nixos/modules/system/boot/loader/grub/grub.nix: fails to honor boot.kernelParams

Nixpkgs version

• Unstable (25.11)

Describe the bug

When using the GRUB bootloader, boot.kernelParams is ignored. This makes it very difficult to use a serial console.

Steps to reproduce

Set boot.kernelParams = [ "console=ttyS0" ] and boot.loader.grub.enable = true.

Expected behaviour

console=ttyS0 added to kernel command line.

Screenshots

No response

Relevant log output

Additional context

This makes it very hard to use serial consoles provided by recovery environments, such as serial-over-LAN.

System metadata

system: "x86_64-linux", multi-user?: yes, version: nix-env (Nix) 2.31.2, channels(root): "nixos, nixpkgs", nixpkgs: /nix/store/nwkl6qniwivgslnp5mg4mj1m0aagpm25-nixos/nixos

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Start in nixos/modules/system/boot/loader/grub/grub.nix and inspect how boot.loader.grub.enable handles boot.kernelParams. Reproduce with boot.kernelParams = [ "console=ttyS0" ] and GRUB enabled, then verify that console=ttyS0 appears on the kernel command line.