Handle carriage-return lines in Edit guard

Author: mangeshraut712

packages/agent-core-v2/src/app/edit/editService.ts

@@ -12,14 +12,14 @@ export type EditApplyResult =
   | { readonly ok: true; readonly rawContent: string; readonly count: number }
   | { readonly ok: false; readonly error: string };
 
-/** Multi-line empty replacements without an explicit opt-in are refused (see #2427). */
 const LARGE_DELETE_MIN_OLD_LINES = 3;
 
 export function countEditLines(text: string): number {
   if (text.length === 0) return 0;
   let lines = 1;
   for (let i = 0; i < text.length; i++) {
-    if (text.charCodeAt(i) === 10) lines++;
+    const char = text[i];
+    if (char === '\n' || (char === '\r' && text[i + 1] !== '\n')) lines++;
   }
   return lines;
 }

packages/agent-core-v2/test/app/edit/tools/edit.test.ts

@@ -581,6 +581,25 @@ describe('EditTool', () => {
     expect(writeText).toHaveBeenCalledWith('/tmp/skill.md', '\n\nmore');
   });
 
+  it('counts lone carriage returns when guarding multi-line deletions', async () => {
+    const writeText = vi.fn().mockResolvedValue(undefined);
+    const { fs } = createSpiedEditFs({
+      readText: vi.fn().mockResolvedValue('first\rsecond\rthird\rtail'),
+      writeText,
+    });
+    const tool = buildTool(fs, createTestEnv(), PERMISSIVE_WORKSPACE);
+
+    const result = await execute(tool, {
+      path: '/tmp/cr.txt',
+      old_string: 'first\rsecond\rthird',
+      new_string: '',
+    });
+
+    expect(result).toMatchObject({ isError: true });
+    expect(result.output).toContain('Refusing a multi-line deletion');
+    expect(writeText).not.toHaveBeenCalled();
+  });
+
   it('tells the model to reread a large region when old_string is missing', async () => {
     const writeText = vi.fn().mockResolvedValue(undefined);
     const { fs } = createSpiedEditFs({

packages/agent-core/src/tools/builtin/file/edit.ts

@@ -62,7 +62,8 @@ export function countEditLines(text: string): number {
   if (text.length === 0) return 0;
   let lines = 1;
   for (let i = 0; i < text.length; i++) {
-    if (text.charCodeAt(i) === 10) lines++;
+    const char = text[i];
+    if (char === '\n' || (char === '\r' && text[i + 1] !== '\n')) lines++;
   }
   return lines;
 }

packages/agent-core/test/tools/edit.test.ts

@@ -382,6 +382,26 @@ describe('EditTool', () => {
     expect(writeText).toHaveBeenCalledWith('/tmp/skill.md', '\n\nmore');
   });
 
+  it('counts lone carriage returns when guarding multi-line deletions', async () => {
+    const writeText = vi.fn().mockResolvedValue(0);
+    const tool = new EditTool(
+      createFakeKaos({
+        readText: vi.fn().mockResolvedValue('first\rsecond\rthird\rtail'),
+        writeText,
+      }),
+      PERMISSIVE_WORKSPACE,
+    );
+
+    const result = await executeTool(
+      tool,
+      context({ path: '/tmp/cr.txt', old_string: 'first\rsecond\rthird', new_string: '' }),
+    );
+
+    expect(result).toMatchObject({ isError: true });
+    expect(result.output).toContain('Refusing a multi-line deletion');
+    expect(writeText).not.toHaveBeenCalled();
+  });
+
   it('tells the model to reread a large region when old_string is missing', async () => {
     const writeText = vi.fn().mockResolvedValue(0);
     const tool = new EditTool(