The single explicit, fail-closed f64→f32 down-cast at the certified lifecycle
egress. serving_cast(psi_steady, certificate, verdict) -> ServingState in
core/physics/cognitive_lifecycle.py:
- Casts ONLY a state that validates as a finite 32-vector, matches its
certificate psi_digest, and was verdict.admitted — an uncertified, refused, or
digest-mismatched state is never served.
- Precision-checks the f32 result (cast_error = max|f64-f32|, unit norm) and
fails closed on an f32 precision cliff (f32_precision_insufficient) rather than
serving a silently-degraded state.
- Keeps f64 as the source of truth: psi_steady and the psi_digest content-address
chain are untouched; ServingState carries provenance back (source_psi_digest,
certificate_id, measured cast_error) for audit. f64 stays inside
relaxation/eigendecomp — this is the one place f32 appears (ADR-0245 §2.2
mechanical sympathy).
Satisfies both ADR-0244 §2.5 and ADR-0245 §2.2 (one contract, two ADRs). Measured
on a real certified outcome: cast_error ~1.2e-8, unit_norm_f32 ~0.99999998.
Off-serving (A-04 guard: chat.runtime never imports it). ADR-0245 status map +
plan doc updated.
[Verification]: smoke 176 passed; fast lane 11907 passed / 109 skipped (-n auto,
not quarantine/slow); 10 targeted serving-cast tests passed.
918aa843b1