Fix Bedrock region detection to respect aws_profile and AWS_DEFAULT_REGION

src/anthropic/lib/bedrock/_client.py

@@ -67,17 +67,24 @@ def _prepare_options(input_options: FinalRequestOptions) -> FinalRequestOptions:
     return options
 
 
-def _infer_region() -> str:
+def _infer_region(aws_profile: str | None = None) -> str:
     """
     Infer the AWS region from the environment variables or
     from the boto3 session if available.
+
+    The resolution order is:
+    1. ``AWS_REGION`` environment variable
+    2. ``AWS_DEFAULT_REGION`` environment variable
+    3. Region resolved by a ``boto3.Session`` (respects ``AWS_PROFILE``,
+       ``~/.aws/config``, and the explicit *aws_profile* parameter)
+    4. Hard-coded ``us-east-1`` fallback (legacy behaviour)
     """
-    aws_region = os.environ.get("AWS_REGION")
+    aws_region = os.environ.get("AWS_REGION") or os.environ.get("AWS_DEFAULT_REGION")
     if aws_region is None:
         try:
             import boto3
 
-            session = boto3.Session()
+            session = boto3.Session(profile_name=aws_profile)
             if session.region_name:
                 aws_region = session.region_name
         except ImportError:
@@ -178,8 +185,8 @@ def __init__(
 
         self.aws_access_key = aws_access_key
 
-        self.aws_region = _infer_region() if aws_region is None else aws_region
         self.aws_profile = aws_profile
+        self.aws_region = _infer_region(aws_profile=aws_profile) if aws_region is None else aws_region
 
         self.aws_session_token = aws_session_token
 
@@ -228,7 +235,7 @@ def _prepare_request(self, request: httpx.Request) -> None:
             aws_access_key=self.aws_access_key,
             aws_secret_key=self.aws_secret_key,
             aws_session_token=self.aws_session_token,
-            region=self.aws_region or "us-east-1",
+            region=self.aws_region,
             profile=self.aws_profile,
             data=data,
         )
@@ -343,8 +350,8 @@ def __init__(
 
         self.aws_access_key = aws_access_key
 
-        self.aws_region = _infer_region() if aws_region is None else aws_region
         self.aws_profile = aws_profile
+        self.aws_region = _infer_region(aws_profile=aws_profile) if aws_region is None else aws_region
 
         self.aws_session_token = aws_session_token
 
@@ -393,7 +400,7 @@ async def _prepare_request(self, request: httpx.Request) -> None:
             aws_access_key=self.aws_access_key,
             aws_secret_key=self.aws_secret_key,
             aws_session_token=self.aws_session_token,
-            region=self.aws_region or "us-east-1",
+            region=self.aws_region,
             profile=self.aws_profile,
             data=data,
         )

tests/lib/test_bedrock.py

@@ -275,3 +275,68 @@ def test_region_infer_from_specified_profile(
     client = AnthropicBedrock()
 
     assert client.aws_region == next(profile for profile in profiles if profile["name"] == aws_profile)["region"]
+
+
+def test_region_infer_from_aws_default_region(monkeypatch: t.Any) -> None:
+    """AWS_DEFAULT_REGION should be respected when AWS_REGION is not set."""
+    monkeypatch.delenv("AWS_REGION", raising=False)
+    monkeypatch.setenv("AWS_DEFAULT_REGION", "eu-west-1")
+    client = AnthropicBedrock(
+        aws_access_key="example-access-key",
+        aws_secret_key="example-secret-key",
+    )
+    assert client.aws_region == "eu-west-1"
+
+
+def test_aws_region_takes_precedence_over_aws_default_region(monkeypatch: t.Any) -> None:
+    """AWS_REGION should take precedence over AWS_DEFAULT_REGION."""
+    monkeypatch.setenv("AWS_REGION", "us-west-2")
+    monkeypatch.setenv("AWS_DEFAULT_REGION", "eu-west-1")
+    client = AnthropicBedrock(
+        aws_access_key="example-access-key",
+        aws_secret_key="example-secret-key",
+    )
+    assert client.aws_region == "us-west-2"
+
+
+@pytest.mark.parametrize(
+    "profiles",
+    [
+        pytest.param(
+            [{"name": "default", "region": "us-east-2"}, {"name": "custom", "region": "ap-southeast-1"}],
+            id="custom profile via constructor",
+        ),
+    ],
+)
+def test_region_infer_from_explicit_aws_profile_param(
+    mock_aws_config: None,  # noqa: ARG001
+    monkeypatch: t.Any,
+) -> None:
+    """When aws_profile is passed to the constructor, its region should be used
+    even without setting the AWS_PROFILE env var."""
+    monkeypatch.delenv("AWS_REGION", raising=False)
+    monkeypatch.delenv("AWS_DEFAULT_REGION", raising=False)
+    monkeypatch.delenv("AWS_PROFILE", raising=False)
+    client = AnthropicBedrock(aws_profile="custom")
+    assert client.aws_region == "ap-southeast-1"
+
+
+@pytest.mark.parametrize(
+    "profiles",
+    [
+        pytest.param(
+            [{"name": "default", "region": "us-east-2"}, {"name": "custom", "region": "ap-southeast-1"}],
+            id="async custom profile via constructor",
+        ),
+    ],
+)
+def test_region_infer_from_explicit_aws_profile_param_async(
+    mock_aws_config: None,  # noqa: ARG001
+    monkeypatch: t.Any,
+) -> None:
+    """AsyncAnthropicBedrock should also respect the aws_profile parameter for region inference."""
+    monkeypatch.delenv("AWS_REGION", raising=False)
+    monkeypatch.delenv("AWS_DEFAULT_REGION", raising=False)
+    monkeypatch.delenv("AWS_PROFILE", raising=False)
+    client = AsyncAnthropicBedrock(aws_profile="custom")
+    assert client.aws_region == "ap-southeast-1"