Interrupted long-running build prints a crash report instead of exiting cleanly

[schickling-assistant]

Summary

When a long-running Determinate Nix build is interrupted, nix prints a crash banner and stack trace instead of treating the interrupt as a normal user cancellation.

I hit this while verifying a Home Manager config, but the bug appears to be the interrupt handling/reporting path itself, not the specific derivation.

Environment

• Determinate Nix: nix (Determinate Nix 3.17.0) 2.33.3
• macOS: 26.2 (25C56)
• Host: mbp2025
• Architecture: arm64

Command

home-manager switch --flake .#mbp2025 --no-write-lock-file

This delegated to:

nix build .#homeConfigurations."mbp2025".activationPackage --out-link /var/folders/.../generation --no-write-lock-file

Repro Shape

I can reproduce the failure mode with a long-running build in a PTY-backed session:

1. Start a long-running nix build / home-manager switch
2. Interrupt the build
3. Determinate Nix prints a crash report

In my case the build was in:

building '/nix/store/anwmra3n5jp0zhb8qykdrv7marny6f12-grafana-dashboard-modules-root.drv'...

Actual Behavior

Instead of cleanly reporting interruption, Determinate Nix emits:

error: interrupted by the user
Determinate Nix crashed. This is a bug. Please report this at https://github.com/DeterminateSystems/nix-src/issues with the following information included:

Exception: nix::Interrupted: error: interrupted by the user
Stack trace:
 0# nix::(anonymous namespace)::onTerminate() in /nix/store/w75hyfqa1p3vy04x8zn4237pqgqfwicp-determinate-nix-3.17.0/bin/nix
 1# std::__terminate(void (*)()) in /nix/store/sg5gfy9cj0991jbd4xfyrl21rmqib9r2-libcxx-19.1.7/lib/libc++abi.1.0.dylib
 2# __cxa_rethrow in /nix/store/sg5gfy9cj0991jbd4xfyrl21rmqib9r2-libcxx-19.1.7/lib/libc++abi.1.0.dylib
 3# nix::ignoreExceptionExceptInterrupt(nix::Verbosity) in /nix/store/lg8s87vqpmigbgpkm7f7g549k946lqfa-determinate-nix-util-3.17.0/lib/libnixutil.2.33.3.dylib
 4# nix::JSONLogger::write(...) in /nix/store/lg8s87vqpmigbgpkm7f7g549k946lqfa-determinate-nix-util-3.17.0/lib/libnixutil.2.33.3.dylib
 5# nix::JSONLogger::logEI(...) in /nix/store/lg8s87vqpmigbgpkm7f7g549k946lqfa-determinate-nix-util-3.17.0/lib/libnixutil.2.33.3.dylib
 6# nix::TeeLogger::logEI(...) in /nix/store/lg8s87vqpmigbgpkm7f7g549k946lqfa-determinate-nix-util-3.17.0/lib/libnixutil.2.33.3.dylib
 7# nix::handleExceptions(...) in /nix/store/yijfh1mylylgbs1j7sp35n517wf7ccfc-determinate-nix-main-3.17.0/lib/libnixmain.2.33.3.dylib
 8# main in /nix/store/w75hyfqa1p3vy04x8zn4237pqgqfwicp-determinate-nix-3.17.0/bin/nix

Expected Behavior

A user interrupt should be handled as a normal cancellation path:

• print error: interrupted by the user or similar
• exit cleanly
• do not print Determinate Nix crashed. This is a bug.
• do not emit a crash-style stack trace for an ordinary interrupt

Notes

I am not claiming the underlying build should have succeeded. The bug report is specifically about Determinate Nix treating an interrupt as an internal crash condition.