Base environment has no site packages directory

Error message

Base environment has no site packages directory

What it means

Error "Base environment has no site packages directory" thrown in astral-sh/uv.

Source

Thrown at crates/uv/src/commands/project/run.rs:1086

    // `--with` requirements environment and the project environment site packages.
    //
    // Setting `PYTHONPATH` is insufficient, as it doesn't resolve `.pth` files in the base
    // environment. Adding `sitecustomize.py` would be an alternative, but it can be shadowed by an
    // existing such module in the python installation.
    if let Some(ephemeral_env) = ephemeral_env.as_ref() {
        if let Some(requirements_env) = requirements_env.as_ref() {
            let requirements_site_packages =
                requirements_env.site_packages().next().ok_or_else(|| {
                    anyhow!("Requirements environment has no site packages directory")
                })?;
            let mut base_site_packages = base_interpreter
                .runtime_site_packages()
                .iter()
                .map(|path| Cow::Borrowed(path.as_path()))
                .chain(base_interpreter.site_packages())
                .peekable();
            if base_site_packages.peek().is_none() {
                return Err(anyhow!("Base environment has no site packages directory"));
            }

            let overlay_content = format!(
                "import site; {}",
                std::iter::once(requirements_site_packages)
                    .chain(base_site_packages)
                    .dedup()
                    .inspect(|path| debug!("Adding `{}` to site packages", path.display()))
                    .map(|path| format!("site.addsitedir({})", path.escape_for_python()))
                    .collect::<Vec<_>>()
                    .join("; ")
            );

            ephemeral_env.set_overlay(overlay_content)?;

            // N.B. The order here matters — earlier interpreters take precedence over the
            // later ones.
            for interpreter in [requirements_env.interpreter(), &base_interpreter] {

View on GitHub (pinned to f1a42680ff)

When it happens

Trigger: Thrown at crates/uv/src/commands/project/run.rs:1086 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of astral-sh/uv@f1a42680ff (2026-08-16). Data as JSON: /api/errors/ee5bf247fb2abdb8. Report an issue: GitHub.