antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called

antigravity-direct: a specific-function `tool_choice` is flattened to `functionCallingConfig: ANY` — the function the client required is never pinned, and any declared function may be called instead

Repo: developing-today/code · Main: df9381ff · File: bin/antigravity-direct.mjs:355-357 (landed today in b0058ec7)

Summary

OpenAI's Chat Completions API lets a caller force one specific function: tool_choice: { "type": "function", "function": { "name": "get_weather" } }. buildV1Request translates tool_choice to the Cloud Code / Gemini functionCallingConfig like this:

if (body.tool_choice) {
  const mode = body.tool_choice === 'none' ? 'NONE' : body.tool_choice === 'auto' ? 'AUTO' : 'ANY';
  request.toolConfig = { functionCallingConfig: { mode } };
}

Every non-none/auto value — including the specific-function object — becomes bare ANY, and the allowedFunctionNames field that functionCallingConfig provides for exactly this case is never set. ANY means "must call some declared function", not "must call this function": a client that required get_weather can be answered with a call to any other declared function (in the probe: send_email).

The string forms are fine ("none" → NONE, "auto" → AUTO, "required" → ANY is the correct semantic). Only the object form loses information.

Evidence (verified this run, real module)

Laptop probe (~/git/fleet/probe-2026-10-30-laneA-antigrav-body/; bin/antigravity-direct.mjs md5 de11cfa24df8200d66fd788422667ef8 identical on sandbox main df9381ff and the laptop; stub secret-tool + stub upstream recording every payload — no real keyring read, no real Google call). Sent:

{
  "model": "gemini-3.8-flash",
  "messages": [{ "role": "user", "content": "weather?" }],
  "tools": [
    { "type": "function", "function": { "name": "get_weather", "parameters": { "type": "object", "properties": {} } } },
    { "type": "function", "function": { "name": "send_email",  "parameters": { "type": "object", "properties": {} } } }
  ],
  "tool_choice": { "type": "function", "function": { "name": "get_weather" } }
}

The recorded upstream streamGenerateContent payload carried both declarations but:

"toolConfig": { "functionCallingConfig": { "mode": "ANY" } }

— no allowedFunctionNames, nothing naming get_weather. The response to the client was a normal HTTP 200, so the downgrade is silent.

Why it matters

Callers use a specific-function tool_choice as a control-flow guarantee (structured extraction, a router that must invoke exactly one named tool, a safety gate that must not fire side-effecting tools). Through this door the guarantee silently degrades to "some function": the model may invoke a different — possibly side-effecting — declared function, and the client, which never opted into that, will execute it under the assumption its choice was honoured. The fleet's own pattern already preserves the choice end-to-end: bin/muse-proxy.mjs:1161-1164 maps the object form through ({type:'function', name}), pinned by bin/muse-proxy.test.mjs:598,648.

Acceptance criteria

A specific-function tool_choice ({type:"function", function:{name:"X"}}) produces an upstream functionCallingConfig that restricts calling to X (e.g. mode: "ANY" with allowedFunctionNames: ["X"] — triage pins the exact upstream shape), where X is one of the declared functions.
String forms are unchanged: "none" → NONE, "auto" → AUTO, "required" → ANY (no allowed list).
A tool_choice naming a function that was not declared does not silently widen to unrestricted ANY — it is rejected with a 400 or handled by an explicit, documented fallback (triage pins which).
Regression tests in a new bin/antigravity-direct.test.mjs (stub-upstream payload recording, in the style of bin/muse-proxy.test.mjs:598) cover the specific-function case and the three string forms; requests without tool_choice send no toolConfig, as today.

Dedup notes: searched open + closed issues this run for tool_choice / functionCallingConfig / allowedFunctionNames against antigravity — no hit. Distinct from #2821 (same file, request-body shape guard; this is a translation-fidelity bug on a well-formed object body).

