The reserve_write_cp undrained-ack refusal returned a bare
HiCacheWriteFailure, which _reserve_write_cp_indices_no_collective
interpreted as a host-capacity failure: with free host space the
retry path tripped the predicted-no-deficit RuntimeError (crashing
the scheduler in exactly the scenario the gate exists to handle
gracefully), and with a deficit it triggered pointless evictions
before refusing again.
Give HiCacheWriteFailure an explicit reason (default host_capacity
keeps all existing constructors/semantics); the wrapper returns
non-capacity failures immediately as skip-this-round, and a
wrapper-level test pins that undrained_ack reaches neither the retry
admission nor host eviction.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
leavelet
ecf7998c80