[vadymhimself]

Summary

• A combo child relay binds the turn admission lease to its own controller (registerTurn / trackStreamLifetime) and unbinds it when its stream ends; ActiveTurnLease.unbindAbortController releases the lease once no controller is bound (src/server/lifecycle.ts). When target 1 answered HTTP 200 SSE and then failed before output (response.failed), the combo cancelled that relay, its unbind released the parent's lease, and target 2 was aborted as soon as it bound the settled lease ("turn already settled"), so the client got a 502 although target 2 was healthy.
• handleComboResponses (src/server/responses/core.ts) now binds its own controller to the lease for the whole ladder and unbinds it on return. The accepted child's stream is bound before the ladder returns, so it keeps the lease until the stream ends; a ladder that ends without a bound stream releases it on return, as before. Without a lease nothing is bound or unbound.
• One site rather than a per-delivery-site guard: every combo protocol reaches executeComboResponses only through handleComboResponses, and the child delivery sites keep binding the lease, so drain and maxActiveTurns still see the accepted child's stream.

Verification

• New test a refused child relay does not settle the parent turn's admission lease in tests/server/server-combo-zero-output-failover.test.ts: target 1 streams response.created then response.failed, target 2 completes, with a real tryAdmitTurn() lease. On unmodified upstream/dev 8640c2f: fails (Expected: 200, Received: 502; log shows b/m2 failed with 502 ... upstream_reset right after a/m1). The same test without the lease reaches target 2, which isolates the lease as the cause. With this PR: 9 pass, 0 fail, and the test also asserts getActiveTurnCount() === 0 after the body is read (the lease is released when the accepted stream ends).
• bun test tests/server/server-combo*.test.ts tests/codex-integration/bearer-admission-routed-provider.test.ts (Bun 1.4.3) -> 327 pass, 0 fail.
• bun x tsc --noEmit -> exit 0. bun scripts/file-size-ratchet.ts -> passed. tests/ci-workflows/structure-ssot.test.ts -> 51 pass.
• bun run test:changed (Bun 1.4.3 via OCX_TEST_RUNNER_BUN) -> 15816 pass, 34 skip, 1 fail across 631 files. The single failure, tests/cli/cli-connect-readiness.test.ts "a rejected preferred runtime falls back without rewriting the saved selection", also fails on an unmodified upstream/dev checkout on this machine (local-environment dependent) and is unrelated.
• Full bun run test was not run locally; the remainder is left to CI.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed. (No doc change: the lease contract is described at the change site; structure/transports/responses-failover.md is at its 600-line budget.)
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults. (Admission accounting only; no credentials, auth, or defaults touched.)

Source: carried from the vadymhimself fork build (commits c93bb49, cdd54a8, 23c91b4). The fork suppressed the lease at each child delivery site and re-attached it to the accepted response; on upstream/dev the lease already supports several bound controllers, so holding it at the ladder is the smaller equivalent.

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Summary by CodeRabbit

• Bug Fixes
  • Improved streaming response recovery when an upstream response fails. The request can now succeed using a backup response, while the completed turn is properly cleared afterward. This helps prevent failed attempts from interfering with subsequent requests and ensures response handling remains consistent during failover.

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ℹ️ Recent review info

⚙️ Run configuration

• Configuration used: Repository: lidge-jun/opencodex/.coderabbit.yaml
• Review profile: ASSERTIVE
• Plan: Advanced
• Run ID: d1116ee0-2ed8-43de-8f65-cb2de7c6d574

📥 Commits

Reviewing files that changed from the base of the PR and between 8640c2f and ebda44c.

📒 Files selected for processing: 2

• src/server/responses/core.ts
• tests/server/server-combo-zero-output-failover.test.ts

Included review availability: This review used your included allowance. Your plan provides up to 10 included reviews per hour; 9 remain after this review.

📝 Walkthrough

handleComboResponses now registers and unregisters a turn controller when a lease is provided. A streaming failover test verifies that the backup response succeeds and that no active turns remain.

Changes: Combo turn lifecycle

Layer / File(s)	Summary
Turn lifecycle and failover coverage src/server/responses/core.ts (lines 15, 71–81), tests/server/server-combo-zero-output-failover.test.ts (lines 15, 224–250)	handleComboResponses registers an abort controller with the turn admission lease, awaits combo execution, and unregisters the controller in finally when a lease exists. The streaming failover test checks the backup response and confirms that the active-turn count returns to zero.

Priority: ➖ Normal

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Bug fix

Merge Risk: ⚪ Minimal · up to ebda4

The backup response can complete without the failed child ending its turn lease prematurely. No merge-blocking issue is established.

Pre-merge checks: 4 · 1

Failed checks: 1 warning

Check name	Status	Explanation	Resolution
Docstring Coverage		Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 1 functions across 2 files.	Write docstrings for the functions missing them to satisfy the coverage threshold.

Passed checks: 4 passed

Check name	Status	Explanation
Description Check		Check skipped - CodeRabbit’s high-level summary is enabled.
Title check		The title clearly and concisely describes the main change: preserving the turn admission lease across the combo failover ladder.
Linked Issues check		Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check		Check skipped because no linked issues were found for this pull request.

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[Ingwannu]

Intake/scoped review at ebda44c2a982c2196c6591174fb54a449e5a284d.

Holding the parent lease across the failover ladder addresses a different lifetime from a child response stream. Preserve cancellation and the handoff to the accepted child, with no leaked lease when all children fail. src/server/responses/core.ts is owner-only under CODEOWNERS; keep Draft pending that owner review and CI.

Current-head functional workflows are awaiting fork approval; that is pending execution, not a passing test result. No local suite was run for this branch in this intake. No workflow approval, new scan, live configuration change or merge was performed. Required review/readiness gates remain in force.

[lidge-jun]

Thank you @vadymhimself! This fix is absorbed into #7355 with your commit and authorship intact. Your regression reproduced the 502 on current dev. One follow-up commit there unbinds only a lease that actually registered a controller, which avoids an unmatched unbind on plain admission leases. The maintainer will close this PR when #7355 lands.

[lidge-jun]

Thank you for this fix! It was absorbed into #7355 (merged into dev as 718692b) with your original commits/Co-authored-by credit. Closing in favor of that PR.