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Free module

Harness engineering

Learn agent harness engineering hands on: context budgets, tool design, permission modes, subagents, undo and a small harness.

6 lessons385 min lessonSoftware engineering

The lessons

Each lesson is free to read in full. Create a free account to run its commands in a live lab and to sit its quizzes and tasks.

  1. 1 · Container lab

    Context engineering for LLM agents

    I can choose what goes into an agent's context window under a token budget.

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  2. 2 · Container lab

    How to design tools for LLM agents

    I can write a tool a model uses correctly, with a clear name, a stated limit and a helpful error.

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  3. 3 · Container lab

    Permission modes for coding agents

    I can say which actions an agent may take without asking in plan, ask and auto modes.

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  4. 4 · Container lab

    Subagents and context isolation

    I can give a side task its own window and take back only a short answer.

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  5. 5 · Container lab

    Checkpoints and undo for coding agents

    I can record every change a run makes, so that I can rewind the files to any step.

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  6. 6 · Container lab

    Build a small coding agent harness

    I can put context, tools, modes, isolation and undo into one harness that I can run and rewind.

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Worked in a real lab

Every lesson of this module is worked in a lab started for you alone. The labs it uses:

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