Ethereum's protocol upgrades, like the shift to Ethereum 2.0 and beyond, can pose compatibility challenges for existing applications. Upgrades often introduce changes to the network’s consensus mechanism, gas fees, or smart contract functionality, potentially breaking dApps built on older protocols. Developers must adapt to new standards, such as EIP-1559 or sharding, which may require code refactoring or redeployment. While Ethereum strives for backward compatibility, complex upgrades can disrupt APIs, transaction formats, or performance, impacting user experience. dApps relying on specific gas dynamics or deprecated features face the greatest risks. Thorough testing and timely updates are crucial to ensure seamless transitions, but resource-constrained projects may struggle to keep pace with Ethereum’s rapid evolution, risking obsolescence or increased maintenance costs.