## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work.
> - The web UI registers a service worker (`/sw.js`) that caches the app
shell for an offline fallback.
> - Browsers only re-fetch a worker script on navigation or a ~24h
timer, and Paperclip is a parked-tab SPA: a tab can sit open for weeks
without one navigation.
> - An installed worker — and the shell it cached — can therefore keep
serving an old bundle long after a deploy, and the server let `sw.js`
inherit the generic 1h static TTL on top of that.
> - This pull request adds explicit update checks (tab-visible +
hourly), applies a discovered update with one reload while the tab is
hidden, and serves `sw.js` with `Cache-Control: no-cache`.
> - The benefit is that a deploy reaches every open tab within about an
hour, instead of some tabs silently running stale UI indefinitely.
## Linked Issues or Issue Description
Refs #11292 (the network-first `sw.js` fallback fix; this PR closes the
delivery gap that can keep clients pinned on a pre-#11292 worker).
**What happened?**
A browser that had an older cache-first worker installed kept rendering
a stale app shell — old feature set, old naming — while the server was
verified to be running the current release. Nothing on the client checks
for a new worker outside navigations, so a parked tab never picked up
the fixed worker, and `sw.js` was served with a 1h cache TTL that
further delayed update checks.
**Expected behavior**
Every open tab converges to the deployed bundle shortly after a release,
without users unregistering workers in DevTools or hard-reloading.
**Steps to reproduce**
Install a build's service worker, deploy a newer build, and leave the
tab parked (no navigation): the tab keeps running the old bundle
indefinitely; the worker update check only happens if the user
navigates, and even then a cached `sw.js` can answer it.
## What Changed
- New `ui/src/lib/service-worker-updates.ts`: registers `/sw.js`, runs
`registration.update()` when the tab becomes visible and on an hourly
timer, and on `controllerchange` of a previously-controlled page applies
the update with a single reload — only while the tab is hidden, so an
update never yanks the page mid-session; a takeover while visible defers
the reload to the next hidden transition. First-ever installs never
reload.
- `ui/src/main.tsx`: replaces the fire-and-forget `register()` with the
new module.
- New `server/src/static-ui-cache.ts` (`staticUiCacheControl`):
`index.html` and `sw.js` are served `Cache-Control: no-cache`; other
non-hashed statics keep the 1h default. `server/src/app.ts` uses it in
the static middleware.
## Verification
- `npx vitest run ui/src/lib/service-worker-updates.test.ts` — 8 tests:
registration, hidden-takeover reload (once), deferred reload on visible
takeover, no reload on first install, visibility-triggered and
timer-triggered update checks, cleanup, no-container no-op.
- `npx vitest run server/src/__tests__/static-ui-cache.test.ts` — 3
tests incl. the `sw.js.map` lookalike keeping the default TTL.
- `tsc -b` (ui) and `tsc --noEmit` (server) clean; `pnpm check:tokens`
clean.
## Risks
- Behavioral shift: tabs now reload once, while hidden, after a deploy
lands. Unsaved in-page state in a hidden tab is lost at that moment —
the same exposure as a browser discarding a background tab, which SPAs
must already tolerate.
- Self-hosted behavior is otherwise unchanged: same worker script, same
registration URL, one added conditional header.
- Low risk on the server side: the header change only widens
revalidation.
## Model Used
Claude Fable 5 (`claude-fable-5`, Anthropic) via Claude Code — agentic
coding session with tool use and extended thinking.
## Checklist
- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have checked ROADMAP.md and confirmed this PR does not duplicate
planned core work
- [x] I have searched GitHub for duplicate or related PRs and linked
them above
- [x] I have either (a) linked existing issues with `Fixes: #` / `Closes
#` / `Refs #` OR (b) described the issue in-PR following the relevant
issue template
- [x] I have not referenced internal/instance-local Paperclip issues or
links (only public GitHub `#NNN` / `github.com/paperclipai/paperclip`
URLs)
- [x] My branch name describes the change (e.g. `docs/...`, `fix/...`)
and contains no internal Paperclip ticket id or instance-derived details
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [x] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [ ] All Paperclip CI gates are green
- [ ] Greptile is 5/5 with no open P2s, recommendations, or follow-ups
- [x] I will address all Greptile and reviewer comments before
requesting merge
Devin Foley