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The SST CLI is configured through the sst.config.ts file in your project root. This file defines your app, its providers, and all resources.

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Basic structure

A minimal sst.config.ts looks like this:
sst.config.ts
export default $config({
  app(input) {
    return {
      name: "my-app",
      removal: input?.stage === "production" ? "retain" : "remove",
      home: "aws",
    };
  },
  async run() {
    // Your resources go here
  },
});

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App configuration

The app function returns configuration for your application:

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name

Type: string The name of your app. This is used to prefix all resources. 
name: "my-app"

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home

Type: string The default provider for your app. Can be aws, cloudflare, etc. 
home: "aws"

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removal

Type: "remove" | "retain" | "retain-all" The removal policy for resources:
  • remove - Resources are deleted when you run sst remove
  • retain - Resources are kept when you run sst remove
  • retain-all - All resources are kept
removal: input?.stage === "production" ? "retain" : "remove"

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providers

Type: Record<string, string | ProviderConfig> Define the providers your app uses: 
providers: {
  aws: "6.27.0",
  cloudflare: {
    version: "5.0.0"
  }
}

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Run function

The run function is where you define your resources: 
async run() {
  const bucket = new sst.aws.Bucket("MyBucket");
  const api = new sst.aws.Function("MyApi", {
    handler: "src/api.handler",
    link: [bucket],
  });
  
  return {
    api: api.url,
  };
}
The returned values are outputs that will be displayed after deployment.

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Environment variables

You can access environment variables in your config: 
export default $config({
  app(input) {
    return {
      name: process.env.APP_NAME || "my-app",
      // ...
    };
  },
});

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Stage-specific configuration

Use the input parameter to configure based on stage: 
export default $config({
  app(input) {
    return {
      name: "my-app",
      removal: input?.stage === "production" ? "retain" : "remove",
      home: "aws",
    };
  },
  async run() {
    const isProd = $app.stage === "production";
    
    new sst.aws.Function("MyFunction", {
      handler: "src/index.handler",
      memory: isProd ? "2 GB" : "1 GB",
    });
  },
});

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Watch configuration

Configure which files trigger a redeploy in sst dev: 
export default $config({
  app(input) {
    return {
      name: "my-app",
      watch: ["src/**/*.ts"],
    };
  },
});

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