diff --git a/Dockerfile b/Dockerfile
index af3dacb..eec32a5 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -1,10 +1,20 @@
-FROM alpine:latest
+FROM node:20-bookworm-slim
+
+# 安裝必要工具：git（操作分支/合併）、bash、ca-certificates、curl（安裝 opencode）
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends git bash ca-certificates curl \
+    && rm -rf /var/lib/apt/lists/*
+
+# 安裝 opencode CLI（用於分析 git diff 產生 PR 標題與描述）
+RUN npm install -g opencode-ai
+
+# 複製 Node.js 應用程式
+COPY app/ /app/
+
+# 應用程式無第三方相依套件，僅在有 package-lock 時安裝
+RUN if [ -f /app/package-lock.json ]; then cd /app && npm ci --omit=dev; fi
 
-# 安裝必要的工具
-RUN apk add --no-cache --no-check-certificate bash
-    
 COPY entrypoint.sh /entrypoint.sh
-
 RUN chmod +x /entrypoint.sh
 
-ENTRYPOINT ["/entrypoint.sh"]
\ No newline at end of file
+ENTRYPOINT ["/entrypoint.sh"]
diff --git a/action.yaml b/action.yaml
index 2000f7c..5970182 100644
--- a/action.yaml
+++ b/action.yaml
@@ -1,22 +1,31 @@
-name: 'Docker Action Template'
-description: 'Docker Action 範本'
+name: 'AI Pull Request'
+description: '使用 opencode 分析 git diff 產生 PR 標題與描述，並透過 Gitea token 建立 Pull Request；遇衝突時自動建立解衝突分支'
 author: 'Jeffery'
 inputs:
-  gitea_token:
-    description: 'Gitea Token'
+  source_branch:
+    description: '來源分支'
+    required: true
+  target_branch:
+    description: '目標分支'
+    required: true
+  opencode_base_url:
+    description: 'opencode 使用的模型服務 base URL（OpenAI 相容端點）'
+    required: true
+  opencode_model:
+    description: 'opencode 使用的模型名稱'
+    required: true
+  opencode_provider:
+    description: 'opencode provider 名稱'
     required: true
-  text:
-    description: '輸入的文字'
-    required: false
-    default: 'Hello, World!'
-outputs:
-  text:
-    description: '輸出的文字'
 runs:
   using: 'docker'
   image: 'Dockerfile'
   env:
     GITEA_SERVER_URL: ${{ gitea.server_url }}
     GITEA_REPOSITORY: ${{ gitea.repository }}
-    GITEA_TOKEN: ${{ secrets.GITEA_TOKEN || inputs.gitea_token }}
-    TEXT: ${{ inputs.text }}
\ No newline at end of file
+    GITEA_TOKEN: ${{ gitea.token }}
+    SOURCE_BRANCH: ${{ inputs.source_branch }}
+    TARGET_BRANCH: ${{ inputs.target_branch }}
+    OPENCODE_BASE_URL: ${{ inputs.opencode_base_url }}
+    OPENCODE_MODEL: ${{ inputs.opencode_model }}
+    OPENCODE_PROVIDER: ${{ inputs.opencode_provider }}
diff --git a/app/index.js b/app/index.js
new file mode 100644
index 0000000..81b4c3d
--- /dev/null
+++ b/app/index.js
@@ -0,0 +1,185 @@
+import { loadInputs, logInputs } from './lib/inputs.js';
+import { Git } from './lib/git.js';
+import { GiteaClient } from './lib/gitea.js';
+import { OpenCode } from './lib/opencode.js';
+import { log } from './lib/util.js';
+
+async function main() {
+  const inputs = loadInputs();
+  logInputs(inputs);
+
+  const remoteUrl = `${inputs.serverUrl}/${inputs.owner}/${inputs.repo}.git`;
+
+  const git = new Git({ cwd: inputs.workspace, remoteUrl, token: inputs.token });
+  const gitea = new GiteaClient({
+    serverUrl: inputs.serverUrl,
+    owner: inputs.owner,
+    repo: inputs.repo,
+    token: inputs.token,
+  });
+  const opencode = new OpenCode({ ...inputs.opencode, language: inputs.language });
+
+  // 1. 準備 git 環境並抓取兩個分支
+  log.step('準備 git 環境');
+  git.configure();
+  git.fetchBranches([inputs.sourceBranch, inputs.targetBranch]);
+
+  // 2. 確認來源分支相對目標分支有變更
+  const ahead = git.countAheadCommits(inputs.targetBranch, inputs.sourceBranch);
+  if (ahead === 0) {
+    log.warn(`來源分支 ${inputs.sourceBranch} 相對 ${inputs.targetBranch} 沒有新的 commit，無需建立 PR`);
+    return;
+  }
+  log.info(`來源分支領先 ${ahead} 個 commit`);
+
+  // 3. 蒐集 diff 內容
