feat: keep pi and nix features current

README.md

@@ -17,7 +17,7 @@ Flat, explicit NixOS modules, with locked inputs. Required machine setup belongs
 | `desktop.nix`, `hyprland.lua`, `anyrun.css`, `wallpaper.svg` | Hyprland/UWSM, bar, launcher, original wallpaper, notifications, lock/idle, PipeWire and desktop styling |
 | `apps.nix` | Firefox ESR, KeePassXC, Thunderbird, Steam, Element, Slack and Zathura |
 | `workstation.nix`, `nvidia.nix` | Separately selected physical-workstation/greeter and NVIDIA integration; not enabled on EC2 |
-| `updates.nix`, `update-system.sh` | Daily stable-input updates in an isolated Git worktree; validated commits, no forced reboot or GC |
+| `updates.nix`, `update-system.sh` | Daily package-input updates in an isolated Git worktree; validated commits, no forced reboot or GC |
 | `desktop-test.nix`, `desktop-test.py`, `audit-desktop.sh`, `update-test.py` | Disposable graphical audit and updater failure/concurrency tests |
 | `network.nix` | WireGuard/OpenVPN clients and network diagnostics; optional resolved, host-owned interface management |
 | `neovim.nix`, `neovim-test.lua` | Editor, unchanged upstream dotfile deployment and opt-in native runtime audit |
@@ -62,12 +62,12 @@ From an administrator shell:
 
 ```sh
 cd /etc/nix
-nix --extra-experimental-features 'nix-command flakes' flake check --no-build --no-update-lock-file
+nix flake check --no-build --no-update-lock-file
-nix --extra-experimental-features 'nix-command flakes' build \
+nix build \
   .#checks.x86_64-linux.physical-config \
   .#checks.x86_64-linux.updates .#checks.x86_64-linux.desktop-config \
   --no-update-lock-file --no-link
-nix --extra-experimental-features 'nix-command flakes' build \
+nix build \
   .#nixosConfigurations.nixos.config.system.build.toplevel \
   --no-update-lock-file --out-link result-nixos
 built=$(readlink -f result-nixos)
@@ -132,7 +132,7 @@ nix --extra-experimental-features 'nix-command flakes' build \
   .#nixosConfigurations.dev.config.system.build.toplevel --no-update-lock-file
 ```
 
-Then review/apply the resulting closure as above. The configuration creates `dev`, sets permissions and deploys its files. **No separate Neovim clone, copy, useradd, chown or global Git-config recipe is required.**
+Then review/apply the resulting closure as above. The configuration creates `dev`, sets permissions and deploys its files. **No separate Neovim clone, copy, useradd, chown or global Git-config recipe is required.** After either host configuration is active, `nix-command` and `flakes` are system defaults through `nix.settings.experimental-features`; the temporary flag is only for bootstrapping older bases that cannot read flakes yet.
 
 This host build does not use a mutable channel. NixOS's native flake integration pins the `nixpkgs` registry entry and login-shell `<nixpkgs>` lookup to the system input; the global `nix-path` setting keeps the same pin when `NIX_PATH` is unset. Old root channel profiles are retained for recovery, not used as build inputs. Dev-environment templates/composition remain deferred; there is no flake framework here.
 
@@ -159,8 +159,8 @@ Make focused changes, format/evaluate them, and commit regularly. Build and acti
 
 ## Updates and safety
 
-- **EC2 only:** `nixos-update.timer` checks daily with up to one hour of jitter. Only the stable Nixpkgs/Home Manager branches advance; Neovim's source stays fixed. The updater skips a dirty repository, builds in a detached worktree, records a tested commit and applies it without rebooting. It attempts rollback if activation fails and retains recovery generations. Inspect `journalctl -u nixos-update` or trigger it with `sudo systemctl start nixos-update`.
+- **EC2 only:** `nixos-update.timer` checks daily with up to one hour of jitter. Nixpkgs/Home Manager release branches and the latest developer-tool package input advance; Neovim's source stays fixed. The updater skips a dirty repository, builds in a detached worktree, records a tested commit and applies it without rebooting. It attempts rollback if activation fails and retains recovery generations. Inspect `journalctl -u nixos-update` or trigger it with `sudo systemctl start nixos-update`.
-- For a manual input refresh: `nix flake update nixpkgs home-manager`, review `flake.lock`, then check/build. The exact resolved revisions and hashes remain committed.
+- For a manual input refresh: `nix flake update nixpkgs home-manager nixpkgs-latest`, review `flake.lock`, then check/build. The exact resolved revisions and hashes remain committed.
 - Keep the EC2 module on the EC2 target only. Preserve sandboxing, signature verification and each host's recovery access.
 - `system.stateVersion` and `home.stateVersion` are both `26.05`; these preserve compatibility, not package versions.
 - `test` activates changes too; it is not a dry run. Keep the original system generation.

