{
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "$id": "structure-versions.schema.json",
  "title": "Structure Versions",
  "description": "Tracks versioned structural snapshots of .forge/ elements. Lives at .forge/structure-versions.json (NOT under .forge/store/). Composition model: Working Artifact = base@pluginVersion + snapshot@currentSnapshot + user_enhancements. Snapshot-array invariant: snapshots is ordered ascending by index; currentSnapshot always equals snapshots[snapshots.length - 1].index. Idempotency: manage-versions.cjs init is a no-op if the file already exists.",
  "type": "object",
  "required": ["basePackVersion", "overlayToolVersion", "currentSnapshot", "snapshots"],
  "additionalProperties": false,
  "properties": {
    "basePackVersion": {
      "type": "string",
      "description": "Plugin version at materialization time. Ties the snapshot set to a specific base-pack release."
    },
    "overlayToolVersion": {
      "type": "string",
      "description": "Version of project-overlay.schema.json at materialization time. Independent of structural drift; lets /forge:update detect runtime-contract drift."
    },
    "currentSnapshot": {
      "type": "integer",
      "minimum": 0,
      "description": "Index of the snapshot that produced the current .forge/ working set. Always equals snapshots[snapshots.length - 1].index."
    },
    "snapshots": {
      "type": "array",
      "description": "Ordered list of snapshots, ascending by index. Index 0 is always the base-pack snapshot.",
      "items": {
        "type": "object",
        "required": ["index", "createdAt", "source"],
        "additionalProperties": false,
        "properties": {
          "index": {
            "type": "integer",
            "minimum": 0
          },
          "createdAt": {
            "type": "string",
            "format": "date-time"
          },
          "source": {
            "type": "string",
            "description": "Origin of the snapshot: 'base-pack', 'post-init', 'post-sprint:SPRINT_ID', 'manual'"
          },
          "enhancedElements": {
            "type": "array",
            "items": { "type": "string" },
            "description": "Relative paths of .forge/ elements modified in this snapshot. Empty for snapshot 0.",
            "default": []
          },
          "archivePath": {
            "type": ["string", "null"],
            "description": "Path to the archive directory for this snapshot, e.g. .forge/archive/snap-1/. Null for snapshot 0 (nothing to archive before first enhancement)."
          }
        }
      }
    }
  }
}