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Playgrounds for systems internals.

Each lab turns a real behavior model into step-by-step state transitions.

Event Loop Visualizer

See how JavaScript schedules sync code, microtasks, and macrotasks.

Code Input

1. Run
→
2. Step / Auto Play
→
3. Reset
Start here: click Run first. Step and Auto Play unlock after Run.
Custom code runs in an isolated Web Worker with a timeout guard.

Call Stack

0
    Empty

    Web APIs

    0
      Empty

      Microtask Queue

      0
        Empty

        Task Queue

        0
          Empty

          Event Loop

          Next source
          Waiting

          Console Output

          No output yet.

          Current Explanation

          Select an example or paste code, then click Run to generate simulation steps.

          Timeline Log

          Run a simulation to see step history.
          Step progress: not started (click Run).
          Speed
          700 ms

          Skill Loading Visualizer

          How an agent picks a skill, implicitly from descriptions or explicitly from a typed name, and what each level costs in context.

          Input

          loaded:
          Run first, then Step or Auto Play.

          Context

          0 tok

          L1 · Metadata

          0
            empty

            L2 · Body

            0
              empty

              L3 · Bundled

              0
                empty

                Decision

                idle

                Idle

                Startup

                Pick an example or write a prompt, then Run.

                Candidates
                run to score
                Trace
                no steps yet
                Registry
                /pdf-processingPersonal
                none
                		50 / 1180
                /deployPersonal
                disable-model-invocationallowed-tools
                		12 / 640
                /deployProject
                none
                		17 / 520
                /legacy-billingProject
                user-invocable: false
                		58 / 2050
                /db-migrationsProject
                paths: db/** prisma/**
                		25 / 900
                /acme:changelogPlugin
                allowed-tools
                		36 / 760
                not started
                Speed
                900 ms

                More labs in progress

                The next set extends beyond scheduling and skill loading into transport-level request flows and React rendering semantics.

                Upcoming

                HTTP Lifecycle Playground

                Visualize DNS, TCP/TLS, request/response cycles, retries, caching, and latency segments in one flow.

                Upcoming

                React Rendering Visualizer

                Step through render/commit/effect phases with state updates and scheduling priorities.

                Upcoming

                Runtime Observability Sandbox

                Track logs, metrics, and traces for mini services to show how production debugging actually works.