chore(aquamarine): use NixOS's NPU module with nixos-unstable-small (#527)

* chore(aquamarine): take the NPU stack from nixos-unstable-small
* refactor(aquamarine): load the NPU driver via hardware.cpu.intel.npu

Assisted-by: DeepSeek Harness (claude-opus-5-5)

docs/WORKAROUNDS.md

@@ -17,13 +17,13 @@ obsolete workarounds get rolled back instead of lingering.
 A version or revision pinned for a reason that can go away.
 
 | ID     | What & where                                                                                                                                                                                                                                                                                                                                 | Why                                                                                                                                                                             | Removal condition                                                                                              | Added      | Revisit                               | Status |
-| ------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------- | ---------- | -------------------------- | ------ |
+| ------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------------------- | ---------- | ------------------------------------- | ------ |
 | WA-004 | `catppuccin` on `main` — `flake.nix`                                                                                                                                                                                                                                                                                                         | `main` carries the nodejs→nodejs-slim deprecation fix, which is not in a release                                                                                                | Switch to a release tag once it includes the fix                                                               | 2026-09-25 | on catppuccin release                 | active |
 | WA-006 | `nixpkgs-blender` — `flake.nix`                                                                                                                                                                                                                                                                                                              | Blender 5.2 LTS + CUDA/OptiX pin; keeps `just up` from triggering a full source rebuild                                                                                         | Bump deliberately when needed; drop the pin if the current nixpkgs build is acceptable                         | 2026-07-24 | deliberate                            | active |
 | WA-020 | `fcitx5-vinput` pinned to release tag `v2.4.2` — `flake.nix`; consumer `home/linux/gui/base/vinput/default.nix`                                                                                                                                                                                                                              | Tracks a release tag instead of a branch, so `just up` stays on that release                                                                                                    | Bump to a newer release tag when its changes are wanted                                                        | 2026-10-04 | on vinput release                     | active |
 | WA-021 | `nix-x86-on-aarch64` input — our fork of rowanG077's patched FEX + muvm runtime — `flake.nix`; `hosts/12kingdoms-shoukei/game/`                                                                                                                                                                                                              | FEX does not support 16K pages, so x86/x86_64 apps and games on shoukei need this pinned flake's 4K-page microVM runtime; our fork lets upstream changes be reviewed before use | Drop once FEX supports 16K pages directly, or nixpkgs/nixos-apple-silicon ships an equivalent runtime          | 2026-10-07 | on FEX/nixpkgs/muvm update            | active |
 | WA-023 | `nix.package = pkgs.nixVersions.latest` — `modules/nixos/base/nix.nix`                                                                                                                                                                                                                                                                       | NixOS is opted into Nix 2.35 (2.35.3), which nixpkgs ships as `nixVersions.latest`, while `nixVersions.stable` is still 2.34 (2.34.9)                                           | Drop the override and fall back to the default `pkgs.nix` once `nixVersions.stable` is 2.35 or newer           | 2026-10-07 | eval warning                          | active |
-| WA-037 | `nixpkgs-npu` input pinned to `2ddccb854d89` — the `openvino-npu-compiler` branch of `ryan4yin/nixpkgs`, carrying [NixOS/nixpkgs#570230](https://github.com/NixOS/nixpkgs/pull/570230) — `flake.nix`; consumer `pkgs-npu` in `outputs/default.nix`, `hosts/idols-aquamarine/asr.nix` | The Intel NPU compiler, and the driver change that loads it, are unmerged, so the NPU driver the Whisper service needs comes from that branch                                   | Drop the input and load `intel-npu-driver` from `nixos-unstable` once #570230 merges                  | 2026-10-17 | when #570230 merges        | active |
+| WA-037 | `nixpkgs-small` input on `nixos-unstable-small`, which carries [NixOS/nixpkgs#570230](https://github.com/NixOS/nixpkgs/pull/570230) — `flake.nix`; consumer `pkgs-small` in `outputs/default.nix`, the `intel-npu-driver` overlay in `hosts/idols-aquamarine/hardware-intel-cpu.nix`, and the Python env in `hosts/idols-aquamarine/asr.nix` | The Intel NPU compiler, and the driver change that loads it, are not in `nixos-unstable` yet; `openvino-genai` 2026.4.0.0 failed to build there                                 | Drop the overlay once #570230 reaches `nixos-unstable`; drop the input once `openvino-genai` also builds there | 2026-10-17 | when #570230 reaches `nixos-unstable` | active |
 
 ## Workarounds
 

flake.lock

@@ -676,22 +676,6 @@
         "type": "github"
       }
     },
-    "nixpkgs-npu": {
-      "locked": {
-        "lastModified": 1792250783,
-        "narHash": "sha256-J/gNk34hn774ccDrvJuSWW9EFLvIvyy3t4HnuTcN4tU=",
-        "owner": "ryan4yin",
-        "repo": "nixpkgs",
-        "rev": "2ddccb854d89eb027e09198368073fdb9cde4d1d",
-        "type": "github"
-      },
-      "original": {
-        "owner": "ryan4yin",
-        "ref": "openvino-npu-compiler",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "nixpkgs-patched": {
       "locked": {
         "lastModified": 1793459509,
@@ -708,6 +692,22 @@
         "type": "github"
       }
     },
+    "nixpkgs-small": {
+      "locked": {
+        "lastModified": 1794378162,
+        "narHash": "sha256-gJGP/BWdmF1pbjAzbuICPSeGkMncAiDt9PRe7L13664=",
+        "owner": "nixos",
+        "repo": "nixpkgs",
+        "rev": "c24da8b1d51f447e8faedcb5cb823b3f84346a60",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nixos",
+        "ref": "nixos-unstable-small",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
     "nixpkgs-stable": {
       "locked": {
         "lastModified": 1793183032,
@@ -896,8 +896,8 @@
         "nixpkgs-blender": "nixpkgs-blender",
         "nixpkgs-darwin": "nixpkgs-darwin",
         "nixpkgs-master": "nixpkgs-master",
-        "nixpkgs-npu": "nixpkgs-npu",
         "nixpkgs-patched": "nixpkgs-patched",
+        "nixpkgs-small": "nixpkgs-small",
         "nixpkgs-stable": "nixpkgs-stable",
         "nu_scripts": "nu_scripts",
         "nur-ryan4yin": "nur-ryan4yin",

