Merge pull request 'fix(data): fire transaction synchronizations, and scope them to their transaction' (#9) from fix/tx-synchronizations into master

Reviewed-on: #9

.gitea/maven-settings.xml

@@ -0,0 +1,24 @@
+<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
+          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0 http://maven.apache.org/xsd/settings-1.0.0.xsd">
+    <!--
+      Used only by .gitea/workflows/publish-maven.yml (mvn -s .gitea/maven-settings.xml deploy).
+      Not used for local builds. PACKAGES_TOKEN is a real personal access token (write:package
+      scope) on the Relism account, read from the env var the workflow exports — never written
+      to disk. Deliberately not Gitea's own per-job GITEA_TOKEN: that token can't publish to
+      any package registry at all, a known unimplemented limitation
+      (https://github.com/go-gitea/gitea/issues/23642) — confirmed here by testing: it
+      authenticated fine against the plain API but still got 401 from this endpoint.
+
+      Basic auth (username/password): the <httpHeaders> form Gitea's own docs show for this is
+      honored by Maven's resolver (used for reading <repositories>) but not reliably by the
+      wagon-http provider maven-deploy-plugin actually uploads through.
+    -->
+    <servers>
+        <server>
+            <id>gitea</id>
+            <username>Relism</username>
+            <password>${env.PACKAGES_TOKEN}</password>
+        </server>
+    </servers>
+</settings>

.gitea/workflows/publish-maven.yml

@@ -0,0 +1,49 @@
+name: Publish Maven packages
+
+# Flash's own POM keeps `2.1.0-SNAPSHOT` as its committed version — that's what local
+# `mvn install` (Pathway's normal dev loop, see its pom.xml `flash.version` comment) always
+# produces, and changing it here would break that. Gitea's Maven registry, unlike a real
+# snapshot repository, refuses to re-publish an existing name+version (must delete first —
+# see https://docs.gitea.com/usage/packages/maven#publish-a-package), so every push instead
+# publishes under a throwaway version stamped with the commit it built from
+# (`2.1.0-<short-sha>`), via `versions:set` on a checkout copy — never touching the committed
+# POMs. Consumers (Pathway's `docker` Maven profile) pin `flash.version` to one specific
+# published build and bump it by hand to pick up newer Flash changes; see
+# pathway/pom.xml's `docker` profile for the other half of this.
+on:
+  push:
+    branches: [master]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    # No actions/checkout here on purpose: it's a Node-based action, and this container
+    # (chosen for its preinstalled mvn/JDK 21) has no Node — checkout would fail with
+    # "node: executable file not found". A plain git clone needs neither.
+    container:
+      image: maven:3.9-eclipse-temurin-21
+    steps:
+      - name: Checkout
+        run: |
+          apt-get update && apt-get install -y --no-install-recommends git
+          git clone https://git.pixel-services.com/Relism/Flash5.git .
+          git checkout ${{ gitea.sha }}
+
+      - name: Stamp every module with a commit-scoped version
+        run: |
+          SHORT_SHA=$(git rev-parse --short HEAD)
+          mvn -B versions:set -DnewVersion="2.1.0-${SHORT_SHA}" -DprocessAllModules=true -DgenerateBackupPoms=false
+          echo "Publishing as 2.1.0-${SHORT_SHA}"
+
+      - name: Deploy to the Gitea Maven registry
+        env:
+          # Not GITEA_TOKEN: Gitea's own job token can't publish to package registries at
+          # all (a known, still-unimplemented limitation — see
+          # https://github.com/go-gitea/gitea/issues/23642). Confirmed by testing: GITEA_TOKEN
+          # authenticated fine against the plain API but still got 401 from this endpoint no
+          # matter the auth style. PACKAGES_TOKEN is a real PAT with write:package scope.
+          PACKAGES_TOKEN: ${{ secrets.PACKAGES_TOKEN }}
+        run: |
+          mvn -B -s .gitea/maven-settings.xml -DskipTests deploy \
+            -DaltReleaseDeploymentRepository=gitea::https://git.pixel-services.com/api/packages/Relism/maven \
+            -DaltSnapshotDeploymentRepository=gitea::https://git.pixel-services.com/api/packages/Relism/maven

.github/settings.xml

@@ -0,0 +1,17 @@
+<settings xmlns="http://maven.apache.org/SETTINGS/1.0.0"
+          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+          xsi:schemaLocation="http://maven.apache.org/SETTINGS/1.0.0
+          http://maven.apache.org/xsd/settings-1.0.0.xsd">
+    <servers>
+        <server>
+            <id>Personal</id>
+            <username>${env.MAVEN_USERNAME}</username>
+            <password>${env.MAVEN_PASSWORD}</password>
+        </server>
+        <server>
+            <id>Personal-snapshots</id>
+            <username>${env.MAVEN_USERNAME}</username>
+            <password>${env.MAVEN_PASSWORD}</password>
+        </server>
+    </servers>
+</settings>

.github/workflows/ci.yml

@@ -0,0 +1,47 @@
+name: CI
+
+on:
+  push:
+    branches:
+      - master
+      - 'feature/**'
+      - 'fix/**'
+      - 'hotfix/**'
+    tags-ignore:
+      - 'v*'
+  pull_request:
+    branches:
+      - master
+
+jobs:
+  build:
+    name: Build & Test
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Temurin 21
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: maven
+          server-id: Personal
+          server-username: MAVEN_USERNAME
+          server-password: MAVEN_PASSWORD
+
+      - name: Build and test
+        run: mvn -B --settings .github/settings.xml clean verify
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+
+      - name: Publish test results
+        uses: actions/upload-artifact@v4
+        if: always()
+        with:
+          name: test-results
+          path: '**/target/surefire-reports/*.xml'
+          retention-days: 7

.github/workflows/docs.yml

@@ -0,0 +1,348 @@
+name: Publish Docs
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Docs version to publish (e.g. 2.1.0)'
+        required: true
+        type: string
+
+  workflow_call:
+    inputs:
+      version:
+        description: 'Docs version to publish (e.g. 2.1.0)'
+        required: true
+        type: string
+    secrets:
+      MAVEN_USERNAME:
+        required: true
+      MAVEN_PASSWORD:
+        required: true
+
+jobs:
+  docs:
+    name: Build JavaDoc & Update gh-pages
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Set up Temurin 21
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: maven
+
+      - name: Build project (compile + resolve deps, skip tests)
+        run: mvn -B --settings .github/settings.xml clean verify -DskipTests
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+
+      # javadoc:aggregate runs on the reactor root.
+      # With flash + flash-extensions both declared as modules in root pom.xml,
+      # this produces a single aggregated Javadoc covering all modules.
+      # Default output path: target/site/apidocs/ (no custom reportOutputDirectory set).
+      - name: Generate aggregated JavaDoc
+        run: |
+          mvn -B \
+            --settings .github/settings.xml \
+            -DskipTests \
+            org.apache.maven.plugins:maven-javadoc-plugin:3.6.3:aggregate
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+          
+      - name: Verify JavaDoc output exists
+        run: |
+          APIDOCS=""
+
+          if [ -f "target/site/apidocs/index.html" ]; then
+            APIDOCS="target/site/apidocs"
+          elif [ -f "target/reports/apidocs/index.html" ]; then
+            APIDOCS="target/reports/apidocs"
+          else
+            echo "ERROR: JavaDoc output not found."
+            echo
+            echo "Contents of target/:"
+            find target -maxdepth 5 2>/dev/null || echo "(empty)"
+            exit 1
+          fi
+
+          echo "APIDOCS_DIR=$APIDOCS" >> $GITHUB_ENV
+
+          COUNT=$(find "$APIDOCS" -name '*.html' | wc -l)
+          echo "JavaDoc OK — $COUNT HTML files at $APIDOCS"
+
+      - name: Checkout gh-pages
+        uses: actions/checkout@v4
+        with:
+          ref: gh-pages
+          path: gh-pages-out
+          token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Copy JavaDoc to versioned folder and latest
+        run: |
+          VERSION=${{ inputs.version }}
+
+          mkdir -p gh-pages-out/javadoc/$VERSION
+          cp -r "$APIDOCS_DIR"/. gh-pages-out/javadoc/$VERSION/
+
+          rm -rf gh-pages-out/latest
+          mkdir -p gh-pages-out/latest
+          cp -r "$APIDOCS_DIR"/. gh-pages-out/latest/
+
+      - name: Regenerate index.html
+        run: |
+          cd gh-pages-out
+          python3 - <<'EOF'
+          import os, re
+
+          def version_key(v):
+              parts = re.findall(r'\d+', v)
+              return [int(p) for p in parts] if parts else [0]
+
+          versions = sorted(
+              [d for d in os.listdir("javadoc") if os.path.isdir(f"javadoc/{d}")],
+              key=version_key,
+              reverse=True
+          )
+
+          latest = versions[0] if versions else None
+
+          rows = "\n".join(
+              f'''
+              <div class="release">
+                <div class="release-info">
+                  <span class="version">{v}</span>
+                  {"<span class='badge'>latest</span>" if v == latest else ""}
+                </div>
+
+                <a href="javadoc/{v}/index.html">Open</a>
+              </div>
+              '''
+              for v in versions
+          )
+
+          html = """<!DOCTYPE html>
+          <html lang="en">
+          <head>
+            <meta charset="UTF-8" />
+            <meta name="viewport" content="width=device-width, initial-scale=1.0" />
+            <title>Flash — JavaDoc</title>
+
+            <style>
+              :root {
+                --bg: #ffffff;
+                --surface: #fafafa;
+                --border: #e5e7eb;
+
+                --text: #111827;
+                --muted: #6b7280;
+
+                --accent: #111827;
+                --accent-hover: #000000;
+              }
+
+              * {
+                box-sizing: border-box;
+                margin: 0;
+                padding: 0;
+              }
+
+              body {
+                font-family:
+                  Inter,
+                  ui-sans-serif,
+                  system-ui,
+                  -apple-system,
+                  BlinkMacSystemFont,
+                  "Segoe UI",
+                  sans-serif;
+
+                background: var(--bg);
+                color: var(--text);
+
+                min-height: 100vh;
+                padding: 64px 24px;
+              }
+
+              .container {
+                width: 100%;
+                max-width: 760px;
+                margin: 0 auto;
+              }
+
+              .header {
+                margin-bottom: 40px;
+              }
+
+              .header h1 {
+                font-size: 2rem;
+                font-weight: 600;
+                letter-spacing: -0.04em;
+              }
+
+              .header p {
+                margin-top: 10px;
+
+                color: var(--muted);
+                font-size: 0.95rem;
+                line-height: 1.6;
+              }
+
+              .latest {
+                display: inline-flex;
+                align-items: center;
+
+                margin-top: 20px;
+                padding-bottom: 2px;
+
+                color: var(--accent);
+                text-decoration: none;
+                font-size: 0.95rem;
+                font-weight: 500;
+
+                border-bottom: 1px solid transparent;
+
+                transition:
+                  border-color 0.15s ease,
+                  color 0.15s ease;
+              }
+
+              .latest:hover {
+                border-color: var(--accent);
+                color: var(--accent-hover);
+              }
+
+              .list {
+                border-top: 1px solid var(--border);
+              }
+
+              .release {
+                display: flex;
+                align-items: center;
+                justify-content: space-between;
+
+                gap: 16px;
+
+                padding: 18px 0;
+
+                border-bottom: 1px solid var(--border);
+              }
+
+              .release-info {
+                display: flex;
+                align-items: center;
+                gap: 12px;
+              }
+
+              .version {
+                font-size: 0.96rem;
+                font-weight: 500;
+                letter-spacing: -0.01em;
+              }
+
+              .badge {
+                font-size: 0.72rem;
+                font-weight: 600;
+
+                color: var(--muted);
+
+                border: 1px solid var(--border);
+                padding: 2px 8px;
+              }
+
+              .release a {
+                color: var(--accent);
+                text-decoration: none;
+                font-size: 0.92rem;
+              }
+
+              .release a:hover {
+                text-decoration: underline;
+              }
+
+              .empty {
+                padding: 32px 0;
+
+                color: var(--muted);
+                font-size: 0.95rem;
+              }
+
+              @media (max-width: 640px) {
+                body {
+                  padding: 40px 20px;
+                }
+
+                .header h1 {
+                  font-size: 1.7rem;
+                }
+
+                .release {
+                  flex-direction: column;
+                  align-items: flex-start;
+                }
+              }
+            </style>
+          </head>
+
+          <body>
+            <div class="container">
+
+              <header class="header">
+                <h1>Flash JavaDoc</h1>
+
+                <p>
+                  API documentation for all published Flash releases.
+                </p>
+
+                """ + (
+                  f'''
+                  <a class="latest" href="latest/index.html">
+                    Latest release — {latest}
+                  </a>
+                  '''
+                  if latest else ""
+                ) + """
+              </header>
+
+              """ + (
+                f'''
+                <div class="list">
+                  {rows}
+                </div>
+                '''
+                if rows else
+                '''
+                <div class="empty">
+                  No versions published yet.
+                </div>
+                '''
+              ) + """
+
+            </div>
+          </body>
+          </html>"""
+
+          with open("index.html", "w", encoding="utf-8") as f:
+              f.write(html)
+
+          print(f"index.html generated — {len(versions)} version(s): {versions}")
+          EOF
+
+      - name: Push gh-pages
+        run: |
+          cd gh-pages-out
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+          git add -A
+          git diff --cached --quiet || git commit -m "docs(javadoc): publish ${{ inputs.version }}"
+          git push origin gh-pages

.github/workflows/prepare-release.yml

@@ -0,0 +1,69 @@
+name: Prepare Release
+
+on:
+  workflow_dispatch:
+    inputs:
+      version:
+        description: 'Release version (e.g. 2.0.0)'
+        required: true
+        type: string
+      next_version:
+        description: 'Next development version without -SNAPSHOT (e.g. 2.1.0)'
+        required: true
+        type: string
+
+jobs:
+  prepare:
+    name: Bump, Tag & Push
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}
+          fetch-depth: 0
+
+      - name: Set up Temurin 21
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: maven
+
+      - name: Configure Git
+        run: |
+          git config user.name "github-actions[bot]"
+          git config user.email "github-actions[bot]@users.noreply.github.com"
+
+      - name: Set release version
+        run: mvn -B --settings .github/settings.xml versions:set -DnewVersion=${{ inputs.version }}
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+
+      - name: Commit release version
+        run: |
+          git add -A
+          git commit -m "chore(release): ${{ inputs.version }}"
+
+      - name: Tag release
+        run: git tag v${{ inputs.version }}
+
+      - name: Set next snapshot version
+        run: mvn -B --settings .github/settings.xml versions:set -DnewVersion=${{ inputs.next_version }}-SNAPSHOT
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+
+      - name: Commit next snapshot version
+        run: |
+          git add -A
+          git commit -m "chore(release): prepare ${{ inputs.next_version }}-SNAPSHOT"
+
+      - name: Push commits and tag
+        run: |
+          git push origin master
+          git push origin v${{ inputs.version }}

.github/workflows/release.yml

@@ -0,0 +1,70 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+jobs:
+  # ── 1. Build, GPG-sign, deploy to Maven releases ──────────────────────────
+  release:
+    name: Build, Sign & Deploy
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+
+    outputs:
+      version: ${{ steps.version.outputs.VERSION }}
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Extract version from tag
+        id: version
+        run: echo "VERSION=${GITHUB_REF_NAME#v}" >> $GITHUB_OUTPUT
+
+      - name: Set up Temurin 21
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: maven
+
+      - name: Import GPG key
+        run: |
+          echo "${{ secrets.GPG_PRIVATE_KEY }}" | gpg --batch --import
+          GPG_KEY_ID=$(gpg --list-secret-keys --with-colons | grep '^sec' | cut -d: -f5 | head -1)
+          echo "GPG_KEY_ID=$GPG_KEY_ID" >> $GITHUB_ENV
+
+      - name: Build, sign and deploy to releases
+        run: |
+          mvn -B --settings .github/settings.xml \
+            -DperformRelease=true \
+            -Dgpg.keyname=$GPG_KEY_ID \
+            clean deploy
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}
+
+      - name: Create GitHub Release
+        uses: softprops/action-gh-release@v2
+        with:
+          tag_name: ${{ github.ref_name }}
+          name: ${{ github.ref_name }}
+          generate_release_notes: true
+          draft: false
+          prerelease: false
+
+  # ── 2. Publish JavaDoc (single source of truth: docs.yml) ─────────────────
+  docs:
+    name: Publish JavaDoc
+    needs: release
+    uses: ./.github/workflows/docs.yml
+    with:
+      version: ${{ needs.release.outputs.version }}
+    secrets:
+      MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+      MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}

.github/workflows/snapshot.yml

@@ -0,0 +1,30 @@
+name: Publish Snapshot
+
+on:
+  push:
+    branches:
+      - master
+    tags-ignore:
+      - 'v*'
+
+jobs:
+  snapshot:
+    name: Deploy Snapshot
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Set up Temurin 21
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: 21
+          cache: maven
+
+      - name: Deploy snapshot
+        run: mvn -B --settings .github/settings.xml clean deploy -DskipTests
+        env:
+          MAVEN_USERNAME: ${{ secrets.MAVEN_USERNAME }}
+          MAVEN_PASSWORD: ${{ secrets.MAVEN_PASSWORD }}

.gitignore

@@ -0,0 +1,57 @@
+target/
+*.versionsBackup
+.mvn/timing.properties
+*.class
+!.mvn/wrapper/maven-wrapper.jar
+!**/src/main/**/target/
+!**/src/test/**/target/
+.kotlin
+
+### IntelliJ IDEA ###
+.idea/modules.xml
+.idea/jarRepositories.xml
+.idea/compiler.xml
+.idea/libraries/
+.idea/workspace.xml
+.idea/inspectionProfiles/
+*.iws
+*.iml
+*.ipr
+
+### Eclipse ###
+.apt_generated
+.classpath
+.factorypath
+.project
+.settings
+.springBeans
+.sts4-cache
+
+### NetBeans ###
+/nbproject/private/
+/nbbuild/
+/dist/
+/nbdist/
+/.nb-gradle/
+build/
+!**/src/main/**/build/
+!**/src/test/**/build/
+
+### VS Code ###
+.vscode/
+
+### Mac OS ###
+.DS_Store
+
+CLAUDE.md
+.claude/
+
+### Local / scratch ###
+flash/src/main/java/dev/relism/Main.java
+flash-bench/
+nuxt-shadcn-dashboard/
+/dev/
+/docs/
+jmh-result.text
+*.text
+/flash-extensions/flash-ext-routeviewer/routeviewer-ui/node_modules/

.idea/copilot.data.migration.agent.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AgentMigrationStateService">
+    <option name="migrationStatus" value="COMPLETED" />
+  </component>
+</project>

.idea/copilot.data.migration.ask.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="AskMigrationStateService">
+    <option name="migrationStatus" value="COMPLETED" />
+  </component>
+</project>

.idea/copilot.data.migration.ask2agent.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Ask2AgentMigrationStateService">
+    <option name="migrationStatus" value="COMPLETED" />
+  </component>
+</project>

.idea/copilot.data.migration.edit.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="EditMigrationStateService">
+    <option name="migrationStatus" value="COMPLETED" />
+  </component>
+</project>

.idea/encodings.xml

@@ -0,0 +1,43 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="Encoding">
+    <file url="file://$PROJECT_DIR$/flash-bench/src/main/java" charset="UTF-8" />
+    <file url="file://$PROJECT_DIR$/flash-bench/src/main/resources" charset="UTF-8" />
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+      <option name="project" value="LOCAL" />
+      <updated>1773536678416</updated>
+    </task>
+    <task id="LOCAL-00003" summary="refactored, pre-buffer reuse">
+      <option name="closed" value="true" />
+      <created>1773581516834</created>
+      <option name="number" value="00003" />
+      <option name="presentableId" value="LOCAL-00003" />
+      <option name="project" value="LOCAL" />
+      <updated>1773581516834</updated>
+    </task>
+    <task id="LOCAL-00004" summary="optimized dynamic body size impl, decluttering javadocs/comments">
+      <option name="closed" value="true" />
+      <created>1773591259108</created>
+      <option name="number" value="00004" />
+      <option name="presentableId" value="LOCAL-00004" />
+      <option name="project" value="LOCAL" />
+      <updated>1773591259108</updated>
+    </task>
+    <task id="LOCAL-00005" summary="enhanced HTTP server configuration and response handling; added acceptorThreads, improved header management, and refined error page titles">
+      <option name="closed" value="true" />
+      <created>1773920675327</created>
+      <option name="number" value="00005" />
+      <option name="presentableId" value="LOCAL-00005" />
+      <option name="project" value="LOCAL" />
+      <updated>1773920675327</updated>
+    </task>
+    <task id="LOCAL-00006" summary="multipart parsing, request body access, and chunked input stream support">
+      <option name="closed" value="true" />
+      <created>1773920735659</created>
+      <option name="number" value="00006" />
+      <option name="presentableId" value="LOCAL-00006" />
+      <option name="project" value="LOCAL" />
+      <updated>1773920735659</updated>
+    </task>
+    <task id="LOCAL-00007" summary="enhanced router middleware support; added pre-fused middleware handling and improved handler registration">
+      <option name="closed" value="true" />
+      <created>1773952556190</created>
+      <option name="number" value="00007" />
+      <option name="presentableId" value="LOCAL-00007" />
+      <option name="project" value="LOCAL" />
+      <updated>1773952556190</updated>
+    </task>
+    <task id="LOCAL-00008" summary="pre-major refactoring + ext api.">
+      <option name="closed" value="true" />
+      <created>1774530802482</created>
+      <option name="number" value="00008" />
+      <option name="presentableId" value="LOCAL-00008" />
+      <option name="project" value="LOCAL" />
+      <updated>1774530802482</updated>
+    </task>
+    <task id="LOCAL-00009" summary="preparing for a conceptual refactoring...">
+      <option name="closed" value="true" />
+      <created>1774703474044</created>
+      <option name="number" value="00009" />
+      <option name="presentableId" value="LOCAL-00009" />
+      <option name="project" value="LOCAL" />
+      <updated>1774703474044</updated>
+    </task>
+    <task id="LOCAL-00010" summary="preparing for another refactoring...">
+      <option name="closed" value="true" />
+      <created>1774819003821</created>
+      <option name="number" value="00010" />
+      <option name="presentableId" value="LOCAL-00010" />
+      <option name="project" value="LOCAL" />
+      <updated>1774819003821</updated>
+    </task>
+    <task id="LOCAL-00011" summary="implement OpenAPI contributor integration for rate limiting and response headers">
+      <option name="closed" value="true" />
+      <created>1776634972916</created>
+      <option name="number" value="00011" />
+      <option name="presentableId" value="LOCAL-00011" />
+      <option name="project" value="LOCAL" />
+      <updated>1776634972916</updated>
+    </task>
+    <task id="LOCAL-00012" summary="add core view extension with JTE and Thymeleaf support">
+      <option name="closed" value="true" />
+      <created>1776724331443</created>
+      <option name="number" value="00012" />
+      <option name="presentableId" value="LOCAL-00012" />
+      <option name="project" value="LOCAL" />
+      <updated>1776724331443</updated>
+    </task>
+    <task id="LOCAL-00013" summary="refactor: rename packages and files to use 'flash' prefix for consistency">
+      <option name="closed" value="true" />
+      <created>1777199691803</created>
+      <option name="number" value="00013" />
+      <option name="presentableId" value="LOCAL-00013" />
+      <option name="project" value="LOCAL" />
+      <updated>1777199691804</updated>
+    </task>
+    <task id="LOCAL-00014" summary="fix: enhance global key validation and update template parameters">
+      <option name="closed" value="true" />
+      <created>1777451475753</created>
+      <option name="number" value="00014" />
+      <option name="presentableId" value="LOCAL-00014" />
+      <option name="project" value="LOCAL" />
+      <updated>1777451475753</updated>
+    </task>
+    <task id="LOCAL-00015" summary="feat: introduce WebSocket support with new endpoints and transaction propagation enhancements">
+      <option name="closed" value="true" />
+      <created>1778508899541</created>
+      <option name="number" value="00015" />
+      <option name="presentableId" value="LOCAL-00015" />
+      <option name="project" value="LOCAL" />
+      <updated>1778508899541</updated>
+    </task>
+    <option name="localTasksCounter" value="16" />
+    <servers />
+  </component>
+  <component name="TypeScriptGeneratedFilesManager">
+    <option name="version" value="3" />
+  </component>
+  <component name="Vcs.Log.Tabs.Properties">
+    <option name="TAB_STATES">
+      <map>
+        <entry key="MAIN">
+          <value>
+            <State>
+              <option name="FILTERS">
+                <map>
+                  <entry key="branch">
+                    <value>
+                      <list>
+                        <option value="claude/distracted-spence" />
+                      </list>
+                    </value>
+                  </entry>
+                </map>
+              </option>
+            </State>
+          </value>
+        </entry>
+      </map>
+    </option>
+  </component>
+  <component name="VcsManagerConfiguration">
+    <MESSAGE value="Initial" />
+    <MESSAGE value="pre-module refactor" />
+    <MESSAGE value="refactored, pre-buffer reuse" />
+    <MESSAGE value="optimized dynamic body size impl, decluttering javadocs/comments" />
+    <MESSAGE value="enhanced HTTP server configuration and response handling; added acceptorThreads, improved header management, and refined error page titles" />
+    <MESSAGE value="multipart parsing, request body access, and chunked input stream support" />
+    <MESSAGE value="enhanced router middleware support; added pre-fused middleware handling and improved handler registration" />
+    <MESSAGE value="pre-major refactoring + ext api." />
+    <MESSAGE value="preparing for a conceptual refactoring..." />
+    <MESSAGE value="preparing for another refactoring..." />
+    <MESSAGE value="implement OpenAPI contributor integration for rate limiting and response headers" />
+    <MESSAGE value="add core view extension with JTE and Thymeleaf support" />
+    <MESSAGE value="refactor: rename packages and files to use 'flash' prefix for consistency" />
+    <MESSAGE value="fix: enhance global key validation and update template parameters" />
+    <MESSAGE value="chore(release): prepare 2.1.0-SNAPSHOT" />
+    <MESSAGE value="feat: introduce Spec and Query interfaces with transaction propagation enhancements" />
+    <MESSAGE value="feat: introduce WebSocket support with new endpoints and transaction propagation enhancements" />
+    <option name="LAST_COMMIT_MESSAGE" value="feat: introduce WebSocket support with new endpoints and transaction propagation enhancements" />
+  </component>
+  <component name="XSLT-Support.FileAssociations.UIState">
+    <expand />
+    <select />
+  </component>
+  <component name="github-copilot-workspace">
+    <instructionFileLocations>
+      <option value=".github/instructions" />
+    </instructionFileLocations>
+    <promptFileLocations>
+      <option value=".github/prompts" />
+    </promptFileLocations>
+  </component>
+</project>

AGENTS.md

@@ -0,0 +1,118 @@
+# Flash — Agent Guidelines
+
+This document defines the conventions and rules that all agents (AI or human) must follow
+when working on this repository. Read it entirely before making any change.
+
+---
+
+## Git Workflow
+
+### Branch Naming
+
+| Type | Pattern | Example |
+|------|---------|---------|
+| New feature | `feature/<scope>/<short-description>` | `feature/ext-oidc/pkce-support` |
+| Bug fix | `fix/<scope>/<short-description>` | `fix/core/router-npe` |
+| Hotfix on released version | `hotfix/<version>/<short-description>` | `hotfix/2.0.1/auth-bypass` |
+| CI/infra changes | `feature/ci/<short-description>` | `feature/ci/add-snapshot-workflow` |
+
+Rules:
+- Always branch from `master`.
+- Branch names are lowercase, words separated by `-`.
+- Never push directly to `master`.
+- Never create `develop`, `release/*`, or any other long-lived branch.
+
+### Commit Messages — Conventional Commits
+
+Format: `<type>(<scope>): <short description>`
+
+| Type | When to use |
+|------|-------------|
+| `feat` | New feature |
+| `fix` | Bug fix |
+| `refactor` | Code change without feature/fix |
+| `test` | Adding or updating tests |
+| `docs` | Documentation only |
+| `chore` | Build, deps, tooling — no production code |
+| `ci` | Changes to GitHub Actions workflows |
+
+Allowed scopes: `core`, `ext-jackson`, `ext-openapi`, `ext-oidc`, `ext-routeviewer`,
+`ext-view-core`, `ext-view-jte`, `ext-view-thymeleaf`, `ext-limiter`, `ext-web-bundler`,
+`ext-mcp`, `ext-data-core`, `ext-data-jdbc`, `ext-data-hibernate`, `release`, `deps`, `ci`.
+
+Examples:
+```
+feat(ext-oidc): add PKCE support
+fix(core): fix NPE in RouteHandler when path is null
+chore(deps): upgrade jackson to 2.18.0
+ci: add timeout to snapshot workflow
+chore(release): 2.1.0
+```
+
+### Pull Requests
+
+- Every branch must be merged via PR, never with a direct push.
+- PR title must follow Conventional Commits format.
+- CI (`ci.yml`) must be green before merging.
+- Squash merge is preferred for `feature/*` and `fix/*` to keep history clean.
+- Merge commit is preferred for hotfixes (preserves the fix commit intact).
+
+---
+
+## Versioning
+
+- All modules share a single version defined in the root `pom.xml` (`flash-parent`).
+- Never change the version in child POMs — always and only in the parent.
+- Current scheme: `MAJOR.MINOR.PATCH`
+  - MAJOR: breaking API changes
+  - MINOR: new backward-compatible features
+  - PATCH: backward-compatible bug fixes on an already-released version
+- During development, master always carries a `-SNAPSHOT` version.
+- **Never manually edit the version** — versions are bumped exclusively by the
+  `prepare-release` GitHub Actions workflow.
+
+### Release Process (for maintainers only)
+
+1. Ensure `master` is green (CI passing).
+2. Go to GitHub Actions → `Prepare Release` → `Run workflow`.
+3. Input `version` (e.g. `2.1.0`) and `next_version` (e.g. `2.2.0`).
+4. The workflow handles everything: bump, commit, tag, push.
+5. The `release` workflow then triggers automatically on the tag.
+
+---
+
+## Maven & Module Structure
+
+- Root POM: `flash-parent` — defines all dependency versions and plugin config.
+- `flash` module: the core framework JAR.
+- `flash-extensions` POM: aggregator for all extension modules.
+- Extensions live under `flash-extensions/flash-ext-*/`.
+- When adding a new extension:
+  1. Add the module to `flash-extensions/pom.xml` `<modules>`.
+  2. Add the dependency to `flash-extensions/pom.xml` `<dependencyManagement>`.
+  3. Add the dependency to the root `pom.xml` `<dependencyManagement>`.
+  4. Do **not** declare a `<version>` in the new module's POM — it inherits from the parent.
+
+---
+
+## CI/CD Pipelines
+
+| Workflow | Trigger | What it does |
+|----------|---------|--------------|
+| `ci.yml` | Push to any branch, PR to master | Compile + test — required gate |
+| `snapshot.yml` | Push to `master` | Deploy `-SNAPSHOT` to `maven.relism.dev/snapshots` |
+| `prepare-release.yml` | Manual `workflow_dispatch` | Bump version, commit, tag, push |
+| `release.yml` | Push of tag `v*` | GPG sign, deploy to `/releases`, JavaDoc to GitHub Pages, GitHub Release |
+
+**Agents must never manually trigger `prepare-release` or modify version strings.**
+
+---
+
+## What Agents Must NOT Do
+
+- Push directly to `master` or `gh-pages`.
+- Manually edit `<version>` tags in any POM.
+- Add new `<repositories>` or `<distributionManagement>` entries without explicit instruction.
+- Modify `.github/workflows/*.yml` files without explicit instruction.
+- Commit generated files (`target/`, `*.class`, `*.versionsBackup`).
+- Use `git push --force` on any branch.

