stackptr · stackptr · Mar 24, 2026
diff --git a/hosts/glyph/services/default.nix b/hosts/glyph/services/default.nix
@@ -84,6 +84,16 @@
     group = "graphite-mcp";
   };
 
+  age.secrets.agent-sandbox-api-key = {
+    file = ./../secrets/agent-sandbox-api-key.age;
+    mode = "400";
+  };
+
+  services.agent-sandbox = {
+    enable = true;
+    apiKeyFile = config.age.secrets.agent-sandbox-api-key.path;
+  };
+
   services.basic-memory.enable = true;
   rc.backup = {
     enable = true;

diff --git a/modules/nixos/llm/agent-sandbox.nix b/modules/nixos/llm/agent-sandbox.nix
@@ -0,0 +1,243 @@
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}: let
+  inherit (lib) mkIf mkOption mkEnableOption types;
+
+  cfg = config.services.agent-sandbox;
+
+  # Packages available inside the sandbox
+  sandboxPackages = with pkgs;
+    [
+      bash
+      claude-code
+      coreutils
+      curl
+      findutils
+      gawk
+      git
+      gnugrep
+      gnused
+      gnutar
+      gzip
+      jq
+      nodejs_24
+      openssh
+      ripgrep
+      xz
+    ]
+    ++ cfg.extraPackages;
+
+  # Build a minimal NixOS root filesystem for the container
+  sandboxRootfs = pkgs.runCommand "agent-sandbox-rootfs" {} ''
+    mkdir -p $out/{bin,etc,tmp,nix,usr/bin,var/tmp}
+    mkdir -p $out/etc/ssl/certs
+
+    # Symlink all sandbox packages into a unified profile
+    ${lib.concatMapStringsSep "\n" (pkg: ''
+        for dir in bin lib share etc; do
+          if [ -d "${pkg}/$dir" ]; then
+            mkdir -p $out/$dir
+            for f in "${pkg}/$dir"/*; do
+              ln -sf "$f" "$out/$dir/" 2>/dev/null || true
+            done
+          fi
+        done
+      '')
+      sandboxPackages}
+
+    # SSL certificates for HTTPS
+    ln -sf ${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt $out/etc/ssl/certs/ca-certificates.crt
+    ln -sf ${pkgs.cacert}/etc/ssl/certs/ca-bundle.crt $out/etc/ssl/certs/ca-bundle.crt
+
+    # Basic system files
+    echo "root:x:0:0:root:/root:/bin/bash" > $out/etc/passwd
+    echo "agent:x:1000:1000:agent:/home/agent:/bin/bash" >> $out/etc/passwd
+    echo "root:x:0:" > $out/etc/group
+    echo "agent:x:1000:" >> $out/etc/group
+    echo "nameserver 100.100.100.100" > $out/etc/resolv.conf
+    echo "nameserver 1.1.1.1" >> $out/etc/resolv.conf
+
+    # Env wrapper script
+    cat > $out/bin/agent-entry <<'ENTRY'
+    #!/bin/bash
+    set -euo pipefail
+    export HOME=/home/agent
+    export PATH="/bin:/usr/bin"
+    export SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
+    export NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
+
+    if [ -f /home/agent/.env ]; then
+      set -a
+      source /home/agent/.env
+      set +a
+    fi
+
+    cd /workspace
+    exec "$@"
+    ENTRY
+    chmod +x $out/bin/agent-entry
+  '';
+
+  # Script to launch a sandboxed agent run
+  launchScript = pkgs.writeShellScriptBin "agent-sandbox" ''
+    set -euo pipefail
+
+    usage() {
+      echo "Usage: agent-sandbox [options] <repo-url-or-path> [prompt]"
+      echo ""
+      echo "Options:"
+      echo "  -b, --branch BRANCH    Branch to checkout"
+      echo "  -n, --name NAME        Session name (default: auto-generated)"
+      echo "  -p, --prompt-file FILE  Read prompt from file instead of argument"
+      echo "  -k, --keep             Keep sandbox after completion"
+      echo "  -h, --help             Show this help"
+      exit 0
+    }
+
+    BRANCH=""
+    SESSION_NAME="agent-$(date +%s)-$$"
+    PROMPT_FILE=""
+    KEEP=false
+
+    while [[ $# -gt 0 ]]; do
+      case "$1" in
+        -b|--branch) BRANCH="$2"; shift 2 ;;
+        -n|--name) SESSION_NAME="$2"; shift 2 ;;
+        -p|--prompt-file) PROMPT_FILE="$2"; shift 2 ;;
+        -k|--keep) KEEP=true; shift ;;
+        -h|--help) usage ;;
+        *) break ;;
+      esac
+    done
+
+    REPO="''${1:?repo URL or path required}"
+    PROMPT="''${2:-}"
+
+    if [ -n "$PROMPT_FILE" ] && [ -z "$PROMPT" ]; then
+      PROMPT="$(cat "$PROMPT_FILE")"
+    fi
+
+    if [ -z "$PROMPT" ]; then
+      echo "Error: prompt required (as argument or via --prompt-file)"
+      exit 1
+    fi
+
+    SANDBOX_BASE="${cfg.stateDirectory}/sessions/$SESSION_NAME"
+    WORKSPACE="$SANDBOX_BASE/workspace"
+    OVERLAY_UPPER="$SANDBOX_BASE/upper"
+    OVERLAY_WORK="$SANDBOX_BASE/work"
+    OVERLAY_MERGED="$SANDBOX_BASE/merged"
+
+    mkdir -p "$WORKSPACE" "$OVERLAY_UPPER" "$OVERLAY_WORK" "$OVERLAY_MERGED"
+
+    cleanup() {
+      if [ "$KEEP" = "false" ]; then
+        umount "$OVERLAY_MERGED" 2>/dev/null || true
+        rm -rf "$SANDBOX_BASE"
+      else
+        umount "$OVERLAY_MERGED" 2>/dev/null || true
+        echo "Sandbox preserved at: $SANDBOX_BASE"
+        echo "Workspace: $WORKSPACE"
+      fi
+    }
+    trap cleanup EXIT
+
+    # Clone or copy the repo
+    if [[ "$REPO" == http* ]] || [[ "$REPO" == git@* ]]; then
+      echo "Cloning $REPO..."
