In wrangler dev, calling ctx.storage.setAlarm() from inside a Durable Object facet of a SQLite-backed DO appears to succeed, then asynchronously breaks the whole actor with:

Error: alarms are not yet implemented for SQLite-backed Durable Objects

The error does not throw from the setAlarm() call. It surfaces as the rejection of an unrelated in-flight RPC into the facet, with no facet-side stack frames.

Minimal repro: https://github.com/firtoz/facet-alarm-repro

Repro

git clone https://github.com/firtoz/facet-alarm-repro
cd facet-alarm-repro
npm install
npx wrangler dev

curl 'http://127.0.0.1:8799/repro'
curl 'http://127.0.0.1:8799/repro?facetAlarm=off'

Expected:

• /repro should either complete, or setAlarm() inside the facet should throw synchronously with a clear "facet alarms are unsupported" error.
• /repro?facetAlarm=off should complete.

Actual:

• /repro returns ok: false; the host -> facet RPC rejects with alarms are not yet implemented for SQLite-backed Durable Objects.
• /repro?facetAlarm=off completes normally.

Important detail

The facet's setAlarm() call logs success before the actor breaks:

{"tag":"leaf:hold:start","ms":4000,"setAlarm":true}
{"tag":"leaf:setAlarm:ok"}

So userland cannot catch this at the alarm call site.

Environment

• Reproduced on wrangler 4.85.0 through 4.100.0.
• compatibility_date: 2026-04-24
• SQLite-backed DO via new_sqlite_classes
• Facet spawned with ctx.facets.get(name, () => ({ class: ctx.exports.Leaf }))
• Linux x64

Likely source

From workerd source:

• src/workerd/server/server.c++: facet actors (parent != kj::none) get ActorSqlite::Hooks::getDefaultHooks() with a TODO: Support alarms in facets, somehow.
• src/workerd/io/actor-sqlite.c++: default Hooks::scheduleRun() throws alarms are not yet implemented for SQLite-backed Durable Objects.

It looks like the output-gate commit path calls scheduleRun() after the JS setAlarm() call has already resolved, breaking the actor asynchronously.

Why this matters

Frameworks like agents / Think use alarms for keep-alive and scheduling. If such framework code runs inside a facet, the actor can be broken by a successful-looking setAlarm() call, and the error appears elsewhere as an unrelated RPC failure.

Suggested fix

Either:

1. Support facet alarms in local workerd; or
2. Make setAlarm() on facet storage throw synchronously at the call site in local dev, with an error that explicitly says alarms are unsupported in facets.