+  log.step('蒐集 git diff');
+  const commitMessages = git.getCommitMessages(inputs.targetBranch, inputs.sourceBranch);
+  const diffStat = git.getDiffStat(inputs.targetBranch, inputs.sourceBranch);
+  const fullDiff = git.getDiff(inputs.targetBranch, inputs.sourceBranch);
+  const { diff, truncated } = truncateDiff(fullDiff, inputs.maxDiffChars);
+  if (truncated) log.warn(`diff 過大，已截斷至 ${inputs.maxDiffChars} 字元`);
+
+  // 4. 使用 opencode 產生標題與描述（失敗則 fallback）
+  log.step('使用 opencode 產生 PR 標題與描述');
+  let summary = await opencode.summarize({
+    sourceBranch: inputs.sourceBranch,
+    targetBranch: inputs.targetBranch,
+    commitMessages,
+    diffStat,
+    diff,
+  });
+  if (!summary) {
+    log.warn('改用 commit/stat 自動產生標題與描述');
+    summary = fallbackSummary({
+      source: inputs.sourceBranch,
+      target: inputs.targetBranch,
+      commitMessages,
+      diffStat,
+    });
+  }
+  log.success(`標題: ${summary.title}`);
+
+  // 5. 偵測合併衝突
+  log.step('偵測合併衝突');
+  const { hasConflict, files } = git.detectConflict(inputs.targetBranch, inputs.sourceBranch);
+
+  if (!hasConflict) {
+    // 5a. 無衝突：直接建立 來源 → 目標 的 PR
+    log.success('無衝突，建立來源分支 → 目標分支的 PR');
+    const { pull, created } = await gitea.createPull({
+      head: inputs.sourceBranch,
+      base: inputs.targetBranch,
+      title: summary.title,
+      body: summary.description,
+    });
+    reportPull(pull, created);
+    return;
+  }
+
+  // 5b. 有衝突：從目標分支建立解衝突分支，合併來源分支後 PR 回來源分支
+  log.warn(`偵測到衝突檔案 (${files.length}): ${files.join(', ')}`);
+  const resolveBranch = buildResolveBranchName(inputs.targetBranch, inputs.sourceBranch);
+
+  log.step('建立解衝突分支並合併來源分支');
+  const { files: conflictFiles } = git.createResolveBranch({
+    target: inputs.targetBranch,
+    source: inputs.sourceBranch,
+    resolveBranch,
+  });
+
+  const body = buildResolveBody({
+    source: inputs.sourceBranch,
+    target: inputs.targetBranch,
+    resolveBranch,
+    files: conflictFiles.length ? conflictFiles : files,
+    summary,
+  });
+
+  log.step('建立解衝突分支 → 來源分支的 PR');
+  const { pull, created } = await gitea.createPull({
+    head: resolveBranch,
+    base: inputs.sourceBranch,
+    title: `解衝突: 將 ${inputs.targetBranch} 合併回 ${inputs.sourceBranch}`,
+    body,
+  });
+  reportPull(pull, created);
+}
+
+/** 把 diff 截斷至上限字元數。 */
+function truncateDiff(diff, maxChars) {
+  if (!diff || diff.length <= maxChars) return { diff: diff || '', truncated: false };
+  return {
+    diff: `${diff.slice(0, maxChars)}\n\n... (diff 已截斷，僅顯示前 ${maxChars} 字元) ...`,
+    truncated: true,
+  };
+}
+
+/** opencode 不可用時，用 commit 訊息與 stat 產生簡單摘要。 */
+function fallbackSummary({ source, target, commitMessages, diffStat }) {
+  const firstCommit = (commitMessages || '')
+    .split('\n')
+    .map((l) => l.replace(/^- /, '').trim())
+    .find(Boolean);
+  const title = firstCommit || `Merge ${source} into ${target}`;
+  const description = [
+    `## 變更摘要`,
+    ``,
+    `將 \`${source}\` 合併到 \`${target}\`。`,
+    ``,
+    `### Commits`,
+    commitMessages || '(無)',
+    ``,
+    `### 變更檔案`,
+    '```',
+    diffStat || '(無)',
+    '```',
+  ].join('\n');
+  return { title, description };
+}
+
+/** 解衝突分支名稱。 */
+function buildResolveBranchName(target, source) {
+  const runId = process.env.GITHUB_RUN_NUMBER || process.env.GITHUB_RUN_ID || '';
+  const safe = (s) => s.replace(/[^a-zA-Z0-9._/-]/g, '-');
+  const suffix = runId ? `-${runId}` : '';
+  return `resolve-conflict/${safe(target)}-into-${safe(source)}${suffix}`;
+}
+
+/** 解衝突 PR 的描述。 */
+function buildResolveBody({ source, target, resolveBranch, files, summary }) {
