●Change8

Migrating to Remix remix@3.0.0-beta.4

Version remix@3.0.0-beta.4 introduces 2 breaking changes. This guide details how to update your code.

Released: 6/5/2026

2
Breaking Changes
2
Migration Steps
23
Affected Symbols

⚠️ Check Your Code

If you use any of these symbols, you need to read this guide:

remix/routerremix/fetch-routernext()Responserouter.mount()RouteBuilderRouteInstallerRouterContextRouterTypes.contextcreateAction()createController()MiddlewareContextcreateMiddleware()MiddlewarecreateRouter()router.map()MapTargetMapHandlerremix/assertassert.okassert.partialDeepEqualremix/testt.signal

Breaking Changes

●Issue #1

Middleware consumed through `remix/router` and `remix/fetch-router` must now explicitly continue the request chain by calling `next()` or return a `Response`. Middleware that returned `undefined` without calling `next()` now throws at runtime instead of implicitly continuing. Fix by ensuring middleware returns `next()` or a `Response`.

●Issue #2

`MapTarget` and `MapHandler` are no longer re-exported from `remix/router` or `remix/fetch-router`. Use the public `Router`, `RouteBuilder`, `RouteInstaller`, `Action`, and `Controller` types instead.

Migration Steps

  1. 1
    Update context-loading middleware in `remix/router` or `remix/fetch-router` to explicitly return the downstream response, typically by calling `return next()`.
  2. 2
    Replace usage of re-exported `MapTarget` and `MapHandler` with the public `Router`, `RouteBuilder`, `RouteInstaller`, `Action`, and `Controller` types.

Release Summary

This pre-release introduces significant router enhancements, including route mounting capabilities and improved middleware contract enforcement, alongside better Node assertion compatibility.

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