codex-lsp-mcp

codex-lsp-mcp is a local MCP stdio server that exposes read-only LSP navigation tools to Codex.

Built-in defaults target clangd for C/C++ and pyright for Python; additional LSP backends can be configured in ~/.config/codex-lsp-mcp/config.toml.

Quick start

Run the published package from PyPI:

uvx codex-lsp-mcp

Local development

uv run pytest
uvx --from . codex-lsp-mcp

Codex configuration

codex mcp add codex-lsp-mcp -- uvx codex-lsp-mcp

Check registration:

codex mcp get codex-lsp-mcp

If clangd is not on Codex's PATH, set:

[mcp_servers.codex-lsp-mcp.env]
CLANGD_BIN = "/path/to/clangd"

For Python navigation, ensure pyright-langserver is on Codex's PATH. If pyright is installed in a non-standard location, override the built-in backend in ~/.config/codex-lsp-mcp/config.toml:

[servers.pyright]
command = "/home/miot/.local/share/nvim/mason/bin/pyright-langserver"
args = ["--stdio"]
root_markers = [["pyrightconfig.json"], ["pyproject.toml"], ["setup.py"], ["setup.cfg"], ["requirements.txt"], ["Pipfile"], ["poetry.lock"], [".git", ".repo"]]
workspace_hint_extension = ".py"

[servers.pyright.extension_to_language]
".py" = "python"

The server discovers the closest compile_commands.json from the queried file path.

Tool coordinates follow the LSP convention: zero-based line and character.

Workspace roots

File-oriented tools (definition, references, hover, diagnostics, and document_symbols) accept an optional root_hint argument. Use it when file is relative or when the MCP server process is not running from the project root:

{
  "file": "miio_test/cli.py",
  "line": 86,
  "character": 18,
  "root_hint": "/home/miot/Work/miot/tool/miio_test"
}

Absolute file paths are not rewritten by root_hint, but the hint is still used as the fallback workspace root when no server-specific root marker is found. Server-specific markers still take precedence, such as compile_commands.json for clangd and pyproject.toml for pyright.

workspace_symbols already accepts root_hint and can also take server_name when a directory is ambiguous across multiple configured LSP backends.