Build apps
Build serverless apps
Build Cloudflare Workers, AWS Lambda, Vercel and Netlify functions in a project and see them working in the preview.
Build Cloudflare Workers, AWS Lambda, Vercel and Netlify functions in a project and see them working in the preview.
Ask the agent for an app built as serverless functions, or import a project that already is one (it has a wrangler.toml, template.yaml, vercel.json, netlify.toml or serverless.yml). The agent runs the platform’s local emulator in the project’s sandbox, so the functions answer in the preview like any other app.
Nothing uses your cloud account. The agent doesn’t sign in to Cloudflare, AWS or Vercel, and doesn’t deploy there. Publish puts what the preview runs on a OneDrop address, as for any project. See Publish.
| Platform | What the preview runs |
|---|---|
| Cloudflare Workers and Pages | wrangler dev, with Cloudflare’s own runtime. D1, KV, R2, Durable Objects and Queues are emulated. |
| AWS Lambda (SAM) | sam local start-api, each function in a Lambda container. Needs Docker inside sandboxes. |
| Vercel | The framework’s own dev server (next dev for Next.js), whose routes are the functions. |
| Netlify | netlify dev --offline |
| Serverless Framework | Version 3 with serverless-offline. Version 4 needs a sign-in for every command. |
| Google Cloud and Azure Functions | The Functions Framework and Azure Functions Core Tools. |
SST isn’t supported, because sst dev needs a real AWS account. Firebase’s emulators need Java, which sandboxes don’t have.
An admin turns on Docker inside sandboxes in Settings → Sandboxes first. See Docker inside sandboxes.
AWS services the functions use run as local stand-ins in the sandbox’s Docker: DynamoDB Local, S3Mock for S3, and ElasticMQ for SQS. The code reaches them through the AWS SDK’s standard endpoint settings (AWS_ENDPOINT_URL_DYNAMODB and the like), so it has nothing that only works locally. A setup script creates the app’s tables, buckets and queues, and adds sample data.
LocalStack emulates more of AWS, but needs a LocalStack account. To use it, add your LOCALSTACK_AUTH_TOKEN in Tools → Secrets. Its free plan is for non-commercial use.
The agent runs the framework’s dev server instead of vercel dev, which needs a Vercel sign-in. Rewrites and headers from vercel.json move into the framework’s config.
A bare api/ folder with no framework has no dev server of its own. The agent suggests moving its functions into the app’s framework. To keep the folder as it is, add a VERCEL_TOKEN in Tools → Secrets. The first run then links the folder to a project in your Vercel account.