@bndynet/ichat-messages

Core chat message UI as Lit Web Components. Markdown rendering with syntax highlighting, pluggable fenced-block renderers, collapsible reasoning, streaming previews, and tool-call / to-do support.

For long histories, virtual scrolling defaults to 'auto' — it automatically engages when the message count exceeds 500. Set config.virtualScroll = true for always-on or false for always-off. The regular keyed list is the automatic fallback when the virtualizer cannot load.

While virtual scrolling is active, off-screen rows are not in the DOM. Browser find-in-page, selection spanning the whole history, and printing therefore cover only the rendered range, and custom parts must keep durable state in message data rather than in private DOM state. Set config.virtualScroll = false if those matter more than large-history performance.

Install

npm install @bndynet/ichat-messages

Components

| Component | Tag | | --------------- | -------------------- | | ChatMessages | <i-chat-messages> | | ChatMessage | <i-chat-message> | | ChatPartHost | <i-chat-part> | | ChatTextPart | <i-chat-text> | | ChatToolCall | <i-chat-tool-call> | | ChatTodo | <i-chat-todo> | | ChatReasoning | <i-chat-reasoning> | | ChatSpinner | <i-chat-spinner> |

Extension APIs

• registerCodeRenderer(renderer) — custom fenced-code-block renderers; output is sanitised by default, with trusted: true as an explicit opt-in for audited renderers that need rich output during streaming
• registerMarkdownPlugin(plugin) — markdown-it plugins with auto CSS injection
• registerPartRenderer(renderer) — custom parts[] type renderers (e.g. file, source, x-*)

All three global registries support runtime registration. New extensions affect subsequently added or updated content without automatically refreshing existing rendered content. Same-object registration is idempotent, while a different object with the same name/id warns and keeps the first registration.

Dependencies

All runtime dependencies are auto-installed:

| Package | Purpose | | -------------- | -------------------------- | | lit | Web Component framework | | markdown-it | Markdown rendering | | dompurify | HTML sanitization | | highlight.js | Syntax highlighting | | morphdom | DOM patching for streaming |

License

MIT