CNAME

@@ -1 +0,0 @@
-flash.javadocs.relism.dev

README.md

@@ -0,0 +1,289 @@
+# Flash
+
+A high-performance HTTP/1.1 server library for Java 21, built around virtual threads and a zero-allocation FSM router.
+
+## Modules
+
+| Module | Description |
+|---|---|
+| `flash` | Core server library — router, request parser, HTTP I/O transport |
+| `flash-extensions/flash-ext-jackson` | Jackson JSON integration |
+| `flash-extensions/flash-ext-openapi` | OpenAPI 3.0 spec + Swagger UI |
+| `flash-extensions/flash-ext-oidc` | OIDC Authorization Code + PKCE flow |
+| `flash-extensions/flash-ext-mcp` | MCP (Model Context Protocol) server — Streamable HTTP, optional OAuth2 via flash-ext-oidc |
+| `flash-extensions/flash-ext-view-core` | Minimal shared SSR runtime primitives |
+| `flash-extensions/flash-ext-view-jte` | Opinionated jte SSR extension |
+| `flash-extensions/flash-ext-view-thymeleaf` | Opinionated Thymeleaf SSR extension |
+| `flash-bench` | Demo harness (OIDC + OpenAPI + Jackson) |
+
+## Requirements
+
+- Java 21+
+- Maven 3.8+
+
+## Quick start
+
+```java
+FlashApp.create(8080)
+    .get("/ping", (req, res) -> "pong")
+    .start();
+```
+
+With full configuration:
+
+```java
+FlashApp.create(
+    FlashConfiguration.builder()
+        .port(8080)
+        .host("0.0.0.0")
+        .maxHeaderBufferSize(65536)
+        .build()
+)
+.get("/ping", (req, res) -> "pong")
+.start();
+```
+
+## Route registration
+
+### Lambda routes
+
+```java
+FlashApp app = FlashApp.create(8080);
+
+app.get("/hello", (req, res) -> "world");
+
+app.post("/echo", (req, res) -> {
+    byte[] body = req.body().bytes();
+    return res.status(200).body(body);
+});
+
+app.get("/users/{id}", (req, res) -> {
+    String id = req.pathParam("id");
+    return "user:" + id;
+});
+```
+
+### Class-based handlers
+
+Extend `RequestHandler`, annotate it, then scan its package. Dependencies are cached in
+`onInit()` after Flash has resolved its complete boot-time service graph:
+
+```java
+@GET("/api/users")
+public class ListUsers extends RequestHandler {
+    private UserService users;
+
+    @Override protected void onInit() { users = require(UserService.class); }
+    @Override public Object handle(Request req, Response res) { return users.list(); }
+}
+
+app.scan("dev.example.api");
+```
+
+### Middleware
+
+Apply middleware at registration. Flash composes the final chain at boot:
+
+```java
+Middleware authCheck = next -> (req, res) -> {
+    if (req.header("Authorization") == null)
+        return res.status(401).body("Unauthorized");
+    return next.handle(req, res);
+};
+
+app.get("/secure", (req, res) -> "secret data", authCheck);
+```
+
+Multiple middlewares are composed outermost-first (left-to-right in the call):
+
+```java
+app.get("/admin", handler, logging, auth, rateLimit);
+// execution order: logging → auth → rateLimit → handler
+```
+
+### Classpath scan
+
+Scans a package for classes that extend `RequestHandler` and carry `@Route`. Each is
+instantiated via its public no-arg constructor:
+
+```java
+app.scan("dev.example.handlers");
+```
+
+### Namespace mounting
+
+Mount a scoped sub-router under a prefix. All routes registered inside the scope get the
+prefix prepended automatically. The scope inherits the parent's extension context (annotation
+processors, services):
+
+```java
+app.mount("/api", scope -> {
+    scope.get("/health", (req, res) -> "ok");          // → GET /api/health
+    scope.scan("dev.example.api");
+});
+```
+
+## Extensions
+
+Extensions have one declarative `configure` method. They declare services, processors and route
+callbacks; Flash resolves the complete graph, materialises routes, compiles both routers, then
+opens listeners. Extension install order never makes a service “not ready”.
+
+```java
+FlashApp.create(8080)
+    .install(new JacksonExtension())
+    .install(new OpenApiExtension("/openapi", "My API", "1.0.0"))
+    .install(new OidcExtension(oidcConfig))
+    .scan("dev.example.handlers")
+    .start();
+```
+
+See extension-specific READMEs for full details:
+- [`flash-ext-jackson`](flash-extensions/flash-ext-jackson/README.md)
+- [`flash-ext-openapi`](flash-extensions/flash-ext-openapi/README.md)
+- [`flash-ext-oidc`](flash-extensions/flash-ext-oidc/README.md)
+- [`flash-ext-mcp`](flash-extensions/flash-ext-mcp/docs/README.md)
+- [`flash-ext-view-jte`](flash-extensions/flash-ext-view-jte/README.md)
+- [`flash-ext-view-thymeleaf`](flash-extensions/flash-ext-view-thymeleaf/README.md)
+
+## Error handlers
+
+```java
+app.onNotFound((req, res) -> res.status(404).body("Not found: " + req.path()));
+
+app.onException((ex, req, res) -> {
+    if (ex instanceof IllegalArgumentException)
+        return res.status(400).body(ex.getMessage());
+    return res.status(500).body("Internal error");
+});
+```
+
+## FlashConfiguration
+
+| Field | Default | Description |
+|---|---|---|
+| `port` | — | TCP port to bind |
+| `host` | `"0.0.0.0"` | Bind address |
+| `tls` | `null` | TLS for the default listener — see [TLS](#tls) |
+| `listeners` | `[]` | Multiple bind targets (port + host + optional TLS) on one app — see [TLS](#tls) |
+| `maxHeaderBufferSize` | `65536` | Max size of the header buffer (bytes) |
+
+## TLS
+
+HTTPS and WSS are a transport-layer concern only: once a listener is bound, the accepted
+`Socket` is either plain or an `SSLSocket` indistinguishably from `HttpServer`'s point of view
+onward — the request parser, router, and WebSocket upgrade never branch on it. WSS is therefore
+not a separate feature; it's a WebSocket upgrade running over whatever transport it was handed.
+
+### Quick start
+
+```java
+FlashApp.create(FlashConfiguration.builder()
+        .port(443)
+        .tls(TlsConfig.keystore(Path.of("cert.p12"), "changeit"))
+        .build())
+    .get("/ping", (req, res) -> "pong")   // HTTPS
+    .ws("/live", handler)                 // WSS, same route API
+    .start();
+```
+
+### Multiple listeners
+
+One app can bind any number of ports, each independently plain or TLS:
+
+```java
+FlashApp.create(FlashConfiguration.builder()
+        .listener(new FlashConfiguration.Listener(80))                                   // plain
+        .listener(new FlashConfiguration.Listener(443, TlsConfig.keystore(cert, pass)))  // TLS
+        .build());
+```
+
+A non-empty `listeners` list takes precedence over the top-level `port`/`host`/`tls` fields.
+Each listener gets its own accept threads; the router, WS router, and virtual-thread executor
+are shared by all of them — one app, N ports.
+
+### `TlsConfig`
+
+| Factory | Use |
+|---|---|
+| `TlsConfig.keystore(Path, String)` | Builds the `SSLContext` from a PKCS12/JKS keystore (type guessed from the extension). Pins `TLSv1.2`/`TLSv1.3` as enabled protocols; cipher suites are left at the JDK's own curated default. |
+| `TlsConfig.ofContext(SSLContext)` | Escape hatch — the given `SSLContext` is used exactly as built. Flash never calls `setSSLParameters` on this path beyond what you explicitly request via `clientAuth`/`applicationProtocols`, so anything else you configured (custom `KeyManager`, ALPN, cipher suites) is authoritative. |
+
+Chainable on either factory:
+
+```java
+TlsConfig.keystore(cert, pass)
+    .clientAuth(ClientAuth.REQUIRE)                    // mTLS: NONE (default) | OPTIONAL | REQUIRE
+    .applicationProtocols("acme-tls/1", "http/1.1")    // ALPN, in preference order
+```
+
+**SNI** falls out of `keystore()` for free: a keystore holding more than one certificate entry
+is matched against the requested hostname by each certificate's SAN (falling back to CN) — no
+per-hostname config. The first entry in the keystore is the default when SNI is absent or
+matches nothing (same convention as nginx/HAProxy's `default_server`).
+
+**ALPN and custom certificate selection** (e.g. TLS-ALPN-01 / RFC 8737 for on-demand ACME
+issuance): ALPN is resolved while consuming `ClientHello`/producing `ServerHello`, which always
+precedes `Certificate` production. A custom `X509ExtendedKeyManager` passed via `ofContext`
+can therefore read `engine.getHandshakeApplicationProtocol()` (or
+`((SSLSocket) socket).getHandshakeApplicationProtocol()`) inside
+`chooseEngineServerAlias`/`chooseServerAlias` — the negotiated protocol is already resolved by
+then, so the certificate decision can key off it.
+
+**mTLS with a private CA**: `clientAuth(...)` only requests/requires a client certificate;
+`keystore()` deliberately doesn't expose a way to configure which CAs are trusted for that
+certificate (it uses the JDK default trust store). For a private CA, build the `SSLContext`
+yourself with a `TrustManagerFactory` and use `ofContext(...)`.
+
+### Reading TLS info from a request
+
+```java
+app.get("/whoami", (req, res) -> {
+    if (!req.isSecure()) return "plain";
+    SSLSession session = req.sslSession();          // null iff !isSecure()
+    X509Certificate peer = (X509Certificate) session.getPeerCertificates()[0]; // mTLS only
+    return session.getCipherSuite() + " / " + session.getProtocol();
+});
+```
+
+`Request.isSecure()` / `Request.sslSession()` cost nothing extra per request: the `SSLSocket`
+reference is threaded through once per connection (same mechanism as `remoteAddress()`), and
+`sslSession()` only calls `SSLSocket#getSession()` — a cached-field read once the handshake
+that got the request this far has already completed, never a forced handshake.
+
+`WebSocketSession` mirrors this exactly (`isSecure()`, `sslSession()`) by delegating to the
+upgrading `Request` — no separate TLS state is tracked for WS.
+
+## Architecture
+
+```
+ServerSocket.accept()
+  → RequestParser.parse()       # zero-alloc header parsing, buffer reuse across keep-alive
+  → GlobalRouter.route()        # two-tier: mounted sub-routers (longest prefix) then FastPathRouterImpl
+  → RequestHandler.handle()     # user handler; return value sets body
+  → Request.drain()             # consume unread body for keep-alive
+  → HttpServer writes response  # status line, headers, then fixed or chunked body
+  → loop or close socket        # based on Connection header
+```
+
+- **Virtual threads** — each accepted socket runs on a virtual thread (`Executors.newVirtualThreadPerTaskExecutor()`). Java 21 required.
+- **Zero-allocation router** — `FastPathRouterImpl` uses `fpr-core`, a byte-level FSM that matches on `METHOD + path` bytes with no per-request allocation.
+- **Keep-alive** — `RequestParser` reuses its header buffer across requests on the same connection.
+- **Chunked transfer** — both chunked request bodies (decoded via `ChunkedInputStream`) and chunked response bodies are supported.
+- **TLS is transport-only** — see [TLS](#tls). Listeners bind either a plain `ServerSocket` or an `SSLServerSocket`; nothing downstream of `accept()` branches on which.
+
+## Build & test
+
+```bash
+# Build all modules (skip tests)
+mvn clean package -DskipTests
+
+# Run all tests
+mvn test
+
+# Run a single test class
+mvn test -pl flash -Dtest=RequestParserTest
+
+# Run the benchmark demo server
+java -jar flash-bench/target/flash-bench-1.0-SNAPSHOT.jar
+```

benchmarks/websocket/benchmark.yml

@@ -0,0 +1,24 @@
+config:
+  target: "ws://localhost:8080/echo"
+  engines:
+    ws: {}
+  phases:
+    - duration: 30
+      arrivalRate: 50
+      rampTo: 500
+      name: "Riscaldamento progressivo"
+    - duration: 120
+      arrivalRate: 1000  # 1000 nuovi utenti al secondo
+      name: "Carico Estremo"
+  ensure:
+    maxErrorRate: 5
+    p99: 150
+
+scenarios:
+  - name: "Saturazione Totale"
+    engine: ws
+    flow:
+      - loop:
+          - send: "Benchmark data"
+          # Rimosso il 'think' per eliminare il limite artificiale di 10msg/s per utente
+        count: 100 # Ogni utente spara a raffica 100 messaggi senza pause

flash-extensions/flash-ext-data-core/docs/README.md

@@ -0,0 +1,125 @@
+# flash-ext-data-core
+
+Shared core for Flash's data layer.
+
+## Purpose
+
+This module defines the transactional contract shared across backend implementations. It does not
+talk to Hibernate or JDBC directly: it exposes abstractions and a minimal runtime, nothing else.
+
+## Components
+
+- `TxDefinition`: immutable transaction metadata.
+- `TxStatus`: runtime state returned by the manager.
+- `TxManager`: the `begin`/`commit`/`rollback` contract.
+- `Tx`: runtime orchestration and the per-thread transaction stack.
+- `ResourceRegistry`: thread-local storage for resources and synchronizations.
+- `Repository<T, ID>`: self-transactional base repository.
+- `Spec<T>`: composable predicate.
+- `Query<T>`: query object carrying spec, sort and paging.
+- `SpecBuilder<T>`: fluent DSL for building typed specs.
+- `RepositorySupport<T, ID>`: shared internal helper.
+- `TransactionPropagation`: propagation semantics.
+- `TransactionIsolation`: isolation level.
+- `TxSynchronization`: lifecycle hooks (see below).
+
+## Execution model
+
+The flow is:
+
+1. `Tx.call(definition, work)` calls `TxManager.begin(definition)`.
+2. The `TxManager` creates a backend-specific `TxStatus`.
+3. The status is pushed onto the thread-local stack.
+4. The work uses `Tx.resource(Class)` to obtain the current resource.
+5. When the work ends, `Tx` chooses between `commit` and `rollback`.
+6. The stack is popped, and the thread-local is cleared once it is empty.
+
+## Supported propagation
+
+- `REQUIRED`: use the active transaction, or open a new one.
+- `REQUIRES_NEW`: suspend the current transaction and open a new one.
+- `SUPPORTS`: join the active transaction if there is one, otherwise run without a transaction.
+- `NOT_SUPPORTED`: suspend the current transaction and run without one.
+- `MANDATORY`: require an active transaction.
+
+## Synchronizations (`TxSynchronization`)
+
+Lifecycle hooks for **one** transaction, registered through `Data.afterCommit(...)` (or directly
+with `ResourceRegistry.addSynchronization(...)`).
+
+Every callback belongs to exactly the innermost transaction active at registration time, and fires
+exactly once, when *that* transaction completes:
+
+- a **joined** inner transaction (`REQUIRED`) is not a transaction of its own, so callbacks
+  registered inside one wait for the outermost commit;
+- a `REQUIRES_NEW` transaction is, so completing it fires only its own callbacks and leaves the
+  suspended outer transaction's pending.
+
+### Which side of the commit each hook sits on
+
+| hook | when | resource |
+| --- | --- | --- |
+| `beforeCommit(readOnly)` | immediately **before** the real commit | session/connection still **bound**, transaction still active |
+| `afterCommit()` / `afterRollback()` | after completion | resource already **unbound** |
+| `afterCompletion(outcome)` | after the two above | resource already unbound |
+
+`beforeCommit` is the only hook that can still write through the same resource and have the write
+land in the same atomic unit: flush a buffer, stamp an audit row, materialize a derived value. It
+is skipped when the transaction is already `rollback-only`, since there is no commit to precede.
+
+Post-completion callbacks run with the resource unbound instead: one that opens its own transaction
+gets a **fresh** one rather than joining the transaction that just finished. That is what makes
+them the right place to refresh a cache, enqueue a message, or notify anything outside the
+database.
+
+### Failure
+
+Throwing from `beforeCommit` **vetoes the commit**: the transaction is rolled back,
+`afterRollback`/`afterCompletion(ROLLED_BACK)` fire, and the exception reaches the caller. That is
+the reason the hook runs before the commit rather than after — it can still refuse.
+
+The post-completion hooks have no such power: the transaction is already over by the time they run,
+so an exception propagates but changes nothing already committed, and stops the callbacks queued
+behind it.
+
+## Using `Repository`
+
+`Repository` is the shared base for concrete repositories. Every public operation internally uses a
+`REQUIRED` transaction, read-only where applicable.
+
+Subclasses implement the `doXxx(...)` methods:
+
+- `doFind(Query<T>)`
+- `doFindOne(Spec<T>)`
+- `doFindPage(Query<T>)`
+- `doDeleteAll(Spec<T>)`
+- `doUpdateAll(Spec<T>, T)`
+
+The old `findAll(...)` and `findPage(...)` overloads were reduced to a combination of `Query<T>` and
+`Spec<T>`.
+
+```java
+public abstract class Repository<T, ID> {
+    protected Repository(Tx tx) { ... }
+    protected final <R> R tx(Tx.TxCallable<R> work) { ... }
+}
+```
+
+## Composing with Flash
+
+`DataExtension` registers:
+
+- `Tx` in the `FlashContext`
+- `TxManager` in the `FlashContext`
+- an annotation processor for `@Transactional`
+
+This makes the data layer composable with Flash's extension system without global state.
+
+## Implementation notes
+
+- The transaction stack is thread-local and is cleared once it becomes empty.
+- Backend resources are suspended and restored for `REQUIRES_NEW` and `NOT_SUPPORTED`.
+- `TxSynchronization` is the hook point for commit/rollback/completion callbacks.
+- Synchronizations live in a thread-local list; every new transaction records how many were already
+  registered when it opened and fires only its own tail, so a `REQUIRES_NEW` does not drag along
+  the suspended transaction's callbacks.

flash-extensions/flash-ext-data-core/pom.xml

@@ -0,0 +1,84 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-data-core</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.transaction</groupId>
+            <artifactId>jakarta.transaction-api</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.annotation</groupId>
+            <artifactId>jakarta.annotation-api</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>jakarta.validation</groupId>
+            <artifactId>jakarta.validation-api</artifactId>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <maven.compiler.source>21</maven.compiler.source>
+        <maven.compiler.target>21</maven.compiler.target>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
+        <jacoco.version>0.8.12</jacoco.version>
+    </properties>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
+                <version>${jacoco.version}</version>
+                <executions>
+                    <execution>
+                        <id>jacoco-initialize</id>
+                        <goals>
+                            <goal>prepare-agent</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>jacoco-site</id>
+                        <phase>verify</phase>
+                        <goals>
+                            <goal>report</goal>
+                        </goals>
+                        <configuration>
+                            <rules>
+                                <rule>
+                                    <element>BUNDLE</element>
+                                    <limits>
+                                        <limit>
+                                            <counter>LINE</counter>
+                                            <value>COVEREDRATIO</value>
+                                            <minimum>0.80</minimum>
+                                        </limit>
+                                    </limits>
+                                </rule>
+                            </rules>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+            <plugin>
+                <groupId>org.apache.maven.plugins</groupId>
+                <artifactId>maven-surefire-plugin</artifactId>
+                <version>3.2.5</version>
+            </plugin>
+        </plugins>
+    </build>
+</project>

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/DataExtension.java

@@ -0,0 +1,63 @@
+package dev.relism.flash.ext.data;
+
+import dev.relism.flash.ext.data.core.Tx;
+import dev.relism.flash.ext.data.core.Data;
+import dev.relism.flash.ext.data.core.TxDefinition;
+import dev.relism.flash.ext.data.core.TxManager;
+import dev.relism.flash.ext.data.core.TransactionPropagation;
+import dev.relism.flash.extension.FlashRegistrar;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.extension.FlashExtension;
+import dev.relism.flash.routing.MiddlewareKey;
+import dev.relism.flash.routing.MiddlewareNode;
+import dev.relism.flash.routing.Middleware;
+import jakarta.transaction.Transactional;
+
+import java.util.List;
+import java.util.Objects;
+
+public final class DataExtension implements FlashExtension {
+    private static final MiddlewareKey TRANSACTION = MiddlewareKey.of("flash.data.transaction");
+    private final TxManager txManager;
+    private final Tx tx;
+    private final Data data;
+
+    public DataExtension(TxManager txManager) {
+        this(txManager, null);
+    }
+
+    public DataExtension(TxManager txManager, Data data) {
+        this.txManager = Objects.requireNonNull(txManager);
+        this.data = data;
+        this.tx = data != null ? data.tx() : new Tx(txManager);
+    }
+
+    @Override
+    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
+        ctx.provide(Tx.class, tx);
+        ctx.provide(TxManager.class, txManager);
+        if (data != null) ctx.provide(Data.class, data);
+        ctx.addAnnotationProcessor(handlerClass -> {
+            Transactional ann = handlerClass.getAnnotation(Transactional.class);
+            if (ann == null) {
+                return List.of();
+            }
+            TxDefinition definition = TxDefinition.DEFAULTS
+                    .withPropagation(mapTxType(ann.value()));
+            Middleware middleware = next -> (req, res) -> {
+                return tx.call(definition, () -> next.handle(req, res));
+            };
+            return List.of(MiddlewareNode.of(TRANSACTION, middleware));
+        });
+    }
+
+    private TransactionPropagation mapTxType(Transactional.TxType txType) {
+        return switch (txType) {
+            case REQUIRED -> TransactionPropagation.REQUIRED;
+            case REQUIRES_NEW -> TransactionPropagation.REQUIRES_NEW;
+            case SUPPORTS -> TransactionPropagation.SUPPORTS;
+            case MANDATORY -> TransactionPropagation.MANDATORY;
+            case NOT_SUPPORTED, NEVER -> TransactionPropagation.NOT_SUPPORTED;
+        };
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Data.java

@@ -0,0 +1,46 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.Objects;
+import java.io.Serializable;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Application-facing data gateway. Repositories are created once per entity type and are safe to
+ * share: transaction/session state stays in {@link Tx}, never in the repository instance.
+ */
+public final class Data {
+    private final Tx tx;
+    private final RepositoryFactory repositories;
+    private final ConcurrentHashMap<Class<?>, Repository<?, ?>> cache = new ConcurrentHashMap<>();
+
+    public Data(Tx tx, RepositoryFactory repositories) {
+        this.tx = Objects.requireNonNull(tx, "tx");
+        this.repositories = Objects.requireNonNull(repositories, "repositories");
+    }
+
+    public Tx tx() { return tx; }
+
+    @SuppressWarnings("unchecked")
+    public <T, ID extends Serializable> Repository<T, ID> repository(Class<T> type) {
+        Objects.requireNonNull(type, "type");
+        return (Repository<T, ID>) cache.computeIfAbsent(type, key -> repositories.create(tx, type));
+    }
+
+    public void read(Tx.TxRunnable work) { tx.run(tx.readOnly(), work); }
+    public <T> T read(Tx.TxCallable<T> work) { return tx.call(tx.readOnly(), work); }
+    public void write(Tx.TxRunnable work) { tx.run(work); }
+    public <T> T write(Tx.TxCallable<T> work) { return tx.call(work); }
+    /** Transitional low-level access for infrastructure that needs an explicit definition. */
+    public void run(Tx.TxRunnable work) { tx.run(work); }
+    public <T> T call(Tx.TxCallable<T> work) { return tx.call(work); }
+    public <T> T call(TxDefinition definition, Tx.TxCallable<T> work) { return tx.call(definition, work); }
+    public TxDefinition readOnly() { return tx.readOnly(); }
+
+    /** Registers work that runs only after the enclosing write transaction commits. */
+    public void afterCommit(Runnable work) {
+        if (!tx.isActive()) throw new IllegalStateException("afterCommit requires an active transaction");
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override public void afterCommit() { work.run(); }
+        });
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Page.java

@@ -0,0 +1,15 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.List;
+
+public record Page<T>(
+        List<T> content,
+        int     page,
+        int     size,
+        long    total
+) {
+    public int  totalPages()   { return size == 0 ? 0 : (int) Math.ceil((double) total / size); }
+    public boolean hasNext()   { return page + 1 < totalPages(); }
+    public boolean hasPrev()   { return page > 0; }
+    public boolean isEmpty()   { return content.isEmpty(); }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Query.java

@@ -0,0 +1,28 @@
+package dev.relism.flash.ext.data.core;
+
+public record Query<T>(Spec<T> spec, Sort sort, Integer page, Integer size) {
+    public Query {
+        spec = spec == null ? Spec.all() : spec;
+        sort = sort == null ? Sort.unsorted() : sort;
+    }
+
+    public static <T> Query<T> all() {
+        return new Query<>(Spec.all(), Sort.unsorted(), null, null);
+    }
+
+    public Query<T> where(Spec<T> spec) {
+        return new Query<>(spec, sort, page, size);
+    }
+
+    public Query<T> orderBy(Sort sort) {
+        return new Query<>(spec, sort, page, size);
+    }
+
+    public Query<T> page(int page, int size) {
+        return new Query<>(spec, sort, page, size);
+    }
+
+    public boolean isPaged() {
+        return page != null && size != null;
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Repository.java

@@ -0,0 +1,121 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public abstract class Repository<T, ID> extends RepositorySupport<T, ID> {
+
+    protected Repository(Tx tx) {
+        super(tx);
+    }
+
+    public Optional<T> findById(ID id) {
+        return roQuery(() -> doFindById(id));
+    }
+
+    public boolean existsById(ID id) {
+        return roQuery(() -> doExistsById(id));
+    }
+
+    public long count() {
+        return roQuery(this::doCount);
+    }
+
+    public List<T> findAll() {
+        return findAll(Query.all());
+    }
+
+    public List<T> findAll(Spec<T> spec) {
+        return findAll(Query.<T>all().where(spec));
+    }
+
+    public List<T> findAll(Query<T> query) {
+        return roQuery(() -> doFind(query));
+    }
+
+    public Page<T> findPage(Query<T> query) {
+        return roQuery(() -> doFindPage(query));
+    }
+
+    public Optional<T> findOne(Spec<T> spec) {
+        return roQuery(() -> doFindOne(spec));
+    }
+
+    public T save(T entity) {
+        return rwQuery(() -> doSave(entity));
+    }
+
+    public T update(T entity) {
+        return rwQuery(() -> doUpdate(entity));
+    }
+
+    public List<T> saveAll(Iterable<T> entities) {
+        return rwQuery(() -> doSaveAll(entities));
+    }
+
+    public void delete(T entity) {
+        rwQuery(() -> {
+            doDelete(entity);
+            return null;
+        });
+    }
+
+    public void deleteById(ID id) {
+        rwQuery(() -> {
+            doDeleteById(id);
+            return null;
+        });
+    }
+
+    public int deleteAll(Spec<T> spec) {
+        return rwQuery(() -> doDeleteAll(spec));
+    }
+
+    public int updateAll(Spec<T> spec, T patch) {
+        return rwQuery(() -> doUpdateAll(spec, patch));
+    }
+
+    public List<T> findAll(int page, int size) {
+        return findAll(Query.<T>all().page(page, size));
+    }
+
+    public List<T> findAll(Sort sort) {
+        return findAll(Query.<T>all().orderBy(sort));
+    }
+
+    public List<T> findAll(int page, int size, Sort sort) {
+        return findAll(Query.<T>all().orderBy(sort).page(page, size));
+    }
+
+    public Page<T> findPage(int page, int size) {
+        return findPage(Query.<T>all().page(page, size));
+    }
+
+    public Page<T> findPage(int page, int size, Sort sort) {
+        return findPage(Query.<T>all().orderBy(sort).page(page, size));
+    }
+
+    public void deleteAll(Iterable<T> entities) {
+        rwQuery(() -> {
+            for (T entity : entities) {
+                doDelete(entity);
+            }
+            return null;
+        });
+    }
+
+    protected abstract Optional<T> doFindById(ID id);
+    protected abstract List<T> doFind(Query<T> query);
+    protected abstract Optional<T> doFindOne(Spec<T> spec);
+    protected abstract Page<T> doFindPage(Query<T> query);
+    protected abstract boolean doExistsById(ID id);
+    protected abstract long doCount();
+    protected abstract T doSave(T entity);
+    protected abstract List<T> doSaveAll(Iterable<T> entities);
+    protected abstract T doUpdate(T entity);
+    protected abstract void doDelete(T entity);
+    protected abstract void doDeleteById(ID id);
+    protected abstract int doDeleteAll(Spec<T> spec);
+    protected abstract int doUpdateAll(Spec<T> spec, T patch);
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/RepositoryFactory.java

@@ -0,0 +1,9 @@
+package dev.relism.flash.ext.data.core;
+
+import java.io.Serializable;
+
+/** Creates the backend-specific, stateless repository for one entity type. */
+@FunctionalInterface
+public interface RepositoryFactory {
+    <T, ID extends Serializable> Repository<T, ID> create(Tx tx, Class<T> type);
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/RepositorySupport.java

@@ -0,0 +1,24 @@
+package dev.relism.flash.ext.data.core;
+
+public abstract class RepositorySupport<T, ID> {
+    private final Tx tx;
+    private final TxDefinition rw = TxDefinition.DEFAULTS
+            .withPropagation(TransactionPropagation.REQUIRED);
+    private final TxDefinition ro = rw.asReadOnly();
+
+    protected RepositorySupport(Tx tx) {
+        this.tx = tx;
+    }
+
+    protected final Tx tx() {
+        return tx;
+    }
+
+    protected final <R> R roQuery(Tx.TxCallable<R> work) {
+        return tx.call(ro, work);
+    }
+
+    protected final <R> R rwQuery(Tx.TxCallable<R> work) {
+        return tx.call(rw, work);
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/ResourceRegistry.java

@@ -0,0 +1,111 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import java.util.Objects;
+
+public final class ResourceRegistry {
+    private static final ThreadLocal<Map<TxResourceKey, Object>> RESOURCES =
+            ThreadLocal.withInitial(HashMap::new);
+    private static final ThreadLocal<List<TxSynchronization>> SYNCHRONIZATIONS =
+            ThreadLocal.withInitial(ArrayList::new);
+
+    private ResourceRegistry() {}
+
+    public static void bind(TxResourceKey key, Object value) {
+        RESOURCES.get().put(key, Objects.requireNonNull(value));
+    }
+
+    public static boolean isBound(TxResourceKey key) {
+        return RESOURCES.get().containsKey(key);
+    }
+
+    public static void unbind(TxResourceKey key) {
+        RESOURCES.get().remove(key);
+    }
+
+    public static void clear() {
+        RESOURCES.get().clear();
+        SYNCHRONIZATIONS.get().clear();
+    }
+
+    public static void cleanup() {
+        RESOURCES.remove();
+        SYNCHRONIZATIONS.remove();
+    }
+
+    public static <R> R get(TxResourceKey key, Class<R> type) {
+        Object value = RESOURCES.get().get(key);
+        if (value == null) {
+            throw new IllegalStateException("No resource bound for key: " + key);
+        }
+        return type.cast(value);
+    }
+
+    public static <R> R getOrNull(TxResourceKey key, Class<R> type) {
+        Object value = RESOURCES.get().get(key);
+        return value == null ? null : type.cast(value);
+    }
+
+    public static void addSynchronization(TxSynchronization sync) {
+        SYNCHRONIZATIONS.get().add(Objects.requireNonNull(sync));
+    }
+
+    /**
+     * How many synchronizations are registered right now — captured by a transaction manager when
+     * it opens a new transaction, and handed back to {@link #fireSynchronizations} on completion
+     * so that transaction only fires its own. See there for why that matters.
+     */
+    public static int synchronizationCount() {
+        return SYNCHRONIZATIONS.get().size();
+    }
+
+    /**
+     * Runs {@link TxSynchronization#beforeCommit} on the synchronizations registered from
+     * {@code fromIndex} onward, while their transaction is still active and its resource still
+     * bound. Unlike {@link #fireSynchronizations} this leaves them registered: they still have
+     * their post-completion callbacks to come. Exceptions propagate on purpose — a beforeCommit
+     * that throws vetoes the commit, see {@link TxSynchronization}.
+     *
+     * <p>Snapshots before iterating, so a callback that registers further synchronizations (a
+     * nested {@code Data#afterCommit}) doesn't mutate the list mid-loop. Those new ones join the
+     * transaction's post-completion callbacks without getting a {@code beforeCommit} of their own,
+     * which is the only coherent answer once the pass is already running.
+     */
+    public static void fireBeforeCommit(boolean readOnly, int fromIndex) {
+        List<TxSynchronization> pending = SYNCHRONIZATIONS.get();
+        if (fromIndex >= pending.size()) {
+            return;
+        }
+        for (TxSynchronization sync : List.copyOf(pending.subList(fromIndex, pending.size()))) {
+            sync.beforeCommit(readOnly);
+        }
+    }
+
+    /**
+     * Fires (and removes) the synchronizations registered from {@code fromIndex} onward — the ones
+     * belonging to the transaction now completing. Everything before that index was registered by
+     * an enclosing transaction that is merely <em>suspended</em>, not finished: a REQUIRES_NEW
+     * inner transaction sets its own baseline, so committing it no longer drags the outer's
+     * pending callbacks along — which fired them early, and with the inner transaction's outcome,
+     * for an outer transaction that might still roll back.
+     */
+    public static void fireSynchronizations(TxOutcome outcome, int fromIndex) {
+        List<TxSynchronization> pending = SYNCHRONIZATIONS.get();
+        if (fromIndex >= pending.size()) {
+            return;
+        }
+        List<TxSynchronization> syncs = List.copyOf(pending.subList(fromIndex, pending.size()));
+        pending.subList(fromIndex, pending.size()).clear();
+        for (TxSynchronization sync : syncs) {
+            if (outcome == TxOutcome.COMMITTED) {
+                sync.afterCommit();
+            } else {
+                sync.afterRollback();
+            }
+            sync.afterCompletion(outcome);
+        }
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Sort.java

