diff --git a/packages/pen-ai-skills/src/__tests__/diagnostics.test.ts b/packages/pen-ai-skills/src/__tests__/diagnostics.test.ts
index 0f2d61e04..0b09b37a6 100644
--- a/packages/pen-ai-skills/src/__tests__/diagnostics.test.ts
+++ b/packages/pen-ai-skills/src/__tests__/diagnostics.test.ts
@@ -10,6 +10,7 @@ import {
   detectTextEffect,
   detectTextStroke,
   detectMixedSiblingPadding,
+  detectExcessiveFrameEffects,
   detectAllIssues,
 } from '../diagnostics/detectors';
 import type { PenNode, PenDocument } from '@zseven-w/pen-types';
@@ -1059,3 +1060,132 @@ describe('detectMixedSiblingPadding', () => {
     expect(detectMixedSiblingPadding(root)).toHaveLength(0);
   });
 });
+
+describe('detectExcessiveFrameEffects', () => {
+  it('flags spread > 0 (the "spiked / bleeding" shadow on a badge)', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 'badge',
+          type: 'frame',
+          name: 'Mexican',
+          effects: [{ type: 'shadow', offsetX: 0, offsetY: 0, blur: 8, spread: 4 }],
+          children: [],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    const issues = detectExcessiveFrameEffects(root);
+    expect(issues).toHaveLength(1);
+    expect(issues[0].nodeId).toBe('badge');
+    expect(issues[0].suggestedValue).toBeUndefined();
+    expect(issues[0].reason).toMatch(/spread/);
+  });
+
+  it('flags blur > 40 (atypical halo)', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 'card',
+          type: 'frame',
+          effects: [{ type: 'shadow', blur: 64, spread: 0 }],
+          children: [],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    const issues = detectExcessiveFrameEffects(root);
+    expect(issues).toHaveLength(1);
+    expect(issues[0].reason).toMatch(/blur/);
+  });
+
+  it('does NOT flag blur exactly 40 (modal-shell scrim is legitimate)', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 'modal-bg',
+          type: 'frame',
+          effects: [{ type: 'shadow', blur: 40, spread: 0 }],
+          children: [],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    expect(detectExcessiveFrameEffects(root)).toHaveLength(0);
+  });
+
+  it('flags 3+ stacked effects on one frame', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 'card',
+          type: 'frame',
+          effects: [
+            { type: 'shadow', blur: 8 },
+            { type: 'shadow', blur: 4 },
+            { type: 'blur', radius: 2 },
+          ],
+          children: [],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    const issues = detectExcessiveFrameEffects(root);
+    expect(issues).toHaveLength(1);
+    expect(issues[0].reason).toMatch(/3 stacked|stacked effects/);
+  });
+
+  it('does NOT flag a typical subtle shadow (blur=8, spread=0, single)', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 'card',
+          type: 'frame',
+          effects: [
+            {
+              type: 'shadow',
+              offsetX: 0,
+              offsetY: 4,
+              blur: 8,
+              spread: 0,
+              color: 'rgba(0,0,0,0.1)',
+            },
+          ],
+          children: [],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    expect(detectExcessiveFrameEffects(root)).toHaveLength(0);
+  });
+
+  it('does NOT flag a frame without effects', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [{ id: 'plain', type: 'frame', children: [] } as unknown as PenNode],
+    } as unknown as PenNode;
+    expect(detectExcessiveFrameEffects(root)).toHaveLength(0);
+  });
+
+  it('does NOT flag text nodes (text-effect detector handles those)', () => {
+    const root = {
+      id: 'r',
+      type: 'frame',
+      children: [
+        {
+          id: 't',
+          type: 'text',
+          content: 'hi',
+          effects: [{ type: 'shadow', spread: 8 }],
+        } as unknown as PenNode,
+      ],
+    } as unknown as PenNode;
+    expect(detectExcessiveFrameEffects(root)).toHaveLength(0);
+  });
+});
diff --git a/packages/pen-ai-skills/src/diagnostics/detectors.ts b/packages/pen-ai-skills/src/diagnostics/detectors.ts
index aff928388..49be36fac 100644
--- a/packages/pen-ai-skills/src/diagnostics/detectors.ts
+++ b/packages/pen-ai-skills/src/diagnostics/detectors.ts
@@ -684,7 +684,73 @@ export function detectMixedSiblingPadding(root: PenNode): Issue[] {
 }
 
 /**
- * Run all 10 detectors and return the deduplicated combined issue list.
