The language server toolkit

One engine.
Every surface.

Write your language analysis once, as one Rust trait. lspkit serves it to your VS Code extension over the Language Server Protocol and to Claude Code, Cursor and Codex as an MCP server. Find the hot path and the memory leak with a profiler built into VS Code.

Get started

See it running.

SharpLsp and Osprey ship the lspkit profiler in VS Code today: hot lines in the source, a flame graph beside it, and ranked memory leak suspects. See both examples.

SharpLsp · C# and F# language server for VS Code ↗SharpLsp profiling a real .NET app in VS Code. Watch the walkthrough ↗
CheckoutPipeline.cs with inline heat bars: ParseCatalog 66.8 percent, PriceBasket 25.1 percent, RenderInvoice 7.6 percent
SharpLsp · C# and F# language server for VS Code ↗Hot lines, painted in the source.
busy.osp in VS Code with inline heat bars: collatz 76.4 percent, longest 73.0 percent, fib 22.5 percent
Osprey · native functional language with a VS Code extension ↗Heat on Osprey source.
An orange engine connects through precise circuit paths to two dark terminal surfaces, representing LSP and MCP.
FIG. A — One engine, two surfaces.LSP / MCP / PROFILER

From the workbench.

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