fix(proxy): clear expired retry cooldown transitions

[JustYannicc]

Problem

A durable retry-circuit cooldown that expired after being loaded could leave a stale positive monotonic deadline in local state. Admission interpreted that expiry as a half-open transition and consumed the exclusive probe lease, suppressing later requests. A transient lookup failure could also create that probe lease; a subsequent same-version expired row cleared only the cooldown and left the lease active.

What this fixes

Expired durable cooldowns now clear equal-version stale local cooldown and half-open deadlines when no newer local failure exists. Newer local failures and newer persisted state remain authoritative.

What is now possible

After a persisted cooldown expires, including recovery from a transient lookup failure, ordinary retry admission remains open without creating or retaining a half-open probe lease. Future cooldowns continue to be enforced.

Tests

• 37 retry-circuit tests passed
• Ruff check passed
• Ruff format check passed
• ty check passed
• Proxy architecture checks passed
• Strict OpenSpec validation passed: normalize-expired-retry-cooldown
• git diff --check passed

Dependencies

Based directly on beta.4 upstream main b311aea. No dependency on PR #1867; the branches are independent. This PR changes only retry-circuit state merge logic and its regression tests.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 6a9026a6-70c2-4946-84dd-f428862e5d13

📥 Commits

Reviewing files that changed from the base of the PR and between b311aea and 32cf3aa.

📒 Files selected for processing (6)

• app/modules/proxy/_service/http_bridge/retry_circuit.py
• openspec/changes/normalize-expired-retry-cooldown/.openspec.yaml
• openspec/changes/normalize-expired-retry-cooldown/proposal.md
• openspec/changes/normalize-expired-retry-cooldown/specs/responses-api-compat/spec.md
• openspec/changes/normalize-expired-retry-cooldown/tasks.md
• tests/unit/test_proxy_http_bridge.py

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📝 Walkthrough

Walkthrough

The retry circuit now restores elapsed or absent durable cooldowns as an open state with no cooldown or half-open lease. Equal-version reloads clear stale local deadlines. Specifications and unit tests document and verify the behavior.

Changes

Retry cooldown normalization

Layer / File(s)	Summary
Cooldown normalization contract openspec/changes/normalize-expired-retry-cooldown/*	The specification defines zero cooldown handling for absent or elapsed durable cooldowns. Future cooldowns remain enforced.
Retry-circuit state reconciliation app/modules/proxy/_service/http_bridge/retry_circuit.py	State loading maps elapsed cooldowns to 0.0. Equal-or-newer records without active cooldowns clear stale local deadlines.
Cooldown expiry regression coverage tests/unit/test_proxy_http_bridge.py	Tests verify expired cooldown restoration, expiry cleanup, repeated admission, and the absence of unnecessary half-open leases.

Estimated code review effort: 2 (Simple) | ~15 minutes

Merge Risk: ⚪ Minimal · up to 32cf3

This localized change clears expired retry cooldown state while preserving newer failures and persisted state; the supplied checks pass, and no actionable merge-blocking risk remains beyond normal review.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	Docstring check was indeterminate for this PR — some files could not be analyzed in time. Not blocking.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main change: clearing expired retry-circuit cooldown transitions in the proxy.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[JustYannicc]

Follow-up on the expiry-transition review: commit ed8ee12 also clears a stale half-open lease when an equal-or-newer expired durable snapshot arrives after a transient lookup failure. Added regression coverage for future row -> lookup failure/lease -> same-version expired row. The branch is based directly on beta.4 main b311aea; no #1867 dependency. Affected gates pass: 37 retry-circuit tests, Ruff, format, ty, architecture, diff check, and strict scoped OpenSpec.