Build Config Env Expansion - Pixi

!!! warning "Variable references are not expanded by pixi" Values are passed to the build shell unchanged, so a reference like $PREFIX is only resolved if that shell understands it. Linux and macOS builds run through bash, which expands $PREFIX. Windows builds run through cmd.exe, which expands %PREFIX% and leaves $PREFIX as literal text.

Use target-specific configuration when you need both:

```toml
[package.build.target.unix.config]
env = { MY_INCLUDE_DIR = "$PREFIX/include" }

[package.build.target.win.config]
env = { MY_INCLUDE_DIR = "%PREFIX%\\Library\\include" }
```

`${{ PREFIX }}` is not an alternative here.
Templates in `env` are rendered while the recipe is evaluated, which happens before the build prefix exists.
They only work in build scripts.