```typescript
/** Returns the quotient of `a` divided by `b`, handling edge cases defensively. */
export function safeDivide(a: number, b: number): number {
  if (typeof a !== 'number' || typeof b !== 'number') {
    throw new Error('Both arguments must be numbers');
  }

  const result = a / b;
  if (!isFinite(result)) {
    throw new Error('Division by zero or infinite result');
  }
  return result;
}
```