Runtype Persona

Persona (@runtypelabs/persona) is an open-source chat widget that works with any backend. It is a themeable chat UI with no framework dependency, and it streams from any backend that sends server-sent events. It has first-party Runtype support, so the recommended production path is a Runtype agent 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 with a browser-safe clientToken, and the widget talks to api.runtype.com directly. You need no proxy and no server code. This is the recommended path, and it is what generate_persona_embed_code produces.

If MCP is unavailable and the user wants a starter deploy, run runtype persona init. It creates an agent, a client token, and a snippet you can paste. Without flags, the token is a test token that allows every origin (*). For production, pass --origins https://your-site.example and --environment live.

Persona also runs on other streaming backends through the Persona SSE protocol. Adapter examples cover the Vercel AI SDK, OpenAI Agents, LangGraph, and the Anthropic Claude Agent SDK, among others. Use a self-hosted backend or @runtypelabs/persona-proxy only when you must hide a secret API key or front a non-Runtype agent. Otherwise, use the hosted clientToken embed, which needs no server code.

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_platform_documentation(topic="types-surface-configs") when surface behavior config details matter.
• Use get_persona_theme_reference before custom themes.
• Use generate_persona_embed_code for final snippets whenever possible.

Do not hand-write embed code unless the MCP tools are unavailable. For details not listed here, fetch one of the documentation topics above.

Critical Constants

• Package: @runtypelabs/persona.
• CDN base: https://cdn.runtype.com/persona/latest.
• Installer script: https://cdn.runtype.com/persona/latest/install.global.js.
• Self-contained browser bundle: https://cdn.runtype.com/persona/latest/index.global.js (exposes window.AgentWidget).
• Do not load /index.js (the ESM build) directly in a browser. It keeps bare import specifiers such as marked, fails with Failed to resolve module specifier "marked", and leaves an empty mount. The ESM build is for bundlers (npm) only.
• CSS for npm usage: @runtypelabs/persona/widget.css. For a manual CDN install, use https://cdn.runtype.com/persona/latest/widget.css.
• Init function: initAgentWidget().
• Script installer lifecycle callbacks: onScriptLoad, onLauncherShown, onChatReady(handle), and onError.
• Ready event: persona:chat-ready.
• 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.

Load from cdn.runtype.com

When you load Persona from a CDN, use cdn.runtype.com. Pages published with the publish_page tool load scripts only from cdn.runtype.com, and scripts from other CDNs fail without an error. On a page that Runtype deploys, replace latest with the current published version, for example https://cdn.runtype.com/persona/PERSONA_VERSION/install.global.js, so a new release does not change the widget under your deployed page. Pin the version in the script URL, never as a version or cdn key in data-config.

Build Pattern

1. Create or identify the agent or flow. A chat surface is optional for a basic embed: a token that names the agent in agentIds is enough. You need a chat surface to use WebMCP page tools, because the surface holds the behavior.webmcp policy.
2. Create a scoped client token with create_client_token, or with Runtype.clientTokens.ensure({ name, agentIds, allowedOrigins }) from @runtypelabs/sdk in code. Without a surface, pass agentId to the widget (data-agent-id or config.agentId).
   • create_client_token defaults to environment: "live" and allowed_origins: ["*"], so an unqualified call creates a live token that any origin can use. Pass environment: "test" while you build, and for production list the exact site origins in allowed_origins.
   • Use a test token (ct_test_) only while you build. Test tokens allow localhost automatically.
   • A live token (ct_live_) created in the dashboard is shown once. Save its value when you create it.
3. For a production widget, set a release target on the token so an agent edit does not change the live widget at once. Set target_alias (for example live) and deploy the agent to that alias, or set target_version_id to pin one exact version. A pinned version requires exactly one agent in agentIds. A token with no target resolves like any run that names no version, so depending on your organization's live-default setting, a saved agent edit can reach the widget immediately.
4. Generate embed code with generate_persona_embed_code.
5. For consumer-facing widgets, hide tool calls and reasoning by default.
6. For internal or debug widgets, expose useful traces intentionally.
7. For custom themes, set explicit high-contrast component tokens and verify header, launcher, user message, primary button, tool call, and reasoning bubble contrast.
8. Keep Persona's default HTML sanitization enabled unless all rendered content is trusted.
9. If the assistant should ask structured follow-up questions or suggest replies, set features.askUserQuestion.expose: true or suggestions.followUps.expose: true in the widget config instead of hand-writing duplicate local tools.

