A2 of the refined sequencing. Proves (deterministically, not by assertion) what a
long-running CORE life costs to persist per turn on a constrained offline device.
Measures the Shape B+ checkpoint BYTES per turn (session_state.json) over the real
turn loop — bytes, not wall-clock latency (machine-dependent → flaky). Reuses the L10
continuity corpus.
Measured cliff: save_session_state re-serializes the FULL snapshot every turn, so
per-turn bytes are O(n) in the accumulated life — 3,811 → 88,189 bytes (23x) over 24
turns, ~1.3KB/vault-entry re-written every turn. That blocks continuous-life at the edge.
The gate encodes the edge REQUIREMENT (≤16 KiB/turn regardless of session length) as
xfail(strict): it fails today (documenting the cliff), runs green in CI, and flips to
a hard failure the moment incremental/append-only persistence (O(Δ)/turn) lands —
forcing us to retire it. Plus a regression ceiling (passes today) and a determinism
check (the byte metric is reproducible → a valid gate).
The fix is algorithmic (incremental persistence, Python/Ring-2), NOT a language
rewrite. Tagged core/array_codec.py as the locked reference contract for a future
gated Ring-1 Zig byte-exact codec (ADR-0196 G0-G8) — step 3, only after the O(Δ) fix
and only if this gate proves the codec is still the bottleneck. See contract.md.
Foundation for L10 resume-as-same-life persistence. Adds:
- core/array_codec.py: a leaf (numpy+base64) codec encoding arrays as
{dtype, shape, b64(raw bytes)} — BIT-EXACT, never decimal. Float round-trips
lose zero precision, so a restored versor keeps versor_condition < 1e-6 and a
replayed turn keeps its trace_hash. dtype carries byte order; float32 is never
conflated with float64.
- field/state.py: FieldState.to_dict/from_dict. Multivector arrays (F, holonomy)
go through the byte codec; energy/valence round-trip exactly via JSON-safe
helpers (lazy physics imports keep field/ cycle-free).
Exit gate (the scope's #1 risk, de-risked first): bit-exact round-trip AND
closure preserved — versor_condition(restored.F) == versor_condition(fs.F)
exactly. 10 codec/FieldState tests + 55 architectural-invariant/runtime tests
pass. Purely additive; no existing behavior changed.
Part of docs/analysis/L10-shapeBplus-persistence-scope-2026-06-05.md (Phase A).
