feat: comprehensive NixOS deployment infrastructure

- docs/nix-container-install.md: 474-line guide covering Determinate Systems installer, vanilla Nix, NixOS base image, architecture notes (x86_64 vs aarch64), cross-compilation, container considerations, troubleshooting - scripts/deploy.sh: 286-line deployment script with pre-flight checks, git sync, build validation (nix build --no-link), 5 actions (switch/boot/test/build/ dry-activate), color-coded logging, env-based configurability - scripts/deploy-ssh-config: SSH config for all 3 hosts with dual users for lazyworkhorse, reverse tunnel for cyt-pi, uConsole placeholder, Gitea entry Full replacements of stub files from previous commit.
feat: add NixOS deployment infrastructure
2026-05-20 14:29:38 -04:00 · 2026-04-30 00:06:12 +00:00
3 changed files with 823 additions and 0 deletions
--- a/docs/nix-container-install.md
+++ b/docs/nix-container-install.md
@@ -0,0 +1,474 @@
+# Nix Installation for Hermes Agent Container
+
+This guide covers several approaches for installing Nix in the Hermes Agent Docker
+container to enable remote NixOS deployment via `nixos-rebuild`. It covers both
+x86_64 (lazyworkhorse) and aarch64 (cyt-pi, uConsole) architectures.
+
+## Table of Contents
+
+1. [Why Nix in a Container?](#why-nix-in-a-container)
+2. [Prerequisites](#prerequisites)
+3. [Installation Methods](#installation-methods)
+   - [Method A: Determinate Systems Installer](#method-a-determinate-systems-installer-recommended)
+   - [Method B: Vanilla Nix Installer](#method-b-vanilla-nix-installer)
+   - [Method C: NixOS-Based Container Image](#method-c-nixos-based-container-image)
+4. [Architecture-Specific Notes](#architecture-specific-notes)
+   - [x86_64 (lazyworkhorse)](#x86_64-lazyworkhorse)
+   - [aarch64 (cyt-pi, uConsole)](#aarch64-cyt-pi-uconsole)
+   - [Cross-Compilation](#cross-compilation)
+5. [Post-Install Configuration](#post-install-configuration)
+6. [Verification](#verification)
+7. [Container-Specific Considerations](#container-specific-considerations)
+   - [Persistence](#persistence)
+   - [Disk Space](#disk-space)
+   - [Security](#security)
+   - [Resource Constraints](#resource-constraints)
+8. [Integration with deploy.sh](#integration-with-deploysh)
+9. [Troubleshooting](#troubleshooting)
+10. [References](#references)
+
+---
+
+## Why Nix in a Container?
+
+The Hermes Agent container runs on an Ubuntu/Debian base. To deploy NixOS
+configurations to remote hosts, we need:
+
+- `nix` — the Nix package manager (for building configurations)
+- `nixos-rebuild` — the NixOS deployment tool
+- Access to the infra repo with flake configuration
+
+Installing Nix inside the container avoids:
+- Host-level Nix installation on the Docker host
+- Cross-container volume mounts of /nix/store
+- Dependencies on the host's Nix daemon (which may be a different version)
+
+## Prerequisites
+
+- Docker host running Linux (x86_64 and/or aarch64)
+- Container base: Debian/Ubuntu (apt-based)
+- 1-2 GB additional disk space for Nix store
+- Network access to cache.nixos.org (or a local binary cache)
+- Git access to the infra repository
+
+## Installation Methods
+
+### Method A: Determinate Systems Installer (Recommended)
+
+The Determinate Systems installer is the recommended approach. It is non-interactive,
+sets up flakes by default, and handles multi-user installation cleanly.
