Customize agent components

Replace shipped prompts, policies, libraries, or complete agent loops when the shipped behavior no longer fits.

Most applications select shipped libraries and do not copy their source:

{
  "workflow": {
    "components": [
      {"id": "app.agent", "path": "agent.clj", "dependencies": ["agent.core"]},
      {"library": "agent.core"}
    ],
    "entry": "app.agent/run"
  }
}

The shipped agent.core loop is a replaceable library, not Kernel behavior. Start with it, then introduce a custom component under a new ID when the application needs different prompts, feedback, retry policy, continuation, or completion rules.

Trial a replacement safely

Selecting agent.core also selects its agent.prompt dependency. A verified component override can trial another prompt for one invocation without changing ptc.json. The active bundle remains immutable throughout the run; a later invocation compiles and checks the candidate before it can become active.

The standalone executable can run a prepared override descriptor but does not create one. Candidate creation is currently a source-checkout workflow. Use Evaluate changes with replay to compare a prepared candidate, and use the repository's embedding guide when creating the descriptor.

Each component declares its direct namespace dependencies. Selecting a library installs its immutable dependency closure, but does not add tools. Mission tools still come only from providers installed in ptc-host.json and selected for that mission in ptc.json.

Keep reusable components narrow:

• expose a small documented public surface;
• declare signatures where model-written calls benefit from validation;
• keep prompt-visible helpers focused on the task contract;
• separate workflow policy from mission-only task functions; and
• use a new component ID for a permanently customized prompt or loop.

Use the components-and-preludes reference for namespaces, dependency rules, visibility, signatures, shipped library selection, compilation, and provider-selection boundaries. The agent library reference documents the exact shipped loop entries and options.