Mikhail Filippov contributed to JetBrains repositories such as intellij-community, kotlin-lsp, and resharper-unity by modernizing build systems, improving test infrastructure, and enhancing plugin reliability. He upgraded Kotlin versions, migrated compiler artifacts to Bazel, and refactored initialization logic to streamline Bazel-based development. Using Kotlin, Java, and C#, Mikhail addressed memory leaks in test suites, modularized Groovy templates for better maintainability, and fixed resource path issues in Rider’s Unity plugin. His work focused on build automation, dependency management, and CI/CD, resulting in faster builds, safer test execution, and more robust cross-repo tooling, demonstrating depth in backend and plugin development.