@@ -0,0 +1,26 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public record Sort(List<Column> columns) {
+
+    public record Column(String column, boolean asc) {}
+
+    public static Sort unsorted() { return new Sort(List.of()); }
+
+    public boolean isSorted() { return !columns.isEmpty(); }
+
+    public static Sort by(String column)          { return new Sort(List.of(new Column(column, true))); }
+    public static Sort desc(String column)        { return new Sort(List.of(new Column(column, false))); }
+    public static Sort by(String col, boolean asc){ return new Sort(List.of(new Column(col, asc))); }
+
+    public Sort then(String column)               { return thenBy(column, true); }
+    public Sort thenDesc(String column)           { return thenBy(column, false); }
+
+    private Sort thenBy(String column, boolean asc) {
+        List<Column> next = new ArrayList<>(columns);
+        next.add(new Column(column, asc));
+        return new Sort(next);
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Spec.java

@@ -0,0 +1,26 @@
+package dev.relism.flash.ext.data.core;
+
+@FunctionalInterface
+public interface Spec<T> {
+    String toFragment(SpecContext ctx);
+
+    default Spec<T> and(Spec<T> other) {
+        return ctx -> "(" + this.toFragment(ctx) + " AND " + other.toFragment(ctx) + ")";
+    }
+
+    default Spec<T> or(Spec<T> other) {
+        return ctx -> "(" + this.toFragment(ctx) + " OR " + other.toFragment(ctx) + ")";
+    }
+
+    default Spec<T> not() {
+        return ctx -> "NOT (" + this.toFragment(ctx) + ")";
+    }
+
+    static <T> Spec<T> all() {
+        return ctx -> "1=1";
+    }
+
+    static <T> Spec<T> none() {
+        return ctx -> "1=0";
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/SpecBuilder.java

@@ -0,0 +1,37 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.Collection;
+import java.util.Objects;
+import java.util.stream.Collectors;
+
+public final class SpecBuilder<T> {
+    private SpecBuilder() {}
+
+    public static <T, V> FieldSpec<T, V> field(String column) {
+        return new FieldSpec<>(column);
+    }
+
+    public static final class FieldSpec<T, V> {
+        private final String column;
+
+        private FieldSpec(String column) {
+            this.column = Objects.requireNonNull(column);
+        }
+
+        public Spec<T> eq(V value) { return ctx -> column + " = " + ctx.bind(value); }
+        public Spec<T> neq(V value) { return ctx -> column + " != " + ctx.bind(value); }
+        public Spec<T> like(String pattern) { return ctx -> column + " like " + ctx.bind(pattern); }
+        public Spec<T> isNull() { return ctx -> column + " is null"; }
+        public Spec<T> isNotNull() { return ctx -> column + " is not null"; }
+
+        public Spec<T> in(Collection<V> values) {
+            return ctx -> column + " in (" + values.stream().map(ctx::bind).collect(Collectors.joining(", ")) + ")";
+        }
+
+        public <C extends Comparable<C>> Spec<T> gt(C value) { return ctx -> column + " > " + ctx.bind(value); }
+        public <C extends Comparable<C>> Spec<T> lt(C value) { return ctx -> column + " < " + ctx.bind(value); }
+        public <C extends Comparable<C>> Spec<T> between(C lo, C hi) {
+            return ctx -> column + " between " + ctx.bind(lo) + " and " + ctx.bind(hi);
+        }
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/SpecContext.java

@@ -0,0 +1,5 @@
+package dev.relism.flash.ext.data.core;
+
+public interface SpecContext {
+    String bind(Object value);
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TransactionIsolation.java

@@ -0,0 +1,14 @@
+package dev.relism.flash.ext.data.core;
+
+public enum TransactionIsolation {
+    DEFAULT(-1),
+    READ_UNCOMMITTED(1),
+    READ_COMMITTED(2),
+    REPEATABLE_READ(4),
+    SERIALIZABLE(8);
+
+    private final int level;
+
+    TransactionIsolation(int level) { this.level = level; }
+    public int level() { return level; }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TransactionPropagation.java

@@ -0,0 +1,9 @@
+package dev.relism.flash.ext.data.core;
+
+public enum TransactionPropagation {
+    REQUIRED,
+    REQUIRES_NEW,
+    SUPPORTS,
+    NOT_SUPPORTED,
+    MANDATORY
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/Tx.java

@@ -0,0 +1,116 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.ArrayDeque;
+import java.util.Deque;
+import java.util.Objects;
+
+public final class Tx {
+    private static final ThreadLocal<Deque<TxStatus>> STATUS_STACK =
+            ThreadLocal.withInitial(ArrayDeque::new);
+    private final TxManager manager;
+
+    public Tx(TxManager txManager) {
+        this.manager = Objects.requireNonNull(txManager);
+    }
+
+    public void run(TxRunnable work) {
+        run(TxDefinition.DEFAULTS, work);
+    }
+
+    public void run(TxDefinition definition, TxRunnable work) {
+        call(definition, () -> {
+            work.run();
+            return null;
+        });
+    }
+
+    public <T> T call(TxCallable<T> work) {
+        return call(TxDefinition.DEFAULTS, work);
+    }
+
+    public <T> T call(TxDefinition definition, TxCallable<T> work) {
+        TxStatus status = manager.begin(definition);
+        pushStatus(status);
+        try {
+            T result = work.call();
+            if (status.isRollbackOnly()) {
+                manager.rollback(status);
+            } else {
+                manager.commit(status);
+            }
+            return result;
+        } catch (Exception e) {
+            silentRollback(status);
+            throw (e instanceof TxException txException) ? txException : new TxException(e);
+        } catch (Throwable t) {
+            silentRollback(status);
+            throw sneakyThrow(t);
+        } finally {
+            popStatus();
+            if (STATUS_STACK.get().isEmpty()) {
+                STATUS_STACK.remove();
+            }
+        }
+    }
+
+    public boolean isActive() {
+        return !STATUS_STACK.get().isEmpty();
+    }
+
+    public void setRollbackOnly() {
+        currentStatus().markRollbackOnly();
+    }
+
+    public <R> R resource(Class<R> type) {
+        return currentStatus().resource(type);
+    }
+
+    public TxDefinition requiresNew() {
+        return TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW);
+    }
+
+    public TxDefinition readOnly() {
+        return TxDefinition.DEFAULTS.asReadOnly();
+    }
+
+    private TxStatus currentStatus() {
+        TxStatus status = STATUS_STACK.get().peek();
+        if (status == null) {
+            throw new IllegalStateException("No active transaction");
+        }
+        return status;
+    }
+
+    private void pushStatus(TxStatus status) {
+        STATUS_STACK.get().push(status);
+    }
+
+    private void popStatus() {
+        Deque<TxStatus> stack = STATUS_STACK.get();
+        if (!stack.isEmpty()) {
+            stack.pop();
+        }
+    }
+
+    private void silentRollback(TxStatus status) {
+        try {
+            manager.rollback(status);
+        } catch (Exception ignored) {
+        }
+    }
+
+    @SuppressWarnings("unchecked")
+    private static <E extends Throwable> RuntimeException sneakyThrow(Throwable t) throws E {
+        throw (E) t;
+    }
+
+    @FunctionalInterface
+    public interface TxRunnable {
+        void run();
+    }
+
+    @FunctionalInterface
+    public interface TxCallable<T> {
+        T call() throws Exception;
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxDefinition.java

@@ -0,0 +1,31 @@
+package dev.relism.flash.ext.data.core;
+
+public record TxDefinition(
+        TransactionPropagation propagation,
+        TransactionIsolation    isolation,
+        boolean                 readOnly,
+        String                  label
+) {
+    public static final TxDefinition DEFAULTS = new TxDefinition(
+            TransactionPropagation.REQUIRED,
+            TransactionIsolation.DEFAULT,
+            false,
+            null
+    );
+
+    public TxDefinition withPropagation(TransactionPropagation p) {
+        return new TxDefinition(p, isolation, readOnly, label);
+    }
+
+    public TxDefinition withIsolation(TransactionIsolation i) {
+        return new TxDefinition(propagation, i, readOnly, label);
+    }
+
+    public TxDefinition withReadOnly(boolean ro) {
+        return new TxDefinition(propagation, isolation, ro, label);
+    }
+
+    public TxDefinition asReadOnly() {
+        return new TxDefinition(propagation, isolation, true, label);
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxException.java

@@ -0,0 +1,6 @@
+package dev.relism.flash.ext.data.core;
+
+public class TxException extends RuntimeException {
+    public TxException(String message) { super(message); }
+    public TxException(Throwable cause) { super(cause); }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxManager.java

@@ -0,0 +1,7 @@
+package dev.relism.flash.ext.data.core;
+
+public interface TxManager {
+    TxStatus begin(TxDefinition definition);
+    void commit(TxStatus status);
+    void rollback(TxStatus status);
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxOutcome.java

@@ -0,0 +1,6 @@
+package dev.relism.flash.ext.data.core;
+
+public enum TxOutcome {
+    COMMITTED,
+    ROLLED_BACK
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxResourceKey.java

@@ -0,0 +1,32 @@
+package dev.relism.flash.ext.data.core;
+
+import java.util.Objects;
+
+public final class TxResourceKey {
+    private final String name;
+
+    private TxResourceKey(String name) {
+        this.name = Objects.requireNonNull(name);
+    }
+
+    public static TxResourceKey of(String name) {
+        return new TxResourceKey(name);
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) return true;
+        if (!(o instanceof TxResourceKey that)) return false;
+        return name.equals(that.name);
+    }
+
+    @Override
+    public int hashCode() {
+        return name.hashCode();
+    }
+
+    @Override
+    public String toString() {
+        return name;
+    }
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxStatus.java

@@ -0,0 +1,9 @@
+package dev.relism.flash.ext.data.core;
+
+public interface TxStatus {
+    boolean isNewTransaction();
+    boolean isReadOnly();
+    boolean isRollbackOnly();
+    void markRollbackOnly();
+    <R> R resource(Class<R> type);
+}

flash-extensions/flash-ext-data-core/src/main/java/dev/relism/flash/ext/data/core/TxSynchronization.java

@@ -0,0 +1,58 @@
+package dev.relism.flash.ext.data.core;
+
+/**
+ * Lifecycle hooks for one transaction, registered through {@code Data#afterCommit} (or
+ * {@link ResourceRegistry#addSynchronization} directly) and fired by the {@link TxManager} that
+ * owns the transaction they were registered in.
+ *
+ * <p>Every callback belongs to exactly one transaction — the innermost one active at registration
+ * time — and fires exactly once, when <em>that</em> transaction completes. A joined
+ * ({@code REQUIRED}) inner transaction is not a transaction of its own, so callbacks registered
+ * inside one wait for the outermost commit; a {@code REQUIRES_NEW} transaction is, so completing
+ * it fires only its own callbacks and leaves the suspended outer transaction's alone.
+ *
+ * <h3>Where each hook sits relative to the commit</h3>
+ * <ul>
+ *   <li>{@link #beforeCommit(boolean)} — immediately <b>before</b> the real commit, with the
+ *       transaction still active and its session/connection still bound. This is the only hook
+ *       that can still write through that same resource and have the write land in the same atomic
+ *       unit: flush a buffer, stamp an audit row, materialize a derived value. Skipped entirely
+ *       when the transaction is already rollback-only, since there is no commit to precede.</li>
+ *   <li>{@link #afterCommit()} / {@link #afterRollback()}, then {@link #afterCompletion(TxOutcome)}
+ *       — <b>after</b> the transaction has completed and its resource has been unbound. Nothing
+ *       done here is part of the transaction: a callback that opens its own transaction gets a
+ *       fresh one instead of joining the one that just finished, which is what makes this the
+ *       right place to refresh a cache, enqueue a message, or notify anything outside the
+ *       database.</li>
+ * </ul>
+ *
+ * <h3>Failure</h3>
+ * Throwing from {@link #beforeCommit(boolean)} <b>vetoes the commit</b>: the transaction is rolled
+ * back, {@link #afterRollback()}/{@link #afterCompletion(TxOutcome)} fire with
+ * {@link TxOutcome#ROLLED_BACK}, and the exception propagates to the caller. That is the point of
+ * this hook running before the commit rather than after — it can still refuse.
+ *
+ * <p>The post-completion hooks have no such power: the transaction is over by the time they run,
+ * so an exception from one propagates to the caller but changes nothing already committed, and
+ * stops the callbacks queued behind it.
+ */
+public interface TxSynchronization {
+
+    /**
+     * Runs inside the transaction, immediately before it commits — see the interface javadoc.
+     * Throwing from here rolls the transaction back instead of committing it.
+     *
+     * @param readOnly whether the transaction was opened read-only, so a callback that would
+     *                 otherwise write can skip work it is not allowed to do
+     */
+    default void beforeCommit(boolean readOnly) {}
+
+    /** Runs after a successful commit, with the transaction's resource already unbound. */
+    default void afterCommit() {}
+
+    /** Runs after a rollback, with the transaction's resource already unbound. */
+    default void afterRollback() {}
+
+    /** Runs after {@link #afterCommit()}/{@link #afterRollback()}, whichever applied. */
+    default void afterCompletion(TxOutcome outcome) {}
+}

flash-extensions/flash-ext-data-hibernate/docs/README.md

@@ -0,0 +1,95 @@
+# flash-ext-data-hibernate
+
+Hibernate backend for `flash-ext-data-core`.
+
+## Purpose
+
+This module implements `TxManager` on top of a `SessionFactory` and provides a Hibernate-centric
+repository base class.
+
+## How to use it
+
+### 1. Create the manager
+
+```java
+SessionFactory sessionFactory = ...;
+HibernateTxManager txManager = new HibernateTxManager(sessionFactory);
+DataExtension extension = new DataExtension(txManager);
+```
+
+### 2. Install the extension in Flash
+
+The extension registers `Tx` and `TxManager` in the `FlashContext`. Class-based handlers annotated
+with `@Transactional` are wrapped automatically.
+
+### 3. Define a repository
+
+```java
+public final class UserRepository extends HibernateRepository<User, Long> {
+    public UserRepository(Tx tx) {
+        super(tx, User.class);
+    }
+}
+```
+
+With the query/spec model you can expose reusable fields as constants:
+
+```java
+public final class UserRepository extends HibernateRepository<User, Long> {
+    public static final SpecBuilder.FieldSpec<User, String> EMAIL = SpecBuilder.field("u.email");
+    public static final SpecBuilder.FieldSpec<User, Boolean> ACTIVE = SpecBuilder.field("u.active");
+
+    public UserRepository(Tx tx) {
+        super(tx, User.class);
+    }
+
+    public Optional<User> findByEmail(String email) {
+        return findOne(EMAIL.eq(email));
+    }
+}
+```
+
+Domain-specific queries can use the base class helpers:
+
+```java
+public List<User> findByEmailDomain(String domain) {
+    return findMany("from User u where u.email like :email", q ->
+        q.setParameter("email", "%@" + domain)
+    );
+}
+```
+
+## How it works underneath
+
+- The current transaction is represented by `HibernateTxStatus`.
+- The resource exposed to the core is a `Session`.
+- `Tx.resource(Session.class)` retrieves the `Session` from the current context.
+- `REQUIRES_NEW` suspends the active status and opens a new `Session`.
+- `NOT_SUPPORTED` suspends the active transaction and continues with no session bound.
+
+## Repository base class
+
+`HibernateRepository` provides:
+
+- `findById`, `findAll`, `findPage`, `findOne`
+- `save`, `update`, `delete`, `saveAll`
+- bulk `deleteAll(Spec<T>)` and `updateAll(Spec<T>, T)`
+- HQL helpers: `hql(...)`, `hqlMutate(...)`
+
+Concrete classes only have to implement domain queries, never the transactional plumbing.
+
+## Transactional semantics
+
+- `REQUIRED`: join, or open a new transaction.
+- `REQUIRES_NEW`: suspend the current context.
+- `SUPPORTS`: join if a transaction exists, otherwise no-op.
+- `NOT_SUPPORTED`: suspend and continue without a transaction.
+- `MANDATORY`: fail if there is no transaction.
+
+## Notes
+
+- The `Session` is closed when a new transaction ends.
+- Synchronizations registered in a transaction fire when *that* transaction completes:
+  `beforeCommit` while it is still active and the `Session` still bound, the post-completion hooks
+  once it is unbound. See `flash-ext-data-core/docs/README.md` for the full contract.
+- This backend is meant to be used through the base class, not directly.

flash-extensions/flash-ext-data-hibernate/pom.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-data-hibernate</artifactId>
+
+    <properties>
+        <jacoco.version>0.8.12</jacoco.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-ext-data-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.hibernate.orm</groupId>
+            <artifactId>hibernate-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
+                <version>${jacoco.version}</version>
+                <configuration>
+                    <rules>
+                        <rule>
+                            <element>BUNDLE</element>
+                            <limits>
+                                <limit>
+                                    <counter>LINE</counter>
+                                    <value>COVEREDRATIO</value>
+                                    <minimum>0.80</minimum>
+                                </limit>
+                            </limits>
+                        </rule>
+                    </rules>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateData.java

@@ -0,0 +1,25 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.Data;
+import dev.relism.flash.ext.data.core.Repository;
+import dev.relism.flash.ext.data.core.RepositoryFactory;
+import dev.relism.flash.ext.data.core.Tx;
+import dev.relism.flash.ext.data.core.TxManager;
+import java.io.Serializable;
+
+/** Hibernate-backed {@link Data} factory. */
+public final class HibernateData {
+    private HibernateData() {}
+
+    private static final RepositoryFactory REPOSITORIES = new RepositoryFactory() {
+        @Override
+        public <T, ID extends Serializable> Repository<T, ID> create(Tx tx, Class<T> type) {
+            return new HibernateRepository<T, ID>(tx, type) {};
+        }
+    };
+
+    public static Data create(TxManager manager) {
+        Tx tx = new Tx(manager);
+        return new Data(tx, REPOSITORIES);
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateRepository.java

@@ -0,0 +1,167 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.*;
+import jakarta.persistence.TypedQuery;
+import org.hibernate.Session;
+import org.hibernate.query.MutationQuery;
+
+import java.io.Serializable;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+import java.util.function.Consumer;
+import java.util.stream.Collectors;
+
+public abstract class HibernateRepository<T, ID extends Serializable> extends Repository<T, ID> {
+
+    private final Class<T> type;
+
+    protected HibernateRepository(Tx tx, Class<T> type) {
+        super(tx);
+        this.type = type;
+    }
+
+    protected Session session() {
+        return tx().resource(Session.class);
+    }
+
+    @Override
+    protected Optional<T> doFindById(ID id) {
+        return Optional.ofNullable(session().get(type, id));
+    }
+
+    @Override
+    protected List<T> doFind(Query<T> query) {
+        HibernateSpecContext ctx = new HibernateSpecContext();
+        String where = query.spec() != null ? " where " + query.spec().toFragment(ctx) : "";
+        String order = query.sort() != null && query.sort().isSorted() ? " order by " + orderClause(query.sort()) : "";
+
+        TypedQuery<T> q = session().createQuery("from " + type.getSimpleName() + where + order, type);
+        ctx.applyParameters(q);
+
+        if (query.isPaged()) {
+            q.setFirstResult(query.page() * query.size());
+            q.setMaxResults(query.size());
+        }
+        return q.getResultList();
+    }
+
+    @Override
+    protected Optional<T> doFindOne(Spec<T> spec) {
+        return doFind(Query.<T>all().where(spec).page(0, 1)).stream().findFirst();
+    }
+
+    @Override
+    protected Page<T> doFindPage(Query<T> query) {
+        if (!query.isPaged()) {
+            throw new IllegalArgumentException("Paged query requires page and size");
+        }
+        long total = countWhere(query.spec());
+        List<T> content = doFind(query);
+        return new Page<>(content, query.page(), query.size(), total);
+    }
+
+    @Override
+    protected boolean doExistsById(ID id) {
+        return doFindById(id).isPresent();
+    }
+
+    @Override
+    protected long doCount() {
+        return countWhere(Spec.all());
+    }
+
+    @Override
+    protected T doSave(T entity) {
+        session().persist(entity);
+        return entity;
+    }
+
+    @Override
+    protected List<T> doSaveAll(Iterable<T> entities) {
+        List<T> saved = new ArrayList<>();
+        Session s = session();
+        int i = 0;
+        for (T entity : entities) {
+            s.persist(entity);
+            saved.add(entity);
+            if (++i % 50 == 0) {
+                s.flush();
+                s.clear();
+            }
+        }
+        return saved;
+    }
+
+    @Override
+    protected T doUpdate(T entity) {
+        return session().merge(entity);
+    }
+
+    @Override
+    protected void doDelete(T entity) {
+        Session s = session();
+        s.remove(s.contains(entity) ? entity : s.merge(entity));
+    }
+
+    @Override
+    protected void doDeleteById(ID id) {
+        doFindById(id).ifPresent(this::doDelete);
+    }
+
+    @Override
+    protected int doDeleteAll(Spec<T> spec) {
+        HibernateSpecContext ctx = new HibernateSpecContext();
+        String where = " where " + spec.toFragment(ctx);
+        MutationQuery q = session().createMutationQuery("delete from " + type.getSimpleName() + where);
+        ctx.applyParameters(q);
+        return q.executeUpdate();
+    }
+
+    @Override
+    protected int doUpdateAll(Spec<T> spec, T patch) {
+        throw new UnsupportedOperationException("Override doUpdateAll() for bulk UPDATE support");
+    }
+
+    protected List<T> hql(String hql, Consumer<TypedQuery<T>> params) {
+        return roQuery(() -> {
+            TypedQuery<T> q = session().createQuery(hql, type);
+            params.accept(q);
+            return q.getResultList();
+        });
+    }
+
+    protected <R> List<R> hql(String hql, Class<R> resultType, Consumer<TypedQuery<R>> params) {
+        return roQuery(() -> {
+            TypedQuery<R> q = session().createQuery(hql, resultType);
+            params.accept(q);
+            return q.getResultList();
+        });
+    }
+
+    protected int hqlMutate(String hql, Consumer<MutationQuery> params) {
+        return rwQuery(() -> {
+            MutationQuery q = session().createMutationQuery(hql);
+            params.accept(q);
+            return q.executeUpdate();
+        });
+    }
+
+    protected Class<T> entityType() {
+        return type;
+    }
+
+    private long countWhere(Spec<T> spec) {
+        HibernateSpecContext ctx = new HibernateSpecContext();
+        String where = spec != null ? " where " + spec.toFragment(ctx) : "";
+        TypedQuery<Long> q = session().createQuery("select count(*) from " + type.getSimpleName() + where, Long.class);
+        ctx.applyParameters(q);
+        return q.getResultStream().findFirst().orElse(0L);
+    }
+
+    private String orderClause(Sort sort) {
+        return sort.columns().stream()
+                .map(c -> c.column() + (c.asc() ? " ASC" : " DESC"))
+                .collect(Collectors.joining(", "));
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateSpecContext.java

@@ -0,0 +1,28 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.SpecContext;
+import jakarta.persistence.TypedQuery;
+import org.hibernate.query.MutationQuery;
+
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+final class HibernateSpecContext implements SpecContext {
+    private final Map<String, Object> params = new LinkedHashMap<>();
+    private int counter;
+
+    @Override
+    public String bind(Object value) {
+        String name = "p" + (++counter);
+        params.put(name, value);
+        return ":" + name;
+    }
+
+    void applyParameters(TypedQuery<?> query) {
+        params.forEach(query::setParameter);
+    }
+
+    void applyParameters(MutationQuery query) {
+        params.forEach(query::setParameter);
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateTxManager.java

@@ -0,0 +1,219 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.*;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+
+import java.util.Objects;
+
+public class HibernateTxManager implements TxManager {
+    private static final TxResourceKey HIBERNATE_STATUS_KEY = TxResourceKey.of("hibernate.tx.status");
+    private static final TxResourceKey HIBERNATE_SUSPENDED_KEY = TxResourceKey.of("hibernate.tx.suspended");
+
+    private final SessionFactory sf;
+
+    public HibernateTxManager(SessionFactory sessionFactory) {
+        this.sf = Objects.requireNonNull(sessionFactory);
+    }
+
+    @Override
+    public TxStatus begin(TxDefinition definition) {
+        return switch (definition.propagation()) {
+            case REQUIRED -> ResourceRegistry.isBound(HIBERNATE_STATUS_KEY)
+                    ? joinExisting(definition)
+                    : beginNew(definition);
+            case REQUIRES_NEW -> beginNew(definition);
+            case SUPPORTS -> ResourceRegistry.isBound(HIBERNATE_STATUS_KEY)
+                    ? joinExisting(definition)
+                    : noOp(definition);
+            case MANDATORY -> {
+                if (!ResourceRegistry.isBound(HIBERNATE_STATUS_KEY))
+                    throw new IllegalStateException("MANDATORY: no active transaction");
+                yield joinExisting(definition);
+            }
+            case NOT_SUPPORTED -> {
+                HibernateTxStatus suspended = suspendIfNeeded();
+                yield noOp(definition, suspended);
+            }
+        };
+    }
+
+    private TxStatus beginNew(TxDefinition definition) {
+        return beginNew(definition, suspendIfNeeded());
+    }
+
+    private TxStatus beginNew(TxDefinition definition, HibernateTxStatus suspended) {
+        // Anything already registered belongs to an enclosing transaction this one is nested
+        // inside (or suspended over) — see ResourceRegistry#fireSynchronizations.
+        int synchronizationBaseline = ResourceRegistry.synchronizationCount();
+        Session s = sf.openSession();
+        boolean bound = false;
+        try {
+            s.beginTransaction();
+            if (definition.readOnly()) s.setDefaultReadOnly(true);
+            if (definition.isolation() != TransactionIsolation.DEFAULT) {
+                s.doWork(connection -> connection.setTransactionIsolation(definition.isolation().level()));
+            }
+            HibernateTxStatus status = new HibernateTxStatus(
+                    s,
+                    true,
+                    definition.readOnly(),
+                    suspended,
+                    new HibernateTxStatus.RollbackMarker(),
+                    synchronizationBaseline
+            );
+            ResourceRegistry.bind(HIBERNATE_STATUS_KEY, status);
+            bound = true;
+            return status;
+        } catch (RuntimeException e) {
+            silentClose(s);
+            throw e;
+        } catch (Exception e) {
+            silentClose(s);
+            throw new TxException(e);
+        } finally {
+            if (!bound && suspended != null) {
+                ResourceRegistry.unbind(HIBERNATE_SUSPENDED_KEY);
+                ResourceRegistry.bind(HIBERNATE_STATUS_KEY, suspended);
+            }
+        }
+    }
+
+    private TxStatus joinExisting(TxDefinition definition) {
+        HibernateTxStatus existing = ResourceRegistry.get(HIBERNATE_STATUS_KEY, HibernateTxStatus.class);
+        if (definition.readOnly() && !existing.isReadOnly()) {
+            throw new TxException("Cannot join read-write tx as read-only");
+        }
+        // Baseline 0 is never read: a joined status isn't a new transaction, so commit()/rollback()
+        // hand it straight back to the transaction it joined without firing anything.
+        return new HibernateTxStatus(
+                existing.session(),
+                false,
+                definition.readOnly(),
+                null,
+                existing.rollbackMarker(),
+                0
+        );
+    }
+
+    private TxStatus noOp(TxDefinition definition) {
+        return noOp(definition, null);
+    }
+
+    private TxStatus noOp(TxDefinition definition, HibernateTxStatus suspended) {
+        return new HibernateTxStatus(null, false, definition.readOnly(), suspended, new HibernateTxStatus.RollbackMarker(), 0);
+    }
+
+    private HibernateTxStatus suspendIfNeeded() {
+        HibernateTxStatus suspended = ResourceRegistry.getOrNull(HIBERNATE_STATUS_KEY, HibernateTxStatus.class);
+        if (suspended != null) {
+            ResourceRegistry.unbind(HIBERNATE_STATUS_KEY);
+            ResourceRegistry.bind(HIBERNATE_SUSPENDED_KEY, suspended);
+        }
+        return suspended;
+    }
+
+    @Override
+    public void commit(TxStatus status) {
+        HibernateTxStatus s = (HibernateTxStatus) status;
+        if (!s.isNewTransaction()) {
+            resumeIfNeeded(s);
+            cleanupIfIdle();
+            return;
+        }
+        TxOutcome outcome = null;
+        try {
+            if (s.isRollbackOnly() && s.session().getTransaction().isActive()) {
+                s.session().getTransaction().rollback();
+                outcome = TxOutcome.ROLLED_BACK;
+            } else {
+                // Still inside the transaction, session still bound: a beforeCommit callback can
+                // write through it and land in this same commit. Throwing from there vetoes the
+                // commit — see TxSynchronization.
+                ResourceRegistry.fireBeforeCommit(s.isReadOnly(), s.synchronizationBaseline());
+                s.session().getTransaction().commit();
+                outcome = TxOutcome.COMMITTED;
+            }
+        } catch (RuntimeException e) {
+            // A vetoing beforeCommit, or a commit that failed outright: either way nothing was
+            // committed, so roll back and let the remaining callbacks hear ROLLED_BACK rather than
+            // nothing at all. A rollback failure here is swallowed deliberately — it would mask
+            // the exception that actually explains what went wrong, which is the one propagating.
+            if (s.session().getTransaction().isActive()) {
+                try {
+                    s.session().getTransaction().rollback();
+                } catch (RuntimeException suppressed) {
+                    e.addSuppressed(suppressed);
+                }
+            }
+            outcome = TxOutcome.ROLLED_BACK;
+            throw e;
+        } finally {
+            // Order is load-bearing, and getting it wrong is silent: cleanupIfIdle() calls
+            // ResourceRegistry.cleanup(), which removes the very ThreadLocal list of
+            // synchronizations still waiting to be fired — firing afterwards saw a freshly
+            // initialized empty list and dropped every callback on the floor. cleanupAndResume()
+            // still has to come first, so a synchronization that opens its own transaction
+            // (Registry#reload() in Pathway does) starts a fresh one instead of joining the
+            // session that just committed. rollback() below already had this order right.
+            cleanupAndResume(s);
+            if (outcome != null) ResourceRegistry.fireSynchronizations(outcome, s.synchronizationBaseline());
+            cleanupIfIdle();
+        }
+    }
+
+    @Override
+    public void rollback(TxStatus status) {
+        HibernateTxStatus s = (HibernateTxStatus) status;
+        if (!s.isNewTransaction()) {
+            s.markRollbackOnly();
+            resumeIfNeeded(s);
+            cleanupIfIdle();
+            return;
+        }
+        try {
+            if (s.session().getTransaction().isActive()) {
+                s.session().getTransaction().rollback();
+            }
+        } finally {
+            // Same order as commit(): unbind the session first so a callback opening its own
+            // transaction gets a fresh one, fire before cleanupIfIdle() can drop the list.
+            cleanupAndResume(s);
+            ResourceRegistry.fireSynchronizations(TxOutcome.ROLLED_BACK, s.synchronizationBaseline());
+            cleanupIfIdle();
+        }
+    }
+
+    private void cleanupAndResume(HibernateTxStatus status) {
+        ResourceRegistry.unbind(HIBERNATE_STATUS_KEY);
+        silentClose(status.session());
+        resumeIfNeeded(status);
+    }
+
+    private void cleanupIfIdle() {
+        if (!ResourceRegistry.isBound(HIBERNATE_STATUS_KEY) && !ResourceRegistry.isBound(HIBERNATE_SUSPENDED_KEY)) {
+            ResourceRegistry.cleanup();
+        }
+    }
+
+    private void resumeIfNeeded(HibernateTxStatus status) {
+        HibernateTxStatus suspended = status.suspended();
+        if (suspended == null) {
+            suspended = ResourceRegistry.getOrNull(HIBERNATE_SUSPENDED_KEY, HibernateTxStatus.class);
+        }
+        if (suspended != null) {
+            ResourceRegistry.unbind(HIBERNATE_SUSPENDED_KEY);
+            ResourceRegistry.bind(HIBERNATE_STATUS_KEY, suspended);
+        }
+    }
+
+    private void silentClose(Session session) {
+        if (session == null) {
+            return;
+        }
+        try {
+            session.close();
+        } catch (Exception ignored) {
+        }
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/main/java/dev/relism/flash/ext/data/hibernate/HibernateTxStatus.java

