# 将 Next.js 14 应用迁移到 Next.js 16 的提示

> 结构化 AI 代理提示，用于将 Next.js 14 App Router 项目迁移到 Next.js 16，处理破坏性变更并分步进行。

**Type:** Prompt  
**Tools:** Cursor, Claude Code, Codex, Windsurf  
**Stack:** Next.js, TypeScript  
**Difficulty:** hard  
**Updated:** 2026-06-08

---

使用此提示来驱动一个谨慎、渐进的 Next.js 14 到 16 迁移——处理异步 `params`/`searchParams` API 变更、React 19 对等依赖以及升级前已弃用的 `next/headers` 模式。

## Main Prompt

```txt title="Main Prompt"
You are migrating an existing Next.js 14 App Router project to Next.js 16.

Do this in the following ordered steps — do not skip steps or combine them.

Step 1 — Audit (read-only):
  - List every file that uses `params` or `searchParams` as synchronous props.
  - List every file that calls `cookies()`, `headers()`, or `draftMode()` without `await`.
  - List every `next/image` usage with a deprecated prop (e.g., `layout`, `objectFit`).
  - List the current `peerDependencies` for React and React DOM.
  Output the audit as a plain list. Stop and wait for my review.

Step 2 — Update deps:
  - Run: `bun add next@16 react@19 react-dom@19 @types/react@19 @types/react-dom@19`
  - Do NOT change any source files in this step.

Step 3 — Fix async params:
  - For every Page, Layout, and `generateMetadata` function that receives `params` or
    `searchParams`, make the function `async` and `await` the prop before use.
  - Type the props as `Promise<{ slug: string }>` (or the relevant shape), not `{ slug: string }`.

Step 4 — Fix async dynamic APIs:
  - Add `await` before every call to `cookies()`, `headers()`, and `draftMode()`.
  - If the call is inside a non-async function, make that function async.

Step 5 — Fix deprecated Image props:
  - Remove `layout="fill"` and replace with `fill` (boolean).
  - Remove `objectFit` and `objectPosition` props and move them to a `className` or `style`.

Step 6 — Verify:
  - Run `bun run typecheck` and fix all remaining TypeScript errors.
  - Run `bun run build` and confirm exit 0.

After each step, show the diff and wait for confirmation before proceeding.
```

## 实现说明

- 在 Next.js 15+ 中，`params` 和 `searchParams` 被 `Promise` 包裹。同步访问它们会编译通过但在运行时抛出错误——因此在升级前，第一步的审计至关重要。
- `cookies()` 和 `headers()` 在 Next.js 15+ 中是异步的；最常见的失败模式是在未标记为 `async` 的函数内部调用它们。
- React 19 移除了部分遗留 API（函数组件上的 `defaultProps`、字符串 refs）。在每个步骤之间运行 `bun run typecheck` 以尽早发现这些变化。

## 预期文件更改

```txt
package.json                          (edited — next, react, react-dom versions)
bun.lock / package-lock.json          (edited automatically)
src/app/**/page.tsx                   (edited — async params)
src/app/**/layout.tsx                 (edited — async params)
src/app/**/generateMetadata           (edited — async params)
src/components/**/*.tsx               (edited — deprecated Image props)
```

## 验收标准

- 所有步骤完成后，`bun run typecheck` 退出码为 0。
- `bun run build` 退出码为 0，且无关于已弃用 API 的警告。
- 所有动态路由在 `bun run dev` 中正确渲染。
- 没有同步访问 `params` 或 `searchParams` 属性。

## 测试命令

```bash
bun run typecheck
bun run build
bun run dev
# visit several dynamic routes and confirm no runtime errors
grep -r "layout=\"fill\"" src/ && echo "FAIL: deprecated Image prop found"
grep -rn "cookies()\|headers()\|draftMode()" src/ | grep -v "await" && echo "WARN: unawaited dynamic API"
```

## 常见 AI 错误

- 跳过审计步骤并一次性完成所有更改，导致难以追踪的错误。
- 将异步 params 类型写为 `{ params: { slug: string } }` 而不是 `{ params: Promise<{ slug: string }> }`。
- 忘记同时升级 `@types/react` 和 `react`，导致类型不匹配。
- 在本身不是异步的嵌套辅助函数内部未对 `cookies()` 使用 await。

## 修复提示

```txt title="Fix Prompt"
The build fails with type errors on params or a runtime error about cookies/headers.
Fix in order:
1. For any page or layout receiving `params`, update the prop type to `Promise<{ slug: string }>` and
   add `const { slug } = await params;` at the top of the function body.
2. Find every call to `cookies()`, `headers()`, `draftMode()` not preceded by `await` and add it.
   Make the containing function async if it isn't already.
3. Run `bun run typecheck` and show me only the remaining errors.
```