markstream-svelte – Design & UI skill for AI agents

Markstream Svelte

Overview

Integrate Markstream using Svelte 5 runes and SvelteKit-safe browser boundaries.

When to Use

Use for Svelte 5 or SvelteKit package setup, streaming state, workers, or scoped custom components. Svelte 4 is unsupported.

Workflow

Inspect the existing package manager, installed package version and project conventions. A requested scoped integration already authorizes routine source/dependency edits; seek approval only for a material scope expansion or unresolved beta/alpha adoption decision.

1. Confirm Svelte 5 and acceptance of a beta package.

2. Install only requested peers; import package CSS after resets and KaTeX CSS only for math.

3. Start with <MarkdownRender {content} /> and smooth streaming auto.

4. For live chat disable fade and opt into the cursor; on completion set final, disable pacing/cursor, and enable fade only if desired.

5. Use nodes only for worker-owned parsing or shared AST state.

6. Use $props() and callbacks. Configure KaTeX or Mermaid workers only when requested.

7. Prefer renderer-local customComponents; use scoped registration only when sharing is intentional.

8. Keep browser-only workers behind SvelteKit client boundaries; validate with svelte-check, build, or e2e.

Example

<script lang="ts">
  import MarkdownRender from 'markstream-svelte'
  import 'markstream-svelte/index.css'

  let { content, isDone }: { content: string; isDone: boolean } = $props()
</script>

<MarkdownRender
  {content}
  final={isDone}
  fade={isDone}
  typewriter={!isDone}
  smoothStreaming={isDone ? false : 'auto'}
  htmlPolicy="safe"
/>

Limitations

• Svelte 4 is unsupported and the package is beta.
• Workers and heavy peers require client-side bundler support.
• This skill does not migrate unrelated Svelte architecture.

Security & Safety Notes

Keep safe HTML and strict Mermaid defaults. Review dependencies and never run browser-only peers during SSR.

Verify props, export paths and peer ranges against the installed package, not a mutable upstream main. Test partial and completed streams, malformed/untrusted Markdown, links and image URLs, cancellation and reduced motion. Safe HTML and strict diagrams reduce exposure but do not alone enforce URL/network privacy or application component permissions.