@@ -0,0 +1,53 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.TxStatus;
+import org.hibernate.Session;
+
+class HibernateTxStatus implements TxStatus {
+    static final class RollbackMarker {
+        boolean rollbackOnly;
+    }
+
+    private final Session session;
+    private final boolean newTransaction;
+    private final boolean readOnly;
+    private final HibernateTxStatus suspended;
+    private final RollbackMarker rollbackMarker;
+    private final int synchronizationBaseline;
+
+    HibernateTxStatus(
+            Session session,
+            boolean newTransaction,
+            boolean readOnly,
+            HibernateTxStatus suspended,
+            RollbackMarker rollbackMarker,
+            int synchronizationBaseline
+    ) {
+        this.session = session;
+        this.newTransaction = newTransaction;
+        this.readOnly = readOnly;
+        this.suspended = suspended;
+        this.rollbackMarker = rollbackMarker;
+        this.synchronizationBaseline = synchronizationBaseline;
+    }
+
+    @Override public boolean isNewTransaction() { return newTransaction; }
+    @Override public boolean isReadOnly() { return readOnly; }
+    @Override public boolean isRollbackOnly() { return rollbackMarker.rollbackOnly; }
+    @Override public void markRollbackOnly() { rollbackMarker.rollbackOnly = true; }
+
+    @Override
+    public <R> R resource(Class<R> type) {
+        if (session == null) {
+            throw new IllegalStateException("No session bound to this transaction status");
+        }
+        return type.cast(session);
+    }
+
+    Session session() { return session; }
+    HibernateTxStatus suspended() { return suspended; }
+    RollbackMarker rollbackMarker() { return rollbackMarker; }
+
+    /** Index into {@code ResourceRegistry}'s synchronization list where this transaction's own callbacks start. */
+    int synchronizationBaseline() { return synchronizationBaseline; }
+}

flash-extensions/flash-ext-data-hibernate/src/test/java/dev/relism/flash/ext/data/hibernate/HibernateTxManagerSynchronizationTest.java

@@ -0,0 +1,258 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.*;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Transaction synchronization semantics — the {@code beforeCommit}/{@code afterCommit}/
+ * {@code afterRollback} callbacks {@code Data#afterCommit} exposes, and the contract callers build
+ * on: "my callback runs once, for my transaction, on the right side of the commit".
+ *
+ * <p>None of this was covered before, and the gap was not academic: {@link #afterCommit_fires_on_commit}
+ * failed against the original {@code commit()}, which fired synchronizations only after
+ * {@code cleanupIfIdle()} had already dropped the ThreadLocal list holding them — so every callback
+ * was silently discarded, on every commit, with no error and no log. Downstream that meant an admin
+ * write landing in Postgres while the in-memory cache it was supposed to refresh never heard about
+ * it until the process restarted.
+ */
+class HibernateTxManagerSynchronizationTest {
+
+    static SessionFactory sf;
+    static HibernateTxManager manager;
+
+    @BeforeAll
+    static void setup() {
+        sf = TestHelper.buildSessionFactory();
+        manager = new HibernateTxManager(sf);
+    }
+
+    @AfterAll
+    static void teardown() {
+        if (sf != null) {
+            sf.close();
+        }
+    }
+
+    @AfterEach
+    void cleanup() {
+        ResourceRegistry.clear();
+    }
+
+    /** Records which callbacks ran, in order — order is part of the contract, not just the fact they ran. */
+    private static final class Recorder implements TxSynchronization {
+        final List<String> calls = new ArrayList<>();
+
+        @Override public void beforeCommit(boolean readOnly) { calls.add("beforeCommit:" + readOnly); }
+        @Override public void afterCommit() { calls.add("afterCommit"); }
+        @Override public void afterRollback() { calls.add("afterRollback"); }
+        @Override public void afterCompletion(TxOutcome outcome) { calls.add("afterCompletion:" + outcome); }
+    }
+
+    private static final List<String> COMMITTED = List.of("beforeCommit:false", "afterCommit", "afterCompletion:COMMITTED");
+    private static final List<String> ROLLED_BACK = List.of("afterRollback", "afterCompletion:ROLLED_BACK");
+
+    @Test
+    void afterCommit_fires_on_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(tx);
+
+        assertEquals(COMMITTED, recorder.calls);
+    }
+
+    @Test
+    void afterRollback_fires_on_rollback() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.rollback(tx);
+
+        assertEquals(ROLLED_BACK, recorder.calls);
+    }
+
+    /** A commit() call on a tx already marked rollback-only really rolls back — and has no commit to precede. */
+    @Test
+    void commit_of_a_rollback_only_tx_rolls_back_without_running_beforeCommit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        tx.markRollbackOnly();
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(tx);
+
+        assertEquals(ROLLED_BACK, recorder.calls);
+    }
+
+    /** beforeCommit runs inside the transaction: session still bound, transaction still active. */
+    @Test
+    void beforeCommit_runs_while_the_transaction_is_still_active() {
+        List<Boolean> stillActive = new ArrayList<>();
+        List<Session> sessionSeen = new ArrayList<>();
+
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        Session session = tx.resource(Session.class);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override
+            public void beforeCommit(boolean readOnly) {
+                stillActive.add(session.getTransaction().isActive());
+                // MANDATORY only succeeds while a transaction is bound — proof this runs inside it.
+                TxStatus joined = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.MANDATORY));
+                sessionSeen.add(joined.resource(Session.class));
+                manager.commit(joined);
+            }
+        });
+
+        manager.commit(tx);
+
+        assertEquals(List.of(true), stillActive, "the transaction must not have committed yet");
+        assertSame(session, sessionSeen.get(0), "the same session must still be bound, so writes land in this commit");
+    }
+
+    @Test
+    void beforeCommit_is_told_whether_the_transaction_is_read_only() {
+        Recorder readWrite = new Recorder();
+        TxStatus rw = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(readWrite);
+        manager.commit(rw);
+
+        Recorder readOnly = new Recorder();
+        TxStatus ro = manager.begin(TxDefinition.DEFAULTS.asReadOnly());
+        ResourceRegistry.addSynchronization(readOnly);
+        manager.commit(ro);
+
+        assertEquals("beforeCommit:false", readWrite.calls.get(0));
+        assertEquals("beforeCommit:true", readOnly.calls.get(0));
+    }
+
+    /** Throwing from beforeCommit is a veto: no commit, the rollback callbacks run, the exception propagates. */
+    @Test
+    void a_throwing_beforeCommit_vetoes_the_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        Session session = tx.resource(Session.class);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override public void beforeCommit(boolean readOnly) { throw new IllegalStateException("veto"); }
+        });
+        ResourceRegistry.addSynchronization(recorder);
+
+        IllegalStateException thrown = assertThrows(IllegalStateException.class, () -> manager.commit(tx));
+
+        assertEquals("veto", thrown.getMessage());
+        assertFalse(session.getTransaction().isActive(), "the vetoed transaction must be rolled back, not left open");
+        assertEquals(ROLLED_BACK, recorder.calls, "the surviving callbacks must hear ROLLED_BACK, not silence");
+    }
+
+    /**
+     * The load-bearing ordering detail: post-completion callbacks run <em>after</em> the committed
+     * session is unbound, so a callback that opens its own transaction (a cache reload, an outbox
+     * drain) gets a fresh one instead of silently joining the transaction that just committed.
+     */
+    @Test
+    void a_synchronization_may_open_its_own_transaction() {
+        List<Session> sessionsSeen = new ArrayList<>();
+        List<Boolean> wasNewTransaction = new ArrayList<>();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        Session committedSession = outer.resource(Session.class);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override
+            public void afterCommit() {
+                TxStatus own = manager.begin(TxDefinition.DEFAULTS);
+                sessionsSeen.add(own.resource(Session.class));
+                wasNewTransaction.add(own.isNewTransaction());
+                manager.commit(own);
+            }
+        });
+
+        manager.commit(outer);
+
+        assertEquals(1, sessionsSeen.size(), "the callback must have run");
+        assertEquals(List.of(true), wasNewTransaction, "must start its own transaction, not join the committed one");
+        assertNotSame(committedSession, sessionsSeen.get(0));
+    }
+
+    /** A joined (REQUIRED) inner commit is not a real commit — callbacks wait for the outermost one. */
+    @Test
+    void a_joined_commit_defers_synchronizations_to_the_outermost_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(inner);
+        assertEquals(List.of(), recorder.calls, "the joined commit did not commit anything yet");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, recorder.calls);
+    }
+
+    /** Each callback belongs to one transaction: a second transaction must not re-run the first's. */
+    @Test
+    void synchronizations_do_not_leak_into_the_next_transaction() {
+        Recorder recorder = new Recorder();
+        TxStatus first = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+        manager.commit(first);
+        recorder.calls.clear();
+
+        TxStatus second = manager.begin(TxDefinition.DEFAULTS);
+        manager.commit(second);
+
+        assertEquals(List.of(), recorder.calls);
+    }
+
+    /**
+     * A REQUIRES_NEW inner transaction suspends the outer one; committing the inner must not drag
+     * the still-pending outer transaction's callbacks along with it. They belong to a transaction
+     * that has not committed — and may yet roll back, in which case firing {@code afterCommit} for
+     * it would be a straight lie.
+     */
+    @Test
+    void a_requires_new_commit_leaves_the_suspended_transactions_synchronizations_alone() {
+        Recorder outerSync = new Recorder();
+        Recorder innerSync = new Recorder();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(outerSync);
+
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        ResourceRegistry.addSynchronization(innerSync);
+        manager.commit(inner);
+
+        assertEquals(COMMITTED, innerSync.calls);
+        assertEquals(List.of(), outerSync.calls, "the outer transaction has not committed yet");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, outerSync.calls);
+    }
+
+    /** A rolled-back inner REQUIRES_NEW must not fire the outer's callbacks either — same reason, opposite outcome. */
+    @Test
+    void a_requires_new_rollback_leaves_the_suspended_transactions_synchronizations_alone() {
+        Recorder outerSync = new Recorder();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(outerSync);
+
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        manager.rollback(inner);
+
+        assertEquals(List.of(), outerSync.calls, "the outer transaction is still open");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, outerSync.calls);
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/test/java/dev/relism/flash/ext/data/hibernate/HibernateTxManagerTest.java

@@ -0,0 +1,108 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import dev.relism.flash.ext.data.core.*;
+import org.hibernate.Session;
+import org.hibernate.SessionFactory;
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class HibernateTxManagerTest {
+    static SessionFactory sf;
+    static HibernateTxManager manager;
+
+    @BeforeAll
+    static void setup() {
+        sf = TestHelper.buildSessionFactory();
+        manager = new HibernateTxManager(sf);
+    }
+
+    @AfterAll
+    static void teardown() {
+        if (sf != null) {
+            sf.close();
+        }
+    }
+
+    @AfterEach
+    void cleanup() {
+        ResourceRegistry.clear();
+    }
+
+    @Test
+    void required_starts_new_when_absent() {
+        TxStatus s = manager.begin(TxDefinition.DEFAULTS);
+        assertNotNull(s.resource(Session.class));
+        assertTrue(s.isNewTransaction());
+        assertDoesNotThrow(() -> manager.commit(s));
+    }
+
+    @Test
+    void required_joins_existing_when_present() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        assertSame(outer.resource(Session.class), inner.resource(Session.class));
+        manager.rollback(outer);
+    }
+
+    @Test
+    void requires_new_uses_separate_session() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        assertNotSame(outer.resource(Session.class), inner.resource(Session.class));
+        manager.commit(inner);
+        manager.rollback(outer);
+    }
+
+    @Test
+    void rollback_on_joined_marks_outer_rollback_only() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        manager.rollback(inner);
+        assertTrue(outer.isRollbackOnly());
+        manager.rollback(outer);
+    }
+
+    /** SUPPORTS without an active transaction yields a sessionless status: not a transaction, no session to hand out. */
+    @Test
+    void supports_without_active_transaction_is_a_sessionless_no_op() {
+        TxStatus s = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.SUPPORTS));
+
+        assertFalse(s.isNewTransaction());
+        assertThrows(IllegalStateException.class, () -> s.resource(Session.class));
+        assertDoesNotThrow(() -> manager.commit(s));
+    }
+
+    @Test
+    void not_supported_suspends_the_active_transaction_and_restores_it_on_commit() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        Session outerSession = outer.resource(Session.class);
+
+        TxStatus suspended = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.NOT_SUPPORTED));
+        assertFalse(suspended.isNewTransaction());
+        assertThrows(IllegalStateException.class, () -> suspended.resource(Session.class));
+        manager.commit(suspended);
+
+        TxStatus rejoined = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        assertSame(outerSession, rejoined.resource(Session.class), "the suspended transaction must be back");
+        manager.rollback(outer);
+    }
+
+    @Test
+    void mandatory_without_active_transaction_is_rejected() {
+        assertThrows(IllegalStateException.class,
+                () -> manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.MANDATORY)));
+    }
+
+    /** A read-only join onto a read-write transaction is a contract violation, not a silent downgrade. */
+    @Test
+    void read_only_cannot_join_a_read_write_transaction() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        assertThrows(TxException.class,
+                () -> manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED).asReadOnly()));
+        manager.rollback(outer);
+    }
+}

flash-extensions/flash-ext-data-hibernate/src/test/java/dev/relism/flash/ext/data/hibernate/TestHelper.java

@@ -0,0 +1,24 @@
+package dev.relism.flash.ext.data.hibernate;
+
+import org.hibernate.SessionFactory;
+import org.hibernate.boot.MetadataSources;
+import org.hibernate.boot.registry.StandardServiceRegistry;
+import org.hibernate.boot.registry.StandardServiceRegistryBuilder;
+
+public class TestHelper {
+    public static SessionFactory buildSessionFactory() {
+        final StandardServiceRegistry registry = new StandardServiceRegistryBuilder()
+                .applySetting("hibernate.connection.url", "jdbc:h2:mem:tx-hibernate;DB_CLOSE_DELAY=-1")
+                .applySetting("hibernate.connection.driver_class", "org.h2.Driver")
+                .applySetting("hibernate.dialect", "org.hibernate.dialect.H2Dialect")
+                .applySetting("hibernate.hbm2ddl.auto", "none")
+                .applySetting("hibernate.show_sql", "false")
+                .build();
+        try {
+            return new MetadataSources(registry).buildMetadata().buildSessionFactory();
+        } catch (Exception e) {
+            StandardServiceRegistryBuilder.destroy(registry);
+            throw e;
+        }
+    }
+}

flash-extensions/flash-ext-data-jdbc/docs/README.md

@@ -0,0 +1,101 @@
+# flash-ext-data-jdbc
+
+JDBC backend for `flash-ext-data-core`.
+
+## Purpose
+
+This module implements `TxManager` on top of a `DataSource` and provides a raw-SQL repository base
+class.
+
+## How to use it
+
+### 1. Create the manager
+
+```java
+DataSource dataSource = ...;
+JdbcTxManager txManager = new JdbcTxManager(dataSource);
+DataExtension extension = new DataExtension(txManager);
+```
+
+### 2. Install the extension in Flash
+
+As with Hibernate, `DataExtension` registers `Tx` in the `FlashContext` and enables
+`@Transactional` on class-based handlers.
+
+### 3. Define a repository
+
+```java
+public final class UserRepository extends JdbcRepository<User, Long> {
+    public UserRepository(Tx tx) {
+        super(tx, "users", "id");
+    }
+
+    @Override
+    protected User mapRow(ResultSet rs) throws SQLException {
+        return new User(rs.getLong("id"), rs.getString("name"));
+    }
+}
+```
+
+Here too you can expose reusable `Spec`s and compose queries from the service layer:
+
+```java
+public final class UserRepository extends JdbcRepository<User, Long> {
+    public static final SpecBuilder.FieldSpec<User, String> EMAIL = SpecBuilder.field("email");
+
+    public UserRepository(Tx tx) {
+        super(tx, "users", "id");
+    }
+}
+```
+
+Saving and updating need an explicit binding:
+
+```java
+@Override
+protected String insertSql() {
+    return "insert into users(name) values(?)";
+}
+
+@Override
+protected void bindInsert(PreparedStatement ps, User entity) throws SQLException {
+    ps.setString(1, entity.name());
+}
+```
+
+## How it works underneath
+
+- The current transaction exposes a `Connection`.
+- `Tx.resource(Connection.class)` retrieves the connection bound to the thread.
+- `REQUIRES_NEW` suspends the active connection and opens a new one.
+- `NOT_SUPPORTED` suspends the context and continues without a transaction.
+
+## Repository base class
+
+`JdbcRepository` provides:
+
+- `select` queries through `queryOne`, `queryMany`
+- mutations through `mutate`
+- persistence through `doSave`, `doUpdate`
+- paging through `doFindPage`
+- bulk `deleteAll(Spec<T>)`
+- raw helpers `queryOne(...)`, `queryMany(...)`, `mutate(...)`
+
+Concrete repositories only have to translate between `ResultSet` and the domain.
+
+## Transactional semantics
+
+- `REQUIRED`: join, or open a new transaction.
+- `REQUIRES_NEW`: suspend the current context.
+- `SUPPORTS`: join if a transaction exists, otherwise no-op.
+- `NOT_SUPPORTED`: suspend and continue without a transaction.
+- `MANDATORY`: fail if there is no transaction.
+
+## Notes
+
+- The `Connection` is closed when a new transaction ends.
+- Synchronizations registered in a transaction fire when *that* transaction completes:
+  `beforeCommit` while it is still active and the `Connection` still bound, the post-completion
+  hooks once it is unbound. See `flash-ext-data-core/docs/README.md` for the full contract.
+- If a repository uses `doDelete(T)`, the default behaviour is unsupported: use `deleteById` or
+  override it.

flash-extensions/flash-ext-data-jdbc/pom.xml

@@ -0,0 +1,71 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-data-jdbc</artifactId>
+
+    <properties>
+        <jacoco.version>0.8.12</jacoco.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-ext-data-core</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.zaxxer</groupId>
+            <artifactId>HikariCP</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>com.h2database</groupId>
+            <artifactId>h2</artifactId>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
+                <version>${jacoco.version}</version>
+                <configuration>
+                    <rules>
+                        <rule>
+                            <element>BUNDLE</element>
+                            <limits>
+                                <limit>
+                                    <counter>LINE</counter>
+                                    <value>COVEREDRATIO</value>
+                                    <minimum>0.80</minimum>
+                                </limit>
+                            </limits>
+                        </rule>
+                    </rules>
+                </configuration>
+            </plugin>
+        </plugins>
+    </build>
+</project>

flash-extensions/flash-ext-data-jdbc/src/main/java/dev/relism/flash/ext/data/jdbc/JdbcRepository.java

@@ -0,0 +1,201 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.*;
+
+import java.sql.*;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Optional;
+
+public abstract class JdbcRepository<T, ID> extends Repository<T, ID> {
+
+    private final String table;
+    private final String idColumn;
+
+    protected JdbcRepository(Tx tx, String table, String idColumn) {
+        super(tx);
+        this.table = table;
+        this.idColumn = idColumn;
+    }
+
+    protected Connection connection() {
+        return tx().resource(Connection.class);
+    }
+
+    protected abstract T mapRow(ResultSet rs) throws SQLException;
+    protected abstract void bindInsert(PreparedStatement ps, T entity) throws SQLException;
+    protected abstract void bindUpdate(PreparedStatement ps, T entity) throws SQLException;
+    protected abstract String insertSql();
+    protected abstract String updateSql();
+
+    @Override
+    protected Optional<T> doFindById(ID id) {
+        return queryOne("select * from " + table + " where " + idColumn + " = ?", ps -> ps.setObject(1, id));
+    }
+
+    @Override
+    protected List<T> doFind(Query<T> query) {
+        JdbcSpecContext ctx = new JdbcSpecContext();
+        String where = query.spec() != null ? " where " + query.spec().toFragment(ctx) : "";
+        String order = query.sort() != null && query.sort().isSorted() ? " order by " + orderClause(query.sort()) : "";
+        String paging = query.isPaged() ? " limit ? offset ?" : "";
+
+        return queryMany("select * from " + table + where + order + paging, ps -> {
+            if (query.isPaged()) {
+                ctx.applyParameters(ps);
+                int base = ctx.size();
+                ps.setInt(base + 1, query.size());
+                ps.setInt(base + 2, query.page() * query.size());
+                return;
+            }
+            ctx.applyParameters(ps);
+        });
+    }
+
+    @Override
+    protected Optional<T> doFindOne(Spec<T> spec) {
+        return doFind(Query.<T>all().where(spec).page(0, 1)).stream().findFirst();
+    }
+
+    @Override
+    protected Page<T> doFindPage(Query<T> query) {
+        if (!query.isPaged()) {
+            throw new IllegalArgumentException("Paged query requires page and size");
+        }
+        long total = countWhere(query.spec());
+        List<T> content = doFind(query);
+        return new Page<>(content, query.page(), query.size(), total);
+    }
+
+    @Override
+    protected boolean doExistsById(ID id) {
+        return queryOne("select 1 from " + table + " where " + idColumn + " = ?", ps -> ps.setObject(1, id), rs -> rs.getInt(1)).isPresent();
+    }
+
+    @Override
+    protected long doCount() {
+        return queryOne("select count(*) from " + table, ps -> {}, rs -> rs.getLong(1)).orElse(0L);
+    }
+
+    @Override
+    protected T doSave(T entity) {
+        try (PreparedStatement ps = connection().prepareStatement(insertSql(), Statement.RETURN_GENERATED_KEYS)) {
+            bindInsert(ps, entity);
+            ps.executeUpdate();
+            applyGeneratedKey(ps, entity);
+            return entity;
+        } catch (SQLException e) {
+            throw new TxException(e);
+        }
+    }
+
+    @Override
+    protected List<T> doSaveAll(Iterable<T> entities) {
+        List<T> saved = new ArrayList<>();
+        for (T entity : entities) {
+            saved.add(doSave(entity));
+        }
+        return saved;
+    }
+
+    @Override
+    protected T doUpdate(T entity) {
+        try (PreparedStatement ps = connection().prepareStatement(updateSql())) {
+            bindUpdate(ps, entity);
+            ps.executeUpdate();
+            return entity;
+        } catch (SQLException e) {
+            throw new TxException(e);
+        }
+    }
+
+    @Override
+    protected void doDelete(T entity) {
+        throw new UnsupportedOperationException("Override doDelete() or use deleteById()");
+    }
+
+    @Override
+    protected void doDeleteById(ID id) {
+        mutate("delete from " + table + " where " + idColumn + " = ?", ps -> ps.setObject(1, id));
+    }
+
+    @Override
+    protected int doDeleteAll(Spec<T> spec) {
+        JdbcSpecContext ctx = new JdbcSpecContext();
+        String where = " where " + spec.toFragment(ctx);
+        return mutate("delete from " + table + where, ctx::applyParameters);
+    }
+
+    @Override
+    protected int doUpdateAll(Spec<T> spec, T patch) {
+        throw new UnsupportedOperationException("Override doUpdateAll() for bulk UPDATE support");
+    }
+
+    protected Optional<T> queryOne(String sql, SqlBinder params) {
+        List<T> r = queryMany(sql, params);
+        return r.isEmpty() ? Optional.empty() : Optional.of(r.get(0));
+    }
+
+    protected <R> Optional<R> queryOne(String sql, SqlBinder params, SqlMapper<R> mapper) {
+        try (PreparedStatement ps = connection().prepareStatement(sql)) {
+            params.bind(ps);
+            try (ResultSet rs = ps.executeQuery()) {
+                return rs.next() ? Optional.of(mapper.map(rs)) : Optional.empty();
+            }
+        } catch (SQLException e) {
+            throw new TxException(e);
+        }
+    }
+
+    protected List<T> queryMany(String sql, SqlBinder params) {
+        try (PreparedStatement ps = connection().prepareStatement(sql)) {
+            params.bind(ps);
+            try (ResultSet rs = ps.executeQuery()) {
+                List<T> results = new ArrayList<>();
+                while (rs.next()) results.add(mapRow(rs));
+                return results;
+            }
+        } catch (SQLException e) {
+            throw new TxException(e);
+        }
+    }
+
+    protected int mutate(String sql, SqlBinder params) {
+        try (PreparedStatement ps = connection().prepareStatement(sql)) {
+            params.bind(ps);
+            return ps.executeUpdate();
+        } catch (SQLException e) {
+            throw new TxException(e);
+        }
+    }
+
+    protected void applyGeneratedKey(PreparedStatement ps, T entity) throws SQLException {
+        // override when entity has a generated PK
+    }
+
+    protected Class<T> entityType() {
+        return null;
+    }
+
+    private long countWhere(Spec<T> spec) {
+        JdbcSpecContext ctx = new JdbcSpecContext();
+        String where = spec != null ? " where " + spec.toFragment(ctx) : "";
+        return queryOne("select count(*) from " + table + where, ctx::applyParameters, rs -> rs.getLong(1)).orElse(0L);
+    }
+
+    private String orderClause(Sort sort) {
+        return sort.columns().stream()
+                .map(c -> c.column() + (c.asc() ? " ASC" : " DESC"))
+                .collect(java.util.stream.Collectors.joining(", "));
+    }
+
+    @FunctionalInterface
+    public interface SqlBinder {
+        void bind(PreparedStatement ps) throws SQLException;
+    }
+
+    @FunctionalInterface
+    public interface SqlMapper<R> {
+        R map(ResultSet rs) throws SQLException;
+    }
+}

flash-extensions/flash-ext-data-jdbc/src/main/java/dev/relism/flash/ext/data/jdbc/JdbcSpecContext.java

@@ -0,0 +1,28 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.SpecContext;
+
+import java.sql.PreparedStatement;
+import java.sql.SQLException;
+import java.util.ArrayList;
+import java.util.List;
+
+final class JdbcSpecContext implements SpecContext {
+    private final List<Object> params = new ArrayList<>();
+
+    @Override
+    public String bind(Object value) {
+        params.add(value);
+        return "?";
+    }
+
+    void applyParameters(PreparedStatement ps) throws SQLException {
+        for (int i = 0; i < params.size(); i++) {
+            ps.setObject(i + 1, params.get(i));
+        }
+    }
+
+    int size() {
+        return params.size();
+    }
+}

flash-extensions/flash-ext-data-jdbc/src/main/java/dev/relism/flash/ext/data/jdbc/JdbcTxManager.java

@@ -0,0 +1,223 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.*;
+
+import javax.sql.DataSource;
+import java.sql.Connection;
+import java.sql.SQLException;
+import java.util.Objects;
+
+public class JdbcTxManager implements TxManager {
+    private static final TxResourceKey JDBC_STATUS_KEY = TxResourceKey.of("jdbc.tx.status");
+    private static final TxResourceKey JDBC_SUSPENDED_KEY = TxResourceKey.of("jdbc.tx.suspended");
+
+    private final DataSource ds;
+
+    public JdbcTxManager(DataSource ds) {
+        this.ds = Objects.requireNonNull(ds);
+    }
+
+    @Override
+    public TxStatus begin(TxDefinition definition) {
+        return switch (definition.propagation()) {
+            case REQUIRED -> ResourceRegistry.isBound(JDBC_STATUS_KEY)
+                    ? joinExisting(definition)
+                    : beginNew(definition);
+            case REQUIRES_NEW -> beginNew(definition);
+            case SUPPORTS -> ResourceRegistry.isBound(JDBC_STATUS_KEY)
+                    ? joinExisting(definition)
+                    : noOp(definition);
+            case MANDATORY -> {
+                if (!ResourceRegistry.isBound(JDBC_STATUS_KEY))
+                    throw new IllegalStateException("MANDATORY: no active transaction");
+                yield joinExisting(definition);
+            }
+            case NOT_SUPPORTED -> {
+                JdbcTxStatus suspended = suspendIfNeeded();
+                yield noOp(definition, suspended);
+            }
+        };
+    }
+
+    private TxStatus beginNew(TxDefinition definition) {
+        Connection conn = null;
+        // Anything already registered belongs to an enclosing transaction this one is nested
+        // inside (or suspended over) — see ResourceRegistry#fireSynchronizations.
+        int synchronizationBaseline = ResourceRegistry.synchronizationCount();
+        JdbcTxStatus suspended = suspendIfNeeded();
+        boolean bound = false;
+        try {
+            conn = ds.getConnection();
+            conn.setAutoCommit(false);
+            if (definition.readOnly()) conn.setReadOnly(true);
+            if (definition.isolation() != TransactionIsolation.DEFAULT) {
+                conn.setTransactionIsolation(definition.isolation().level());
+            }
+            JdbcTxStatus status = new JdbcTxStatus(
+                    conn,
+                    true,
+                    definition.readOnly(),
+                    suspended,
+                    new JdbcTxStatus.RollbackMarker(),
+                    synchronizationBaseline
+            );
+            ResourceRegistry.bind(JDBC_STATUS_KEY, status);
+            bound = true;
+            return status;
+        } catch (SQLException e) {
+            silentClose(conn);
+            throw new TxException(e);
+        } finally {
+            if (!bound && suspended != null) {
+                ResourceRegistry.unbind(JDBC_SUSPENDED_KEY);
+                ResourceRegistry.bind(JDBC_STATUS_KEY, suspended);
+            }
+        }
+    }
+
+    private TxStatus joinExisting(TxDefinition definition) {
+        JdbcTxStatus existing = ResourceRegistry.get(JDBC_STATUS_KEY, JdbcTxStatus.class);
+        if (definition.readOnly() && !existing.isReadOnly()) {
+            throw new TxException("Cannot join read-write tx as read-only");
+        }
+        // Baseline 0 is never read: a joined status isn't a new transaction, so commit()/rollback()
+        // hand it straight back to the transaction it joined without firing anything.
+        return new JdbcTxStatus(
+                existing.connection(),
+                false,
+                definition.readOnly(),
+                null,
+                existing.rollbackMarker(),
+                0
+        );
+    }
+
+    private TxStatus noOp(TxDefinition definition) {
+        return noOp(definition, null);
+    }
+
+    private TxStatus noOp(TxDefinition definition, JdbcTxStatus suspended) {
+        return new JdbcTxStatus(null, false, definition.readOnly(), suspended, new JdbcTxStatus.RollbackMarker(), 0);
+    }
+
+    private JdbcTxStatus suspendIfNeeded() {
+        JdbcTxStatus suspended = ResourceRegistry.getOrNull(JDBC_STATUS_KEY, JdbcTxStatus.class);
+        if (suspended != null) {
+            ResourceRegistry.unbind(JDBC_STATUS_KEY);
+            ResourceRegistry.bind(JDBC_SUSPENDED_KEY, suspended);
+        }
+        return suspended;
+    }
+
+    @Override
+    public void commit(TxStatus status) {
+        JdbcTxStatus s = (JdbcTxStatus) status;
+        if (!s.isNewTransaction()) {
+            resumeIfNeeded(s);
+            cleanupIfIdle();
+            return;
+        }
+        TxOutcome outcome = null;
+        try {
+            if (s.isRollbackOnly()) {
+                s.connection().rollback();
+                outcome = TxOutcome.ROLLED_BACK;
+            } else {
+                // Still inside the transaction, connection still bound: a beforeCommit callback
+                // can write through it and land in this same commit. Throwing from there vetoes
+                // the commit — see TxSynchronization.
+                ResourceRegistry.fireBeforeCommit(s.isReadOnly(), s.synchronizationBaseline());
+                s.connection().commit();
+                outcome = TxOutcome.COMMITTED;
+            }
+        } catch (SQLException e) {
+            TxException wrapped = new TxException(e);
+            outcome = rollbackAfterFailedCommit(s, wrapped);
+            throw wrapped;
+        } catch (RuntimeException e) {
+            outcome = rollbackAfterFailedCommit(s, e);
+            throw e;
+        } finally {
+            // Unbind the connection before firing, so a callback that opens its own transaction
+            // gets a fresh one instead of joining the connection that just committed — and fire
+            // before cleanupIfIdle(), whose ResourceRegistry.cleanup() drops the pending list.
+            cleanupAndResume(s);
+            if (outcome != null) ResourceRegistry.fireSynchronizations(outcome, s.synchronizationBaseline());
+            cleanupIfIdle();
+        }
+    }
+
+    /**
+     * Nothing was committed — a vetoing {@code beforeCommit}, or a commit that failed outright —
+     * so undo whatever the transaction had done and report {@code ROLLED_BACK} to the callbacks
+     * still queued behind it. A failure to roll back is attached to the exception already on its
+     * way out rather than replacing it: that one explains what actually went wrong.
+     */
+    private static TxOutcome rollbackAfterFailedCommit(JdbcTxStatus s, Throwable propagating) {
+        try {
+            s.connection().rollback();
+        } catch (SQLException suppressed) {
+            propagating.addSuppressed(suppressed);
+        }
+        return TxOutcome.ROLLED_BACK;
+    }
+
+    @Override
+    public void rollback(TxStatus status) {
+        JdbcTxStatus s = (JdbcTxStatus) status;
+        if (!s.isNewTransaction()) {
+            s.markRollbackOnly();
+            resumeIfNeeded(s);
+            cleanupIfIdle();
+            return;
+        }
+        try {
+            s.connection().rollback();
+        } catch (SQLException e) {
+            throw new TxException(e);
+        } finally {
+            // Same order as commit() above, for the same two reasons.
+            cleanupAndResume(s);
+            ResourceRegistry.fireSynchronizations(TxOutcome.ROLLED_BACK, s.synchronizationBaseline());
+            cleanupIfIdle();
+        }
+    }
+
+    private void cleanupAndResume(JdbcTxStatus status) {
+        ResourceRegistry.unbind(JDBC_STATUS_KEY);
+        try {
+            if (status.connection() != null) {
+                status.connection().close();
+            }
+        } catch (SQLException ignored) {
+        }
+        resumeIfNeeded(status);
+    }
+
+    private void cleanupIfIdle() {
+        if (!ResourceRegistry.isBound(JDBC_STATUS_KEY) && !ResourceRegistry.isBound(JDBC_SUSPENDED_KEY)) {
+            ResourceRegistry.cleanup();
+        }
+    }
+
+    private void resumeIfNeeded(JdbcTxStatus status) {
+        JdbcTxStatus suspended = status.suspended();
+        if (suspended == null) {
+            suspended = ResourceRegistry.getOrNull(JDBC_SUSPENDED_KEY, JdbcTxStatus.class);
+        }
+        if (suspended != null) {
+            ResourceRegistry.unbind(JDBC_SUSPENDED_KEY);
+            ResourceRegistry.bind(JDBC_STATUS_KEY, suspended);
+        }
+    }
+
+    private void silentClose(Connection connection) {
+        if (connection == null) {
+            return;
+        }
+        try {
+            connection.close();
+        } catch (SQLException ignored) {
+        }
+    }
+}

flash-extensions/flash-ext-data-jdbc/src/main/java/dev/relism/flash/ext/data/jdbc/JdbcTxStatus.java