+
+**Dockerfile additions:**
+
+```dockerfile
+# Install Nix (Determinate Systems installer)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+
+# Download and run Nix installer (non-interactive)
+RUN curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix \
+    -o /tmp/nix-install.sh \
+    && chmod +x /tmp/nix-install.sh \
+    && sh /tmp/nix-install.sh install --no-confirm \
+    && rm /tmp/nix-install.sh
+
+# Configure Nix for flakes
+RUN mkdir -p /root/.config/nix \
+    && echo 'experimental-features = nix-command flakes' > /root/.config/nix/nix.conf
+
+# Add Nix to PATH for all users
+ENV PATH="/nix/var/nix/profiles/default/bin:$PATH"
+```
+
+**Pros:**
+- Fully non-interactive (--no-confirm)
+- Enables flakes automatically
+- Sets up multi-user daemon
+- Auto-selects correct architecture
+- Handles upgrades gracefully
+
+**Cons:**
+- Downloads ~100 MB installer
+- Requires systemd in container (works with --privileged or cgroupv2)
+- Daemon mode may conflict with container exit semantics
+
+**Container runtime additions:**
+
+For the Nix daemon to work properly inside a container, you may need:
+```dockerfile
+# Ensure /nix is a volume for persistence
+VOLUME /nix
+
+# Or mount tmpfs for ephemeral builds:
+# docker run --tmpfs /nix:exec,size=4G ...
+```
+
+### Method B: Vanilla Nix Installer
+
+The official single-user Nix installer is lighter but requires manual flake setup.
+
+**Dockerfile additions:**
+
+```dockerfile
+# Install Nix (single-user, official installer)
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    curl \
+    sudo \
+    xz-utils \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Nix as root (single-user)
+RUN curl -L https://nixos.org/nix/install -o /tmp/nix-install.sh \
+    && chmod +x /tmp/nix-install.sh \
+    && sh /tmp/nix-install.sh --no-daemon \
+    && rm /tmp/nix-install.sh
+
+# Enable flakes
+RUN mkdir -p /root/.config/nix \
+    && echo 'experimental-features = nix-command flakes' > /root/.config/nix/nix.conf
+
+# Source Nix in shell
+RUN echo '. /root/.nix-profile/etc/profile.d/nix.sh' >> /root/.bashrc
+ENV PATH="/root/.nix-profile/bin:$PATH"
+```
+
+**Pros:**
+- Smaller installer
+- No daemon needed (single-user mode)
+- Works in containers without systemd
+- Simpler container lifecycle
+
+**Cons:**
+- Manual flake configuration required
+- Single-user only (no multi-user isolation)
+- PATH must be set manually
+- No automatic garbage collection
+
+### Method C: NixOS-Based Container Image
+
+For maximum isolation, use an official NixOS base image for the build stage.
+
+**Multi-stage Dockerfile:**
+
+```dockerfile
+# Build stage: NixOS builder
+FROM nixos/nix:latest AS builder
+
+COPY infra /infra
+WORKDIR /infra
+
+# Build the configuration once
+RUN nix build '.#nixosConfigurations.lazyworkhorse.config.system.build.toplevel'
+
+# Final stage: Hermes container
+FROM ubuntu:22.04
+
+# Copy the Nix closure and binary cache
+COPY --from=builder /nix /nix
+
+# ... rest of Hermes setup
+```
+
+**Pros:**
+- Purely declarative build environment
+- No installation at runtime
+- Easy to pin Nix version
+- Good for CI/CD pipelines
+
+**Cons:**
+- Requires multi-stage Docker build
+- Larger initial image build
+- Harder to update Nix version at runtime
+- Overkill if Nix is only needed for `nixos-rebuild`
+
+---
+
+## Architecture-Specific Notes
+
+### x86_64 (lazyworkhorse)
+
+The Hermes container likely runs on x86_64 hardware for the primary server.
+Nix will download x86_64 binaries from cache.nixos.org by default.
+
+**No special configuration needed** — the standard installer works out of the box.
