sequenceDiagram
    participant Pool as Thread Pool
    participant Worker as Worker Thread
    participant Local as Local<T>
    participant Activity as WorkerActivity
    participant Metric as Prometheus Counter

    Pool->>Worker: Spawn worker thread
    Worker->>Local: Initialize with activity field
    Worker->>Local: on_worker_start()
    Local->>Activity: Record start time
    Activity->>Metric: Begin tracking (if enabled)

    loop For Each Task
        Worker->>Local: Execute task
        Local->>Activity: Monitor execution
        Worker->>Local: on_task_complete()
        Local->>Activity: Check elapsed time
        alt Periodic checkpoint triggered
            Activity->>Activity: Flush accumulated time
            Activity->>Metric: Update counter with active seconds
        end
    end

    Worker->>Local: Drain remaining futures
    Worker->>Local: on_worker_end()
    Local->>Activity: Final flush
    Activity->>Metric: Commit final active seconds
    Local->>Local: Clear activity state