@@ -0,0 +1,59 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.TxStatus;
+
+import java.sql.Connection;
+
+class JdbcTxStatus implements TxStatus {
+    static final class RollbackMarker {
+        boolean rollbackOnly;
+    }
+
+    private final Connection connection;
+    private final boolean newTransaction;
+    private final boolean readOnly;
+    private final JdbcTxStatus suspended;
+    private final RollbackMarker rollbackMarker;
+    private final int synchronizationBaseline;
+
+    // No requireNonNull on the connection: a SUPPORTS-without-a-transaction or a NOT_SUPPORTED
+    // status is deliberately connectionless (see JdbcTxManager#noOp), and rejecting null here
+    // turned both of those propagations into an NPE at begin() — the Hibernate manager has
+    // always allowed it. resource() reports the real mistake, asking a connectionless status for
+    // its connection, where it can name it.
+    JdbcTxStatus(
+            Connection connection,
+            boolean newTransaction,
+            boolean readOnly,
+            JdbcTxStatus suspended,
+            RollbackMarker rollbackMarker,
+            int synchronizationBaseline
+    ) {
+        this.connection = connection;
+        this.newTransaction = newTransaction;
+        this.readOnly = readOnly;
+        this.suspended = suspended;
+        this.rollbackMarker = rollbackMarker;
+        this.synchronizationBaseline = synchronizationBaseline;
+    }
+
+    @Override public boolean isNewTransaction() { return newTransaction; }
+    @Override public boolean isReadOnly() { return readOnly; }
+    @Override public boolean isRollbackOnly() { return rollbackMarker.rollbackOnly; }
+    @Override public void markRollbackOnly() { rollbackMarker.rollbackOnly = true; }
+
+    @Override
+    public <R> R resource(Class<R> type) {
+        if (connection == null) {
+            throw new IllegalStateException("No connection bound to this transaction status");
+        }
+        return type.cast(connection);
+    }
+
+    Connection connection() { return connection; }
+    JdbcTxStatus suspended() { return suspended; }
+    RollbackMarker rollbackMarker() { return rollbackMarker; }
+
+    /** Index into {@code ResourceRegistry}'s synchronization list where this transaction's own callbacks start. */
+    int synchronizationBaseline() { return synchronizationBaseline; }
+}

flash-extensions/flash-ext-data-jdbc/src/test/java/dev/relism/flash/ext/data/jdbc/JdbcTxManagerSynchronizationTest.java

@@ -0,0 +1,216 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.*;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+
+import java.sql.Connection;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+/**
+ * Transaction synchronization semantics for the JDBC manager — the same contract {@code
+ * HibernateTxManagerSynchronizationTest} pins down for the Hibernate one, kept deliberately
+ * parallel: the two managers are interchangeable behind {@code TxManager}, so a callback must not
+ * observe a different lifecycle depending on which one is installed.
+ */
+class JdbcTxManagerSynchronizationTest {
+
+    private final JdbcTxManager manager = new JdbcTxManager(new TestDataSource());
+
+    @AfterEach
+    void cleanup() {
+        ResourceRegistry.clear();
+    }
+
+    /** Records which callbacks ran, in order — order is part of the contract, not just the fact they ran. */
+    private static final class Recorder implements TxSynchronization {
+        final List<String> calls = new ArrayList<>();
+
+        @Override public void beforeCommit(boolean readOnly) { calls.add("beforeCommit:" + readOnly); }
+        @Override public void afterCommit() { calls.add("afterCommit"); }
+        @Override public void afterRollback() { calls.add("afterRollback"); }
+        @Override public void afterCompletion(TxOutcome outcome) { calls.add("afterCompletion:" + outcome); }
+    }
+
+    private static final List<String> COMMITTED = List.of("beforeCommit:false", "afterCommit", "afterCompletion:COMMITTED");
+    private static final List<String> ROLLED_BACK = List.of("afterRollback", "afterCompletion:ROLLED_BACK");
+
+    @Test
+    void afterCommit_fires_on_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(tx);
+
+        assertEquals(COMMITTED, recorder.calls);
+    }
+
+    @Test
+    void afterRollback_fires_on_rollback() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.rollback(tx);
+
+        assertEquals(ROLLED_BACK, recorder.calls);
+    }
+
+    @Test
+    void commit_of_a_rollback_only_tx_rolls_back_without_running_beforeCommit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        tx.markRollbackOnly();
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(tx);
+
+        assertEquals(ROLLED_BACK, recorder.calls);
+    }
+
+    /** beforeCommit runs inside the transaction: connection still bound, nothing committed yet. */
+    @Test
+    void beforeCommit_runs_while_the_transaction_is_still_active() {
+        List<Connection> connectionSeen = new ArrayList<>();
+
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        Connection connection = tx.resource(Connection.class);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override
+            public void beforeCommit(boolean readOnly) {
+                // MANDATORY only succeeds while a transaction is bound — proof this runs inside it.
+                TxStatus joined = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.MANDATORY));
+                connectionSeen.add(joined.resource(Connection.class));
+                manager.commit(joined);
+            }
+        });
+
+        manager.commit(tx);
+
+        assertSame(connection, connectionSeen.get(0), "the same connection must still be bound, so writes land in this commit");
+    }
+
+    @Test
+    void beforeCommit_is_told_whether_the_transaction_is_read_only() {
+        Recorder readWrite = new Recorder();
+        TxStatus rw = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(readWrite);
+        manager.commit(rw);
+
+        Recorder readOnly = new Recorder();
+        TxStatus ro = manager.begin(TxDefinition.DEFAULTS.asReadOnly());
+        ResourceRegistry.addSynchronization(readOnly);
+        manager.commit(ro);
+
+        assertEquals("beforeCommit:false", readWrite.calls.get(0));
+        assertEquals("beforeCommit:true", readOnly.calls.get(0));
+    }
+
+    /** Throwing from beforeCommit is a veto: no commit, the rollback callbacks run, the exception propagates. */
+    @Test
+    void a_throwing_beforeCommit_vetoes_the_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus tx = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override public void beforeCommit(boolean readOnly) { throw new IllegalStateException("veto"); }
+        });
+        ResourceRegistry.addSynchronization(recorder);
+
+        IllegalStateException thrown = assertThrows(IllegalStateException.class, () -> manager.commit(tx));
+
+        assertEquals("veto", thrown.getMessage());
+        assertEquals(ROLLED_BACK, recorder.calls, "the surviving callbacks must hear ROLLED_BACK, not silence");
+    }
+
+    /** Post-completion callbacks run after the committed connection is unbound, so opening a transaction gets a fresh one. */
+    @Test
+    void a_synchronization_may_open_its_own_transaction() {
+        List<Connection> connectionsSeen = new ArrayList<>();
+        List<Boolean> wasNewTransaction = new ArrayList<>();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        Connection committedConnection = outer.resource(Connection.class);
+        ResourceRegistry.addSynchronization(new TxSynchronization() {
+            @Override
+            public void afterCommit() {
+                TxStatus own = manager.begin(TxDefinition.DEFAULTS);
+                connectionsSeen.add(own.resource(Connection.class));
+                wasNewTransaction.add(own.isNewTransaction());
+                manager.commit(own);
+            }
+        });
+
+        manager.commit(outer);
+
+        assertEquals(1, connectionsSeen.size(), "the callback must have run");
+        assertEquals(List.of(true), wasNewTransaction, "must start its own transaction, not join the committed one");
+        assertNotSame(committedConnection, connectionsSeen.get(0));
+    }
+
+    @Test
+    void a_joined_commit_defers_synchronizations_to_the_outermost_commit() {
+        Recorder recorder = new Recorder();
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        ResourceRegistry.addSynchronization(recorder);
+
+        manager.commit(inner);
+        assertEquals(List.of(), recorder.calls, "the joined commit did not commit anything yet");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, recorder.calls);
+    }
+
+    @Test
+    void synchronizations_do_not_leak_into_the_next_transaction() {
+        Recorder recorder = new Recorder();
+        TxStatus first = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(recorder);
+        manager.commit(first);
+        recorder.calls.clear();
+
+        TxStatus second = manager.begin(TxDefinition.DEFAULTS);
+        manager.commit(second);
+
+        assertEquals(List.of(), recorder.calls);
+    }
+
+    @Test
+    void a_requires_new_commit_leaves_the_suspended_transactions_synchronizations_alone() {
+        Recorder outerSync = new Recorder();
+        Recorder innerSync = new Recorder();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(outerSync);
+
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        ResourceRegistry.addSynchronization(innerSync);
+        manager.commit(inner);
+
+        assertEquals(COMMITTED, innerSync.calls);
+        assertEquals(List.of(), outerSync.calls, "the outer transaction has not committed yet");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, outerSync.calls);
+    }
+
+    @Test
+    void a_requires_new_rollback_leaves_the_suspended_transactions_synchronizations_alone() {
+        Recorder outerSync = new Recorder();
+
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        ResourceRegistry.addSynchronization(outerSync);
+
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        manager.rollback(inner);
+
+        assertEquals(List.of(), outerSync.calls, "the outer transaction is still open");
+
+        manager.commit(outer);
+        assertEquals(COMMITTED, outerSync.calls);
+    }
+}

flash-extensions/flash-ext-data-jdbc/src/test/java/dev/relism/flash/ext/data/jdbc/JdbcTxManagerTest.java

@@ -0,0 +1,87 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import dev.relism.flash.ext.data.core.*;
+import org.junit.jupiter.api.AfterEach;
+import org.junit.jupiter.api.Test;
+
+import java.sql.Connection;
+
+import static org.junit.jupiter.api.Assertions.*;
+
+class JdbcTxManagerTest {
+    private final JdbcTxManager manager = new JdbcTxManager(new TestDataSource());
+
+    @AfterEach
+    void cleanup() {
+        ResourceRegistry.clear();
+    }
+
+    @Test
+    void required_starts_new_when_absent() {
+        TxStatus s = manager.begin(TxDefinition.DEFAULTS);
+        assertTrue(s.isNewTransaction());
+        assertDoesNotThrow(() -> manager.commit(s));
+    }
+
+    @Test
+    void required_joins_existing_when_present() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        assertSame(outer.resource(Connection.class), inner.resource(Connection.class));
+        assertFalse(inner.isNewTransaction());
+        manager.rollback(outer);
+    }
+
+    @Test
+    void requires_new_creates_distinct_connection() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRES_NEW));
+        assertNotSame(outer.resource(Connection.class), inner.resource(Connection.class));
+        manager.commit(inner);
+        manager.rollback(outer);
+    }
+
+    @Test
+    void rollback_on_joined_marks_outer_rollback_only() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        TxStatus inner = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        manager.rollback(inner);
+        assertTrue(outer.isRollbackOnly());
+        manager.rollback(outer);
+    }
+
+    /**
+     * SUPPORTS without an active transaction yields a connectionless status — it must not be a
+     * transaction, and asking it for a connection must say so rather than NPE. Both propagations
+     * that produce one used to throw {@link NullPointerException} straight out of {@code begin()}.
+     */
+    @Test
+    void supports_without_active_transaction_is_a_connectionless_no_op() {
+        TxStatus s = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.SUPPORTS));
+
+        assertFalse(s.isNewTransaction());
+        assertThrows(IllegalStateException.class, () -> s.resource(Connection.class));
+        assertDoesNotThrow(() -> manager.commit(s));
+    }
+
+    @Test
+    void not_supported_suspends_the_active_transaction_and_restores_it_on_commit() {
+        TxStatus outer = manager.begin(TxDefinition.DEFAULTS);
+        Connection outerConnection = outer.resource(Connection.class);
+
+        TxStatus suspended = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.NOT_SUPPORTED));
+        assertFalse(suspended.isNewTransaction());
+        assertThrows(IllegalStateException.class, () -> suspended.resource(Connection.class));
+        manager.commit(suspended);
+
+        TxStatus rejoined = manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.REQUIRED));
+        assertSame(outerConnection, rejoined.resource(Connection.class), "the suspended transaction must be back");
+        manager.rollback(outer);
+    }
+
+    @Test
+    void mandatory_without_active_transaction_is_rejected() {
+        assertThrows(IllegalStateException.class,
+                () -> manager.begin(TxDefinition.DEFAULTS.withPropagation(TransactionPropagation.MANDATORY)));
+    }
+}

flash-extensions/flash-ext-data-jdbc/src/test/java/dev/relism/flash/ext/data/jdbc/TestDataSource.java

@@ -0,0 +1,37 @@
+package dev.relism.flash.ext.data.jdbc;
+
+import javax.sql.DataSource;
+import java.io.PrintWriter;
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.SQLException;
+import java.util.logging.Logger;
+
+/**
+ * A bare in-memory H2 {@link DataSource} — one fresh connection per {@code getConnection()}, which
+ * is all {@code JdbcTxManager} needs to exercise real commit/rollback and suspension. Every method
+ * outside the two {@code getConnection} overloads throws: nothing under test calls them, and a
+ * loud failure beats a silent stub if that ever changes.
+ */
+final class TestDataSource implements DataSource {
+
+    static final String URL = "jdbc:h2:mem:tx-jdbc;DB_CLOSE_DELAY=-1";
+
+    @Override
+    public Connection getConnection() throws SQLException {
+        return DriverManager.getConnection(URL);
+    }
+
+    @Override
+    public Connection getConnection(String username, String password) throws SQLException {
+        return DriverManager.getConnection(URL, username, password);
+    }
+
+    @Override public <T> T unwrap(Class<T> iface) { throw new UnsupportedOperationException(); }
+    @Override public boolean isWrapperFor(Class<?> iface) { return false; }
+    @Override public PrintWriter getLogWriter() { throw new UnsupportedOperationException(); }
+    @Override public void setLogWriter(PrintWriter out) { throw new UnsupportedOperationException(); }
+    @Override public void setLoginTimeout(int seconds) { throw new UnsupportedOperationException(); }
+    @Override public int getLoginTimeout() { return 0; }
+    @Override public Logger getParentLogger() { throw new UnsupportedOperationException(); }
+}

flash-extensions/flash-ext-jackson/README.md

@@ -0,0 +1,116 @@
+# flash-ext-jackson
+
+Jackson JSON integration for Flash with an opinionated auto-marshal middleware.
+
+## What it provides
+
+| Component | Description |
+|---|---|
+| `JacksonExtension` | Registers JSON services into `FlashContext` |
+| `Json` | JSON read/write helper (`body`, `bodyFrom`, `write`, `writeView`) |
+| `ObjectMapper` | Raw mapper escape hatch for advanced usage |
+| `JacksonMiddleware` | `autoJson()` middleware for automatic outbound JSON marshalling |
+
+Default mapper behavior (`new JacksonExtension()`):
+
+- auto-discovers Jackson modules on classpath (`findAndAddModules()`)
+- includes Java Time support (`jackson-datatype-jsr310`)
+- writes date/time values as ISO-8601 strings (not numeric timestamps)
+
+## Recommended default
+
+Install the extension, then apply `autoJson()` once at app or scope level.
+
+```java
+JacksonExtension jackson = new JacksonExtension();
+
+FlashApp app = FlashApp.create(8080)
+    .install(jackson)
+    .use(jackson.autoJson());
+
+app.startAndBlock();
+```
+
+Behavior of `autoJson()`:
+
+- pass-through: `null`, `Response`, `byte[]`, `String`, `CharSequence`
+- any other return value: serialize to JSON `byte[]`
+- sets `Content-Type: application/json` for marshalled responses
+- serialization failures throw `IllegalStateException`
+
+This keeps handlers concise while preserving Flash's direct byte write path.
+
+## Installation
+
+```xml
+<dependency>
+    <groupId>dev.relism</groupId>
+    <artifactId>flash-ext-jackson</artifactId>
+    <version>1.1-indev2</version>
+</dependency>
+```
+
+## Json helper API
+
+Use `Json` when you want explicit, local control in a handler.
+
+```java
+@POST("/users")
+public final class CreateUser extends RequestHandler {
+    private Json json;
+
+    @Override
+    protected void onInit() {
+        json = require(Json.class);
+    }
+
+    @Override
+    public Object handle(Request req, Response res) throws Exception {
+        CreateUserBody body = json.body(req, CreateUserBody.class);
+        UserDto created = service.create(body);
+        res.status(201);
+        return json.write(res, created);
+    }
+}
+```
+
+Methods:
+
+- `body(req, Type.class)` -> parse from `req.body().bytes()`
+- `bodyFrom(req, Type.class)` -> parse from `req.body().stream()`
+- `write(res, obj)` -> writes JSON string and sets JSON content type
+- `writeView(res, obj, View.class)` -> JSON with Jackson `@JsonView`
+- `mapper()` -> raw `ObjectMapper`
+
+## Custom mapper
+
+```java
+ObjectMapper mapper = JsonMapper.builder()
+    .addModule(new JavaTimeModule())
+    .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+    .build();
+
+FlashApp.create(8080)
+    .install(new JacksonExtension(mapper));
+```
+
+## Scope usage
+
+`autoJson()` works the same at scope level:
+
+```java
+JacksonExtension jackson = new JacksonExtension();
+
+app.mount("/api", api -> {
+    api.use(jackson.autoJson());
+    api.get("/health", (req, res) -> Map.of("ok", true));
+});
+```
+
+If you need to pull it from context, `JacksonMiddleware` is also provided as a service
+after the app boots (same lifecycle model as other extension-provided services).
+
+## Notes
+
+- Install order is irrelevant (Flash two-phase extension lifecycle).
+- `autoJson()` and OpenAPI are intentionally decoupled.

flash-extensions/flash-ext-jackson/pom.xml

@@ -0,0 +1,82 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-jackson</artifactId>
+
+    <properties>
+        <jacoco.version>0.8.12</jacoco.version>
+    </properties>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.core</groupId>
+            <artifactId>jackson-databind</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>com.fasterxml.jackson.datatype</groupId>
+            <artifactId>jackson-datatype-jsr310</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+        </dependency>
+    </dependencies>
+
+    <build>
+        <plugins>
+            <plugin>
+                <groupId>org.jacoco</groupId>
+                <artifactId>jacoco-maven-plugin</artifactId>
+                <version>${jacoco.version}</version>
+                <executions>
+                    <execution>
+                        <id>jacoco-prepare-agent</id>
+                        <goals>
+                            <goal>prepare-agent</goal>
+                        </goals>
+                    </execution>
+                    <execution>
+                        <id>jacoco-report-and-check</id>
+                        <phase>verify</phase>
+                        <goals>
+                            <goal>report</goal>
+                            <goal>check</goal>
+                        </goals>
+                        <configuration>
+                            <rules>
+                                <rule>
+                                    <element>BUNDLE</element>
+                                    <limits>
+                                        <limit>
+                                            <counter>LINE</counter>
+                                            <value>COVEREDRATIO</value>
+                                            <minimum>0.80</minimum>
+                                        </limit>
+                                    </limits>
+                                </rule>
+                            </rules>
+                        </configuration>
+                    </execution>
+                </executions>
+            </plugin>
+        </plugins>
+    </build>
+
+</project>

flash-extensions/flash-ext-jackson/src/main/java/dev/relism/flash/ext/jackson/JacksonExtension.java

@@ -0,0 +1,94 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import com.fasterxml.jackson.databind.SerializationFeature;
+import com.fasterxml.jackson.databind.json.JsonMapper;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.extension.FlashRegistrar;
+import dev.relism.flash.extension.FlashExtension;
+import dev.relism.flash.routing.Middleware;
+
+/**
+ * Registers JSON support into the Flash extension layer.
+ *
+ * <p>Exposes a {@link Json} utility instance in the {@link FlashContext} under
+ * {@code Json.class}. Any handler or extension can retrieve it via {@code ctx.require(Json.class)}
+ * inside {@code onInit()} (class-based) or from a {@link FlashContext#onReady(Runnable)}
+ * callback (extensions).
+ *
+ * <p>The raw {@link ObjectMapper} is also registered under {@code ObjectMapper.class}
+ * for extensions that need direct mapper access (e.g. OpenAPI schema generation).
+ *
+ * <p>{@link JacksonMiddleware} is provided under {@code JacksonMiddleware.class} and
+ * exposes opinionated JSON auto-marshalling middleware via {@link JacksonMiddleware#autoJson()}.
+ *
+ * <h3>Usage — composition (preferred)</h3>
+ * <pre>{@code
+ * public class MyHandler extends RequestHandler {
+ *     private Json json;
+ *
+ *     @Override protected void onInit() {
+ *         json = require(Json.class);
+ *     }
+ *
+ *     public Object handle(Request req, Response res) throws Exception {
+ *         MyDto dto = json.body(req, MyDto.class);
+ *         return json.write(res, 201, dto);
+ *     }
+ * }
+ * }</pre>
+ *
+ * <h3>Custom mapper</h3>
+ * <pre>{@code
+ * ObjectMapper mapper = JsonMapper.builder()
+ *         .addModule(new JavaTimeModule())
+ *         .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+ *         .build();
+ *
+ * FlashApp.create(8080)
+ *         .install(new JacksonExtension(mapper));
+ * }</pre>
+ */
+public class JacksonExtension implements FlashExtension {
+
+    private final ObjectMapper mapper;
+    private final JacksonMiddleware middleware;
+
+    /**
+     * Installs with an opinionated default {@link JsonMapper}:
+     * auto-discovers modules on classpath (e.g. Java Time) and writes dates as ISO strings.
+     */
+    public JacksonExtension() {
+        this(JsonMapper.builder()
+                .findAndAddModules()
+                .disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS)
+                .build());
+    }
+
+    /** Installs with a fully configured custom {@link ObjectMapper}. */
+    public JacksonExtension(ObjectMapper mapper) {
+        this.mapper = mapper;
+        this.middleware = new JacksonMiddleware(mapper);
+    }
+
+    /**
+     * Opinionated outbound JSON middleware factory.
+     *
+     * <p>Use for app/scope-level registration:
+     * <pre>{@code
+     * JacksonExtension jackson = new JacksonExtension();
+     * app.install(jackson).use(jackson.autoJson());
+     * }</pre>
+     */
+    public Middleware autoJson() {
+        return middleware.autoJson();
+    }
+
+    @Override
+    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
+        Json json = new Json(mapper);
+        ctx.provide(Json.class,               json);
+        ctx.provide(ObjectMapper.class,       mapper);
+        ctx.provide(JacksonMiddleware.class,  middleware);
+    }
+}

flash-extensions/flash-ext-jackson/src/main/java/dev/relism/flash/ext/jackson/JacksonMiddleware.java

@@ -0,0 +1,62 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.Middleware;
+
+/**
+ * Outbound JSON marshalling middleware for class-based and lambda routes.
+ *
+ * <p>{@link #autoJson()} marshals any non-body-native return value to JSON bytes,
+ * writes {@code Content-Type: application/json}, and returns {@code byte[]} so
+ * the Flash write path stays direct.
+ *
+ * <p>Pass-through return types:
+ * <ul>
+ *   <li>{@code null}</li>
+ *   <li>{@link Response}</li>
+ *   <li>{@code byte[]}</li>
+ *   <li>{@link String}</li>
+ *   <li>{@link CharSequence}</li>
+ * </ul>
+ */
+public final class JacksonMiddleware {
+
+    private final ObjectMapper mapper;
+
+    JacksonMiddleware(ObjectMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    /**
+     * Automatic JSON marshalling policy.
+     *
+     * <p>For non-pass-through return values, serializes with Jackson directly to
+     * {@code byte[]} and sets response content type to JSON.
+     *
+     * @throws IllegalStateException when serialization fails
+     */
+    public Middleware autoJson() {
+        return next -> (req, res) -> {
+            Object out = next.handle(req, res);
+            if (isPassThrough(out)) return out;
+
+            res.type(ContentType.JSON);
+            try {
+                return mapper.writeValueAsBytes(out);
+            } catch (JsonProcessingException e) {
+                throw new IllegalStateException(
+                        "Failed to serialize handler result as JSON: " + out.getClass().getName(), e);
+            }
+        };
+    }
+
+    private static boolean isPassThrough(Object out) {
+        return out == null
+                || out instanceof Response
+                || out instanceof byte[]
+                || out instanceof CharSequence;
+    }
+}

flash-extensions/flash-ext-jackson/src/main/java/dev/relism/flash/ext/jackson/Json.java

@@ -0,0 +1,117 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.exceptions.HttpException;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.Response;
+
+/**
+ * Thread-safe JSON toolbox. Single point of access for all JSON I/O operations
+ * within a Flash application.
+ *
+ * <p>Retrieve once at boot time via {@code require(Json.class)} inside
+ * {@code onInit()}, cache in a private field, and call on the hot path
+ * with zero lookup or allocation overhead:
+ *
+ * <pre>{@code
+ * @Route(method = HttpMethod.POST, path = "/api/items")
+ * public class CreateItemHandler extends RequestHandler {
+ *
+ *     private Json json;
+ *
+ *     @Override
+ *     protected void onInit() {
+ *         json = require(Json.class);
+ *     }
+ *
+ *     public Object handle(Request req, Response res) throws Exception {
+ *         CreateItemRequest body = json.body(req, CreateItemRequest.class);
+ *         return json.write(res, itemService.create(body));
+ *     }
+ * }
+ * }</pre>
+ *
+ * <p>The underlying {@link ObjectMapper} is shared across all handlers in the same
+ * scope (one instance per app / per child scope). Jackson's {@code ObjectMapper}
+ * is fully thread-safe after configuration — no synchronization is needed.
+ *
+ * <p>Install via {@link JacksonExtension} before calling {@code scan()} or
+ * {@code register()}.
+ */
+public final class Json {
+
+    private final ObjectMapper mapper;
+
+    /** Package-private — constructed exclusively by {@link JacksonExtension}. */
+    Json(ObjectMapper mapper) {
+        this.mapper = mapper;
+    }
+
+    // ── Input ─────────────────────────────────────────────────────────────────
+
+    /**
+     * Deserializes the full request body into an instance of {@code type}.
+     *
+     * <p>Reads {@code req.body().bytes()} in one shot. For streaming bodies
+     * use {@link #bodyFrom(Request, Class)} instead.
+     *
+     * @throws HttpException 400 if the body cannot be parsed as {@code type}
+     */
+    public <T> T body(Request req, Class<T> type) throws Exception {
+        try {
+            return mapper.readValue(req.body().bytes(), type);
+        } catch (JsonProcessingException e) {
+            throw HttpException.badRequest("Invalid request body: " + e.getOriginalMessage());
+        }
+    }
+
+    /**
+     * Deserializes the request body via the raw {@link java.io.InputStream},
+     * avoiding the intermediate {@code byte[]} allocation. Prefer this for
+     * large bodies or when allocation budget is tight.
+     *
+     * @throws HttpException 400 on parse failure
+     */
+    public <T> T bodyFrom(Request req, Class<T> type) throws Exception {
+        try {
+            return mapper.readValue(req.body().stream(), type);
+        } catch (JsonProcessingException e) {
+            throw HttpException.badRequest("Invalid request body: " + e.getOriginalMessage());
+        }
+    }
+
+    // ── Output ────────────────────────────────────────────────────────────────
+
+    /**
+     * Serializes {@code obj} to a JSON string and sets
+     * {@code Content-Type: application/json} on the response.
+     *
+     * <p>The returned string is used as the response body by the Flash runtime.
+     */
+    public String write(Response res, Object obj) throws Exception {
+        res.type(ContentType.JSON);
+        return mapper.writeValueAsString(obj);
+    }
+
+    /**
+     * Like {@link #write} but applies a Jackson {@code @JsonView} filter,
+     * restricting serialization to fields visible under {@code view}.
+     */
+    public String writeView(Response res, Object obj, Class<?> view) throws Exception {
+        res.type(ContentType.JSON);
+        return mapper.writerWithView(view).writeValueAsString(obj);
+    }
+
+    // ── Escape hatch ──────────────────────────────────────────────────────────
+
+    /**
+     * Returns the underlying {@link ObjectMapper} for advanced operations
+     * (custom serialization, schema generation, etc.) not covered by the
+     * methods above.
+     */
+    public ObjectMapper mapper() {
+        return mapper;
+    }
+}

flash-extensions/flash-ext-jackson/src/test/java/dev/relism/flash/ext/jackson/JacksonExtensionTest.java

@@ -0,0 +1,62 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.models.SimpleHandler;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestHandler;
+import dev.relism.flash.models.Response;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JacksonExtensionTest {
+
+    @Test
+    void configure_registers_json_mapper_and_middleware() {
+        FlashContext ctx = new FlashContext();
+        ObjectMapper mapper = new ObjectMapper();
+        JacksonExtension ext = new JacksonExtension(mapper);
+
+        ext.configure(null, ctx);
+        ctx.complete();
+
+        assertNotNull(ctx.require(Json.class));
+        assertNotNull(ctx.require(JacksonMiddleware.class));
+        assertSame(mapper, ctx.require(ObjectMapper.class));
+    }
+
+    @Test
+    void autoJson_factory_delegates_to_middleware_policy() throws Exception {
+        ObjectMapper mapper = new ObjectMapper();
+        JacksonExtension ext = new JacksonExtension(mapper);
+        RequestHandler next = new RequestHandler() {
+            @Override
+            public Object handle(Request request, Response response) {
+                return new Payload("ok");
+            }
+        };
+        RequestHandler wrapped = new RequestHandler() {
+            private final SimpleHandler.FunctionalHandler delegate = ext.autoJson().wrap(next);
+
+            @Override
+            public Object handle(Request request, Response response) throws Exception {
+                return delegate.handle(request, response);
+            }
+        };
+
+        Response res = new Response(200, ContentType.TEXT_PLAIN);
+        Object out = wrapped.handle(null, res);
+
+        assertTrue(out instanceof byte[]);
+        assertEquals("application/json", new String(res.getContentType(), StandardCharsets.UTF_8));
+    }
+
+    private record Payload(String status) {}
+}

flash-extensions/flash-ext-jackson/src/test/java/dev/relism/flash/ext/jackson/JacksonMiddlewareTest.java

@@ -0,0 +1,90 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.models.SimpleHandler;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestHandler;
+import dev.relism.flash.models.Response;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertInstanceOf;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JacksonMiddlewareTest {
+
+    private static final Request REQ = null;
+
+    @Test
+    void autoJson_marshalsPojo_toJsonBytes_and_setsJsonContentType() throws Exception {
+        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+        RequestHandler wrapped = wrap(mw, new UserDto("u1", "alice"));
+        Response res = new Response(200, ContentType.TEXT_PLAIN);
+
+        Object out = wrapped.handle(REQ, res);
+
+        assertInstanceOf(byte[].class, out);
+        assertEquals("application/json", new String(res.getContentType(), StandardCharsets.UTF_8));
+        assertEquals("{\"id\":\"u1\",\"name\":\"alice\"}", new String((byte[]) out, StandardCharsets.UTF_8));
+    }
+
+    @Test
+    void autoJson_passThrough_for_response_string_charSequence_bytes_and_null() throws Exception {
+        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+
+        Response payloadResponse = new Response(201, ContentType.TEXT_PLAIN).body("ok");
+        RequestHandler wrappedResponse = wrap(mw, payloadResponse);
+        Response res = new Response(200, ContentType.TEXT_PLAIN);
+        assertSame(payloadResponse, wrappedResponse.handle(REQ, res));
+
+        String s = "hello";
+        assertSame(s, wrap(mw, s).handle(REQ, res));
+
+        CharSequence cs = new StringBuilder("hello-cs");
+        assertSame(cs, wrap(mw, cs).handle(REQ, res));
+
+        byte[] bytes = new byte[]{1, 2, 3};
+        assertSame(bytes, wrap(mw, bytes).handle(REQ, res));
+
+        assertSame(null, wrap(mw, null).handle(REQ, res));
+    }
+
+    @Test
+    void autoJson_wraps_serialization_errors_as_illegal_state() {
+        JacksonMiddleware mw = new JacksonMiddleware(new ObjectMapper());
+        RequestHandler wrapped = wrap(mw, new CyclicDto());
+        Response res = new Response(200, ContentType.TEXT_PLAIN);
+
+        IllegalStateException ex = assertThrows(IllegalStateException.class, () -> wrapped.handle(REQ, res));
+        assertEquals("application/json", new String(res.getContentType(), StandardCharsets.UTF_8));
+        assertTrue(ex.getMessage().startsWith("Failed to serialize handler result as JSON:"));
+    }
+
+    private static RequestHandler wrap(JacksonMiddleware mw, Object fixedReturn) {
+        RequestHandler next = new RequestHandler() {
+            @Override
+            public Object handle(Request request, Response response) {
+                return fixedReturn;
+            }
+        };
+        return new RequestHandler() {
+            private final SimpleHandler.FunctionalHandler delegate = mw.autoJson().wrap(next);
+
+            @Override
+            public Object handle(Request request, Response response) throws Exception {
+                return delegate.handle(request, response);
+            }
+        };
+    }
+
+    private record UserDto(String id, String name) {}
+
+    private static final class CyclicDto {
+        CyclicDto self = this;
+    }
+}

flash-extensions/flash-ext-jackson/src/test/java/dev/relism/flash/ext/jackson/JsonTest.java

