fix(openai-chat): tolerate null tool-call padding

[dbc-hbin]

Summary

• Treat explicit tool_calls: null as an absent optional field in streamed and buffered OpenAI-compatible responses.
• Preserve the fail-closed validation introduced for malformed non-null containers and entries in [Bug] Nested field shapes bypass the #1219 frame guard and crash both adapter paths #1325.
• Add focused regression coverage for both response modes.

This restores compatibility with providers that use null as padding when no tool call is present, without accepting malformed claimed tool-call payloads.

Verification

• bun test tests/openai-chat-hardening.test.ts
• bun run typecheck
• bun run test
• bun run privacy:scan

No documentation change is needed because this is an internal adapter compatibility correction with no configuration or public API change.

Checklist

• Scope stays focused and avoids unrelated cleanup.
• Docs or release notes were updated when needed.
• Security-sensitive changes were reviewed for secrets, auth, and unsafe defaults.

Review readiness checklist

This PR stays in draft until every box below is ticked. Tick all four boxes once the requirements are met:

• All CI tests are green on my local testing.

• I pushed my PR to the latest dev commit.

• I resolved all correct Codex and CodeRabbit findings.

• My PR is ready for review.

Summary by CodeRabbit

• Bug Fixes
  • Improved handling of OpenAI chat responses where tool-call data is null.
  • Text output and completion usage are now preserved without unnecessary errors.
  • Malformed, non-null tool-call data continues to be reported appropriately.

[coderabbitai]

Important

Review skipped

No new commits to review since the last review.

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: ASSERTIVE

Plan: Pro Plus

Run ID: 76485066-f73d-4bf7-8932-1e94df78112b

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

Use the checkbox below for a quick retry:

• 🔍 Trigger review

📝 Walkthrough

Walkthrough

The OpenAI Chat adapter now treats null tool-call payloads as absent in streaming and non-streaming responses. Hardening tests verify preserved text output, completion usage, and error-free processing.

Changes

OpenAI null tool-call handling

Layer / File(s)	Summary
Handle null tool-call payloads src/adapters/openai-chat.ts, tests/openai-chat-hardening.test.ts	Streaming and non-streaming responses ignore null tool-call payloads. Non-null payloads remain validated, and tests cover text output, completion usage, and error-free completion.

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

Possibly related PRs

• lidge-jun/opencodex#339: Modifies OpenAI Chat response parsing for streaming and non-streaming tool handling.
• lidge-jun/opencodex#1249: Modifies OpenAI Chat streaming payload handling and related tests.
• lidge-jun/opencodex#1332: Modifies OpenAI Chat tool-call payload validation and hardening tests.

Suggested reviewers: lidge-jun, wibias, ingwannu

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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: tolerating null tool-call padding in the OpenAI chat adapter.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}

[github-actions]

✅ Deterministic PR hygiene checks passed.

[github-actions]

✅ READY

• all PR quality gates passed; the review readiness checklist is complete.

Review readiness checklist

• ✅ All CI tests are green on my local testing.
• ✅ I pushed my PR to the latest dev commit.
• ✅ I resolved all correct Codex and CodeRabbit findings.
• ✅ My PR is ready for review.

✅ 4/4 boxes ticked.

This pull request is already Ready for Review.
The review-ready label marks this PR as ready; review automation runs independently. If no CodeRabbit review appears, comment @coderabbitai review to request one.
Maintainers: @lidge-jun @Ingwannu @Wibias

[Ingwannu]

This is a valid, focused compatibility correction. tool_calls: null is an absent optional value in both Chat Completions response modes, while the patch still rejects non-array containers, null array entries, and incomplete claimed calls through the existing fail-closed adapter error path.

I rechecked exact head 53c1f425 on current dev@20c513198:

• nine adjacent OpenAI Chat / Chat Completions suites: 161 passed, 0 failed;
• typecheck: passed;
• privacy scan: passed;
• git diff --check: passed.

The added streaming and buffered regressions cover the intended boundary, and no documentation change is needed for this internal wire-compatibility fix. I did not find a blocker in the diff.

I am not approving or merging while the PR is draft with the readiness checklist at 0/4 and no exact-head full CI. Once the author completes the checklist against this head, current-head automated review has run, and required CI is green, this should be a strong merge candidate.

[coderabbitai]

@github-actions[bot] I will review pull request #1468. The review will check buffered and streamed tool_calls: null handling, malformed non-null validation, and regression-test coverage.

⚠️ Action not completed

Already reviewed.

Note: CodeRabbit is an incremental review system and does not re-review already reviewed commits. This command is applicable only when automatic reviews are paused.

[coderabbitai]

Tip

For best results, initiate chat on the files or code changes.

@github-actions[bot] PR #1468 is marked ready for review. The prior CodeRabbit review request reported that the current commits were already reviewed. No additional review action is required from this status update.

_{You are interacting with an AI system.}