Bash tool breaks on NixOS with version >=1.0.49

[CircuitCoder]

Describe the bug

Bash tool breaks on NixOS when updated to version >=1.0.49 (also present on 1.0.50). When the agent tries to run any command, it errors with:

<exited with error: Failed to start bash process>

Running copilot-cli with strace -f gives the following output:

[pid  2803] execve("/bin/bash", ["/bin/bash", "--norc", "--noprofile"], 0x5480bd70 /* 75 vars */ <unfinished ...>

This seems to be the only relevant syscall related to the tool call.

NixOS does not have /bin/bash, only /bin/sh.

Affected version

GitHub Copilot CLI 1.0.50.

Steps to reproduce the behavior

1. Start a session, tell the agent to run anything in a shell.

Expected behavior

1. The command gets executed.

Additional context

No response

[linus-entiros]

I have the same issue. Here is more context/temporary fix.

Bash on NixOS is (by default) accessible from:
/etc/profiles/per-user/<USERNAME>/bin/bash

Also via PATH. It is not available at /bin/bash

Fix while we wait for official bufix is to add envfs to your configuration.nix:
services.envfs.enable = true;

[me-and]

Notably this isn't a problem if you're using WSL with https://github.com/nix-community/NixOS-WSL, as that has code to make sure /bin/bash always exists: https://github.com/nix-community/NixOS-WSL/blob/5482f113fd31ebac131d1ebeb2ae90bf0d5e41f5/modules/wsl-distro.nix#L204-L213

My Nix configuration now patches in the correct path to Bash in my build of github-copilot-cli. You can't invoke it directly (I want nix run github:me-and/nixcfg#github-copilot-cli-universal to work, but it's currently broken), but if you're building the package yourself and/or can add an overlay to Nixpkgs' github-copilot-cli packgae, you might be able to emulate this patch: https://github.com/me-and/nixcfg/blob/44b83a4773a25b02d30026bed3bb4a97908ca692/pkgs/github-copilot-cli-universal.nix#L33-L40

[NobbZ]

This is a problem on any distro, FHS compliant or not, that decides to not provide /bin/bash, but maybe /usr/bin/bash instead.

Any programs location should always be resolved through the PATH mechanism. And if that is not possible, then a configuration mechanism should be used to allow users to override the defaults.

Software should never expect any given path to exist at any time.

[Xophmeister]

Still reproduces on 1.0.61 (nixpkgs build). Confirmed in-source, not just via strace: lib/github-copilot-cli/app.js (and sdk/index.js) hardcode the PTY executable as let d = c ? u : "/bin/bash" and spawn it directly, bypassing PATH. Notably the Nix wrapper already prepends a valid bash-interactive/bin to PATH, so simply resolving bash via PATH (or honouring $SHELL/a config override) would fix this for all non-FHS distros.