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Agent Engineering Lab
The Bench · Playground

The Bench

Interactive experiments you can run in the browser. Read the Field Note, then come break it here.

Loop Lab

The companion to FN-004. A loop engineering agent that wants to "clean up" a database. Toggle the three external fences and watch the same agent either delete production or get stopped. The brake is not in the model; it is the layer you switch on here.

Loop Lab enforced
Agent scenario
External fences

Toggle the fences and run. With the gate off, the hallucinated-done agent deletes the database. With it on, the same agent cannot, by construction.

Deterministic, no API keys, same logic as the Python tests. Source: src/fn04.

Trace Replay

Pick a sample query and replay a real pre-recorded agent trace, token by token: tool calls, reasoning steps, and the final response. No live model calls.

Try the agent · pre-recorded sessions
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More on the Bench

Every Field Note and Lab Note with an interactive piece lands here. Next up: the eval-rubric failure-bucket explorer from FN-002, and the multi-agent versus router comparison from SG-003 and the Lab Note.