# ERROR: Invalid pyproject.toml config: `project`. configuration error: `project.version` must be a string, was `float`

- **ID:** `python/pip-install-invalid-pyproject-toml`
- **Domain:** python
- **Category:** config_error
- **Verification:** ai_generated
- **Fix Rate:** 80%

## Root Cause

TOML parses `version = 1.0` as a float, but PEP 621 requires the version field to be a string.

## Version Compatibility

| Version | Status | Introduced | Deprecated |
|---------|--------|------------|------------|
| 3.11 | active | — | — |
| 3.12 | active | — | — |
| 3.13 | active | — | — |

## Workarounds

1. **** (97% success)
   ```
   Quote the version in pyproject.toml: `version = "1.0"` (or use dynamic version via setuptools_scm).
   ```
2. **** (94% success)
   ```
   Validate before building: `python -c "import tomllib,pathlib; print(tomllib.loads(pathlib.Path('pyproject.toml').read_text())['project']['version'])"`.
   ```

## Dead Ends

- **** — The pyproject.toml validation happens before build isolation settings matter. (90% fail)
- **** — Newer setuptools enforces the same PEP 621 type rules; the error persists. (85% fail)