Planner-Executor-Replanner (PER)

What Problem It Solves

Plans can become wrong mid-run. PER introduces a replanner that decides:

• continue
• replan
• finish (final)

Core Flow

flowchart TD
  U["Task"] --> P["Planner: plan"]
  P --> X["Executor: do step"]
  X --> R["Replanner: decide"]
  R -->|continue| X
  R -->|replan| P
  R -->|final| O["Final"]

Evolution Path

• Extends: Plan & Solve with explicit “plan may change”
• Often combined with: Retrieval (new evidence triggers replans)

Repo Reference

• Code: src/agent_patterns_lab/patterns/planner_executor_replanner.py
• Example: examples/51_planner_executor_replanner.py
• Tests: tests/test_per.py