lsp

Language Server Protocol (LSP) is a protocol for communication between a text editor or integrated development environment (IDE) and a language server that provides language features such as code completion, go-to-definition, hover information, and diagnostics. By standardizing the interface, editors can support multiple languages using the same tooling, while language servers can be reused across editors.

LSP uses JSON-RPC over a channel such as standard input/output, TCP, or WebSocket. The client initializes a session with an initialize request, after which the server declares its capabilities (for example, text document synchronization, completion, hover, and formatting). As the user edits a document, the client sends didOpen, didChange, and related notifications; the server responds with responses or emits asynchronous messages with results such as completion items, definitions, or diagnostics.

Architecturally, the client and server are separate processes. The client is responsible for presenting results in the UI and for managing documents, while the server analyzes source code and provides language-aware tooling. The protocol supports features including code actions, symbol discovery, semantic tokens, and refactoring helpers, depending on the server's capabilities and the editor's interface.

History and ecosystem: LSP was introduced by Microsoft in 2016 to enable consistent language tooling across editors; it has since evolved and is maintained by the language tooling community. Dozens of language servers exist for languages such as Python, JavaScript/TypeScript, Java, C/C++, Rust, Go, and many others; major editors and IDEs—including VS Code, Neovim, Sublime Text, and Eclipse Theia—offer LSP support, typically via client libraries or built-in integrations.

Impact and considerations: LSP reduces the need for language-specific editor plug-ins by enabling reusable servers, fostering interoperability and faster tooling development. Potential drawbacks include additional network or inter-process overhead, latency for large projects, and the challenge of maintaining consistent feature parity across editors and servers.