command() ignores reroute hook — event.route.id reflects un-rerouted path

[half2me]

Describe the bug

When using SvelteKit's experimental command() (remote functions) from a page that is served via a reroute hook, event.route.id inside the command is null instead of the matched route.

Page navigation correctly resolves event.route.id via the reroute hook. But when a command() is invoked from that same page, event.route.id is null.

Reproduction

Minimal repo: https://github.com/half2me/sveltekit-reroute-command-bug

git clone https://github.com/half2me/sveltekit-reroute-command-bug
cd sveltekit-reroute-command-bug
pnpm install
pnpm dev

1. Navigate to http://localhost:5173/original
   • The page loads correctly — the reroute hook maps /original → /actual
   • In the terminal: [hooks.server] GET /original → route.id: /actual
2. Click "Call command()"
3. The page shows event.route.id: null — BUG

Navigate to /actual directly and click the button to verify — in that case event.route.id is correctly /actual.

Setup:

• src/hooks.ts — reroute hook: /original → /actual
• src/routes/actual/+page.svelte — page with a button calling a command()
• src/lib/get-route-info.remote.ts — command that returns event.route and event.url

Logs

Page load (correct):

[hooks.server] GET /original → route.id: /actual

Command call (bug):

event.route.id: null
event.url.pathname: /original

Expected behavior

event.route.id should be /actual inside the command(), same as during page navigation.

Actual behavior

event.route.id is null.

Real-world impact

This breaks any handle hook logic that uses event.route.id for command() requests. In our production app we use subdomain-based routing via reroute:

// hooks.ts — reroutes acme.example.com/ → /o/acme
export const reroute: Reroute = ({ url }) => {
  const subdomain = getSubdomain(url.hostname);
  if (subdomain) return `/o/${subdomain}${url.pathname}`;
};

// hooks.server.ts — skips auth for static marketing pages
const handleAuth: Handle = async ({ event, resolve }) => {
  if (event.route.id?.includes('(static)')) return resolve(event);
  // ... set up session ...
};

When a command() is called from acme.example.com/, event.route.id is null instead of /o/[slug]. In our case the un-rerouted / path happened to match a /(static) route group, causing the auth hook to break things.

System Info

SvelteKit 2.55.0
Svelte 5.53.13
Vite 8.0.0
TypeScript 5.9.3
macOS 15.5

Severity

serious, but I can work around it

Additional Information

• Page loads (GET requests) correctly apply the reroute hook
• Only command() POST requests are affected
• The handle hook in hooks.server.ts does run for command requests, but event.route.id is already null by the time it executes

[half2me]

Clarification: the bug is that reroute is skipped entirely, not just that route.id is null

The null in the minimal repro is a side effect — the real bug is that command() completely ignores the reroute hook when resolving the route.

In the repro, /original has no matching route without reroute, so route.id is null. But in production this is worse: the un-rerouted path can match a different, wrong route. In our case:

• User is on acme.example.com/ (subdomain, rerouted to /o/acme → route /o/[slug])
• command() sends the un-rerouted pathname /
• Server skips reroute and matches / against the /(static) home page route
• event.route.id = /(static) instead of /o/[slug] — silent mismatch

This caused our auth hook to skip session setup (it skips (static) routes as a perf optimization), breaking things for logged-in users.

Docs reference

The reroute docs state:

This function runs before handle and allows you to change how URLs are translated into routes. The returned pathname is used to select the route and its parameters.

No exception is mentioned for remote functions. The reroute hook should apply to route resolution for all request types.

Source code trace

In respond.js, the reroute hook is explicitly skipped for remote function requests behind an if (!remote_id) guard. The client sends the page's original url.pathname (via x-sveltekit-pathname header), and the server uses it directly for route matching without applying reroute.