oraios/serena · error · RuntimeError

Nix is required for nixd. Please install Nix from https://ni

Error message

Nix is required for nixd. Please install Nix from https://nixos.org/download.html

What it means

_get_or_install_core_dependency for nixd first requires the Nix package manager itself (checked via shutil.which("nix")), because nixd is installed through Nix when missing. If the `nix` binary is absent, RuntimeError is raised pointing to the Nix download page.

Source

Thrown at src/solidlsp/language_servers/nixd_ls.py:116

                    if result.returncode == 0:
                        nixd_path = shutil.which("nixd")
                        if nixd_path:
                            log.info("Successfully installed nixd at: %s", nixd_path)
                            return nixd_path
                    log.error("Failed to install nixd: %s", result.stderr)

            except subprocess.TimeoutExpired:
                log.error("Nix install timed out after 10 minutes")
            except Exception:
                log.exception("Error installing nixd with nix")

            return None

        def _get_or_install_core_dependency(self) -> str:
            """Return a working nixd path, installing nixd when necessary."""
            if not shutil.which("nix"):
                log.error("Nix is not installed. nixd requires Nix to function properly.")
                raise RuntimeError("Nix is required for nixd. Please install Nix from https://nixos.org/download.html")

            nixd_path = self._get_nixd_path()
            if not nixd_path:
                log.info("nixd not found. Attempting to install...")
                nixd_path = self._install_nixd_with_nix()

            if not nixd_path:
                raise RuntimeError(
                    "nixd (Nix Language Server) is not installed.\n"
                    "Please install nixd using one of the following methods:\n"
                    "  - Using Nix flakes: nix profile install github:nix-community/nixd\n"
                    "  - From nixpkgs: nix-env -iA nixpkgs.nixd\n"
                    "  - On macOS with Homebrew: brew install nixd\n\n"
                    "After installation, make sure 'nixd' is in your PATH."
                )

            try:
                result = subprocess_run([nixd_path, "--version"], capture_output=True, text=True, check=False, timeout=5)

View on GitHub (pinned to 7fcbca7e62)

Solutions

Install Nix from https://nixos.org/download.html and restart the shell.
Alternatively install the nixd binary directly (brew install nixd, nix profile install github:nix-community/nixd) so the Nix-based install path is skipped.
Ensure the nix binary location (e.g. /nix/var/nix/profiles/default/bin) is on PATH in non-interactive shells/CI.

Defensive patterns

Strategy: validation

Validate before calling

import shutil
if not shutil.which("nix"):
    raise SystemExit("Install Nix first: https://nixos.org/download.html")

Try / catch

try:
    server = NixdLanguageServer(...)
except RuntimeError as e:
    if "Nix is required" in str(e):
        install_nix()  # or preinstall nixd binary
    else:
        raise

Prevention

Install Nix on all dev machines and CI images using nixd.
Or preinstall the nixd binary (brew/nix profile) so Nix itself is not needed at install time.
Ensure /nix/var/nix/profiles/default/bin is on PATH in non-interactive shells.

When it happens

Trigger: Initializing the nixd language server on a machine where `nix` is not on PATH and nixd itself is not already installed (so the Nix-based installer path is taken).

Common situations: Developers on macOS/Windows/WSL without Nix; CI images without the Nix package manager; nix installed only in a user profile not on PATH.

Related errors

AI-assisted analysis of oraios/serena@7fcbca7e62 (2026-08-29). Data as JSON: /api/errors/9ffda2f4951f7cd9. Report an issue: GitHub.