Symfony's official LSP server was mostly written by Claude and GPT, and Potencier said so.

Symfony Language Tools adds Symfony-aware completion, hover, navigation, references, rename, diagnostics, quick fixes, and code lenses across PHP, Twig, and YAML, shipping as a native VS Code extension with Neovim support, alongside rather than replacing existing PHP language servers. Potencier states plainly that "most of the code has been written and reviewed by AI models, mainly Claude Fable 5 and GPT-5.6 Sol," with him owning architecture, scope, and final say. Extensive test suite, benchmarks, and a test matrix covering every *.symfony.com site. A rare public accounting of AI-authored code in a framework's official tooling, from a maintainer with nothing to prove.