Reproducible Python project contract

First classify the repository:

Project	Build system	Installation expectation
Application/non-package	Usually none; optionally tool.uv.package = false	Sync dependencies, do not invent a distributable package.
Library/package	Explicit [build-system] and package layout	Build and inspect wheel plus sdist.
Workspace	Root membership plus member metadata	One shared lock; run member-specific commands deliberately.

Workflow

1. Inspect existing pyproject.toml, uv.lock, Python constraint, source layout, build backend, dependency groups/extras, tool configuration, CI, and current commands before changing anything.
2. Preserve the declared project type. Do not add a build system merely to make an application look like a package.
3. Put runtime dependencies in [project.dependencies], optional consumer features in [project.optional-dependencies], and development tools in [dependency-groups]. Keep environment markers explicit.
4. Use uv add/remove or an intentional metadata edit followed by uv lock. Commit uv.lock for reproducible projects; never edit it manually.
5. Use uv sync for an exact project environment and uv run for commands. In CI or verification, use --locked so stale metadata fails rather than silently updating the lock.
6. Configure one canonical quality pipeline: Ruff check and format, Pyright, pytest, and build inspection when the project is distributable.
7. For a package, run uv build, inspect sdist/wheel contents and metadata, install the wheel into a clean environment, then import and exercise its public entry point.

Invariants

• pyproject.toml declares intent; uv.lock records resolution; .venv is generated state and is not committed.
• A passing editable install is not proof that the built wheel contains the package or data files.
• Extras are consumer-selectable features; dependency groups are development or task environments. Do not use one as the other.
• Never invoke publishing or handle registry tokens without explicit authority.
• Preview uv features and tool schemas are version-sensitive; inspect installed help and current official docs before encoding them.

uv lock --check
uv sync --locked
uv run --locked ruff check .
uv run --locked ruff format --check .
uv run --locked pyright
uv run --locked pytest
uv build

Use project and dependency layout, quality and build verification, and migration safeguards.