address comment

src/server/routes/proxy/upstreamEndpoint.test.ts

@@ -679,6 +679,40 @@ describe('buildUpstreamEndpointRequest', () => {
     expect(request.body.temperature).toBe(0.8);
   });
 
+  it('strips unsupported openai parameters like frequency_penalty for Gemini models from downstream responses bodies', () => {
+    const request = buildUpstreamEndpointRequest({
+      endpoint: 'responses',
+      modelName: 'gemini-1.5-pro',
+      stream: false,
+      tokenValue: 'sk-test',
+      sitePlatform: 'gemini',
+      openaiBody: {},
+      downstreamFormat: 'responses',
+      responsesOriginalBody: {
+        model: 'gemini-1.5-pro',
+        input: 'hello',
+        frequency_penalty: 0.5,
+        presence_penalty: 0.2,
+        logit_bias: { '100': 1 },
+        logprobs: true,
+        top_logprobs: 2,
+        store: true,
+        temperature: 0.8,
+        top_p: 1.0,
+      },
+    });
+
+    expect(request.path).toBe('/v1beta/openai/responses');
+    expect(request.body.frequency_penalty).toBeUndefined();
+    expect(request.body.presence_penalty).toBeUndefined();
+    expect(request.body.logit_bias).toBeUndefined();
+    expect(request.body.logprobs).toBeUndefined();
+    expect(request.body.top_logprobs).toBeUndefined();
+    expect(request.body.store).toBeUndefined();
+    expect(request.body.temperature).toBe(0.8);
+    expect(request.body.top_p).toBe(1.0);
+  });
+
   it('preserves structured responses content blocks instead of flattening them', () => {
     const request = buildUpstreamEndpointRequest({
       endpoint: 'responses',

src/server/routes/proxy/upstreamEndpoint.ts

@@ -481,20 +481,24 @@ export function buildUpstreamEndpointRequest(input: {
     commonHeaders.Authorization = `Bearer ${input.tokenValue}`;
   }
 
-  const openaiBody = { ...input.openaiBody };
+  const stripGeminiUnsupportedFields = (body: Record<string, unknown>) => {
-  if (isGeminiUpstream) {
+    const next = { ...body };
-    const blacklist = [
+    if (isGeminiUpstream) {
-      'frequency_penalty',
+      for (const key of [
-      'presence_penalty',
+        'frequency_penalty',
-      'logit_bias',
+        'presence_penalty',
-      'logprobs',
+        'logit_bias',
-      'top_logprobs',
+        'logprobs',
-      'store',
+        'top_logprobs',
-    ];
+        'store',
-    for (const key of blacklist) {
+      ]) {
-      delete openaiBody[key];
+        delete next[key];
+      }
     }
-  }
+    return next;
+  };
+
+  const openaiBody = stripGeminiUnsupportedFields(input.openaiBody);
 
   if (input.endpoint === 'messages') {
     const claudeHeaders = input.downstreamFormat === 'claude'
@@ -554,7 +558,7 @@ export function buildUpstreamEndpointRequest(input: {
     const rawBody = (
       input.downstreamFormat === 'responses' && input.responsesOriginalBody
         ? {
-          ...input.responsesOriginalBody,
+          ...stripGeminiUnsupportedFields(input.responsesOriginalBody),
           model: input.modelName,
           stream: input.stream,
         }