feat(pikachu): add initial NixOS host

.sops.yaml

@@ -7,6 +7,7 @@ keys:
   - &admin age1m0pk94ysjlw3lmf6pyuv5l5pepvdjss8w0vxjv90dq6ndp02tdgsdwdvue
   # Generated on the machine it names.
   - &neogaia age14a04vphzjq74epfrz9a09wjw8lzchtru84awzuq2n45d8f42ychqjs89qe
+  - &pikachu age1wf5s0n0tgt6ld2ysgu9dc67mj8ylwecgl4utzg7hqwy3kut9zyms7aglmh
 
 creation_rules:
   # Material belonging to one machine.
@@ -24,3 +25,4 @@ creation_rules:
       - age:
           - *admin
           - *neogaia
+          - *pikachu

AGENTS.md

@@ -20,6 +20,8 @@ The domain model (Host, Module, Skeleton, Auto-loader, Enable convention, overla
 
 - Subagent completion delivery is non-blocking through immediate spawn, milestone notifications, retained terminal entries, and `subagent_list` or `subagent_result` retrieval.
   `subagent_wait` intentionally blocks the parent tool call until its condition or timeout, so do not use it merely to keep background work alive during an interactive workflow.
+- Nixvim's flake input following the root nixpkgs source does not make its Home Manager module reuse the host's `pkgs` instance.
+  Keep `programs.nixvim.nixpkgs.useGlobalPackages = true` so Nixvim uses the shared package set without warning that its source default was affected.
 - This host has no `python` or `python3` command on its ordinary `PATH`.
   For ad hoc Python, use Nix explicitly, such as `nix shell nixpkgs#python3 -c python3 <script>`.
 - ADR bodies are immutable records of decisions as they were made, while frontmatter is mutable.

flake.lock

@@ -562,11 +562,11 @@
         ]
       },
       "locked": {
-        "lastModified": 1785622772,
-        "narHash": "sha256-0mOr+Jxerr4SU1ksLoSkztYlZ9P/nMB6RlgWygoCHWc=",
+        "lastModified": 1785695024,
+        "narHash": "sha256-DLLk6X5zu3cRT50p18uHVdwjGVtiS0t/661M34q02zU=",
         "ref": "refs/heads/main",
-        "rev": "40b16b87963b085817bfb82c26eef7d0408fa8a5",
-        "revCount": 52,
+        "rev": "9b2a6bcd583d7d6bf7e5377c3632f601692df209",
+        "revCount": 54,
         "type": "git",
         "url": "https://git.alexion.dev/alexion/skills"
       },

flake.nix

@@ -100,7 +100,11 @@
 
       # `nix flake check` builds each host's toplevel.
       checks.x86_64-linux = lib.mapAttrs (
-        _name: host: host.config.system.build.toplevel
+        name: host:
+        if host.config.warnings == [] then
+          host.config.system.build.toplevel
+        else
+          throw "Host ${name} has evaluation warnings:\n${lib.concatStringsSep "\n" host.config.warnings}"
       ) self.nixosConfigurations;
     };
 }

hosts/neogaia/default.nix

@@ -69,6 +69,7 @@
   modules.agents.tools.gitea-axi.enable = true;
   modules.agents.pi.enable = true;
   modules.agents.pi.subagents.maxConcurrent = 8;
+  modules.agents.pi.subagents.recentTerminalTtlMs = 15 * 60 * 1000;
 
   modules.desktop.enable = true;
   modules.desktop.obsidian.enable = true;

hosts/pikachu/default.nix

@@ -0,0 +1,58 @@
+{
+  config,
+  pkgs,
+  ...
+}:
+# pikachu — AZW ME Pro server.
+# Disk layout is in ./disk.nix.
+# `fileSystems` for the root disk are derived from it.
+{
+  imports = [
+    ./hardware-configuration.nix
+    ./disk.nix
+  ];
+
+  system.stateVersion = "26.05";
+
+  boot.loader.systemd-boot.enable = true;
+  boot.loader.efi.canTouchEfiVariables = true;
+
+  hardware.cpu.intel.updateMicrocode = true;
+  hardware.enableRedistributableFirmware = true;
+
+  zramSwap.enable = true;
+
+  systemd.network = {
+    enable = true;
+    networks."10-uplink" = {
+      matchConfig.MACAddress = "78:55:36:07:af:49";
+      networkConfig.DHCP = "yes";
+      linkConfig.RequiredForOnline = "routable";
+    };
+  };
+  networking.useDHCP = false;
+
+  boot.zfs.forceImportRoot = false;
+
+  modules.zfs = {
+    enable = true;
+    hostId = "2346edbd";
+    pools.pikachu = { };
+  };
+
+  modules.ssh.enable = true;
+  modules.ssh.hostKeys.restore = false;
+  modules.ssh.authorizedKeys = config.modules.ssh.workstationKeys;
+
+  modules.git.enable = true;
+  modules.toolkit.enable = true;
+
+  environment.systemPackages = with pkgs; [
+    pciutils
+    smartmontools
+    usbutils
+  ];
+
+  time.timeZone = "America/New_York";
+  i18n.defaultLocale = "en_GB.UTF-8";
+}

