{
  "slug": "vercel-multi-service-builds-support-experimental-concurrency-0f151fdf49bf",
  "title": "vercel multi-service builds support experimental concurrency",
  "tools": [
    "vercel"
  ],
  "tags": [
    "agent"
  ],
  "introduced_at": "2026-08-29T01:07:49.520Z",
  "announced_at": "2026-08-29T01:07:49.520Z",
  "effective_at": null,
  "date_basis": "source-publication",
  "status": "unknown",
  "how": {
    "incantation": "For a multi-service project, set `VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY` above `1` to run fork-eligible service builds concurrently; builds are grouped by install scope. The release note allows an integer, a percentage of available parallelism, or `auto`.",
    "examples": [
      "VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY=2 vercel build",
      "VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY=50% vercel build",
      "VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY=auto vercel build"
    ],
    "gotchas": [
      "Version: 59.10.0",
      "Availability: Experimental; concurrency values above 1 enable parallel builds.",
      "VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY: Concurrency setting: integer, percentage of available parallelism, or `auto`; default `1` preserves sequential behavior.",
      "The default of 1 preserves fully sequential behavior.",
      "Only fork-eligible service builds run concurrently.",
      "Builds are grouped by install scope so package-manager installs never race."
    ]
  },
  "why_it_matters": "Build a project with multiple services and control how many eligible service builds run concurrently.",
  "before": "Set `VERCEL_EXPERIMENTAL_BUILD_CONCURRENCY` to its default value of 1 for fully sequential service builds.",
  "sources": [
    "https://github.com/vercel/vercel/blob/main/packages/cli/CHANGELOG.md#59100"
  ],
  "rank": 0.94036,
  "judge": {
    "publish": true,
    "judge_model": "codex-cli/gpt-6-luna+typesafe/jev-1.13.0",
    "prompt_version": "extract-v7+enrich-v1+judge-v2x3+jev-publish-v1"
  },
  "review_state": "approved",
  "provenance": {
    "run_id": "vercel-20261007",
    "verdict_id": "vercel-20261007:vercel-20261007-f1f0e7760a844ceb-0:gate",
    "evidence_hash": "a6c217a2c431000edc1304efa8449d208f71049309610fc0abfe8686cef4943d"
  },
  "review": {
    "draft_hash": "c64048c18f59f9da34f53d993f0545579d7227293f670ffd7427244571d0b161",
    "reviewer": "publication-gate",
    "reviewed_at": "2026-10-07T00:00:00.000Z",
    "decision": "vercel-20261007: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)."
  }
}