Merge pull request #135 from weijiafu14/fix/gemini-thought-signature-tool-calls

fix: inject thoughtSignature into functionCall parts for OpenAI→Gemini conversion

package-lock.json

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src/server/routes/proxy/geminiCliCompat.thoughtSignature.test.ts

@@ -0,0 +1,196 @@
+import { describe, it, expect } from 'vitest';
+import { buildGeminiGenerateContentRequestFromOpenAi } from './geminiCliCompat.js';
+
+describe('thoughtSignature injection in OpenAI→Gemini conversion', () => {
+  it('injects thoughtSignature from provider_specific_fields into functionCall parts', () => {
+    const result = buildGeminiGenerateContentRequestFromOpenAi({
+      body: {
+        model: 'gemini-3-flash-preview',
+        messages: [
+          { role: 'user', content: 'What is the weather?' },
+          {
+            role: 'assistant',
+            content: 'Let me check.',
+            tool_calls: [
+              {
+                id: 'call_123',
+                type: 'function',
+                function: { name: 'get_weather', arguments: '{"city":"Tokyo"}' },
+                provider_specific_fields: { thought_signature: 'real_sig_abc' },
+              },
+            ],
+          },
+          { role: 'tool', tool_call_id: 'call_123', content: '{"temp":"22C"}' },
+        ],
+      },
+      modelName: 'gemini-3-flash-preview',
+    }) as Record<string, unknown>;
+
+    const contents = result.contents as Array<Record<string, unknown>>;
+    // Find the model message with functionCall
+    const modelMsgs = contents.filter((c) => c.role === 'model');
+    const fcParts = modelMsgs
+      .flatMap((m) => (m.parts as Array<Record<string, unknown>>))
+      .filter((p) => 'functionCall' in p);
+
+    expect(fcParts.length).toBe(1);
+    expect(fcParts[0].thoughtSignature).toBe('real_sig_abc');
+  });
+
+  it('splits text and signed functionCall parts into separate model messages', () => {
+    const result = buildGeminiGenerateContentRequestFromOpenAi({
+      body: {
+        model: 'gemini-3-flash-preview',
+        messages: [
+          { role: 'user', content: 'Read the file.' },
+          {
+            role: 'assistant',
+            content: 'I will read it.',
+            tool_calls: [
+              {
+                id: 'call_456',
+                type: 'function',
+                function: { name: 'Read', arguments: '{"path":"/tmp/x"}' },
+                provider_specific_fields: { thought_signature: 'sig_split_test' },
+              },
+            ],
+          },
+          { role: 'tool', tool_call_id: 'call_456', content: 'file content here' },
+        ],
+      },
+      modelName: 'gemini-3-flash-preview',
+    }) as Record<string, unknown>;
+
+    const contents = result.contents as Array<Record<string, unknown>>;
+    const modelMsgs = contents.filter((c) => c.role === 'model');
+
+    // Should be 2 model messages: text (unsigned) + functionCall (signed)
+    expect(modelMsgs.length).toBe(2);
+
+    const firstParts = modelMsgs[0].parts as Array<Record<string, unknown>>;
+    const secondParts = modelMsgs[1].parts as Array<Record<string, unknown>>;
+
+    // First: text only, no thoughtSignature
+    expect(firstParts.every((p) => 'text' in p)).toBe(true);
+    expect(firstParts.every((p) => !('thoughtSignature' in p))).toBe(true);
+
+    // Second: functionCall with thoughtSignature
+    expect(secondParts.every((p) => 'functionCall' in p)).toBe(true);
+    expect(secondParts[0].thoughtSignature).toBe('sig_split_test');
+  });
+
+  it('injects dummy sentinel when thinking enabled but no signature available', () => {
+    const result = buildGeminiGenerateContentRequestFromOpenAi({
+      body: {
+        model: 'gemini-3-flash-preview',
+        reasoning_effort: 'high',
+        messages: [
+          { role: 'user', content: 'Do something.' },