@@ -0,0 +1,116 @@
+package dev.relism.flash.ext.jackson;
+
+import com.fasterxml.jackson.annotation.JsonView;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import dev.relism.flash.exceptions.HttpException;
+import dev.relism.flash.http.ContentType;
+import dev.relism.flash.http.HttpMethod;
+import dev.relism.flash.models.HeaderMap;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestLine;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.routers.fastpathrouter.FastPathViews;
+import org.junit.jupiter.api.Test;
+
+import java.nio.charset.StandardCharsets;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertSame;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JsonTest {
+
+    @Test
+    void body_parses_valid_json_and_maps_bad_payload_to_http_400() throws Exception {
+        Json json = new Json(new ObjectMapper());
+
+        Request ok = request("{\"id\":\"u1\",\"name\":\"alice\"}");
+        UserDto dto = json.body(ok, UserDto.class);
+        assertEquals("u1", dto.id);
+        assertEquals("alice", dto.name);
+
+        Request bad = request("not-json");
+        HttpException ex = assertThrows(HttpException.class, () -> json.body(bad, UserDto.class));
+        assertEquals(400, ex.status());
+        assertTrue(ex.getMessage().startsWith("Invalid request body:"));
+    }
+
+    @Test
+    void bodyFrom_parses_stream_and_maps_bad_payload_to_http_400() throws Exception {
+        Json json = new Json(new ObjectMapper());
+
+        Request ok = request("{\"id\":\"u2\",\"name\":\"bob\"}");
+        UserDto dto = json.bodyFrom(ok, UserDto.class);
+        assertEquals("u2", dto.id);
+        assertEquals("bob", dto.name);
+
+        Request bad = request("[");
+        HttpException ex = assertThrows(HttpException.class, () -> json.bodyFrom(bad, UserDto.class));
+        assertEquals(400, ex.status());
+    }
+
+    @Test
+    void write_and_writeView_set_content_type_and_render_expected_payload() throws Exception {
+        Json json = new Json(new ObjectMapper());
+        Response res = new Response(200, ContentType.TEXT_PLAIN);
+
+        String payload = json.write(res, new UserDto("u3", "carol"));
+        assertEquals("application/json", new String(res.getContentType(), StandardCharsets.UTF_8));
+        assertEquals("{\"id\":\"u3\",\"name\":\"carol\"}", payload);
+
+        Response viewRes = new Response(200, ContentType.TEXT_PLAIN);
+        String viewed = json.writeView(viewRes, new ViewDto("u4", "hidden"), PublicView.class);
+        assertEquals("application/json", new String(viewRes.getContentType(), StandardCharsets.UTF_8));
+        assertEquals("{\"id\":\"u4\"}", viewed);
+    }
+
+    @Test
+    void mapper_returns_underlying_object_mapper_instance() {
+        ObjectMapper mapper = new ObjectMapper();
+        Json json = new Json(mapper);
+        assertSame(mapper, json.mapper());
+    }
+
+    private static Request request(String body) {
+        return request(body.getBytes(StandardCharsets.UTF_8));
+    }
+
+    private static Request request(byte[] body) {
+        RequestLine line = new RequestLine(
+                HttpMethod.POST,
+                new FastPathViews.StringByteView("/json"),
+                null,
+                new FastPathViews.StringByteView("HTTP/1.1"),
+                new HeaderMap()
+        );
+        return new Request(line, body);
+    }
+
+    private static final class UserDto {
+        public String id;
+        public String name;
+
+        public UserDto() {}
+
+        private UserDto(String id, String name) {
+            this.id = id;
+            this.name = name;
+        }
+    }
+
+    private interface PublicView {}
+    private interface InternalView {}
+
+    private static final class ViewDto {
+        @JsonView(PublicView.class)
+        public String id;
+        @JsonView(InternalView.class)
+        public String secret;
+
+        private ViewDto(String id, String secret) {
+            this.id = id;
+            this.secret = secret;
+        }
+    }
+}

flash-extensions/flash-ext-limiter/docs/README.md

@@ -0,0 +1,65 @@
+# flash-ext-limiter
+
+Rate limiting for the Flash HTTP server. Zero-allocation hot-path, lock-free counters,
+pluggable key resolvers, and two built-in algorithms.
+
+## What it provides
+
+| Component | Description |
+|---|---|
+| `@Limit` | Annotation for class-based handlers — processed once at boot |
+| `Guard` | Programmatic middleware factory for lambda routes |
+| `LimiterConfig` | Resolver registry — map string names to key-extraction lambdas |
+| `FIXED_WINDOW` | Clock-aligned counter reset; minimal memory |
+| `TOKEN_BUCKET` | Continuous refill; absorbs bursts smoothly |
+
+## Dependency
+
+```xml
+<dependency>
+    <groupId>dev.relism</groupId>
+    <artifactId>flash-ext-limiter</artifactId>
+    <version>1.0-SNAPSHOT</version>
+</dependency>
+```
+
+## Quick start
+
+```java
+// Default install — only the built-in "ip" resolver available
+FlashApp.create(8080)
+    .install(new LimiterExtension())
+    .scan("com.example.handlers");
+```
+
+```java
+// With custom resolvers
+LimiterConfig conf = new LimiterConfig()
+    .registerResolver("auth_user", req ->
+        ClaimsHolder.exists() ? ClaimsHolder.user().sub() : "anonymous");
+
+FlashApp.create(8080)
+    .install(new LimiterExtension(conf))
+    .scan("com.example.handlers");
+```
+
+## Installation order
+
+Install `LimiterExtension` **before** authentication extensions. Rate-limit checks
+then short-circuit over-limit requests before expensive token validation runs.
+
+```java
+app.install(new LimiterExtension(conf))   // ← first
+   .install(new OidcExtension(oidcConf))  // ← second
+   .scan("com.example");
+```
+
+## Docs
+
+| File | Contents |
+|---|---|
+| [key-resolvers.md](key-resolvers.md) | Resolver registration, built-in defaults, custom logic |
+| [annotation.md](annotation.md) | `@Limit` reference — all fields and examples |
+| [guard.md](guard.md) | `Guard` for lambda routes — all overloads |
+| [strategies.md](strategies.md) | `FIXED_WINDOW` vs `TOKEN_BUCKET` — algorithm reference |
+| [http-headers.md](http-headers.md) | HTTP compliance — headers and 429 response |

flash-extensions/flash-ext-limiter/docs/annotation.md

@@ -0,0 +1,135 @@
+# @Limit annotation
+
+Applies a rate limit to a **class-based** `RequestHandler`. The annotation is read once
+per handler class at boot by the `LimiterExtension` annotation processor — zero overhead
+at request time.
+
+## Declaration
+
+```java
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Limit {
+    String      key()        default "ip";
+    int         requests();
+    long        window();
+    TimeUnit    windowUnit() default TimeUnit.SECONDS;
+    LimitStrategy strategy() default LimitStrategy.FIXED_WINDOW;
+}
+```
+
+## Fields
+
+| Field | Type | Default | Description |
+|---|---|---|---|
+| `key` | `String` | `"ip"` | Name of the key resolver registered in `LimiterConfig` |
+| `requests` | `int` | — | Maximum requests allowed per window (required) |
+| `window` | `long` | — | Window duration in `windowUnit` units (required) |
+| `windowUnit` | `TimeUnit` | `SECONDS` | Time unit for `window` |
+| `strategy` | `LimitStrategy` | `FIXED_WINDOW` | Rate-limit algorithm |
+
+## Basic usage
+
+### 100 requests per second per IP (default)
+
+```java
+@Route(method = HttpMethod.GET, path = "/api/search")
+@Limit(requests = 100, window = 1)
+public class SearchHandler extends RequestHandler {
+    public Object handle(Request req, Response res) {
+        return searchService.query(req.query("q"));
+    }
+}
+```
+
+### 20 requests per minute per authenticated user
+
+```java
+@Route(method = HttpMethod.POST, path = "/api/report")
+@Limit(key = "auth_user", requests = 20, window = 1, windowUnit = TimeUnit.MINUTES)
+@Authenticated
+public class ReportHandler extends RequestHandler {
+    public Object handle(Request req, Response res) { ... }
+}
+```
+
+Order of annotation processors: register `LimiterExtension` before `OidcExtension`
+so the rate-limit middleware wraps the outer layer of the chain and fires before auth.
+
+### Token bucket — absorb bursts
+
+```java
+@Route(method = HttpMethod.POST, path = "/api/upload")
+@Limit(
+    key        = "api_key",
+    requests   = 50,
+    window     = 1,
+    windowUnit = TimeUnit.MINUTES,
+    strategy   = LimitStrategy.TOKEN_BUCKET
+)
+public class UploadHandler extends RequestHandler { ... }
+```
+
+### Large window — 1000 requests per hour
+
+```java
+@Route(method = HttpMethod.GET, path = "/api/export")
+@Limit(requests = 1000, window = 1, windowUnit = TimeUnit.HOURS)
+public class ExportHandler extends RequestHandler { ... }
+```
+
+### Strict per-second limit on a public endpoint
+
+```java
+@Route(method = HttpMethod.GET, path = "/api/prices")
+@Limit(requests = 10, window = 1, windowUnit = TimeUnit.SECONDS)
+public class PriceHandler extends RequestHandler { ... }
+```
+
+## Combining @Limit with other annotations
+
+`@Limit` composes naturally with `@Authenticated`, `@RolesAllowed`, and `@ApiOperation`.
+Each annotation is processed by its own processor; Flash collects all middleware and
+composes them in processor registration order.
+
+When `flash-ext-openapi` is installed, `@Limit` also contributes OpenAPI response
+headers (`X-RateLimit-*`) and `Retry-After` on `429` automatically.
+
+```java
+@Route(method = HttpMethod.DELETE, path = "/admin/users/{id}")
+@Limit(key = "auth_user", requests = 5, window = 1, windowUnit = TimeUnit.MINUTES)
+@RolesAllowed("admin")
+@ApiOperation(summary = "Delete a user", tags = "admin")
+public class DeleteUserHandler extends RequestHandler { ... }
+```
+
+Execution chain (outermost → handler):
+`LimiterMiddleware → OidcRolesMiddleware → DeleteUserHandler`
+
+## Fail-fast at boot
+
+If `key` names a resolver not registered in `LimiterConfig`, the server refuses to start:
+
+```
+dev.relism.exceptions.InitializationException:
+  Rate-limit resolver "auth_user" is not registered.
+  Call LimiterConfig.registerResolver("auth_user", req -> ...) before install.
+```
+
+There is no silent fallback — a misconfigured rate limit is treated as a hard error.
+
+## What happens on violation
+
+```
+HTTP/1.1 429 Too Many Requests
+X-RateLimit-Limit:     100
+X-RateLimit-Remaining: 0
+X-RateLimit-Reset:     1711750860
+Retry-After:           1
+Content-Type:          text/plain
+
+Too Many Requests
+```
+
+The handler body is never invoked. See [http-headers.md](http-headers.md) for the full
+header reference.

flash-extensions/flash-ext-limiter/docs/guard.md

@@ -0,0 +1,144 @@
+# Guard — programmatic rate limiting for lambda routes
+
+`Guard` is the rate-limit API for lambda (inline) route registrations. It produces
+a `Middleware` that is composed once at route-wiring time — the resolver lambda is
+captured directly into the closure, with no map lookup on the request hot-path.
+
+## Obtaining Guard
+
+`Guard` is provided in the `FlashContext` after `LimiterExtension` is installed:
+
+```java
+Guard guard = app.ctx().require(Guard.class);
+```
+
+Or inside another extension:
+
+```java
+public void install(FlashRegistrar app, FlashContext ctx) {
+    Guard guard = ctx.require(Guard.class);
+    // ...
+}
+```
+
+## API
+
+```java
+// Fixed window (default strategy)
+Middleware limit(String resolverKey, int requests, long window, TimeUnit unit)
+
+// Explicit strategy
+Middleware limit(String resolverKey, int requests, long window, TimeUnit unit, LimitStrategy strategy)
+```
+
+Both overloads:
+- Resolve the named key lambda **once** at call time (fail-fast if unknown).
+- Return a stateless `Middleware` whose closure captures the lambda and `LimitConfig` directly.
+- Share the `BucketStore` with all other rules registered through this `LimiterExtension` instance.
+
+## Examples
+
+### Simple per-IP limit on a lambda route
+
+```java
+Guard guard = app.ctx().require(Guard.class);
+
+app.get("/api/search", (req, res) -> searchService.query(req.query("q")))
+   .with(guard.limit("ip", 100, 1, TimeUnit.SECONDS));
+```
+
+### Per authenticated user — token bucket
+
+```java
+app.post("/api/export", (req, res) -> exportService.run(req))
+   .with(guard.limit("auth_user", 10, 1, TimeUnit.MINUTES, LimitStrategy.TOKEN_BUCKET));
+```
+
+### Chaining with other middleware
+
+`Guard.limit(...)` returns a plain `Middleware`, so it composes with `Middleware.of()`
+and `.andThen()` exactly like any other middleware:
+
+```java
+Middleware secured = Middleware.of(
+    guard.limit("ip", 200, 1, TimeUnit.SECONDS),   // ← outermost: runs first
+    oidc.protect()
+);
+
+app.get("/dashboard", handler).with(secured);
+```
+
+Or with `.andThen()` for two middlewares:
+
+```java
+app.get("/dashboard", handler)
+   .with(guard.limit("ip", 200, 1, TimeUnit.SECONDS).andThen(oidc.protect()));
+```
+
+### Different limits on the same path by method
+
+```java
+// Read: 500/s; Write: 20/s
+app.get("/api/items",  readHandler) .with(guard.limit("ip", 500, 1, TimeUnit.SECONDS));
+app.post("/api/items", writeHandler).with(guard.limit("ip",  20, 1, TimeUnit.SECONDS));
+```
+
+Each `.with(guard.limit(...))` call creates an independent bucket store key namespace —
+GET and POST requests to `/api/items` share the same IP bucket only if you share the same
+`Middleware` instance. Using two `guard.limit(...)` calls creates **two independent buckets**.
+
+### Reusing a middleware instance across routes
+
+To share a single bucket pool across multiple routes (treating them as one combined limit):
+
+```java
+Middleware sharedIpLimit = guard.limit("ip", 1000, 1, TimeUnit.MINUTES);
+
+app.get("/api/items",      handler1).with(sharedIpLimit);
+app.get("/api/items/{id}", handler2).with(sharedIpLimit);
+app.post("/api/items",     handler3).with(sharedIpLimit);
+```
+
+All three routes now draw from the same per-IP bucket — 1000 combined requests per minute.
+
+### Inside an extension
+
+```java
+public class MyApiExtension implements FlashExtension {
+    public void install(FlashRegistrar app, FlashContext ctx) {
+        Guard guard = ctx.require(Guard.class);  // LimiterExtension must be installed first
+
+        Middleware ipLimit = guard.limit("ip", 60, 1, TimeUnit.SECONDS);
+
+        app.get("/api/status",  statusHandler) .with(ipLimit);
+        app.get("/api/metrics", metricsHandler).with(ipLimit);
+    }
+}
+```
+
+### Large window
+
+```java
+app.get("/api/export", exportHandler)
+   .with(guard.limit("api_key", 50, 24, TimeUnit.HOURS));
+```
+
+## Fail-fast
+
+If the resolver name is not registered, `guard.limit(...)` throws immediately
+(at wiring time, not at request time):
+
+```
+InitializationException: Rate-limit resolver "auth_user" is not registered.
+```
+
+## Comparison: Guard vs @Limit
+
+| | `@Limit` | `Guard.limit(...)` |
+|---|---|---|
+| Route style | Class-based `RequestHandler` | Lambda `(req, res) -> ...` |
+| Configuration | Annotation fields | Method arguments |
+| Where resolved | `AnnotationProcessor` at `scan()` | `guard.limit(...)` call at wiring |
+| Hot-path overhead | Zero | Zero |
+| Fail-fast | Yes | Yes |
+| Composable with `Middleware.of()` | Via annotation processor order | Yes, directly |

flash-extensions/flash-ext-limiter/docs/http-headers.md

@@ -0,0 +1,128 @@
+# HTTP headers and 429 response
+
+The extension injects standard rate-limit headers on **every** request — both allowed
+and rejected. Clients can use these headers to implement back-off logic without waiting
+for a 429.
+
+## Response headers
+
+| Header | Type | Description |
+|---|---|---|
+| `X-RateLimit-Limit` | integer | Maximum requests allowed in the current window |
+| `X-RateLimit-Remaining` | integer | Requests remaining in the current window (≥ 0) |
+| `X-RateLimit-Reset` | Unix timestamp (s) | When the quota resets or the next token arrives |
+| `Retry-After` | seconds | **Only on 429** — how long to wait before retrying (≥ 1) |
+
+### Example — allowed request
+
+```
+HTTP/1.1 200 OK
+X-RateLimit-Limit:     100
+X-RateLimit-Remaining: 73
+X-RateLimit-Reset:     1711750860
+Content-Type: application/json
+```
+
+### Example — rejected request (429)
+
+```
+HTTP/1.1 429 Too Many Requests
+X-RateLimit-Limit:     100
+X-RateLimit-Remaining: 0
+X-RateLimit-Reset:     1711750860
+Retry-After:           1
+Content-Type: text/plain
+
+Too Many Requests
+```
+
+## Header semantics by strategy
+
+### FIXED_WINDOW
+
+| Header | Value |
+|---|---|
+| `X-RateLimit-Reset` | Unix timestamp of the **next window start** (aligned to clock) |
+| `Retry-After` | Seconds until `X-RateLimit-Reset` (minimum 1) |
+
+At a 1-second window boundary `Retry-After` will typically be `1`.
+
+### TOKEN_BUCKET
+
+| Header | Value |
+|---|---|
+| `X-RateLimit-Remaining` | Current token count (may increase between requests due to refill) |
+| `X-RateLimit-Reset` | Estimated Unix timestamp when the **next token arrives** |
+| `Retry-After` | Milliseconds-precise estimate converted to seconds (minimum 1) |
+
+Because the token bucket refills continuously, `X-RateLimit-Reset` is a near-future
+timestamp rather than an aligned window boundary.
+
+## Retry-After precision
+
+`Retry-After` is computed as:
+
+```
+retryAfter = max(1, X-RateLimit-Reset - currentTimeSeconds)
+```
+
+The minimum value is always `1` second — RFC 7231 discourages `Retry-After: 0` as it
+encourages instant retry loops.
+
+## Client-side back-off example (Java)
+
+```java
+HttpResponse<String> res = client.send(request, BodyHandlers.ofString());
+
+if (res.statusCode() == 429) {
+    String retryAfter = res.headers().firstValue("Retry-After").orElse("1");
+    long waitMs = Long.parseLong(retryAfter) * 1000L;
+    Thread.sleep(waitMs);
+    // retry...
+}
+```
+
+## Client-side back-off example (JavaScript fetch)
+
+```js
+const res = await fetch('/api/search?q=flash');
+
+if (res.status === 429) {
+    const retryAfter = parseInt(res.headers.get('Retry-After') ?? '1', 10);
+    await new Promise(r => setTimeout(r, retryAfter * 1000));
+    // retry...
+}
+```
+
+## Monitoring / alerting
+
+`X-RateLimit-Remaining` can be scraped by a metrics agent to track approaching limits
+before they hit 429:
+
+- `remaining / limit < 0.1` → warning (less than 10% quota left)
+- `status == 429` → rate-limit violation counter increment
+
+If `flash-ext-limiter` is used together with a future metrics extension, the 429 rate
+per resolver key is a natural signal for abuse detection or auto-scaling.
+
+## Header injection timing
+
+Headers are injected **before** calling `next.handle(req, res)` on allowed requests,
+and **instead of** calling it on rejected requests. This means:
+
+- Handlers cannot accidentally overwrite `X-RateLimit-*` headers (they are set first,
+  but handlers that call `res.header(...)` with the same name will add a second value —
+  avoid this by not setting these headers manually).
+- On 429, the handler body is never executed — no side effects occur.
+
+## Integration with Swagger UI (flash-ext-openapi)
+
+When `flash-ext-openapi` is installed, handlers annotated with `@Limit` automatically
+contribute rate-limit response headers to generated OpenAPI responses:
+
+- `X-RateLimit-Limit`
+- `X-RateLimit-Remaining`
+- `X-RateLimit-Reset`
+- `Retry-After` on `429`
+
+If `429` is not manually declared, OpenAPI auto-adds `429 Too Many Requests`.

flash-extensions/flash-ext-limiter/docs/key-resolvers.md

@@ -0,0 +1,143 @@
+# Key Resolvers
+
+A **key resolver** is a lambda `Request → String` that extracts the partition key used
+to identify who a rate limit applies to. Each unique key value gets its own independent
+bucket — so `"ip"` limits per client address, `"auth_user"` limits per logged-in user, etc.
+
+## Built-in resolver: `"ip"`
+
+Always present. Cannot be removed; can be overridden with `registerResolver("ip", ...)`.
+
+Resolution order:
+1. `X-Forwarded-For` header — first address in the comma-separated list (client behind proxy)
+2. `X-Real-IP` header — single forwarded IP (nginx `proxy_set_header X-Real-IP`)
+3. `req.remoteAddress().getAddress().getHostAddress()` — direct socket address, zero allocation
+   (the `InetSocketAddress` already exists from `ServerSocket.accept()`; only `getHostAddress()`
+   allocates a String, and only when the first two headers are absent)
+4. `"unknown"` — only if `remoteAddress()` is null (test-constructed requests)
+
+```java
+// Override the built-in "ip" resolver to trust only the last hop in X-Forwarded-For
+conf.registerResolver("ip", req -> {
+    String xff = req.header("X-Forwarded-For");
+    if (xff != null) {
+        String[] parts = xff.split(",");
+        return parts[parts.length - 1].strip();   // last = most recent proxy
+    }
+    return req.header("X-Real-IP") != null ? req.header("X-Real-IP").strip() : "unknown";
+});
+```
+
+
+## Registering custom resolvers
+
+```java
+LimiterConfig conf = new LimiterConfig();
+```
+
+### By authenticated user (OIDC / ClaimsHolder)
+
+```java
+conf.registerResolver("auth_user", req ->
+    ClaimsHolder.exists() ? ClaimsHolder.user().sub() : "anonymous");
+```
+
+Requests from unauthenticated users share the `"anonymous"` bucket. If you want
+unauthenticated requests to be unlimited, pair this resolver with `@Limit` only on
+handlers that are already protected by `@Authenticated`.
+
+### By API key header
+
+```java
+conf.registerResolver("api_key", req -> {
+    String key = req.header("X-Api-Key");
+    return key != null ? key : "none";
+});
+```
+
+### By tenant (multi-tenant SaaS)
+
+```java
+conf.registerResolver("tenant", req -> {
+    // Extract from subdomain: acme.api.example.com → "acme"
+    String host = req.header("Host");
+    if (host == null) return "unknown";
+    int dot = host.indexOf('.');
+    return dot > 0 ? host.substring(0, dot) : host;
+});
+```
+
+### By IP + path (per-endpoint per-IP)
+
+Combines two dimensions into a single key string:
+
+```java
+conf.registerResolver("ip_path", req -> {
+    String ip   = req.header("X-Forwarded-For");
+    if (ip == null) ip = "unknown";
+    int comma = ip.indexOf(',');
+    if (comma > 0) ip = ip.substring(0, comma).strip();
+    return ip + "|" + req.path();
+});
+```
+
+### Composite: role-based bucket size
+
+One resolver, two different `@Limit` thresholds on two handler classes. The resolver
+returns the same key for the same user regardless of endpoint; the limit is set per handler.
+
+```java
+conf.registerResolver("auth_user", req ->
+    ClaimsHolder.exists() ? ClaimsHolder.user().sub() : "anon");
+```
+
+```java
+@Limit(key = "auth_user", requests = 1000, window = 1)   // privileged endpoint
+public class AdminReportHandler extends RequestHandler { ... }
+
+@Limit(key = "auth_user", requests = 20,   window = 1)   // public endpoint
+public class PublicSearchHandler extends RequestHandler { ... }
+```
+
+The two handlers maintain **independent buckets** for the same user — each `@Limit`
+annotation gets its own `BucketStore`.
+
+## Resolver contract
+
+```java
+@FunctionalInterface
+public interface KeyResolver {
+    String resolve(Request req);  // must never return null; return "unknown" as fallback
+}
+```
+
+- Must not return `null` — a null key will throw `NullPointerException` inside `ConcurrentHashMap`.
+- Must be **thread-safe** — called concurrently from virtual threads.
+- Should be **fast** — it runs on every request for every rate-limited route.
+- No state should be mutated — treat `Request` as read-only.
+
+## Fail-fast validation
+
+If a `@Limit` annotation or `guard.limit(...)` call references a resolver name that was never
+registered, the server **refuses to start** with `InitializationException`:
+
+```
+InitializationException: Rate-limit resolver "auth_user" is not registered.
+Call LimiterConfig.registerResolver("auth_user", req -> ...) before install.
+```
+
+This check happens at boot time (annotation processor / Guard wiring), not at request time.
+
+## Registration API
+
+```java
+LimiterConfig conf = new LimiterConfig()
+    .registerResolver("auth_user", req -> ...)
+    .registerResolver("tenant",    req -> ...)
+    .registerResolver("api_key",   req -> ...);
+
+app.install(new LimiterExtension(conf));
+```
+
+`registerResolver` returns `this` for fluent chaining. Calling it with an existing name
+**replaces** the previous resolver — this is how you override the built-in `"ip"` resolver.

flash-extensions/flash-ext-limiter/docs/strategies.md

@@ -0,0 +1,178 @@
+# Rate-limit strategies
+
+Two algorithms are built in. Both are lock-free (CAS-only), operate on pre-allocated
+`Bucket` state, and write results into a caller-supplied `long[2]` — zero per-request allocation.
+
+## FIXED_WINDOW
+
+```java
+@Limit(strategy = LimitStrategy.FIXED_WINDOW, ...)   // default, can be omitted
+guard.limit("ip", 100, 1, TimeUnit.SECONDS)           // default
+```
+
+### How it works
+
+The request counter resets to zero at each clock-aligned window boundary.
+
+```
+ window 1         window 2         window 3
+|────────────────|────────────────|────────────────|
+ cnt: 0 1 2 … N  cnt: 0 1 2 … N  cnt: 0 1 2 … N
+```
+
+With `requests = 100, window = 1s`:
+- Requests 1–100 in a given second → allowed
+- Request 101+ in that second → 429, allowed again at second +1
+
+### Implementation
+
+All state is packed into a single `AtomicLong` (`Bucket.slot0`):
+
+```
+high 32 bits = reduced epoch  = (currentTimeMs / windowMs) & 0xFFFFFFFF
+low  32 bits = request count in the current window
+```
+
+One CAS operation per request. At a window boundary the same CAS atomically resets the
+counter to 1. No locks, no additional fields.
+
+### Burst behaviour
+
+Because the window is fixed to the clock, a burst can occur at the boundary:
+up to `N` requests at the end of window 1 followed immediately by `N` requests at the
+start of window 2 → `2N` requests in a short interval.
+
+```
+   window 1  │  window 2
+ ────────────┼────────────
+  99 100 101 │ 1  2  3  4
+             ↑ reset: 101 → 429, then 1 is allowed
+```
+
+If burst tolerance is unacceptable, use `TOKEN_BUCKET`.
+
+### When to use
+
+- Simple API rate limiting where occasional boundary bursts are acceptable.
+- Scenarios where a hard "N requests per clock second/minute" guarantee matters.
+- When you want minimal per-bucket memory (one `AtomicLong`, `Bucket.slot1` unused).
+
+---
+
+## TOKEN_BUCKET
+
+```java
+@Limit(strategy = LimitStrategy.TOKEN_BUCKET, ...)
+guard.limit("ip", 100, 1, TimeUnit.SECONDS, LimitStrategy.TOKEN_BUCKET)
+```
+
+### How it works
+
+The bucket holds up to `requests` tokens and refills at a continuous rate of
+`requests / window` tokens per millisecond. Each request consumes one token.
+A client that was idle accumulates tokens and can fire a burst, but sustained
+excess traffic drains the bucket and triggers 429s.
+
+```
+tokens
+  N ─┐           ┌──── refill slope ────┐
+     │           │                      │
+  0  └───────────┘ ←─ burst consumed ──→│
+      burst here    429s during drain   recovery
+```
+
+### Refill rate
+
+`refillPerMs = (requests × 1000) / windowMs`  (integer, minimum 1)
+
+For `requests = 100, window = 1s`:
+- Refill rate: 100 tokens/s = 1 token/10 ms
+- Max capacity: 100 tokens
+- A client idle for 500 ms accumulates 50 tokens and can fire 50 requests instantly.
+
+### Implementation
+
+- `Bucket.slot0` — current tokens × 1000 (fixed-point, avoids floating-point math)
+- `Bucket.slot1` — last-refill timestamp in ms (0 = uninitialised → bucket starts full)
+
+One CAS loop on `slot0` per request; `slot1` updated best-effort after CAS success.
+The bounded inaccuracy from the non-atomic dual update is at most a few nanoseconds —
+negligible and self-correcting for rate limiting.
+
+### Bucket starts full
+
+On the very first request, `slot1 == 0`. The strategy treats this as "one full window
+elapsed" → `currentTokens = max`. The bucket starts at capacity; no warm-up needed.
+
+### When to use
+
+- APIs where clients legitimately batch requests (analytics, bulk imports).
+- Endpoints where smooth throughput matters more than hard per-second guarantees.
+- Any scenario where `FIXED_WINDOW` boundary bursts would be problematic.
+
+---
+
+## Comparison
+
+| | `FIXED_WINDOW` | `TOKEN_BUCKET` |
+|---|---|---|
+| Algorithm | Aligned counter reset | Continuous token refill |
+| Burst handling | Allows 2× limit at boundaries | Absorbs bursts up to bucket capacity |
+| Memory per bucket | 1 × `AtomicLong` used | 2 × `AtomicLong` used |
+| Clock alignment | Yes (predictable resets) | No (smooth) |
+| Typical use case | Simple request quotas | APIs with legitimate burst patterns |
+| CAS operations per request | 1 (usually) | 1 (usually) |
+
+Both strategies use the same `Bucket` type. Both are lock-free and allocation-free after
+the bucket is first created.
+
+---
+
+## Adding a custom strategy
+
+Implement `RateLimitStrategy` and wrap it in a `LimitStrategy` enum constant:
+
+```java
+// 1. Implement the strategy
+public final class SlidingWindowStrategy implements RateLimitStrategy {
+    @Override
+    public boolean check(Bucket bucket, LimitConfig cfg, long[] out) {
+        // ... lock-free implementation using bucket.slot0 / slot1
+        return allowed;
+    }
+}
+
+// 2. Add to the enum
+public enum LimitStrategy {
+    FIXED_WINDOW { ... },
+    TOKEN_BUCKET { ... },
+    SLIDING_WINDOW {
+        @Override
+        public RateLimitStrategy create() { return new SlidingWindowStrategy(); }
+    };
+    public abstract RateLimitStrategy create();
+}
+```
+
+The new strategy is immediately available to `@Limit(strategy = LimitStrategy.SLIDING_WINDOW)`
+and `guard.limit("ip", 100, 1, SECONDS, LimitStrategy.SLIDING_WINDOW)`.
+
+### Strategy contract
+
+```java
+public interface RateLimitStrategy {
+    /**
+     * @param bucket  pre-allocated per-key state (never null)
+     * @param cfg     immutable rule config (limit, windowMs)
+     * @param out     out[0] = remaining, out[1] = reset epoch-seconds
+     * @return true = allowed, false = rejected (429)
+     */
+    boolean check(Bucket bucket, LimitConfig cfg, long[] out);
+}
+```
+
+Requirements for custom implementations:
+- **Lock-free** — use `AtomicLong.compareAndSet`; no `synchronized` or `ReentrantLock`.
+- **Stateless** — all mutable state must live in `Bucket.slot0` / `Bucket.slot1`.
+- **No allocation** — `out[]` is the only output channel; do not create objects on the hot path.
+- **Thread-safe** — called concurrently from many virtual threads.

