markstream-migration

name	markstream-migration
description	Audit and migrate existing Markdown rendering to Markstream. Use when Codex needs to replace another renderer, classify direct vs custom vs plugin-heavy usage, preserve behavior during adoption, migrate custom renderers into scoped Markstream overrides, or decide when `nodes` streaming is worth adopting.

Markstream Migration

Use this skill when a repo already renders Markdown and the task is to adopt Markstream safely.

Read references/adoption-checklist.md before changing code.

Workflow

1. Audit the repo's current renderer usage.
   • Search for markdown renderers, plugin chains, raw HTML handling, security props, and custom renderers.
   • List every call site that will be touched.
2. Classify the migration.
   • direct: simple string-in renderer swap.
   • renderer-custom: custom renderers but limited parser work.
   • plugin-heavy: remark, rehype, markdown-it, or other transform-heavy pipelines.
   • security-heavy: allow or deny lists, URL rewriting, sanitization, or raw HTML policies.
3. Swap the renderer first.
   • Introduce the correct Markstream package and CSS.
   • Import Markstream CSS through the package CSS subpath; do not rely on the renderer import to inject styles.
   • Preserve user-visible behavior before adding richer Markstream-only features.
   • Audit whether the old renderer allowed broad raw HTML or Mermaid loose-mode HTML labels before claiming parity.
4. Migrate custom renderers.
   • Convert built-in node renderers into scoped node-type overrides.
   • In React, prefer renderer-local streamingComponents for parser-backed tags and htmlComponents for sanitized HTML-prop components; use setCustomComponents for built-in node overrides or shared compatibility registration.
   • In Svelte or Angular, prefer the renderer-local customComponents input when the mapping does not need shared registration.
   • For trusted tag-like content, prefer customHtmlTags.
   • Use parseOptions.preTransformTokens, postTransformTokens, or postTransformNodes only when the old pipeline truly requires token or AST transforms.
5. Review gaps honestly.
   • Do not claim 1:1 parity where none exists.
   • Call out parser, plugin, security, or HTML behavior that still needs manual review.
6. Consider renderer mode and smooth streaming before jumping to nodes.
   • For Vue 3, choose mode="chat" for AI/SSE output, mode="docs" for rich document surfaces, and mode="minimal" for lightweight non-chat surfaces.
   • If the app streams content and only needs pacing, smooth-streaming="auto" (the default) handles it without requiring nodes.
   • Move to nodes only when the app needs custom AST control, worker preparsing, or high-frequency structural updates.
   • When smooth streaming is on outside Vue 3 mode="chat" defaults, pair it with :fade="false".
   • Streaming vs recovering history: when migrating a chat UI, keep mode="chat" on the same chat row and switch pacing/animation props instead. Vue 3 streaming: mode="chat", smooth-streaming="auto", :fade="false". Vue 3 completed chat history: mode="chat", :smooth-streaming="false", optional :fade="true". Use mode="docs" only for separate rich document surfaces.
7. Validate and summarize.
   • Run the smallest relevant tests or build.
   • Report direct mappings, TODOs, and remaining verification work.

Default Decisions

• Renderer swap first, streaming optimization second.
• Smooth streaming is an intermediate option between "just content" and "full nodes migration": it paces visible output without requiring AST control.
• Preserve safety over feature parity when HTML or security rules are involved.
• Prefer explicit TODOs over vague claims.
• Prefer renderer-local component maps where the target framework exposes them.
• Recommend against migration when the current stack depends heavily on transforms that Markstream does not mirror directly.
• When preserving trusted legacy behavior is necessary, use scoped htmlPolicy / html-policy="trusted" and mermaidProps.isStrict = false instead of weakening defaults everywhere.

Useful Doc Targets

• docs/guide/react-markdown-migration.md
• docs/guide/react-markdown-migration-cookbook.md
• docs/guide/ai-chat-streaming.md
• docs/guide/installation.md
• docs/guide/component-overrides.md
• docs/guide/advanced.md