{
  "slug": "git-build-contexts-accept-mtime-commit-9ceb2f6c551f",
  "title": "Git build contexts accept mtime=commit",
  "tools": [
    "buildkit"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-03-31T12:57:33.000Z",
  "announced_at": "2026-03-31T12:57:33.000Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "For a remote build with a Git context, add `mtime=commit` to the Git URL query to set snapshot file, symlink, and directory mtimes to the resolved commit timestamp. If the Dockerfile frontend receives `SOURCE_DATE_EPOCH`, commit-time mtimes are selected automatically; the URL parameter can override the policy.",
    "examples": [
      "docker buildx build 'https://github.com/<owner>/<repo>.git?mtime=commit'"
    ],
    "gotchas": [
      "Version: dockerfile/1.23.0",
      "mtime: Git URL query parameter; `commit` selects resolved-commit mtimes. The documented alternatives are `commit` and `checkout`; the URL parameter can override the automatic policy.",
      "SOURCE_DATE_EPOCH: When set in the Dockerfile frontend, Git contexts automatically use commit-time mtimes. The docs do not specify a required value for this behavior.",
      "The automatic default applies to remote builds using a Git context that define `SOURCE_DATE_EPOCH`."
    ]
  },
  "why_it_matters": "Make a remote build using a Git context reproducible by setting checked-out file timestamps to the commit time.",
  "sources": [
    "https://github.com/moby/buildkit/releases/tag/dockerfile/1.23.0",
    "https://github.com/moby/buildkit/pull/6600"
  ],
  "rank": 0.93031,
  "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": "wave1b-20261016",
    "verdict_id": "wave1b-20261016:wave1b-20261016-ce694119607f9cbd-0:gate",
    "evidence_hash": "af059e19829900ce1d672a588d2f4d4bc98c035d9028e6aa6826d8582c91ea0b"
  },
  "review": {
    "draft_hash": "39923430c770b86fc7c558178fa40b2688985c5daef8366eedefa8fa28341165",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-07T00:00:00.000Z",
    "decision": "wave1b-20261016:gate",
    "reason": "2 of 3 judge runs approved with p_yes >= 0.9 (mean 0.93 >= 0.9; 2 needed) and Jev gave 0.64 (>= 0.6 needed)."
  }
}