[BUG] Previous wrongly forced selection of us-west-2 region by agents not fixed by Merge #254 and passage to v1.0.0

[juliencarponcy]

I've commented on the most related issue which gave rise to #254 and can't be reopen by myself

---

Hello,

This is still not working for me after the recent merge and version change / tag to 1.0.0 (before and after yesterday updates)

I'd like to suggest reopenning : #299
I reproduce the same error whenever testing different noteboooks presents in the

Checks

I have updated to the lastest minor and patch version of Strands :

Yes v1.0.0 (https://github.com/strands-agents/sdk-python@19fb01e67ce584f4195403ec70cdc728d5066c3f)

I have checked the documentation and this is not expected behavior :

Yes

I have searched ./issues and there are no duplicates of my issue:

Yes found the current one

Strands Version

1.0.0

Python Version

3.10.14

Operating System

Windows 11 Pro 26100.4349

Installation Method

uv+pip

Steps to Reproduce

Run strands, for instance in notebooks from the samples repo (https://github.com/strands-agents/samples)
Notice that we default to us-west-2 even if the aws default config specifies a different region

Expected Behavior

Strands should use AWS_REGION, or default to the value defined aws config, and not fallback to us-west-2.

Actual Behavior

We default to us-west-2 where no region is detected.

Additional Context

I use sso login which might affect the expected results, with .env files:
I am also doing this during a pro hackathon sponsored for which AWS is organizing : https://awsagentichackathon.onova.io/ so this events accounts particularity might play.

AWS_PROFILE=
AWS_REGION=us-east-1

Looks like an confusion between region-name and default-region parameters of boto3 session vs client variables (depending on the authentication method chosen or a combination of them)

Possible Solution

Instead of defaulting to us-west-2, default to the aws config default

Related Issues

strands-agents/tools#170

---

Originally posted by @juliencarponcy in #238

[zastrowm]

Hello! Would you by chance have an end-to-end example that reproduces this behavior?

If I run the following:

 aws configure set region eu-west-1

and then use the notebook from the samples repository - this code specifically:

from strands import Agent

# Initialize your agent
agent = Agent(
    system_prompt="You are a helpful assistant that provides concise responses."
)

# Send a message to the agent
response = agent("Hello! Tell me a joke.")

I do get the correct region:

ValidationException: An error occurred (ValidationException) when calling the ConverseStream operation: The provided model identifier is invalid.
└ Bedrock region: eu-west-1
└ Model id: us.anthropic.claude-sonnet-4-20250514-v1:0

Explicitly setting the region:

import os
from strands import Agent
os.environ["AWS_REGION"] = "us-west-1"

# Initialize your agent
agent = Agent(
    system_prompt="You are a helpful assistant that provides concise responses."
)

# Send a message to the agent
response = agent("Hello! Tell me a joke.")

also uses the expected region:

ValidationException: An error occurred (ValidationException) when calling the ConverseStream operation: Your account is not authorized to invoke this API operation.
└ Bedrock region: us-west-1
└ Model id: us.anthropic.claude-sonnet-4-20250514-v1:0