common.nix

@@ -11,6 +11,18 @@
   ];
 
   nixpkgs.hostPlatform = "x86_64-linux";
+  nixpkgs.overlays = [
+    (_final: prev: {
+      # Pi is a fast-moving agent harness; stable branches can be generations old.
+      # Use the latest resolving Nixpkgs input while keeping the rest of the
+      # system on the stable release branch.
+      pi-coding-agent =
+        (import inputs.nixpkgs-latest {
+          inherit (prev.stdenv.hostPlatform) system;
+          config = prev.config or { };
+        }).pi-coding-agent;
+    })
+  ];
 
   nix = {
     channel.enable = false;

flake.lock

@@ -55,11 +55,28 @@
         "type": "github"
       }
     },
+    "nixpkgs-latest": {
+      "locked": {
+        "lastModified": 1788659161,
+        "narHash": "sha256-rIzUUvgwhfJeWwm7y1ZF+xRo2Gep+QYkxpj9mJbG6cM=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "de0ba0a81b0f6eed798a97fdec6f03a754b9d966",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "master",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "root": {
       "inputs": {
         "home-manager": "home-manager",
         "neovim-dots": "neovim-dots",
-        "nixpkgs": "nixpkgs"
+        "nixpkgs": "nixpkgs",
+        "nixpkgs-latest": "nixpkgs-latest"
       }
     }
   },

flake.nix

@@ -10,6 +10,10 @@
       inputs.nixpkgs.follows = "nixpkgs";
     };
 
+    # Fast-moving developer tools can lag behind stable release branches.
+    # flake.lock still records the exact resolved snapshot.
+    nixpkgs-latest.url = "github:NixOS/nixpkgs/master";
+
     neovim-dots = {
       url = "git+https://git.cyber.ayyalasomayajula.net/marsultor/neovim-dots?ref=main&rev=380eb86778a7c53a0f1c18e84f14037456155347";
       flake = false;

tools.nix

@@ -11,6 +11,7 @@ in
 
   environment.systemPackages = with pkgs; [
     nixfmt
+    # Overridden in common.nix to stay current beyond stable release lag.
     pi-coding-agent
     # Runtime build prerequisites for the unchanged Lazy/Mason plugin workflow.
     gcc

update-system.sh

@@ -21,10 +21,10 @@ trap cleanup EXIT
 
 git worktree add --detach "$work" "$baseline"
 cd "$work"
-# Only these stable release inputs advance. Neovim's source stays pinned.
+# Advance package inputs to newest resolving branch heads. Neovim stays pinned.
-nix flake update nixpkgs home-manager
+nix flake update nixpkgs home-manager nixpkgs-latest
 if git diff --quiet -- flake.lock; then
-  echo 'Stable inputs are already current.'
+  echo 'Package inputs are already current.'
   exit 0
 fi
 nix flake check --no-build --no-update-lock-file
@@ -32,7 +32,7 @@ nix build .#checks.x86_64-linux.updates .#checks.x86_64-linux.desktop-config \
   --no-update-lock-file --no-link
 git add flake.lock
 git -c user.name='NixOS Updater' -c user.email='nixos-updater@localhost' \
-  commit -m 'chore: update stable NixOS and Home Manager inputs'
+  commit -m 'chore: update NixOS package inputs'
 built=$(nix build .#nixosConfigurations.dev.config.system.build.toplevel \
   --no-update-lock-file --no-link --print-out-paths)
 candidate=$(git rev-parse HEAD)

update-test.py

@@ -17,7 +17,7 @@ with open(os.environ["CALLS"], "a") as f:
     f.write(json.dumps([name, *args]) + "\n")
 if name == "nix":
     if args[:2] == ["flake", "update"]:
-        assert args[2:] == ["nixpkgs", "home-manager"]
+        assert args[2:] == ["nixpkgs", "home-manager", "nixpkgs-latest"]
         if scenario != "unchanged":
             pathlib.Path("flake.lock").write_text('{"revision":2}\n')
     elif args[:2] == ["flake", "check"]: