Fastify 5.12.6 release notes, 13 Oct 2026

[Backport 5.x] types: restrict route lookup methods by @github-actions[bot] in https://github.com/fastify/fastify/pull/7048
[Backport 5.x] perf: decode string bodies once instead of per chunk by @github-actions[bot] in https://github.com/fastify/fastify/pull/7053
[Backport 5.x] perf: avoid resetting the level of request child loggers by @github-actions[bot] in https://github.com/fastify/fastify/pull/7058
[Backport 5.x] fix: resolve reply.mediaType from raw response headers by @github-actions[bot] in https://github.com/fastify/fastify/pull/7067
[Backport 5.x] perf: use a FIFO cache for parsed content-types by @github-actions[bot] in https://github.com/fastify/fastify/pull/7072
[Backport 5.x] fix(validation): lowercase header names in propertyNames enum/const by @mcollina in https://github.com/fastify/fastify/pull/7104
[Backport 5.x] fix: copy a set-cookie array passed to reply.header instead of storing it by @github-actions[bot] in https://github.com/fastify/fastify/pull/7087
[Backport 5.x] fix: remove error when HTTP QUERY request has empty body by @github-actions[bot] in https://github.com/fastify/fastify/pull/7060
[Backport 5.x] docs: document fastify.query() shorthand for RFC 10008 by @github-actions[bot] in https://github.com/fastify/fastify/pull/7094

Full Changelog: https://github.com/fastify/fastify/compare/v5.12.5...v5.12.6