Provenance & Tamper-Evidence

Every ClassificationResult carries a content_hash — SHA-256 of (text, context, taxonomy_version). It's deterministic: the same input under the same taxonomy version always hashes the same, regardless of when it's computed, so it can be used to verify "this exact text was classified under this exact taxonomy version" independent of any particular run.

For escalation tracking, each Observation is chained to the one before it — record_hash is a hash of the previous record's hash plus this record's fields, the same idea as a git commit chain or a minimal Merkle-style ledger. Altering any historical record (directly in the database, bypassing the API) changes its hash, which no longer matches what every later record's hash was computed from:

nhc track verify <source_id>

reports Chain intact: YES or, on a tampered history, NO — TAMPERING DETECTED plus the first broken observation id (also GET /tracking/{source_id}/verify).

Warning

This detects tampering; it does not prevent it — nothing stops someone with direct database access from recomputing the whole chain to hide their edit. For real accountability-workflow use, pair this with normal database access controls and backups, not as a substitute for them.