LangChain.js now supports running on browsers, Cloudflare Workers, Vercel/Next.js, Deno, and Supabase Edge Functions, in addition to existing support for Node.js ESM and CJS. The library has been reworked to better support optional dependencies and produce smaller bundles. Breaking changes include moving certain imports to more granular locations. Testing is conducted using a test-exports package for each new environment, with the option for users to contribute additional environments through pull requests.