+  return [
+    `## ⚠️ 自動解衝突 PR`,
+    ``,
+    `來源分支 \`${source}\` 合併到目標分支 \`${target}\` 時偵測到衝突，`,
+    `已自動從 \`${target}\` 建立解衝突分支 \`${resolveBranch}\` 並合併 \`${source}\`。`,
+    ``,
+    `**此 PR 會將 \`${resolveBranch}\` 合併回 \`${source}\`，請在合併前手動解決下列檔案的衝突標記（\`<<<<<<<\`、\`=======\`、\`>>>>>>>\`）：**`,
+    ``,
+    ...files.map((f) => `- \`${f}\``),
+    ``,
+    `解決並合併此 PR 後，\`${source}\` 即可順利合併進 \`${target}\`。`,
+    ``,
+    `---`,
+    ``,
+    `### AI 變更摘要`,
+    ``,
+    summary.description || '(無)',
+  ].join('\n');
+}
+
+/** 印出 PR 結果。 */
+function reportPull(pull, created) {
+  const url = pull?.html_url || pull?.url || '';
+  const number = pull?.number || '';
+  if (created) {
+    log.success(`已建立 PR #${number}: ${url}`);
+  } else {
+    log.info(`PR 已存在 #${number}: ${url}`);
+  }
+}
+
+main().catch((err) => {
+  log.error(err?.stack || err?.message || String(err));
+  process.exit(1);
+});
diff --git a/app/lib/git.js b/app/lib/git.js
new file mode 100644
index 0000000..28b9bfd
--- /dev/null
+++ b/app/lib/git.js
@@ -0,0 +1,163 @@
+import { run, runOrThrow, log, maskSecrets } from './util.js';
+
+/**
+ * 封裝這個 action 需要的 git 操作。所有對遠端的操作都透過
+ * http.extraheader 帶上 Gitea token，避免 token 寫進 remote URL。
+ */
+export class Git {
+  /**
+   * @param {object} opts
+   * @param {string} opts.cwd 工作目錄（已 checkout 的 repo）
+   * @param {string} opts.remoteUrl 不含認證資訊的 repo HTTPS URL
+   * @param {string} opts.token Gitea token
+   */
+  constructor({ cwd, remoteUrl, token }) {
+    this.cwd = cwd;
+    this.remoteUrl = remoteUrl;
+    this.token = token;
+    // Gitea 接受 "Authorization: token <token>"
+    this.authArgs = ['-c', `http.extraheader=Authorization: token ${token}`];
+  }
+
+  /** 帶 token 的 git 執行（用於遠端操作），不會把 args 印進日誌。 */
+  _authGit(args, { throwOnError = true } = {}) {
+    const full = [...this.authArgs, ...args];
+    const result = run('git', full, { cwd: this.cwd });
+    if (throwOnError && result.status !== 0) {
+      const detail = maskSecrets(result.stderr || result.stdout, [this.token]).trim();
+      throw new Error(`git ${args.join(' ')} 失敗 (${result.status}):\n${detail}`);
+    }
+    return result;
+  }
+
+  /** 不帶 token 的本地 git 執行。 */
+  _git(args, opts = {}) {
+    return run('git', args, { cwd: this.cwd, ...opts });
+  }
+
+  /** 初始化必要的 git 設定（safe.directory、user.name/email）。 */
+  configure() {
+    run('git', ['config', '--global', '--add', 'safe.directory', this.cwd]);
+    run('git', ['config', '--global', '--add', 'safe.directory', '*']);
+    // 解衝突分支需要建立 merge commit，必須有身份
+    this._git(['config', 'user.name', process.env.GIT_AUTHOR_NAME || 'ai-pull-request[bot]']);
+    this._git(['config', 'user.email', process.env.GIT_AUTHOR_EMAIL || 'ai-pull-request@users.noreply.gitea']);
+  }
+
+  /**
+   * 從遠端抓取 source 與 target 分支到本地追蹤分支 refs/remotes/pr/<branch>。
+   *
+   * @param {string[]} branches
+   */
+  fetchBranches(branches) {
+    const refspecs = branches.map((b) => `+refs/heads/${b}:refs/remotes/pr/${b}`);
+    log.info(`抓取分支: ${branches.join(', ')}`);
+    this._authGit(['fetch', '--no-tags', this.remoteUrl, ...refspecs]);
+  }
+
+  /** 取得分支的 commit 數量差異（source 比 target 多幾個 commit）。 */
+  countAheadCommits(target, source) {
+    const result = this._git(['rev-list', '--count', `refs/remotes/pr/${target}..refs/remotes/pr/${source}`]);
+    return result.status === 0 ? parseInt(result.stdout.trim(), 10) || 0 : 0;
+  }
+
+  /** 取得 source 相對 target 的 commit 訊息清單。 */
+  getCommitMessages(target, source, limit = 50) {
+    const result = this._git([
+      'log',
