fix: resolve AWS client SigV4 signing, forced SageMaker dep, and missing embed params

- Fix SigV4 host header mismatch: update copied headers dict with correct
  host after URL rewrite, so AWSRequest signs with the Bedrock/SageMaker
  host instead of stale api.cohere.com
- Add mode parameter to cohere_aws.Client to conditionally initialize
  boto3 clients (bedrock-runtime/bedrock vs sagemaker-runtime/sagemaker),
  avoiding forced SageMaker dependency for Bedrock users
- Add output_dimension and embedding_types params to embed() for Embed v4

Closes #721

Co-Authored-By: Claude Opus 4.6 <[email protected]>

Author: fern-support

src/cohere/aws_client.py

@@ -239,6 +239,7 @@ def _event_hook(request: httpx.Request) -> None:
         )
         request.url = URL(url)
         request.headers["host"] = request.url.host
+        headers["host"] = request.url.host
 
         if endpoint == "rerank":
             body["api_version"] = get_api_version(version=api_version)

src/cohere/manually_maintained/cohere_aws/client.py

@@ -20,17 +20,23 @@ class Client:
     def __init__(
            self,
             aws_region: typing.Optional[str] = None,
+            mode: Mode = Mode.SAGEMAKER,
         ):
         """
         By default we assume region configured in AWS CLI (`aws configure get region`). You can change the region with
         `aws configure set region us-west-2` or override it with `region_name` parameter.
         """
-        self._client = lazy_boto3().client("sagemaker-runtime", region_name=aws_region)
-        self._service_client = lazy_boto3().client("sagemaker", region_name=aws_region)
+        self.mode = mode
         if os.environ.get('AWS_DEFAULT_REGION') is None:
             os.environ['AWS_DEFAULT_REGION'] = aws_region
-        self._sess = lazy_sagemaker().Session(sagemaker_client=self._service_client)
-        self.mode = Mode.SAGEMAKER
+
+        if self.mode == Mode.SAGEMAKER:
+            self._client = lazy_boto3().client("sagemaker-runtime", region_name=aws_region)
+            self._service_client = lazy_boto3().client("sagemaker", region_name=aws_region)
+            self._sess = lazy_sagemaker().Session(sagemaker_client=self._service_client)
+        elif self.mode == Mode.BEDROCK:
+            self._client = lazy_boto3().client("bedrock-runtime", region_name=aws_region)
+            self._service_client = lazy_boto3().client("bedrock", region_name=aws_region)
 
 
 
@@ -550,11 +556,15 @@ def embed(
         variant: Optional[str] = None,
         input_type: Optional[str] = None,
         model_id: Optional[str] = None,
+        output_dimension: Optional[int] = None,
+        embedding_types: Optional[List[str]] = None,
     ) -> Embeddings:
         json_params = {
             'texts': texts,
             'truncate': truncate,
-            "input_type": input_type
+            "input_type": input_type,
+            "output_dimension": output_dimension,
+            "embedding_types": embedding_types,
         }
         for key, value in list(json_params.items()):
             if value is None: