Four JEPs targeting JDK 27 entered or concluded review on May 19, 2026. JEP 523 proposes making G1 the default garbage collector across all JVM environments, removing the current split where G1 is default only for server-class machines. JEP 534 graduates compact object headers from experimental to the default memory layout, reducing object overhead. JEP 537 advances the Vector API into its 12th incubator iteration with additional runtime optimizations, while JEP 538 introduces a new standard API for PEM encoding and decoding of cryptographic keys, certificates, and certificate revocation lists. For teams targeting JDK 27, JEP 523 and JEP 534 are the most operationally relevant: both are default-on changes that could alter GC tuning assumptions and heap profiling baselines. JEP 538 fills a long-standing gap where PEM handling required third-party libraries. The Vector API remains incubating and is not yet API-stable, but the continued iteration signals a path to standardization. Additionally, the macOS/x64 port enters maintenance-end status with JDK 27, meaning teams on that platform should plan migration to macOS/aarch64 or alternate targets.