feat: add extra headers support to responses endpoint

intercept/responses/base.go

@@ -52,6 +52,12 @@ type responsesInterceptionBase struct {
 func (i *responsesInterceptionBase) newResponsesService() responses.ResponseService {
 	opts := []option.RequestOption{option.WithBaseURL(i.cfg.BaseURL), option.WithAPIKey(i.cfg.Key)}
 
+	// Add extra headers if configured.
+	// Some providers require additional headers that are not added by the SDK.
+	for key, value := range i.cfg.ExtraHeaders {
+		opts = append(opts, option.WithHeader(key, value))
+	}
+
 	// Add API dump middleware if configured
 	if mw := apidump.NewMiddleware(i.cfg.APIDumpDir, config.ProviderOpenAI, i.Model(), i.id, i.logger, quartz.NewReal()); mw != nil {
 		opts = append(opts, option.WithMiddleware(mw))

provider/copilot_test.go

@@ -221,6 +221,53 @@ func TestCopilot_CreateInterceptor(t *testing.T) {
 		assert.Contains(t, err.Error(), "unmarshal responses request body")
 	})
 
+	t.Run("Responses_ForwardsHeadersToUpstream", func(t *testing.T) {
+		t.Parallel()
+
+		var receivedHeaders http.Header
+
+		// Mock upstream that captures headers
+		mockUpstream := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			receivedHeaders = r.Header.Clone()
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusOK)
+			_, _ = w.Write([]byte(`{"id":"resp-123","object":"responses.response","created":1677652288,"model":"gpt-5-mini","output":[],"usage":{"input_tokens":5,"output_tokens":10,"total_tokens":15}}`))
+		}))
+		t.Cleanup(mockUpstream.Close)
+
+		// Create provider with mock upstream URL
+		provider := NewCopilot(config.Copilot{
+			BaseURL: mockUpstream.URL,
+		})
+
+		body := `{"model": "gpt-5-mini", "input": "hello", "stream": false}`
+		req := httptest.NewRequest(http.MethodPost, routeCopilotResponses, bytes.NewBufferString(body))
+		req.Header.Set("Authorization", "Bearer test-token")
+		req.Header.Set("Editor-Version", "vscode/1.85.0")
+		req.Header.Set("Copilot-Integration-Id", "test-integration")
+		req.Header.Set("X-Custom-Header", "should-not-forward")
+		w := httptest.NewRecorder()
+
+		interceptor, err := provider.CreateInterceptor(w, req, testTracer)
+		require.NoError(t, err)
+		require.NotNil(t, interceptor)
+
+		// Setup and process request
+		logger := slog.Make()
+		interceptor.Setup(logger, &testutil.MockRecorder{}, nil)
+
+		processReq := httptest.NewRequest(http.MethodPost, routeCopilotResponses, nil)
+		err = interceptor.ProcessRequest(w, processReq)
+		require.NoError(t, err)
+
+		// Verify headers were forwarded
+		assert.Equal(t, "vscode/1.85.0", receivedHeaders.Get("Editor-Version"))
+		assert.Equal(t, "test-integration", receivedHeaders.Get("Copilot-Integration-Id"))
+
+		// Verify non-Copilot headers are not forwarded
+		assert.Empty(t, receivedHeaders.Get("X-Custom-Header"), "non-Copilot headers should not be forwarded")
+	})
+
 	t.Run("UnknownRoute", func(t *testing.T) {
 		t.Parallel()