+          {
+            role: 'assistant',
+            tool_calls: [
+              {
+                id: 'call_no_sig',
+                type: 'function',
+                function: { name: 'Bash', arguments: '{"command":"ls"}' },
+                // No provider_specific_fields — signature missing
+              },
+            ],
+          },
+          { role: 'tool', tool_call_id: 'call_no_sig', content: 'file1\nfile2' },
+        ],
+      },
+      modelName: 'gemini-3-flash-preview',
+    }) as Record<string, unknown>;
+
+    const contents = result.contents as Array<Record<string, unknown>>;
+    const modelMsgs = contents.filter((c) => c.role === 'model');
+    const fcParts = modelMsgs
+      .flatMap((m) => (m.parts as Array<Record<string, unknown>>))
+      .filter((p) => 'functionCall' in p);
+
+    expect(fcParts.length).toBe(1);
+    // Should have a dummy sentinel, not be missing
+    expect(typeof fcParts[0].thoughtSignature).toBe('string');
+    expect((fcParts[0].thoughtSignature as string).length).toBeGreaterThan(0);
+  });
+
+  it('does not inject thoughtSignature when thinking is not enabled', () => {
+    const result = buildGeminiGenerateContentRequestFromOpenAi({
+      body: {
+        model: 'gemini-2.5-flash',
+        messages: [
+          { role: 'user', content: 'Hello' },
+          {
+            role: 'assistant',
+            tool_calls: [
+              {
+                id: 'call_no_think',
+                type: 'function',
+                function: { name: 'Read', arguments: '{"path":"/x"}' },
+              },
+            ],
+          },
+          { role: 'tool', tool_call_id: 'call_no_think', content: 'data' },
+        ],
+      },
+      modelName: 'gemini-2.5-flash',
+    }) as Record<string, unknown>;
+
+    const contents = result.contents as Array<Record<string, unknown>>;
+    const modelMsgs = contents.filter((c) => c.role === 'model');
+    const fcParts = modelMsgs
+      .flatMap((m) => (m.parts as Array<Record<string, unknown>>))
+      .filter((p) => 'functionCall' in p);
+
+    expect(fcParts.length).toBe(1);
+    // No thinking → no signature injected
+    expect(fcParts[0].thoughtSignature).toBeUndefined();
+  });
+
+  it('preserves functionResponse count matching functionCall count', () => {
+    const result = buildGeminiGenerateContentRequestFromOpenAi({
+      body: {
+        model: 'gemini-3-flash-preview',
+        messages: [
+          { role: 'user', content: 'Read two files.' },
+          {
+            role: 'assistant',
+            tool_calls: [
+              {
+                id: 'call_a',
+                type: 'function',
+                function: { name: 'Read', arguments: '{"path":"/a"}' },
+                provider_specific_fields: { thought_signature: 'sig_a' },
+              },
+              {
+                id: 'call_b',
+                type: 'function',
+                function: { name: 'Read', arguments: '{"path":"/b"}' },
+                provider_specific_fields: { thought_signature: 'sig_b' },
+              },
+            ],
+          },
+          { role: 'tool', tool_call_id: 'call_a', content: 'content a' },
+          { role: 'tool', tool_call_id: 'call_b', content: 'content b' },
+        ],
+      },
+      modelName: 'gemini-3-flash-preview',
+    }) as Record<string, unknown>;
+
+    const contents = result.contents as Array<Record<string, unknown>>;
+
+    // Count functionCall and functionResponse parts
+    let fcCount = 0;
+    let frCount = 0;
+    for (const content of contents) {
+      for (const part of (content.parts as Array<Record<string, unknown>>)) {
+        if ('functionCall' in part) fcCount++;
+        if ('functionResponse' in part) frCount++;
+      }
+    }
+
+    expect(fcCount).toBe(2);
+    expect(frCount).toBe(2);
+  });
+});

