[maxmad64bis]

⚠️ base-red inherited: #14547

Summary

The park-and-replay path parks a request for up to 120 s with heartbeat pings, but the stream-readiness guard still cuts the parked response at its stall deadline, surfacing a 502 before the replayed leg arrives. This change marks the synthetic parked response as a transient parked stream and teaches the readiness guard to honor that state, so a parked request resolves directly instead of failing first and retrying.

Related Issues

Related to #13924

Validation

• Change type: other
• Focused tests and category gates from the golden path
• npm run lint
• Reconciled with the current active release base; focused checks rerun afterward
• Production-code changes include a new or updated automated test in this PR

Tests Added Or Updated

• tests/unit/parked-stream-readiness.test.ts (new, 6 cases: marked park with pings resolves instead of 502 RED then GREEN; unmarked pings still 502; marked stream past the ceiling still 504; marker survives a header rebuild and is stripped from the ready response; JSON fallback converts to valid frames; non-convertible 429 fallback surfaces one error data frame with no event: line RED then GREEN).
• Neighbors re-run one by one, all green: tests/unit/stream-readiness.test.ts (21/21), tests/unit/stream-readiness-policy.test.ts (23/23), tests/unit/opencode-429-park-resume.test.ts (8/8).

Coverage Notes

• N/A — no coverage gate movement; new behavior is covered by the new test plus the three neighbor suites above. The non-convertible fallback now emits a single data: error frame (built with the shared error helpers) instead of an event: upstream-status line plus raw text, so the parked stream stays a valid SSE frame sequence.

Reviewer Notes

• Guard thresholds are untouched (80 s stall, 180 s ceiling); only parked responses marked transient suspend the stall deadline, never past the ceiling; outside the park the guard behaves byte-identically (fail-fast fix(streaming): fail fast when an upstream stream produces only lifecycle/heartbeat events, never real content #12741 preserved).
• API Route Typecheck reports 4 diagnostics in open-sse/executors/auggie.ts (TS2769/TS18047) and src/app/api/v1/combos/projectCombo.ts (TS2459/TS2724); both files are unchanged since the merge-base and the same 4 lines fail on same-base PRs test(sse): lock per-key ceiling 429 out of neighbor cooldown scope #14581/fix(sse): serve the stored 429 instead of re-sending refused requests #14588, so inherited via 🔴 Release branch not green: release/v3.8.51 #14547 and non-blocking. Local check:open-sse-typecheck shows only the same auggie.ts errors with zero on touched files.

Recensement (upstream positions)

• fix(sse): park request with heartbeat after repeated transient 429s, replay one capped leg #13924 [merged] park request with heartbeat after repeated transient 429s, replay one capped leg — parent change this PR completes; the parked response it synthesizes is what the guard previously cut.
• fix(streaming): fail fast when an upstream stream produces only lifecycle/heartbeat events, never real content #12741 [merged] fail fast on lifecycle/heartbeat-only streams — preserved outside the park; this PR only suspends the deadline while the parked marker is present.
• No open PR or issue proposes honoring the parked state in the readiness guard: no duplicate found.

[diegosouzapw]

Clean fix closing a real gap left by #13924's park-and-replay. Specifically checked that the
internal marker header never leaks to the client (it's stripped on every response rebuild) and
that the non-convertible fallback goes through the shared buildErrorBody/sanitizeErrorMessage
helpers rather than a raw error string — both confirmed by the test suite, which also passes
clean alongside the rest of this session's stall/buffered-turn batch (no shared files with any
of the other six). No blocking items.