I work on a system that has a lot of third party vendors that provide various services for us.
This is a description of the behaviour of two of the vendors regarding changes to their api’s.
The good vendor wanted to make one of their private apis public but this would include a breaking change. They carefully identified which customers were using that api and gave them 2 months to move to the new api. Documentation for the new api was provided. Incidently we had ceased using the api by the deadline so it all went well.
The bad vendor wanted to make a breaking change to an api only available to their higher payment tier customers. They made the change overnight without any notification. The dev team noticed the change due to a failure in an end-to-end test. We identified the problem and found a work around, tested and deployed it 5 seconds after the first customer complaint arrived. The vendor has not yet acknowledged the bug. Problems in the api behaviour are typically described as functions as designed.
The first vendor is Contentful. The second vendor in another field is much more famous.
Please look after your customers…