Advanced CodeAct (and Predict) Tuning

The authoring basics are in nooa-agent-authoring. This skill covers the deep configuration surface, verified against strategies/codeact.py, strategies/prefill.py, strategies/predict.py, and config/.

Config plumbing rules (read first)

• Strategy constructors take config= only: CodeActStrategy(config=CodeActConfig(...)), PredictStrategy(PredictConfig(...)). Flat kwargs (CodeActStrategy(max_iterations=10), CodeActStrategy(prefill=...)) do not exist, despite some docstring examples.
• All config objects are frozen Pydantic models with merge_with(other): only fields explicitly set on other override. Configs must be freshly constructed — anything round-tripped through model_dump()/model_validate() has an empty model_fields_set and merge_with raises.
• Truncation layers: framework default → Agent class kwarg truncation= → instance kwarg → @strategy(..., truncation=...) per method. TruncationConfig.merge_with deep-merges sub-configs field-by-field; the strategy configs merge flat.

Prefill

Before the first LLM turn, CodeAct runs up to two synthetic execute_python cells (tool-call id prefixed prefill_, execution_count=0). They cost no loop iterations, their failures are non-fatal (logged as an Error event), and any variables they define persist as live REPL locals for the model's first real turn.

1. The prefill plugin (default InspectInputsPrefill()): generates code that prints the call signature, pprint()s each parameter under truncation.prefill_format limits (defaults max_string=2000, max_length=25, max_depth=4), auto-show()s Media parameters for multimodal perception, and prints doc() of a complex return type. Per-parameter limits come from Annotated[T, spec(max_string=..., max_length=...)] on the signature.
2. Pre-ellipsis code: statements between the docstring and the ... are extracted from the AST and run verbatim as the second prefill cell — with or without the plugin.