The decode stall is step contention (measured: 18.7 ms decode-only steps
against 317 ms steps that carry a prefill chunk, decode at 13 t/s median
while prefill runs), and the two engine knobs that fix it arrived after this
endpoint's pin. Moving to 1.8.1 (2026-10-18) brings both, and brings two CLI
breaks with them:
- --vram-weights-mib / --vram-kv-mib were REMOVED at 1.3.0. The per-card
split between the expert slab and the KV pool is now derived by the
engine's budget resolver from --gpu-headroom-mib, the cache bound
(--max-model-len, --max-num-seqs) and --host-pool-mib, and the cache may
lend idle blocks to the expert slab. The slab size and the pool's token
count are boot-ledger lines from here on, so the capacity contract
(3 x 200,000 fp8) is verified live by the probe's capacity leg instead of
computed from an env number.
- The prefix cache has no disk tier any more: --prefix-cache-dir and
--prefix-cache-disk-mib are refusals and --prefix-cache-host-mib is
--prefix-cache-mib. 64 GiB of parked KV on NVMe becomes re-prefill, so
prefix_hit_rate is the thing to watch after this boot.
env: image re-pinned to the 1.8.1 digest; the pair and the disk tier dropped;
FRANK_ARCHON_PREFIX_CACHE_MIB replaces the host/disk pair; new
FRANK_ARCHON_BUSY_PREFILL_CHUNK=auto (explicit, because auto vs off is the
difference between decode waiting one chunk and waiting a whole step) and
FRANK_ARCHON_PREFILL_INTERLEAVE=0 (opt-in through a guarded argv array).
serve: argv follows the new CLI, /data mount and the pre-created kvcache path
go with the disk tier, and the retired env keys are no longer required (they
would abort ExecStart). autoresearch-frank-archon.sh takes the same CLI, with
a cold prefill now coming from --prefix-cache-mib 0 instead of a per-run disk
directory. run-swift15-bf16.sh is untouched: it pins its own engines by design.
tests: the two budget-arithmetic seams asserted knobs that no longer exist and
are replaced by one seam that asserts the retired knobs are ABSENT from env and
argv - a stale line is a boot refusal, not a no-op. The container-contract seam
now asserts the tune mount and the absence of /data.
Frank
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