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The Nix sandbox is a hidden input

The article reveals that Nix's sandbox-paths configuration is a hidden input to derivations that isn't captured in the derivation hash, potentially breaking reproducibility. The author demonstrates this with a practical example where the presence or absence of /truth in the sandbox changes the build output, yet the derivation hash remains identical.

Background

Nix is a functional package manager and build system that achieves reproducibility through content-addressed store paths. The sandbox restricts what files a build can access, but its configuration is not part of the derivation hash by default.

Source
Lobsters
Published
Aug 4, 2026 at 09:02 PM
Score
6.0 / 10