fix(proxy): allow prefix-settled replay outputs

[Komzpa]

Consolidated into Soju06/codex-lb PR 2088, which includes the prefix-settled tool-output replay change and its tests/spec alongside the bridge recovery that consumes it. The original patch content is retained. Closing this duplicate review surface.

[chatgpt-codex-connector]

Codex Review Summary

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-09-04T22:06:34.084812Z	52d3b5b	Manual request

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[Komzpa]

@codex review

[coderabbitai]

📝 Walkthrough

Walkthrough

The replay proof now accepts output-only suffixes that settle pending direct tool calls in a verified prefix. It rejects orphan, duplicate, malformed, response-owned, and unexpected tool-call items while preserving exact-manifest validation for fresh replays.

Changes

Prefix-settled replay certification

Layer / File(s)	Summary
Replay contract and change specification openspec/changes/allow-prefix-settled-tool-output-replay/*	The OpenSpec change defines output-only suffix settlement, rejection cases, scenarios, ownership metadata, and completed validation tasks.
Fail-closed replay validation app/modules/proxy/replay_safety.py	responses_input_suffix_matches_pending_tool_calls separates pending-prefix and fresh-suffix validation. It validates output fields, nonblank call_id values, duplicate IDs, and manifest matches.
Replay safety regression coverage tests/unit/test_replay_safety.py	Tests cover successful prefix settlement and rejection of orphan, duplicate, response-owned, and missing-call-ID outputs.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Sequence Diagram(s)

sequenceDiagram
  participant StoredPrefix
  participant ReplayValidator
  participant PendingToolManifest
  participant FreshSuffix
  StoredPrefix->>ReplayValidator: provide prefix state
  ReplayValidator->>PendingToolManifest: compare pending calls
  FreshSuffix->>ReplayValidator: provide tool outputs or fresh calls
  ReplayValidator-->>FreshSuffix: return replay proof result

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Merge Risk: 🟡 Moderate · up to e8ca8

Prefix-settled replay can currently accept incomplete or malformed tool outputs for a pending call, weakening fail-closed replay certification. Validate output content and metadata before merging.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 16.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files. (4 skipped: 4…	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
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 and concisely describes the main change: allowing replay outputs that settle pending calls in the stored prefix.

Full details: Docstring Coverage

Explanation

Docstring coverage is 16.67% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 6 functions across 2 files. (4 skipped: 4 unsupported.)

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Actionable comments posted: 1

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Inline comments:
In `@app/modules/proxy/replay_safety.py`:
- Line 460: The prefix-settling validation around the field-name check must also
validate each tool output’s value and metadata before accepting it. Apply
_tool_output_is_self_contained and
_internal_chat_message_metadata_is_account_neutral in this branch, preserving
valid self-contained outputs while rejecting missing or malformed output content
and internal metadata; add regression coverage for those cases.

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Team

Run ID: bde37d82-104e-41cf-bc65-d367cb686c91

📥 Commits

Reviewing files that changed from the base of the PR and between dd28d7d and e8ca86f1bcb597cbd271f94d10671772ef5e5183.

📒 Files selected for processing (6)

• app/modules/proxy/replay_safety.py
• openspec/changes/allow-prefix-settled-tool-output-replay/.openspec.yaml
• openspec/changes/allow-prefix-settled-tool-output-replay/proposal.md
• openspec/changes/allow-prefix-settled-tool-output-replay/specs/responses-api-compat/spec.md
• openspec/changes/allow-prefix-settled-tool-output-replay/tasks.md
• tests/unit/test_replay_safety.py

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[chatgpt-codex-connector]

💡 Codex Review

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Reviewed commit: e8ca86f1bc

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[Komzpa]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Keep them coming!

Reviewed commit: 52d3b5bcea

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[Soju06]

Thanks for splitting this out with a spec delta as requested on #1881. CI is green on 52d3b5b, the Codex/CodeRabbit threads are addressed, and the branch still merges cleanly against current main (no overlap with the R19 merges so far). Three things block merge:

1. The raw response-owned-ID guard is bypassable for Responses-Lite prefixes. responses_input_suffix_has_response_owned_prefix_settling_output_ids (app/modules/proxy/replay_safety.py:471) calls _direct_tool_call_prefix_state without the projection's canonical_lite_developer_index; both call sites (app/modules/proxy/_service/http_bridge/streaming.py:402 and :1575) pass nothing. For a stored prefix [additional_tools bundle, canonical developer message, user, function_call call-1] the prefix walk returns None on the developer message, the guard returns False, and both callers fall through to the projected path where project_responses_input_for_account_neutral_fresh_replay strips the output id before the prefix-settled proof runs. Reproduced on this head: _verify_durable_full_resend returns a proof for suffix [{"type": "function_call_output", "id": "fc_output_response_owned", "call_id": "call-1", "output": "result"}] with that Lite prefix and manifest {"call-1": "function_call"}. That is exactly the shape the new requirement says MUST fail, and test_verified_durable_full_resend_rejects_response_owned_prefix_settling_output_id (tests/unit/test_proxy_http_bridge.py:14106) only covers the non-Lite prefix. Either thread canonical_lite_developer_index from the classification projection into the raw guard (compute the projection first, then run the guard on the raw items with its index), or check the IDs on the raw suffix items directly without re-walking the prefix. Please add the Lite-prefix regression in both test_replay_safety.py and the _verify_durable_full_resend test.

