Defer Codex patches until their diff arrives

server/src/session/codex/translate.rs

@@ -154,10 +154,10 @@ fn start_item(item: &Value) -> Vec<Event> {
         item.get("type").and_then(Value::as_str),
         Some("file_change" | "fileChange")
     ) {
-        let Some(id) = item.get("id").and_then(Value::as_str) else {
+        // Unlike command execution, a file change's start notification has no payload. Its
+        // completed copy carries the diff, so that is where both common events are made; recording
+        // this empty shell produced a Patch card containing only `diff:`.
         return Vec::new();
-        };
-        return vec![patch_start(id.to_string(), file_change_diff(item))];
     }
     let Some((id, tool, input)) = tool(item) else {
         return Vec::new();
@@ -202,10 +202,13 @@ fn complete_item(item: &Value, include_agent_message: bool) -> Vec<Event> {
             .get("id")
             .and_then(Value::as_str)
             .map(|id| {
-                vec![Event::ToolEnd {
+                vec![
+                    patch_start(id.to_string(), file_change_diff(item)),
+                    Event::ToolEnd {
                         id: id.to_string(),
                         output: tool_output(item),
-                }]
+                    },
+                ]
             })
             .unwrap_or_default(),
         _ => {
@@ -529,23 +532,23 @@ mod tests {
     fn a_file_change_becomes_the_common_patch_shape() {
         let mut translator = Translator::default();
         let started = translator.translate(&line(
-            r#"{"method":"item/started","params":{"item":{"id":"patch-1","type":"fileChange","changes":{"src/main.rs":{"type":"update","unified_diff":"@@ -1 +1 @@\n-old\n+new\n","move_path":null}},"status":"inProgress"}}}"#,
+            r#"{"method":"item/started","params":{"item":{"id":"patch-1","type":"fileChange","changes":{},"status":"inProgress"}}}"#,
         ));
-        assert_eq!(
-            started,
-            vec![patch_start(
-                "patch-1".to_string(),
-                "--- src/main.rs\n+++ src/main.rs\n@@ -1 +1 @@\n-old\n+new\n".to_string()
-            )]
-        );
+        assert!(started.is_empty());
         assert_eq!(
             translator.translate(&line(
-                r#"{"method":"item/completed","params":{"item":{"id":"patch-1","type":"fileChange","changes":{},"status":"completed","stdout":"Success"}}}"#
+                r#"{"method":"item/completed","params":{"item":{"id":"patch-1","type":"fileChange","changes":{"src/main.rs":{"type":"update","unified_diff":"@@ -1 +1 @@\n-old\n+new\n","move_path":null}},"status":"completed","stdout":"Success"}}}"#
             )),
-            vec![Event::ToolEnd {
+            vec![
+                patch_start(
+                    "patch-1".to_string(),
+                    "--- src/main.rs\n+++ src/main.rs\n@@ -1 +1 @@\n-old\n+new\n".to_string()
+                ),
+                Event::ToolEnd {
                     id: "patch-1".to_string(),
                     output: String::new()
-            }]
+                }
+            ]
         );
     }