hosts/pikachu/disk.nix

@@ -0,0 +1,32 @@
+{ ... }:
+# pikachu's install layout for disko: one NVMe boot disk with an EFI system partition and ext4 root.
+# The existing 8 TB ZFS mirror is imported by name and is never declared here.
+{
+  disko.devices.disk.main = {
+    type = "disk";
+    device = "/dev/nvme0n1";
+    content = {
+      type = "gpt";
+      partitions = {
+        ESP = {
+          size = "2G";
+          type = "EF00";
+          content = {
+            type = "filesystem";
+            format = "vfat";
+            mountpoint = "/boot";
+            mountOptions = [ "umask=0077" ];
+          };
+        };
+        root = {
+          size = "100%";
+          content = {
+            type = "filesystem";
+            format = "ext4";
+            mountpoint = "/";
+          };
+        };
+      };
+    };
+  };
+}

hosts/pikachu/hardware-configuration.nix

@@ -0,0 +1,18 @@
+{ lib, modulesPath, ... }:
+# Hardware detected from the Proxmox inventory for this machine.
+# disko derives the root disk filesystems, none declared here.
+{
+  imports = [ (modulesPath + "/installer/scan/not-detected.nix") ];
+
+  boot.initrd.availableKernelModules = [
+    "ahci"
+    "nvme"
+    "sd_mod"
+    "xhci_pci"
+  ];
+  boot.initrd.kernelModules = [ ];
+  boot.kernelModules = [ "kvm-intel" ];
+  boot.extraModulePackages = [ ];
+
+  nixpkgs.hostPlatform = lib.mkDefault "x86_64-linux";
+}

modules/agents/pi/extensions/subagents/supervisor.test.ts

@@ -335,29 +335,31 @@ test("clearTerminal returns only removed terminal ids", async () => {
   assert.equal(supervisor.status(running.id).state, "running");
 });
 
-test("terminal records stay listed past ttl and remain retrievable until cleared", async () => {
+test("terminal records expire after ttl while active children remain", async () => {
   const runner = new FakeRunner();
   const supervisor = new Supervisor(runner, "/tmp", { recentTerminalTtlMs: 5 });
   const completed = await spawnStarted(supervisor, "one");
   const failed = await spawnStarted(supervisor, "two");
+  const running = await spawnStarted(supervisor, "three");
 
   runner.starts[0].events.completed("one done", "agent_settled");
   runner.starts[1].events.failed("two failed");
-  await sleep(10);
 
-  const listedIds = supervisor.list().map((status) => status.id);
-  assert.ok(listedIds.includes(completed.id));
-  assert.ok(listedIds.includes(failed.id));
   assert.equal(supervisor.result(completed.id).result, "one done");
   assert.equal(supervisor.result(failed.id).error, "two failed");
+  assert.equal(supervisor.status(running.id).state, "running");
 
-  (supervisor as Supervisor & { clearTerminal(): void }).clearTerminal();
+  await sleep(20);
 
-  const afterClearIds = supervisor.list().map((status) => status.id);
-  assert.equal(afterClearIds.includes(completed.id), false);
-  assert.equal(afterClearIds.includes(failed.id), false);
+  const listedIds = supervisor.list().map((status) => status.id);
+  assert.equal(listedIds.includes(completed.id), false);
+  assert.equal(listedIds.includes(failed.id), false);
+  assert.equal(listedIds.includes(running.id), true);
   assert.throws(() => supervisor.status(completed.id), /unknown subagent id/);
+  assert.throws(() => supervisor.status(failed.id), /unknown subagent id/);
+  assert.throws(() => supervisor.result(completed.id), /unknown subagent id/);
   assert.throws(() => supervisor.result(failed.id), /unknown subagent id/);
+  assert.equal(supervisor.status(running.id).state, "running");
 });
 
