Local package randomly becomes unimportable when using `uv run` in a project created with `uv init --package`

I'm seeing non-deterministic import failures when using uv to manage a Python project created with "uv init --package". After a fresh "uv sync", my local package is importable, but after running a few "uv run" commands it suddenly becomes unimportable with:

ModuleNotFoundError: No module named 'tfm_rag_municipal'

No files or config change between runs. Recreating ".venv", deleting "uv.lock", and running "uv sync" fixes it temporarily — but the problem always returns.

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Project Setup

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Project created using:

uv init --package tfm-rag-municipal

Project structure (standard src layout):

tfm-rag-municipal/ pyproject.toml src/ tfm_rag_municipal/ __init__.py example.py corpus_audit/ __init__.py schema.py corpusrecord_example.py tests/ test_example.py

Example module:

def add(a: int, b: int) -> int: return a + b

Test:

from tfm_rag_municipal.example import add def test_add_basic(): assert add(2, 3) == 5

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pyproject.toml (relevant parts)

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[project] name = "tfm-rag-municipal" version = "0.1.0" requires-python = ">=3.12" dependencies = [] [project.scripts] tfm-rag-municipal = "tfm_rag_municipal:main" [project.optional-dependencies] dev = ["pytest", "ruff", "pre-commit"] [build-system] requires = ["uv_build>=0.9.15,<0.10.0"] build-backend = "uv_build"

uv sync reports:

+ tfm-rag-municipal==0.1.0 (from file:///.../tfm-rag-municipal)

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Minimal Reproducible Sequence

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Fresh reset:

rm -rf .venv uv.lock src/tfm_rag_municipal.egg-info uv sync

Everything works:

uv run python -c "import tfm_rag_municipal" uv run pytest uv run python -m tfm_rag_municipal.corpus_audit.corpusrecord_example

Then, after repeating:

uv run python -c "import tfm_rag_municipal" uv run python -c "import tfm_rag_municipal" uv run python -c "import tfm_rag_municipal"

Eventually:

ModuleNotFoundError: No module named 'tfm_rag_municipal'

No code or config changes occur.

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Environment

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macOS (M1) Python 3.12.7 (via pyenv) uv (latest version) Reproducible with or without VS Code running

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Things I've already checked

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init.py exists Not using pip manually Not modifying PYTHONPATH Issue appears in plain terminal Removing .venv + uv.lock always fixes it temporarily

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Question

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Why is uv intermittently losing access to my local package, and how can I prevent this?

Specific questions:

How can I ensure a local package created via "uv init --package" stays importable across uv run invocations? Is my pyproject.toml missing something required by uv or uv_build? Is this a known issue with uv + uv_build + src layout on macOS?

Any explanation or workaround would be greatly appreciated.