diff --git a/internal/translator/codex/claude/codex_claude_response.go b/internal/translator/codex/claude/codex_claude_response.go
index 4557606f..4db4c9fc 100644
--- a/internal/translator/codex/claude/codex_claude_response.go
+++ b/internal/translator/codex/claude/codex_claude_response.go
@@ -389,6 +389,7 @@ func ClaudeTokenCount(_ context.Context, count int64) []byte {
 
 func finalizeCodexThinkingBlock(params *ConvertCodexResponseToClaudeParams) []byte {
 	if !params.ThinkingBlockOpen {
+		params.ThinkingSignature = ""
 		return nil
 	}