Connecting AWS Bedrock models to new Claude Agent SDK

[arindam-giri]

Claude Agent SDK hangs when using AWS Bedrock backend

Description

When using the Claude Agent SDK with AWS Bedrock (via CLAUDE_CODE_USE_BEDROCK=1), the SDK hangs after receiving the initial SystemMessage with subtype='init' and never proceeds to get a response from the model. The process times out and no assistant messages are received.

Environment

• Python Version: 3.12
• claude-agent-sdk Version: 0.1.1
• anthropic Version: 0.69.0
• OS: macOS
• AWS Region: us-east-1
• Bedrock Model: us.anthropic.claude-sonnet-4-20250514-v1:0 (Claude Sonnet 4)

Steps to Reproduce

1. Set up AWS credentials with a profile in ~/.aws/credentials:

[arindam_linux]
aws_access_key_id = AKIA...
aws_secret_access_key = ...

2. Install required packages:

pip install anthropic[bedrock] claude-agent-sdk

3. Run the following code:

import asyncio
import boto3
import os
from claude_agent_sdk import query, ClaudeAgentOptions

async def main():
    # Enable Bedrock mode
    os.environ["CLAUDE_CODE_USE_BEDROCK"] = "1"
    
    # Set up AWS
    boto3.setup_default_session(profile_name="arindam_linux")
    os.environ["AWS_REGION"] = "us-east-1"
    
    # Configure options
    options = ClaudeAgentOptions(
        model="us.anthropic.claude-sonnet-4-20250514-v1:0",
        permission_mode='bypassPermissions',
        max_turns=1,
        allowed_tools=[]
    )
    
    # Query
    async for message in query(prompt="Say hello", options=options):
        print(f"Message type: {type(message).__name__}")
        if hasattr(message, 'subtype'):
            print(f"Subtype: {message.subtype}")

asyncio.run(main())

Expected Behavior

The SDK should:

1. Receive the init SystemMessage
2. Send the prompt to AWS Bedrock
3. Receive and yield the assistant's response
4. Complete successfully

Actual Behavior

The SDK:

1. ✅ Receives the init SystemMessage correctly
2. ❌ Hangs indefinitely after that
3. ❌ Never receives any AssistantMessage or response
4. ❌ Times out after 30+ seconds with no further messages

Output:

[Message 1]
Type: SystemMessage
Subtype: init
------------------------------------------------------------
<hangs here indefinitely>

Verification that Bedrock Works

Direct Bedrock API calls work perfectly with the same credentials and model:

import boto3
import json

boto3.setup_default_session(profile_name="arindam_linux")
client = boto3.client("bedrock-runtime", region_name="us-east-1")

native_request = {
    "anthropic_version": "bedrock-2023-05-31",
    "max_tokens": 100,
    "messages": [{"role": "user", "content": [{"type": "text", "text": "Say hello"}]}],
}

response = client.invoke_model(
    modelId="us.anthropic.claude-sonnet-4-20250514-v1:0",
    body=json.dumps(native_request)
)

model_response = json.loads(response["body"].read())
print(model_response['content'][0]['text'])
# Output: Hello! It's nice to meet you. How are you doing today?

This confirms:

• ✅ AWS credentials are correct
• ✅ Bedrock access is enabled
• ✅ Model is accessible
• ✅ IAM permissions are sufficient

Additional Context

I do not have ANTHROPIC_API_KEY setup since I do not want to use that key. I want to use the Bedrock model instead.

---

Thanks.

Happy to provide any additional information or testing needed.

[alejandroBallesterosC]

I was also running into this, for me it was a permissions issue.

I recommend reviewing your permissions and making sure they are set correctly because the Claude Code CLI requires more permissions than just Bedrock:InvokeModel.

Here are the permissions to make sure you've enabled as per the Anthropic Docs:

{
  "Version": "......",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": [
        "bedrock:InvokeModel",
        "bedrock:InvokeModelWithResponseStream",
        "bedrock:ListInferenceProfiles"
      ],
      "Resource": [
        "arn:aws:bedrock:*:*:inference-profile/*",
        "arn:aws:bedrock:*:*:application-inference-profile/*"
      ]
    }
  ]
}

[arindam-giri]

Thanks. @alejandroBallesterosC . I already had full bedrock access attached to the IAM user. Still, I added the IAM as suggested from documentation and removed earlier roles. But it didn't work it seems.

Here's the current log (after 1 minute or so..):
I will dig deeper if I can find anything.

