fix: preserve optional tool parameters across Responses and Codex tra…

[felixfoertsch]

Summary

Preserve Chat Completions function-tool optionality when routing through Responses, including Codex (cx/*). This targets the OpenCode v2 subagent.sessionID failure: omitting the argument creates a child, while supplying it requests a resume.

Two concrete defects found in 0.5.75

1. open-sse/translator/request/openai-responses.js already preserves parameters.required, but forwards an omitted function.strict as undefined. JSON serialization removes that field. Chat Completions is non-strict by default, whereas Responses can normalize omitted strictness into strict mode, making optional fields required.
2. open-sse/executors/codex.js::normalizeCodexTools rebuilds each function declaration and discards strict, including explicit false and true. A translator-only fix is therefore insufficient for cx/*.

OpenAI documentation: https://developers.openai.com/api/docs/guides/function-calling#strict-mode

The user-reported direct-versus-routed OpenCode result is consistent with these defects. This PR does not claim a live reproduction of model behavior or OpenCode child creation.

Changes

• Emit strict: tool.function.strict ?? false when translating Chat Completions function declarations.
• Capture and restore strictness while rebuilding Codex function tools.
• Default nested Chat-shaped tools reaching the executor to non-strict, while retaining the existing defaults for native flat Responses tools.
• Leave parameter schemas and existing required arrays unchanged; do not derive required fields from property names or silently repair explicitly strict schemas.
• Do not inject, remove, or replace sessionID in returned arguments. Legitimate resume IDs remain intact.

Regression coverage

Adds tests/unit/openai-responses-optional-params.test.js with 26 cases covering:

• Optional sessionID; absent and empty required; nested objects, arrays, unions, and definitions; parameter-less functions.
• Explicit strict values, Chat default handling, native Responses defaults, and nested Chat tool normalization.
• Serialized outbound tool declarations, idempotence, input-schema preservation, and hosted/custom/namespaced tools.
• Replayed arguments and synthetic streamed arguments, both fragmented deltas and done-only payloads, for omitted and supplied child IDs.

The synthetic streaming fixtures verify transport fidelity, not actual model argument selection or OpenCode execution.

Validation performed

In the available offline environment, the same 26 test assertions were run using Node 22's native test runner against the fetched production translator/executor source and the extracted production response-conversion function. External I/O and unrelated provider configuration dependencies were replaced by isolated adapters; helper behavior was copied from the inspected source.

Version	Passed	Failed
Original 0.5.75	8	18
Translator change alone	8	18
Both changes	26	0

node --check and git diff --check passed. Final GitHub blob hashes match the locally validated files.

Not run: the normal Vitest dependency graph, full repository suite/build, live Codex inference, or the OpenCode acceptance probe. Dependencies could not be installed in this environment. This PR remains a draft pending normal integration validation.

From a full checkout with dependencies installed, run:

cd tests
npm test -- unit/openai-responses-optional-params.test.js

Live acceptance still required

Using OpenCode v2 2.0.3, rerun the original identical probe through 9router/cx/gpt-5.6-sol after building and deploying this branch. Retain the direct-provider control.

• Captured final provider request has strict: false for the translated subagent function, and its original required array does not include sessionID.
• The new-child call's captured rawInput lacks sessionID entirely, not merely null or an empty string.
• A real child session is created; the output contains its returned session ID and ROUTED-SUBAGENT-OK.
• An explicit valid child sessionID can still resume that child.

No changes to OpenCode's parent/child validation are proposed. No automatic merge, deployment, or upstream issue/PR is included.

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[forggy0113]

Hi, just following up on this PR. I’m experiencing the same issue, and I’ve tested this PR locally — the fix works for me.
Would it be possible to review and merge this when you have a chance? This fix would really help with my use case. Thanks!

Tested this patch on 9router v0.5.86 with OpenCode v2.0.15 via the Codex/Responses route. Before the patch, creating a subagent failed with Subagent session not found: ses_invalid; after rebuilding and running the patched image, creating a new subagent succeeds.