## Background
A 5000-chat scaletest (~50k turns, ~2m45s wall time) completed
successfully,
but the main bottleneck was **DB pool starvation from repeated reads**,
not
individually expensive SQL. The push/webpush path showed a few
especially noisy
reads:
- `GetLastChatMessageByRole` for push body generation
- `GetEnabledChatProviders` + `GetChatModelConfigByID` for push summary
model
resolution
- `GetWebpushSubscriptionsByUserID` for every webpush dispatch
This PR keeps the optimizations that remove those duplicate reads while
leaving
stream behavior unchanged.
## What changes in this PR
### 1. Reuse resolved chat state for push notifications
`maybeSendPushNotification` used to re-read the last assistant message
and
re-resolve the chat model/provider after `runChat` had already done that
work.
Now `runChat` returns the final assistant text plus the already-resolved
model
and provider keys, and the push goroutine uses that state directly.
That removes the extra push-path reads for:
- `GetLastChatMessageByRole`
- the second `resolveChatModel` path
- the provider/model lookups that came with that second resolution
### 2. Cache webpush subscriptions during dispatch
`Dispatch()` previously hit `GetWebpushSubscriptionsByUserID` on every
push. A
small per-user in-memory cache now avoids those repeated reads.
The follow-up fix keeps that optimization correct: `InvalidateUser()`
bumps a
per-user generation so an older in-flight fetch cannot repopulate the
cache with
pre-mutation data after subscribe/unsubscribe.
That preserves the cache win without letting local subscription changes
be
silently overwritten by stale fetch results.
## Why this is safe
- The push change only reuses data already produced during the same chat
run. It
does not change notification semantics; if there is no assistant text to
summarize, the existing fallback body still applies.
- The webpush change keeps the existing TTL and `410 Gone` cleanup
behavior. The
generation guard only prevents stale in-flight fetches from poisoning
the
shared cache after invalidation.
- The final PR does **not** change stream setup, pubsub/relay behavior,
or chat
status snapshot timing.
## Deliberately not included
- No stream-path optimization in `Subscribe`.
- No inline pubsub message payloads.
- No distributed cross-replica webpush cache invalidation.
Replace manual experiment checks in web-push handlers with the
`RequireExperimentWithDevBypass` middleware on the route group, matching
the pattern used by OAuth2, Agents, and MCP experiments.
## Changes
- **`coderd/coderd.go`**: Add `RequireExperimentWithDevBypass`
middleware to `/webpush` route group
- **`coderd/webpush.go`**: Remove inline
`api.Experiments.Enabled(codersdk.ExperimentWebPush)` checks from all
three handlers
- **`cli/server.go`**: Gate webpush dispatcher initialization with
`buildinfo.IsDev()` fallback so dev builds always init the real
dispatcher
- **`coderd/webpush_test.go`**: Remove experiment enablement from tests
(dev bypass handles it)
Net effect: -26 lines removed, +5 added.
Created using whatchamacallits (Opus 4.6 Max)
## Summary
`deleteUserWebpushSubscription` in `coderd/webpush.go` had incorrect
error handling that masked database errors as 404 responses.
## Bug
`GetWebpushSubscriptionsByUserID` is a `:many` query — it returns `([],
nil)` when no rows match, never `sql.ErrNoRows`. The previous `if/else
if` chain:
```go
if existing, err := api.Database.GetWebpushSubscriptionsByUserID(ctx, user.ID); err != nil && errors.Is(err, sql.ErrNoRows) {
// dead code — :many queries never return sql.ErrNoRows
} else if idx := slices.IndexFunc(existing, ...); idx == -1 {
// real DB errors fall through here, existing is nil, idx is -1 → 404
}
```
Any real database error (connection failure, timeout, authorization
error) fell through to the `else if` branch where `slices.IndexFunc(nil,
...)` returns `-1`, returning 404 "subscription not found" instead of
500.
## Fix
Split into two separate checks so database errors properly return 500:
```go
existing, err := api.Database.GetWebpushSubscriptionsByUserID(ctx, user.ID)
if err != nil {
// 500
}
if idx := slices.IndexFunc(existing, ...); idx == -1 {
// 404
}
```
## Testing
Added `TestDeleteWebpushSubscription/database_error_returns_500` which
wraps the DB store to inject an error into
`GetWebpushSubscriptionsByUserID` and asserts the handler returns 500
(not 404).
* Adds `codersdk.ExperimentWebPush` (`web-push`)
* Adds a `coderd/webpush` package that allows sending native push
notifications via `github.com/SherClockHolmes/webpush-go`
* Adds database tables to store push notification subscriptions.
* Adds an API endpoint that allows users to subscribe/unsubscribe, and
send a test notification (404 without experiment, excluded from API docs)
* Adds server CLI command to regenerate VAPID keys (note: regenerating
the VAPID keypair requires deleting all existing subscriptions)
---------
Co-authored-by: Kyle Carberry <kyle@carberry.com>
Ethan