(venv312) arindam@arindams-MacBook-Pro claude % python claude_code_sdk2.py
INFO:__main__:Initializing with Bedrock (CLAUDE_CODE_USE_BEDROCK=1)...
INFO:botocore.credentials:Found credentials in shared credentials file: ~/.aws/credentials
INFO:__main__:AWS Region: None
INFO:__main__:AWS Credentials loaded: True
INFO:__main__:Sending prompt: Write a simple Python function to calculate factorial of a number and save it to factorial.py
==================================================

Message 1:
SystemMessage(subtype='init', data={'type': 'system', 'subtype': 'init', 'cwd': '/Users/arindam/Documents/playground/git-repos/genai-engineering/basic_model_calls/claude', 'session_id': 'fb0d3216-936a-4d7e-a619-3bbdfdbef2cb', 'tools': ['Task', 'Bash', 'Glob', 'Grep', 'ExitPlanMode', 'Read', 'Edit', 'Write', 'NotebookEdit', 'WebFetch', 'TodoWrite', 'BashOutput', 'KillShell', 'SlashCommand'], 'mcp_servers': [], 'model': 'us.anthropic.claude-sonnet-4-20250514-v1:0', 'permissionMode': 'acceptEdits', 'slash_commands': ['compact', 'context', 'cost', 'init', 'output-style:new', 'pr-comments', 'release-notes', 'todos', 'review', 'security-review'], 'apiKeySource': 'none', 'output_style': 'default', 'agents': ['general-purpose', 'statusline-setup', 'output-style-setup'], 'uuid': 'f5d03ef9-f183-4d88-8701-5700e545228a'})
----------------------------------------

Message 2:
AssistantMessage(content=[TextBlock(text='API Error: Could not load credentials from any providers')], model='<synthetic>', parent_tool_use_id=None)
----------------------------------------

Message 3:
ResultMessage(subtype='success', duration_ms=188765, duration_api_ms=0, is_error=True, num_turns=1, session_id='fb0d3216-936a-4d7e-a619-3bbdfdbef2cb', total_cost_usd=0, usage={'input_tokens': 0, 'cache_creation_input_tokens': 0, 'cache_read_input_tokens': 0, 'output_tokens': 0, 'server_tool_use': {'web_search_requests': 0}, 'service_tier': 'standard', 'cache_creation': {'ephemeral_1h_input_tokens': 0, 'ephemeral_5m_input_tokens': 0}}, result='API Error: Could not load credentials from any providers')
----------------------------------------
INFO:__main__:Received final message: success
==================================================

ERROR:asyncio:Task exception was never retrieved
future: <Task finished name='Task-6' coro=<<async_generator_athrow without __name__>()> exception=RuntimeError('Attempted to exit cancel scope in a different task than it was entered in')>
Traceback (most recent call last):
  File "/Users/arindam/Documents/playground/git-repos/genai-engineering/venv312/lib/python3.12/site-packages/claude_agent_sdk/_internal/client.py", line 118, in process_query
    yield parse_message(data)
GeneratorExit

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/arindam/Documents/playground/git-repos/genai-engineering/venv312/lib/python3.12/site-packages/claude_agent_sdk/_internal/client.py", line 121, in process_query
    await query.close()
  File "/Users/arindam/Documents/playground/git-repos/genai-engineering/venv312/lib/python3.12/site-packages/claude_agent_sdk/_internal/query.py", line 516, in close
    await self._tg.__aexit__(None, None, None)
  File "/Users/arindam/Documents/playground/git-repos/genai-engineering/venv312/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 792, in __aexit__
    return self.cancel_scope.__exit__(exc_type, exc_val, exc_tb)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/arindam/Documents/playground/git-repos/genai-engineering/venv312/lib/python3.12/site-packages/anyio/_backends/_asyncio.py", line 459, in __exit__
    raise RuntimeError(
RuntimeError: Attempted to exit cancel scope in a different task than it was entered in

[zraphael]

Just a heads up that I've been running into the same issue, tried multiple troubleshooting but can't get any response from Bedrock using the SDK, stuck with the Subtype init as well. Calling claude cli as subprocess works just fine

[conorvenus]

I've also been running into the same issue, but on the Typescript SDK

[arindam-giri]

ok. I managed to make it work with Bedrock API key (for an IAM user) and AmazonBedrockFullAccess IAM permission to that user PLUS the custom Bedrock recommended policy which @alejandroBallesterosC referred above.

So, your IAM user will have two policies attached.

Here's the output:

[arindam-giri]

Closing, since it is resolved via correcting IAM permissions.