If a token value leaks, run regenerate_client_token and update the embed. The old value stops working immediately.

Signed-in and Returning Visitors

• To pass a verified signed-in user to the agent and its tools, set identityProvider (the Identity Exchange integration's provider value, such as clerk or workos) and getIdentityProof in the widget config (Persona 4.24.0 or later). The widget then sends identityProof: { provider, token } on every chat turn and stops the turn when the proof is null. Without identityProvider, the proof goes only on init, so an agent whose tenancyStrategy requires a tenant or end user rejects widget chat. See End-user identity.
• To give each visitor a conversation list that persists, set features.history: { enabled: true } in the widget config and configure behavior.conversationHistory on the chat surface. See Client conversation history.

Fullscreen Assistant Layouts

For ChatGPT-style or 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.

For server-side tools that need the signed-in visitor's identity, pass an Identity Exchange proof as identityProof on /v1/client/init and /v1/client/chat (in Persona, set identityProvider with getIdentityProof), then reference {{_tenant.id}} or {{_endUser.id}} in the tool's header (or send {{_identity.token}} for a signed assertion your API verifies). The model cannot set these values, and the call fails closed when the execution has no identity. Docs: https://docs.runtype.com/developer-guides/guides/tool-template-variables

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 in the host page, for example with registerTool(...). Persona collects them on each turn and runs returned webmcp:<name> calls in the browser.
• Create the client token with product_surface_id set to the chat surface, and include the embedding page origin in allowed_origins. A token that is not bound to the surface drops every page tool. product_surface_id is fixed at creation, so recreate an existing unbound token.
• Enable page tools in the widget config with webmcp: { enabled: true }. Persona asks for approval before every page-tool call. Use webmcp.autoApprove = (info) => ... to skip approval only for safe read-only tools, and webmcp.onConfirm only when the host page needs custom confirmation UI. The 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, for example { origin: "https://store.example.com", tools: ["search_*"] }. The server enforces only enabled and allowlist. behavior.webmcp.requireConfirmFor (for example ["checkout_*"]) is a confirmation hint for Persona, not a security boundary.
• After real traffic, open the surface's WebMCP section in the dashboard to review discovered tools and observed origins. Discovery records the offered page tools before allowlist 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.

Custom Chat UIs Without Persona

A custom browser chat UI that uses a client token calls /v1/client/chat and resumes with /v1/client/resume. That path follows the same surface behavior.webmcp policy as Persona. For an approval_start on a gate with tools.approval.approver: "end-user", POST { sessionId, executionId, approvalId, decision } to /v1/client/approve and read the continued SSE stream as you would from /v1/client/resume. Never send remember. Owner gates never reach a client-token chat; it refuses them with 501.

A trusted server or SDK process can send local tools directly to /v1/dispatch as top-level clientTools[] and resume with /v1/dispatch/resume. This path requires a secret API key, so never run it in a browser. It uses the optional clientToolsPolicy.allowlist and does not use behavior.webmcp, client-token origins, or dashboard discovery.

Verify and Troubleshoot

1. Load the page and send a message in the widget.
2. Confirm that the turn reached Runtype with list_conversations(source="client_token", client_token_id="ct_...") or list_logs.

If the widget loads but does not respond, check the response body in the browser's Network tab:

Status	Error	Fix
401	Invalid client token	Install the current token value. A regenerated token invalidates the old value.
403	Origin not allowed	Add the exact page origin to the token's list, and to the surface's list if it has one.
403	Chat surface is not active	Activate the chat surface.
429	Session message limit reached	Start a new session, or raise max_messages_per_session with update_client_token.

If page tools never run, confirm that the token is bound to the chat surface, that behavior.webmcp.enabled is true. If the surface has a behavior.webmcp.allowlist, confirm that a rule matches the page origin and the tool name. For the full error list and token limits, see Client tokens and domain restrictions.

Related Docs

• Quickstart: From Agent to Chat Widget
• Embedding the chat widget (script tag)
• Embedding the chat widget (React)
• Client tokens and domain restrictions