Defaults Plus Overrides

Defaults Plus Overrides

Category: Architecture Time Saved: 2+ hours avoiding configuration complexity Battle-tested: Yes — user preference systems, role-based config

The Problem

You're building a system with configurable behavior — user preferences, role-based permissions, or tenant-specific settings. You need sensible defaults but also flexibility. You end up with either rigid presets OR overwhelming configuration options.

Why It's Hard

• Too rigid: Users can't customize what they need
• Too flexible: Users must configure everything
• Presets only: Edge cases require workarounds
• Full config: Decision fatigue, misconfiguration risk

The Rule

Provide role/archetype defaults, allow partial overrides, clamp to safe bounds.

The Pattern

Archetype Default + User Overrides + Bounds Clamping = Final Config

Step 1: Define Archetypes

const ARCHETYPES = {
  developer: {
    verbosity: 'detailed',
    theme: 'dark',
    shortcuts: true,
    maxTokens: 4000,
    autoSave: true,
  },
  executive: {
    verbosity: 'concise',
    theme: 'light',
    shortcuts: false,
    maxTokens: 1000,
    autoSave: false,
  },
  researcher: {
    verbosity: 'detailed',
    theme: 'auto',
    shortcuts: true,
    maxTokens: 8000,
    autoSave: true,
  },
};

Step 2: Define Bounds

const BOUNDS = {
  maxTokens: { min: 100, max: 16000 },
  verbosity: ['concise', 'normal', 'detailed'],
  theme: ['light', 'dark', 'auto'],
};

Step 3: Merge with Clamping

function resolveConfig(archetype, overrides = {}) {
  // Start with archetype defaults
  const base = { ...ARCHETYPES[archetype] };
  
  // Apply user overrides
  const merged = { ...base, ...overrides };
  
  // Clamp to bounds
  return clampConfig(merged, BOUNDS);
}

function clampConfig(config, bounds) {
  const result = { ...config };
  
  for (const [key, constraint] of Object.entries(bounds)) {
    if (constraint.min !== undefined) {
      // Numeric bound
      result[key] = Math.max(constraint.min, Math.min(constraint.max, result[key]));
    } else if (Array.isArray(constraint)) {
      // Enum bound
      if (!constraint.includes(result[key])) {
        result[key] = constraint[0]; // Default to first option
      }
    }
  }
  
  return result;
}

Step 4: Usage

// User selects archetype, optionally overrides specific values
const userConfig = resolveConfig('developer', {
  theme: 'light',        // Override: prefer light theme
  maxTokens: 50000,      // Will be clamped to 16000
});

// Result:
// {
//   verbosity: 'detailed',  // From archetype
//   theme: 'light',         // User override
//   shortcuts: true,        // From archetype
//   maxTokens: 16000,       // Clamped from 50000
//   autoSave: true,         // From archetype
// }

JSON Schema Example

{
  "type": "object",
  "properties": {
    "archetype": {
      "type": "string",
      "enum": ["developer", "executive", "researcher"],
      "default": "developer"
    },
    "overrides": {
      "type": "object",
      "properties": {
        "verbosity": {
          "type": "string",
          "enum": ["concise", "normal", "detailed"]
        },
        "maxTokens": {
          "type": "integer",
          "minimum": 100,
          "maximum": 16000
        }
      }
    }
  }
}

UI Pattern

┌─────────────────────────────────────┐
│ Profile: [Developer ▾]             │
├─────────────────────────────────────┤
│ ☑ Use defaults                      │
│                                     │
│ Customize:                          │
│   Theme: [Light ▾]                  │
│   Max Tokens: [====|====] 4000      │
│   ☐ Auto-save                       │
│                                     │
│ [Reset to defaults]                 │
└─────────────────────────────────────┘

When to Use

Anti-Patterns

Verification Checklist

• Archetypes cover 80% of users out of the box
• Overrides are partial (don't require full config)
• Bounds prevent invalid/dangerous values
• Reset-to-defaults option exists
• Configuration is validated at load time

Related Skills

• universal-audit-pattern — Validating configuration