Brainstorming Ideas Into Approved Plans

Turn rough ideas into an approved implementation plan. Spark is a planning skill, not an execution skill: it clarifies intent, records assumptions, uses the active planning surface correctly, and stops for user approval.

Writable/default output is a Markdown plan at <project-root>/.plannings/YYYY-MM-DD-<feature-slug>.md. Native Plan modes are read-only while active. Create an HTML or visual artifact only when the user explicitly asks for HTML, browser-viewable, visual, mockup, or comparable output and the current surface allows file writes.

Planning Surface Selection

Choose the planning surface before deriving an output path. Do not force-enter Codex Plan mode just to run Spark; the user controls Codex native Plan mode with the client UI such as /plan or its mode toggle. Claude Code Plan mode may expose explicit plan-mode tools; use those only in the Claude Code branch.