src/server/routes/proxy/geminiCliCompat.ts

@@ -1,6 +1,10 @@
 import { TextDecoder, TextEncoder } from 'node:util';
 import { resolveGeminiThinkingConfigFromRequest } from '../../transformers/gemini/generate-content/convert.js';
 
+// Dummy sentinel used when no real thoughtSignature is available but thinking
+// mode is enabled. Gemini accepts any base64 string and won't reject this.
+const DUMMY_THOUGHT_SIGNATURE = 'c2tpcF90aG91Z2h0X3NpZ25hdHVyZV92YWxpZGF0b3I=';
+
 function isRecord(value: unknown): value is Record<string, unknown> {
   return !!value && typeof value === 'object' && !Array.isArray(value);
 }
@@ -143,6 +147,27 @@ export function buildGeminiGenerateContentRequestFromOpenAi(input: {
     }
   }
 
+  // Detect if thinking mode is enabled (needed for dummy signature fallback)
+  const hasThinkingEnabled = !!resolveGeminiThinkingConfigFromRequest(input.modelName, input.body);
+
+  // Collect thoughtSignatures from assistant tool_calls for injection.
+  // OpenAI format stores signatures in provider_specific_fields or encoded in tool call IDs.
+  const thoughtSignatureById = new Map<string, string>();
+  for (const message of messages) {
+    if (!isRecord(message) || asTrimmedString(message.role) !== 'assistant') continue;
+    const toolCalls = Array.isArray(message.tool_calls) ? message.tool_calls : [];
+    for (const toolCall of toolCalls) {
+      if (!isRecord(toolCall)) continue;
+      const id = asTrimmedString(toolCall.id);
+      if (!id) continue;
+      // Check provider_specific_fields first
+      const providerFields = isRecord(toolCall.provider_specific_fields) ? toolCall.provider_specific_fields : null;
+      if (providerFields && typeof providerFields.thought_signature === 'string') {
+        thoughtSignatureById.set(id, providerFields.thought_signature);
+      }
+    }
+  }
+
   const systemParts: Array<Record<string, unknown>> = [];
   if (typeof input.instructions === 'string' && input.instructions.trim()) {
     systemParts.push({ text: input.instructions.trim() });
@@ -176,7 +201,8 @@ export function buildGeminiGenerateContentRequestFromOpenAi(input: {
       continue;
     }
 
-    const parts = convertContentToGeminiParts(message.content);
+    const textParts = convertContentToGeminiParts(message.content);
+    const fcParts: Array<Record<string, unknown>> = [];
     const toolCalls = Array.isArray(message.tool_calls) ? message.tool_calls : [];
     for (const toolCall of toolCalls) {
       if (!isRecord(toolCall) || !isRecord(toolCall.function)) continue;
@@ -193,21 +219,45 @@ export function buildGeminiGenerateContentRequestFromOpenAi(input: {
       } else if (isRecord(rawArguments)) {
         args = rawArguments;
       }
-      parts.push({
+      const fcPart: Record<string, unknown> = {
-        functionCall: {
+        functionCall: { name, args },
-          name,
+      };
-          args,
+      // Inject thoughtSignature if available from provider_specific_fields.
-        },
+      // If no signature is found, use a dummy sentinel so Gemini doesn't reject
-      });
+      // the request outright. Gemini 3+ requires thoughtSignature on all
+      // functionCall parts when thinking is enabled.
+      // Ref: https://ai.google.dev/gemini-api/docs/thought-signatures
+      const id = asTrimmedString(toolCall.id);
+      const signature = thoughtSignatureById.get(id);
+      if (signature) {
+        fcPart.thoughtSignature = signature;
+      } else if (hasThinkingEnabled) {
+        fcPart.thoughtSignature = DUMMY_THOUGHT_SIGNATURE;
       }
-    if (parts.length <= 0) continue;
+      fcParts.push(fcPart);
+    }
+
+    const geminiRole = role === 'assistant' ? 'model' : 'user';
+
+    // Gemini requires that parts WITH thoughtSignature and parts WITHOUT
+    // are not mixed in the same message. Split if needed.
+    // Ref: https://ai.google.dev/gemini-api/docs/thought-signatures
+    const hasSigned = fcParts.some((p) => 'thoughtSignature' in p);
+    if (hasSigned && textParts.length > 0 && fcParts.length > 0) {
+      // Emit text parts first, then functionCall parts in a separate message
       request.contents = [
         ...(Array.isArray(request.contents) ? request.contents : []),
-      {
+        { role: geminiRole, parts: textParts },
-        role: role === 'assistant' ? 'model' : 'user',
+        { role: geminiRole, parts: fcParts },
-        parts,
-      },
       ];
+    } else {
+      const allParts = [...textParts, ...fcParts];
+      if (allParts.length <= 0) continue;
+      request.contents = [
+        ...(Array.isArray(request.contents) ? request.contents : []),
+        { role: geminiRole, parts: allParts },
+      ];
+    }
   }
 
   if (systemParts.length > 0) {