Programmatic Control

What is this?

Programmatic control is what you reach for when you want to drive an agent run from code rather than from a chat composer — a button, a form, a cron job, a keyboard shortcut, a graph callback. CopilotKit exposes three primitives that cover every triggering pattern:

• agent.addMessage(...) — append a message to the conversation without running the agent. Pair with copilotkit.runAgent({ agent }) when you want the appended message to kick off a turn.
• copilotkit.runAgent({ agent }) — the same entry point <CopilotChat /> calls under the hood. Orchestrates frontend tools, follow-up runs, and the subscriber lifecycle.
• agent.subscribe(subscriber) — low-level AG-UI event subscription (onCustomEvent, onRunStartedEvent, onRunFinalized, onRunFailed, …). Pairs with agent.runAgent({ forwardedProps: { command: { resume, interruptEvent } } }) to drive interrupt resolution from arbitrary UI.

Every example on this page is pulled from two live cells: headless-complete (full chat surface, shown here for the message-send path) and interrupt-headless (button-driven interrupt resolver, shown here for the subscribe + resume path).

When should I use this?

Use programmatic control when you want to:

• Trigger agent runs from buttons, forms, or other UI elements
• Execute specific tools directly from UI interactions (without an LLM turn)
• Build agent features without a chat window
• Access agent state and results programmatically
• Create fully custom agent-driven workflows

Sending a message from code

The message-send path in headless-complete is the canonical pattern: append a user message with agent.addMessage, then call copilotkit.runAgent({ agent }). The same handleStop calls copilotkit.stopAgent({ agent }) to cancel mid-run. Note the connectAgent effect at the top — it opens the backend session on mount so the very first runAgent doesn't race the handshake.

copilotkit.runAgent() vs agent.runAgent()

Both methods trigger the agent, but they operate at different levels:

• copilotkit.runAgent({ agent }) — the recommended default. Orchestrates the full lifecycle: executes frontend tools, handles follow-up runs, and routes errors through the subscriber system.
• agent.runAgent(options) — low-level method on the agent instance. Sends the request to the runtime but does not execute frontend tools or chain follow-ups. Reach for this only when you need direct control — the canonical example is resuming from an interrupt with forwardedProps.command.

Subscribing to agent events

agent.subscribe(subscriber) returns { unsubscribe }. The subscriber object accepts every AG-UI lifecycle callback — onCustomEvent, onRunStartedEvent, onRunFinalized, onRunFailed, and the streaming deltas. Use it to drive custom progress UI, forward events to analytics, or — the pattern below — catch LangGraph interrupt(...) events and resume with a payload.

Resolving a LangGraph interrupt from a button

The interrupt-headless cell demonstrates the full pattern without useInterrupt or a chat surface. A plain hook subscribes to on_interrupt custom events, buffers the payload until the run finalizes (so the UI doesn't flash mid-stream), and exposes a resolve(response) callback that calls copilotkit.runAgent({ agent, forwardedProps: { command: { resume, interruptEvent } } }) to unblock the graph:

The resulting { pending, resolve } tuple is pure data — any UI can drive it. The cell itself renders a simple button grid, but the same hook would power a modal, a toast, a sidebar form, or a voice UI.

See also

• Headless UI — the full useRenderedMessages composition that mirrors <CopilotChatMessageView> line-for-line.
• Human-in-the-Loop — the useHumanInTheLoop and useInterrupt hooks with their render-prop contracts, for the "paused mid-chat" pattern this page's headless variant replaces.

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