How would you design configuration for a multi-tenant application where each tenant needs different settings resolved at runtime?

Common approaches include: a custom configuration provider that loads and merges tenant-specific overrides on top of global defaults at request time (using the current tenant context, often resolved via IHttpContextAccessor or a middleware-set value), or a tenant-aware options resolution pattern (a custom ITenantOptionsProvider service) that layers a base IOptions<T> with tenant-specific overrides fetched from a database or cache -- since the standard Options pattern's IOptionsSnapshot is scoped per-request but not inherently tenant-aware, additional logic is needed to select the right values for the current tenant.

public class TenantSettingsResolver {
    private readonly IOptionsMonitor<Dictionary<string, TenantSettings>> _allTenantSettings;
    public TenantSettings GetForCurrentTenant(string tenantId) {
        return _allTenantSettings.CurrentValue.TryGetValue(tenantId, out var settings)
            ? settings
            : _defaultSettings;
    }
}