---

name: markstream-svelte description: Integrate the beta markstream-svelte package in Svelte 5 or SvelteKit apps. Use when Codex needs Svelte 5 runes, CSS and optional peers, smooth streaming, worker setup, renderer-local or scoped custom components, or SSR-safe boundaries. Svelte 4 is unsupported.

Markstream Svelte

• Confirm Svelte 5; ask Svelte 4 users to upgrade.
• Add package and only requested peers.
• Import CSS after resets; KaTeX CSS for math.
• Treat the package as beta and confirm the app accepts that API maturity.
• Default to <MarkdownRender {content} />.
  • For streaming AI chat, keep content and use built-in smooth streaming first.
    • smoothStreaming="auto" is the default and activates when typewriter={true} or maxLiveNodes <= 0.
    • typewriter only controls the blinking cursor and defaults to false.
    • fade controls node enter and streamed-text fade animations and defaults to true.
  • Streaming vs recovering history: in chat UIs the same renderer starts streaming and later switches to history when final={true}.
    • Streaming: smoothStreaming="auto", fade={false}, typewriter={true}. This is a conservative visual/performance choice, not an API incompatibility. This adapter has not adopted Vue 3's bounded append fades, so verify its animation behavior before enabling both.
    • Recovering history: smoothStreaming={false}, fade={true}, typewriter={false}. Content is already complete — pacing would slow it down, but fade gives a polished entry animation.
    • Dynamic switch: smoothStreaming={isStreaming ? 'auto' : false}, fade={!isStreaming}.
  • Use nodes + final for worker-preparsed content, shared AST stores, or custom AST control.
• Use $props() and callbacks.
• Workers: setKaTeXWorker, setMermaidWorker, workers/*?worker.
• Custom UI: prefer the renderer-local customComponents prop for one surface; use scoped setCustomComponents, customId, and customHtmlTags when shared registration is intentional.
• Keep browser-only workers and heavy peers behind SvelteKit client boundaries.
• Verify with svelte-check, build, or e2e.

Useful Doc Targets

• docs/guide/svelte.md
• docs/frameworks/svelte.md