Planner–executor

How it works

A planner agent owns the objective (“rebalance the portfolio for the coming week”) and produces an explicit plan: which data to gather, which analyses to run, which orders to draft. Each step is executed by a worker — a smaller model, a single-purpose agent, or a deterministic tool — and results flow back to the planner, which revises the plan or hands the outcome to a verifier before anything reaches the market.

The separation matters because planning and execution fail differently: planning errors are reasoning errors, execution errors are integration errors. Isolating them makes both debuggable.

Design choices

• Plan as artifact. Persist the plan as structured data (steps, dependencies, status). It becomes the audit trail regulators-of-your-own-money want anyway.
• Executor capability boundaries. Workers get the narrowest tool access that does the job — the researcher can read market data but cannot place orders.
• Verification gate. A final check (rule-based or agentic) between the plan’s output and order submission is where risk controls naturally live.

Failure modes

• The planner micro-manages: plans so detailed that workers add nothing, doubling cost for no benefit.
• Stale plans: markets move while a long plan executes; plans need revision triggers, not just linear execution.
• Verifier rubber-stamping — if the verifier is the same model with the same context, it tends to approve its own reasoning.