Matt Leon upgraded core WebAssembly runtime dependencies for the envoyproxy/envoy repository, focusing on improving compatibility, security, and maintainability of the WebAssembly execution environment. He updated proxy_wasm_cpp_host, wasmtime, and wamr to their latest versions, ensuring the runtime could support newer wasm modules and reducing long-term maintenance risks. Using Bazel for build systems and leveraging his experience with CI/CD and dependency management, Matt maintained end-to-end traceability through detailed commits and pull requests. His work included updating dependency manifests and release notes, providing a robust foundation for future WebAssembly ecosystem updates while demonstrating depth in C++, Go, and Python.