It appears that due to the breaking changes around middleware reordering, service client modules tagged on or after yesterday are now fundamentally incompatible with runtime modules tagged before yesterday (and vice versa).
and
As for a post-mortem, this is clearly an unfortunate side-effect of the breaking change that went in on 11/15. In reality I suspect we have a host of undocumented compatibility breaks across our release history. Something as simple as an API added in one module to be consumed by another technically constitutes a break in this way, https://github.com/aws/aws-sdk-go-v2/issues/2372 is an example of this. Even though our release tooling handles updating our own module dependencies, people are free to pin to their own versions and run into breaks like this.
A true semantic versioning system would help mitigate this if not prevent it outright, but that's not something we have in place at this time.
caused by AWS not honoring Semver, and pushing breaking changes (c.f. https://github.com/aws/aws-sdk-go-v2/issues/2370)
and