Plan-Execute Control Flow
A plan that cannot survive a failure is a script. A script that can replan is an agent. Build the replanner first. Represent a plan as an ordered list of typed steps so the executor can reason about progress and outcome. Execute steps sequentially with a controlled failure handoff back to the planner. Replan from the current cursor with the prior error in the context so the next plan is informed. Emit a plan diff on each revision so a downstream tracer or UI can show why the plan changed. Enforce two budgets: a hard step ceiling and a hard replan ceiling. A chain-of-thought agent emits tokens and lets the loop guess where the tool call ends. A plan-and-execute agent emits a structured plan first, then executes each step deterministically. The plan is data the harness can introspect. The execution is the harness running that data through a dispatcher. Two pieces. A planner that produces a plan. An executor that runs the plan. The interesting work is what happens when the executor hits a failure. Three options: Replan is the one that turns a script into an agent. expectedoutcome is a short sentence the planner emits alongside the step. It is not enforced by the executor. It is for two things: the replanner reads it when revising the plan; the…
Plan-Execute Control Flow: A plan that cannot survive a failure is a script. A script that can replan is an agent. Build the replanner first.
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