Runtype Persona

Persona (@runtypelabs/persona) is an open-source, backend-agnostic chat widget: a themeable, zero-framework chat UI that streams from any SSE-capable backend. It ships first-party Runtype support, so the easiest production path is a Runtype chat surface with a browser-safe clientToken. Use this skill for website widgets, assistant layouts, deployment snippets, theming, artifacts, WebMCP page tools, and local browser tools.

Where to Deploy

Default to Runtype. Embed against a Runtype chat surface with a browser-safe clientToken and the widget talks to api.runtype.com directly — no proxy and no server code. This is the recommended path and what generate_persona_embed_code produces. If MCP is unavailable and the user wants a starter deploy, runtype persona init creates a simple agent, origin-scoped client token, and paste-ready snippet.

Persona also runs on any other streaming backend via the Persona SSE protocol, with adapter examples for the Vercel AI SDK, OpenAI Agents, LangGraph, and the Anthropic Claude Agent SDK, among others. Reach for a self-hosted backend or @runtypelabs/persona-proxy only when you must hide a secret API key or front a non-Runtype agent — otherwise the hosted clientToken embed is simpler and has fewer moving parts.

Required First Calls

When MCP is available:

• Use get_platform_documentation(topic="persona-embed") for current embed docs.
• Use get_platform_documentation(topic="persona-fullscreen-assistant") for fullscreen

split-pane assistant layouts.

• Use get_persona_theme_reference before custom themes.
• Use generate_persona_embed_code for final snippets whenever possible.
• Read runtype://types/surface-configs directly when surface behavior config details

matter.

Do not hand-write embed code unless the MCP tools are unavailable. If the task needs details not listed here, fetch persona-embed, persona-fullscreen-assistant, or types-surface-configs rather than adding more embed prose to this skill.

Critical Constants

• Package: @runtypelabs/persona.
• CDN base (Runtype's first-party CDN): https://cdn.runtype.com/persona/latest for

ordinary embeds. Use cdn.runtype.com everywhere — it is required on pages deployed through Runtype (a static app or any Runtype-hosted page): their strict CSP only allows scripts/styles from the page origin and https://cdn.runtype.com, so third-party CDNs (jsdelivr, unpkg, esm.sh) are blocked and fail silently. On a Runtype-deployed page, replace latest with a pinned version (e.g. /persona/4.6.0/) so a new release can't shift the widget code under your immutable app bundle.

• Global script: https://cdn.runtype.com/persona/latest/install.global.js.
• ESM entry: https://cdn.runtype.com/persona/latest/index.js.
• CSS for ESM/npm usage: @runtypelabs/persona/widget.css (or https://cdn.runtype.com/persona/latest/widget.css for CDN/ESM installs).
• Init function: initAgentWidget().
• Script installer lifecycle callbacks: onScriptLoad, onLauncherShown,

onChatReady(handle), and onError.

• Ready event: persona:chat-ready; do not use the removed persona:ready event.
• Direct initAgentWidget() returns the handle; its onChatReady option is a fire-only

callback, not the primary way to get the handle.

• Controller events include user:message and assistant:complete.

Common wrong answers: @runtype/persona, Persona.mount(), window.Persona, index.umd.js, missing widget.css, persona:ready, onReady, widget:ready, message:sent, or message:received.

Build Pattern

1. Create or identify the product, agent/flow capability, and chat surface.
2. Create a scoped client token with create_client_token.
3. Generate embed code with generate_persona_embed_code.
4. For consumer-facing widgets, hide tool calls and reasoning by default.
5. For internal/debug widgets, expose useful traces intentionally.
6. For custom themes, set explicit high-contrast component tokens and verify header,

launcher, user message, primary button, tool call, and reasoning bubble contrast.

1. Keep Persona's default HTML sanitization enabled unless all rendered content is

trusted.

1. If the assistant should ask structured follow-up questions or suggest replies, set

features.askUserQuestion.expose: true or features.suggestReplies.expose: true in the widget config instead of hand-writing duplicate local tools.

Fullscreen Assistant Layouts

For ChatGPT/Claude-style layouts, read the fullscreen assistant resource first. The default launcher embed is not enough. Fullscreen layouts usually need full-height mode, panel chrome changes, a persistent shell, an artifact pane, composer customization, and layout-specific token choices.

Local Tools

Use browser-side local tools when the assistant needs to read page state or trigger UI actions that are only available in the front end. For Persona widgets these are WebMCP page tools registered on document.modelContext and admitted by the chat surface's behavior.webmcp policy. Pair local tools with hidden parameters when authenticated context should not enter model context.

Good local tool examples:

• Read current page HTML or selected DOM regions.
• Navigate to a record detail page.
• Open a modal or fill a safe form.
• Read browser-only state that has no server API.

Required WebMCP setup:

• Register page tools on document.modelContext (e.g. registerTool(...)) in the host

page. Persona snapshots them per turn into clientTools[] and runs returned webmcp:<name> calls back in the browser.

• Create a client token whose allowedOrigins includes the embedding page origin.
• Enable page-tool consumption in the widget config with webmcp: { enabled: true }.

Persona shows native approval bubbles by default; use webmcp.autoApprove = (info) => ... only for safe reads and webmcp.onConfirm only when the host page needs custom confirmation UI. Widget-side webmcp.allowlist is a convenience filter, not a security boundary.

• Set the chat surface behavior.webmcp.enabled to true.
• Add origin-scoped behavior.webmcp.allowlist rules for page tools that should be

callable, e.g. { origin: "https://store.example.com", tools: ["search_*"] }. Use behavior.webmcp.requireConfirmFor (a Persona-side UX hint, e.g. ["checkout_*"]) to force per-call confirmation; server-side enforcement is enabled + allowlist.

• Use the dashboard WebMCP tab to review discovered tools and observed origins after

real traffic. Discovery records the offered page tools before allow-list filtering.

• Do not confuse WebMCP page tools with an mcp surface. WebMCP runs inside the

browser page; an mcp surface exposes Runtype capabilities to external AI clients.

• Advanced custom chat UIs or server proxies can bypass Persona and send WebMCP-style

local tools directly to API-key /v1/dispatch as top-level clientTools[], then resume via /v1/dispatch/resume. This is not the default browser embed path and must run from a trusted server or SDK process because it requires a secret API key. Raw dispatch uses optional clientToolsPolicy.allowlist; it does not use behavior.webmcp, client-token allowedOrigins, or dashboard discovery telemetry. Custom public-token browser UIs should use /v1/client/chat plus /v1/client/resume instead; that path follows the same surface behavior.webmcp policy as Persona.

If the umbrella runtype skill is installed alongside this focused skill, its durable references provide fallback snippets and working-mode tradeoffs. This skill must still work when installed by itself; prefer live MCP docs over local sibling files.