From 76b53d6b5b6c7cc48b174d2cfcf611b4f5ccefce Mon Sep 17 00:00:00 2001
From: Ravi Tharuma <RaviTharuma@users.noreply.github.com>
Date: Tue, 24 Mar 2026 19:34:11 +0100
Subject: [PATCH] fix: finalize pending thinking block before next summary part

---
 .../codex/claude/codex_claude_response.go     |  3 ++
 .../claude/codex_claude_response_test.go      | 42 +++++++++++++++++++
 2 files changed, 45 insertions(+)

diff --git a/internal/translator/codex/claude/codex_claude_response.go b/internal/translator/codex/claude/codex_claude_response.go
index 0ddd0845..4f027543 100644
--- a/internal/translator/codex/claude/codex_claude_response.go
+++ b/internal/translator/codex/claude/codex_claude_response.go
@@ -81,6 +81,9 @@ func ConvertCodexResponseToClaude(_ context.Context, _ string, originalRequestRa
 
 		output = translatorcommon.AppendSSEEventBytes(output, "message_start", template, 2)
 	} else if typeStr == "response.reasoning_summary_part.added" {
+		if params.ThinkingBlockOpen && params.ThinkingStopPending {
+			output = append(output, finalizeCodexThinkingBlock(params)...)
+		}
 		template = []byte(`{"type":"content_block_start","index":0,"content_block":{"type":"thinking","thinking":"","signature":""}}`)
 		template, _ = sjson.SetBytes(template, "index", params.BlockIndex)
 		params.ThinkingBlockOpen = true
diff --git a/internal/translator/codex/claude/codex_claude_response_test.go b/internal/translator/codex/claude/codex_claude_response_test.go
index d903dcf7..5a25057c 100644
--- a/internal/translator/codex/claude/codex_claude_response_test.go
+++ b/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":[]}`)