{
  "id": "durable-agent-jobs",
  "title": "Durable Agent Jobs",
  "level": 4,
  "levelName": "Systems",
  "tagline": "Persist job states and reject stale worker completions.",
  "summary": "Build a persistent local report queue with versioned leases, immutable input, idempotent output receipts and reproducible worker-process crash recovery.",
  "usefulFor": [
    "Resume local report jobs after a worker crash",
    "Observe and test the gap between an output effect and durable completion"
  ],
  "youWillBuild": "Build a persistent local report queue with versioned leases, immutable input, idempotent output receipts and reproducible worker-process crash recovery.",
  "hours": 8,
  "languages": ["Go"],
  "status": "ready",
  "source": "core",
  "author": {
    "name": "AI Engineering from Scratch",
    "github": "rohitg00"
  },
  "skills": [
    "Create jobs with stable identity",
    "Claim with a lease and version",
    "Finish or reclaim expired work",
    "Write and recover atomic snapshots"
  ],
  "prerequisites": [
    "Go 1.22 or later on Linux or macOS",
    "Python 3.10 or later for the grader",
    "Go structs, pointers, errors and JSON files",
    "Basic process lifecycle and filesystem operations"
  ],
  "inspiredBy": [],
  "demo": {
    "command": ["go", "run", ".", "demo"],
    "cwd": "solution"
  },
  "stages": [
    {
      "id": "01-create-jobs-with-stable-identity",
      "title": "Create jobs with stable identity",
      "summary": "Accept a bounded identifier and start every job in queued state with version zero.",
      "hours": 2,
      "language": "go",
      "difficulty": "starter",
      "concepts": [
        "Validate ID",
        "Initial state",
        "Zero version",
        "No side effect"
      ]
    },
    {
      "id": "02-claim-with-a-lease-and-version",
      "title": "Claim with a lease and version",
      "summary": "Only queued work can be claimed.",
      "hours": 2,
      "language": "go",
      "difficulty": "core",
      "concepts": [
        "Expected version",
        "Attempt cap",
        "Lease arithmetic",
        "Atomic state mutation"
      ]
    },
    {
      "id": "03-finish-or-reclaim-expired-work",
      "title": "Finish or reclaim expired work",
      "summary": "Finish succeeds only for the current running version before its lease expires.",
      "hours": 2,
      "language": "go",
      "difficulty": "core",
      "concepts": [
        "Lease boundary",
        "Requeue expired",
        "Increment version",
        "Fence stale worker"
      ]
    },
    {
      "id": "04-write-and-recover-atomic-snapshots",
      "title": "Write and recover atomic snapshots",
      "summary": "Compose validated snapshots with locked enqueue, durable claims and crash-safe local receipt reuse.",
      "hours": 2,
      "language": "go",
      "difficulty": "core",
      "concepts": [
        "Validate snapshot",
        "Write temp",
        "Flush and rename",
        "Recover records"
      ],
      "timeout": 120
    }
  ],
  "demos": [
    {
      "gif": "media/run.gif",
      "poster": "media/run.png",
      "title": "Initialize and grade",
      "caption": "Recorded starter failure followed by all reference-solution stages passing. Reference passes do not earn learner certificates."
    },
    {
      "gif": "media/output.gif",
      "poster": "media/output.png",
      "title": "Inspect the output",
      "caption": "Actual output from the local deterministic demo command. See the README for fixture and live-adapter limits."
    }
  ]
}