Bedrock OpenAI OSS models support

[zegerius]

What happened?

The new OpenAI OSS models as available on Bedrock result in The model is unsupported for streaming.. As per the AWS blog post they should support streaming.

Version Information

v.0.8.0-rc1

Steps to Reproduce

Add Bedrock models:

1. openai.gpt-oss-120b-1:0
2. openai.gpt-oss-20b-1:0

Query.

What browsers are you seeing the problem on?

No response

Relevant log output

LibreChat  | 2025-08-06 07:49:44 error: [api/server/controllers/agents/client.js #sendCompletion] Operation aborted The model is unsupported for streaming.
LibreChat  | 2025-08-06 07:49:44 error: [api/server/controllers/agents/client.js #sendCompletion] Unhandled error type The model is unsupported for streaming.

Screenshots

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[codelasak]

I got the same error. Any fix?

[danny-avila]

The message is coming directly from Bedrock API:
langchain-ai/langchainjs#7678

Note that the AWS Bedrock integration currently misidentifies the streaming support behavior for some models, as listed here:
https://docs.aws.amazon.com/bedrock/latest/userguide/models-supported.html

From what I can tell, based on the Bedrock OpenAI Docs and using this model in Bedrock's playground, it does not support streaming.

However, you can use Bedrock's OpenAI-like endpoint as a custom endpoint:
https://docs.aws.amazon.com/bedrock/latest/userguide/model-parameters-openai.html

Note, using it this way, we can see streaming still does not work:

It works for me with the following custom endpoint config, explicitly disabling streaming:

endpoints:
  custom:
    - name: "OpenAI via Bedrock"
      apiKey: "${AWS_BEARER_TOKEN_BEDROCK}"
      baseURL: "https://bedrock-runtime.us-west-2.amazonaws.com/openai/v1"
      models:
        default: ["openai.gpt-oss-120b-1:0", "openai.gpt-oss-20b-1:0"]
      titleConvo: true
      titleModel: "current_model"
      modelDisplayLabel: "OpenAI via Bedrock"
      addParams:
        disableStreaming: true
        stream: false
      dropParams:
        - "user"

[danny-avila]

More info on custom endpoints:

• https://www.librechat.ai/docs/quick_start/custom_endpoints