{
  "slug": "terragrunt-cas-mutable-attribute-for-editable-fetched-sources-d475f3198fa9",
  "title": "Terragrunt CAS `mutable` attribute for editable fetched sources",
  "tools": [
    "terragrunt"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-05-18T17:06:31.000Z",
  "announced_at": "2026-05-18T17:06:31.000Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "When a source is fetched through CAS and you need to edit its materialized files, set `mutable = true` in the applicable `terraform`, `unit`, or `stack` block. This copies files into the block’s working directory instead of hardlinking them from CAS.",
    "examples": [
      "terraform {\n  source  = \"git::https://github.com/acme/infrastructure-modules.git//vpc?ref=v1.0.0\"\n  mutable = true\n}"
    ],
    "gotchas": [
      "Version: v1.0.5",
      "mutable: Boolean on `terraform`, `unit`, or `stack`; `true` copies CAS-fetched files so they are editable. Defaults to `false`, which hardlinks files and marks them read-only.",
      "Prerequisite: The source must be fetched through CAS; `mutable` has no effect with the standard download path.",
      "The default is `false`; files are materialized read-only so an accidental edit cannot reach back into the shared CAS store.",
      "The attribute is orthogonal to `update_source_with_cas`.",
      "The attribute has no effect when content is fetched through the standard download path, which already produces an independent copy."
    ]
  },
  "why_it_matters": "When you need to edit source files materialized through CAS, configure the applicable block as mutable.",
  "sources": [
    "https://github.com/gruntwork-io/terragrunt/releases/tag/v1.0.5"
  ],
  "rank": 0.94033,
  "judge": {
    "publish": true,
    "judge_model": "codex-cli/gpt-6-luna+typesafe/jev-1.13.0",
    "prompt_version": "extract-v7+enrich-v2+judge-v2x3+jev-publish-v1"
  },
  "review_state": "approved",
  "provenance": {
    "run_id": "wave2a-20261017",
    "verdict_id": "wave2a-20261017:wave2a-20261017-dbb4231dfd6f8dce-4:gate",
    "evidence_hash": "76e8effac64656f91216971392d38eac5ef9a9617a90a95b10a210370c884e7a"
  },
  "review": {
    "draft_hash": "63ea532e1466c6ca38b70faa061f7afbabd814fb409424dcf1f16557fc8c619d",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-07T00:00:00.000Z",
    "decision": "wave2a-20261017:gate",
    "reason": "3 of 3 judge runs approved with p_yes >= 0.9 (mean 0.94 >= 0.9; 2 needed) and Jev gave 0.61 (>= 0.6 needed)."
  }
}