Re-applies the desired shape incrementally on the proven-good fp8 3x262144
base, after bisecting why the first attempt (30904ba) crash-looped.
Root cause: `--max-num-seqs 2` cannot compile on this model. AOT
build_guards(strict_error=True) inside profile_run -> _dummy_run specializes
`query_start_loc`'s width to SEQS + 1 (3 at SEQS 2, 4 at SEQS 3) and the
ConstraintViolationError kills engine init ~7 min in. MNBT is orthogonal:
SEQS 2 failed at MNBT 1024 AND 2048; SEQS 3 passed at both. KV dtype was a
red herring. Measured by four single-variable boot probes.
Arena lever measured: the expert arena is sized from `max_model_len` via the
registry-priced KV reserve (9190 B/token x max_model_len), NOT from
--kv-cache-memory-bytes. 262144 -> 14.30 GiB / 6,248 slots; 200704 ->
14.87 GiB / 6,496 slots. The 6.1e9 -> 3.15e9 pool cut bought zero arena and
is a runtime-headroom lever.
Shape: MAXLEN 200704, SEQS 3 (unchanged - the only slot count that compiles),
KV_BYTES 3.15e9/rank = 2.04x full-length concurrency at 7,701 B/token fp8,
MNBT 1024, gather 32x64, no spec decode, no prefetch, no precise-memory.
Frank
c769ff2f63