- - Fastify v4 introduces breaking changes: drops Node 12 support, removes flatstrt, deprecates the variadic listen method, changes default reply.sent handling and content‑type coercion for streams, among other API adjustments.
- - Adds major new features such as Type Providers and typed decorators, default exposeHeadRoutes = true, async handlers resolving undefined, reply trailers support, AJV 8 as the default validator, and enhanced error handling/encapsulation.
- - Includes extensive documentation updates, dependency upgrades, CI/benchmark improvements, and numerous bug‑fixes and minor enhancements.
v4.0.0
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Fix for two Fastify security advisories (GHSA‑w2qp‑rph6‑63g4 and GHSA‑3m5p‑2c4r‑xxw2).
Added per‑route logging for Google Cloud Functions and introduced `Reply.prototype.mediaType` for easier content‑type handling.
Fixed trailer state clearing when removing all trailers and corrected requestCompleted handling to use null instead of undefined.