Python: [Bug]: BedrockEmbeddingClient ignores an explicit region when a boto3_session is passed, and reports the wrong region

Observed Behavior

BedrockEmbeddingClient picks its region differently from BedrockChatClient, and its region attribute does not match the region it sends requests to:

With region="us-west-2" (or BEDROCK_REGION) and a boto3_session for eu-west-1, embedding requests go to eu-west-1. The explicit region is ignored, but client.region reports us-west-2.
With only a boto3_session for eu-west-1, requests go to eu-west-1, but client.region reports us-east-1.
Without a session, when boto3 finds a region in its own configuration (for example AWS_DEFAULT_REGION), requests go to that region, but client.region reports us-east-1.

BedrockChatClient (since #9249) uses the explicit region first, then the session's region, then us-east-1, and its region attribute always matches the region it uses.

Expected Behavior

The embedding client uses the same order as the chat client: region / BEDROCK_REGION, then the region of boto3_session (or boto3's own configuration when no session is passed), then us-east-1. client.region reports the region that requests are actually sent to. Nothing changes when a pre-built client is passed.

Steps to Reproduce

Make sure BEDROCK_REGION is not set.
Create a boto3 session for eu-west-1.
Create BedrockEmbeddingClient with region="us-west-2" and that session, and another one with only the session.
Compare the region of the runtime client with client.region.

Minimal Reproduction

from boto3.session import Session

from agent_framework_bedrock import BedrockChatClient, BedrockEmbeddingClient

session = Session(region_name="eu-west-1")

embeddings = BedrockEmbeddingClient(model="amazon.titan-embed-text-v2:0", region="us-west-2", boto3_session=session)
chat = BedrockChatClient(model="<model id>", region="us-west-2", boto3_session=session)
print(embeddings._bedrock_client.meta.region_name, embeddings.region)  # eu-west-1 us-west-2 (expected us-west-2 us-west-2)
print(chat._bedrock_client.meta.region_name, chat.region)              # us-west-2 us-west-2

session_only = BedrockEmbeddingClient(model="amazon.titan-embed-text-v2:0", boto3_session=session)
print(session_only._bedrock_client.meta.region_name, session_only.region)  # eu-west-1 us-east-1 (expected eu-west-1 eu-west-1)

No AWS call is needed; boto3 builds the client offline.

The cause is in agent_framework_bedrock/_embedding_client.py: the runtime client is created with region_name=boto3_session.region_name or resolved_region, so the session's region wins over the configured one, while self.region is set to resolved_region (the configured region or us-east-1).

Error Messages and Stack Traces

No error. Requests go to a different region than the one configured (or reported), so they can fail on model availability or account access, or send data to an unexpected region.

Package Versions

agent-framework-bedrock: 1.0.0b261008 (main at b5e5521), agent-framework-core: 1.21.0, boto3: 1.43.107

Python Version

Python 3.12

Additional Context

I'd like to fix this. The change is a few lines in RawBedrockEmbeddingClient.__init__ (resolve the region in the same order as the chat client and report it) plus regression tests mirroring the chat client's region tests from #9249.

AI assistance: I used an AI coding assistant for the analysis and to draft this report. I reproduced and verified the behavior myself.

Md. Shalah Uddin (@shanto462)

Thanks Md. Shalah Uddin (@shanto462) for the precise repro and for opening #9349 with tests that mirror #9249.

I get the same result on current main (cae4955, no AWS_*/BEDROCK_* variables, no AWS config file). With #9349's source, the first four rows match the expected behavior in the issue:

Case (cells: runtime client region / `.region`)	embedding, main	embedding, #9349	chat, main
`region="us-west-2"` + session in eu-west-1	eu-west-1 / us-west-2	us-west-2 / us-west-2	us-west-2 / us-west-2
session in eu-west-1 only	eu-west-1 / us-east-1	eu-west-1 / eu-west-1	eu-west-1 / eu-west-1
`BEDROCK_REGION=us-west-2` + session in eu-west-1	eu-west-1 / us-west-2	us-west-2 / us-west-2	us-west-2 / us-west-2
no session, `AWS_DEFAULT_REGION=ap-southeast-2`	ap-southeast-2 / us-east-1	ap-southeast-2 / ap-southeast-2	us-east-1 / us-east-1 (pinned without a session; #9349 keeps this difference on purpose)
nothing set	us-east-1 / us-east-1	us-east-1 / us-east-1	us-east-1 / us-east-1
pre-built `client` in eu-west-1 (out of scope per the issue)	eu-west-1 / us-east-1	eu-west-1 / us-east-1	eu-west-1 / us-east-1

The cause matches the report: _embedding_client.py:144 lets the session region win, while :149 reports resolved_region from :126. The chat client resolves once (_chat_client.py:325-326) and uses that value for both.

