{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "https://thinkloom.app/schemas/provenance/1.0/chain-head.schema.json",
  "title": "Chain head",
  "description": "Durable pointer to the last committed provenance event.",
  "type": "object",
  "properties": {
    "schema_version": {
      "const": "1.0"
    },
    "project_id": {
      "type": "string",
      "pattern": "^project_[0-9A-HJKMNP-TV-Z]{26}$"
    },
    "active_segment_number": {
      "type": "integer",
      "minimum": 1
    },
    "event_id": {
      "type": "string",
      "pattern": "^event_[0-9A-HJKMNP-TV-Z]{26}$"
    },
    "event_sequence": {
      "type": "integer",
      "minimum": 1
    },
    "event_hash": {
      "type": "string",
      "pattern": "^sha256:[a-f0-9]{64}$"
    },
    "updated_at": {
      "type": "string",
      "format": "date-time",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}:\\d{2}\\.\\d{3}Z$"
    }
  },
  "required": [
    "schema_version",
    "project_id",
    "active_segment_number",
    "event_id",
    "event_sequence",
    "event_hash",
    "updated_at"
  ],
  "additionalProperties": false,
  "examples": [
    {
      "schema_version": "1.0",
      "project_id": "project_01J00000000000000000000001",
      "active_segment_number": 1,
      "event_id": "event_01J00000000000000000000003",
      "event_sequence": 1,
      "event_hash": "sha256:4444444444444444444444444444444444444444444444444444444444444444",
      "updated_at": "2026-07-17T18:42:10.123Z"
    }
  ]
}