+      `--max-count=${limit}`,
+      '--pretty=format:- %s',
+      `refs/remotes/pr/${target}..refs/remotes/pr/${source}`,
+    ]);
+    return result.status === 0 ? result.stdout.trim() : '';
+  }
+
+  /** 取得 diff 統計（--stat）。 */
+  getDiffStat(target, source) {
+    const result = this._git([
+      'diff',
+      '--stat',
+      `refs/remotes/pr/${target}...refs/remotes/pr/${source}`,
+    ]);
+    return result.status === 0 ? result.stdout.trim() : '';
+  }
+
+  /** 取得完整 diff（three-dot，等同 PR 在 merge base 之後的變更）。 */
+  getDiff(target, source) {
+    const result = this._git([
+      'diff',
+      `refs/remotes/pr/${target}...refs/remotes/pr/${source}`,
+    ]);
+    return result.status === 0 ? result.stdout : '';
+  }
+
+  /**
+   * 偵測 source 合併進 target 是否會衝突（不會留下任何變更）。
+   *
+   * @returns {{ hasConflict: boolean, files: string[] }}
+   */
+  detectConflict(target, source) {
+    // 建立暫時的本地 target 分支，嘗試以 --no-commit 合併 source
+    const tmp = `__conflict_check_${target}`;
+    this._git(['checkout', '-B', tmp, `refs/remotes/pr/${target}`]);
+
+    const merge = this._git(['merge', '--no-commit', '--no-ff', `refs/remotes/pr/${source}`]);
+    let hasConflict = merge.status !== 0;
+    let files = [];
+
+    if (hasConflict) {
+      const unmerged = this._git(['diff', '--name-only', '--diff-filter=U']);
+      files = unmerged.stdout.split('\n').map((s) => s.trim()).filter(Boolean);
+    }
+
+    // 還原工作區
+    this._git(['merge', '--abort']);
+    this._git(['checkout', '--detach']);
+    this._git(['branch', '-D', tmp]);
+
+    return { hasConflict, files };
+  }
+
+  /**
+   * 建立解衝突分支：以 target 為基礎，合併 source（保留衝突標記後 commit），
+   * 再推送到遠端。
+   *
+   * @param {object} opts
+   * @param {string} opts.target 目標分支
+   * @param {string} opts.source 來源分支
+   * @param {string} opts.resolveBranch 解衝突分支名稱
+   * @returns {{ files: string[] }} 衝突檔案清單
+   */
+  createResolveBranch({ target, source, resolveBranch }) {
+    log.info(`以 ${target} 為基礎建立解衝突分支 ${resolveBranch}`);
+    this._git(['checkout', '-B', resolveBranch, `refs/remotes/pr/${target}`]);
+
+    const merge = this._git([
+      'merge',
+      '--no-ff',
+      '-m',
+      `Merge branch '${source}' into ${resolveBranch} (待人工解衝突)`,
+      `refs/remotes/pr/${source}`,
+    ]);
+
+    let files = [];
+    if (merge.status !== 0) {
+      // 合併產生衝突：將含有衝突標記的檔案標記為已解決後 commit，
+      // 讓開發者可以在 PR 中看到並解決衝突。
+      const unmerged = this._git(['diff', '--name-only', '--diff-filter=U']);
+      files = unmerged.stdout.split('\n').map((s) => s.trim()).filter(Boolean);
+
+      runOrThrow('git', ['add', '-A'], { cwd: this.cwd });
+      runOrThrow(
+        'git',
+        ['commit', '--no-verify', '-m', `Merge branch '${source}' into ${resolveBranch}（含衝突標記，待人工解衝突）`],
+        { cwd: this.cwd },
+      );
+    }
+
+    log.info(`推送解衝突分支 ${resolveBranch}`);
+    this._authGit(['push', '--force', this.remoteUrl, `HEAD:refs/heads/${resolveBranch}`]);
+
+    return { files };
+  }
+}
diff --git a/app/lib/gitea.js b/app/lib/gitea.js
new file mode 100644
index 0000000..28ff34e
--- /dev/null
+++ b/app/lib/gitea.js
@@ -0,0 +1,98 @@
+import { log } from './util.js';
+
+/**
+ * 極簡的 Gitea API client，只實作這個 action 需要的 PR 相關操作。
+ */
+export class GiteaClient {
+  /**
+   * @param {object} opts
+   * @param {string} opts.serverUrl Gitea base URL（不含結尾斜線）
+   * @param {string} opts.owner
+   * @param {string} opts.repo
+   * @param {string} opts.token
+   */
+  constructor({ serverUrl, owner, repo, token }) {
+    this.apiBase = `${serverUrl}/api/v1`;
+    this.owner = owner;
+    this.repo = repo;
