fix(proxy): recover anchored bridge requests after missing response.created

[kevinsslin]

Summary

• recover one hard-owner HTTP Responses continuation when the upstream accepts response.create but never emits response.created;
• reconnect on the same account and resend the unchanged previous_response_id anchor once, before any response/model/downstream output exists;
• keep the existing fail-closed behavior for soft affinity, file-pinned requests, visible/eventful requests, and subsequent failures;
• keep this watchdog recovery budget separate from replay_count, and bypass retry-circuit cooldown only for the narrowly proven eventless same-anchor attempt.

Fixes #1735

Related: #1393, #1394, #1711, #1723.

Why

Stable 1.23.0 still leaves an anchored continuation at the eventless watchdog boundary:

Upstream did not acknowledge response.create before the client-safe deadline
missing_response_created_timeout

The existing generic replay guard correctly rejects ambiguous anchored replays, but it also rejected this narrower state where no upstream response event, model output, or downstream-visible output exists. The request then terminally 502s and the Codex client spends its reconnect budget / pauses the task.

Safety boundary

The new path is opt-in only from the missing-response.created watchdog and requires:

• hard bridge ownership;
• an existing previous_response_id and no assigned response ID;
• awaiting response.created with zero response events;
• no downstream sequence/visible output or upstream model output;
• no account-scoped file requirement;
• at most one watchdog-owned same-anchor attempt.

A replacement socket that is also silent is terminally retired; recovery is not indefinite. Durable operation fencing, account ownership, admission, API-key reservations, and direct WebSocket behavior are unchanged.

OpenSpec

openspec/changes/recover-precreated-anchored-bridge/

Validation

• uv run pytest -q tests/integration/test_http_responses_bridge.py — 129 passed
• uv run pytest -q tests/unit/test_proxy_http_bridge.py — 551 passed
• uv run ruff check app tests — passed
• uv run ruff format --check app tests — passed
• uv run ty check — passed
• uv run python scripts/check_proxy_architecture.py — passed
• npx --yes @fission-ai/openspec@1.9.0 validate recover-precreated-anchored-bridge --strict — valid
• npx --yes @fission-ai/openspec@1.9.0 validate --specs — 57 passed, 0 failed
• git diff --check — passed

No database, environment, public API, or dependency changes. This PR is committed at 1858d95b and pushed, but it is not merged, deployed, or live-verified yet.

[chatgpt-codex-connector]

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