fix(kosong): make Gemini (google-genai/vertexai) tool-calling work#1360
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fix(kosong): make Gemini (google-genai/vertexai) tool-calling work#1360powerfooI wants to merge 1 commit into
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The Google GenAI provider built function declarations and content parts with snake_case keys (function_declarations, parameters_json_schema, function_call, function_response, thought_signature). The @google/genai SDK expects camelCase, so it silently dropped those keys and sent empty tool specs, causing Gemini to return MALFORMED_FUNCTION_CALL. Separately, tool-call thought_signature extras captured from responses were dropped in the agent-core tool-call event pipeline (LoopToolCallEvent had no extras; the context/transcript reconstructors rebuilt tool calls without them), so multi-turn Gemini 3.x tool use failed with "missing thought_signature". - kosong/google-genai: emit camelCase functionDeclarations / parametersJsonSchema / functionCall / functionResponse / thoughtSignature. - agent-core: add extras to LoopToolCallEvent, dispatch toolCall.extras, and copy extras when rebuilding tool calls in ContextMemory and the transcript service. - Update kosong google-genai tests to assert the camelCase the SDK requires. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
🦋 Changeset detectedLatest commit: ce8bae6 The changes in this PR will be included in the next version bump. This PR includes changesets to release 2 packages
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Related Issue
No existing issue — this is a clear, reproducible bug fix with a focused diff (allowed without prior discussion per CONTRIBUTING). Problem described below.
Problem
Gemini tool-calling is broken for both
google-genaiandvertexai:Empty tool specs →
MALFORMED_FUNCTION_CALL. The provider builds function declarations with snake_case keys (function_declarations,parameters_json_schema) and content parts withfunction_call/function_response/thought_signature. The@google/genaiSDK expects camelCase, so it drops these keys and sends empty tool objects (tools: [{}]) on the wire. Gemini then responds withfinishReason: MALFORMED_FUNCTION_CALLand empty content.Multi-turn fails with
missing thought_signature. Once tools are populated, Gemini 3.x requires thethoughtSignatureto be echoed back on later turns. The provider captures it intoToolCall.extras.thought_signature_b64, butLoopToolCallEventhas noextrasfield and theContextMemory/ transcript reconstructors rebuild tool calls without it, so the signature is lost and continuations are rejected.The existing
google-genaitests mockgenerateContentStreamand assert the snake_case object passed into the SDK, so the real serialization was never exercised and the bug went uncaught.What changed
packages/kosong/src/providers/google-genai.ts— emit the camelCase keys the SDK expects:functionDeclarations,parametersJsonSchema,functionCall,functionResponse,thoughtSignature.packages/agent-core— addextrastoLoopToolCallEvent, dispatchtoolCall.extrasindispatchToolCall, and copyextraswhen rebuilding tool calls inContextMemory(agent/context) and the transcript service, sothoughtSignatureround-trips across turns.packages/kosong/test/google-genai.test.ts— updated to assert the camelCase keys the SDK requires.Verified end-to-end against a real Gemini endpoint (
gemini-3.1-pro-preview): multi-turn tool-using tasks (create file → shell command → read back) now complete for bothgoogle-genaiandvertexai.pnpm typecheck,pnpm lint(0 errors), and the kosong/agent-core test suites pass.Checklist
gen-changesetsskill, or this PR needs no changeset. (changeset added manually)gen-docsskill, or this PR needs no doc update. (no user-facing doc change)