{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://mhs.openai4s.org/schema/0.9/snapshot.schema.json",
  "title": "OpenMHS snapshot",
  "description": "Result of mhs.snapshot (MHS-002 9.1). Only simulated/hybrid devices with fidelity.snapshot_restore=true and replay devices may produce one. Canonical wire field: `state` (the {resource_id: state} document). `snapshot` is the retained backward-compatible alias for the same document; a snapshot MUST carry at least one of the two, and endpoints SHOULD emit both with identical content. `snapshot_digest` is the canonical digest of the state document. Restoring a snapshot MUST reproduce `revision` and `state_hash`; `device_id`, `instance_id`, `mode` and `fidelity_digest` are mandatory identity/fidelity metadata, and a snapshot from another device/instance/fidelity configuration MUST be rejected (PROTO-035/FID-004).",
  "type": "object",
  "required": [
    "device_id",
    "instance_id",
    "mode",
    "revision",
    "state_hash",
    "snapshot_digest",
    "fidelity_digest"
  ],
  "anyOf": [
    { "required": ["state"] },
    { "required": ["snapshot"] }
  ],
  "additionalProperties": false,
  "properties": {
    "device_id": {
      "$ref": "defs.schema.json#/$defs/deviceId"
    },
    "instance_id": {
      "$ref": "defs.schema.json#/$defs/ulid",
      "description": "ULID of the device instance (the same identity that devices.get and restore compare against)."
    },
    "mode": {
      "$ref": "defs.schema.json#/$defs/mode"
    },
    "revision": {
      "$ref": "defs.schema.json#/$defs/revisionValue"
    },
    "state_hash": {
      "$ref": "defs.schema.json#/$defs/digest"
    },
    "state": {
      "type": "object",
      "description": "Canonical state document: {resource_id: resource state}, exactly as served by mhs.resource.read and bound by state_hash under the device's hash_exclusions."
    },
    "snapshot": {
      "type": "object",
      "description": "Backward-compatible alias of `state`; when both are present they MUST be identical."
    },
    "snapshot_digest": {
      "$ref": "defs.schema.json#/$defs/digest",
      "description": "canonical.digest(state document)."
    },
    "fidelity_digest": {
      "$ref": "defs.schema.json#/$defs/digest",
      "description": "Digest of the serving device's declared fidelity configuration; a snapshot from another fidelity instance MUST be rejected (FID-004)."
    },
    "created_at": {
      "$ref": "defs.schema.json#/$defs/rfc3339"
    }
  }
}