flash-extensions/flash-ext-limiter/pom.xml

@@ -0,0 +1,35 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <modelVersion>4.0.0</modelVersion>
+
+    <parent>
+        <groupId>dev.relism</groupId>
+        <artifactId>flash-extensions</artifactId>
+        <version>2.1.0-SNAPSHOT</version>
+    </parent>
+
+    <artifactId>flash-ext-limiter</artifactId>
+
+    <dependencies>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>dev.relism</groupId>
+            <artifactId>flash-ext-openapi</artifactId>
+            <optional>true</optional>
+        </dependency>
+        <dependency>
+            <groupId>org.projectlombok</groupId>
+            <artifactId>lombok</artifactId>
+        </dependency>
+        <dependency>
+            <groupId>org.junit.jupiter</groupId>
+            <artifactId>junit-jupiter</artifactId>
+        </dependency>
+    </dependencies>
+
+</project>

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/Bucket.java

@@ -0,0 +1,24 @@
+package dev.relism.flash.ext.limiter;
+
+import java.util.concurrent.atomic.AtomicLong;
+
+/**
+ * Pre-allocated per-key rate limit state. Holds two {@link AtomicLong} slots whose
+ * semantics are strategy-specific:
+ *
+ * <ul>
+ *   <li><b>FIXED_WINDOW</b>: {@code slot0} = packed {@code (epoch << 32 | count)},
+ *       {@code slot1} unused.</li>
+ *   <li><b>SLIDING_WINDOW</b>: {@code slot0} = packed {@code (epoch << 32 | count)},
+ *       {@code slot1} = request count from the immediately preceding epoch.</li>
+ *   <li><b>TOKEN_BUCKET</b>: {@code slot0} = tokens × 1000 (scaled),
+ *       {@code slot1} = last-refill timestamp (ms since epoch).</li>
+ * </ul>
+ *
+ * <p>Buckets are created once per unique key (via {@link BucketStore}) and reused
+ * for the lifetime of the server — zero allocation on the warm path.
+ */
+public final class Bucket {
+    public final AtomicLong slot0 = new AtomicLong(0L);
+    public final AtomicLong slot1 = new AtomicLong(0L);
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/BucketStore.java

@@ -0,0 +1,28 @@
+package dev.relism.flash.ext.limiter;
+
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Thread-safe store of pre-allocated {@link Bucket} instances keyed by partition key.
+ *
+ * <p>On the warm path (key already seen), {@link #get} performs a single
+ * {@link ConcurrentHashMap} lookup — no allocation. On the cold path (new key),
+ * {@code computeIfAbsent} allocates exactly one {@link Bucket} and inserts it.
+ *
+ * <p>Buckets accumulate indefinitely; for workloads with unbounded unique keys
+ * (e.g. one-shot crawlers), consider periodic store replacement or a bounded
+ * LRU map implementation.
+ */
+public final class BucketStore {
+
+    private final ConcurrentHashMap<String, Bucket> map = new ConcurrentHashMap<>();
+
+    /**
+     * Returns the bucket for {@code key}, creating one if absent.
+     * Two threads racing on the same new key are guaranteed to receive the same bucket instance.
+     */
+    public Bucket get(String key) {
+        Bucket b = map.get(key);
+        return b != null ? b : map.computeIfAbsent(key, k -> new Bucket());
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/Guard.java

@@ -0,0 +1,69 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.exceptions.InitializationException;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.routing.Middleware;
+
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Manual rate-limit guard for lambda routes.
+ *
+ * <p>Available via {@link FlashContext}:
+ * <pre>{@code
+ * Guard guard = ctx.require(Guard.class);
+ * }</pre>
+ *
+ * <p>{@link #limit} creates a {@link Middleware} that is composed once at route registration
+ * time — the resolver lambda is captured directly from the registry (no runtime map lookup):
+ * <pre>{@code
+ * // 50 req/s per IP — fixed window (default)
+ * app.get("/api/search", handler, guard.limit("ip", 50, 1, TimeUnit.SECONDS));
+ *
+ * // 10 req/min per authenticated user — token bucket
+ * app.post("/api/export", handler, guard.limit("auth_user", 10, 1, TimeUnit.MINUTES, LimitStrategy.TOKEN_BUCKET));
+ * }</pre>
+ *
+ * <p>The resolver name is looked up once here (at wiring time, not on each request).
+ * If the name is not registered, {@link InitializationException}
+ * is thrown immediately.
+ */
+public final class Guard {
+
+    private final LimiterConfig config;
+    private final BucketStore   store;
+
+    Guard(LimiterConfig config, BucketStore store) {
+        this.config = config;
+        this.store  = store;
+    }
+
+    /**
+     * Returns a {@link Middleware} that enforces the given rate limit using
+     * {@link LimitStrategy#FIXED_WINDOW}.
+     *
+     * @param resolverKey name registered via {@link LimiterConfig#registerResolver}
+     * @param requests    maximum requests allowed per window
+     * @param window      window duration in {@code unit}
+     * @param unit        time unit for {@code window}
+     */
+    public Middleware limit(String resolverKey, int requests, long window, TimeUnit unit) {
+        return limit(resolverKey, requests, window, unit, LimitStrategy.FIXED_WINDOW);
+    }
+
+    /**
+     * Returns a {@link Middleware} that enforces the given rate limit with the specified strategy.
+     *
+     * @param resolverKey name registered via {@link LimiterConfig#registerResolver}
+     * @param requests    maximum requests allowed per window
+     * @param window      window duration in {@code unit}
+     * @param unit        time unit for {@code window}
+     * @param strategy    rate-limit algorithm
+     */
+    public Middleware limit(String resolverKey, int requests, long window, TimeUnit unit, LimitStrategy strategy) {
+        // Fail-fast: resolve the lambda at wiring time, not at request time.
+        KeyResolver resolver = config.requireResolver(resolverKey);
+        LimitConfig cfg      = new LimitConfig(requests, unit.toMillis(window), strategy.create());
+        return LimiterExtension.buildMiddleware(resolver, cfg, store);
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/KeyResolver.java

@@ -0,0 +1,20 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.models.Request;
+
+/**
+ * Extracts a partition key from an incoming request.
+ *
+ * <p>The resolved key identifies who the rate limit applies to — an IP address,
+ * an authenticated user ID, an API key, etc. Implementations are captured once
+ * at route registration time and called directly (no registry lookup) on every request.
+ *
+ * <pre>{@code
+ * conf.registerResolver("ip",       req -> req.header("X-Forwarded-For"));
+ * conf.registerResolver("auth_user", req -> ClaimsHolder.user().sub());
+ * }</pre>
+ */
+@FunctionalInterface
+public interface KeyResolver {
+    String resolve(Request req);
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/Limit.java

@@ -0,0 +1,48 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.exceptions.InitializationException;
+import dev.relism.flash.models.RequestHandler;
+
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+import java.util.concurrent.TimeUnit;
+
+/**
+ * Applies a rate limit to a class-based {@link RequestHandler}.
+ *
+ * <p>The annotation is processed at boot time by the {@link LimiterExtension} annotation
+ * processor. If {@link #key()} names a resolver that was never registered,
+ * startup fails immediately with {@link InitializationException}.
+ *
+ * <pre>{@code
+ * // 100 req/s per client IP — fixed window
+ * @Limit(requests = 100, window = 1)
+ * public class SearchHandler extends RequestHandler { ... }
+ *
+ * // 20 req/min per authenticated user — token bucket
+ * @Limit(key = "auth_user", requests = 20, window = 1, windowUnit = TimeUnit.MINUTES,
+ *        strategy = LimitStrategy.TOKEN_BUCKET)
+ * public class ExpensiveHandler extends RequestHandler { ... }
+ * }</pre>
+ */
+@Target(ElementType.TYPE)
+@Retention(RetentionPolicy.RUNTIME)
+public @interface Limit {
+
+    /** Name of the resolver registered via {@link LimiterConfig#registerResolver}. Default: {@code "ip"}. */
+    String key() default "ip";
+
+    /** Maximum number of requests allowed per {@link #window()}. */
+    int requests();
+
+    /** Window duration in {@link #windowUnit()} units. */
+    long window();
+
+    /** Unit for {@link #window()}. Default: {@link TimeUnit#SECONDS}. */
+    TimeUnit windowUnit() default TimeUnit.SECONDS;
+
+    /** Rate-limit algorithm. Default: {@link LimitStrategy#FIXED_WINDOW}. */
+    LimitStrategy strategy() default LimitStrategy.FIXED_WINDOW;
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/LimitConfig.java

@@ -0,0 +1,11 @@
+package dev.relism.flash.ext.limiter;
+
+/**
+ * Immutable configuration snapshot for a single rate-limit rule.
+ * Created once at boot time and captured directly in the middleware closure.
+ *
+ * @param limit      Maximum allowed requests per window.
+ * @param windowMs   Window duration in milliseconds.
+ * @param strategy   Strategy instance bound to this rule (one per rule, not shared).
+ */
+public record LimitConfig(int limit, long windowMs, RateLimitStrategy strategy) {}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/LimitStrategy.java

@@ -0,0 +1,58 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.ext.limiter.strategy.FixedWindowStrategy;
+import dev.relism.flash.ext.limiter.strategy.SlidingWindowStrategy;
+import dev.relism.flash.ext.limiter.strategy.TokenBucketStrategy;
+
+/**
+ * Enumeration of built-in rate-limit algorithms. Each constant is a factory
+ * for its corresponding {@link RateLimitStrategy} implementation.
+ *
+ * <p>New algorithms can be added here without touching the rest of the extension.
+ * The enum value is referenced by {@link Limit#strategy()} so user code refers
+ * to the algorithm by name ({@code LimitStrategy.FIXED_WINDOW}) rather than
+ * instantiating strategy objects directly.
+ *
+ * <pre>{@code
+ * @Limit(key = "ip", requests = 100, window = 1, strategy = LimitStrategy.TOKEN_BUCKET)
+ * public class SearchHandler extends RequestHandler { ... }
+ * }</pre>
+ */
+public enum LimitStrategy {
+
+    /**
+     * Fixed-window counter: resets to zero at each clock-aligned window boundary.
+     * Simple, minimal memory, but allows up to 2× the limit in bursts that straddle
+     * two windows.
+     */
+    FIXED_WINDOW {
+        @Override
+        public RateLimitStrategy create() { return new FixedWindowStrategy(); }
+    },
+
+    /**
+     * Token-bucket: tokens refill continuously. Smooth burst absorption — a client
+     * that was idle accumulates tokens and can fire a short burst, but sustained
+     * excess traffic is rejected. Preferred for API endpoints where occasional bursts
+     * are legitimate.
+     */
+    TOKEN_BUCKET {
+        @Override
+        public RateLimitStrategy create() { return new TokenBucketStrategy(); }
+    },
+
+    /**
+     * Sliding-window counter: interpolates between the previous window's count and the
+     * current window's count weighted by how far into the current window we are.
+     * Eliminates the boundary burst of {@link #FIXED_WINDOW} while remaining O(1)
+     * memory and lock-free. Slight approximation — worst-case error ≈ a few percent at
+     * window boundaries.
+     */
+    SLIDING_WINDOW {
+        @Override
+        public RateLimitStrategy create() { return new SlidingWindowStrategy(); }
+    };
+
+    /** Creates a fresh, stateless {@link RateLimitStrategy} instance for this algorithm. */
+    public abstract RateLimitStrategy create();
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/LimiterConfig.java

@@ -0,0 +1,82 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.exceptions.InitializationException;
+
+import java.net.InetSocketAddress;
+import java.util.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Extension configuration: holds the named {@link KeyResolver} registry.
+ *
+ * <p>Resolvers are registered during the <em>config phase</em> (before {@code install}).
+ * After {@link LimiterExtension#install} is called, the registry is consulted once per
+ * route/handler at boot to capture the resolver lambda directly into the middleware closure.
+ * There is no map lookup on the request hot-path.
+ *
+ * <p>The built-in {@code "ip"} resolver is always present and extracts the client IP from
+ * {@code X-Forwarded-For} (first address) or {@code X-Real-IP}. Override it with
+ * {@code registerResolver("ip", ...)} if needed.
+ *
+ * <pre>{@code
+ * LimiterConfig conf = new LimiterConfig()
+ *     .registerResolver("auth_user", req -> {
+ *         // custom logic — e.g. extract sub from ClaimsHolder
+ *         return ClaimsHolder.exists() ? ClaimsHolder.user().sub() : "anonymous";
+ *     });
+ *
+ * app.install(new LimiterExtension(conf));
+ * }</pre>
+ */
+public final class LimiterConfig {
+
+    private final Map<String, KeyResolver> resolvers = new LinkedHashMap<>();
+
+    public LimiterConfig() {
+        // Built-in mandatory "ip" resolver.
+        // Resolution order (standard reverse-proxy chain):
+        //   1. X-Forwarded-For — first address (client behind one or more proxies)
+        //   2. X-Real-IP       — single forwarded IP (nginx proxy_set_header X-Real-IP)
+        //   3. Socket address  — direct connection, no proxy headers (zero alloc: the
+        //                        InetSocketAddress already exists from accept(); only
+        //                        getHostAddress() allocates a String, and only when reached)
+        resolvers.put("ip", req -> {
+            String xff = req.header("X-Forwarded-For");
+            if (xff != null) {
+                int comma = xff.indexOf(',');
+                return comma > 0 ? xff.substring(0, comma).strip() : xff.strip();
+            }
+            String xri = req.header("X-Real-IP");
+            if (xri != null) return xri.strip();
+            InetSocketAddress addr = req.remoteAddress();
+            return addr != null ? addr.getAddress().getHostAddress() : "unknown";
+        });
+    }
+
+    /**
+     * Registers (or replaces) a named key resolver. Returns {@code this} for fluent chaining.
+     *
+     * @param name     identifier referenced by {@link Limit#key()} and {@link Guard#limit}
+     * @param resolver lambda that extracts the partition key from a request
+     */
+    public LimiterConfig registerResolver(String name, KeyResolver resolver) {
+        if (name == null || name.isBlank()) throw new IllegalArgumentException("Resolver name must not be blank");
+        if (resolver == null)               throw new IllegalArgumentException("Resolver must not be null");
+        resolvers.put(name, resolver);
+        return this;
+    }
+
+    /**
+     * Returns the resolver for {@code name}.
+     *
+     * @throws InitializationException if no resolver with that name has been registered —
+     *         checked at boot time so misconfigurations surface immediately.
+     */
+    KeyResolver requireResolver(String name) {
+        KeyResolver r = resolvers.get(name);
+        if (r == null) throw new InitializationException(
+                "Rate-limit resolver \"" + name + "\" is not registered. " +
+                "Call LimiterConfig.registerResolver(\"" + name + "\", req -> ...) before install.");
+        return r;
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/LimiterExtension.java

@@ -0,0 +1,192 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.ext.openapi.OpenApiContributor;
+import dev.relism.flash.ext.openapi.OpenApiContributorRegistry;
+import dev.relism.flash.ext.openapi.OpenApiOperationContribution;
+import dev.relism.flash.ext.openapi.OpenApiResponseContribution;
+import dev.relism.flash.extension.AnnotationProcessor;
+import dev.relism.flash.extension.FlashRegistrar;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.extension.FlashExtension;
+import dev.relism.flash.http.HttpStatus;
+import dev.relism.flash.routing.Middleware;
+import dev.relism.flash.routing.MiddlewareKey;
+import dev.relism.flash.routing.MiddlewareNode;
+
+import java.nio.charset.StandardCharsets;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * Rate-limiting extension for Flash.
+ *
+ * <p>At {@link #provide}:
+ * <ol>
+ *   <li>Creates a single {@link BucketStore} shared by all rules in this extension instance.</li>
+ *   <li>Provides a {@link Guard} in the {@link FlashContext} for manual use on lambda routes.</li>
+ *   <li>Registers an {@link AnnotationProcessor} for {@link Limit}:
+ *       reads the annotation once per handler class at boot, resolves the key lambda
+ *       fail-fast, then returns a pre-compiled middleware — zero map lookups at request time.</li>
+ * </ol>
+ *
+ * <h3>Annotation-based (class handlers)</h3>
+ * <pre>{@code
+ * @Limit(requests = 100, window = 1)                          // 100 req/s per IP
+ * public class SearchHandler extends RequestHandler { ... }
+ *
+ * @Limit(key = "auth_user", requests = 20, window = 1,
+ *        windowUnit = TimeUnit.MINUTES,
+ *        strategy   = LimitStrategy.TOKEN_BUCKET)
+ * public class ReportHandler extends RequestHandler { ... }
+ * }</pre>
+ *
+ * <h3>Lambda routes (via Guard)</h3>
+ * <pre>{@code
+ * app.install(new LimiterExtension(
+ *     new LimiterConfig().registerResolver("auth_user", req -> ClaimsHolder.user().sub())));
+ *
+ * // inside a FlashContext.onReady(...) callback:
+ * Guard guard = ctx.require(Guard.class);
+ * app.get("/api/search", handler, guard.limit("ip", 50, 1, TimeUnit.SECONDS));
+ * }</pre>
+ */
+public final class LimiterExtension implements FlashExtension {
+    private static final MiddlewareKey LIMIT = MiddlewareKey.of("flash.limiter.limit");
+
+    private final LimiterConfig config;
+
+    /** Installs with default config (only the built-in {@code "ip"} resolver). */
+    public LimiterExtension() {
+        this(new LimiterConfig());
+    }
+
+    /** Installs with a custom {@link LimiterConfig} (custom resolvers, etc.). */
+    public LimiterExtension(LimiterConfig config) {
+        this.config = config;
+    }
+
+    @Override
+    public void configure(FlashRegistrar<?> app, FlashContext ctx) {
+        BucketStore store = new BucketStore();
+        Guard       guard = new Guard(config, store);
+
+        ctx.provide(Guard.class,        guard);
+        ctx.provide(LimiterConfig.class, config);
+
+        // Annotation processor: runs once per class-based handler at boot.
+        ctx.addAnnotationProcessor(handlerClass -> {
+            Limit ann = handlerClass.getAnnotation(Limit.class);
+            if (ann == null) return List.of();
+
+            // Fail-fast: if the key is unknown the server refuses to start.
+            KeyResolver resolver = config.requireResolver(ann.key());
+            LimitConfig cfg      = new LimitConfig(
+                    ann.requests(),
+                    ann.windowUnit().toMillis(ann.window()),
+                    ann.strategy().create()
+            );
+
+            return List.of(MiddlewareNode.of(LIMIT, buildMiddleware(resolver, cfg, store)));
+        });
+        ctx.onReady(() -> {
+            try {
+                OpenApiIntegration.register(ctx);
+            } catch (NoClassDefFoundError ignored) {
+                // flash-ext-openapi not available — OpenAPI integration disabled
+            }
+        });
+    }
+
+    // ── Package-private helper — shared with Guard ────────────────────────────
+
+    /**
+     * Builds the rate-limit {@link Middleware} from an already-resolved resolver lambda.
+     *
+     * <p>Hot-path design:
+     * <ul>
+     *   <li>{@code resolver} is captured directly in the closure — no registry lookup per request.</li>
+     *   <li>{@code resultBuf} is a per-{@link Middleware}-instance ThreadLocal {@code long[2]}.
+     *       Allocated once per thread, reused forever — zero per-request allocation.</li>
+     *   <li>The static {@code X-RateLimit-Limit} header is pre-encoded at boot — zero-alloc.</li>
+     * </ul>
+     */
+    static Middleware buildMiddleware(KeyResolver resolver, LimitConfig cfg, BucketStore store) {
+        ThreadLocal<long[]> resultBuf  = ThreadLocal.withInitial(() -> new long[2]);
+        byte[]              limitHeader = ("X-RateLimit-Limit: " + cfg.limit() + "\r\n")
+                .getBytes(StandardCharsets.UTF_8);
+
+        return next -> (req, res) -> {
+            String key    = resolver.resolve(req);
+            Bucket bucket = store.get(key);
+            long[] out    = resultBuf.get();
+
+            boolean allowed = cfg.strategy().check(bucket, cfg, out);
+
+            res.header(limitHeader);
+            res.header("X-RateLimit-Remaining", String.valueOf(out[0]));
+            res.header("X-RateLimit-Reset",     String.valueOf(out[1]));
+
+            if (!allowed) {
+                long retryAfter = Math.max(1L, out[1] - System.currentTimeMillis() / 1000L);
+                res.status(HttpStatus.TOO_MANY_REQUESTS)
+                   .header("Retry-After", String.valueOf(retryAfter));
+                return "Too Many Requests";
+            }
+
+            return next.handle(req, res);
+        };
+    }
+
+    private static final class OpenApiIntegration {
+        private static final Map<String, Object> INTEGER_SCHEMA = Map.of("type", "integer");
+        private static final Map<String, Object> LIMIT_HEADER = Map.of(
+                "description", "Maximum requests allowed in current window",
+                "schema", INTEGER_SCHEMA
+        );
+        private static final Map<String, Object> REMAINING_HEADER = Map.of(
+                "description", "Requests remaining in current window",
+                "schema", INTEGER_SCHEMA
+        );
+        private static final Map<String, Object> RESET_HEADER = Map.of(
+                "description", "Unix epoch seconds when quota resets or next token arrives",
+                "schema", INTEGER_SCHEMA
+        );
+        private static final Map<String, Object> RETRY_AFTER_HEADER = Map.of(
+                "description", "Seconds to wait before retrying",
+                "schema", INTEGER_SCHEMA
+        );
+
+        static void register(FlashContext ctx) {
+            ctx.find(OpenApiContributorRegistry.class)
+                    .ifPresent(registry -> registry.add(new OpenApiContributor() {
+                        @Override
+                        public OpenApiOperationContribution operationFor(Class<?> handlerClass) {
+                            if (handlerClass.getAnnotation(Limit.class) == null) {
+                                return OpenApiOperationContribution.builder().build();
+                            }
+
+                            OpenApiResponseContribution common =
+                                    OpenApiResponseContribution.builder()
+                                            .header("X-RateLimit-Limit", LIMIT_HEADER)
+                                            .header("X-RateLimit-Remaining", REMAINING_HEADER)
+                                            .header("X-RateLimit-Reset", RESET_HEADER)
+                                            .build();
+
+                            OpenApiResponseContribution tooManyRequests =
+                                    OpenApiResponseContribution.builder()
+                                            .description("Too Many Requests")
+                                            .header("X-RateLimit-Limit", LIMIT_HEADER)
+                                            .header("X-RateLimit-Remaining", REMAINING_HEADER)
+                                            .header("X-RateLimit-Reset", RESET_HEADER)
+                                            .header("Retry-After", RETRY_AFTER_HEADER)
+                                            .build();
+
+                            return OpenApiOperationContribution.builder()
+                                    .allResponses(common)
+                                    .response(429, tooManyRequests)
+                                    .build();
+                        }
+                    }));
+        }
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/RateLimitStrategy.java

@@ -0,0 +1,39 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.ext.limiter.strategy.FixedWindowStrategy;
+import dev.relism.flash.ext.limiter.strategy.SlidingWindowStrategy;
+import dev.relism.flash.ext.limiter.strategy.TokenBucketStrategy;
+
+/**
+ * Contract for a rate-limit algorithm. Implementations must be:
+ * <ul>
+ *   <li><b>Lock-free</b> — rely only on {@link java.util.concurrent.atomic.AtomicLong} CAS operations.</li>
+ *   <li><b>Stateless</b> — all mutable state lives in the {@link Bucket}; the strategy itself
+ *       holds no instance fields so the same object can be shared across threads and rules.</li>
+ * </ul>
+ *
+ * <p>Called on every request — must not allocate on the hot path.
+ *
+ * @see FixedWindowStrategy
+ * @see SlidingWindowStrategy
+ * @see TokenBucketStrategy
+ */
+public interface RateLimitStrategy {
+
+    /**
+     * Checks whether this request is within the limit and updates the bucket atomically.
+     *
+     * <p>On return, {@code out} contains:
+     * <ul>
+     *   <li>{@code out[0]} — remaining allowed requests in the current window (≥ 0).</li>
+     *   <li>{@code out[1]} — Unix epoch seconds at which the quota resets (for {@code X-RateLimit-Reset}
+     *       and {@code Retry-After} headers).</li>
+     * </ul>
+     *
+     * @param bucket  per-key state carrier (pre-allocated, never null)
+     * @param cfg     immutable rule configuration
+     * @param out     caller-supplied two-element array; values are overwritten on every call
+     * @return {@code true} if the request is within the limit and should proceed
+     */
+    boolean check(Bucket bucket, LimitConfig cfg, long[] out);
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/strategy/FixedWindowStrategy.java

@@ -0,0 +1,54 @@
+package dev.relism.flash.ext.limiter.strategy;
+
+import dev.relism.flash.ext.limiter.Bucket;
+import dev.relism.flash.ext.limiter.LimitConfig;
+import dev.relism.flash.ext.limiter.RateLimitStrategy;
+
+/**
+ * Fixed-window rate limit: allows up to {@link LimitConfig#limit()} requests per window of
+ * {@link LimitConfig#windowMs()} milliseconds. The window is aligned to clock time
+ * (e.g. 10:00:00 – 10:00:59 for a 60-second window), not sliding.
+ *
+ * <h3>Implementation</h3>
+ * The entire state fits in a single {@link java.util.concurrent.atomic.AtomicLong}
+ * ({@link Bucket#slot0}), packed as:
+ * <pre>
+ *   high 32 bits = reduced epoch  (currentTimeMs / windowMs) & 0xFFFFFFFFL
+ *   low  32 bits = request count in the current window
+ * </pre>
+ * Each request performs a single CAS loop — no locks, no allocations.
+ * At a window boundary the CAS atomically resets the counter to 1.
+ *
+ * <p>The reduced epoch wraps every {@code 2^32 × windowMs} milliseconds
+ * (~13,000 years for a 100 ms window) — collision-free in practice.
+ */
+public final class FixedWindowStrategy implements RateLimitStrategy {
+
+    @Override
+    public boolean check(Bucket bucket, LimitConfig cfg, long[] out) {
+        long now       = System.currentTimeMillis();
+        long absEpoch  = now / cfg.windowMs();
+        int  epoch     = (int)(absEpoch & 0xFFFFFFFFL);  // reduced epoch, collision-safe
+
+        while (true) {
+            long packed      = bucket.slot0.get();
+            int  storedEpoch = (int)(packed >>> 32);
+            int  count       = (int)(packed & 0xFFFFFFFFL);
+
+            // Same window: increment; new window: reset to 1.
+            // Cap at limit+1 to guard against int overflow on extreme traffic.
+            int newCount = (storedEpoch == epoch)
+                    ? Math.min(count + 1, cfg.limit() + 1)
+                    : 1;
+
+            long newPacked = ((long) epoch << 32) | (newCount & 0xFFFFFFFFL);
+
+            if (bucket.slot0.compareAndSet(packed, newPacked)) {
+                out[0] = Math.max(0L, cfg.limit() - newCount);
+                out[1] = (absEpoch + 1) * cfg.windowMs() / 1000L;
+                return newCount <= cfg.limit();
+            }
+            // CAS lost — contention; re-read and retry.
+        }
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/strategy/SlidingWindowStrategy.java

@@ -0,0 +1,86 @@
+package dev.relism.flash.ext.limiter.strategy;
+
+import dev.relism.flash.ext.limiter.Bucket;
+import dev.relism.flash.ext.limiter.LimitConfig;
+import dev.relism.flash.ext.limiter.RateLimitStrategy;
+
+/**
+ * Sliding-window counter rate limit: approximates a true sliding window by interpolating
+ * between the previous fixed window's count and the current window's count.
+ *
+ * <pre>
+ *   estimate = prevCount × (1 − elapsed / windowMs) + currentCount
+ * </pre>
+ *
+ * <p>This is the same approximation used by Redis. It eliminates the boundary burst
+ * problem of {@link FixedWindowStrategy} while staying O(1) memory and lock-free.
+ * The error is bounded: in the worst case the true rate at the boundary can exceed
+ * the limit by at most {@code limit × (1 − elapsed/windowMs)} — typically a few percent.
+ *
+ * <h3>Slot layout</h3>
+ * <ul>
+ *   <li>{@link Bucket#slot0} — packed {@code (reducedEpoch << 32 | currentCount)}</li>
+ *   <li>{@link Bucket#slot1} — count from the immediately preceding epoch (0 = none)</li>
+ * </ul>
+ *
+ * <p>On a window transition the thread that wins the {@code slot0} CAS also writes
+ * {@code slot1}. A concurrent thread that reads {@code slot0} after the transition but
+ * before {@code slot1} is written sees a slightly stale previous count — acceptable for
+ * an approximation algorithm.
+ */
+public final class SlidingWindowStrategy implements RateLimitStrategy {
+
+    @Override
+    public boolean check(Bucket bucket, LimitConfig cfg, long[] out) {
+        long now      = System.currentTimeMillis();
+        long windowMs = cfg.windowMs();
+        long absEpoch = now / windowMs;
+        int  epoch    = (int)(absEpoch & 0xFFFFFFFFL);
+        long elapsed  = now % windowMs;   // ms elapsed inside the current window
+
+        while (true) {
+            long packed      = bucket.slot0.get();
+            int  storedEpoch = (int)(packed >>> 32);
+            int  count       = (int)(packed & 0xFFFFFFFFL);
+
+            if (storedEpoch == epoch) {
+                // ── Same window ──────────────────────────────────────────────────
+                long prevCount = bucket.slot1.get();
+                // Integer interpolation — no floating-point on hot path.
+                long estimate  = (prevCount * (windowMs - elapsed)) / windowMs + count + 1;
+
+                if (estimate > cfg.limit()) {
+                    out[0] = 0L;
+                    out[1] = (absEpoch + 1) * windowMs / 1000L;
+                    return false;
+                }
+
+                int  newCount  = Math.min(count + 1, cfg.limit() + 1);
+                long newPacked = ((long) epoch << 32) | (newCount & 0xFFFFFFFFL);
+                if (!bucket.slot0.compareAndSet(packed, newPacked)) continue; // CAS lost, retry
+
+                out[0] = Math.max(0L, cfg.limit() - estimate);
+                out[1] = (absEpoch + 1) * windowMs / 1000L;
+                return true;
+
+            } else {
+                // ── Window transition ────────────────────────────────────────────
+                // If the stored epoch is exactly the one before ours, carry its count forward.
+                // If it's older (gap ≥ 2 windows), the previous window is effectively empty.
+                int  prevEpoch = (int)((absEpoch - 1) & 0xFFFFFFFFL);
+                long oldCount  = (storedEpoch == prevEpoch) ? count : 0L;
+
+                long newPacked = ((long) epoch << 32) | 1L;
+                if (!bucket.slot0.compareAndSet(packed, newPacked)) continue; // CAS lost, retry
+
+                // Won the transition: publish old count so the same-window branch can read it.
+                bucket.slot1.set(oldCount);
+
+                long estimate = (oldCount * (windowMs - elapsed)) / windowMs + 1;
+                out[0] = Math.max(0L, cfg.limit() - estimate);
+                out[1] = (absEpoch + 1) * windowMs / 1000L;
+                return estimate <= cfg.limit();
+            }
+        }
+    }
+}

flash-extensions/flash-ext-limiter/src/main/java/dev/relism/flash/ext/limiter/strategy/TokenBucketStrategy.java

