feat(core): add HTTP/2 performance gates

flash/docs/http2/IMPLEMENTATION-PLAN.md

@@ -78,7 +78,7 @@ Status values: `not started` / `in progress` / `blocked` / `done`.
 | 14 — h2c prior knowledge + proxy support | done | `feature/core/http2` | Independent TLS/h2c gates, pooled proxy-oriented h2 client with TLS ALPN and h2c, bidirectional h1/h2 trailer relay, shared four-direction hop-by-hop policy and certificate-backed 421 handling complete. Real grpcurl h2c interop passes. 670/670 tests green from a clean `-Pjmh` build. |
 | 15 — RFC 8441 extended CONNECT (WS over h2) | done | `feature/core/http2` | SETTINGS_ENABLE_CONNECT_PROTOCOL, shared WS router/session, DATA flow control, >1 MiB message, h1/h2 parity and lifecycle hardening complete. EX-52/53 fixed; DEC-32 recorded. 675/675 tests green from a clean `-Pjmh` build; real grpcurl interop remains green. |
 | 16 — Compliance test suite | done | `feature/core/http2` | h2spec 2.6.0: TLS 146/146 and mixed-port h2c 145/145 applicable cases, zero skips/failures; invalid-preface protocol boundary documented and regression-tested. Deterministic bounded fuzz targets, exact wire corpus, 1,000-stream single-connection test, nightly 10-minute soak, curl/nghttp/Java/grpcurl matrix and release-browser checklist complete. EX-54–56 fixed; DEC-33/34 recorded. Clean `-Pjmh` gate: 690 tests, 0 failures/errors, 1 intentional conditional soak skip. |
-| 17 — Benchmarks, allocation gates, tuning | not started | — | — |
+| 17 — Benchmarks, allocation gates, tuning | done | `feature/core/http2` | Forked JMH allocation and true sampled-p99 gates wired into CI; h1/h2/frame/HPACK/body/multiplexing/writer coverage complete. Reconstructed Phase-0 h1 baseline: 1,024.602 ns now vs 976.195 ns then with overlapping 99.9% CIs, and 0.007 vs 224.007 B/op. h2load matrix against nghttpd recorded honestly (no unmatched claim); tuning and async-profiler CPU/allocation/lock pass documented. EX-57/58 and DEC-35/36 recorded. Clean pinned-thread build: 694 tests, zero failures/errors, eight intentional conditional skips. |
 | 18 — Documentation | not started | — | — |
 
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@@ -855,6 +855,25 @@ connection `PROTOCOL_ERROR`. **Fix**: preface verification now distinguishes mat
 and invalid input; invalid input sends GOAWAY. The exact 24 bytes are in the regression corpus.
 **Phase**: 16.
 
+### EX-57 — Wire-closed streams occupied the live concurrency table until their final write callback
+
+Found by the Phase 17 h2load matrix at the advertised 64-stream concurrency. A response stream
+could be closed in protocol state while its final immutable write batch was still owned by the
+serialized writer. Keeping that object in the live table made a legal replacement stream receive
+`REFUSED_STREAM`; recycling it immediately would instead corrupt the pending write callback.
+**Fix**: detach a closed stream from live lookup before submitting its final batch, retain bounded
+object ownership until the callback, and cap live plus detached objects at twice the advertised
+live capacity. The regression test fills a one-entry table, detaches its final generation, admits
+the next stream, and proves both objects return to the pool. **Phase**: 17.
+
+### EX-58 — The upstream HTTP/2 client left Nagle enabled on synchronous exchanges
+
+Found while building the Phase 17 end-to-end benchmark. The proxy-oriented client sends small
+request and control frames and then synchronously waits for the response; with Nagle enabled this
+interacted with delayed ACKs and added roughly 40 ms to a local exchange. **Fix**: configure
+`TCP_NODELAY` on both cleartext and TLS sockets before protocol exchange. A socket-option
+regression test covers the shared configuration method. **Phase**: 17.
+
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 # PART III — The phases
@@ -3122,11 +3141,14 @@ decisions and the rejected ones. Every claim in the project's marketing about pe
 be traceable to a number in this file.
 
 ### DoD
-- [ ] Allocation gates green in CI and wired to fail the build.
-- [ ] Latency baselines recorded.
-- [ ] h1 performance is not worse than the pre-Phase-1 baseline.
-- [ ] No carrier pinning anywhere.
-- [ ] `flash/docs/http2/PERFORMANCE.md` complete with the comparison against a reference server.
+- [x] Allocation gates green in CI and wired to fail the build.
+- [x] Latency baselines recorded in `BASELINES.md`; CI reads JMH's actual `p0.99` secondary
+      result, not iteration-mean statistics.
+- [x] h1 performance is not statistically worse than the reconstructed pre-Phase-1 baseline:
+      the 99.9% confidence intervals overlap, while allocation falls from 224.007 to 0.007 B/op.
+- [x] No carrier pinning anywhere — full 694-test clean run with
+      `-Djdk.tracePinnedThreads=full`, zero pinning events.
+- [x] `flash/docs/http2/PERFORMANCE.md` complete with the comparison against nghttpd.
 
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