{ ... }:
{
  # Resource limits for user sessions to prevent system wedging
  #
  # Modern systemd/cgroups v2 approach to resource control (replaces ulimits).
  # Limits apply to all user sessions (SSH, GUI, etc.) but NOT to system services.
  #
  # Rationale:
  # - Prevents runaway user processes (nix builds, compiles, etc.) from consuming
  #   all resources and making the system unresponsive
  # - System services (Nomad jobs, Consul, NFS, etc.) run outside user.slice and
  #   are unaffected by these limits
  # - Ensures SSH access remains responsive even under heavy load
  #
  # CPU: Uses CPUWeight (not CPUQuota) so user sessions can use 100% when idle,
  #      but system services get priority (1.25x) during contention
  # Memory: Soft limit at 90% (triggers pressure/reclaim), hard limit at 95%
  #         Gives 5% warning buffer before OOM kills

  systemd.slices.user = {
    sliceConfig = {
      # CPU weight: 80 vs default 100 for system services
      # When idle: user sessions use all available CPU
      # Under contention: system services get 1.25x CPU share
      CPUWeight = "80";

      # Memory soft limit: triggers reclaim and memory pressure
      # User will notice slowdown but processes keep running
      MemoryHigh = "90%";

      # Memory hard limit: OOM killer targets user.slice
      # 5% buffer between MemoryHigh and MemoryMax provides warning
      MemoryMax = "95%";

      # Limit number of tasks (processes/threads)
      # Prevents fork bombs while still allowing nix builds
      TasksMax = "4096";

      # Lower I/O priority slightly
      # System services get preference during I/O contention
      IOWeight = "90";
    };
  };
}