flake.nix

@@ -32,10 +32,9 @@
     nixpkgs-patched.url = "github:ryan4yin/nixpkgs/nixos-unstable-patched";
     # get some latest packages from the master branch
     nixpkgs-master.url = "github:nixos/nixpkgs/master";
-    # ryan4yin/nixpkgs branch carrying NixOS/nixpkgs#570230 (the Intel NPU
+    # Ahead of nixos-unstable for aquamarine's NPU stack, through `pkgs-small`;
-    # compiler and the driver change that loads it). Only aquamarine consumes it,
+    # removal condition in docs/WORKAROUNDS.md WA-037.
-    # through `pkgs-npu`; drop it once the PR merges.
+    nixpkgs-small.url = "github:nixos/nixpkgs/nixos-unstable-small";
-    nixpkgs-npu.url = "github:ryan4yin/nixpkgs/openvino-npu-compiler";
     # NixOS MicroVMs -- run the VMs directly on the hosts, replacing the former KubeVirt
     microvm = {
       url = "github:microvm-nix/microvm.nix";

hosts/idols-aquamarine/asr.nix

@@ -3,7 +3,7 @@
   mylib,
   myvars,
   pkgs,
-  pkgs-npu,
+  pkgs-small,
   ...
 }:
 let
@@ -52,9 +52,9 @@ let
   '';
 
   # openvino-genai 2026.4.0.0 fails to compile against the OpenVINO headers in
-  # nixos-unstable (no matching constructor in continuous_batching); the branch's
+  # nixos-unstable (no matching constructor in continuous_batching); the
-  # nixpkgs builds it, and the service has to match the NPU stack anyway.
+  # service takes it from the same nixpkgs as the NPU stack.
-  pythonEnv = pkgs-npu.python3.withPackages (ps: [
+  pythonEnv = pkgs-small.python3.withPackages (ps: [
     ps.fastapi
     ps.numpy
     ps.openvino-genai
@@ -90,9 +90,6 @@ in
       # Python block-buffers stdout when it is not a tty, which would hold the
       # request log lines back instead of putting them in the journal.
       PYTHONUNBUFFERED = "1";
-      # The stock driver cannot find the NPU compiler; the patched one loads it
-      # from its own store path.
-      ZE_ENABLE_ALT_DRIVERS = "${lib.getLib pkgs-npu.intel-npu-driver}/lib/libze_intel_npu.so";
     };
 
     # Reads its model, writes its cache, uses the NPU and listens on the LAN.

hosts/idols-aquamarine/default.nix

@@ -1,8 +1,6 @@
 {
   disko,
   myvars,
-  lib,
-  pkgs-npu,
   ...
 }:
 #############################################################
@@ -71,13 +69,6 @@ in
   # profile's rootless Podman (modules/nixos/agent.nix), built from the `~/src`
   # checkout that ./preservation.nix keeps.
 
-  # Speech recognition runs on the NPU, see ./asr.nix. The driver and the
-  # compiler it loads come from NixOS/nixpkgs#570230, which is unmerged, so they
-  # are taken from that branch as `pkgs-npu`; the stock driver cannot find the
-  # compiler, the patched one loads it from its own store path. The service sets
-  # this itself -- the session variable is for manual runs.
-  environment.sessionVariables.ZE_ENABLE_ALT_DRIVERS = "${lib.getLib pkgs-npu.intel-npu-driver}/lib/libze_intel_npu.so";
-
   # The daemons of the hosts that build here (modules/nixos/base/remote-builders.nix).
   # Their host keys have no passphrase, so they only get the daemon protocol, as
   # nix.sshServe does. `--store daemon` hands builds to the system daemon instead

hosts/idols-aquamarine/hardware-intel-cpu.nix

@@ -1,8 +1,14 @@
 {
   pkgs,
+  pkgs-small,
   ...
 }:
 {
+  # The NPU serves ./asr.nix; the driver's compiler lookup is fixed by
+  # NixOS/nixpkgs#570230, which reached nixos-unstable-small first (WA-037).
+  hardware.cpu.intel.npu.enable = true;
+  nixpkgs.overlays = [ (_: _: { inherit (pkgs-small) intel-npu-driver; }) ];
+
   # Ad-hoc CPU idle-power diagnostics: package power, C-state residency and
   # wakeup attribution. Long-term RAPL export lives in the shared
   # modules/nixos/base/power-monitoring.nix module.

outputs/default.nix

@@ -61,7 +61,7 @@ let
         # to use chrome, we need to allow the installation of non-free software
         config.allowUnfree = true;
       };
-      pkgs-npu = import inputs.nixpkgs-npu {
+      pkgs-small = import inputs.nixpkgs-small {
         inherit system;
         config.allowUnfree = true;
       };