## Thinking Path
> - Paperclip is the open source app people use to manage AI agents for
work
> - The UI registers a service worker (`ui/public/sw.js`) with a
network-first fetch handler whose cache is an offline fallback
> - The fallback hands `event.respondWith` the result of
`caches.match(...)`, which resolves `undefined` on a cache miss — and in
the navigation branch, `caches.match("/") || offlineResponse` never uses
the fallback because `caches.match` returns a promise, which is always
truthy
> - When the network fetch rejects (server restart, deploy, brief
outage) and the cache misses, the browser fails the request with
`Uncaught (in promise) TypeError: Failed to convert value to
'Response'`, so navigation breaks outright instead of degrading to the
offline page
> - This pull request awaits the cache lookups and guarantees a real
`Response` on every path
> - The benefit is that brief server unavailability degrades to the
offline fallback instead of a dead navigation
## Linked Issues or Issue Description
No existing issue. Description follows the bug template:
**What happened?**
Navigating while the server was briefly unavailable (mid-restart)
produced `The FetchEvent for "…" resulted in a network error response:
the promise was rejected.` and `sw.js:1 Uncaught (in promise) TypeError:
Failed to convert value to 'Response'.` The navigation failed instead of
showing the offline fallback.
**Expected behavior**
A failed navigation serves the cached app shell when present, otherwise
the "Offline" 503 response. A failed asset fetch serves its cache entry
when present, otherwise a proper network-error response. `respondWith`
always receives a real `Response`.
**Steps to reproduce**
1. Load the app so `sw.js` is active; ensure `/` is not in the service
worker cache (fresh cache version).
2. Restart or stop the backend.
3. Navigate to any page: the fetch rejects, `caches.match` misses, and
the browser logs the conversion TypeError with a failed navigation.
## What Changed
- `ui/public/sw.js`: the fetch fallback awaits `caches.match(...)` and
returns the "Offline" 503 for navigations and `Response.error()` for
assets when the cache misses.
- `ui/src/lib/sw-offline-fallback.test.ts`: evaluates the real `sw.js`
in a sandboxed scope and covers the three fallback paths; the two
miss-path tests fail against the previous code.
## Verification
- `pnpm vitest run src/lib/sw-offline-fallback.test.ts` in `ui/` — 3
tests pass.
- Verified both miss-path tests fail against the unmodified `sw.js`.
## Risks
Low risk. The change only affects the fetch-rejection path; successful
fetches and cache hits behave exactly as before. `Response.error()`
mirrors what the browser would produce for an unhandled failed no-cors
fetch.
## Model Used
- Claude (Anthropic), Claude Fable 5 (`claude-fable-5`), via Claude Code
CLI with tool use (code search, edit, test execution).
## 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
01112c350c
