Cloudflare Sandbox Agent Example

Deploy sandbox-agent inside a Cloudflare Sandbox.

Prerequisites

Cloudflare account with Workers Paid plan
Docker running locally for wrangler dev
ANTHROPIC_API_KEY or OPENAI_API_KEY for the coding agents

Setup

Install dependencies:

pnpm install

Create .dev.vars with your API keys:

echo "ANTHROPIC_API_KEY=your-api-key" > .dev.vars

Development

Start the development server:

pnpm run dev

Test the endpoint:

curl http://localhost:8787

Test prompt routing through the SDK with a custom sandbox fetch handler:

curl -N -X POST "http://localhost:8787/sandbox/demo/prompt" \
  -H "Content-Type: application/json" \
  -H "Accept: text/event-stream" \
  -d '{"agent":"codex","prompt":"Reply with one short sentence."}'

The response is an SSE stream with events:

session.created
session.event
prompt.completed
done

Troubleshooting: only two events

If you only see:

outbound session/prompt
inbound prompt result with stopReason: "end_turn"

then ACP session/update notifications are not flowing. In Cloudflare sandbox paths this can happen if you forward AbortSignal from SDK fetch init into containerFetch(...) for long-lived ACP SSE requests.

Use:

const sdk = await SandboxAgent.connect({
  fetch: (input, init) =>
    sandbox.containerFetch(
      input as Request | string | URL,
      {
        ...(init ?? {}),
        // Avoid passing AbortSignal through containerFetch; it can drop ACP SSE updates.
        signal: undefined,
      },
      PORT,
    ),
});

Without session/update events, assistant text/tool deltas will not appear in UI streams.

Deploy

pnpm run deploy

Note: Production preview URLs require a custom domain with wildcard DNS routing. See Cloudflare Production Deployment for details.

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