 test("zero recent terminal ttl does not hide terminal statuses", async () => {

modules/agents/pi/extensions/subagents/supervisor.ts

@@ -20,6 +20,7 @@ interface RunningChild {
   handle?: ChildHandle;
   startTimer?: ReturnType<typeof setTimeout>;
   runTimer?: ReturnType<typeof setTimeout>;
+  expiryTimer?: ReturnType<typeof setTimeout>;
 }
 
 interface SupervisorOptions {
@@ -99,6 +100,7 @@ export class Supervisor {
     for (const [id, child] of this.children) {
       if (selectedIds && !selectedIds.includes(id)) continue;
       if (!isTerminal(child.record.status.state)) continue;
+      this.clearTimer(child, "expiryTimer");
       cleared.push(id);
       this.children.delete(id);
     }
@@ -159,6 +161,7 @@ export class Supervisor {
         }
       }),
     );
+    for (const child of this.children.values()) this.clearTimer(child, "expiryTimer");
   }
 
   private createChild(request: SpawnRequest): SpawnAccepted {
@@ -250,7 +253,10 @@ export class Supervisor {
         this.recordActivity(record, "completed", now);
         record.status.stopReason = stopReason;
         record.status.resultAvailable = true;
-        if (child) this.emitMilestone(child, "completed");
+        if (child) {
+          this.armTerminalExpiry(child);
+          this.emitMilestone(child, "completed");
+        }
         this.pumpQueue();
       },
       failed: (error) => this.fail(record, error),
@@ -269,7 +275,10 @@ export class Supervisor {
     this.recordActivity(record, "failed", now);
     record.status.error = error;
     record.status.stopReason = "failed";
-    if (child) this.emitMilestone(child, "failed");
+    if (child) {
+      this.armTerminalExpiry(child);
+      this.emitMilestone(child, "failed");
+    }
     this.pumpQueue();
   }
 
@@ -283,6 +292,7 @@ export class Supervisor {
     child.record.status.lastEventAt = now;
     this.recordActivity(child.record, state, now);
     child.record.status.stopReason = reason;
+    this.armTerminalExpiry(child);
     this.emitMilestone(child, state);
   }
 
@@ -309,12 +319,26 @@ export class Supervisor {
     this.pumpQueue();
   }
 
+  private armTerminalExpiry(child: RunningChild) {
+    const ttl = this.options.recentTerminalTtlMs;
+    if (ttl === undefined || ttl <= 0) return;
+    this.clearTimer(child, "expiryTimer");
+    child.expiryTimer = setTimeout(() => {
+      child.expiryTimer = undefined;
+      const id = child.record.status.id;
+      if (this.children.get(id) !== child || !isTerminal(child.record.status.state)) return;
+      this.children.delete(id);
+      this.emitChange();
+    }, ttl);
+    child.expiryTimer.unref?.();
+  }
+
   private clearTimers(child: RunningChild) {
     this.clearTimer(child, "startTimer");
     this.clearTimer(child, "runTimer");
   }
 
-  private clearTimer(child: RunningChild, key: "startTimer" | "runTimer") {
+  private clearTimer(child: RunningChild, key: "startTimer" | "runTimer" | "expiryTimer") {
     const timer = child[key];
     if (!timer) return;
     clearTimeout(timer);

modules/desktop/theming.nix

@@ -32,6 +32,9 @@ in
 
       image = wallpaper;
 
+      # Regreet is not enabled, so its styling target stays off.
+      targets.regreet.enable = false;
+
       cursor = {
         package = pkgs.bibata-cursors;
         # Solid white with a dark outline, so it stays easy to spot against the

modules/nvim/nvim.nix

@@ -19,6 +19,7 @@ in
     home-manager.users.${user} = hm: {
       programs.nixvim = {
         enable = true;
+        nixpkgs.useGlobalPackages = true;
 
         extraPackages = with pkgs; [
           git # neogit and gitsigns shell out to git

