agent: Handle out of order old_text/new_text in edit file tool

crates/agent/src/tools/edit_file_tool.rs

@@ -753,6 +753,15 @@ mod tests {
         // Edit 2 appears — edit 1 is now complete and should be applied
         sender.send_partial(json!({
             "path": "root/file.txt",
+            "edits": [
+                {"old_text": "aaa", "new_text": "AAA"},
+                {"old_text": "ccc"}
+            ]
+        }));
+        cx.run_until_parked();
+        sender.send_partial(json!({
+            "path": "root/file.txt",
+            "mode": "edit",
             "edits": [
                 {"old_text": "aaa", "new_text": "AAA"},
                 {"old_text": "ccc", "new_text": "CCC"}
@@ -774,6 +783,16 @@ mod tests {
         // Edit 3 appears — edit 2 is now complete and should be applied
         sender.send_partial(json!({
             "path": "root/file.txt",
+            "edits": [
+                {"old_text": "aaa", "new_text": "AAA"},
+                {"old_text": "ccc", "new_text": "CCC"},
+                {"old_text": "eee"}
+            ]
+        }));
+        cx.run_until_parked();
+        sender.send_partial(json!({
+            "path": "root/file.txt",
+            "mode": "edit",
             "edits": [
                 {"old_text": "aaa", "new_text": "AAA"},
                 {"old_text": "ccc", "new_text": "CCC"},
@@ -909,6 +928,12 @@ mod tests {
         }));
         cx.run_until_parked();
 
+        sender.send_partial(json!({
+            "path": "root/file.txt",
+            "edits": [{"old_text": "hello world"}]
+        }));
+        cx.run_until_parked();
+
         sender.send_partial(json!({
             "path": "root/file.txt",
             "edits": [{"old_text": "hello world", "new_text": "goodbye world"}]
@@ -2135,6 +2160,99 @@ mod tests {
         assert_eq!(new_text, "new_content");
     }
 
+    #[gpui::test]
+    async fn test_streaming_edit_file_tool_new_and_old_text_appear_together(
+        cx: &mut TestAppContext,
+    ) {
+        let (tool, _project, _action_log, _fs, _thread) =
+            setup_test(cx, json!({"file.txt": "old_content"})).await;
+        let (mut sender, input) = ToolInput::<EditFileToolInput>::test();
+        let (event_stream, _receiver) = ToolCallEventStream::test();
+        let task = cx.update(|cx| tool.clone().run(input, event_stream, cx));
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt"
+        }));
+        cx.run_until_parked();
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": "old"}]
+        }));
+        cx.run_until_parked();
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": "old_content"}]
+        }));
+        cx.run_until_parked();
+
+        sender.send_full(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": "old_content"}]
+        }));
+        cx.run_until_parked();
+
+        let result = task.await;
+        let EditFileToolOutput::Success { new_text, .. } = result.unwrap() else {
+            panic!("expected success");
+        };
+        assert_eq!(new_text, "new_content");
+    }
+
+    #[gpui::test]
+    async fn test_streaming_edit_file_tool_new_text_before_old_text(cx: &mut TestAppContext) {
+        let (tool, _project, _action_log, _fs, _thread) =
+            setup_test(cx, json!({"file.txt": "old_content"})).await;
+        let (mut sender, input) = ToolInput::<EditFileToolInput>::test();
+        let (event_stream, _receiver) = ToolCallEventStream::test();
+        let task = cx.update(|cx| tool.clone().run(input, event_stream, cx));
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt"
+        }));
+        cx.run_until_parked();
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content"}]
+        }));
+        cx.run_until_parked();
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": ""}]
+        }));
+        cx.run_until_parked();
+
+        sender.send_partial(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": "old"}]
+        }));
+        cx.run_until_parked();
+
+        sender.send_full(json!({
+            "mode": "edit",
+            "path": "root/file.txt",
+            "edits": [{"new_text": "new_content", "old_text": "old_content"}]
+        }));
+        cx.run_until_parked();
+
+        let result = task.await;
+        let EditFileToolOutput::Success { new_text, .. } = result.unwrap() else {
+            panic!("expected success");
+        };
+        assert_eq!(new_text, "new_content");
+    }
+
     #[gpui::test]
     async fn test_streaming_edit_partial_last_line(cx: &mut TestAppContext) {
         let file_content = indoc::indoc! {r#"