Completes the verification chain (P1.2 -> P1.1 -> P1.3 -> P1.6). The client
remembers the last accepted (seq_no, event_hash) per stream and checks every
new receipt links forward; if the server rewinds a sequence number or presents
a divergent lineage, log_event / log_events raise AttestoForkDetected (Go:
*ForkDetectedError) and the stored head is NOT advanced. The customer's own
machine becomes the fork detector — no trust in any Attesto-side check.
- Python: HeadStore protocol + FileHeadStore (~/.attesto/heads.json, atomic,
0600, default) + MemoryHeadStore; wired into sync and async v2 clients;
head_store=None disables.
- TypeScript: HeadStore + MemoryHeadStore (default, edge-safe); Node-only
FileHeadStore kept in a separate module (@attesto/sdk/heads-file) so the core
bundle imports no node:fs; headStore: null disables.
- Go: HeadStore interface + MemoryHeadStore (default) + NewFileHeadStore;
WithHeadStore option; WithHeadStore(nil) disables.
Same forward/rewind/divergence/gap semantics across all three (unit-tested:
in-order advance, forged-rewind fork, divergent-next fork, forward-gap accept,
file-store restart persistence). Existing v2 client tests pin head_store=None
(they replay overlapping seq). READMEs gain a "Your SDK is a witness" section.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Adds payload_commitment / metadata_commitment / verify_payload_commitment
and assert_commitment_safe_numbers to the Python, TypeScript, and Go SDKs,
each building on the frozen canonical_json/domain_hash primitives (no change
to their byte output). The number preflight is a byte-for-byte port of the
backend assert_commitment_safe_numbers (floats rejected, |int| > 2^53-1
rejected, bool exempt) and is wired into the v2 log_event / log_events send
path, raising a typed AttestoUnsafeNumberError with the JSON path so the rule
fails at dev time rather than as a production 422; preflight=False /
SkipPreflight defers to the server.
New shared corpus golden-vectors/sdk-parity/canonical-numbers.json (15 accept
+ 8 reject), accept-hashes generated from the backend _commitment. Proven:
Python = TypeScript = Go = backend produce byte-identical commitment hashes
for every accept vector and identical reject paths (the Go float64-vs-Python-
int serialization parity holds). READMEs updated per SDK.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
