Sandbox SDK 2026 deprecation migration

Use this skill when migrating a codebase that depends on the Cloudflare Sandbox SDK away from features deprecated in June 2026.

For the announcement, refer to the changelog entry. For detailed documentation, refer to the migration guide.

Migration checklist

1. Update @cloudflare/sandbox and the sandbox container image before changing runtime configuration.

2. Search the codebase for deprecated configuration and APIs:

   Copy

   rg 'SANDBOX_TRANSPORT|transport:|exposePort\(|enableDefaultSession|execStream\(|readFileStream|writeFileStream'

3. Switch every sandbox to RPC transport with SANDBOX_TRANSPORT=rpc or getSandbox(..., { transport: "rpc" }).

4. Replace Sandbox SDK desktop APIs with Cloudflare Browser Run where browser automation is required.

5. Replace exposePort() with sandbox.tunnels.get(). Use quick tunnels for development and named tunnels for stable production hostnames.

6. Set enableDefaultSession: false on getSandbox().

7. Replace workflows that depend on persisted shell state with explicit sessions from sandbox.createSession().

8. Move stream-specific file and command logic to the base readFile(), writeFile(), and exec() APIs where streaming behavior is supported.

9. Deploy the Worker and smoke-test command execution, file operations, public URLs, and stateful session workflows.

API replacements

Notes for agents

• Do not remove exposePort() blindly if the Worker uses proxyToSandbox() to inject authentication or rewrite responses. Preserve that behavior before moving traffic to tunnels.
• If code relies on cd carrying across separate exec() calls, create an explicit session with cwd instead.
• Tunnels require RPC transport. Configure RPC before migrating public URLs.
• Large or binary file streaming requires RPC transport.