Plan
Fast vs Deep specs
Choose planning depth based on the decisions you need to make.
Fast Spec gives a quicker project-level plan. Deep Spec develops a more detailed breakdown for complex work. Both can produce requirements, architecture, and specifications for humans and coding agents.
| Choose | When it helps |
|---|---|
| Fast Spec | Explore scope, validate an idea, or establish a first architecture |
| Deep Spec | Coordinate a larger project or examine implementation details and subtasks |
Deep output typically includes more granular stories and subtasks. Inspect the generated artifacts for the actual level of detail; do not rely on a fixed number of milestones or tasks.
Generation time and credits vary with scope. The Architect overview keeps current estimates in one place. Plans and credits explains commercial availability.
Refine the plan
Start with Fast when you need to assess direction, then request deeper planning for areas that need more detail. In the REST API, an existing spec’s text goes in currentContext; in MCP it goes in existingContext. Neither field is a spec ID or an automatic upgrade operation.
In the Coding Agent, planning happens when the agent decides a request needs it, and you can ask for a plan at any time. That is separate from spec depth and model choice.