feat(server): define OpenAI Chat contract

[Pouyanpi]

Superseded

This standalone PR is folded into #2413. Its remaining OpenAI source pin, boundary documentation, and provenance tests are already included there; #2413 now targets #2411 directly.

The authoritative Python models remain in #2413. The buffered contract is exported from the endpoint-bound models in #2414 at contracts/openai/_generated/chat-completions.buffered.guard.yaml; it is not a separately maintained YAML policy. Streaming and its contract export remain separate work.

No branch or commits are deleted. The review discussion is preserved. The logprobs, explicit plain-text/no-tools values, conversation-cardinality, and streaming-null questions are linked from #2413 and are not marked resolved by this consolidation.

Revised Stack

The Python projection models and runtime bindings are authoritative. This stack makes their policy explicit through typed declarations and exports a guard contract for inspection and documentation, not runtime configuration or a separately maintained policy.

#2412's remaining provider provenance, boundary documentation, and metadata tests are folded into #2413. Streaming implementation and its contract export are outside this buffered stack.

Review each PR against its parent branch; only #2411 targets develop.

Order	PR	Branch	Base
1	#2411	pouyanpi/guard-contract-foundation-1	develop
2	#2413	pouyanpi/openai-chat-buffered-projections-3	pouyanpi/guard-contract-foundation-1
3	#2414	pouyanpi/openai-chat-buffered-integration-4	pouyanpi/openai-chat-buffered-projections-3

AI Assistance

• No AI tools were used.
• AI tools were used; a human reviewed and can explain every change.

Checklist

• I've read the CONTRIBUTING guidelines.
• This is maintainer-led work tracked internally.
• The PR title follows the project commit convention.
• Applicable documentation and tests are included.
• Generated changelog files were not edited manually.
• Automated and human review comments are addressed or answered.
• The responsible reviewer or team is mentioned.

[greptile-apps]

Confidence Score: 4/5

[Low risk] Documents OpenAI Chat API contract and adds validation test.

The PR is not ready to merge as stacked because the later streaming PR still requires the contract removed here.

Findings

1.  Streaming contract is missing ▶

Fix with agent prompt

### Issue 1
nemoguardrails/server/experimental/contracts/openai/README.md:31-33
This revision removes `chat-completions.guard.yaml` and says the machine-readable contract belongs with the integration, but PR #2435 modifies that file rather than adding it. Its streaming test reads the file directly, so stacking that PR on this head leaves the file missing and the test fails. The buffered export in PR #2414 does not provide the stream section the test needs.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

Summary

The PR pins OpenAI Chat provider-source metadata and documents a narrow single-text boundary, replacing the previously authored operation contract with a descriptive README and offline provenance tests.

• The revised boundary no longer supplies the streaming contract expected by a higher PR in the stack.

_{Reviews (7) · Last reviewed commit: "docs(server): align OpenAI contract docs..." · Reviewed by Greptile}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[tgasser-nv]

Looks good, marking as comment only until the YAML format question in #2411 is answered

[tgasser-nv]

The PR allows logprobs on the request-side but disable the logprobs response from the model. This is true for non-streaming and streaming. Recommend constraining logprobs with const: false and making top_logprobs a null-only disabled gate

[tgasser-nv]

Couldn't Streaming content could be null as well?

[tgasser-nv]

The request projection rejects values that this supports:

• modalities: ["text"] (lines 61-67)
• response_format: {"type": "text"} (88-94)
• tool_choice: "none" (100-106)
• parallel_tool_calls: false (74-80)

Recommend declaring these as constrained with the expected value allowed

[tgasser-nv]

Would this block a request with both system/developer and user entries?

[github-actions]

PR merge guidance

@Pouyanpi thanks for the PR. GitHub is currently blocking merge for one or more repository requirements:

• 1 commit does not have a verified signature (4e59192). Please sign the commits and force-push the updated branch.

Relevant guide:

• Signed commits: https://github.com/NVIDIA-NeMo/Guardrails/blob/develop/CONTRIBUTING.md#commit-signing
• Contribution guide: https://github.com/NVIDIA-NeMo/Guardrails/blob/develop/CONTRIBUTING.md

[greptile-apps]

Streaming contract is missing

This revision removes chat-completions.guard.yaml and says the machine-readable contract belongs with the integration, but PR #2435 modifies that file rather than adding it. Its streaming test reads the file directly, so stacking that PR on this head leaves the file missing and the test fails. The buffered export in PR #2414 does not provide the stream section the test needs.

Prompt To Fix With AI

This is a comment left during a code review.
Path: nemoguardrails/server/experimental/contracts/openai/README.md
Line: 31-33

Comment:
**Streaming contract is missing**

This revision removes `chat-completions.guard.yaml` and says the machine-readable contract belongs with the integration, but PR #2435 modifies that file rather than adding it. Its streaming test reads the file directly, so stacking that PR on this head leaves the file missing and the test fails. The buffered export in PR #2414 does not provide the stream section the test needs.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

[Pouyanpi]

Superseded by #2413, which now includes this PR's remaining OpenAI provenance, boundary documentation, and metadata tests and targets #2411 directly. The endpoint-bound buffered contract export remains in #2414. The existing branch and commits are preserved. Review concerns about logprobs, explicit plain-text/no-tools values, message cardinality, and nullable stream content are linked from #2413 and are not resolved by closing this standalone PR. Revised stack: #2411 → #2413 → #2414.