The MeTTa language server

MeTTa LSP is a TypeScript language server and VS Code extension for MeTTa. It reads your code the way the interpreter does and turns that understanding into editor features: hovers, go to definition, references, rename, completions, diagnostics, formatting, running, and visualising a reduction.

Runtime behavior comes from MeTTa TS. The LSP docs describe editor, CLI, MCP, diagnostics, and generated reference pages; for the runtime packages, TypeScript APIs, async host operations, and browser runner, see the MeTTa TS documentation.

What you get

• Rich hovers in the rust-analyzer style: a symbol's signature, its interpreter-exact type, where it is defined, and a link straight to its builtins reference entry.
• Run without the guard caps from the ▶ button or the run code lens. A run evaluates the whole file (or one bang query), and the results print to the MeTTa Run output channel in MeTTa syntax. Fuel and timeout are configurable; MeTTa's own pragma! governs the rest.
• Visualise the reduction as the interactive MeTTaGrapher, the same component this site embeds: step through it, switch between the graph and block views, and export the animation as a GIF.
• Python interop: when a program uses the py-atom family or py-call/py-eval, an unguarded run evaluates them against real CPython. Guarded evaluation never loads the bridge, so py atoms stay inert there by construction.
• Diagnostics with a full catalogue: every code links to a page explaining what it means and how to fix it, so you always see the whole message, not just the one line in the editor.
• Suggestions: a lightbulb offers to add a type declaration to an untyped function, because a declared type lets the interpreter dispatch by type instead of trying every rule.
• Pseudocode mode: a toggle that shows each top-level form's mixfix reading above it.

Settings

The status-bar button (or the command MeTTa: Settings) opens a quick-pick that toggles the common settings without leaving the editor: inlay hints, pseudocode mode, and the diagnostic groups. They are ordinary VS Code settings, so they also live in the Settings UI and sync across your machines.

metta.docs.baseUrl points the hover and diagnostic docs links at wherever this site is deployed. Set it to your deployment's URL and every "Open docs" link and diagnostic code resolves here.