```ts
export function applyOverrides(
  base: Record<string, string>,
  overrides: string[],
): Record<string, string> {
  if (!Array.isArray(overrides)) {
    throw new Error("Overrides must be a list of strings.");
  }

  const merged = { ...base };

  for (const override of overrides) {
    const [name, value] = override.split('=');

    if (typeof name !== 'string' || typeof value !== 'string') {
      throw new Error("Each override must be a string.");
    }
    if (!name || !override.includes('=')) {
      throw new Error("Each override must contain exactly one equals sign.");
    }

    merged[name] = value;
  }

  return merged;
}
```