Round 11 put the nesting count in the expander, which is optional. A
consumer at a lower priority can CLAIM and stop the chain before the
expander runs, while that fan-out's deferred-expansion subscriber still
runs — so the nested pass went uncounted, looked like the outermost
one, expanded early, and outer pairing resumed with a record the
replace had invalidated. `\alp(` gave `α(` again.
The count now comes from a no-op consumer registered at the minimum
priority, which runs first in every chain invocation that reaches any
consumer at all. Its guarantee is exactly the ordering contract the
chain already rests on, and it degrades safely: the only thing that can
skip it is a claim ahead of it, which skips the expander too, so
nothing is queued in that fan-out either.
The other plausible home does not work and the comment now says why: a
subscriber registered beside `run_deferred` is too late, because the
whole nested fan-out completes inside the OUTER chain's subscriber,
before either of them runs.
Acceptance 45o pins the short-circuit path — a consumer at 25 that
claims when the record is nil, so the nested pass never reaches the
expander. 45n passes against this bug, which is why both exist.
Counting in the expander fails 45o and nothing else.
Framing rev 12 also names the shape rounds 10–12 share: each fix was
correct about the failure it was shown and wrong about the boundary of
the mechanism it leaned on — the chain's copy semantics, then its
re-entrancy, then its short-circuit. A queue that outlives the thing
that filled it has to name that thing, not approximate it.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_011LFvC4FQtux4y32KuevZ7B
Levi Neuwirth
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