# Agent Harness

> A question-and-answer guide to designing the system around a language model.

- [Build an agent harness](https://agent-harness101.com/index.md): Understand the system around the model, one question at a time.
- [Learning path](https://agent-harness101.com/learning-path.md): Fourteen topics, from repository access to a complete agent architecture.
- [Repository access](https://agent-harness101.com/tools/repository-access.md): The model cannot inspect the repository.
- [Editing & execution](https://agent-harness101.com/tools/editing-and-execution.md): Reading explains the change; editing and execution prove it.
- [Context rot](https://agent-harness101.com/context/context-rot.md): Raw files and logs crowd out the goal and current reasoning.
- [Seven state stores](https://agent-harness101.com/context/state-stores.md): Seven stores, each holding one kind of state — reassembled per turn.
- [Why not one blob](https://agent-harness101.com/context/why-not-one-blob.md): Each format is chosen for how that state gets written, read, and trusted.
- [Token levers](https://agent-harness101.com/cost/token-levers.md): There are several levers. Model routing is one strategy.
- [Enforce with a hook](https://agent-harness101.com/cost/enforce-with-a-hook.md): A prompt-based instruction is a suggestion. A hook enforces it in code.
- [The delegation gate](https://agent-harness101.com/cost/the-delegation-gate.md): No. Delegation must buy isolation or useful parallelism.
- [Conditional planning](https://agent-harness101.com/planning/conditional-planning.md): Make planning conditional; persist only compact task state.
- [Subagent isolation](https://agent-harness101.com/subagents/subagent-isolation.md): Because exploration pollutes the context used to integrate the fix.
- [Write conflicts](https://agent-harness101.com/subagents/write-conflicts.md): Avoid the collision by design first. Isolate with worktrees when it can't be avoided.
- [When to delegate](https://agent-harness101.com/subagents/when-to-delegate.md): The decision depends on context and independence, not task size alone.
- [Recap](https://agent-harness101.com/synthesis/recap.md): Eight decisions, two kinds of pressure.
- [The architecture](https://agent-harness101.com/synthesis/the-architecture.md): Each component exists because the simpler design failed.
- [Sources & notes](https://agent-harness101.com/sources.md): Published figures, their origins, and the caveats that keep them honest.
- [Contributing](https://agent-harness101.com/contributing.md): Help improve the questions, explanations, diagrams, and evidence.


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