Title

title() generates a short title for an Agent Invocation. It can use a model, a custom executor, or a local heuristic, then streams or returns the title as output metadata and optionally delivers it to a Channel thread.

The Capability reads the prepared first user message, generates a short title, provides it as a finish extension, and injects title data into compatible streams. When that message has no semantic text, such as an attachment-only audio or image message, it waits for the successful Agent reply and uses that text instead. Applications can use the finish extension to name a job, run, artifact, or other durable record without depending on a chat interface. It can limit title generation to selected Agent Trigger ids.

Configure titles

Attach title() to any Agent Definition that needs a generated title. When no model is available to the Capability, ViteHub falls back to a short heuristic title.

import { defineAgent } from 'vite-hub/agent'
import { title } from 'vite-hub/agent/capabilities'

export default defineAgent({
  driver: { model },
  capabilities: [
    title(),
  ],
})

How titles are generated

title() runs in the output phase. It wraps compatible async streams or UI message streams so the title can arrive alongside the response, and it provides { title } in the finish extension.

Input Capabilities run first, so transcribe() can replace audio with transcript text before title() reads it. Audio with authored text uses both in their prepared order. If the prepared input is still empty, title() waits for the normalized Agent reply; when that reply is also empty or the invocation fails, it leaves the title unset.

For framework-managed Chat SDK message Channels, ViteHub also delivers the title once per thread by default, even when each webhook contains only the current message or the handler is recreated. Follow-up Channel invocations skip title generation after successful delivery. Set channelDelivery: "always" to refresh the platform title on every invocation. Plain runAgent() and UI invocations without framework-managed Chat SDK delivery still receive stream data and finish extensions per invocation.

The Capability avoids wrapping the same result twice.

Requirements

title() needs message-shaped input with at least one user message and semantic text from either the prepared input or a successful Agent reply. A model, custom executor, or heuristic path must be available.

Use a custom template, variables, or executor when the title must include product-specific context.

Driver support

Verify titles

Run one Agent Invocation and inspect the stream for title data. Confirm that the finish extension includes { title } when title generation succeeds.

Test a vague first message and confirm the fallback title is used instead of an empty string.

Options

Related pages

• chat()
• chatSummary()