Fix Codex transcript convergence

server/src/session/codex/translate.rs

@@ -52,12 +52,11 @@ impl Translator {
             Some("item.started") | Some("item/started") => start_item(&body["item"]),
             Some("item.updated") => update_item(&line["item"]),
             // The old `codex exec --json` dialect reports only the completed message. App-server
-            // reports every message through durable delta notifications and its completed copy
-            // must always be skipped. That rule cannot live in an in-memory set: after a backend
-            // restart the deltas are behind the persisted log cursor while the completion is not,
-            // which used to append the whole message again after its already-recorded prefix.
+            // also reports deltas, but they are provisional: safety buffering can revise their
+            // text before completion. Keep its completed copy as an append-only correction rather
+            // than guessing that the two representations concatenate to the same answer.
             Some("item.completed") => complete_item(&body["item"], true),
-            Some("item/completed") => complete_item(&body["item"], false),
+            Some("item/completed") => final_item(&body["item"]),
             Some("item/agentMessage/delta") => {
                 let Some(delta) = body.get("delta").and_then(Value::as_str) else {
                     return Vec::new();
@@ -221,6 +220,21 @@ fn complete_item(item: &Value, include_agent_message: bool) -> Vec<Event> {
     }
 }
 
+fn final_item(item: &Value) -> Vec<Event> {
+    match item.get("type").and_then(Value::as_str) {
+        Some("agentMessage") => item
+            .get("text")
+            .and_then(Value::as_str)
+            .map(|text| {
+                vec![Event::AssistantTextFinal {
+                    text: text.to_string(),
+                }]
+            })
+            .unwrap_or_default(),
+        _ => complete_item(item, false),
+    }
+}
+
 fn tool(item: &Value) -> Option<(String, String, Value)> {
     let id = item.get("id")?.as_str()?.to_string();
     let kind = item.get("type")?.as_str()?;
@@ -633,7 +647,7 @@ mod tests {
     }
 
     #[test]
-    fn translates_native_app_server_streaming_without_repeating_the_final_item() {
+    fn native_app_server_completion_corrects_provisional_streaming() {
         let mut translator = Translator::default();
         assert_eq!(
             translator.translate(&line(
@@ -651,12 +665,13 @@ mod tests {
                 delta: "hello".to_string()
             }]
         );
-        assert!(
-            translator
-                .translate(&line(
-                    r#"{"method":"item/completed","params":{"item":{"id":"message-1","type":"agentMessage","text":"hello"}}}"#
-                ))
-                .is_empty()
+        assert_eq!(
+            translator.translate(&line(
+                r#"{"method":"item/completed","params":{"item":{"id":"message-1","type":"agentMessage","text":"hello, revised"}}}"#
+            )),
+            vec![Event::AssistantTextFinal {
+                text: "hello, revised".to_string()
+            }]
         );
         assert!(
             translator
@@ -702,16 +717,17 @@ mod tests {
     }
 
     #[test]
-    fn an_app_server_completion_never_repeats_streamed_text_after_adoption() {
+    fn an_app_server_completion_corrects_streamed_text_after_adoption() {
         // A newly adopted translator has not seen the deltas already recorded by the previous
         // backend. The dialect, rather than process-local memory, decides that this is a copy.
         let mut adopted = Translator::default();
-        assert!(
-            adopted
-                .translate(&line(
-                    r#"{"method":"item/completed","params":{"item":{"id":"message-1","type":"agentMessage","text":"the complete message"}}}"#
-                ))
-                .is_empty()
+        assert_eq!(
+            adopted.translate(&line(
+                r#"{"method":"item/completed","params":{"item":{"id":"message-1","type":"agentMessage","text":"the complete message"}}}"#
+            )),
+            vec![Event::AssistantTextFinal {
+                text: "the complete message".to_string()
+            }]
         );
     }
 }