Instruct seal format (Markdown)

Format for the agent instruction file integrity seal: what was sealed is what agents still read.

Seal field

YAML front matter:

---
hashseal: "blake3:<hex>"
hashseal_sig: |
  -----BEGIN PGP SIGNATURE-----
  …
  -----END PGP SIGNATURE-----
---

Signature is optional; see signing.

Chicken-and-egg

The digest is computed over canonical content with seal and signature fields excluded (hashseal, hashseal_sig, hashseal_key_id). Updating the seal/sig does not change the hashed payload.

YAML order when both present: hashseal then hashseal_sig (armor).

Canonical modes

Mode	Hash input
`full` (default)	Sorted front-matter keys (minus seal fields) as `key: value\n` lines, then `\n`, then LF-normalized body. If no non-seal FM keys, body only.
`body-only`	LF-normalized body only

CLI

hashseal seal --instruct
hashseal check
hashseal check --no-fail
hashseal unseal --instruct

Verify UX

Failures list every path with MISMATCH / MISSING_SEAL / … and expected vs actual digests.

Vectors

Official cases: verify/vectors/instruct-v1.json (FULL canonical mode). All language SDKs and core tests must agree.

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