Streaming

Call stream() instead of prompt() to iterate the run's events as they arrive. Collect TextDelta events for the answer text; the loop still runs the full pipeline (tools execute, approvals surface) before the stream ends. In a controller, return ->toResponse() to send SSE straight to the client.

use Crustum\Ai\AnonymousAgent;
use Crustum\Ai\Streaming\Event\TextDelta;

$stream = (new AnonymousAgent('You are a probe.', [], []))->stream('Say hello.');

$text = '';
foreach ($stream as $event) {
    if ($event instanceof TextDelta) {
        $text .= $event->delta;
    }
}
echo $text . PHP_EOL;

Say hello back.

then() registers a callback invoked with the final StreamedAgentResponse once streaming completes ($response->text, ->usage, ->events).

Stopping mid-stream

Pass stopCheck: a predicate polled between chunks. When it returns true, the stream aborts with StoppedException. Console drivers use this for Ctrl+C: the predicate reads a stop signal, and the catch maps the exception to a stopped turn instead of an error:

use Crustum\Ai\AnonymousAgent;
use Crustum\Ai\Exception\StoppedException;

$stream = (new AnonymousAgent('You are a probe.', [], []))
    ->stream('Say hello.', stopCheck: fn () => true);

try {
    foreach ($stream as $event) {
        // never reached: the predicate fires before the first chunk
    }
    echo "finished\n";
} catch (StoppedException) {
    echo "stopped\n";
}

stopped

Chat endpoints

A chat endpoint parses the frontend's request into a Chat input, resumes the thread, and returns the protocol-encoded stream as the response. The Chat carries the thread id and the client's protocol (AG-UI or Vercel), so one action serves both:

use Crustum\Ai\AgentUserInteraction\AgentUserInteraction;

class ChatController extends AppController
{
    public function run(): Response
    {
        $this->request->allowMethod(['post']);

        $chat = AgentUserInteraction::chat($this->request);

        $user = $this->request->getAttribute('identity');

        return (new SupportAgent())
            ->continue($chat->threadId(), as: $user)
            ->stream($chat)
            ->usingProtocol($chat->protocol())
            ->toResponse();
    }
}

usingVercelDataProtocol() / usingAgentUserInteractionProtocol() do the same without parsing a request, for streams you drive yourself. Either way the frontend gets native tool-approval parts (Vercel) or interrupts (AG-UI).

Where next

• Agents — lifecycle and prompting
• Structured output — typed responses
• Approvals — human gates on tool calls