codex: avoid duplicate realtime audio transcript done

codex-rs/app-server/tests/suite/v2/realtime_conversation.rs

@@ -731,6 +731,10 @@ async fn realtime_text_output_modality_requests_text_output_and_final_transcript
             "type": "response.output_text.delta",
             "delta": "world"
         }),
+        json!({
+            "type": "response.output_audio_transcript.done",
+            "transcript": "hello world"
+        }),
         json!({
             "type": "conversation.item.done",
             "item": {
@@ -829,6 +833,15 @@ async fn realtime_text_output_modality_requests_text_output_and_final_transcript
             text: "hello world".to_string(),
         }
     );
+    assert!(
+        timeout(
+            Duration::from_millis(200),
+            mcp.read_stream_until_notification_message("thread/realtime/transcript/done"),
+        )
+        .await
+        .is_err(),
+        "should not emit duplicate transcript done from audio transcript done"
+    );
 
     realtime_server.shutdown().await;
     Ok(())

codex-rs/codex-api/src/endpoint/realtime_websocket/protocol_v2.rs

@@ -38,10 +38,6 @@ pub(super) fn parse_realtime_event_v2(payload: &str) -> Option<RealtimeEvent> {
         "response.output_text.delta" | "response.output_audio_transcript.delta" => {
             parse_transcript_delta_event(&parsed, "delta").map(RealtimeEvent::OutputTranscriptDelta)
         }
-        "response.output_audio_transcript.done" => {
-            parse_transcript_done_event(&parsed, "transcript")
-                .map(RealtimeEvent::OutputTranscriptDone)
-        }
         "input_audio_buffer.speech_started" => Some(RealtimeEvent::InputAudioSpeechStarted(
             RealtimeInputAudioSpeechStarted {
                 item_id: parsed