Progress summary

progressSummary() observes reasoning and tool lifecycle events while an Agent works, then emits a replaceable one-sentence status as transient data-progress-summary stream data.

Add progress summaries

Import the Capability from @vite-hub/agent/capabilities and give it the independent Agent Driver that writes progress:

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

export default defineAgent({
  driver: primaryDriver,
  capabilities: [
    progressSummary({
      driver: {
        kind: 'codex',
        model: 'gpt-5.6-luna',
      },
    }),
  ],
})

The Capability owns the summarizer instructions. The configured Driver selects the model and execution environment using the same contract as an Agent Definition or title().

Render the current summary

Listen for data-progress-summary parts and replace the currently displayed sentence when revision increases:

{
  type: 'data-progress-summary',
  data: {
    type: 'progress-summary',
    summary: 'Checking current SKU costs against the planning data.',
    revision: 1,
  },
}

The part is transient, so it does not become conversation history. Keep structured reasoning and tool logs separate when your interface exposes them.

With manual chat delivery, ViteHub edits the current placeholder as summaries arrive. When the Agent finishes, ViteHub deletes that placeholder and posts the final reply as a new message so chat platforms can deliver their normal notification.

Understand the runtime behavior

With event-driven intervalMs: 0, the Capability starts its initial summary when the first non-terminal primary stream chunk arrives. A terminal-only or failed stream does not start unused auxiliary work.

Positive intervals begin when the first primary stream chunk arrives and use a fixed cadence from that point, so auxiliary generation never delays primary Driver startup. At most one generation runs at a time, and interval ticks are skipped while a generation is pending. Set intervalMs: 0 to generate from reasoning and tool activity through the event-driven microtask behavior instead. Activity that arrives during an event-driven generation schedules one follow-up after it settles. Raw reasoning, tool input, and tool output are excluded from the generated prompt; reasoning is represented only as an Active presence signal.

The default prompt uses only reasoning presence, sanitized tool names, and the previous summary. It does not include user message text, code, commands, paths, traces, hidden instructions, credentials, raw tool details, or trusted <context> payloads.

The Capability stops its cadence and aborts every in-flight generation when the parent invocation aborts or the primary stream finishes, cancels, or errors. A generation failure does not interrupt the primary response stream; ViteHub emits a sanitized warning and trace event without logging the Driver error message.

Requirements

The primary Agent Driver must expose a compatible async stream or UI message stream. With a positive interval, the Capability attempts a summary on every tick and suppresses unchanged output. With intervalMs: 0, it remains silent after the first-chunk summary until reasoning or tool lifecycle events provide new activity.

Configure a driver, model, or execute option for summary generation. Without one of those options, the Capability uses the Agent model when available.

Driver support

Verify the result

Run an invocation and confirm that the primary stream continues immediately while an initial transient data-progress-summary part arrives. Keep the invocation open beyond intervalMs, then confirm that a later changed summary arrives with a higher revision.

Stop the invocation before the next interval and confirm that no later progress part appears.

Options

String templates use @vite-hub/markdown-template and receive userText, the reasoning presence signal, activeTools, completedTools, and previous. Referencing userText opts a custom template into handling user message text; keep sensitive content out of prompts you construct.

Related pages

• title()
• Agent Drivers
• Markdown pages