`devbox shell` command fails on x86_64-darwin: "nixpkgs 26.11 has dropped support for x86_64-darwin"

[udnp]

What happened?

On x86_64-darwin, devbox shell fails in both existing projects and newly initialized ones. It fails even when packages is empty, so Devbox is currently unusable on this platform.

devbox shell
Info: Ensuring packages are installed.
✓ Computed the Devbox environment.
Error: nix: command error: nix --extra-experimental-features ca-derivations --option experimental-features 'nix-command flakes fetch-closure' print-dev-env --json path:~/ws/nix-fix-x86darwin/.devbox/gen/flake: Nixpkgs 26.11 has dropped support for x86_64-darwin.: exit code 1

The generated .devbox/gen/flake/flake.nix pins a nixpkgs revision from the
26.11 line, which no longer supports this platform:

{
   description = "A devbox shell";

   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/38a4887411571457d700c51c64a6e49ead2ed5ab?narHash=sha256-kh35kIx7el4Jk8Ki3BH9%2FPn1eZYSYLJ6LMALos0zOy0%3D";
   };

   outputs = {
     self,
     nixpkgs,
   }:
      let
        pkgs = nixpkgs.legacyPackages.x86_64-darwin;
      in
      {
        devShells.x86_64-darwin.default = pkgs.mkShell {
          buildInputs = [
          ];
        };
      };
 }

As a local workaround, adding "nixpkgs.commit": "329c3d2af6d1b618705150ea39f72c15eb4e613e" that indicates current nixpkgs-26.05-darwin branch to the devbox.json.

{
   "$schema": "https://raw.githubusercontent.com/jetify-com/devbox/0.17.5/.schema/devbox.schema.json",
   "packages": [],
   "shell": {
     "init_hook": [
       "echo 'Welcome to devbox!' > /dev/null"
     ],
     "scripts": {
       "test": [
         "echo \"Error: no test specified\" && exit 1"
       ]
     }
+  },
+  "nixpkgs": {
+    "commit": "329c3d2af6d1b618705150ea39f72c15eb4e613e"
   }
 }

.devbox/gen/flake/flake.nix generated from the devbox.json above

{
   description = "A devbox shell";

   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/329c3d2af6d1b618705150ea39f72c15eb4e613e";
   };

   outputs = {
     self,
     nixpkgs,
   }:
      let
        pkgs = nixpkgs.legacyPackages.x86_64-darwin;
      in
      {
        devShells.x86_64-darwin.default = pkgs.mkShell {
          buildInputs = [
          ];
        };
      };
 }

Could Devbox select a nixpkgs-26.05-darwin revision for x86_64-darwin, so that existing projects keep working without each user pinning nixpkgs.commit by hand?
Nixpkgs 26.05 is supported until the end of 2026, so this would cover the remaining lifetime of the platform.

See:
https://github.com/NixOS/nixpkgs/blob/38a4887411571457d700c51c64a6e49ead2ed5ab/doc/release-notes/rl-2611.section.md

Steps to reproduce

1. devbox init on x86_64-darwin system.
2. devbox shell

Command

shell

devbox.json

Devbox version

0.17.5

Nix version

No response

What system does this bug occur on?

macOS (Intel)

Debug logs

No response