Opus review of the symm prefetch wiring found a latent group deadlock:
the prefetch hit path never touched _agreed_tai_ipc_peer_ptrs, so the
first use of a layer's pool tensor — which issues a capability MIN
all-reduce plus an IPC handle all-gather — only happened on the sync
fallback. With every rank hitting from batch one (the prefetcher runs
a layer ahead), a later lone-rank miss would be the only rank issuing
those collectives. Both consumes now seed the (idempotent, per-pool-
tensor-cached) agreement at entry, before any per-rank early return;
the index consume gets the pool buffer from its indexer call site.
Unreachable in today's config (prefetch env off) but a blocker for
ever enabling it.
Also per review: the [pool|staging] combined pointer-table cache now
keys per pool table instead of holding one — the token and index pool
tables alternate every layer and evicted each other, so the cache
never hit; and a debug-gated check that current locs all map into the
staging page inverse (index_copy_ has no skip semantics for stray -1).
Validated on g0033: 151 unit tests; all four 8-rank byte-exactness
phases.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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