A transparency log without split-view defense is just a signature with
extra steps: the provider could serve one tree to the agent and another
to the world, or roll the log back, and standalone receipt verification
would never notice. The primitives (RFC 9162 consistency proofs) were
already implemented and correct; this closes the loop on the AGENT side.
- src/pacta/sthstore.py: a local STH pin store. Unknown log -> pin
(trust-on-first-use, recorded as such). Same tree size -> the root
must match the pin byte-for-byte; a mismatch is named EQUIVOCATION
and is a hard rejection. Larger tree -> a consistency proof FROM THE
PINNED SIZE is required and verified before the pin advances
(receipts already embed a from-previous anchor; the anchor's root is
itself checked against the pin so a lying anchor cannot bridge a
split view). Smaller tree -> LOG ROLLBACK, hard rejection.
- Freshness policy: --max-sth-age-seconds rejects stale (or
future-dated) tree heads - an old-but-valid STH can hide later
entries.
- Wired into receipt-verify, claims, and agent (--sth-store,
--consistency-proof, --max-sth-age-seconds); evidence records the
pin action; any accountability failure fails the receipt closed.
- Provider: log-consistency --from-size N (serve proofs for pinning
agents whose pin is older than the receipt's embedded anchor) and
log-audit (monitor self-check: recompute the tree, verify the stored
STH and per-entry leaf hashes).
Live drill in this commit's validation: pin-on-first-use -> matched ->
grown-with-proof advance -> a real forged same-size split view REJECTED
with the equivocation diagnostic -> freshness rejection -> clean
self-audit. tests/test_sthstore.py covers pin/match/equivocation,
growth-without-proof, lying consistency anchors, rollback, freshness.
45/45 tests green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
The verified corpus completed its phase 2 on 2026-07-06: every ed25519
fork now carries FOUR button-enforced apex tiers up to the full lift
(accept <=> decompress(R) = [k](-A)+[s]B as points), the complete scalar
layer, and the constructive encoding/decoding chain. pacta was calibrated
to the pre-apex corpus and - worse - had no vocabulary for
boundary-audited certificates: its axiom audit knew only "clean = exactly
the three standard axioms", so the apex tiers would have scored dirty.
New vocabulary:
- Profile.certificate_axioms: per-certificate ALLOWED axiom sets;
expected_axioms_for(cert) resolves each certificate's own boundary.
- RepoConfig.apex_boundary: a simple per-fork key (dalek-wrappers /
hash3 / anza) expanded by the ed25519 profile into the exact
per-tier allowed sets. AUTHORITY NOTE in profiles/ed25519.py: each
repo's check.sh Phase 3b is the enforcement point; if the button and
this table disagree, the button wins.
- run_axiom_audit compares each certificate against ITS allowed set;
deviation in EITHER direction (extra axiom or missing boundary
axiom) is dirty.
New risk reality:
- R4 is now reachable: full four-tier apex + constructive chain +
scalar arithmetic, all proven with cones pinned to their documented
boundaries. R4 always carries explicit residual blockers (SHA-512
oracle, hypothesis-parametric wire parses, translation faithfulness,
no side-channel/build assurance - those gate R5).
- R3 unchanged (arithmetic pair) and now explains exactly which apex
certificates are missing for R4.
Attestation trust model hardened:
- The provider is trusted for its OBSERVATION, never its VERDICT:
axiom_status is re-derived locally from observed_axioms against the
agent's own boundary policy. A provider that labels a dirty cone
"clean" gains nothing; "proven" with no observed axioms is
"unverifiable".
- Partial attestations degrade instead of being rejected: uncovered
certificates stay unproven and the score caps accordingly (an
arithmetic-only attestation still authorizes an R3 library capsule,
never a wallet).
Also: scripts/mini_pytest.py - a dependency-free test runner (tmp_path,
raises, monkeypatch, capsys) for hosts without pytest; examples
regenerated FROM the tool (dalek/anza fixtures now R4, 16 certs; new
full four-tier attestation example); tests updated + new
tests/test_boundaries.py (lying-provider, missing-boundary-axiom,
partial-coverage cases). 40/40 tests green.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
