# Issue #838 — Broker acceptance socket flake

## Objective

Eliminate high-contention uncaught JSON parse failures in lease-broker and mutator-gate acceptance helpers without laundering malformed/empty replies into passing assertions.

## Constraints

- Branch: `fix/838-broker-acceptance-flake` in `/home/hermes/agent-work/stack-838-flakefix`.
- Red-first TDD with a forced empty/truncated reply path and deterministic rejection or documented retry.
- Read newline-framed replies completely; reject malformed broker replies with byte length/content context.
- Determine RIDER2 branch before finalizing: test-harness-only `(a)` or daemon write truncation `(b)`.
- If product-side, prove the real Claude/Pi adapter read path fails closed; fix any allow-risk.
- Coverage >=85% per changed executable through real tests.
- Full suite and repository gates green; independent exact-head review required.
- Push and open a PR containing `closes #838`; do not merge.

## Progress

- 2026-07-17: Reclaimed from #824. Confirmed clean worktree on `fix/838-broker-acceptance-flake` at main base `abd2791f59b3f06f46dd08e55298ced72f6aa7c2`.
- RED evidence: after dependency setup, `broker-test-client.spec.ts` failed to load the intentionally absent shared client module. Its contract forces empty-close retry, repeated truncated-close rejection with byte context, and newline-terminated malformed-reply rejection.
- RIDER2 verdict: branch **(b)**. `daemon.py` starts one connection deadline before request reading, then may spend that budget waiting for `broker_lock`; after handling, `remaining <= 0` returns without writing. A timed `sendall` failure can likewise close after a partial write. A deterministic socketpair probe held the lock past `CONNECTION_DEADLINE_SECONDS` and observed `deadline_probe_reply_length=0`.
- Adapter tripwire: real subprocess executions of `mutator-gate.py` for both `--runtime claude` and `--runtime pi` against actual Unix servers returning empty and truncated replies all exited 2 with `GATE_UNAVAILABLE`. Adapter fail-close is proven; there is no ALLOW risk.
- Residual: production broker reply loss remains an availability-denial path under extreme contention, but cannot grant mutator authority. The acceptance-only client retries early closes and otherwise rejects with response byte length, escaped bytes, and hex; malformed newline-framed replies are never retried or converted to reply objects.
- Shared client now owns newline framing and parsing for both acceptance suites. Focused suites pass 60 tests, including the real adapter tripwire.
- Coverage gate: changed helper is 100% statements/lines/functions and 90% branches; existing `skill.ts` remains above 85% per-file thresholds.

## Scope corrections and bounded product repair

- Coordinator correction superseded the initial push/PR and retry language: this lane is BUILD-ONLY, and early-close retries are forbidden because they can mask a committed broker transaction. Nothing may be pushed or opened until explicitly cleared.
- Revised RED evidence: the no-retry empty/truncated tests failed because the first failed exchange was retried into `{ ok: true }`; the daemon regression failed because a slow completed `broker.handle()` produced `b''` instead of a newline-framed reply.
- Client repair: both former duplicated helpers use one shared reader. Empty, truncated, malformed, oversized, timed-out, and socket-error replies reject `BrokerTransportError` with a typed `kind`, attempt count fixed at one, response length, escaped bytes, and hex. No retry and no catch-to-reply conversion exists.
- Product repair: `daemon.py` now has independent bounded read, broker-lock queue, and send budgets. Lock queue exhaustion returns explicit `BROKER_BUSY` before `broker.handle()` can mutate state. Once handling starts it finishes atomically, and its reply always receives a fresh send timeout instead of being skipped because read/lock/fsync consumed a shared deadline.
- Product GREEN evidence: deterministic socketpair tests prove lock saturation returns framed `BROKER_BUSY` without invoking `handle()`, and a handle that completes after the former one-second shared deadline still returns its complete framed reply.
- RIDER2b remains **fail-closed**: real Claude and Pi `mutator-gate.py` subprocesses against empty and truncated Unix-socket replies exit 2 with `GATE_UNAVAILABLE`; no malformed/default ALLOW was observed.
- Residual/tripwire: an unavoidable peer disconnect or send failure can still lose acknowledgement after a valid transaction commits. The affected adapter call fails closed. A valid `promote_lease` may nevertheless remain VERIFIED after its acknowledgement is lost; that is authority-observability divergence requiring WI-3/Opus security review rather than expansion of #838. #838 does not add retries or attempt a protocol redesign.
- Final package evidence: recursive Mosaic dependency build passed; 73 Vitest files / 1,392 tests passed; deadline unit tests 2/2, real runtime tool tests 15/15, launch guard tests 12/12, inventory 14/14, and shell regressions passed.
- Final coverage: `broker-test-client.ts` 99.24% statements/lines, 86.11% branches, 100% functions under per-file >=85% thresholds. Repository typecheck 42/42, lint 23/23, and format check passed.
- Independent Codex exact-head review requested one framing fix: a valid frame followed by trailing bytes in a later socket chunk could resolve before the garbage arrived. Security review also flagged complete token-bearing reply bodies in diagnostic properties/logs.
- Review RED evidence: delayed cross-chunk garbage resolved `{ ok: true }` instead of rejecting, and a truncated `promotion_token` remained in the typed error. The tests use separate timed writes to prevent kernel/event-loop coalescing.
- Review remediation: the shared client now accumulates through EOF, requires exactly one terminal newline, then parses inside a rejecting error boundary. Diagnostic bodies are capped at 256 bytes, sensitive broker fields are fully redacted, and a SHA-256 digest preserves correlation without credential disclosure.
- Post-review coverage: `broker-test-client.ts` 99.35% statements/lines, 86.66% branches, 100% functions. Final full suite is 73 files / 1,394 tests plus all Python/shell gates; recursive build, typecheck, lint, and format are green.
- Fresh exact-head Codex security review: risk `none`, no findings. Fresh code review found only that the real-adapter subprocess proof lacked a timeout; it now has a five-second bound and fails with runtime/wire context while closing the fake server. The focused Python suite remains 15/15 green.
- Mandatory Opus SECREV remains coordinator-owned and pending before any push/PR decision; this build is intentionally local-only.
