When `mapUpstreamError` produced the final 502/503/504, it only carried
`{triedKeys, triedUpstreams, lastStatusCode}` in `details`. The upstream
response body was `.cancel()`'d on the wire and the network error
message vanished into the catch arm — operators staring at a 502 had no
way to tell "OpenRouter region-blocked us" from "key revoked" from
"DNS failed" without re-probing the upstream by hand.
Now each recorded failure carries the diagnostic snippet:
- chat upstreams read at most 256 bytes of the failed body via a
drain-aware reader before cancelling the rest (socket still returns
to the pool, no fallback-storm pool exhaustion).
- TTS upstreams reuse `errorMessageFrom(err)` — adapters already bake
the status + body snippet into `err.message`, so one field carries
both.
- network / timeout attempts record `errorMessageFromUnknown(err)` so
"attempt-timeout" vs "ECONNRESET" vs "DNS failed" stays
distinguishable.
The collected `UpstreamAttempt[]` is attached to `ApiError.cause`
rather than `details`. SEC-5 (no upstream content in client-facing
response body) still holds — only the server-side logger + OTel pick
the cause up. `app.onError` now logs `{details, cause}` together so a
single log line tells the operator both the contract-level summary
and the actual upstream payload.
Adds a router.test.ts regression covering both shapes (HTTP 401 body
snippet + network ECONNRESET errorMessage), with an explicit assertion
that `details` does NOT contain the body text so SEC-5 doesn't drift.
RainbowBird
46fb391330