Parse Codex app-server patch payloads

server/src/session/codex/translate.rs

@@ -305,34 +305,58 @@ fn shell_word(word: &Value) -> String {
 }
 
 fn file_change_diff(item: &Value) -> String {
-    let Some(changes) = item.get("changes").and_then(Value::as_object) else {
-        return String::new();
-    };
-    changes
-        .iter()
-        .map(|(path, change)| {
-            let kind = change.get("type").and_then(Value::as_str);
-            let from = if kind == Some("add") {
-                "/dev/null"
-            } else {
-                path
-            };
-            let to = if kind == Some("delete") {
-                "/dev/null"
-            } else {
-                change
-                    .get("move_path")
+    match item.get("changes") {
+        // Current app-server protocol: [{path, kind: {type, move_path?}, diff}].
+        Some(Value::Array(changes)) => changes
+            .iter()
+            .filter_map(|change| {
+                let path = change.get("path")?.as_str()?;
+                let kind = change.pointer("/kind/type").and_then(Value::as_str);
+                let moved = change.pointer("/kind/move_path").and_then(Value::as_str);
+                let body = change
+                    .get("diff")
                     .and_then(Value::as_str)
-                    .unwrap_or(path)
-            };
-            let body = change
-                .get("unified_diff")
-                .and_then(Value::as_str)
-                .unwrap_or_default();
-            format!("--- {from}\n+++ {to}\n{body}")
-        })
-        .collect::<Vec<_>>()
-        .join("\n")
+                    .unwrap_or_default();
+                Some(render_file_diff(path, kind, moved, body))
+            })
+            .collect::<Vec<_>>()
+            .join("\n"),
+        // Older exec protocol and durable Codex rollouts: {path: {type, unified_diff, ...}}.
+        Some(Value::Object(changes)) => changes
+            .iter()
+            .map(|(path, change)| {
+                render_file_diff(
+                    path,
+                    change.get("type").and_then(Value::as_str),
+                    change.get("move_path").and_then(Value::as_str),
+                    change
+                        .get("unified_diff")
+                        .and_then(Value::as_str)
+                        .unwrap_or_default(),
+                )
+            })
+            .collect::<Vec<_>>()
+            .join("\n"),
+        _ => String::new(),
+    }
+}
+
+fn render_file_diff(path: &str, kind: Option<&str>, moved: Option<&str>, body: &str) -> String {
+    // Some protocol revisions carry complete unified diffs and some carry only their hunks.
+    if body.starts_with("--- ") || body.starts_with("diff --git ") {
+        return body.to_string();
+    }
+    let from = if kind == Some("add") {
+        "/dev/null"
+    } else {
+        path
+    };
+    let to = if kind == Some("delete") {
+        "/dev/null"
+    } else {
+        moved.unwrap_or(path)
+    };
+    format!("--- {from}\n+++ {to}\n{body}")
 }
 
 fn tool_output(item: &Value) -> String {
@@ -537,7 +561,7 @@ mod tests {
         assert!(started.is_empty());
         assert_eq!(
             translator.translate(&line(
-                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"}}}"#
+                r#"{"method":"item/completed","params":{"item":{"id":"patch-1","type":"fileChange","changes":[{"path":"src/main.rs","kind":{"type":"update","move_path":null},"diff":"@@ -1 +1 @@\n-old\n+new\n"}],"status":"completed","stdout":"Success"}}}"#
             )),
             vec![
                 patch_start(
@@ -552,6 +576,17 @@ mod tests {
         );
     }
 
+    #[test]
+    fn the_legacy_file_change_shape_remains_readable() {
+        let item = line(
+            r#"{"changes":{"old.rs":{"type":"update","unified_diff":"@@ -1 +1 @@\n-a\n+b\n","move_path":"new.rs"}}}"#,
+        );
+        assert_eq!(
+            file_change_diff(&item),
+            "--- old.rs\n+++ new.rs\n@@ -1 +1 @@\n-a\n+b\n"
+        );
+    }
+
     #[test]
     fn translates_native_app_server_streaming_without_repeating_the_final_item() {
         let mut translator = Translator::default();