{
  "id": 13140851,
  "title": "Why did this re-run?",
  "url": "https://urgent.news/2026/10/09/why-did-this-re-run",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-10-09T15:05:25.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/vzn-vx/why-did-this-re-run-28dp"
  },
  "original_language": "en",
  "account": "A cache key is an opaque hash that changes when its components alter. However, most tools do not retain information about which parts have changed, resulting in a manual bisecting process that consumes significant time. vx records per-component input fingerprints alongside cache entries, enabling a quick and precise answer through a terminal command. The tool compares the latest run with the one preceding it or a specific run, inspecting stored components such as files, environment variables, and runtime outputs. When an upstream dependency changes, only its key is recorded, leading to a cache key change. vx why can trace the chain of dependencies that moved in a single run to the task whose inputs changed, providing a clear cause for re-execution. The tool can be invoked after the fact, even on different machines, providing valuable insights into why a re-run occurred.",
  "summary": "A cache key is one opaque hash. When it changes, knowing that it changed is nearly useless. You need to know which of its parts moved. Most tools do not keep that information; they compute the hash, compare it, and print miss . The afternoon you then spend bisecting your own inputs is the real cost of the cache. vx records the per-component input fingerprint alongside every cache entry. That…",
  "key_points": [
    "Cache key changes when its components alter",
    "vx records per-component input fingerprints",
    "vx why traces dependency chain causing re-run"
  ],
  "editors_take": null,
  "illustration": null,
  "coverage": {
    "outlets": 1,
    "also_reported_by": []
  },
  "ai_generated": true,
  "disclaimer": "Summaries, key points and the editor’s take are written by software from other outlets’ reporting and may contain errors — always check the linked original."
}