[ncaq]

Upstream ComfyUI calls Python 3.13 "very well supported" and ships it in its portable builds,
and it is the default Python of nixpkgs.
Linux moves from 3.12 to 3.13.
macOS stays on 3.12,
because the pinned PyTorch 2.5.1 has no cp313 wheel for macOS.
The interpreter is now selected in one place,
nix/python.nix.

Interpreter-specific wheel pins in nix/versions.nix become a URL template,
with one hash per interpreter tag.
nix/python-overrides.nix derives the tag from the selected Python,
so the next bump only has to add hashes.
A new wheel-pins check fails evaluation when a pin lacks the hash for the selected Python.

The launcher derives the venv paths from the interpreter instead of hardcoding python3.12.
It rewrites pyvenv.cfg and the interpreter links on every start,
since both name a store path that changes with each update.
It also prints a note when site-packages of another Python version are left in the venv,
because packages installed by ComfyUI-Manager under 3.12 are not visible to 3.13.

The bundled PyAV wheel goes from 17.0.0 to 17.0.1.
With 17.0.0 on Python 3.13,
imageio's test_lagging_video_stream hangs and fails the build every time.

Overrides that Linux no longer needs on nixpkgs' default Python are reduced.
On Linux the affected packages now come from the binary cache,
or build with their test suites enabled.

• macOS only, grouped in one block: open-clip-torch, torchmetrics, inline-snapshot, backrefs
• macOS only, same block: jupyter-server, ultralytics, mss, filterpy
• Only where PyTorch comes from a pre-built wheel: timm, torchsde
• Removed: albumentations, which nixpkgs dropped
• Removed: bitsandbytes, which nixpkgs already builds with ninja
• Removed: allowBrokenPredicate for open-clip-torch, which is no longer marked broken

Tested on x86_64-linux with an RTX 5090.

• nix flake check passes, building the CPU, CUDA, ROCm 7.1 and XPU packages
• The ROCm 7.2 package builds
• The CUDA package starts and loads all bundled custom nodes
• It registers the same 1693 nodes as the 3.12 build
• A model-free workflow that saves PNG and h264 output succeeds

macOS is only verified to evaluate.
The PyAV bump and the allowBrokenPredicate removal also affect it.

[Copilot]

🟡 Changes recommended

The manual-linting heading in CLAUDE.md is joined to the wheel-pins bullet, making the manual commands appear to belong to the CI-check list.

1 open issue

• Restore line break before manual linting heading · New

What changed in this PR

Moves Linux builds to Python 3.13 while keeping macOS on Python 3.12 for compatibility with its pinned PyTorch wheels.

Changes:

• Centralizes interpreter selection and adds interpreter-specific wheel hashes with an evaluation check.
• Updates launcher virtual-environment paths and interpreter links, with guidance for reinstalling older dependencies.
• Upgrades PyAV to 17.0.1 and narrows package overrides that Linux no longer needs.

File	Description
README.md	Updates the documented Python versions.
pyproject.toml	Updates the project description to Python 3.13.
nix/​versions.nix	Adds wheel URL templates and Python 3.13 hashes.
nix/​python.nix	Centralizes platform-specific interpreter selection.
nix/​python-overrides.nix	Resolves wheel pins, upgrades PyAV, and narrows overrides.
nix/​packages.nix	Adapts the launcher and virtual environment to the selected Python.
nix/​checks.nix	Adds wheel-hash validation and adjusts the mss assertion.
flake.nix	Uses shared interpreter selection and removes obsolete broken-package allowances.
CLAUDE.md	Documents interpreter selection and the wheel-pin check.
CHANGELOG.md	Records the migration and dependency changes.

_{Review effort: Balanced}

[Copilot]

🔵 Needs a closer look

The PyAV update and override changes still require a native macOS build and import smoke test against the retained Python 3.12 runtime and pinned PyTorch 2.5.1 stack.

No open issues 🎉

1 resolved since last review

• Restore line break before manual linting heading

_{Review effort: Balanced}