+      git clone ''${BRANCH:+--branch "$BRANCH"} --depth=1 "$REPO" "$WORKSPACE"
+    elif [ -d "$REPO" ]; then
+      echo "Copying $REPO..."
+      cp -a "$REPO/." "$WORKSPACE/"
+      if [ -n "$BRANCH" ]; then
+        git -C "$WORKSPACE" checkout "$BRANCH"
+      fi
+    else
+      echo "Error: $REPO is not a valid URL or directory"
+      exit 1
+    fi
+
+    # Set up overlay filesystem for rootfs (sandbox packages are read-only)
+    mount -t overlay overlay \
+      -o lowerdir=${sandboxRootfs},upperdir=$OVERLAY_UPPER,workdir=$OVERLAY_WORK \
+      "$OVERLAY_MERGED"
+
+    mkdir -p "$OVERLAY_MERGED/home/agent" "$OVERLAY_MERGED/workspace"
+
+    # Write the API key into the sandbox
+    if [ -f "${cfg.apiKeyFile}" ]; then
+      echo "ANTHROPIC_API_KEY=$(cat "${cfg.apiKeyFile}")" > "$OVERLAY_MERGED/home/agent/.env"
+      chmod 600 "$OVERLAY_MERGED/home/agent/.env"
+    fi
+
+    echo "Starting sandboxed agent session: $SESSION_NAME"
+    echo "Workspace: $WORKSPACE"
+    echo "Prompt: $PROMPT"
+
+    # Run Claude Code inside systemd-nspawn container
+    systemd-nspawn \
+      --quiet \
+      --directory="$OVERLAY_MERGED" \
+      --bind="$WORKSPACE:/workspace" \
+      --bind-ro=/nix/store \
+      --private-network=false \
+      --user=root \
+      --setenv=HOME=/home/agent \
+      --setenv=PATH="/bin:/usr/bin" \
+      --setenv=SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt \
+      --setenv=NIX_SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt \
+      --setenv=ANTHROPIC_API_KEY="$(cat "${cfg.apiKeyFile}" 2>/dev/null || echo "")" \
+      /bin/claude \
+        --dangerously-skip-permissions \
+        --print \
+        --output-format=text \
+        "$PROMPT"
+
+    echo "Agent session $SESSION_NAME completed."
+
+    # Show what changed
+    if [ -d "$WORKSPACE/.git" ]; then
+      echo ""
+      echo "=== Changes ==="
+      git -C "$WORKSPACE" --no-pager diff --stat
+    fi
+  '';
+in {
+  options.services.agent-sandbox = {
+    enable = mkEnableOption "sandboxed AI agent execution environment";
+
+    stateDirectory = mkOption {
+      type = types.path;
+      default = "/var/lib/agent-sandbox";
+      description = "Directory for sandbox sessions and state.";
+    };
+
+    apiKeyFile = mkOption {
+      type = types.path;
+      description = "Path to file containing ANTHROPIC_API_KEY.";
+    };
+
+    extraPackages = mkOption {
+      type = types.listOf types.package;
+      default = [];
+      description = "Additional packages to make available inside sandboxes.";
+    };
+  };
+
+  config = mkIf cfg.enable {
+    # Ensure systemd-nspawn is available
+    environment.systemPackages = [
+      launchScript
+      pkgs.systemd
+    ];
+
+    # Create state directory
+    systemd.tmpfiles.rules = [
+      "d ${cfg.stateDirectory} 0750 root root -"
+      "d ${cfg.stateDirectory}/sessions 0750 root root -"
+    ];
+  };
+}
diff --git a/modules/nixos/llm/default.nix b/modules/nixos/llm/default.nix
@@ -1,5 +1,6 @@
 {
   imports = [
+    ./agent-sandbox.nix
     ./basic-memory.nix
     ./graphite-mcp.nix
     ./kagi.nix