+    this.token = token;
+  }
+
+  async _request(method, path, body) {
+    const url = `${this.apiBase}${path}`;
+    const res = await fetch(url, {
+      method,
+      headers: {
+        Authorization: `token ${this.token}`,
+        'Content-Type': 'application/json',
+        Accept: 'application/json',
+      },
+      body: body ? JSON.stringify(body) : undefined,
+    });
+
+    const text = await res.text();
+    let json;
+    try {
+      json = text ? JSON.parse(text) : {};
+    } catch {
+      json = { message: text };
+    }
+    return { ok: res.ok, status: res.status, json };
+  }
+
+  /**
+   * 查詢 head -> base 是否已存在開啟中的 PR。
+   *
+   * @param {string} head 來源分支
+   * @param {string} base 目標分支
+   * @returns {Promise<object|null>}
+   */
+  async findOpenPull(head, base) {
+    // Gitea pulls 不直接支援 head/base 過濾，這裡撈開啟中的 PR 自行比對
+    const { ok, json } = await this._request(
+      'GET',
+      `/repos/${this.owner}/${this.repo}/pulls?state=open&limit=50`,
+    );
+    if (!ok || !Array.isArray(json)) return null;
+    return (
+      json.find(
+        (pr) => pr?.head?.ref === head && pr?.base?.ref === base,
+      ) || null
+    );
+  }
+
+  /**
+   * 建立 Pull Request。若已存在相同 head/base 的 PR 則回傳既有 PR。
+   *
+   * @param {object} opts
+   * @param {string} opts.head 來源分支
+   * @param {string} opts.base 目標分支
+   * @param {string} opts.title
+   * @param {string} opts.body
+   * @returns {Promise<{ pull: object, created: boolean }>}
+   */
+  async createPull({ head, base, title, body }) {
+    log.info(`建立 PR: ${head} → ${base}`);
+    const { ok, status, json } = await this._request(
+      'POST',
+      `/repos/${this.owner}/${this.repo}/pulls`,
+      { head, base, title, body },
+    );
+
+    if (ok) {
+      return { pull: json, created: true };
+    }
+
+    // 422 通常代表 PR 已存在
+    if (status === 422 || status === 409) {
+      const existing = await this.findOpenPull(head, base);
+      if (existing) {
+        log.warn(`PR 已存在: #${existing.number}`);
+        return { pull: existing, created: false };
+      }
+    }
+
+    const message = json?.message || JSON.stringify(json);
+    throw new Error(`建立 PR 失敗 (${status}): ${message}`);
+  }
+}
diff --git a/app/lib/inputs.js b/app/lib/inputs.js
new file mode 100644
index 0000000..a221542
--- /dev/null
+++ b/app/lib/inputs.js
@@ -0,0 +1,81 @@
+import { log } from './util.js';
+
+/**
+ * 從環境變數讀取並驗證所有輸入參數。
+ *
+ * @returns {{
+ *   serverUrl: string,
+ *   repository: string,
+ *   owner: string,
+ *   repo: string,
+ *   token: string,
+ *   sourceBranch: string,
+ *   targetBranch: string,
+ *   opencode: { baseUrl: string, model: string, provider: string },
+ *   language: string,
+ *   maxDiffChars: number,
+ *   workspace: string,
+ * }}
+ */
+export function loadInputs() {
+  const serverUrl = trimSlash(required('GITEA_SERVER_URL'));
+  const repository = required('GITEA_REPOSITORY'); // owner/repo
+  const token = required('GITEA_TOKEN');
+  const sourceBranch = required('SOURCE_BRANCH');
+  const targetBranch = required('TARGET_BRANCH');
+
+  const [owner, repo] = repository.split('/');
+  if (!owner || !repo) {
+    throw new Error(`GITEA_REPOSITORY 格式應為 owner/repo，收到: ${repository}`);
+  }
+
+  if (sourceBranch === targetBranch) {
+    throw new Error(`來源分支與目標分支不可相同: ${sourceBranch}`);
+  }
+
+  const opencode = {
+    baseUrl: trimSlash(process.env.OPENCODE_BASE_URL || ''),
+    model: process.env.OPENCODE_MODEL || '',
+    provider: process.env.OPENCODE_PROVIDER || '',
+  };
+
+  // PR 標題/描述固定使用繁體中文，diff 截斷上限固定，皆不透過參數控制
