cdk-local-lambda

Run Lambda functions from your CDK stack locally. Edit your code and see changes immediately—no redeployment required.

Supported Runtimes

| Runtime | Status | |---------|--------| | TypeScript / JavaScript | Supported | | Docker | Supported | | Python | Not yet supported | | Java | Not yet supported |

Comparison with SST v2

This project provides similar live Lambda development capabilities to SST v2's Live Lambda Dev, but with a key difference: cdk-local-lambda works with vanilla CDK.

SST v2 requires adopting SST's stack conventions and constructs. With cdk-local-lambda, you keep your existing CDK code as-is—just add the bootstrap import and apply the aspect.

Prerequisites

• Node.js 24 or later

Installation

npm install cdk-local-lambda

Quick Start

Setting up local Lambda development requires three steps:

1. Load the bootstrap module
2. Apply the LiveLambda aspect
3. Start the local daemon

1. Load the bootstrap module

The bootstrap module patches CDK internals to enable local execution. The loading method depends on your runtime.

tsx / ts-node

In your CDK app entry point (e.g., bin/app.ts), import the bootstrap module before any other imports:

import "cdk-local-lambda/bootstrap" // Must be first import!
import * as cdk from "aws-cdk-lib"

Bun

Bun requires preloading the bootstrap module because it snapshots CommonJS exports during static ESM import linking. A regular import statement runs too late.

Add the --preload flag to your cdk.json:

{
  "app": "bun --preload cdk-local-lambda/bootstrap bin/app.ts"
}

2. Apply the LiveLambda aspect

In your CDK app entry point (e.g., bin/app.ts), apply the aspect after defining your stacks:

import "cdk-local-lambda/bootstrap" // Must be first import!
import * as cdk from "aws-cdk-lib"
import { applyLiveLambdaAspect } from "cdk-local-lambda"

const app = new cdk.App()
const stack = new MyStack(app, "MyStack")

applyLiveLambdaAspect(app)

app.synth()

3. Start the local daemon

The daemon deploys your stack with live mode enabled and runs Lambda functions locally:

npx cll local

For multiple stacks, specify which one to use:

npx cll local --stacks MyStack

When ready, you'll see:

[15:09:16.979] INFO: [Local] Starting local Lambda development...
[15:09:19.747] INFO: [CDK] Deploying...
[15:09:19.757] INFO: [Local] Press Ctrl+C to stop
[15:09:25.870] INFO: [CDK] Deploy complete
[15:09:26.878] INFO: [Local] Discovering functions...
[15:09:30.837] INFO: [Local] Functions: JsCalculatorBD1C3822 (node), DockerAdder757B287D (docker), TsGreeter58FA51CD (node)
[15:09:30.841] INFO: [Local] Ready for invocations

Now invoke your Lambda normally via the AWS CLI or SDK:

aws lambda invoke --function-name MyStack-TsGreeter58FA51CD-EiQlVgIoZhz4 \
  --payload '{"name": "World"}' \
  --cli-binary-format raw-in-base64-out \
  /dev/stdout

{"message":"Hello, World!","timestamp":"2026-02-02T02:10:11.920Z"}

The local console shows each invocation with any console.log output from your function:

[1] ┌── MyStack-TsGreeter58FA51CD-EiQlVgIoZhz4 ──
[1] [Greeter] Received greeting request for: World
[1] └── ✓ Done (892ms) ──

Manual bootstrap (optional)

To deploy the bootstrap stack separately:

npx cll bootstrap --profile my-profile --region us-west-2

Options

Conditional Configuration

Use isInLocalMode() to conditionally configure your constructs when running locally:

import { isInLocalMode } from "cdk-local-lambda"

new lambda.Function(this, "MyFunction", {
  // Longer timeout for local debugging
  timeout: isInLocalMode()
    ? cdk.Duration.minutes(5)
    : cdk.Duration.seconds(30),
  // ... other props
})

Credentials

Run daemon with a specific credential and region:

npx cll local --stacks MyStack --profile my-profile --region us-west-2

Troubleshooting

"No functions found with live-lambda tags yet"

This error appears when the bootstrap module or aspect is not configured correctly.

Checklist:

• Verify that cdk-local-lambda/bootstrap is loaded (use --preload for Bun)
• Confirm that applyLiveLambdaAspect(app) is called in your app entry point
• Ensure the aspect is applied after all stacks are defined