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Sandbox Migrate To Next

CloudflareOfficialPublished by Cloudflare

  • Skill
  • Workflow
  • Cloud and DevOps
  • Apache-2.0
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From the author

Migrate Cloudflare Sandbox apps from stable @cloudflare/sandbox to @cloudflare/sandbox@next (SDK 1.0 preview). Use sandbox-next for apps already on the preview.
— the description by Cloudflare

AutoGineer summary

Written by AutoGineer from the skill’s own files, not by the author

This skill provides a structured procedure for migrating existing Cloudflare Sandbox applications from the stable SDK to the 1.0 preview (@next) version. It covers code refactoring, package updates, container image configuration, and the required deployment strategy for production cutover. The workflow emphasizes safety by requiring user confirmation before production changes and provides a clear mapping of deprecated stable APIs to their new @next counterparts.

What it does

  • Audits existing codebases for deprecated stable SDK patterns.
  • Provides a comprehensive mapping of stable APIs to @next equivalents.
  • Guides the update of package dependencies and Dockerfile images.
  • Outlines the necessary code changes for process execution, terminal handling, and interpreter usage.
  • Defines the required deployment strategy using immediate container rollouts.
  • Includes a validation checklist to ensure the migration is successful.

When to use it

  • When you are ready to migrate an existing stable Cloudflare Sandbox application to the 1.0 preview.
  • When you need to ensure your application is prepared for the upcoming 1.0 stable release.
  • When you need to refactor code that relies on deprecated stable SDK features like transport settings or session management.

Advantages

  • Ensures alignment between Worker packages and container images.
  • Prevents common pitfalls like gradual rollouts during breaking changes.
  • Provides clear, actionable steps for complex refactors like process handling.
  • Reduces risk by requiring explicit user approval for production cutovers.

Usage examples

“Help me migrate my current Cloudflare Sandbox project to the 1.0 preview.”
The agent will initiate the audit process, list the necessary code changes based on the replacement map, and guide you through the package and image updates.
“How do I update my exec calls for the new SDK?”
The agent will provide the new pattern for using process handles and the .output() method instead of the previous buffered result approach.

Install

  1. Download the skill as a ZIP:

    https://autogineer.com/agent-skills/cloudflare/sandbox-migrate-to-next/download
  2. Unzip it into the cross-client skills folder of your project:

    mkdir -p .agents/skills && unzip sandbox-migrate-to-next.zip -d .agents/skills

Documentation by Cloudflare

Migrate stable → Sandbox SDK 1.0 preview (@next)

Perform the port. Follow the steps in order. Depth lives in docs—fetch the linked page when a step needs detail.

Human guide: Migrate · 1.0 preview

New projects should start on @next (sandbox-next), not this skill. Day-to-day stable work → sandbox-stable. Deprecated-API cleanup without moving to @next → 2026 deprecation guide first if needed.

Existing apps should migrate when you can, so you are ready when 1.0 becomes the stable release. Do not force production cutover without the user agreeing.

Prefer installed @next types and the migrate doc over memory.

Workflow

  1. Review hard rules and the replacement map

  2. Audit the codebase; list hits and target shapes

  3. Clarify with the user (cutover, bridge, Python image, unclear sites)

  4. Upgrade package, image, and code

  5. Validate

Stop after any step that needs a user decision.

Hard rules

  • Worker package and container image must be the same @next line.

  • Production cutover uses immediate container rollout. Stable and @next control protocols are incompatible both ways; gradual rollout leaves a broken mixed window. In-flight container work can stop.

  • After cutover, await sandbox.exec(...) means process started, not command finished.

  • Argv is as-is (no implicit shell). Shell syntax needs an explicit shell binary.

  • Process handles have no stdin → terminals for interactive input.

  • Observation timeout / AbortSignal cancel the wait only, not the process.

  • No single retry loop for every error.

  • Do not invent APIs (gitCheckout on core, process stdin, string-exec completion helper).

  • Self-deployed bridge stays on stable (not part of the preview line yet).

Replacement map

Stable@next
SANDBOX_TRANSPORT / transport / setTransportRemove — RPC only
await sandbox.exec("cmd") → buffered resultawait sandbox.exec(argv) → handle, then output / waits
execStream / startProcessSame handle: logs, waitFor*, kill
Default / named sessionsGone — cwd/env per launch, or one shell script
sandbox.terminal(request) / session terminalcreateTerminal + terminal.connect(request)
xterm sessionIdterminalId
Interpreter methods on SandboxwithInterpreter → sandbox.interpreter.*
gitCheckoutargv git via exec
String kill signalsNumeric only
Files, mounts, backups, ports, tunnels, proxyToSandboxMostly unchanged (ignore session/transport bits on stable pages)

Depth: Migrate · after port, day-to-day → sandbox-next

Audit

rg 'SANDBOX_TRANSPORT|transport:|setTransport|enableDefaultSession|createSession|getSession|deleteSession|execStream\(|startProcess\(|killProcess\(|sandbox\.terminal\(|sessionId|gitCheckout\(|SandboxTransport|ExecutionSession'

Also: string exec(, cd then a later exec, bare createCodeContext / runCode on Sandbox.