@@ -0,0 +1,68 @@
+package dev.relism.flash.ext.limiter.strategy;
+
+import dev.relism.flash.ext.limiter.Bucket;
+import dev.relism.flash.ext.limiter.LimitConfig;
+import dev.relism.flash.ext.limiter.RateLimitStrategy;
+
+/**
+ * Token-bucket rate limit: tokens refill continuously at a rate of
+ * {@code limit / windowMs} tokens per millisecond, up to a maximum of {@code limit} tokens.
+ * Each request consumes one token. Burst traffic is absorbed until the bucket empties.
+ *
+ * <h3>Implementation</h3>
+ * <ul>
+ *   <li>{@link Bucket#slot0} — current token count scaled by {@value #SCALE}
+ *       (allows sub-token precision without floating-point). Starts at 0; treated as
+ *       {@code maxScaled} when {@link Bucket#slot1} is 0 (first call → bucket starts full).</li>
+ *   <li>{@link Bucket#slot1} — last-refill timestamp in ms. 0 = not yet initialised.</li>
+ * </ul>
+ *
+ * <p>Each request CAS-loops on {@code slot0}; {@code slot1} is advanced monotonically via CAS
+ * after a successful token consumption — never regresses to an older timestamp under concurrent load.
+ */
+public final class TokenBucketStrategy implements RateLimitStrategy {
+
+    /** Fixed-point scale factor. Stored tokens = actual tokens × SCALE. */
+    static final long SCALE = 1_000L;
+
+    @Override
+    public boolean check(Bucket bucket, LimitConfig cfg, long[] out) {
+        long now       = System.currentTimeMillis();
+        long maxScaled = (long) cfg.limit() * SCALE;
+        // Refill rate: limit tokens per windowMs → (limit * SCALE) / windowMs scaled-tokens per ms.
+        // Minimum 1 to ensure progress even for very large windows.
+        long rfPerMs   = Math.max(1L, maxScaled / cfg.windowMs());
+
+        while (true) {
+            long lastMs    = bucket.slot1.get();
+            long rawTokens = bucket.slot0.get();
+
+            // When slot1 == 0 the bucket has never been used: treat as one full window elapsed
+            // so the bucket starts completely full.
+            long elapsed       = (lastMs == 0L) ? cfg.windowMs() : Math.max(0L, now - lastMs);
+            long currentTokens = Math.min(maxScaled, rawTokens + elapsed * rfPerMs);
+
+            if (currentTokens < SCALE) {
+                // Not enough for one token — compute when the next token arrives.
+                long needed   = SCALE - currentTokens;
+                long msToNext = (needed + rfPerMs - 1) / rfPerMs; // ceiling division
+                out[0] = 0L;
+                out[1] = (now + msToNext) / 1000L;
+                // Best-effort: advance the refill baseline so the next call gets a fresh elapsed.
+                bucket.slot0.compareAndSet(rawTokens, currentTokens);
+                bucket.slot1.compareAndSet(lastMs, now);
+                return false;
+            }
+
+            long newTokens = currentTokens - SCALE;
+            if (bucket.slot0.compareAndSet(rawTokens, newTokens)) {
+                // Advance refill baseline: CAS ensures we never regress to an older timestamp.
+                if (lastMs < now) bucket.slot1.compareAndSet(lastMs, now);
+                out[0] = newTokens / SCALE;
+                out[1] = now / 1000L;
+                return true;
+            }
+            // CAS lost — another thread consumed a token concurrently; re-read and retry.
+        }
+    }
+}

flash-extensions/flash-ext-limiter/src/test/java/dev/relism/flash/ext/limiter/LimiterOpenApiInteropTest.java

@@ -0,0 +1,87 @@
+package dev.relism.flash.ext.limiter;
+
+import dev.relism.flash.ext.openapi.OpenApiContributor;
+import dev.relism.flash.ext.openapi.OpenApiContributorRegistry;
+import dev.relism.flash.ext.openapi.OpenApiOperationContribution;
+import dev.relism.flash.ext.openapi.OpenApiResponseContribution;
+import dev.relism.flash.extension.FlashContext;
+import dev.relism.flash.models.Request;
+import dev.relism.flash.models.RequestHandler;
+import dev.relism.flash.models.Response;
+import dev.relism.flash.routing.GET;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class LimiterOpenApiInteropTest {
+
+    @GET("/limited")
+    @Limit(requests = 10, window = 1)
+    static class LimitedHandler extends RequestHandler {
+        @Override
+        public Object handle(Request request, Response response) {
+            return null;
+        }
+    }
+
+    @GET("/plain")
+    static class PlainHandler extends RequestHandler {
+        @Override
+        public Object handle(Request request, Response response) {
+            return null;
+        }
+    }
+
+    @Test
+    void registersContributor_whenOpenApiRegistryExists() {
+        FlashContext ctx = new FlashContext();
+        OpenApiContributorRegistry registry = new OpenApiContributorRegistry();
+        ctx.provide(OpenApiContributorRegistry.class, registry);
+
+        new LimiterExtension().configure(null, ctx);
+        ctx.complete();
+
+        assertEquals(1, registry.contributors().size());
+    }
+
+    @Test
+    void limitedHandler_contributesHeadersAnd429() {
+        FlashContext ctx = new FlashContext();
+        OpenApiContributorRegistry registry = new OpenApiContributorRegistry();
+        ctx.provide(OpenApiContributorRegistry.class, registry);
+        new LimiterExtension().configure(null, ctx);
+        ctx.complete();
+
+        OpenApiContributor contributor = registry.contributors().getFirst();
+        OpenApiOperationContribution operation = contributor.operationFor(LimitedHandler.class);
+
+        OpenApiResponseContribution all = operation.allResponses();
+        assertNotNull(all);
+        assertTrue(all.headers().containsKey("X-RateLimit-Limit"));
+        assertTrue(all.headers().containsKey("X-RateLimit-Remaining"));
+        assertTrue(all.headers().containsKey("X-RateLimit-Reset"));
+
+        OpenApiResponseContribution tooMany = operation.responses().get(429);
+        assertNotNull(tooMany);
+        assertEquals("Too Many Requests", tooMany.description());
+        assertTrue(tooMany.headers().containsKey("Retry-After"));
+    }
+
+    @Test
+    void plainHandler_hasNoContribution() {
+        FlashContext ctx = new FlashContext();
+        OpenApiContributorRegistry registry = new OpenApiContributorRegistry();
+        ctx.provide(OpenApiContributorRegistry.class, registry);
+        new LimiterExtension().configure(null, ctx);
+        ctx.complete();
+
+        OpenApiContributor contributor = registry.contributors().getFirst();
+        OpenApiOperationContribution operation = contributor.operationFor(PlainHandler.class);
+
+        assertTrue(operation.isEmpty());
+        assertFalse(operation.responses().containsKey(429));
+    }
+}

flash-extensions/flash-ext-mcp/docs/README.md

@@ -0,0 +1,58 @@
+# flash-ext-mcp
+
+`flash-ext-mcp` turns a Flash5 app into an [MCP](https://modelcontextprotocol.io) (Model Context
+Protocol) server: JSON-RPC 2.0 over the Streamable HTTP transport, tools/resources/prompts
+declared as plain classes and discovered at boot, optional OAuth2 protection built on
+`flash-ext-oidc`.
+
+## Quick Start
+
+```java
+FlashApp.create(8080)
+    .install(new McpExtension(McpConfig.builder("my-mcp-server")
+        .toolsPackage("com.example.tools")
+        .build()))
+    .start();
+```
+
+```java
+@Tool(name = "get_weather", description = "Get current weather for a city",
+      args = @ToolArg(name = "city", description = "City name", required = true))
+public class GetWeatherTool extends McpTool {
+
+    private WeatherService weatherService;
+
+    @Override
+    protected void onInit() {
+        weatherService = require(WeatherService.class);
+    }
+
+    @Override
+    public ToolResponse call(ToolArguments args) {
+        return ToolResponse.success(new TextContent(weatherService.fetch(args.getString("city"))));
+    }
+}
+```
+
+## Operating Model
+
+- **One class per tool/resource/prompt** — mirrors `RequestHandler`: a no-arg constructor,
+  `onInit()` to cache services from `FlashContext`, one hot-path method
+  (`call`/`read`/`render`). No CDI, no field injection, no reflection on the hot path.
+- **Boot-time precompilation** — `tools/list`/`resources/list`/`prompts/list` JSON payloads
+  (including JSON Schema) are built once at boot and spliced verbatim into responses. See
+  `tools-resources-prompts.md`.
+- **Transport**: Streamable HTTP, `POST`-only, stateless in this revision — see `transport.md`
+  for exactly what that means and why.
+- **Security**: optional, policy-driven OAuth2 via `flash-ext-oidc` — see `security.md`.
+- **JSON**: this extension owns its JSON handling independently of `flash-ext-jackson` — see
+  `jackson-interop.md` for why, and how a future opt-in reuse could work.
+
+## Documents
+
+- [`tools-resources-prompts.md`](tools-resources-prompts.md) — defining tools, resources, prompts
+- [`transport.md`](transport.md) — Streamable HTTP scope, session/SSE limitations, Origin validation
+- [`security.md`](security.md) — `McpSecurity` policy, OAuth2 resolution, RFC 9728 / RFC 8707
+- [`keycloak.md`](keycloak.md) — Keycloak-specific setup cookbook: Dynamic Client Registration,
+  the RFC 8707 audience mapper gotcha, and how to verify/debug it
+- [`jackson-interop.md`](jackson-interop.md) — why this extension does not depend on `flash-ext-jackson`

flash-extensions/flash-ext-mcp/docs/jackson-interop.md

@@ -0,0 +1,51 @@
+# Why no `flash-ext-jackson` interop (yet)
+
+## The decision
+
+`flash-ext-mcp` does not depend on, or integrate with, `flash-ext-jackson`. It brings its own
+JSON handling (`jackson-databind`/`jackson-core` as a plain library dependency, wrapped by the
+internal `McpJson` utility) and never touches `flash-ext-jackson`'s `Json`/`JacksonMiddleware`/
+shared `ObjectMapper`, even if the host app has `flash-ext-jackson` installed. This was a
+deliberate choice, discussed and made explicitly — not an oversight — and is written down here
+so it isn't accidentally "fixed" later without re-litigating the trade-off.
+
+## Why
+
+`flash-ext-jackson`'s `Json` class is built around full databinding:
+`mapper.readValue(bytes, SomeDto.class)` / `mapper.writeValueAsBytes(obj)` — reflection-driven
+property matching in both directions. The MCP JSON-RPC envelope has a **fixed, known shape**
+(`{jsonrpc, id, method, params}` in, `{jsonrpc, id, result|error}` out) defined by a spec, not by
+application DTOs. Given that, hand-writing it with `JsonGenerator` directly is both simpler and
+strictly cheaper than round-tripping through databinding: no property-name matching, no
+reflection, no intermediate POJO graph for the parts of the response this extension controls
+(the envelope itself, `tools/list`/`resources/list`/`prompts/list` — precompiled once at boot,
+see `tools-resources-prompts.md` — and the fixed `TextContent`/`TextResourceContents`/
+`PromptMessage` shapes). `ToolArguments`/`PromptArguments` read the incoming `arguments` object
+as a `JsonNode` tree, not as a databound class, for the same reason — a JSON-RPC tool call's
+arguments aren't a DTO with getters/setters, they're a dynamic, per-tool-defined bag of values.
+
+This mirrors how `flash-ext-oidc` already handles its own internal JSON needs (`json-smart` for
+token-endpoint responses) independently of `flash-ext-jackson` — extensions with protocol-level
+JSON needs that are shaped by a spec, not by user code, own that JSON handling themselves rather
+than routing it through the app's general-purpose JSON extension.
+
+## What this means practically
+
+- Installing `flash-ext-mcp` never requires installing `flash-ext-jackson`. A pure MCP server
+  with no other JSON REST routes has zero unrelated dependencies to configure.
+- If the host app *does* have `flash-ext-jackson` installed for its own REST routes, that
+  `ObjectMapper`'s configuration (custom modules, date formatting, naming strategy, etc.) is
+  **not** consulted by `flash-ext-mcp` — the two JSON paths are entirely independent today.
+
+## What a future opt-in reuse could look like
+
+Nothing here rules out a later, additive convenience layer: `McpExtension.routes()` could check
+`ctx.find(ObjectMapper.class)` (populated by `JacksonExtension.provide()`) and, if present, use
+that shared mapper as the backing for an escape hatch such as `ToolArguments.as(Class<T>)` or
+for a tool that wants to `ToolResponse.success(someRecord)` and have it serialized with the
+app's own conventions — falling back to a locally-constructed default `ObjectMapper` when
+`flash-ext-jackson` isn't installed, the same "prefer shared, degrade to sane default" shape
+already used for `McpSecurity.AUTO`. That would be purely additive on top of the
+`JsonGenerator`-based envelope/content writing described above, not a replacement for it — the
+fixed-shape protocol plumbing has no reason to ever go through databinding, regardless of what
+convenience layer gets added around it.

flash-extensions/flash-ext-mcp/docs/keycloak.md

@@ -0,0 +1,107 @@
+# Keycloak cookbook
+
+`security.md` covers the OAuth2 mechanics `McpOidcIntegration` implements against any
+`flash-ext-oidc`-compatible provider. This is the Keycloak-specific setup: the exact Admin
+Console configuration for a working MCP OAuth2 flow with open Dynamic Client Registration
+(DCR) — no pre-registered clients, any MCP client self-registers on first connect.
+
+## 1. Allow Dynamic Client Registration
+
+MCP clients (Claude Desktop, Claude.ai, MCP Inspector, others) don't share one static OAuth
+client — each has its own `redirect_uri` and none know your realm in advance. They self-register
+on first connect via `POST {issuer}/clients-registrations/openid-connect` (the
+`registration_endpoint` from the AS metadata document, reached via the RFC 9728 Protected
+Resource Metadata document `McpExtension` publishes).
+
+**Clients → Client registration**: remove the **Trusted Hosts** policy — it rejects anonymous
+registration from hosts not on an explicit allowlist (`403` / `"Host not trusted"`), which
+doesn't scale to arbitrary future agents. This does not weaken end-user authentication — DCR
+only grants an app a `client_id`; every user still authenticates against Keycloak's real login
+screen regardless of which client asked. Lighter hygiene policies (**Max Clients Limit**,
+**Consent Required**) can stay, they don't interfere.
+
+## 2. RFC 8707 audience: mapper on `basic`, not a custom scope
+
+`McpOidcIntegration` rejects (403) any token whose `aud` doesn't include the MCP endpoint's
+canonical URL. Keycloak doesn't add this by default. The obvious fix — a custom client scope
+with an Audience mapper, marked Default, added to Allowed Client Scopes — **does not work**:
+clients created via the `openid-connect` DCR endpoint only ever get scopes they explicitly
+request, and most MCP clients (including MCP Inspector) don't request anything beyond what a
+server tells them to via `scopes_supported` (step 3). Default-scope auto-attachment, which is
+how a normal manually-created client would pick up a custom Default scope, doesn't apply to
+DCR-created clients at all.
+
+`basic` is the one built-in scope Keycloak attaches to every client unconditionally, regardless
+of what it registered with. Put the audience mapper there:
+
+1. **Client scopes → `basic`** → **Mappers** → **Add mapper** → **By configuration** →
+   **Audience**.
+2. **Included Custom Audience** = the exact value your server expects — check
+   `GET {parent-of-rootPath}/.well-known/oauth-protected-resource{rootPath}` on the running
+   server for the `resource` field it publishes (auto-derived from the request's
+   forwarded/`Host` headers — see `security.md`). Leave **Included Client Audience** empty (that
+   targets another Keycloak client, not a resource URL).
+3. **Add to access token** = ON.
+4. **Save.**
+
+This is unconditional and works regardless of client cooperation — keep it even after step 3
+below gets other claims flowing normally, since audience binding is a hard spec requirement
+that shouldn't depend on a client bothering to request the right scope.
+
+## 3. Other claims (username, email...): `scopes_supported` + Allowed Client Scopes
+
+`OidcUser.username()`/`.email()`/`.name()` read `preferred_username`/`email`/`name` — normally
+from the `profile`/`email` client scopes, which DCR clients don't get either, same root cause.
+Unlike audience, this **is** fixable the "normal" way, because it doesn't need to survive a
+completely uncooperative client:
+
+`McpConfig.scopesSupported("openid", "profile", "email")` publishes those scopes in the PRM
+document. MCP clients that read it (confirmed for MCP Inspector) echo them back in their DCR
+registration request — `"scope": "openid profile email offline_access"` (`offline_access` is
+Inspector's own addition, for refresh tokens). For that request to actually succeed, **Allowed
+Client Scopes** needs, exactly:
+
+- **`openid` listed explicitly.** The one genuinely non-obvious step: `openid` is not covered by
+  **Allow Default Scopes** (On by default) the way other realm-Default scopes are, even though
+  every OIDC request includes it. Until it's listed here, registration fails with a generic
+  `403 insufficient_scope` / `"Not permitted to use specified clientScope"` regardless of
+  whether everything else is configured correctly.
+- **`offline_access` listed explicitly** — it's Optional, not Default, so `ALLOW_DEFAULT_SCOPES`
+  doesn't cover it either.
+- **`profile`/`email` — do not list them here.** Mark them **Default** on the **Client scopes**
+  page (Assigned Type column) instead, and leave **Allow Default Scopes** = On. Adding an
+  already-Default scope to this list explicitly gets rejected on save
+  (`"Client scopes not allowed: [...]"`) — the list is for *additional* Optional scopes only.
+
+With that, a real client's token comes back with `preferred_username`/`email` populated
+normally.
+
+### Fallback for anything else
+
+For a claim not covered by `openid profile email` (a custom attribute, a role) — or for a client
+that ignores `scopes_supported` entirely — add a **User Property** mapper to `basic` too
+(Property `username` → Token Claim Name `preferred_username`, or whatever's needed), same as the
+audience mapper in step 2. Unconditional, works regardless of client cooperation, costs one
+mapper per claim, once, at the realm level — not per tool.
+
+## Verifying without a full OAuth round-trip
+
+**Clients → (any client) → Client scopes → Evaluate**: pick a user, run it — Default scopes
+(including `basic`) apply automatically and won't appear in the "Select scope parameters"
+picker, which only lists Optional ones — and check the **Generated Access Token** preview.
+Confirms mappers work without a browser + real MCP client round-trip each time.
+
+## If a real client still gets rejected
+
+`McpOidcIntegration.audienceGuard` logs the actual mismatch at `WARN`:
+
+```
+[flash-ext-mcp] Rejecting token (RFC 8707): aud=<token's actual aud> does not include expected
+resource identifier "<what this server expects>" — ...
+```
+
+`aud=null` → the `basic` mapper produced nothing (most common cause: **Included Custom
+Audience** left blank — the mapper saves fine and silently does nothing without it). A non-null
+`aud` that still doesn't match → compare byte-for-byte — the expected side is derived from the
+request's own forwarded/`Host` headers, so scheme/host/trailing-slash mismatches show up here
+directly, as does a proxy hop that drops `X-Forwarded-Host`.

flash-extensions/flash-ext-mcp/docs/security.md

@@ -0,0 +1,170 @@
+# Security
+
+Provider-specific setup steps (not generic OAuth2 mechanics) live in separate cookbooks —
+[`keycloak.md`](keycloak.md) for Keycloak: enabling Dynamic Client Registration, why the RFC 8707
+audience mapper needs to go on the built-in `basic` scope instead of a custom one, and the exact
+Allowed Client Scopes configuration `scopes_supported` needs to actually work.
+
+## `McpSecurity`
+
+`McpConfig.security(...)` controls how the MCP endpoint reacts to `flash-ext-oidc` being
+installed (`ctx.find(OidcMiddleware.class)`), resolved once at boot in `McpExtension.routes()`:
+
+| Policy | `flash-ext-oidc` installed | `flash-ext-oidc` absent |
+|---|---|---|
+| `REQUIRED` | protected | **boot fails** (`IllegalStateException`) |
+| `AUTO` (default) | protected | runs unprotected, logs a warning |
+| `NONE` | never protected, even if oidc is installed elsewhere in the app | runs unprotected |
+
+Use `REQUIRED` for anything you intend to run in production reachable over the network — it
+turns "someone forgot to wire up OAuth2" into a startup crash instead of a silently open
+endpoint. `AUTO` is meant for local development, where spinning up a real identity provider is
+friction you don't want yet.
+
+## Why `flash-ext-oidc` is an *optional* Maven dependency, concretely
+
+Maven's `<optional>true</optional>` only affects **transitive** propagation: consumers of
+`flash-ext-mcp` don't get `flash-ext-oidc` pulled in automatically unless they add it themselves.
+Within `flash-ext-mcp` itself, `flash-ext-oidc`'s classes are on the compile/test classpath as
+normal — this extension can (and does) reference `OidcMiddleware`/`ClaimsHolder` directly in
+source.
+
+That reference is isolated in its own class, `McpOidcIntegration`, invoked only from inside a
+`catch (NoClassDefFoundError)` block. A bare class-literal like `OidcMiddleware.class` (which
+`ctx.find(OidcMiddleware.class)` needs) forces the JVM to resolve that type the moment it's
+evaluated — if `flash-ext-oidc` is not on the *runtime* classpath at all (a genuinely
+MCP-only install, no OAuth2 anywhere in the app), the first such reference throws
+`NoClassDefFoundError`. Keeping that reference inside a separate, lazily-loaded class means
+`McpExtension` itself loads and works fine standalone; only the attempt to actually use OIDC
+fails, and only when there's something to fail. This mirrors `OidcExtension`'s own lazy bridge to
+`flash-ext-openapi` — same technique, same reason.
+
+## OAuth2 resolution details — zero-config by default
+
+When oidc is available and `security() != NONE`, `McpOidcIntegration` (an isolated,
+lazily-loaded bridge — see its javadoc) derives everything an MCP OAuth2 resource server needs
+straight from the installed `OidcMiddleware`, with no additional `McpConfig` calls required:
+
+1. The MCP route is wrapped with `flash-ext-oidc`'s own `OidcMiddleware.protect(resourceMetadataPath)`
+   — the same Bearer-token/JWKS validation path used everywhere else in Flash5, plus a
+   `resource_metadata` challenge parameter (see below). No JWT parsing or JWKS handling is
+   reimplemented here.
+2. An audience guard always runs after `protect(...)`: it reads the validated claims from
+   `ClaimsHolder` and rejects (`403`) any token whose `aud` claim does not include the resource
+   identifier — **RFC 8707 Resource Indicators / audience binding**, enforced unconditionally,
+   not opt-in. `OidcMiddleware` itself validates `aud` against its own `clientId` for ID
+   tokens, but deliberately does not enforce audience on access tokens (it varies by provider)
+   — the MCP extension adds that check on top, scoped to its own resource identifier.
+3. The resource identifier is the canonical URI of the MCP endpoint, resolved **per request** by
+   `OidcMiddleware#selfOrigin` + `rootPath` — the same scheme/host resolution `OidcExtension`
+   uses for its own redirect URIs: `X-Forwarded-Host`/`X-Forwarded-Proto` when the request came
+   through a reverse proxy, otherwise `{selfScheme()}://{Host header}`. Behind a proxy the
+   `Host` alone is the upstream address the proxy dialled, which would publish a resource
+   identifier no client can reach. `McpConfig.resourceIdentifier(...)` still overrides it
+   outright for a proxy that forwards neither header.
+4. The authorization server issuer is read from `OidcMiddleware#issuer()` unless
+   `McpConfig.authorizationServerIssuer(...)` overrides it.
+
+## RFC 9728 Protected Resource Metadata
+
+Whenever the endpoint ends up protected, `flash-ext-mcp` publishes a Protected Resource Metadata
+document at `/.well-known/oauth-protected-resource{rootPath}` — no explicit `resourceIdentifier`/
+`authorizationServerIssuer` configuration required, both are auto-derived as described above:
+
+```json
+{ "resource": "https://mcp.example.com/mcp", "authorization_servers": ["https://auth.example.com/realms/myrealm"] }
+```
+
+`resource` is computed per request from the incoming request's forwarded/`Host` headers (see
+above), so the document is correct without hardcoding the server's own public URL.
+
+### `scopes_supported`
+
+Optional per RFC 9728, omitted from the document entirely unless set via
+`McpConfig.scopesSupported("openid", "profile", "email")`:
+
+```json
+{ "resource": "...", "authorization_servers": ["..."], "scopes_supported": ["openid", "profile", "email"] }
+```
+
+This is pure advertisement — token validation doesn't change based on it — but it matters in
+practice: a client that ignores it and requests no scope at all (many do — see `keycloak.md`)
+only gets back whatever the authorization server treats as always-included regardless of
+request, which for Keycloak is just its built-in `basic` scope. A client that *does* read
+`scopes_supported` and echoes it back in its authorization/token requests gets a token with the
+claims those scopes actually provide (`profile` → `preferred_username`/`name`, etc.), without
+needing every one of those claims hand-mapped onto `basic`. Set it to whatever scopes your
+`McpTool`s actually read off `ClaimsHolder`/`OidcUser` — there's no way to auto-derive this list,
+it depends entirely on what your tools do with the claims.
+
+## `WWW-Authenticate: resource_metadata` (RFC 9728 §5.1)
+
+The MCP Authorization spec **requires** a `401` to carry `resource_metadata` in
+`WWW-Authenticate`, pointing at the Protected Resource Metadata document above — this is how a
+spec-compliant client discovers the authorization server without out-of-band configuration.
+`OidcMiddleware.protect(String resourceMetadataPath)` (an overload added specifically for this)
+builds that challenge automatically:
+
+```
+WWW-Authenticate: Bearer realm="...", resource_metadata="https://mcp.example.com/.well-known/oauth-protected-resource/mcp"
+```
+
+The plain `OidcMiddleware.protect()` (no argument), used by every other Flash5 app, is
+unaffected — this parameter is additive and MCP-specific.
+
+## Per-tool `@RolesAllowed`/`@ScopesAllowed`
+
+`McpTool` subclasses can carry `flash-ext-oidc`'s `@RolesAllowed`/`@ScopesAllowed`:
+
+```java
+@Tool(name = "delete_route", description = "Delete a route")
+@RolesAllowed("admin")
+public class DeleteRouteTool extends McpTool {
+    @Override public ToolResponse call(ToolArguments args) { ... }
+}
+```
+
+This does **not** reuse `flash-ext-oidc`'s per-route middleware mechanism (`ctx.addAnnotationProcessor`,
+the thing that makes these annotations work on a `RequestHandler`) — it can't: every tool shares
+one HTTP route (`POST {rootPath}`), already wrapped by whatever `McpSecurity` resolved above, so
+there is no per-tool route to attach a different middleware chain to. Instead,
+`McpOidcIntegration.compileToolPolicy` reads the annotations once at boot (`McpRegistry.scan`)
+and compiles them into a closure (`McpAuthPolicy`) that `McpDispatcher` runs *after* the
+route-wide auth has already succeeded and *before* invoking the specific tool named in the
+`tools/call` request — narrowing what's already-authenticated, not replacing it. A denial is a
+normal `isError: true` tool result (see `ToolResponse.error`), not an HTTP-level rejection — the
+model sees why, the same as any other tool failure.
+
+Roles are read via `OidcUser#hasRole` against `McpConfig.rolesClaimPath(...)` (default
+`"realm_access.roles"`, matching `OidcConfig`'s own default — set this explicitly if the two
+diverge; there's no way to read `OidcConfig`'s actual configured value from here). Scopes use
+`OidcUser#hasScope`'s built-in default claim paths (`scope`/`scp`), no extra config needed.
+`@ScopesAllowed(match = ScopesAllowed.Match.ANY)` and multi-role `@RolesAllowed({"admin",
+"editor"})` (OR semantics) both work exactly as they do on a `RequestHandler`.
+
+**`@Authenticated` alone has no effect and fails boot.** Once oidc is active for a server, every
+tool call is already authenticated — there's no per-tool public/authenticated split the way
+there is for HTTP routes, so a bare `@Authenticated` on a tool can't mean anything and would
+silently do nothing if allowed to compile. Boot fails instead, with a message pointing at
+`@RolesAllowed`/`@ScopesAllowed` as the actual narrowing mechanism.
+
+**Annotating a tool without active OAuth2 also fails boot**, not silently at request time: if
+`@RolesAllowed`/`@ScopesAllowed`/`@Authenticated` shows up on a tool while `McpSecurity` resolved
+to unprotected (`NONE`, or `AUTO` with no oidc installed), that's very likely a forgotten
+`OidcExtension` install or a `McpSecurity.NONE` left over from local dev — `IllegalStateException`
+at `app.start()`.
+
+## The `HttpException` safety net
+
+`flash-ext-oidc`'s middleware throws `HttpException.unauthorized()`/`forbidden()` on auth
+failure. Flash5's core does **not** special-case `HttpException` in the default exception
+handler — the out-of-the-box `AbstractRouter` default always returns a generic `500`, regardless
+of the thrown exception's embedded status code; only an app that explicitly calls
+`FlashApp#onException(...)` (or installs something that does) gets `HttpException.status()`
+honored.
+
+To keep the MCP endpoint correct regardless of what the rest of the app configures,
+`McpTransportGuards.httpExceptionGuard()` wraps the whole route and translates `HttpException`
+into the right HTTP status itself, rather than letting it fall through to the app's (possibly
+unconfigured) global handler. This is scoped entirely to the MCP route — it does not touch or
+override the app's `onException` for any other route.

flash-extensions/flash-ext-mcp/docs/tools-resources-prompts.md

@@ -0,0 +1,107 @@
+# Tools, Resources, Prompts
+
+## One class per feature
+
+Every tool, resource, and prompt is its own class — the same shape as a Flash `RequestHandler`,
+minus the HTTP-specific bits:
+
+```java
+public abstract class McpTool {
+    protected void onInit() {}                       // cache services here, once, at boot
+    protected <T> T require(Class<T> type) { ... }    // FlashContext lookup
+    public abstract ToolResponse call(ToolArguments args) throws Exception;  // hot path
+}
+```
+
+`McpResource` (`read()`) and `McpPrompt` (`render(PromptArguments)`) follow the exact same
+shape. There is deliberately no CDI-style `@Inject` and no method-per-tool bean class — Flash5
+handlers are classes, and MCP features follow that convention.
+
+## Declaring metadata
+
+Metadata (name, description, input schema) lives entirely in the annotation, not in reflected
+method signatures — the whole JSON Schema is known at scan time and compiled once:
+
+```java
+@Tool(
+    name = "get_weather",
+    description = "Get current weather for a city",
+    args = {
+        @ToolArg(name = "city", description = "City name", required = true),
+        @ToolArg(name = "days", type = ToolArgType.INTEGER, description = "Forecast horizon")
+    }
+)
+public class GetWeatherTool extends McpTool {
+    @Override
+    public ToolResponse call(ToolArguments args) {
+        String city = args.getString("city");
+        int days = args.getInt("days", 1);
+        ...
+    }
+}
+```
+
+`ToolArgType` maps directly to JSON Schema primitive types: `STRING`, `INTEGER`, `NUMBER`,
+`BOOLEAN`, `OBJECT`, `ARRAY`. Nested object/array schemas beyond the primitive type keyword are
+not modeled in this revision — declare those tools with a looser `OBJECT`/`ARRAY` type and parse
+the raw shape via `ToolArguments.raw(name)`.
+
+`ToolArguments`/`PromptArguments` are thin typed accessors over the already-parsed JSON — no
+databinding, no reflection, no intermediate DTO:
+
+```java
+args.getString("city");
+args.getInt("days", 1);
+args.getBoolean("metric", true);
+args.raw("filters");   // escape hatch: JsonNode for nested/array arguments
+```
+
+## Discovery
+
+`McpConfig.toolsPackage("com.example.tools")` scans that package (and subpackages) for concrete
+`McpTool`/`McpResource`/`McpPrompt` subclasses carrying `@Tool`/`@Resource`/`@Prompt`. Same
+fail-fast contract as `FlashApp.scan()`: missing package, missing no-arg constructor, or a class
+that fails to load aborts startup immediately with a clear message. Duplicate names/URIs also
+fail fast at boot.
+
+## Resources and Prompts
+
+```java
+@Resource(uri = "config://app-settings", description = "Application settings", mimeType = "application/json")
+public class AppSettingsResource extends McpResource {
+    @Override
+    public ResourceContents read() {
+        return TextResourceContents.of(uri(), "application/json", settingsJson());
+    }
+}
+
+@Prompt(name = "summarize", args = @PromptArg(name = "text", required = true))
+public class SummarizePrompt extends McpPrompt {
+    @Override
+    public PromptMessage render(PromptArguments args) {
+        return PromptMessage.withUserRole(new TextContent("Summarize: " + args.getString("text")));
+    }
+}
+```
+
+`McpResource.uri()` returns the URI declared on `@Resource`, cached at bind time — no repeated
+annotation lookups on the hot path.
+
+## Content types
+
+`Content` and `ResourceContents` are `sealed`, currently permitting only `TextContent` and
+`TextResourceContents` respectively. This is a deliberate v1 scope cut, not an oversight — image
+content, embedded resources, and blob resources are extension points for a future revision
+(extend the `permits` clause and `McpContentWriter`).
+
+## Tool failures vs. protocol errors
+
+A `McpTool.call(...)` that throws is caught by the dispatcher and turned into
+`ToolResponse.error(message)` — per the MCP specification this is a normal JSON-RPC *result*
+with `isError: true`, not a JSON-RPC error, so the calling model can see and react to it. Prefer
+returning `ToolResponse.error(...)` explicitly when you can produce a better message than the
+raw exception text.
+
+`McpResource.read()`/`McpPrompt.render(...)` failures, by contrast, surface as JSON-RPC errors
+(`-32603 Internal error`) — the specification does not define a soft-failure content convention
+for those two.