fix: mock CUDA virtual package in GPU-less CI for pixi >= 0.76 - #4
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pixi 0.76 introduced a build dispatch machine check when solving pypi requirements: the current machine must satisfy the workspace's system-requirements. GPU-less GitHub runners cannot provide __cuda >= 12.6, so every ubuntu pixi job started failing with 'build dispatch initialization failed: the workspace does not support linux-64 on this machine'. Set CONDA_OVERRIDE_CUDA (pixi's documented mechanism for mocking missing virtual packages) in the template repo CI and in the generated projects' CI/test workflows for pixi. The generated workflows derive the CUDA version from the selected pytorch_cuda_preset (or the custom cuda_version answer). Verified in a linux/amd64 container with pixi 0.76.1: 'pixi lock' reproduces the CI failure without the override and succeeds with it, for both the plain and PyTorch Geometric configurations. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
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Summary
Fixes the CI failures on all
ubuntu-latestpixi jobs (build dispatch initialization failed: the workspace does not support 'linux-64' on this machine).Root cause
CI installs the latest pixi. pixi 0.76 added a build-dispatch machine check when solving PyPI requirements: the current machine must now satisfy the workspace's
system-requirements(previously advisory). GPU-less GitHub runners cannot provide__cuda >= 12.6, sopixi install/pixi lockfails before solving. macOS jobs pass because the cuda requirement doesn't apply toosx-arm64. Unrelated to #3 — this is pixi version drift (last green run was 2026-05-18).Fix
Set
CONDA_OVERRIDE_CUDA— pixi's documented mechanism for mocking missing virtual packages (it's literally what pixi's error help suggests) — in:.github/workflows/test-template.yml(workflow-level, matches the matrix presets' CUDA 12.6)ci.yml.jinja/test.yml.jinjafor pixi projects, deriving the version frompytorch_cuda_preset(or the customcuda_versionanswer)Verification
linux/amd64container with pixi 0.76.1;pixi locksucceeds with the override for both plain and PyG configurations"13.0"), pixi custom (cuda_version=12.8→"12.8"), uv (no env block)Follow-up (out of scope)
pixi 0.76 also deprecates
[tool.pixi.system-requirements]in favor of per-platform declarations (platforms = [{ platform = "linux-64", cuda = "12.6" }]). Currently only a warning; worth migrating in a separate PR.🤖 Generated with Claude Code