# ERROR: Could not build wheels for foo, which is required to install pyproject.toml-based projects

- **ID:** `python/pip-missing-build-backend`
- **Domain:** python
- **Category:** install_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

A package using PEP 517 build system failed to produce a wheel, typically due to missing C compiler, headers, or build dependencies.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.x | active | — | — |

## Workarounds

1. **** (90% success)
   ```
   On Debian/Ubuntu: `sudo apt-get install build-essential python3-dev`. On macOS: `xcode-select --install`. Then retry `pip install foo`.
   ```
2. **** (80% success)
   ```
   `pip install --only-binary=:all: foo` or fetch a manylinux wheel from PyPI/conda-forge.
   ```

## Dead Ends

- **** — Upgrading pip does not provide the missing system toolchain. (85% fail)
- **** — Disabling build isolation can help only if build deps are preinstalled; usually they are not. (70% fail)