Toby Zhang focused on reliability and performance improvements in JVM-based projects, addressing complex issues in both the TencentKona-11 and SAP/SapMachine repositories. He enhanced test automation stability by reconfiguring the Java test runner to prevent timeouts in the JstackTestStoppedThread, improving CI feedback and reducing triage time. In SAP/SapMachine, Toby corrected G1 garbage collector boundary calculations for UseCompressedOops, aligning them with ergonomic heap region sizing and adding automated regression tests to ensure correctness across configurations. His work leveraged deep knowledge of Java, C++, and JVM internals, demonstrating careful attention to correctness and maintainability in performance tuning and software testing.