+
+If the container is running on an AMD Ryzen/EPYC or Intel Xeon, consider:
+```bash
+# Enable CPU-specific optimizations (optional)
+echo 'extra-platforms = x86_64-v1 x86_64-v2 x86_64-v3' >> /root/.config/nix/nix.conf
+```
+
+### aarch64 (cyt-pi, uConsole)
+
+When building for aarch64 targets from an x86_64 container, you need either:
+1. Remote builder (aarch64 machine does the build), or
+2. QEMU-based emulation (slower but self-contained), or
+3. Build directly on the aarch64 target using `--build-host`
+
+**For QEMU emulation in the container:**
+
+```dockerfile
+# Enable binfmt for aarch64 emulation
+RUN apt-get update && apt-get install -y --no-install-recommends \
+    qemu-user-static \
+    binfmt-support \
+    && rm -rf /var/lib/apt/lists/*
+
+# Register aarch64 binfmt
+RUN update-binfmts --enable qemu-aarch64
+```
+
+**Container runtime (for QEMU):**
+```bash
+docker run --privileged --rm ... hermes-agent
+# Or with specific capability:
+docker run --cap-add=SYS_ADMIN --security-opt seccomp=unconfined ... hermes-agent
+```
+
+### Cross-Compilation
+
+For native cross-compilation (without emulation), add to your Nix configuration:
+
+```nix
+# In your flake.nix or nix.conf
+{
+  nix.settings.extra-platforms = [ "aarch64-linux" "x86_64-linux" ];
+  nix.settings.extra-sandbox-paths = [ ];
+  boot.binfmt.emulatedSystems = [ "aarch64-linux" ];
+}
+```
+
+Or in `nix.conf`:
+```
+extra-platforms = x86_64-linux aarch64-linux
+extra-sandbox-paths =
+```
+
+---
+
+## Post-Install Configuration
+
+### nix.conf for Container Usage
+
+Recommended `/root/.config/nix/nix.conf`:
+
+```ini
+experimental-features = nix-command flakes
+substituters = https://cache.nixos.org/
+trusted-users = root
+max-jobs = auto
+cores = 0
+sandbox = false
+```
+
+Note: `sandbox = false` is needed inside containers that lack full sandbox
+support. This is safe in a single-tenant container environment.
+
+### PATH Setup
+
+Add to your Dockerfile:
+```dockerfile
+ENV PATH="/nix/var/nix/profiles/default/bin:/root/.nix-profile/bin:${PATH}"
+```
+
+### Shell Integration
+
+```dockerfile
+RUN echo 'source /root/.nix-profile/etc/profile.d/nix.sh' >> /root/.bashrc
+```
+
+---
+
+## Verification
+
+After installation, verify with:
+
+```bash
+# Check Nix is available
+nix --version
+
+# Check nixos-rebuild
+nixos-rebuild --help | head -3
+
+# Verify flakes are enabled
+nix flake --help
+
+# Test a build (must be in infra repo)
+cd /opt/data/infra
+nix build --no-link '.#nixosConfigurations.lazyworkhorse.config.system.build.toplevel'
+
+# Check available systems
+nix eval --impure --expr 'builtins.currentSystem'
+```
+
+---
+
+## Container-Specific Considerations
+
+### Persistence
+
+The `/nix` directory should be a Docker volume to avoid re-downloading
+packages on every container restart:
+
+```yaml
+# docker-compose.yml
+volumes:
+  - nix-store:/nix
+
+volumes:
+  nix-store:
+```
+
+Without persistence, every container restart requires re-downloading the
+entire Nix store (~500 MB - 2 GB depending on packages used).
