The request-scoped capture kept the last verdict of any kind and fell back
to it when nothing had refused. That fallback fires in exactly one state —
no limiter refused this request — which is the definition of "this 429 came
from somewhere else". So a daily AI budget that is spent until midnight, an
hourly generation quota, and a provider-side 429 relayed onward all went out
carrying our own bucket's numbers: a remainder that says there is room left
and a Retry-After measured against an unrelated window. On the AI paths the
captured window can also expire while the provider call runs, so the dressed
delay could land at zero and tell the client to retry immediately into the
ceiling that had just refused it.
The cell now keeps refusals only. A request every bucket let through reports
nothing, and a 429 from another cause leaves undressed, which is correct:
there is no bucket to describe. The two-limiter rule is unchanged — the last
refusal wins, and a refusal still outranks a pass.
The unit case that pinned the fallback is turned round, and both directions
now run through the real wrapper: a limiter refusal gets the headers, a 429
raised without one gets none. The integration file gains the two shapes it
was missing — a route that consults two buckets must report the one that
refused, and a route whose 429 comes from the daily budget must carry no
rate-limit headers at all.
A refused client had nothing to back off against. `rateLimitHeaders()`
emitted `X-RateLimit-Remaining` and an ISO `X-RateLimit-Reset`, no
`Retry-After` and no cap, and only about 70 of the 199 route files that
consult a limiter attached even those two. The rest answered with a bare
prose envelope, including every endpoint an offline replay queue hits:
the four batch ingests, `/api/sync/changes` and `/api/auth/refresh`. A
first-run Apple Health import trips the 60-per-minute batch ceiling
reliably, and the only strategy left to the client was a blind backoff.
Threading headers through 129 handlers is 129 edits the next new route
forgets, so the verdict is carried instead: `checkRateLimit` records it
in a request-scoped cell and `apiHandler` dresses any 429 that leaves
without headers. A route that already built its own is left alone —
`Retry-After` is the presence test, and it comes from the same builder.
`Retry-After` is whole seconds rounding UP (RFC 9110 §10.2.3), floored
at zero. `X-RateLimit-Limit` is new and needs the cap, so the limiter
result carries it. `X-RateLimit-Reset` keeps its ISO form: it is the
wrong convention for the name, but it is on the wire today and changing
it is a decision of its own.
The cell lives in its own leaf module because 177 test files replace
`@/lib/rate-limit` wholesale with a mock factory, and `apiHandler` must
not depend on anything those factories stand in for.
Marc-André Bombeck