diff --git a/TODO.md b/TODO.md
index d03beba..09239bb 100644
--- a/TODO.md
+++ b/TODO.md
@@ -67,3 +67,4 @@
   5. LLM API Key 至少一把通過驗證：送出最小請求確認認證可用，逗號分隔多把只要一把成功即可並逐把記錄成敗；Ollama 改為檢查 `OLLAMA_BASE_URL` 可連線。
 - 驗收：log 中能看到 `Step1.5`（或對等）前置驗證的每一項結果（成功/失敗），任一失敗時 log 指出是哪一項與錯誤訊息，且 workflow 狀態為失敗；全部通過時 log 出「前置驗證通過」後才進入後續流程；驗證邏輯由 `app/preflight.js` 提供並有單元測試覆蓋（成功、缺環境變數、Gitea token 無效、comment token 無效、所有 LLM key 失敗、Ollama base url 等情境）。
 - 補充紀錄：前置驗證不應發布任何 PR comment，只做唯讀的認證/連線確認；LLM 驗證請用最小 payload，避免浪費 token。
+- 已驗收：`app/preflight.js` 提供 `checkRequiredEnv` / `verifyGiteaToken` / `verifyCommentToken` / `verifyLLM` / `runPreflight`，`main.js` 已在 Step1 之後、bot-check 之前呼叫 `runPreflight()`，未通過即印出原因並 `exit 1`；`app/preflight.test.js` 覆蓋上述情境，`node --test *.test.js` 全數通過。
diff --git a/app/main.js b/app/main.js
index 3ebe32e..2cba174 100644
--- a/app/main.js
+++ b/app/main.js
@@ -6,6 +6,7 @@ import { analyzeWithRole, loadOldFindings, mergeFindings, sortByLevel, deduplica
 import { saveFindings, postOldFindingsComment, postNewNonCriticalComment, postNewCriticalComments } from './comments.js';
 import { cloneRepo, commitAndPush, getRepoState } from './git.js';
 import { validateJSONArrayFile, ensureJSONArrayFileExists } from './json.js';
+import { runPreflight } from './preflight.js';
 import { section, step, line, ok, warn, error } from './log.js';
 
 const WORKSPACE = process.env.GITHUB_WORKSPACE || '/workspace';
@@ -16,6 +17,12 @@ async function main() {
   line(`repo=${GITEA_REPOSITORY}  PR=#${PR_NUMBER}`);
   line(`${PR_HEAD_BRANCH} -> ${PR_BASE_BRANCH}`);
 
+  if (!(await runPreflight())) {
+    error('前置驗證未通過，終止流程');
+    section('Pipeline 結束');
+    process.exit(1);
+  }
+
   const headSha = process.env.PR_HEAD_SHA || process.env.GITHUB_SHA || '';
   const headMessage = await getCommitMessageBySha(headSha);
   const headOutcome = getBotReviewOutcome(headMessage);
diff --git a/app/preflight.js b/app/preflight.js
new file mode 100644
index 0000000..abe223d
--- /dev/null
+++ b/app/preflight.js
@@ -0,0 +1,130 @@
+import axios from 'axios';
+import https from 'https';
+import {
+  GITEA_TOKEN,
+  GITEA_COMMENT_TOKEN,
+  GITEA_SERVER_URL,
+  GITEA_REPOSITORY,
+  GITEA_SKIP_TLS_VERIFY,
+  PR_NUMBER,
+  getLLMConfig,
+} from './config.js';
+import { step, line, ok, error } from './log.js';
+
+const httpsAgent = GITEA_SKIP_TLS_VERIFY ? new https.Agent({ rejectUnauthorized: false }) : undefined;
+const api = (path) => `${GITEA_SERVER_URL.replace(/\/$/, '')}/api/v1${path}`;
+const giteaHeaders = (token) => ({ Authorization: `token ${token}`, 'Content-Type': 'application/json' });
+
+function giteaErr(e) {
+  const status = e.response?.status;
+  return status ? `HTTP ${status} ${e.message}` : e.message;
+}
+
+/** 檢查必要環境變數是否齊全；可傳入覆寫值供測試使用 */
+export function checkRequiredEnv({ token = GITEA_TOKEN, repo = GITEA_REPOSITORY, pr = PR_NUMBER } = {}) {
+  const missing = [];
+  if (!token) missing.push('GITEA_TOKEN');
+  if (!repo) missing.push('GITEA_REPOSITORY');
+  if (!pr) missing.push('PR_NUMBER');
+  return { ok: missing.length === 0, missing };
+}
+
+/** 用 GITEA_TOKEN 讀取此 repo，同時驗證 token 有效與有讀取權限 */
+export async function verifyGiteaToken(token = GITEA_TOKEN, repo = GITEA_REPOSITORY) {
+  try {
+    await axios.get(api(`/repos/${repo}`), { headers: giteaHeaders(token), timeout: 30000, httpsAgent });
+    return { ok: true };
+  } catch (e) {
+    return { ok: false, error: giteaErr(e) };
