# `ExAthena.Modes.PlanAndSolve`
[🔗](https://github.com/udin-io/ex_athena/blob/v0.7.1/lib/ex_athena/modes/plan_and_solve.ex#L1)

Plan-and-Solve mode.

Two-phase operation: on the first iteration, the agent is asked to
**plan** before it acts. Subsequent iterations execute the plan using
`ExAthena.Modes.ReAct`'s standard cycle.

Rationale (Plan-and-Solve literature): models produce better
tool-calling behaviour when they articulate a plan before diving into
actions. Forcing the first turn to be planning-only prevents the
"immediate tool call" failure mode you see with small models on
complex prompts.

## State

Plan-mode state is kept in `state.mode_state[:phase]`:

  * `:planning` — on the first iteration. A planning-only system-prompt
    addendum is injected, forbidding tool calls.
  * `:executing` — subsequent iterations fall through to the ReAct
    cycle.

## Configuration

    ExAthena.run(prompt, mode: :plan_and_solve, …)

No extra options. The planning system prompt is hardcoded; consumers
who want a custom planning instruction should implement their own Mode
(the `ReAct` module is 200 lines of reference).

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*Consult [api-reference.md](api-reference.md) for complete listing*