+
+### Disk Space
+
+The Nix store grows over time as old generations accumulate. Set up garbage
+collection:
+
+```bash
+# Manual GC
+nix store gc
+
+# Remove old generations
+nix-collect-garbage --delete-older-than 30d
+
+# Automatic GC (in nix.conf)
+# Currently not supported in nix.conf, but you can run a cron job:
+# nix store gc --max 10G
+```
+
+In Docker, limit store growth with:
+```dockerfile
+# Configure max store size
+RUN mkdir -p /etc/nix && \
+    echo 'min-free = 5368709120' > /etc/nix/nix.conf  # Keep 5GB free
+```
+
+### Security
+
+Running Nix in a container introduces some security considerations:
+
+1. **Sandboxing:** `sandbox = false` disables build isolation. In a multi-tenant
+   container, this means Nix builds can affect the container filesystem.
+   **Mitigation:** Only build configs you trust (your own infra repo).
+
+2. **Network access:** The container needs outbound access to cache.nixos.org.
+   If using a restricted network, set up a local binary cache:
+   ```nix
+   substituters = https://cache.nixos.org/ https://nix-cache.internal/
+   ```
+
+3. **Privileged mode:** QEMU emulation for aarch64 builds may need `--privileged`
+   or `--security-opt seccomp=unconfined`. This reduces container isolation.
+   **Mitigation:** Use remote builders or build natively on the target.
+
+4. **Supply chain:** Nix derivations pin exact inputs via hashes. Verify
+   flake.lock is committed and reviewed.
+
+### Resource Constraints
+
+Nix builds can be memory and CPU intensive:
+
+```nix
+# Limit build parallelism in nix.conf
+max-jobs = 2
+cores = 4
+
+# Or set per-build:
+# nix build --max-jobs 2 --cores 4
+```
+
+For containers with limited memory (< 2 GB), consider:
+- Building on the target host instead (`--build-host`)
+- Using the deploy script's `build` action separately
+
+---
+
+## Integration with deploy.sh
+
+The deployment script at `scripts/deploy.sh` expects:
+
+1. **Nix installed** with flakes enabled
+2. **SSH key** at `/opt/data/home/.ssh/id_hermes_gitea` (or via SSH_KEY env)
+3. **Infra repo** cloned at the script's parent directory
+4. **Network access** to:
+   - `code.lazyworkhorse.net:2222` (Gitea for git operations)
+   - Target hosts via SSH (see deploy-ssh-config)
+   - `cache.nixos.org` or a local substitute
+
+Typical usage from Hermes:
+
+```bash
+# Full deployment
+./scripts/deploy.sh lazyworkhorse master switch
+
+# Build-only check (no remote deployment)
+./scripts/deploy.sh cyt-pi master build
+
+# Dry run
+./scripts/deploy.sh uConsole feat/test dry-activate
+
+# Override SSH key
+SSH_KEY=/opt/data/home/.ssh/my-custom-key ./deploy.sh lazyworkhorse
+```
+
+---
+
+## Troubleshooting
+
+### "nix: command not found"
+
+- Ensure Nix is installed and PATH is set:
+  ```bash
+  export PATH="/nix/var/nix/profiles/default/bin:/root/.nix-profile/bin:$PATH"
+  ```
+- Check installation: `ls -la /nix/` should exist
+- Re-source profile: `. /root/.nix-profile/etc/profile.d/nix.sh`
+
+### "error: unable to download ... cache.nixos.org"
+
+- Check network connectivity: `ping cache.nixos.org`
+- Check DNS resolution from inside the container
+- If behind a proxy, set `http_proxy` / `https_proxy` environment variables
+
+### "sandbox: cannot run build in sandbox"
+
+- Add `sandbox = false` to nix.conf
+- Or run container with `--privileged` or `--security-opt seccomp=unconfined`
+
+### "aarch64-linux builds fail on x86_64"
+
+- QEMU binfmt not registered. Check: `ls /proc/sys/fs/binfmt_misc/`
