Planner Spec Expand

A one-line brief ("build a claude.ai clone", "a habit tracker with streaks") is not enough surface for a coding agent to make good decisions from. It has no design language, no acceptance criteria, no ordering. The generator ends up inventing scope mid-session and shipping incoherent slices.

The planner's job is to expand the brief into a spec dense enough that every downstream decision — what feature to pick, what "done" looks like, what the button should say — has an answer already written down. See Prithvi's post on planner/generator/evaluator separation for the underlying architecture: https://www.prithvirajrk.com/blog/three-agent-harness.

When to apply

• The user handed you a brief under ~200 words and expects a real product.
• You're about to seed [[feature-list-json]] and the brief has no orderable features yet.
• Scope drifted mid-project and the original spec no longer describes the target — rewrite, don't patch.

Procedure — expand in this order

Do the sections in order. Later sections depend on earlier ones being locked.