Add new OpenCode x Sandboxes demo with remote tool calls

[aron-cf]

Adds an experimental example showing OpenCode running inside a Cloudflare Sandbox, with all tool calls (bash, read, write, edit, grep, glob, list) routed through an isolated CodeSandbox rather than the container's own filesystem.

The demo aims to demonstrate how workers can provide a capnproto RPC API very easily to services (either internally or externally) that allow easy interaction with those primatives.

class SandboxRpcApi extends RpcTarget {
  #env: Env;

  constructor(env: Env) {
    super();
    this.#env = env;
  }

  async sandbox(sessionId: string) {
    return getSandbox(this.#env.SANDBOX, `session-${sessionId}`);
  }
}

Then consumed in the OpenCode plugin:

const api = await getSandbox();
    const result = await api
      .sandbox(context.sessionID)
      .exec(args.command, { timeout: args.timeout });

Also includes a small addition to @cloudflare/sandbox's OpenCode integration: exposes process on OpencodeServer and adds an onStart callback to OpencodeOptions, invoked only when the server is freshly started (not reused). The example uses this to stream OpenCode logs to the Worker's console.

Architecture

Two containers back the Worker:

• OpenCodeSandbox — runs opencode serve with a custom plugin that opens a Cap'n Web WebSocket server on port 3001
• CodeSandbox — one instance per OpenCode session; all tool calls are routed here via RPC

The Durable Object connects to the plugin over Cap'n Web and exposes a SandboxRpcApi that maps each tool call to the correct per-session CodeSandbox.

Testing

cd examples/experimental/opencode
npm run dev
opencode attach http://localhost:8787

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Latest commit: c73bb6f

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/cloudflare/sandbox-sdk/@cloudflare/sandbox@534

commit: c73bb6f

[github-actions]

🐳 Docker Images Published

Variant	Image
Default	cloudflare/sandbox:0.0.0-pr-534-c73bb6f
Python	cloudflare/sandbox:0.0.0-pr-534-c73bb6f-python
OpenCode	cloudflare/sandbox:0.0.0-pr-534-c73bb6f-opencode
Musl	cloudflare/sandbox:0.0.0-pr-534-c73bb6f-musl
Desktop	cloudflare/sandbox:0.0.0-pr-534-c73bb6f-desktop

Usage:

FROM cloudflare/sandbox:0.0.0-pr-534-c73bb6f

Version: 0.0.0-pr-534-c73bb6f

---

📦 Standalone Binary

For arbitrary Dockerfiles:

COPY --from=cloudflare/sandbox:0.0.0-pr-534-c73bb6f /container-server/sandbox /sandbox
ENTRYPOINT ["/sandbox"]

Download via GitHub CLI:

gh run download 23646265198 -n sandbox-binary

Extract from Docker:

docker run --rm cloudflare/sandbox:0.0.0-pr-534-c73bb6f cat /container-server/sandbox > sandbox && chmod +x sandbox