Storybook

• ALWAYS use mcp__storybook__get-storybook-story-instructions before writing stories.
• ALWAYS use mcp__storybook__preview-stories to preview stories after writing them.
• Stories use parameters.fixtures for fixture overrides.
• API mocking (handlers, fixtures, story-scoped overrides, msw-storybook-addon wiring and its v2→v3 break): svelte-5:msw skill.
• Storybook is usually already running: just navigate with Playwright MCP.
• Verify every story in the browser via Playwright MCP: don't assume it works.
• CSS imports: trace chains through BOTH App.svelte AND .storybook/preview.ts. Moving imports out of the SCSS chain breaks Storybook unless also added to preview.ts or storybook.scss.

Svelte 4 writable stores need wrapper components in stories

Components that import and read from Svelte 4 module-level writable() stores (from svelte/store) render with default/ empty data in Storybook unless the stores are populated before the component mounts. This does NOT apply to Svelte 5 runes- based state in .svelte.ts modules, those are reactive on their own.