When implementing custom network protocol behavior, ensure that modifications are properly scoped to only the intended protocol types and include upstream context documentation. Avoid applying protocol-specific changes broadly across all network protocols, as this can break assumptions and cause unintended side effects. Key principles: 1. **Scope restrictions appropriately**: Limit custom behavior to specific protocol types that require it, rather than applying changes universally 2. **Document upstream context**: Include references to upstream changes and their motivations in patch files for future maintainability 3. **Align with upstream behavior**: Keep behavior consistent with upstream implementations except where explicitly needed for specific protocols Example from streaming protocol handling: ```cpp // Good: Scoped to streaming custom protocols only if (IsStreamingCustomProtocol(url)) { destination_url_data->set_range_supported(); } // Avoid: Broad application that could break other protocols destination_url_data->set_range_supported(); // Applied to all protocols ``` When modifying network service initialization, ensure proper guards are in place: ```cpp SystemNetworkContextManager* SystemNetworkContextManager::GetInstance() { if (!g_system_network_context_manager) { content::GetNetworkService(); DCHECK(g_system_network_context_manager); } return g_system_network_context_manager; } ``` This approach prevents breaking buffering assumptions for protocols like file:// URLs while enabling the required functionality for custom streaming protocols that support range requests.