Partner of ours claimed they are going to update their api. No breakage. My hopes were low and they did not disappoint.

Soon after the new version of their api went live, of course, loads of breakage. And the email contact with them is really fun.

Me: "Hello, since your update we get the issue A. Here's the complete communication."

Them: "We did not change the existing behavior. You are doing X wrong. Repeat that one call during the step and you should be fine."

Me: "Thank you, if I repeat the call, it does indeed work, albeit slower, since we are now repeating calls. Furthermore, our application was consuming your api for years and we did not change anything. So why is that step necessary now? Only after your update do our logs show errors from your API. And by the way, we now also have a issue with B. Why is that?"

Them: "Oh that's because your query the endpoint with "Fnord", try "Baz".

Me: "Yes, I do know that we query it with "Fnord" as that is what a previous endpoint of yours is responding to us. Why are we getting "Fnord"? What request do I have to make to get a "Baz" back?"

It feels like a game of wackamole. Squash one issue, ten more will pop up. I am one step away from becoming active-aggressive.