In the first place, I don't see why a third-party API would update without you knowing about it. Any decent project tells the users when there are breaking changes and provide new endpoints for the new version and maintain the old ones everyone is still using the previous version and it's their choice to migrate to the new one or not. If we're talking about an internal API that's part of a library or package, then it's the same thing, why would it be automatically updated without you knowing about it? Any update to third-party services has to be tested and only be performed if there's a strong reason to do it, such as a huge security or performance fix.

First, stay calm—panic fixes nothing. Check what the API changed, like finding out why your favorite pizza place stopped delivering. Update your app to match the new rules. If it’s broken badly, set up a quick patch or temporary workaround to keep things running. Talk to the API team if needed—politely, no angry emails! Test fixes carefully, then roll them out. Finally, tell your users, "We fixed it!" and maybe send a thank-you email for their patience. Keep an eye on the app afterward—no surprises, please!