+  const language = 'Traditional Chinese (繁體中文)';
+  const maxDiffChars = 60000;
+  const workspace = process.env.GITHUB_WORKSPACE || process.cwd();
+
+  return {
+    serverUrl,
+    repository,
+    owner,
+    repo,
+    token,
+    sourceBranch,
+    targetBranch,
+    opencode,
+    language,
+    maxDiffChars,
+    workspace,
+  };
+}
+
+function required(name) {
+  const value = process.env[name];
+  if (!value || !value.trim()) {
+    throw new Error(`缺少必要的環境變數: ${name}`);
+  }
+  return value.trim();
+}
+
+function trimSlash(url) {
+  return url.replace(/\/+$/, '');
+}
+
+/** 印出輸入摘要（遮蔽敏感資訊）。 */
+export function logInputs(inputs) {
+  log.info(`Gitea Server : ${inputs.serverUrl}`);
+  log.info(`Repository   : ${inputs.repository}`);
+  log.info(`來源分支     : ${inputs.sourceBranch}`);
+  log.info(`目標分支     : ${inputs.targetBranch}`);
+  log.info(`opencode     : provider=${inputs.opencode.provider || '(未設定)'} model=${inputs.opencode.model || '(未設定)'} baseUrl=${inputs.opencode.baseUrl || '(未設定)'}`);
+}
diff --git a/app/lib/opencode.js b/app/lib/opencode.js
new file mode 100644
index 0000000..1190790
--- /dev/null
+++ b/app/lib/opencode.js
@@ -0,0 +1,230 @@
+import { writeFileSync, mkdtempSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { run, log, maskSecrets } from './util.js';
+
+/**
+ * 透過 opencode CLI 分析 git diff，產生 PR 標題與描述。
+ */
+export class OpenCode {
+  /**
+   * @param {object} opts
+   * @param {string} opts.baseUrl
+   * @param {string} opts.model
+   * @param {string} opts.provider
+   * @param {string} [opts.language]
+   */
+  constructor({ baseUrl, model, provider, language = 'Traditional Chinese (繁體中文)' }) {
+    this.baseUrl = baseUrl;
+    this.model = model;
+    this.provider = provider;
+    this.language = language;
+  }
+
+  /** 是否有足夠設定可以呼叫 opencode。 */
+  isConfigured() {
+    return Boolean(this.baseUrl && this.model && this.provider);
+  }
+
+  /**
+   * 在暫存目錄寫出 opencode.json，將自訂 provider 設為 OpenAI 相容端點。
+   *
+   * @returns {string} config 檔路徑
+   */
+  _writeConfig() {
+    const dir = mkdtempSync(join(tmpdir(), 'opencode-'));
+    const options = { baseURL: this.baseUrl };
+
+    const config = {
+      $schema: 'https://opencode.ai/config.json',
+      provider: {
+        [this.provider]: {
+          npm: '@ai-sdk/openai-compatible',
+          name: this.provider,
+          options,
+          models: {
+            [this.model]: { name: this.model },
+          },
+        },
+      },
+    };
+
+    const path = join(dir, 'opencode.json');
+    writeFileSync(path, JSON.stringify(config, null, 2));
+    return path;
+  }
+
+  /**
+   * 呼叫 opencode 產生標題與描述。
+   *
+   * @param {object} ctx
+   * @param {string} ctx.sourceBranch
+   * @param {string} ctx.targetBranch
+   * @param {string} ctx.commitMessages
+   * @param {string} ctx.diffStat
+   * @param {string} ctx.diff 已截斷的 diff
+   * @returns {Promise<{ title: string, description: string } | null>}
+   */
+  async summarize(ctx) {
+    if (!this.isConfigured()) {
+      log.warn('opencode 參數不完整（需要 base_url / model / provider），略過 AI 摘要');
+      return null;
+    }
+
+    const configPath = this._writeConfig();
+    const prompt = buildPrompt({ ...ctx, language: this.language });
+
+    log.info(`呼叫 opencode（${this.provider}/${this.model}）分析 diff...`);
+    const result = run(
+      'opencode',
+      ['run', '--model', `${this.provider}/${this.model}`, prompt],
+      {
+        cwd: tmpdir(),
+        env: {
+          ...process.env,
+          OPENCODE_CONFIG: configPath,
+          // 確保 opencode 有可寫的 HOME / 設定目錄
+          HOME: process.env.HOME || '/root',
