Grzegorz Kossakowski
Company Owner at Thing In Itself
San Francisco, California, United States
Summary
🤩
Rockstar🎓
Top SchoolGrzegorz Kossakowski is a seasoned software engineer and founder with 19 years of experience building compilers, developer tooling, and AI-first products from San Francisco. He combines deep compiler and Scala expertise—contributing to scala/scala, sbt, and Typelevel projects—with product and AI leadership roles at Stripe and his own ventures. Known for practical, hands-on work, he led developer productivity and early AI initiatives at Stripe and later founded AI-focused startups and a consultancy, Thing In Itself. His open-source contributions reveal a focus on incremental compilation, dependency tracking, and cross-version Scala compatibility, reflecting a mix of low-level systems thinking and developer ergonomics. He writes about software, AI, and product and takes a pragmatic view learned from a startup that was “2–4 years too early” to market.
19 years of coding experience
4 years of employment as a software developer
Masters mathematics computer science, Masters mathematics computer science at University of WarsawMaster thesis DSLs programming techniques, Master thesis DSLs programming techniques at EPFL
Github Skills (34)
reflection10
restructuredtext10
jvm10
compile-time10
testing10
macros10
sbt10
build-system10
incremental-compiler10
development-tools10
devtools10
scala10
incremental-builds10
compile10
scala-compiler10
Programming languages (11)
Github contributions (5)
sbt/sbt
Nov 2012 - May 2016
sbt, the interactive build tool
Role in this project:
Back-end Developer
Back-end DeveloperContributions:386 commits, 8 PRs, 1 push in 3 years 6 months
Contributions summary:Grzegorz made several contributions related to the internal workings of the sbt build tool, focusing on incremental compilation and dependency tracking. They added functionality to enhance the incremental compiler by introducing options and improving the logging of changes. Their work involved adding support for features like name hashing to improve the precision of dependency analysis, and they also refactored code for greater modularity and maintainability within the compiler. Furthermore, the user addressed bugs related to class file management and dependency resolution, improving the reliability of the build process.
zincsbt-pluginscalasbtbuild-tool
scala/scala
Sep 2011 - Apr 2015
Scala 2 compiler and standard library. Scala 2 bugs at https://github.com/scala/bug; Scala 3 at https://github.com/scala/scala3
Role in this project:Backend Developer & Compiler Engineer
Backend Developer & Compiler EngineerContributions:461 commits, 28 PRs, 26 pushes in 3 years 7 months
Contributions summary:Grzegorz made several contributions focused on improving the Scala compiler and standard library. The contributions included fixing bugs in Char constant printing, optimizing the Iterator class by removing structural types, removing unused imports, and addressing issues related to handling inner classes in the JVM backend. Additionally, they worked on compiler phase management, improved pattern matching and switches and also on making sure the specialized flag is being pickled.
functional-programmingobject-oriented-programmingscala-libraryscala-programming-languagestandard-library
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