# #9349's tests against main's _embedding_client.py
FAILED tests/bedrock/test_bedrock_embedding_client.py::test_bedrock_embedding_resolves_region_with_boto3_session[session-region]
FAILED tests/bedrock/test_bedrock_embedding_client.py::test_bedrock_embedding_resolves_region_with_boto3_session[region-argument-wins]
FAILED tests/bedrock/test_bedrock_embedding_client.py::test_bedrock_embedding_resolves_region_with_boto3_session[env-region-wins]
FAILED tests/bedrock/test_bedrock_embedding_client.py::test_bedrock_embedding_reports_boto3_default_region
4 failed, 9 passed, 1 deselected, 2 warnings in 2.38s

# with #9349's source and tests: python/packages/bedrock/tests -m "not integration"
88 passed, 1 deselected, 2 warnings in 1.00s

Repro script, raw output, one adjacent note

import os

from boto3.session import Session

from agent_framework_bedrock import BedrockChatClient, BedrockEmbeddingClient

EMB = "amazon.titan-embed-text-v2:0"
CHAT = "anthropic.claude-test"


def show(label, make):
    c = make()
    print(f"{label:<45} runtime={c._bedrock_client.meta.region_name:<14} .region={c.region}")


os.environ.pop("BEDROCK_REGION", None)
eu = Session(region_name="eu-west-1")
for name, cls, model in (("chat", BedrockChatClient, CHAT), ("embed", BedrockEmbeddingClient, EMB)):
    show(f"{name}: region=us-west-2 + session(eu-west-1)", lambda: cls(model=model, region="us-west-2", boto3_session=eu))
    show(f"{name}: session(eu-west-1) only", lambda: cls(model=model, boto3_session=eu))
    os.environ["BEDROCK_REGION"] = "us-west-2"
    show(f"{name}: BEDROCK_REGION=us-west-2 + session", lambda: cls(model=model, boto3_session=eu))
    os.environ.pop("BEDROCK_REGION")
    os.environ["AWS_DEFAULT_REGION"] = "ap-southeast-2"
    show(f"{name}: no session, AWS_DEFAULT_REGION=ap-se-2", lambda: cls(model=model))
    os.environ.pop("AWS_DEFAULT_REGION")
    show(f"{name}: nothing set", lambda: cls(model=model))
    show(f"{name}: pre-built client(eu-west-1)", lambda: cls(model=model, client=eu.client("bedrock-runtime")))

# main cae49553
chat: region=us-west-2 + session(eu-west-1)   runtime=us-west-2      .region=us-west-2
chat: session(eu-west-1) only                 runtime=eu-west-1      .region=eu-west-1
chat: BEDROCK_REGION=us-west-2 + session      runtime=us-west-2      .region=us-west-2
chat: no session, AWS_DEFAULT_REGION=ap-se-2  runtime=us-east-1      .region=us-east-1
chat: nothing set                             runtime=us-east-1      .region=us-east-1
chat: pre-built client(eu-west-1)             runtime=eu-west-1      .region=us-east-1
embed: region=us-west-2 + session(eu-west-1)  runtime=eu-west-1      .region=us-west-2
embed: session(eu-west-1) only                runtime=eu-west-1      .region=us-east-1
embed: BEDROCK_REGION=us-west-2 + session     runtime=eu-west-1      .region=us-west-2
embed: no session, AWS_DEFAULT_REGION=ap-se-2 runtime=ap-southeast-2 .region=us-east-1
embed: nothing set                            runtime=us-east-1      .region=us-east-1
embed: pre-built client(eu-west-1)            runtime=eu-west-1      .region=us-east-1

# #9349 45420b3c, embedding rows
embed: region=us-west-2 + session(eu-west-1)  runtime=us-west-2      .region=us-west-2
embed: session(eu-west-1) only                runtime=eu-west-1      .region=eu-west-1
embed: BEDROCK_REGION=us-west-2 + session     runtime=us-west-2      .region=us-west-2
embed: no session, AWS_DEFAULT_REGION=ap-se-2 runtime=ap-southeast-2 .region=ap-southeast-2
embed: nothing set                            runtime=us-east-1      .region=us-east-1
embed: pre-built client(eu-west-1)            runtime=eu-west-1      .region=us-east-1

The requests follow the runtime region, not .region:

from boto3.session import Session
from agent_framework_bedrock import BedrockEmbeddingClient
c = BedrockEmbeddingClient(model="amazon.titan-embed-text-v2:0", region="us-west-2", boto3_session=Session(region_name="eu-west-1"))
print(c.region, c.service_url())

# main
us-west-2 https://bedrock-runtime.eu-west-1.amazonaws.com
# #9349
us-west-2 https://bedrock-runtime.us-west-2.amazonaws.com

Adjacent, for the last row: on the chat client .region also builds service_url() (_chat_client.py:1064), so a pre-built eu-west-1 client returns https://bedrock-runtime.us-east-1.amazonaws.com.

Happy to leave it with you. Claude (via Claude Code) assisted with the checks and this write-up; the outputs above are from local runs.

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Python: [Bug]: BedrockEmbeddingClient ignores an explicit region when a boto3_session is passed, and reports the wrong region #9348

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Python: [Bug]: BedrockEmbeddingClient ignores an explicit region when a boto3_session is passed, and reports the wrong region #9348

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Error Messages and Stack Traces

Package Versions

Python Version

Additional Context

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kimnamu commented on Oct 15, 2026

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