Codemode Lsp

codemode-lsp

Semantic code intelligence and refactoring for TypeScript/JavaScript agents: an MCP server exposing a single execute tool backed by the language server. The LLM writes one JavaScript script that chains semantic operations (lsp.*) — filtering, looping, and aggregating in code instead of across many tool-call round trips:

const refs = await lsp.findReferences("src/api.ts", "handleRequest");
const relevant = refs.filter((r) => r.context.includes("deprecated"));
for (const ref of relevant) {
  await lsp.replaceSymbolBody(ref.file, ref.symbolPath, newImpl);
}
({ modified: relevant.length });

It shines on codebase-wide work that grep-based agents get subtly wrong: impact analysis, call graphs, usage audits, and atomic multi-file refactors. Names are resolved, not text-matched. Writes are transactional — nothing hits disk unless the whole script succeeds, and successful writes come back as reviewable unified diffs.

Setup

No install step — the package bundles its own typescript-language-server. The workspace root is the directory the server is spawned from:

{
  "mcpServers": {
    "codemode-lsp": {
      "command": "npx",
      "args": ["-y", "codemode-lsp"]
    }
  }
}

Add "env": { "CODEMODE_READONLY": "1" } to try it on a repo it physically cannot write to.

Operations

The tool returns { result, logs, changes }. Symbols are addressed as (file, "MyClass/myMethod") pairs discovered via getSymbols. When a script does something a cheaper call covers, the result (and logs) carries an advisory [hint]. Full type definitions are embedded in the tool description (generated from source); if a client truncates it, await lsp.help() returns the complete reference and await lsp.docs("query") returns just the matching op signatures, related types, and a worked example.

See PRD.md for the complete spec and decision log.

Configuration

Limitations

• TypeScript/JavaScript only (the architecture is language-agnostic).
• Per-file diagnostics cover session-touched files; checkProject() is the whole-project check. On files created mid-script, per-file "Cannot find module" alias errors are tagged likelyFalsePositive: true — checkProject() has no such false positives.
• getDependencies is syntactic; moveSymbol moves top-level symbols only.
• Reference.isWriteAccess is always false (not exposed over standard LSP).

Development

bun run check           # typecheck + lint + all tests — run before declaring done
bun run generate:types  # regenerate src/lsp-types.generated.ts after API changes
bun run eval            # LLM benchmark: headless Claude Code, execute tool only

The tool description's worked examples run verbatim as golden tests, and every eval task's reference solution runs in the normal suite — neither can rot.