+- Rebuild QEMU registration: `docker run --privileged --rm tonistiigi/binfmt --install all`
+- Or use `--build-host` to build on the target directly
+
+### "nixos-rebuild fails with SSH errors"
+
+- Verify SSH key exists and has correct permissions:
+  ```bash
+  ls -la /opt/data/home/.ssh/id_hermes_gitea
+  chmod 600 /opt/data/home/.ssh/id_hermes_gitea
+  ```
+- Test SSH manually: `ssh -p 2424 -i /opt/data/home/.ssh/id_hermes_gitea ai-worker@lazyworkhorse.net`
+- Check target host is reachable: `nc -zv lazyworkhorse.net 2424`
+
+### "git fetch fails from Gitea"
+
+- Verify GIT_SSH_COMMAND is set: `echo $GIT_SSH_COMMAND`
+- Test git SSH: `ssh -T git@code.lazyworkhorse.net -p 2222`
+- Check the infra repo remote: `git remote -v`
+
+---
+
+## References
+
+- [Determinate Systems Nix Installer](https://github.com/DeterminateSystems/nix-installer)
+- [NixOS Manual: Installation](https://nixos.org/manual/nix/stable/installation/)
+- [NixOS Wiki: Flakes](https://nixos.wiki/wiki/Flakes)
+- [NixOS Wiki: nixos-rebuild](https://nixos.wiki/wiki/Nixos-rebuild)
+- [NixOS Wiki: Cross Compilation](https://nixos.wiki/wiki/Cross_Compilation)
+- [Multi-arch Docker with QEMU](https://github.com/multiarch/qemu-user-static)
--- a/scripts/deploy-ssh-config
+++ b/scripts/deploy-ssh-config
@@ -0,0 +1,63 @@
+# Hermes Container SSH Configuration
+# For NixOS deployment to remote hosts
+#
+# Usage:
+#   cp scripts/deploy-ssh-config ~/.ssh/config.d/hermes-include
+#   Or: cat scripts/deploy-ssh-config >> ~/.ssh/config
+#
+# This config covers all NixOS hosts managed from the Hermes container.
+# Lazyworkhorse has two users: ai-worker (primary automation) and gortium (admin).
+# Cyt-pi connects via reverse SSH tunnel on port 19999.
+# uConsole is a placeholder until LAN-hostname resolution is confirmed.
+
+# ── Global defaults ──────────────────────────────────────────────────
+Host *
+    ServerAliveInterval 60
+    ServerAliveCountMax 3
+    TCPKeepAlive yes
+    Compression yes
+    CompressionLevel 6
+    ControlMaster auto
+    ControlPath ~/.ssh/controlmasters/%r@%h:%p
+    ControlPersist 10m
+    StrictHostKeyChecking no
+    UserKnownHostsFile /dev/null
+
+# ── Hosts ──────────────────────────────────────────────────────────────
+
+# Lazyworkhorse — x86_64 main server (ai-worker@lazyworkhorse.net:2424)
+Host lazyworkhorse
+    HostName lazyworkhorse.net
+    User ai-worker
+    Port 2424
+    IdentityFile /opt/data/home/.ssh/id_hermes_gitea
+
+# Lazyworkhorse — admin access (gortium@lazyworkhorse.net:2425)
+Host lazyworkhorse-admin
+    HostName lazyworkhorse.net
+    User gortium
+    Port 2425
+    IdentityFile /opt/data/home/.ssh/id_hermes_gitea
+
+# Cyt-pi — aarch64 Pi Zero 2 W
+# Connected via reverse SSH tunnel (gortium directs tunnel to :19999)
+Host cyt-pi
+    HostName localhost
+    User gortium
+    Port 19999
+    IdentityFile /opt/data/home/.ssh/id_hermes_gitea
+
+# uConsole — aarch64 ClockworkPi (placeholder hostname)
+# Replace uconsole.lan with actual IP/hostname when deployed
+Host uConsole uconsole
+    HostName uconsole.lan
+    User gortium
+    Port 22
+    IdentityFile /opt/data/home/.ssh/id_hermes_gitea
+
+# ── Gitea host — for git operations ──────────────────────────────────
+Host code
+    HostName code.lazyworkhorse.net
+    Port 2222
+    User gortium
+    IdentityFile /opt/data/home/.ssh/id_hermes_gitea
--- a/scripts/deploy.sh
+++ b/scripts/deploy.sh
@@ -0,0 +1,286 @@
+#!/usr/bin/env bash
+# NixOS Deployment Helper Script
+# Remote NixOS deployment from Hermes container to target hosts.