+ * Aesthetic detector: frame node with shadow/blur effects whose parameters
+ * are outside typical UI ranges. Real product UI shadows are tight and
+ * subtle — blur 4-16, no positive spread, near-black low-alpha color. The
+ * AI hallucination signature is one of:
+ *   - blur >= 40 (too soft, looks like a glow / halo)
+ *   - spread > 0 (a positive spread "bleeds" the shadow outward and reads
+ *     as a colored bloom around the element — the "带尖的背景阴影"
+ *     ("pointy / spiked background shadow") the 2026-05-10 user report
+ *     called out on the Mexican badge)
+ *   - 3+ effects on one frame (badges / cards rarely stack 3+ shadows)
+ *
+ * Suggested fix is to remove the effects array; the user / agent can
+ * re-add a proper shadow afterwards if intentional.
+ */
+export function detectExcessiveFrameEffects(root: PenNode): Issue[] {
+  const issues: Issue[] = [];
+  // Threshold is "strictly greater than" — modal-shell + similar
+  // production builders legitimately use blur=40 for the modal scrim.
+  // A blur of 41+ is the AI-hallucination signature.
+  const TYPICAL_BLUR_MAX = 40;
+  function walk(node: PenNode): void {
+    if (node.type === 'frame') {
+      const eff = (node as unknown as { effects?: unknown }).effects;
+      if (Array.isArray(eff) && eff.length > 0) {
+        let suspect = false;
+        let reason = '';
+        if (eff.length >= 3) {
+          suspect = true;
+          reason = `${eff.length} stacked effects on one frame (typical UI uses 0-2)`;
+        } else {
+          for (const e of eff) {
+            const r = e as { blur?: unknown; spread?: unknown; type?: unknown };
+            if (typeof r.blur === 'number' && r.blur > TYPICAL_BLUR_MAX) {
+              suspect = true;
+              reason = `effect blur ${r.blur} > ${TYPICAL_BLUR_MAX} (glow / halo, atypical for UI)`;
+              break;
+            }
+            if (typeof r.spread === 'number' && r.spread > 0) {
+              suspect = true;
+              reason = `effect spread ${r.spread} > 0 (bleeds outward, "spiked" appearance)`;
+              break;
+            }
+          }
+        }
+        if (suspect) {
+          issues.push({
+            nodeId: node.id,
+            category: 'excessive-frame-effects',
+            severity: 'warning',
+            property: 'effects',
+            currentValue: eff,
+            suggestedValue: undefined,
+            reason,
+          });
+        }
+      }
+    }
+    if ('children' in node && Array.isArray(node.children)) {
+      for (const c of node.children) walk(c);
+    }
+  }
+  walk(root);
+  return issues;
+}
+
+/**
+ * Run all 11 detectors and return the deduplicated combined issue list.
  * Dedup key: `${nodeId}:${property}` (matches runPreValidationFixes).
  * On collision, the first issue wins (detector execution order below).
  */
@@ -700,6 +766,7 @@ export function detectAllIssues(root: PenNode, doc: PenDocument): Issue[] {
     ...detectTextEffect(root),
     ...detectTextStroke(root),
     ...detectMixedSiblingPadding(root),
+    ...detectExcessiveFrameEffects(root),
   ];
   const seen = new Set<string>();
   const unique: Issue[] = [];
diff --git a/packages/pen-ai-skills/src/diagnostics/index.ts b/packages/pen-ai-skills/src/diagnostics/index.ts
index b26d40831..12b30032d 100644
--- a/packages/pen-ai-skills/src/diagnostics/index.ts
+++ b/packages/pen-ai-skills/src/diagnostics/index.ts
@@ -11,5 +11,6 @@ export {
   detectTextEffect,
   detectTextStroke,
   detectMixedSiblingPadding,
+  detectExcessiveFrameEffects,
   detectAllIssues,
 } from './detectors';
diff --git a/packages/pen-ai-skills/src/diagnostics/types.ts b/packages/pen-ai-skills/src/diagnostics/types.ts
index a9d81940e..6057a4a6e 100644
--- a/packages/pen-ai-skills/src/diagnostics/types.ts
+++ b/packages/pen-ai-skills/src/diagnostics/types.ts
@@ -10,7 +10,8 @@ export type IssueCategory =
   | 'mixed-sibling-corner-radius'
   | 'text-effect'
   | 'text-stroke'
-  | 'mixed-sibling-padding';
+  | 'mixed-sibling-padding'
+  | 'excessive-frame-effects';
 
 export interface Issue {
   /** Node id where the issue was detected */
diff --git a/packages/pen-mcp/src/routes/debug-routes.ts b/packages/pen-mcp/src/routes/debug-routes.ts
index 3efe13746..d97ad82b7 100644
--- a/packages/pen-mcp/src/routes/debug-routes.ts
+++ b/packages/pen-mcp/src/routes/debug-routes.ts
@@ -45,6 +45,7 @@ export const DEBUG_TOOL_DEFINITIONS = [
               'text-effect',
               'text-stroke',
               'mixed-sibling-padding',
+              'excessive-frame-effects',
             ],
           },
           description: 'Filter to specific detector categories.',