Route files in React Router only get server-code stripped from a
specific set of exports (loader/action/middleware/headers). The
overpass failover work added a `fetchWithFailover` named export to
`app/routes/api.overpass.ts` for unit tests, but that export pulls
in `metrics.server` (prom-client registry, etc.) — which then
leaks into the client bundle and fails the production build with:
[plugin react-router:dot-server]
Error: Server-only module referenced by client
'app/lib/metrics.server' imported by route 'app/routes/api.overpass.ts'
Move the upstream fetch logic and its config constants into
`app/lib/overpass.server.ts`. The `.server.ts` naming makes the
server-only boundary explicit, and tests now import from the lib
instead of from the route. The route keeps only its `action` export
(plus the per-instance LRU cache, which is internal to the module
and not exported).
Tests: 85 passing (no behavior changes). Build: planner + journal
both succeed. Typecheck + lint clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
