# Policy Hash and Versioning Spec (v1)

## Purpose

Ensure each quote, purchase, and entitlement is provably bound to an exact policy snapshot.

## Canonical Policy Snapshot

1. Serialize policy object with stable key ordering.
2. Normalize numeric representations.
3. Remove non-policy metadata fields.

## Hashing

1. Compute `policy_hash = SHA-256(canonical_policy_json)`.
2. Store hex-encoded 64-char hash.
3. Include `policy_hash` in quote response, receipt, and entitlement record.

## Versioning

1. `policy_version` is semantic (`v1`, `v1.1`, etc.) for human readability.
2. `policy_hash` is authoritative for machine verification.
3. Breaking changes require new `policy_version` and migration note.

## Enforcement

1. Checkout confirm rejects if tx-linked quote policy hash differs from current quote policy hash.
2. Entitlement activation uses stored `policy_hash`; no retroactive mutation.
3. Historical purchases remain tied to their original policy hash.