Flaky: Namespace macOS arm64 Nix store invalid path

namespace-nix-store-flake.md

Flaky CI failure on Namespace macOS arm64 runners: invalid Nix store paths

Summary

We are seeing an intermittent CI failure on Namespace-managed GitHub Actions runners (macOS arm64) where Nix evaluation fails because the runner's /nix/store appears internally inconsistent (store DB references paths that don't exist).

This is not a flaky unit/integration test: the failure happens before our actual tests run.

Symptoms

• Job: test (namespace-profile-macos-arm64)
• Fails during Nix/devenv evaluation (before vitest starts)
• Error signature (key line):

error: path '/nix/store/...-make-symlinks-relative.sh' is not valid

The error is emitted while evaluating bootstrap-stage0-stdenv-darwin (Darwin stdenv bootstrap), which suggests missing store paths.

We also see downstream/secondary errors like:

• Failed to convert config.cachix to JSON
• Evaluation error: Failed to get attribute 'package' while evaluating cachix.package

Those look like consequences of the earlier invalid store path.

Evidence (public)

Example failing runs in a public repo:

• 2026-02-12: https://github.com/overengineeringstudio/effect-utils/actions/runs/21937239839
  • failing job: test (namespace-profile-macos-arm64)
• 2026-02-09: https://github.com/overengineeringstudio/effect-utils/actions/runs/21840384378
  • failing job: test (namespace-profile-macos-arm64)

Internal tracking issue (what we collect when it happens again):

• overengineeringstudio/effect-utils#201

Upstream issue filed for Namespace:

• namespacelabs/nscloud-setup#8

Runner details

In the failing run logs (linked above), GitHub Actions prints Namespace runner details:

• OS: macOS
• Architecture: arm64
• A "User Bundled Cache" is enabled

We suspect this may involve persisted runner state / bundled cache restoring a broken Nix store state.

What would help

Questions for Namespace maintainers / runners team:

1. Are there known issues on macOS Namespace runners where /nix/store can become inconsistent (missing paths)?
2. Is there a supported way to force a clean Nix store (or disable store persistence) for a runner profile?
3. If the bundled cache can become corrupted, is there a supported mechanism to invalidate/reset it automatically?

Notes

• This is flaky and we do not have a reliable reproduction.
• We are improving CI logging so that future failures include more actionable Nix store verification output.