AWS Lambda adds public preview runtimes with Node.js 26 and Python 3.15

AWS Lambda's new public preview runtimes address a recurring developer pain point: waiting for AWS to certify a language version long after its upstream release. By letting teams run Node.js 26 and Python 3.15 in a preview state before general availability, AWS lets developers validate compatibility early and feed issues back to shape the runtime before it's locked as GA.

The mechanism is a formalized preview channel — a supported-but-non-GA runtime tier with an explicit feedback loop — rather than the previous all-or-nothing model where a runtime was either GA or unavailable. It's a modest but practically useful change for teams that track upstream language features closely and want to test performance and behavior on Lambda ahead of production commitment.

The move sits within a busy AWS week: 41 announcements including Aurora serverless faster scaling for agentic workloads, Managed Dashboards for Billing, and DNS-based domain validation in Certificate Manager, all against a backdrop of Amazon lifting 2026 capex guidance to $220 billion tied to component costs and AI infrastructure. Competitively, preview runtimes narrow a gap where developers sometimes reached for containers or other clouds to get newer language versions. Watch whether the feedback channel meaningfully improves GA runtime quality or becomes a perpetual-preview holding pattern.