+  }
+}
+
+/** 若有提供 comment token，用它呼叫 /user 驗證可用；沒提供則略過 */
+export async function verifyCommentToken(token = GITEA_COMMENT_TOKEN) {
+  if (!token) return { ok: true, skipped: true };
+  try {
+    await axios.get(api('/user'), { headers: giteaHeaders(token), timeout: 30000, httpsAgent });
+    return { ok: true };
+  } catch (e) {
+    return { ok: false, error: giteaErr(e) };
+  }
+}
+
+/**
+ * 驗證 LLM 設定可用：
+ * - 須已選定一個 provider
+ * - Ollama 檢查 base URL 是否可連線
+ * - 其餘 provider 以最小請求驗證認證，多把 Key 只要一把成功即可
+ */
+export async function verifyLLM() {
+  const { provider, apiKeys, baseURL, model } = getLLMConfig();
+  if (!provider) return { ok: false, error: '未設定任何 LLM provider 或 API Key' };
+  if (!baseURL) return { ok: false, provider, error: `${provider} 缺少 base URL` };
+
+  const base = baseURL.replace(/\/$/, '');
+
+  if (provider === 'ollama') {
+    try {
+      await axios.get(`${base}/models`, { timeout: 30000 });
+      return { ok: true, provider };
+    } catch (e) {
+      return { ok: false, provider, error: `Ollama base URL 無法連線: ${e.message}` };
+    }
+  }
+
+  const headers = { 'Content-Type': 'application/json' };
+  if (provider === 'claude') headers['anthropic-version'] = '2023-06-01';
+  const payload = { model, messages: [{ role: 'user', content: 'ping' }], max_tokens: 1, temperature: 0 };
+
+  for (let i = 0; i < apiKeys.length; i++) {
+    headers['Authorization'] = `Bearer ${apiKeys[i]}`;
+    try {
+      await axios.post(`${base}/chat/completions`, payload, { headers, timeout: 30000 });
+      return { ok: true, provider, keyIndex: i + 1, total: apiKeys.length };
+    } catch (e) {
+      line(`[preflight] LLM key[${i + 1}/${apiKeys.length}] 驗證失敗: ${e.message}`);
+    }
+  }
+  return { ok: false, provider, error: `所有 ${apiKeys.length} 把 ${provider} API Key 驗證失敗` };
+}
+
+/**
+ * 集中執行所有驗證相關設定的前置檢查；全部通過回傳 true，任一失敗回傳 false。
+ * 僅做唯讀的認證/連線確認，不發布任何 comment。
+ */
+export async function runPreflight() {
+  step('Step1.5', '前置驗證（驗證相關設定）');
+
+  const env = checkRequiredEnv();
+  if (!env.ok) {
+    error(`缺少必要環境變數: ${env.missing.join(', ')}`);
+    return false;
+  }
+  ok('必要環境變數齊全 (GITEA_TOKEN, GITEA_REPOSITORY, PR_NUMBER)');
+
+  const gitea = await verifyGiteaToken();
+  if (!gitea.ok) {
+    error(`GITEA_TOKEN 驗證失敗（無法讀取 repo ${GITEA_REPOSITORY}）: ${gitea.error}`);
+    return false;
+  }
+  ok(`GITEA_TOKEN 可讀取 repo ${GITEA_REPOSITORY}`);
+
+  const comment = await verifyCommentToken();
+  if (!comment.ok) {
+    error(`GITEA_COMMENT_TOKEN 驗證失敗: ${comment.error}`);
+    return false;
+  }
+  if (comment.skipped) line('未提供 GITEA_COMMENT_TOKEN，comment 將沿用 GITEA_TOKEN');
+  else ok('GITEA_COMMENT_TOKEN 可用');
+
+  const llm = await verifyLLM();
+  if (!llm.ok) {
+    error(`LLM 驗證失敗: ${llm.error}`);
+    return false;
+  }
+  if (llm.keyIndex) ok(`LLM provider=${llm.provider} 驗證通過（key ${llm.keyIndex}/${llm.total}）`);
+  else ok(`LLM provider=${llm.provider} 連線正常`);
+
+  ok('前置驗證通過');
+  return true;
+}
diff --git a/app/preflight.test.js b/app/preflight.test.js
new file mode 100644
index 0000000..b49e673
--- /dev/null
+++ b/app/preflight.test.js
@@ -0,0 +1,197 @@
+import { describe, it, afterEach, mock } from 'node:test';
+import assert from 'node:assert/strict';
+import axios from 'axios';
+import { checkRequiredEnv, verifyGiteaToken, verifyCommentToken, verifyLLM, runPreflight } from './preflight.js';
+
+const LLM_ENV_KEYS = [
