{
  "id": 8426434,
  "title": "Leave a Replay Script, Not a Transcript",
  "url": "https://urgent.news/2026/09/19/leave-a-replay-script-not-a-transcript",
  "topic": "tech",
  "section": "Tech",
  "published": "2026-09-19T09:20:11.000Z",
  "source": {
    "name": "Dev.to",
    "slug": "dev-to",
    "url": "https://dev.to/applab_743/leave-a-replay-script-not-a-transcript-58ap"
  },
  "original_language": "en",
  "account": "A backend engineer submitted a pull request after an afternoon of coding. The ticket stated the pagination bug was resolved, tests were passing, and cache keys no longer collided. However, reviewers encountered a build failure even before the first test began. This failure highlights a crucial issue: chat transcripts are not reliable evidence of an agent's work. Teams that rely on them often find the work only exists within the original session. To combat this, a spike can be conducted using a replay script that the agent must leave behind. The hypothesis for the spike is defined before any prompts are sent. Given a frozen git worktree, failing characterization test, and a 90-minute time limit, the agent must generate a replay script. If the script cannot be reproduced on another machine without the agent, the spike is abandoned. Think of the replay script as a black-box recorder, capturing the agent's actions rather than its understanding. The goal is to have a script that can be executed on any machine, proving that the work existed independently of the agent's memory. The proposed layout includes a disposable directory with a hypothesis file, failing test, patch, and replay script. The hypothesis file contains a short statement that can be verified by a shell script. The clock file sets a time limit for the spike. The characterization test should fail on the main branch, as a spike that creates both the bug and the fix is not genuine. Before the agent starts, the operator clones a clean worktree and records the source tree's fingerprint. If the replay script runs successfully on a second host without relying on the original chat directory or agent artifacts, the spike passes and can be considered evidence of the agent's work.",
  "summary": "A backend engineer opened a pull request at sixteen forty after an afternoon spent steering a coding agent. The ticket claimed the pagination bug was gone, the tests were green, and the cache key no longer collided under concurrent load. Reviewers cloned the branch onto a laptop that had never seen the chat and watched the build fail before the first test even started. The session had felt like…",
  "key_points": [
    "Replay script captures agent's actions, not understanding",
    "Replay script must be reproducible on any machine",
    "Spike passes if script runs successfully without original chat directory"
  ],
  "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."
}