+#
+# Usage: ./deploy.sh <hostname> [branch] [action]
+#
+# Actions:
+#   switch       Activate configuration now (default)
+#   boot         Activate on next reboot
+#   test         Activate without switching generations
+#   build        Build locally only, no remote activation
+#   dry-activate Show what would change without applying
+#
+# Examples:
+#   ./deploy.sh lazyworkhorse                  # deploy master/switch to lazyworkhorse
+#   ./deploy.sh cyt-pi feat/test boot          # deploy feat/test branch, activate on boot
+#   ./deploy.sh uConsole master build          # just build, don't deploy
+#   NO_BUILD_CHECK=1 ./deploy.sh uConsole      # skip the pre-flight nix build
+#
+# Environment variables:
+#   SSH_USER      SSH user (default: auto-detected per host)
+#   SSH_PORT      SSH port (default: auto-detected per host)
+#   SSH_KEY       SSH identity file
+#   BUILD_HOST    Build flake for this host (default: same as target host)
+#   NO_BUILD_CHECK  Set to 1 to skip local nix build before deployment
+
+set -euo pipefail
+
+# ── Colors ──────────────────────────────────────────────────────────────
+RED='\033[0;31m'
+GREEN='\033[0;32m'
+YELLOW='\033[1;33m'
+BLUE='\033[0;34m'
+CYAN='\033[0;36m'
+NC='\033[0m' # No Color
+
+info()  { echo -e "${BLUE}[INFO]${NC}  $*"; }
+ok()    { echo -e "${GREEN}[OK]${NC}    $*"; }
+warn()  { echo -e "${YELLOW}[WARN]${NC}  $*"; }
+error() { echo -e "${RED}[ERROR]${NC} $*" >&2; }
+step()  { echo -e "\n${CYAN}━━━ $* ━━━${NC}"; }
+
+# ── Cleanup trap ───────────────────────────────────────────────────────
+cleanup() {
+    local ec=$?
+    if [ $ec -ne 0 ]; then
+        error "Deployment failed with exit code $ec"
+    fi
+    exit $ec
+}
+trap cleanup EXIT
+
+# ── Usage / Help ───────────────────────────────────────────────────────
+show_usage() {
+    cat <<EOF
+Usage: $0 <hostname> [branch] [action]
+
+Remote NixOS deployment from Hermes container to target hosts.
+
+HOSTNAME (required):
+    lazyworkhorse     x86_64 main server
+    cyt-pi            aarch64 Pi Zero 2 W (via reverse tunnel)
+    uConsole          aarch64 ClockworkPi
+
+BRANCH (optional, default: master):
+    Git branch or tag to deploy. Fetched from origin.
