fix: finalize pending thinking block before next summary part

internal/translator/codex/claude/codex_claude_response_test.go

@@ -121,6 +121,48 @@ func TestConvertCodexResponseToClaude_StreamThinkingWithoutReasoningItemStillInc
 	}
 }
 
+func TestConvertCodexResponseToClaude_StreamThinkingFinalizesPendingBlockBeforeNextSummaryPart(t *testing.T) {
+	ctx := context.Background()
+	originalRequest := []byte(`{"messages":[]}`)
+	var param any
+
+	chunks := [][]byte{
+		[]byte("data: {\"type\":\"response.reasoning_summary_part.added\"}"),
+		[]byte("data: {\"type\":\"response.reasoning_summary_text.delta\",\"delta\":\"First part\"}"),
+		[]byte("data: {\"type\":\"response.reasoning_summary_part.done\"}"),
+		[]byte("data: {\"type\":\"response.reasoning_summary_part.added\"}"),
+	}
+
+	var outputs [][]byte
+	for _, chunk := range chunks {
+		outputs = append(outputs, ConvertCodexResponseToClaude(ctx, "", originalRequest, nil, chunk, &param)...)
+	}
+
+	startCount := 0
+	stopCount := 0
+	for _, out := range outputs {
+		for _, line := range strings.Split(string(out), "\n") {
+			if !strings.HasPrefix(line, "data: ") {
+				continue
+			}
+			data := gjson.Parse(strings.TrimPrefix(line, "data: "))
+			if data.Get("type").String() == "content_block_start" && data.Get("content_block.type").String() == "thinking" {
+				startCount++
+			}
+			if data.Get("type").String() == "content_block_stop" {
+				stopCount++
+			}
+		}
+	}
+
+	if startCount != 2 {
+		t.Fatalf("expected 2 thinking block starts, got %d", startCount)
+	}
+	if stopCount != 1 {
+		t.Fatalf("expected pending thinking block to be finalized before second start, got %d stops", stopCount)
+	}
+}
+
 func TestConvertCodexResponseToClaudeNonStream_ThinkingIncludesSignature(t *testing.T) {
 	ctx := context.Background()
 	originalRequest := []byte(`{"messages":[]}`)