fix(translator): handle empty tool function names in OpenAI Claude responses

- Added check to prevent processing of empty `function.name` values, ensuring valid data is handled.

Fixed: #2557

internal/translator/openai/claude/openai_claude_response.go

@@ -236,7 +236,7 @@ func convertOpenAIStreamingChunkToAnthropic(rawJSON []byte, param *ConvertOpenAI
 
 				// Handle function name
 				if function := toolCall.Get("function"); function.Exists() {
-					if name := function.Get("name"); name.Exists() {
+					if name := function.Get("name"); name.Exists() && name.String() != "" {
 						accumulator.Name = util.MapToolName(param.ToolNameMap, name.String())
 
 						stopThinkingContentBlock(param, &results)

internal/translator/openai/claude/openai_claude_response_test.go

@@ -0,0 +1,41 @@
+package claude
+
+import (
+	"bytes"
+	"context"
+	"testing"
+)
+
+func TestConvertOpenAIResponseToClaude_StreamIgnoresNullToolNameDelta(t *testing.T) {
+	originalRequest := []byte(`{"stream":true}`)
+	var param any
+
+	firstChunks := ConvertOpenAIResponseToClaude(
+		context.Background(),
+		"test-model",
+		originalRequest,
+		nil,
+		[]byte(`data: {"id":"chatcmpl_1","model":"test-model","created":1,"choices":[{"index":0,"delta":{"role":"assistant","tool_calls":[{"index":0,"id":"call_1","type":"function","function":{"name":"read_file","arguments":""}}]},"finish_reason":null}]}`),
+		&param,
+	)
+	firstOutput := bytes.Join(firstChunks, nil)
+	if !bytes.Contains(firstOutput, []byte(`"name":"read_file"`)) {
+		t.Fatalf("expected first chunk to start read_file tool block, got %s", string(firstOutput))
+	}
+
+	secondChunks := ConvertOpenAIResponseToClaude(
+		context.Background(),
+		"test-model",
+		originalRequest,
+		nil,
+		[]byte(`data: {"id":"chatcmpl_1","model":"test-model","created":1,"choices":[{"index":0,"delta":{"tool_calls":[{"index":0,"function":{"name":null,"arguments":"{\"path\":\"/tmp/a\"}"}}]},"finish_reason":null}]}`),
+		&param,
+	)
+	secondOutput := bytes.Join(secondChunks, nil)
+	if bytes.Contains(secondOutput, []byte(`content_block_start`)) {
+		t.Fatalf("did not expect null tool name delta to start a new content block, got %s", string(secondOutput))
+	}
+	if bytes.Contains(secondOutput, []byte(`"name":""`)) {
+		t.Fatalf("did not expect null tool name delta to emit an empty tool name, got %s", string(secondOutput))
+	}
+}