Clarify (ask when needed)

  • OK to cut production with --containers-rollout=immediate (live processes/terminals/streams may stop)?

  • Self-deployed bridge? Leave on stable.

  • Python interpreter → -python image variant?

  • Call sites not covered by the map?

Upgrade

Package and image
npm install @cloudflare/sandbox@next
FROM cloudflare/sandbox:next
# Python: cloudflare/sandbox:next-python

Same prerelease tag on Worker and image when not on floating next.

Code by area

Apply replacements from the map. For each area, implement from the doc—not from stable habits:

AreaDoc
Commands / handles / waitsProcesses · Processes API
cwd / env / secretsEnvironment · Outbound traffic
Drop sessionsMigrate · Lifecycle
TerminalsTerminals
InterpreterInterpreter
ErrorsErrors
Durable job across requestsProcess execution — lifetime / durability

Commands (shape):

// Before (stable)
const result = await sandbox.exec("npm test");

// After (@next)
const process = await sandbox.exec(["/bin/bash", "-lc", "npm test"]);
const result = await process.output({ encoding: "utf8" });
const server = await sandbox.exec(["/bin/bash", "-lc", "npm run dev"], {
  cwd: "/workspace/app",
});
await server.waitForPort(3000, { timeout: 60_000 });
await server.kill(); // numeric; default 15

Terminals (shape):

const terminal = await sandbox.createTerminal({ command: ["bash"], cwd: "/workspace" });
const t = await sandbox.getTerminal(terminal.id);
if (!t) return new Response("terminal gone", { status: 410 });
return t.connect(request, { cursor, cols, rows });

Interpreter (shape):

import { Sandbox as BaseSandbox } from "@cloudflare/sandbox";
import { withInterpreter } from "@cloudflare/sandbox/interpreter";

export class Sandbox extends BaseSandbox<Env> {
  interpreter = withInterpreter(this);
}

Git (shape):

const clone = await sandbox.exec(
  ["git", "clone", "--depth", "1", "--", repoUrl, "/workspace/repo"],
  { cwd: "/workspace" },
);
const result = await clone.output({ encoding: "utf8" });

Delete transport settings entirely. Remove session APIs. Isolate users with separate sandbox IDs.

Deploy cutover

Staging/branch first. Production is one deploy of matching Worker + image:

npx wrangler deploy --containers-rollout=immediate

Leave rollout_active_grace_period at default 0 (or set 0 if raised). After cutover, pre-deploy process/terminal IDs are invalid. Details: Migrate · Container rollouts

Validate

  1. Lockfile + Dockerfile on the same @next line

  2. Typecheck against @next

  3. Smoke argv exec + output({ encoding: "utf8" })

  4. Smoke long process / terminal / interpreter if used

  5. Errors distinguished: unavailable / interrupted-RPC / stale / local wait

  6. No live secrets in sandbox env

  7. Grep again for removed APIs

  8. Production used --containers-rollout=immediate

Then day-to-day work uses sandbox-next.

Red flags — stop and fix

  • Mixing @next Worker with stable image (or reverse)

  • Gradual container rollout for this cutover

  • Treating await exec as command completion

  • Assuming cd / exports persist across exec calls

  • One retry wrapper for every error

  • Inventing gitCheckout, process stdin, or undocumented APIs

  • Keeping pre-cutover process/terminal IDs after deploy

  • Forcing production cutover without user agreement

  • Putting live secrets in setEnvVars / launch env

Skill feedback

If the user reports that this skill gave incorrect or outdated guidance, or is missing information, read references/skill-feedback.md.

Files

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Requirements and compatibility

Works with: Claude Code, Claude apps, OpenAI Codex, GitHub Copilot, Cursor, Gemini CLI, Kiro, OpenCode, Goose, Amp, Roo Code, JetBrains Junie, Factory Droid, Devin (ex-Windsurf), Mistral Vibe, OpenHands, Letta

“Works with” means the tool reads the open Agent Skills format; a skill written for one tool may use features others lack.

Needs: Needs Python, Needs Node.js

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Attribution and licence

Published by
Cloudflare
Publisher
Cloudflare (Official)
Source
cloudflare/skills · skills/sandbox-migrate-to-next · commit 6eb6c78
Licence
Apache License 2.0 (redistribution allowed)
  • LICENSE (added by AutoGineer from LICENSE)
  • ATTRIBUTION.md (written by AutoGineer)
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