pi-diet-lsp

One of my diet context engineering and workflow extensions. Explore the complete collection: https://www.npmjs.com/~probabilityengineer

On-demand LSP code-intelligence tools for Pi without automatic diagnostics or context injection.

pi-diet-lsp gives Pi agents focused, model-visible Language Server Protocol tools for definitions, references, symbols, hover/type information, and diagnostics. It keeps the surface compact and explicit: no automatic diagnostics pipeline, no context injection, no read guard, no skills, and no session-start bootstrap. Agents call the tools when precise code intelligence is useful.

This is intentionally different from automatic LSP feedback extensions: pi-diet-lsp favors low prompt overhead and explicit tool calls over continuously appending diagnostics to every edit.

Tools

• lsp_definition — jump to definition at a 1-based file position
• lsp_references — find references at a 1-based file position
• lsp_symbols — document symbols for a file, or workspace symbols by query
• lsp_hover — show hover/type info at a 1-based file position
• lsp_diagnostics — open a file in LSP and return current diagnostics

lsp_symbols has two modes:

{ "filePath": "src/index.ts", "query": "optional-filter" }
{ "query": "SymbolName" }

With filePath, it returns document symbols. Without filePath, it uses LSP workspace symbol search.

Large symbol/reference results are compacted and capped to avoid runaway context growth.

Use /lsp to toggle pi-diet-lsp tools, and /lsp-footer to toggle the footer entry. Both commands are toggle-only and take no arguments.

Install

From npm, after publication:

pi install npm:pi-diet-lsp

From GitHub:

pi install git:github.com/ProbabilityEngineer/pi-diet-lsp

For project-local install, add -l:

pi install -l git:github.com/ProbabilityEngineer/pi-diet-lsp

For local testing:

pi -e ./index.ts

Runtime requirements

LSP tools resolve language servers from PATH using broader built-in defaults and first-available selection when multiple servers are supported. Configured command values may also be absolute executable paths (with arguments supplied separately in args); absolute paths are checked directly, independently of PATH.

Availability checks require a regular file (or a symlink to one) and execute access on POSIX systems, so directories and non-executable files are skipped. These checks do not guarantee successful startup: interpreters, shared libraries, runtime configuration, and Windows executable-format restrictions can still prevent launch.

Current built-in mappings include:

• TypeScript/JavaScript: typescript-language-server --stdio
• Vue: vue-language-server --stdio
• Python: basedpyright-langserver --stdio, fallback pyright-langserver --stdio
• Go: gopls
• Rust: rust-analyzer
• Swift: sourcekit-lsp
• C/C++: clangd
• C#: csharp-ls, fallback omnisharp --languageserver
• Java: jdtls
• Kotlin: kotlin-language-server
• PHP: intelephense --stdio, fallback phpactor language-server
• Ruby: ruby-lsp, fallback solargraph stdio
• Lua: lua-language-server
• Nix: nixd, fallback nil
• HTML: vscode-html-language-server --stdio
• CSS/SCSS/Less: vscode-css-language-server --stdio
• JSON: vscode-json-language-server --stdio
• YAML: yaml-language-server --stdio

Configuration overrides

You can override or add language mappings with:

~/.pi/agent/pi-diet-lsp/config.json

Example:

{
  "showStatus": false,
  "languages": {
    "lua_override": {
      "languageId": "lua",
      "extensions": [".lua"],
      "servers": [
        { "command": "custom-lua-lsp", "args": ["--stdio"] }
      ]
    }
  }
}

Configured languages are checked before built-in defaults.

You can also provide per-server environment variables, which is especially useful for OmniSharp:

{
  "languages": {
    "csharp_override": {
      "languageId": "csharp",
      "extensions": [".cs"],
      "servers": [
        {
          "command": "omnisharp",
          "args": ["--languageserver"],
          "env": {
            "DOTNET_ROOT": "/Users/you/.dotnet"
          }
        }
      ]
    }
  }
}

C# notes and troubleshooting

• pi-diet-lsp prefers csharp-ls first, then falls back to omnisharp.
• The selected executable must be runnable from PATH, or configured with an absolute executable path. It is launched directly, without an interactive shell.
• For OmniSharp, pi-diet-lsp now auto-uses ~/.dotnet as DOTNET_ROOT when present. If your setup differs, set env.DOTNET_ROOT in config.
• Legacy .NET Framework projects may still load with partial diagnostics on macOS/Linux if reference assemblies/targeting packs are unavailable.
• If a server fails to launch, tool errors now include launch details and stderr instead of only reporting an initialize timeout.

Validation

npm run lint
npm run test:resolution

Prompt overhead

pi-diet-lsp avoids automatic context injection. It registers compact tools and guidance, then waits for agents to call LSP tools explicitly when code intelligence is relevant.

Guidance covers only this extension's LSP tools; it does not assume other extensions are installed.