system-design

Run the skill after producing a requirements document at docs/devdocs/01-requirements.md. It auto-detects initial versus incremental mode, asks about tech stack and platform preferences, then generates a layered design covering architecture, modules, interfaces, and data models.

Initial mode runs when no design document exists and builds the full L1-L4 layered design. Incremental mode runs when a design exists and new features or insights arrive, performing impact analysis, backward-compatibility assessment, and a revision checklist before updating the document.

No. The skill is strictly prohibited from producing implementation code. Interface sections contain only signatures and behavior contracts (preconditions, postconditions, error contracts); coding is delegated to the separate dev-workflow stage.

Only when a genuine fork exists, meaning two or more defensible approaches such as technology selection or architectural style. If the solution is self-evident, it produces the document directly without a confirmation gate, and self-check results go into the document rather than the dialog.

Realign mode backfills structural or field gaps in an existing design document after the design spec version is upgraded. It only patches differences against the new spec and never reruns the L1-L4 layered design interaction.