AM-4: measured what each remediation option actually buys, rather than
leaving one recommendation unquantified. serde_yaml optional removes 6
crates, not 5 — ryu belongs to that group, since serde_json now uses
zmij for floats. Full ladder: -6 to 27, serde_json -4 more to 23,
inlining SHA-256 -8 to 19, inlining ChaCha12 -4 to 15. Only
reimplementing a primitive gets under 20, so the target is unreachable
without undoing K5/K7.
Also records that crate count compares badly across ecosystems, and
offers the alternative the count is a proxy for: 307,317 lines of
third-party source under audit against 3,398 of our own.
AM-12: corrected from "uncomputable" to measured. The refusal to
estimate was right; the claim that no instrument existed was wrong.
Session transcripts carry exact per-message usage including the cache
breakdown. This session cost $248.46 at Fable 5 rates, of which 53% is
cache reads — cost is driven by context size times turn count, not by
output volume. What is still missing is per-task attribution, since
nothing marks task boundaries in a transcript.
CB-WP-0002 makes cost measurable and attributable: survey the
instruments, decide the attribution model by ADR, spec metrics that
include cost composition rather than a bare total, build a collector
whose positive control refuses to emit unreconciled numbers, and prove
it by answering a question that could not be answered before.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
