Netlify Functions lambda-compat-2026-09-04

Last reviewed Sep 20, 2026

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  1. Netlify Functions lambda-compat-2026-09-04150 lines · 6.1K tokens

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Prompt Preview

Use these rules only for Netlify Functions in the deprecated Lambda compatibility mode: JavaScript or TypeScript functions with a named handler(event, context) export and Go functions built on the AWS Lambda handler API. This deprecated line remains deployable until its announced retirement deadlines below. The modern web-standard Netlify Functions API, including default-exported withLambda() wrappers, is a separate runtime boundary.

Legacy boundary and retirement

  • Identify JavaScript and TypeScript compatibility functions by their named handler export, including stream(), schedule(), and builder() wrappers; identify Go functions by lambda.Start() and the events.APIGatewayProxyRequest / APIGatewayProxyResponse contract.
  • Inspect the Netlify build log after function bundling, because it lists remaining compatibility-mode functions and whether each came from the repository, a build plugin, or a framework adapter.
  • Treat 2027-06-01 as the operational deadline for new legacy deploys: Netlify's detailed announcement names that earlier date even though the compatibility reference currently says 2027-07-01, and obtain current Netlify confirmation before relying on the later date.
  • Migrate every deployed legacy function well before 2027-12-31, when Netlify says already-deployed compatibility-mode functions will stop being invoked and return errors.
  • Prefer the modern API for new work and give each remaining legacy function a migration date and tested replacement; do not plan a rollback that depends on invoking the retired runtime.
  • For JavaScript or