fix(relaykit): preserve Gemini text alongside tool calls (#7998)

relaykit/relayconvert/internal/gemini_chat/to_oai_chat_req.go

@@ -131,7 +131,8 @@ func GeminiGenerateContentRequestToOpenAIChat(ctx context.Context, geminiRequest
 
 		if len(toolCalls) > 0 {
 			message.SetToolCalls(toolCalls)
-		} else if len(mediaContents) == 1 && mediaContents[0].Type == "text" {
+		}
+		if len(mediaContents) == 1 && mediaContents[0].Type == "text" {
 			message.Content = mediaContents[0].Text
 		} else if len(mediaContents) > 0 {
 			message.SetMediaContent(mediaContents)

relaykit/relayconvert/request_registry_test.go

@@ -1110,3 +1110,52 @@ func mustMarshalRequestJSON(t *testing.T, value any) []byte {
 	require.NoError(t, err)
 	return raw
 }
+
+func TestGeminiToOpenAIChatPreservesTextAlongsideToolCalls(t *testing.T) {
+	const text = "I will check the weather."
+	call := dto.GeminiPart{FunctionCall: &dto.FunctionCall{
+		ID: "call_weather", FunctionName: "get_weather", Arguments: map[string]any{"city": "Paris"},
+	}}
+	for _, tt := range []struct {
+		name      string
+		parts     []dto.GeminiPart
+		wantText  []string
+		wantCalls int
+	}{
+		{name: "text and call", parts: []dto.GeminiPart{{Text: text}, call}, wantText: []string{text}, wantCalls: 1},
+		{name: "text around call", parts: []dto.GeminiPart{{Text: text}, call, {Text: "Please wait."}}, wantText: []string{text, "Please wait."}, wantCalls: 1},
+		{name: "call only", parts: []dto.GeminiPart{call}, wantCalls: 1},
+		{name: "text only", parts: []dto.GeminiPart{{Text: text}}, wantText: []string{text}},
+	} {
+		t.Run(tt.name, func(t *testing.T) {
+			request := &dto.GeminiChatRequest{Contents: []dto.GeminiChatContent{{Role: "model", Parts: tt.parts}}}
+			result, err := ConvertRequest(context.Background(), &convmeta.Values{
+				UpstreamModelName: "gpt-4o", ChannelMetaAttached: true,
+			}, types.RelayFormatOpenAI, request)
+			require.NoError(t, err)
+			converted, ok := result.Value.(*dto.GeneralOpenAIRequest)
+			require.True(t, ok)
+			// Verify the JSON sent upstream, including custom DTO serialization.
+			body, err := kitutil.Marshal(converted)
+			require.NoError(t, err)
+			var wire dto.GeneralOpenAIRequest
+			require.NoError(t, kitutil.Unmarshal(body, &wire))
+			require.Len(t, wire.Messages, 1)
+			assistant := wire.Messages[0]
+			assert.Equal(t, "assistant", assistant.Role)
+			content := assistant.ParseContent()
+			require.Len(t, content, len(tt.wantText))
+			for i, want := range tt.wantText {
+				assert.Equal(t, "text", content[i].Type)
+				assert.Equal(t, want, content[i].Text)
+			}
+			calls := assistant.ParseToolCalls()
+			require.Len(t, calls, tt.wantCalls)
+			if tt.wantCalls > 0 {
+				assert.Equal(t, "call_weather", calls[0].ID)
+				assert.Equal(t, "get_weather", calls[0].Function.Name)
+				assert.JSONEq(t, `{"city":"Paris"}`, calls[0].Function.Arguments)
+			}
+		})
+	}
+}