diff --git a/apps/daemon/src/server.ts b/apps/daemon/src/server.ts
index 6ea861454..d9bd29e9a 100644
--- a/apps/daemon/src/server.ts
+++ b/apps/daemon/src/server.ts
@@ -885,7 +885,7 @@ export function renderCommentAttachmentHint(commentAttachments) {
     '',
     '',
     '<attached-preview-comments>',
-    'Scope: treat each attachment as the default refinement target. For visual marks, inspect the screenshot and modify the marked region first. Preserve unrelated areas.',
+    "Hard scope: change ONLY the elements identified below by selector / position / pod members. Do NOT modify sibling sub-pages, parent layout, global CSS, design tokens, or unrelated rules even if you notice issues there — surface those as a follow-up note in your reply instead of editing them. If the user's request cannot be satisfied without touching outside this scope, ask the user before proceeding. For visual marks, inspect the screenshot and modify the marked region first.",
   ];
   for (const item of commentAttachments) {
     const targetKind =
diff --git a/apps/daemon/tests/comment-attachments.test.ts b/apps/daemon/tests/comment-attachments.test.ts
index 7a17dcefb..ccfdf1a17 100644
--- a/apps/daemon/tests/comment-attachments.test.ts
+++ b/apps/daemon/tests/comment-attachments.test.ts
@@ -171,6 +171,12 @@ describe('preview comment agent payload', () => {
     expect(hint).toContain('file: index.html');
     expect(hint).toContain('selector: [data-od-id="hero-title"]');
     expect(hint).toContain('comment: Make the headline shorter');
+    // The hard-scope sentence IS the behavior change. Assert its key phrases
+    // so a future edit that softens or drops the directive lights the suite
+    // red instead of silently re-opening the over-broad edit bug.
+    expect(hint).toContain('Hard scope: change ONLY');
+    expect(hint).toContain('Do NOT modify sibling sub-pages, parent layout, global CSS, design tokens, or unrelated rules');
+    expect(hint).toContain('ask the user before proceeding');
   });
 
   it('renders pod attachments with grouped member context', () => {
diff --git a/apps/web/src/comments.ts b/apps/web/src/comments.ts
index ba2904ec4..e5b0ac3c0 100644
--- a/apps/web/src/comments.ts
+++ b/apps/web/src/comments.ts
@@ -308,7 +308,7 @@ function renderCommentAttachmentContext(commentAttachments: ChatCommentAttachmen
     '',
     '',
     '<attached-preview-comments>',
-    'Scope: apply the user request to the attached preview target by default. For visual marks, inspect the screenshot and modify the marked region first. Preserve unrelated elements.',
+    "Hard scope: change ONLY the elements identified below by selector / position / pod members. Do NOT modify sibling sub-pages, parent layout, global CSS, design tokens, or unrelated rules even if you notice issues there — surface those as a follow-up note in your reply instead of editing them. If the user's request cannot be satisfied without touching outside this scope, ask the user before proceeding. For visual marks, inspect the screenshot and modify the marked region first.",
   ];
   commentAttachments.forEach((item) => {
     const position = normalizePosition(item.pagePosition);
diff --git a/apps/web/tests/comments.test.ts b/apps/web/tests/comments.test.ts
index f39bf1e3e..3fb9b86be 100644
--- a/apps/web/tests/comments.test.ts
+++ b/apps/web/tests/comments.test.ts
@@ -265,6 +265,12 @@ describe('preview comment attachment helpers', () => {
     expect(content).toContain('computedStyle: color: rgb(26, 25, 22)');
     expect(content).toContain('fontSize: 13.5px');
     expect(content).toContain('comment: Only shorten this title');
+    // The hard-scope sentence IS the behavior change. Assert its key phrases
+    // so a future edit that softens or drops the directive lights the suite
+    // red instead of silently re-opening the over-broad edit bug.
+    expect(content).toContain('Hard scope: change ONLY');
+    expect(content).toContain('Do NOT modify sibling sub-pages, parent layout, global CSS, design tokens, or unrelated rules');
+    expect(content).toContain('ask the user before proceeding');
   });
 
   it('adds hidden comment context only to the current user message sent to API providers', () => {