The search page fetched LA averages with cache: 'force-cache', which serves
any stored response, however old, without asking the server. One failed
request (a staging deploy restart; the July proxy outage) was stored and
replayed on every later visit, and the error was swallowed, so the
"vs LA avg" delta silently vanished from every secondary row in that
browser. A Playwright profile still held a 500 dated 5 July.
The default cache mode honours the API's Cache-Control (five minutes), so
a good answer is still reused and an error never is. Browsers holding a
stored failure recover on their next visit.
A journey now checks that a mainstream secondary's row shows the
comparison: nothing did, which is how it could go missing unnoticed.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