🤖 Agent note · filed

Agent: new-issue-creator (lane A, new-issue-creator-code-a)
Session / ID: cron new-issue-creator-code-a, run 2026-10-30 14:35 CDT
Found via: filed this run
Task: Triage the tool_choice translation in bin/antigravity-direct.mjs — a specific-function choice is flattened to functionCallingConfig ANY with no allowedFunctionNames — and pin the pinned-function upstream shape plus regression tests
Expectation: effort/s — done when a specific-function tool_choice restricts the upstream call to the named function, string forms are unchanged, and bin/antigravity-direct.test.mjs pins all forms
Links: probe (laptop) ~/git/fleet/probe-2026-10-30-laneA-antigrav-body/ (toolchoice case; recorded upstream payload) · sibling door antigravity-direct: a non-object JSON body is never a 400 — 'null' 500s at body.model, and scalar/array bodies fabricate an empty upstream request for model '-medium' and return 200 #2821 · fleet pattern bin/muse-proxy.mjs:1161-1164

agent-note:v1 — picked up — Lane D

Agent: queue worker (repo-worker-code), lane D
Session / ID: task 5427, repo-health-code-pilot
Found via: atomic queue claim
Fresh state: issue antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822 OPEN, no hard-stop labels, no competing PR. Triage pins (task 3945) confirmed on the issue: object form -> {mode: ANY, allowedFunctionNames: [X]}; undeclared/malformed name -> HTTP 400 invalid_request_error before upstream; string forms unchanged; no tool_choice -> no toolConfig.
Disposition: implementing in laptop worktree on branch queue/5427-2822-tool-choice with a new bin/antigravity-direct.test.mjs.

agent-note:v1 — PR opened, parked on CI — Lane D

Agent: queue worker (repo-worker-code), lane D
Session / ID: task 5427, repo-health-code-pilot
Work: implemented the triage-pinned fix on branch queue/5427-2822-tool-choice (laptop worktree ~/git/fleet/5427): specific-function tool_choice -> {mode: ANY, allowedFunctionNames: [X]}; undeclared/malformed name -> 400 invalid_request_error before upstream; string forms and no-choice unchanged. New bin/antigravity-direct.test.mjs: node --test on the laptop — 6 pass, 0 fail.
PR: fix(antigravity-direct): pin specific-function tool_choice via allowedFunctionNames (#2822) #4233 (head 9b58ebc). Codex review requested.
Disposition: task 5427 parked 20 minutes on CI.
Resume condition: PR fix(antigravity-direct): pin specific-function tool_choice via allowedFunctionNames (#2822) #4233 checks green + Codex findings dispositioned -> merge, close issue antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822, complete task 5427.

Merge pull request #4233 from developing-today/queue/5427-2822-tool-c…

agent-note:v1 — done — Lane D

Agent: queue worker (repo-worker-code), lane D
Session / ID: task 5427, repo-health-code-pilot
Outcome: PR fix(antigravity-direct): pin specific-function tool_choice via allowedFunctionNames (#2822) #4233 merged (merge commit e26e36a); issue antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822 closed by the merge.
Verification: Codex review completed on head 9b58ebc with no findings; only check was CodeRabbit skipping (neutral); prior laptop targeted tests node --test bin/antigravity-direct.test.mjs 6/6 pass; diff matched the antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822 intent (specific-function tool_choice -> ANY + allowedFunctionNames, undeclared/malformed -> 400 before upstream).
Labels: status/parked, queue/parked, work/assigned removed on completion.

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antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822

antigravity-direct: a specific-function `tool_choice` is flattened to `functionCallingConfig: ANY` — the function the client required is never pinned, and any declared function may be called instead

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antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig ANY — the client-required function is never pinned and any declared function may be called #2822

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antigravity-direct: a specific-function tool_choice is flattened to functionCallingConfig: ANY — the function the client required is never pinned, and any declared function may be called instead

Summary

Evidence (verified this run, real module)

Why it matters

Acceptance criteria

Activity

dezren39 commented on Oct 30, 2026

10 remaining items

dezren39 commented on Nov 2, 2026

dezren39 commented on Nov 2, 2026

dezren39 commented on Nov 2, 2026

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antigravity-direct: a specific-function `tool_choice` is flattened to `functionCallingConfig: ANY` — the function the client required is never pinned, and any declared function may be called instead