secrets/shared.yaml

@@ -3,22 +3,31 @@ sops:
     age:
         - enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBVYzZuaERsRjMyaTAwL3Ri
-            b2RhaGZ1aHNOSzVMamVxWkdKb3VKTk9QMmk4CmV0R3hYN3hkMU1tVDJLNkFlT08y
-            SUdUeUZ4d2JwNmdyOWVJcmZNcEtCb1EKLS0tIHhDV1NZWWdDZUNMYjVqYUVlc0ty
-            Y1owUFZPMXBHbDhjVWxTUjZGRk1IUzQK7VENq6TjuOFlon+CJqUxbIJZ9qka78C/
-            LDsgaTD+7zCBPgASwPbF88pH6tdK7bvNLJnznlZdZBL12eOy25BmOQ==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBvdGQ0ZnZ2UlVaTFVuRmJI
+            aVZNVjZVNGdiVGVhUTVXN3luU0V1eUZFb0ZRCkVrY3lKRE9GTUEzV0ZjUnk4UHdl
+            QnFMVDhMcGVUTWFQemxrSnNEMStpSEEKLS0tIFFIQndkZHp1NkRmRlB4RXlwdk5C
+            cTJVQW9iMWhaMlk1dUxBK1ZvQTRuV0kKm7/z24q4NcDFlVuxZViDFlJodjRzRqhY
+            7X9LqouIXcGhDgwq0hh+JXRfYCz9LDiUJtOLHR7Lu/oscCBCnk7N6Q==
             -----END AGE ENCRYPTED FILE-----
           recipient: age1m0pk94ysjlw3lmf6pyuv5l5pepvdjss8w0vxjv90dq6ndp02tdgsdwdvue
         - enc: |
             -----BEGIN AGE ENCRYPTED FILE-----
-            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBHY0ZXT3lRWS9DMFA1MHhl
-            MDZiWHhEMy9INGtpd1ZOdzh0OFRoUlZDa0hZCkJwTUV4c01YWlE1QjNDd3pRN3F0
-            SGJWWmFTT1NMQktNejVHY1RrRlZJNFEKLS0tIHlRZG9ZV3FrQktSN2tURVV1NmlW
-            UTBZbFlqMmFGZ0VPSlA1dmNMU2Q3TFUKtL2V8t9+Qw5vjXursvCVRatflX8JKXJr
-            VuA8oe0nKpk7wh4fCzcT7RoRKpJY0gPFjIzeTZGVfoAmZIUWMhzRuw==
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSBTOENXYmRRNmVQeUtvOVFy
+            eElWVUhnUnJDTk93aVJCVmpTcHd2aVpKSFhJCk9oUk5ObHNSZHNwSisrSE9JbjRI
+            WVllODlYek1VMDZpMmh3M2JRTU92ZEkKLS0tIFVVNG9RNnlzS0ZvMUM3bVN2Mldo
+            N0MvcXEraDcwUHVxbTJqWGdxTGhOVG8KIhIY9QGbt/eWy9bfST4tEkjLQLylaHRm
+            AwYIwU1Hw6HXR1TX3t0YciI3c8HcWISruY/tBR3xIHIdBlQR5OTaeA==
             -----END AGE ENCRYPTED FILE-----
           recipient: age14a04vphzjq74epfrz9a09wjw8lzchtru84awzuq2n45d8f42ychqjs89qe
+        - enc: |
+            -----BEGIN AGE ENCRYPTED FILE-----
+            YWdlLWVuY3J5cHRpb24ub3JnL3YxCi0+IFgyNTUxOSA4ODgyNjQ1RFMwOGpUaG5U
+            UDNjTENrYzY5UFVTNlRONlBhNmVUUXk2OVd3ClFQUUhFaUM4YmR6dVNlMXRwWUFY
+            ais3L0FyQ1ozWjFMMHhjWmU1NU5JdVUKLS0tIG1tS1NoZjhBb3JRak9XdEpOT3Vy
+            Uk5HdUd6NUsrZWx2Y1lrWGdHRXcxZEUK470gSumRCpgYvIWJcmylw0VTgyV3et/B
+            QkVLBz5x+ShVun27nN3oz8And0qXfwgXojhM3yWnBSUa9CFBsbTOJQ==
+            -----END AGE ENCRYPTED FILE-----
+          recipient: age1wf5s0n0tgt6ld2ysgu9dc67mj8ylwecgl4utzg7hqwy3kut9zyms7aglmh
     lastmodified: "2026-07-20T03:22:00Z"
     mac: ENC[AES256_GCM,data:ei7PKVAIjJ6fGkxqJFc5wdYapq1gElel3fTJ+yKhvWHU+39aKcllG66T3d9FitRztgyt69phykHdKvxDHRUwYeyl1YBzyf1ZpPU5mXJb+hkLtVB1Am7StcP+m7jFqKSmqtYhIT9OxUrH0MJ8qeoU9216otwkhhpPz2hr1s7KYFk=,iv:Pp03KmlinjJiiTZezr0LzzkcHb1a5XWgDpu38jhl9Rk=,tag:HAqFitge+KTCtDE24t8/ig==,type:str]
     unencrypted_suffix: _unencrypted