2. Reachability of the admitted shape is not shown. The durable manifest is built from response output items (_durable_pending_tool_call_manifest, app/modules/proxy/_service/http_bridge/upstream_events.py:976, registered at :3704), while latest_input_item_count/latest_input_full_fingerprint are that same request's input, and all three are written together per response id in register_owned_alias (app/modules/proxy/durable_bridge_repository.py:3625-3661, replaced whenever the response id changes). Under normal upstream behavior a manifest call therefore cannot already be pending inside its own fingerprint-verified prefix; the proposal's "can force owner-bound recovery" has no trigger attached. Since this loosens a fail-closed certification (flagged as risk-sensitive on fix(http-bridge): expire stale inflight creations #1881), please document the concrete client sequence or log that produces prefix_pending == manifest, ideally as a bridge-level test that fails on main for that sequence, not only the helper-level responses_input_suffix_matches_pending_tool_calls cases.

3. Spec delta should be MODIFIED, not ADDED. openspec/specs/responses-api-compat/spec.md:4782 ("Historical output remains mandatory": matching output missing -> exact manifest proof fails), under the requirement at :4717, conflicts with the new requirement when the missing output arrives in the suffix. Please express this as a MODIFIED delta on that requirement so the two readings are reconciled instead of coexisting.

Minor: the exact-manifest path on main still relies on projection to strip output ids, so the new raw guard enforces the property only in prefix-settled mode. If the property matters, it should apply to both modes; if it does not, the ~40-line guard plus two call sites can go.

[Soju06]

Status check on 52d3b5b (unchanged since 09-04): the three points from the 09-05 comment are still open, and I re-verified them against current main (e987c56, which includes this round's merges). The branch still merges cleanly (0 conflicts on the merge tree) and lint/architecture guards pass, so no rebase is needed — the fixes below are all that stands between this and merge. The "codex: ok" label does not clear them; Codex reviewed the non-Lite shape only.

1. Lite-prefix bypass, reproduced again on the merged tree. With stored prefix [additional_tools bundle, {"type":"message","role":"developer",...}, user, function_call call-1], manifest {"call-1": "function_call"} and suffix [{"type":"function_call_output","id":"fc_output_response_owned","call_id":"call-1","output":"result"}], _verify_durable_full_resend returns a proof, while the same suffix on the plain prefix is correctly rejected. Cause: the new responses_input_suffix_has_response_owned_prefix_settling_output_ids (app/modules/proxy/replay_safety.py) accepts canonical_lite_developer_index but both call sites in app/modules/proxy/_service/http_bridge/streaming.py (_VerifiedDurableFullResend, ~L402, and the classification path, ~L1575) call it with only stored_count/pending_tool_calls. _direct_tool_call_prefix_state then sees occupies_canonical_lite_position=False at index 1, historical_interleave_is_bounded needs len(pending_calls) == 1 while pending is still empty, the walk returns None, the guard returns False, and control falls through to the projected input where project_responses_input_for_account_neutral_fresh_replay has already stripped the id. Concrete fix: compute the projection first (as main already does) and pass replay_projection.canonical_lite_developer_index into the raw guard — the index is anchored on the original position (bundle at 0 and developer message at 1 both survive projection), so it is valid against the raw items. Alternatively drop the prefix re-walk from the guard and simply check "id" in item on raw suffix outputs whose call_id is in the manifest. Please add the Lite-prefix regression next to test_verified_durable_full_resend_rejects_response_owned_prefix_settling_output_id in tests/unit/test_proxy_http_bridge.py and a matching case in tests/unit/test_replay_safety.py.

2. Reachability is still unshown. _durable_pending_tool_call_manifest (app/modules/proxy/_service/http_bridge/upstream_events.py:972) is built from the response's output items and is written together with latest_input_item_count/latest_input_full_fingerprint for the same response id in register_owned_alias (app/modules/proxy/durable_bridge_repository.py), so a manifest call cannot normally already sit inside its own fingerprint-verified prefix. Since this loosens a fail-closed certification, please attach the concrete client sequence (or a bridge-level test that fails on main) that produces prefix_pending == manifest.

3. openspec/changes/allow-prefix-settled-tool-output-replay/specs/responses-api-compat/spec.md is still ## ADDED Requirements; it conflicts with the existing scenario "Historical output remains mandatory" at openspec/specs/responses-api-compat/spec.md:4801 on current main. Please express it as a MODIFIED delta on that requirement.

Note: #2084 and #2088 (both still open) touch the same streaming.py/test_proxy_http_bridge.py regions; whichever lands first will need the other rebased. None of the PRs merged this round conflict with this branch.