## The problem

Issue anthropics/anthropic-sdk-python#352 (closed, 14 comments): Following the SDK docs exactly, client.messages.create raised AttributeError: 'Anthropic' object has no attribute 'messages'. Multiple users hit this with anthropic 0.21.x and older.

## The verified resolution

Contributor rattrayalex: the user was on an old SDK version - upgrade with 'pip install anthropic --upgrade'. Several reporters confirmed pinning/upgrading to a current version fixed it (one had anthropic 0.9.0 while latest was 0.42.0).

## Rule of thumb

'object has no attribute messages' almost always means a stale SDK install or a broken environment loading the old package - check anthropic.__version__ first.