---
title: "next Breaking Changes on npm | Since.dev"
description: "What each next release removed, renamed or changed: 142 breaking changes in 55 versions on npm, each with its source."
canonical_url: https://since.dev/packages/npm/next
last_updated: 2026-10-06
---

# next breaking changes

Every breaking API change we have recorded in next on npm: 142 breaking changes in 55 versions. Below are its newest 6 versions, removals and renames first, each with its source.

Newest change October 6, 2026

## 16.4.0

1 breaking change, first published October 6, 2026.

- **Signature changed** `NextConfig.partialPrefetching`  

Was partialPrefetching?: boolean | 'unstable_eager'; now partialPrefetching?: boolean. [npmjs.com](https://www.npmjs.com/package/next/v/16.4.0)

## 16.4.0-canary.56

1 breaking change, first published October 6, 2026.

- **Default changed**  

Builds now mangle export names by default with Turbopack. Code relying on export names at runtime may be affected. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.56)

## 16.4.0-canary.55

2 breaking changes, first published October 6, 2026.

- **Behavior changed**  

An explicitly set generateBuildId is now always used for the build ID. Check custom build ID logic. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.55)
- **Default changed** `experimental.turbopackSharedRuntime`  

experimental.turbopackSharedRuntime is now on by default. Set it to false to keep the previous behavior. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.55)

## 16.4.0-canary.54

2 breaking changes, first published October 6, 2026.

- **Removed** `agentUpgrade`  

The agentUpgrade option no longer accepts true. Remove or change that setting in your config. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.54)
- **Behavior changed**  

Next data paths are matched case-sensitively now. Requests that relied on case-insensitive matching may change. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.54)

## 16.4.0-canary.38

1 breaking change, first published October 6, 2026.

- **Behavior changed**  

Routes are matched strictly by default in this canary. Check routes that relied on looser matching. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.38)

## 16.4.0-canary.26

2 breaking changes, first published October 6, 2026.

- **Behavior changed**  

Interception routes now require canonical route targets. Routes that previously worked with non-canonical paths may now fail and need to be updated. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.26)
- **Behavior changed**  

App pages that do not match any route now produce an error. Users with unmatched app pages must add matching routes. [github.com](https://github.com/vercel/next.js/releases/tag/v16.4.0-canary.26)

## Check your code

These are the changes. To see which of them reach your code, [scan a public repository](https://since.dev/scan.md), or have your coding agent call `check_code` with your manifest or lockfile over [MCP](https://since.dev/docs.md#mcp). [The API](https://since.dev/docs.md#api) reads every change in every version, not only the newest. On Team and up, a fix pull request opens for the changes that reach a connected repository. Nothing merges or deploys.

## Put your code on continuous management.

Scan a public repository now, or give your agent one line.

### See how out of date your code is.

[Scan a repository](https://since.dev/scan.md). Any public GitHub repository. No sign-in.

### Tell your agent what changed since it was trained.

`claude mcp add --transport http since https://api.since.dev/mcp`

---

Every page on this site as Markdown: https://since.dev/sitemap.md. For agents: https://since.dev/llms.txt.