API client lacks a messages attribute

TL;DR

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

Steps

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

When to use

You are seeing this: 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'. Use this skill when you run into "API client lacks a messages attribute".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

Versions mentioned in the source: anthropic 0.9.0, was 0.42.0. If you are on something much newer or older, the details may have shifted.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Asked in gh:anthropics/anthropic-sdk-python#352 (https://github.com/anthropics/anthropic-sdk-python/issues/352): API client lacks a messages attribute. The issue report: 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 answer: 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). Lesson: 'object has no attribute messages' almost always means a stale SDK install or a broken environment loading the old package - check anthropic.version first.