What is Planner-Executor?
Planner-Executor is an AI agent architecture that separates high-level task decomposition and strategy selection from concrete action execution, observation, and result reporting.
How It Works
Planner-Executor is useful when a task is complex enough that the agent should not immediately act on the first model response. The planner proposes a sequence of steps, dependencies, or success criteria. The executor performs those steps through tools, retrieval, code, or APIs and reports observations back. This separation can improve reviewability and reliability, but it is not automatically safe: plans can be wrong, executors can misinterpret steps, and both layers need evaluation and constraints.
Key Characteristics
- Role separation: splits strategy and decomposition from tool execution
- Plan visibility: makes intended steps easier to inspect before actions occur
- Iterative feedback: executor observations can cause replanning or escalation
- Tool-use discipline: reduces impulsive calls by making actions follow an explicit plan
- Failure modes: may suffer from vague plans, stale assumptions, or executor drift
Common Use Cases
- Breaking a software migration into analysis, edits, tests, and verification
- Planning a research workflow before issuing web or database queries
- Reviewing high-risk agent plans before allowing external side effects
- Coordinating multiple tool calls where dependencies matter
- Comparing planned steps against actual agent trajectory during evaluation
Example
Loading code...Frequently Asked Questions
Does Planner-Executor require two separate models?
No. Planner and executor can be separate agents, separate prompts, separate graph nodes, or even the same model used with different instructions and constraints.
Why separate planning from execution?
Separation makes intended actions visible before execution, allows review or approval, and gives teams a place to compare what the agent planned with what it actually did.
What can go wrong with Planner-Executor?
The planner may create unrealistic steps, omit constraints, or assume unavailable tools. The executor may follow a bad plan too literally or deviate without reporting.
How should this pattern be evaluated?
Evaluate both plan quality and execution quality: whether the plan is relevant and safe, whether execution follows it, and whether replanning happens when observations contradict assumptions.