+        },
+        timeout: 5 * 60 * 1000,
+      },
+    );
+
+    if (result.status !== 0) {
+      log.warn(`opencode 執行失敗 (${result.status})：${maskSecrets(result.stderr).slice(0, 500)}`);
+      return null;
+    }
+
+    const parsed = extractResult(result.stdout);
+    if (!parsed) {
+      log.warn('無法從 opencode 輸出解析出標題/描述');
+      return null;
+    }
+    return parsed;
+  }
+}
+
+function buildPrompt({ sourceBranch, targetBranch, commitMessages, diffStat, diff, language }) {
+  return [
+    `You are an assistant that writes high-quality Pull Request titles and descriptions.`,
+    `Analyze the following git changes for a PR merging branch "${sourceBranch}" into "${targetBranch}".`,
+    ``,
+    `Write the title and description in ${language}.`,
+    `The title should be a concise one-line summary (ideally following Conventional Commits style, e.g. "feat: ...").`,
+    `The description should be Markdown and include: a short summary, a bullet list of key changes, and any notable impact or risk.`,
+    ``,
+    `Respond with ONLY a single JSON object, no code fences, no extra text:`,
+    `{"title": "...", "description": "..."}`,
+    ``,
+    `=== Commits ===`,
+    commitMessages || '(no commit messages)',
+    ``,
+    `=== Changed files (stat) ===`,
+    diffStat || '(no stat)',
+    ``,
+    `=== Diff ===`,
+    diff || '(no diff)',
+  ].join('\n');
+}
+
+/** 去除 ANSI 控制碼。 */
+function stripAnsi(text) {
+  // eslint-disable-next-line no-control-regex
+  return text.replace(/\x1b\[[0-9;]*[a-zA-Z]/g, '');
+}
+
+/**
+ * 從 opencode 輸出中擷取含 title 的 JSON 物件並解析。
+ *
+ * @param {string} stdout
+ * @returns {{ title: string, description: string } | null}
+ */
+export function extractResult(stdout) {
+  const text = stripAnsi(stdout || '');
+
+  // 掃描所有平衡的 {...} 區塊，挑出第一個能成功解析且含 title 的物件
+  for (const candidate of findJsonObjects(text)) {
+    // LLM 常在字串值內輸出未跳脫的換行，先嘗試原始解析，失敗再嘗試修正
+    for (const variant of [candidate, escapeControlCharsInStrings(candidate)]) {
+      try {
+        const obj = JSON.parse(variant);
+        if (obj && typeof obj === 'object' && obj.title) {
+          return {
+            title: String(obj.title).trim(),
+            description: String(obj.description || '').trim(),
+          };
+        }
+      } catch {
+        // 試下一個變體 / 候選
+      }
+    }
+  }
+  return null;
+}
+
+/** 將字串值內未跳脫的控制字元（換行、tab 等）跳脫，修正 LLM 常見的無效 JSON。 */
+function escapeControlCharsInStrings(text) {
+  let out = '';
+  let inString = false;
+  let escape = false;
+  for (let i = 0; i < text.length; i++) {
+    const ch = text[i];
+    if (inString) {
+      if (escape) {
+        out += ch;
+        escape = false;
+        continue;
+      }
+      if (ch === '\\') {
+        out += ch;
+        escape = true;
+        continue;
+      }
+      if (ch === '"') {
+        out += ch;
+        inString = false;
+        continue;
+      }
+      if (ch === '\n') { out += '\\n'; continue; }
+      if (ch === '\r') { out += '\\r'; continue; }
+      if (ch === '\t') { out += '\\t'; continue; }
+      out += ch;
+    } else {
+      out += ch;
+      if (ch === '"') inString = true;
+    }
+  }
+  return out;
+}
+
+/** 以括號平衡方式找出文字中所有最外層的 {...} 區塊。 */
+function findJsonObjects(text) {
+  const objects = [];
+  let depth = 0;
+  let start = -1;
+  let inString = false;
+  let escape = false;
+
+  for (let i = 0; i < text.length; i++) {
+    const ch = text[i];
+    if (inString) {
+      if (escape) escape = false;
+      else if (ch === '\\') escape = true;
+      else if (ch === '"') inString = false;
