diff --git a/src/test/llm.test.js b/src/test/llm.test.js
index 0864089..efcf0bf 100644
--- a/src/test/llm.test.js
+++ b/src/test/llm.test.js
@@ -3,7 +3,7 @@ import assert from 'node:assert/strict';
 import { mkdtemp, writeFile, chmod, rm, readFile } from 'fs/promises';
 import { tmpdir } from 'os';
 import { join } from 'path';
-import { extractBalancedJSON, extractJSONText } from '../llm.js';
+import { extractBalancedJSON, extractJSONText, extractMeaningfulError } from '../llm.js';
 
 const ENV_KEYS = [
   'AI_ASSISTANT_CLI', 'MODEL', 'OPENCODE_MODEL', 'PATH', 'AI_ASSISTANT_TIMEOUT_MS', 'AI_ASSISTANT_MAX_BUFFER',
@@ -237,3 +237,39 @@ describe('extractJSONText', () => {
     assert.equal(result, 'not json at all');
   });
 });
+
+describe('extractMeaningfulError', () => {
+  it('抽出尾端真正的錯誤，而非開頭的 codex banner／回顯 prompt', () => {
+    const raw = [
+      'OpenAI Codex v0.142.5',
+      '--------',
+      'workdir: /workspace/actions/ai-code-review',
+      'model: gpt-5.4-mini',
+      'reasoning effort: none',
+      '--------',
+      'user',
+      '請依照以下系統指示處理使用者內容，並只輸出要求的最終結果。',
+      'ERROR codex_api::endpoint::responses_websocket: failed to connect to websocket: HTTP error: 401 Unauthorized',
+      'ERROR: Your access token could not be refreshed because your refresh token was revoked. Please log out and sign in again.',
+    ].join('\n');
+
+    const result = extractMeaningfulError(raw);
+
+    assert.match(result, /401 Unauthorized/);
+    assert.match(result, /refresh token was revoked/);
+    assert.doesNotMatch(result, /workdir:/);
+    assert.doesNotMatch(result, /請依照以下系統指示/);
+  });
+
+  it('抽不到錯誤行時退取尾段（不取開頭）', () => {
+    const raw = 'A'.repeat(1200) + '\nTAIL-CONTENT';
+    const result = extractMeaningfulError(raw, 100);
+    assert.ok(result.length <= 100);
+    assert.match(result, /TAIL-CONTENT$/);
+  });
+
+  it('容錯處理空輸入', () => {
+    assert.equal(extractMeaningfulError(''), '');
+    assert.equal(extractMeaningfulError(null), '');
+  });
+});