+  'OPENAI_API_KEY', 'OPENAI_BASE_URL', 'OPENAI_MODEL',
+  'CLAUDE_API_KEY', 'CLAUDE_BASE_URL', 'CLAUDE_MODEL',
+  'GEMINI_API_KEY', 'GEMINI_BASE_URL', 'GEMINI_MODEL',
+  'OLLAMA_BASE_URL', 'OLLAMA_MODEL',
+  'AMAZONQ_API_KEY', 'AMAZONQ_BASE_URL', 'AMAZONQ_MODEL',
+];
+
+function clearLLMEnv() {
+  for (const k of LLM_ENV_KEYS) delete process.env[k];
+}
+
+afterEach(() => {
+  mock.restoreAll();
+  clearLLMEnv();
+});
+
+describe('checkRequiredEnv', () => {
+  it('reports all three missing when nothing provided', () => {
+    const result = checkRequiredEnv({ token: '', repo: '', pr: '' });
+    assert.equal(result.ok, false);
+    assert.deepEqual(result.missing, ['GITEA_TOKEN', 'GITEA_REPOSITORY', 'PR_NUMBER']);
+  });
+
+  it('reports only the missing ones', () => {
+    const result = checkRequiredEnv({ token: 't', repo: '', pr: '5' });
+    assert.equal(result.ok, false);
+    assert.deepEqual(result.missing, ['GITEA_REPOSITORY']);
+  });
+
+  it('ok when all provided', () => {
+    const result = checkRequiredEnv({ token: 't', repo: 'owner/repo', pr: '5' });
+    assert.equal(result.ok, true);
+    assert.deepEqual(result.missing, []);
+  });
+});
+
+describe('verifyGiteaToken', () => {
+  it('ok when repo endpoint returns successfully', async () => {
+    let capturedUrl, capturedOpts;
+    mock.method(axios, 'get', async (url, opts) => {
+      capturedUrl = url;
+      capturedOpts = opts;
+      return { data: { full_name: 'owner/repo' } };
+    });
+    const result = await verifyGiteaToken('tok', 'owner/repo');
+    assert.equal(result.ok, true);
+    assert.ok(capturedUrl.includes('/api/v1/repos/owner/repo'));
+    assert.equal(capturedOpts.headers['Authorization'], 'token tok');
+  });
+
+  it('fails with HTTP status when token is invalid', async () => {
+    mock.method(axios, 'get', async () => {
+      const e = new Error('Unauthorized');
+      e.response = { status: 401 };
+      throw e;
+    });
+    const result = await verifyGiteaToken('bad', 'owner/repo');
+    assert.equal(result.ok, false);
+    assert.match(result.error, /HTTP 401/);
+  });
+});
+
+describe('verifyCommentToken', () => {
+  it('skips when no comment token provided', async () => {
+    const result = await verifyCommentToken('');
+    assert.deepEqual(result, { ok: true, skipped: true });
+  });
+
+  it('ok when /user returns successfully', async () => {
+    let capturedUrl, capturedOpts;
+    mock.method(axios, 'get', async (url, opts) => {
+      capturedUrl = url;
+      capturedOpts = opts;
+      return { data: { login: 'bot' } };
+    });
+    const result = await verifyCommentToken('ctok');
+    assert.equal(result.ok, true);
+    assert.ok(capturedUrl.endsWith('/api/v1/user'));
+    assert.equal(capturedOpts.headers['Authorization'], 'token ctok');
+  });
+
+  it('fails when comment token is invalid', async () => {
+    mock.method(axios, 'get', async () => {
+      const e = new Error('Unauthorized');
+      e.response = { status: 401 };
+      throw e;
+    });
+    const result = await verifyCommentToken('bad');
+    assert.equal(result.ok, false);
+    assert.match(result.error, /HTTP 401/);
+  });
+});
+
+describe('verifyLLM', () => {
+  it('fails when no provider/key configured', async () => {
+    clearLLMEnv();
+    const result = await verifyLLM();
+    assert.equal(result.ok, false);
+    assert.match(result.error, /未設定/);
+  });
+