+
+ACTION (optional, default: switch):
+    switch           Activate configuration now (default)
+    boot             Activate on next reboot
+    test             Activate without switching generations
+    build            Build locally only, skip remote deployment
+    dry-activate     Show what would change without applying
+
+Environment variables:
+    SSH_USER       SSH username override
+    SSH_PORT       SSH port override
+    SSH_KEY        SSH identity file path
+    BUILD_HOST     Build flake hostname (default: same as HOSTNAME)
+    NO_BUILD_CHECK Skip local nix build validation (set to 1)
+
+Examples:
+    $0 lazyworkhorse                       # deploy master/switch
+    $0 cyt-pi feat/test boot               # deploy feature branch, boot
+    $0 uConsole master build               # just build, no remote
+    NO_BUILD_CHECK=1 $0 uConsole           # skip build check
+
+EOF
+    exit 0
+}
+
+# ── Argument parsing ───────────────────────────────────────────────────
+HOSTNAME="${1:-}"
+BRANCH="${2:-master}"
+ACTION="${3:-switch}"
+NO_BUILD_CHECK="${NO_BUILD_CHECK:-0}"
+
+if [ "$HOSTNAME" = "--help" ] || [ "$HOSTNAME" = "-h" ] || [ -z "$HOSTNAME" ]; then
+    show_usage
+fi
+
+# ── Host configuration ─────────────────────────────────────────────────
+case "$HOSTNAME" in
+    lazyworkhorse)
+        DEFAULT_SSH_USER="ai-worker"
+        DEFAULT_SSH_PORT="2424"
+        ARCH="x86_64-linux"
+        ;;
+    cyt-pi)
+        DEFAULT_SSH_USER="gortium"
+        DEFAULT_SSH_PORT="19999"
+        ARCH="aarch64-linux"
+        ;;
+    uConsole)
+        DEFAULT_SSH_USER="gortium"
+        DEFAULT_SSH_PORT="22"
+        ARCH="aarch64-linux"
+        ;;
+    *)
+        error "Unknown host: $HOSTNAME"
+        echo "Supported hosts: lazyworkhorse, cyt-pi, uConsole"
+        exit 1
+        ;;
+esac
+
+SSH_USER="${SSH_USER:-$DEFAULT_SSH_USER}"
+SSH_PORT="${SSH_PORT:-$DEFAULT_SSH_PORT}"
+SSH_KEY="${SSH_KEY:-/opt/data/home/.ssh/id_hermes_gitea}"
+BUILD_HOST="${BUILD_HOST:-$HOSTNAME}"
+
+SSH_OPTS="-p $SSH_PORT -i $SSH_KEY -o StrictHostKeyChecking=no -o UserKnownHostsFile=/dev/null"
+SSH_TARGET="${SSH_USER}@${HOSTNAME}"
+export GIT_SSH_COMMAND="ssh -i $SSH_KEY -p 2222 -o StrictHostKeyChecking=no"
+export PATH="/nix/var/nix/profiles/default/bin:$PATH"
+
+# ── Banner ─────────────────────────────────────────────────────────────
+echo "╔══════════════════════════════════════════════╗"
+echo "║         NixOS Remote Deployment              ║"
+echo "╚══════════════════════════════════════════════╝"
+info "Host:   $HOSTNAME ($ARCH)"
+info "Branch: $BRANCH"
+info "Action: $ACTION"
+info "SSH:    ${SSH_USER}@${HOSTNAME}:${SSH_PORT}"
+echo ""
+
+# ── Pre-flight checks ─────────────────────────────────────────────────
+step "Pre-flight checks"
+
+# 1. Check required tools
+for cmd in nix git ssh; do
+    if ! command -v "$cmd" &>/dev/null; then
+        error "Required tool not found: $cmd"
+        exit 1
+    fi
+done
+ok "Required tools available (nix, git, ssh)"
+
+# 2. Check infra repo
+INFRA_DIR="$(cd "$(dirname "$0")/.." && pwd)"
+if [ ! -d "$INFRA_DIR/.git" ]; then
+    error "Not a git repository: $INFRA_DIR"
+    exit 1
+fi
+ok "Infra repo found at $INFRA_DIR"
+
+# 3. Check SSH connectivity (skip for build-only actions)
+if [ "$ACTION" != "build" ]; then
+    if ssh $SSH_OPTS -o ConnectTimeout=5 "$SSH_TARGET" "echo connected" &>/dev/null; then
+        ok "SSH connectivity to $HOSTNAME verified"
+    else
+        warn "Cannot reach $HOSTNAME via SSH — deployment step will fail later"
+    fi
+fi
+
+# ── Git sync ───────────────────────────────────────────────────────────
+step "Git sync"
+
+cd "$INFRA_DIR"
+
+# Stash local changes if any
+if ! git diff --quiet HEAD; then
+    warn "Local changes detected, stashing..."
