fix(http-bridge): classify recovery error frames and poison same-anchor eventless failures

[Soju06]

Root cause

Two gaps combined into the permanent "cooling down" 503 wedge documented in #1830 (the acknowledged P3 follow-up from #1818's merge notes):

1. Bridge-local recovery gate reads raw error codes. _http_bridge_should_attempt_local_previous_response_recovery (app/modules/proxy/_service/http_bridge/helpers.py) classified on error.get("code") without the _normalize_error_code(code, type) fallback the WebSocket rewrite path gained in fix(proxy): classify parameterless previous response errors #1818. A classifiable upstream previous-response rejection whose code rides only in type — or the terse parameterless Invalid `previous_response_id`. frame — fell through to the ambiguous-transport class, so the failure fed the retry circuit instead of anchored recovery.
2. Anchor poison never counted the wedge's failure class. Poisoning only triggered on stream_idle_timeout, and only on the reader path when admission waiters exist (upstream_events.py). The observed wedge fails eventlessly with stream_incomplete (the bridge's masked form of an upstream previous-response rejection on bridge request states, which never set expose_stale_previous_response_classifier), and the wedge loop retires through the shared retirement boundary (_retire_stale_pending_http_bridge_session), which recorded circuit strikes but discarded the count. Result: http_responses_session_bridge_anchor_poison_failure_threshold (default 7) never fired, the circuit cooled down forever, and only wiping the http_bridge_* tables freed sessions.

Fix

• Normalize the error code (falling back to type) in the bridge-local recovery gate before all classification checks — same normalization convention as _http_bridge_is_context_overflow_error directly below it and the WS path from fix(proxy): classify parameterless previous response errors #1818.
• Map both ambiguous eventless transport classes (stream_incomplete, and stream_idle_timeout incl. its aliases) to anchor-poison details (retry_circuit.py: _http_bridge_anchor_poison_detail); clean_close never triggers poison.
• Widen the deferred reader-path poison branch to both classes and thread the poison detail through durable_anchor_poisoned / durable_anchor_poison_clear_failed observability.
• Evaluate the poison threshold at the shared retirement boundary too, clearing the poisoned durable anchor while the session still owns its durable lease, so a wedged anchored session failing without admission waiters also self-heals. A clear that cannot be confirmed is re-attempted on the next eligible eventless failure at/above the threshold.

Same-anchor justification: the durable anchor only advances on a completed response, which resets the retry circuit — so N consecutive circuit failures on one bridge key prove the anchor never advanced.

OpenSpec

openspec/changes/classify-bridge-recovery-error-frames/ (modifies responses-api-compat): gate normalization requirement + widened anchor-poison requirement. openspec validate classify-bridge-recovery-error-frames --type change --strict passes.

Note on poison-count composition: the threshold intentionally reuses the existing shared circuit counter (same as the pre-existing stream_idle_timeout poison branch). A run mixed with clean_close strikes can therefore reach the threshold with fewer eventless failures, but only an eligible eventless failure can trigger the clear, the same-anchor invariant holds regardless of class mix (the counter resets on any completed response), and a false-positive clear costs one full-history resend versus the permanent wedge it prevents.

Test evidence (RED → GREEN)

New regressions, all failing on main (d148dd9) and passing on this branch:

Test	On main	Here
test_http_bridge_should_attempt_local_previous_response_recovery_normalizes_upstream_error_frames (terse parameterless + type-only frames)	FAIL (assert False is True)	pass
test_stream_via_http_bridge_recovers_terse_previous_response_rejection (product path: anchored bridge stream, terse rejection → local recovery + retry succeeds)	FAIL (raw 400 propagates)	pass
test_http_bridge_repeated_zero_event_stream_incompletes_poison_anchor_with_waiter	FAIL (never poisons)	pass
test_http_bridge_retire_stale_pending_poisons_anchor_after_repeated_eventless_failures (waiterless boundary)	FAIL (rebind never awaited)	pass
test_http_bridge_retire_stale_pending_reattempts_failed_poison_clear	FAIL (0 clears)	pass
test_http_bridge_retire_stale_pending_clean_close_never_poisons_anchor (guard)	pass	pass

Suites: tests/unit/test_proxy_http_bridge.py + tests/unit/test_proxy_utils.py → 1755 passed, 1 failed (test_stream_via_http_bridge_fails_closed_before_file_affinity_when_previous_response_owner_misses — pre-existing, fails identically on unmodified main in this environment). tests/integration/test_http_responses_bridge.py → 131 passed. ruff check / ruff format --check / ty check clean.

Local codex review --base origin/main raised three P2s, addressed as follows: product-path regression added for the gate (test_stream_via_http_bridge_recovers_terse_previous_response_rejection), failed-clear re-attempt covered by test + spec, and clean-close count composition documented above (pre-existing shared-counter semantics of the deferred poison branch, trigger-gated by class).