+  it('ok when an OpenAI-compatible key authenticates', async () => {
+    clearLLMEnv();
+    process.env.OPENAI_API_KEY = 'k1,k2';
+    let capturedUrl, capturedPayload, capturedHeaders;
+    mock.method(axios, 'post', async (url, payload, opts) => {
+      capturedUrl = url;
+      capturedPayload = payload;
+      capturedHeaders = opts.headers;
+      return { data: { choices: [{ message: { content: 'ok' } }] } };
+    });
+    const result = await verifyLLM();
+    assert.equal(result.ok, true);
+    assert.equal(result.provider, 'openai');
+    assert.equal(result.keyIndex, 1);
+    assert.equal(result.total, 2);
+    assert.ok(capturedUrl.endsWith('/chat/completions'));
+    assert.equal(capturedPayload.max_tokens, 1);
+    assert.equal(capturedHeaders['Authorization'], 'Bearer k1');
+  });
+
+  it('tries the next key when the first one fails', async () => {
+    clearLLMEnv();
+    process.env.OPENAI_API_KEY = 'bad,good';
+    let calls = 0;
+    mock.method(axios, 'post', async (_url, _payload, opts) => {
+      calls += 1;
+      if (opts.headers['Authorization'] === 'Bearer bad') throw new Error('401');
+      return { data: { choices: [{ message: { content: 'ok' } }] } };
+    });
+    const result = await verifyLLM();
+    assert.equal(result.ok, true);
+    assert.equal(result.keyIndex, 2);
+    assert.equal(calls, 2);
+  });
+
+  it('fails when all keys fail', async () => {
+    clearLLMEnv();
+    process.env.OPENAI_API_KEY = 'k1,k2';
+    mock.method(axios, 'post', async () => { throw new Error('401'); });
+    const result = await verifyLLM();
+    assert.equal(result.ok, false);
+    assert.match(result.error, /所有 2 把 openai API Key 驗證失敗/);
+  });
+
+  it('sets anthropic-version header for claude', async () => {
+    clearLLMEnv();
+    process.env.CLAUDE_API_KEY = 'ck';
+    let capturedHeaders;
+    mock.method(axios, 'post', async (_url, _payload, opts) => {
+      capturedHeaders = opts.headers;
+      return { data: { choices: [{ message: { content: 'ok' } }] } };
+    });
+    const result = await verifyLLM();
+    assert.equal(result.ok, true);
+    assert.equal(result.provider, 'claude');
+    assert.equal(capturedHeaders['anthropic-version'], '2023-06-01');
+  });
+
+  it('checks base URL connectivity for ollama (no key)', async () => {
+    clearLLMEnv();
+    process.env.OLLAMA_BASE_URL = 'http://ollama.local/v1';
+    let capturedUrl;
+    mock.method(axios, 'get', async (url) => {
+      capturedUrl = url;
+      return { data: { data: [] } };
+    });
+    const result = await verifyLLM();
+    assert.equal(result.ok, true);
+    assert.equal(result.provider, 'ollama');
+    assert.ok(capturedUrl.endsWith('/models'));
+  });
+
+  it('fails when ollama base URL is unreachable', async () => {
+    clearLLMEnv();
+    process.env.OLLAMA_BASE_URL = 'http://ollama.local/v1';
+    mock.method(axios, 'get', async () => { throw new Error('ECONNREFUSED'); });
+    const result = await verifyLLM();
+    assert.equal(result.ok, false);
+    assert.match(result.error, /無法連線/);
+  });
+});
+
+describe('runPreflight', () => {
+  it('returns false and stops early when required env is missing', async () => {
+    // Config constants default to empty in the test environment, so the
+    // required-env check fails before any network call is attempted.
+    const result = await runPreflight();
+    assert.equal(result, false);
+  });
+});