+      continue;
+    }
+    if (ch === '"') {
+      inString = true;
+    } else if (ch === '{') {
+      if (depth === 0) start = i;
+      depth++;
+    } else if (ch === '}') {
+      depth--;
+      if (depth === 0 && start !== -1) {
+        objects.push(text.slice(start, i + 1));
+        start = -1;
+      }
+    }
+  }
+  return objects;
+}
diff --git a/app/lib/util.js b/app/lib/util.js
new file mode 100644
index 0000000..d0463d7
--- /dev/null
+++ b/app/lib/util.js
@@ -0,0 +1,72 @@
+import { spawnSync } from 'node:child_process';
+
+/**
+ * 執行外部指令並回傳結果（不會因為非零結束碼而 throw）。
+ *
+ * @param {string} command 要執行的指令
+ * @param {string[]} args 指令參數
+ * @param {object} [options] spawnSync 額外設定（cwd、env、input、maxBuffer...）
+ * @returns {{ status: number, stdout: string, stderr: string }}
+ */
+export function run(command, args = [], options = {}) {
+  const result = spawnSync(command, args, {
+    encoding: 'utf8',
+    maxBuffer: 64 * 1024 * 1024, // 64MB，避免大型 diff 被截斷
+    ...options,
+  });
+
+  if (result.error) {
+    return { status: 1, stdout: '', stderr: String(result.error.message || result.error) };
+  }
+
+  return {
+    status: typeof result.status === 'number' ? result.status : 1,
+    stdout: result.stdout || '',
+    stderr: result.stderr || '',
+  };
+}
+
+/**
+ * 執行外部指令，若結束碼非零則 throw。
+ *
+ * @param {string} command
+ * @param {string[]} args
+ * @param {object} [options]
+ * @returns {string} stdout（已 trim）
+ */
+export function runOrThrow(command, args = [], options = {}) {
+  const result = run(command, args, options);
+  if (result.status !== 0) {
+    const detail = (result.stderr || result.stdout || '').trim();
+    throw new Error(`指令失敗 (${result.status}): ${command} ${args.join(' ')}\n${detail}`);
+  }
+  return result.stdout.trim();
+}
+
+const ICONS = { info: 'ℹ️', warn: '⚠️', error: '❌', success: '✅', step: '▶️' };
+
+/** 簡單的分級日誌輸出。 */
+export const log = {
+  info: (msg) => console.log(`${ICONS.info}  ${msg}`),
+  warn: (msg) => console.log(`${ICONS.warn}  ${msg}`),
+  error: (msg) => console.error(`${ICONS.error}  ${msg}`),
+  success: (msg) => console.log(`${ICONS.success}  ${msg}`),
+  step: (msg) => console.log(`\n${ICONS.step}  ${msg}`),
+};
+
+/**
+ * 將敏感字串（如 token）從文字中遮蔽，避免寫入日誌。
+ *
+ * @param {string} text
+ * @param {string[]} secrets
+ * @returns {string}
+ */
+export function maskSecrets(text, secrets = []) {
+  let masked = String(text ?? '');
+  for (const secret of secrets) {
+    if (secret && secret.length >= 4) {
+      masked = masked.split(secret).join('***');
+    }
+  }
+  return masked;
+}
diff --git a/app/package.json b/app/package.json
new file mode 100644
index 0000000..136121a
--- /dev/null
+++ b/app/package.json
@@ -0,0 +1,14 @@
+{
+  "name": "ai-pull-request",
+  "version": "1.0.0",
+  "description": "使用 opencode 分析 git diff 自動產生 PR 標題與描述，並透過 Gitea API 建立 Pull Request",
+  "type": "module",
+  "main": "index.js",
+  "scripts": {
+    "start": "node index.js"
+  },
+  "engines": {
+    "node": ">=18"
+  },
+  "license": "MIT"
+}
diff --git a/entrypoint.sh b/entrypoint.sh
index c8c429c..9a8fb15 100644
--- a/entrypoint.sh
+++ b/entrypoint.sh
@@ -1,11 +1,9 @@
 #!/bin/bash
+set -euo pipefail
 
-echo "Gitea Server Url: $GITEA_SERVER_URL"
+echo "🚀 ai-pull-request action 啟動"
+echo "   Repository: ${GITEA_REPOSITORY:-?}"
+echo "   ${SOURCE_BRANCH:-?} → ${TARGET_BRANCH:-?}"
 
-echo "Gitea Repository: $GITEA_REPOSITORY"
-
-echo "Gitea Token: $GITEA_TOKEN"
-
-echo "Text: $TEXT"
-
-echo "text=$TEXT" >> "$GITHUB_OUTPUT"
\ No newline at end of file
+# Node.js 應用程式進入點
+exec node /app/index.js