Issue cover

Fixes #1830

The second, independent deadlock reported there (operation_already_recorded_no_status_proof — ghost ledger operation with no status proof) is not addressed by this PR; it remains a follow-up. This PR removes the primary wedge (misclassification + unreachable poison threshold) that produced the cooldown loop.

@kvz you offered to test — this branch is fix/bridge-recovery-error-classification. Your logged wedge shape (sub-second stream_incomplete with all-None diagnostics on the same anchor) should now self-heal at http_responses_session_bridge_anchor_poison_failure_threshold consecutive failures (default 7) and classifiable rejections should route into recovery instead of the circuit; we'd love confirmation from your setup with the bridge re-enabled.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Improved recovery from upstream errors with alternate classification fields and terse rejection messages.
  • Improved handling of repeated incomplete or idle bridge streams, including durable connection cleanup.
  • Prevented cleanly closed connections from being incorrectly marked as poisoned.
  • Added retries and telemetry when durable connection cleanup initially fails.

• Tests

  • Added coverage for error recovery, stream failures, connection poisoning, cleanup retries, and clean closures.

• Documentation

  • Added specifications and implementation tasks describing bridge recovery and continuity behavior.

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📝 Walkthrough

Walkthrough

The HTTP bridge now normalizes upstream recovery errors, recognizes terse previous-response rejections, and classifies repeated eventless incomplete or idle-timeout failures as durable-anchor poisoning. Retirement clears poisoned anchors, retries failed clears, and preserves clean-close immunity.

Changes

HTTP bridge recovery and anchor poisoning

Layer / File(s)	Summary
Recovery error classification app/modules/proxy/_service/http_bridge/helpers.py, tests/unit/test_proxy_utils.py, tests/unit/test_proxy_http_bridge.py, openspec/changes/classify-bridge-recovery-error-frames/...	Recovery classification trims code and type, falls back to type, and recognizes parameterless previous_response_id rejection frames. Tests cover local recovery and stream replay.
Anchor poisoning and retirement app/modules/proxy/_service/http_bridge/retry_circuit.py, app/modules/proxy/_service/http_bridge/request_submit.py, app/modules/proxy/_service/http_bridge/upstream_events.py, tests/unit/test_proxy_http_bridge.py, openspec/changes/classify-bridge-recovery-error-frames/specs/responses-api-compat/spec.md	stream_incomplete and stream_idle_timeout can classify as poison details. Threshold evaluation now clears durable anchors during waiter and waiterless retirement, retries failed clears, and excludes clean_close.

Estimated code review effort: 4 (Complex) | ~45 minutes

Merge Risk: ⚪ Minimal · up to d9c1c

The PR narrowly improves recovery classification and anchor cleanup behavior, with reported regression coverage and passing checks; no actionable merge-blocking risk remains after normal checks and review.

Sequence Diagram(s)

sequenceDiagram
  participant HTTPBridge
  participant RetryCircuit
  participant DurableAnchor
  participant StaleSession
  HTTPBridge->>RetryCircuit: record eventless stream failure
  RetryCircuit-->>HTTPBridge: return poison detail at threshold
  HTTPBridge->>DurableAnchor: abandon continuity anchor
  HTTPBridge->>StaleSession: retire with classified detail

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Possibly related PRs

• Soju06/codex-lb#1818: Extends its error-code normalization and parameterless previous_response_id classification into HTTP bridge recovery.
• Soju06/codex-lb#1817: Addresses the same terse previous_response_id rejection recovery path.
• Soju06/codex-lb#1736: Directly relates to HTTP bridge retry and retirement behavior for repeated eventless failures.

Suggested reviewers: komzpa, mastertyko, leventov

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the recovery-frame classification and same-anchor eventless-failure handling changes.
Linked Issues check	✅ Passed	The changes address error normalization, recovery classification, anchor poisoning, waiterless retirement, clear retries, and required observability for #1830.
Out of Scope Changes check	✅ Passed	The implementation, tests, and OpenSpec updates remain focused on the linked issue objectives without unrelated code changes.

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Inline comments:
In `@app/modules/proxy/_service/http_bridge/request_submit.py`:
- Around line 2855-2875: After _abandon_durable_http_bridge_continuity returns
False for a session with durable continuity in the waiterless retry path, emit
the durable_anchor_poison_clear_failed event, matching the existing
admission-waiter path telemetry. Preserve the current warning and only add the
event for failed durable-anchor clears.

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📒 Files selected for processing (10)

• app/modules/proxy/_service/http_bridge/helpers.py
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• app/modules/proxy/_service/http_bridge/retry_circuit.py
• app/modules/proxy/_service/http_bridge/upstream_events.py
• openspec/changes/classify-bridge-recovery-error-frames/.openspec.yaml
• openspec/changes/classify-bridge-recovery-error-frames/proposal.md
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