Observed

Source-reviewed: the exception mapping exists, but asyncio.CancelledError bypasses all three of LiteLLM's exception-handling layers — a DNS cancellation yields a bare 500 with no retry, no fallback, and no log entry (#22100, still open as of 2026-06-11); pass-through paths erase upstream exception types (a provider 401 surfaces as a gateway 500); upstream Retry-After headers are not forwarded to clients under the standard header (#21553, stale-bot closed not-planned 2026-05-29; fix PR #21648 closed unmerged).