Hi! I'm one of the authors of Dart Code Metrics, and we use analyzer plugin API (like sending AnalysisErrorFixes, etc.) to communicate with the analysis server. If I enable LSP preview in VSCode and have the plugin enabled, VSCode starts to display diagnostics without quick fixes. For example,

It works fine when LSP preview is disabled.

Could there be a problem with the analysis server?

Dart SDK version: 2.14.0-301.2.beta (beta) (Mon Jul 19 23:53:21 2021 +0200) on "macos_x64"
VSCode version: 1.58.0
Dart extension version: 3.24.2