+    git stash push -m "auto-stash before deploy $(date -Iseconds)"
+    STASHED=1
+else
+    STASHED=0
+fi
+
+# Fetch and checkout
+git fetch origin "$BRANCH" 2>/dev/null || git fetch origin master
+if git rev-parse --verify "origin/$BRANCH" &>/dev/null 2>&1; then
+    # Remote branch exists — fast-forward merge
+    git checkout -B "$BRANCH" "origin/$BRANCH"
+elif git rev-parse --verify "$BRANCH" &>/dev/null 2>&1; then
+    # Local branch or tag
+    git checkout "$BRANCH"
+else
+    error "Branch/tag not found: $BRANCH"
+    exit 1
+fi
+ok "Checked out $BRANCH ($(git rev-parse --short HEAD))"
+
+# Update submodules
+if [ -f .gitmodules ]; then
+    git submodule update --init --recursive
+    ok "Submodules updated"
+fi
+
+# ── Build validation ──────────────────────────────────────────────────
+if [ "$NO_BUILD_CHECK" != "1" ]; then
+    step "Build validation"
+    info "Building nixosConfigurations.$BUILD_HOST (no link)..."
+
+    if nix build --no-link --print-build-logs \
+        ".#nixosConfigurations.${BUILD_HOST}.config.system.build.toplevel" 2>&1; then
+        ok "Build succeeded for $BUILD_HOST"
+    else
+        error "Build failed for $BUILD_HOST"
+        exit 1
+    fi
+else
+    warn "Build check skipped (NO_BUILD_CHECK=1)"
+fi
+
+# ── Deployment ─────────────────────────────────────────────────────────
+if [ "$ACTION" = "build" ]; then
+    step "Build complete (no deployment)"
+    info "Use one of: switch, boot, test, dry-activate to deploy"
+    exit 0
+fi
+
+step "Deployment ($ACTION)"
+
+# Build the nixos-rebuild command
+case "$ACTION" in
+    switch|boot|test)
+        nixos-rebuild "$ACTION" \
+            --flake ".#$HOSTNAME" \
+            --target-host "$SSH_TARGET" \
+            --build-host "localhost" \
+            --use-remote-sudo \
+            --max-jobs 4
+        ;;
+    dry-activate)
+        nixos-rebuild dry-activate \
+            --flake ".#$HOSTNAME" \
+            --target-host "$SSH_TARGET" \
+            --build-host "localhost" \
+            --use-remote-sudo
+        ;;
+    *)
+        error "Unknown action: $ACTION"
+        echo "Valid actions: switch, boot, test, build, dry-activate"
+        exit 1
+        ;;
+esac
+
+# ── Check result ───────────────────────────────────────────────────────
+DEPLOY_EXIT=$?
+if [ $DEPLOY_EXIT -eq 0 ]; then
+    echo ""
+    ok "Deployment to $HOSTNAME ($ACTION) completed successfully"
+    case "$ACTION" in
+        switch|test)
+            info "Configuration is now active"
+            ;;
+        boot)
+            info "Configuration will activate on next reboot"
+            ;;
+        dry-activate)
+            info "Dry-run complete — no changes applied"
+            ;;
+    esac
+else
+    error "Deployment failed with exit code $DEPLOY_EXIT"
+    exit $DEPLOY_EXIT
+fi
+
+echo ""
+echo "╔══════════════════════════════════════════════╗"
+echo "║         Deployment Complete                   ║"
+echo "╚══════════════════════════════════════════════╝"
+info "Host:   $HOSTNAME"
+info "Branch: $BRANCH ($(git rev-parse --short HEAD))"
+info "Action: $ACTION"
+info "Time:   $(date -Iseconds)"