AWS Bedrock

An llm · client with dialect: aws-bedrock sends requests to Amazon Bedrock Runtime. Applications keep using the OpenAI or Anthropic SDK: Zilla Plus converts each request for Bedrock, signs it with AWS Signature Version 4, and returns the reply in the caller's API. An llm · server can also accept requests in the Bedrock Converse API.

Available in Zilla Plus

Configuration

bedrock_llm_client:
  type: llm
  kind: client
  options:
    dialect: aws-bedrock
    server: https://bedrock-runtime.us-east-1.amazonaws.com
  telemetry:
    metrics:
      - llm.*
  exit: bedrock_http_client

bedrock_http_client:
  type: http
  kind: client
  exit: bedrock_tls_client

bedrock_tls_client:
  type: tls
  kind: client
  options:
    sni:
      - bedrock-runtime.us-east-1.amazonaws.com
  exit: bedrock_tcp_client

bedrock_tcp_client:
  type: tcp
  kind: client
  options:
    host: bedrock-runtime.us-east-1.amazonaws.com
    port: 443

Unlike the OpenAI and Anthropic clients, an aws-bedrock client doesn't connect through sys:http_client. It exits to its own http · client, tls · client, and tcp · client. To use another region, change the host in all three places: server, sni, and host.

Route Bedrock model IDs to it from llm · proxy:

north_llm_proxy:
  type: llm
  kind: proxy
  routes:
    - when:
        - model:
            - anthropic.*
            - amazon.*
            - us.anthropic.*
            - us.amazon.*
      exit: bedrock_llm_client

Many Bedrock models are called through a cross-region inference profile, whose ID starts with a geography such as us., for example us.anthropic.claude-haiku-4-5-20251001-v1:0. Add patterns for the profile IDs your callers use.

How Requests Are Sent

Zilla Plus picks the Bedrock API for each request from the API the caller used and the model it asked for:

Caller's API	Model	Bedrock API
Anthropic	`anthropic.`, with or without a geography prefix such as `us.anthropic.`	InvokeModel, with the request in Anthropic's own format
OpenAI	`openai.*`	InvokeModel, with the request in OpenAI's own format
OpenAI or Anthropic	Any other model	Converse, converted from the caller's API
Bedrock Converse	Any model	Converse

InvokeModel sends the caller's request to /model/{modelId}/invoke, or /model/{modelId}/invoke-with-response-stream for a streaming request, and returns the model's reply as it is. Zilla Plus removes the model and stream members and adds the anthropic_version that Anthropic models require. For openai.* models, the reasoning the model returns between <reasoning> tags is removed from the reply.
Converse sends the request to /model/{modelId}/converse. A streaming request converted from the OpenAI or Anthropic API is also sent to /converse, and the reply is streamed back in the caller's format. Only a caller that uses the Bedrock Converse API itself is sent to /converse-stream.

Model in the Path

Zilla Plus puts each request's model in the Bedrock request path, so one client serves every Bedrock model routed to it. A path in the server URL is ignored.

What Is Converted

When a request is converted to the Converse API, each part of the conversation is converted to its Converse form:

Section	Converse
System instruction	`system[].text`
User and assistant text, refusals	`text`
Images and documents sent inline	`image` and `document`, with `bytes`
Audio sent inline, from the OpenAI API	`audio`, with `bytes`
Reasoning, from the Anthropic API	`reasoningContent`
Tool definitions	`toolConfig.tools[].toolSpec`
Tool calls	`toolUse`
Tool results	`toolResult`

The output token limit is carried across as inferenceConfig.maxTokens. Other request settings aren't carried across, as with any translation.

Some content can't be converted:

Images and documents sent by URL, and tool definitions for tools the provider runs, are rejected with 400 Bad Request, naming the section, such as user-image cannot be converted from openai to aws-bedrock.
Server tool results and citations are skipped.
Video, audio, and Amazon S3 references in a Bedrock Converse request can't be sent to OpenAI or Anthropic, and are rejected with 400 Bad Request.
Members only Bedrock has, such as guardrailConfig, cachePoint, and additionalModelRequestFields, are kept when the caller uses the Bedrock Converse API, and dropped otherwise.

Credentials

Zilla Plus signs every request itself, so options.authorization is not used with aws-bedrock. It takes credentials from the standard AWS default credentials chain:

The AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, and AWS_SESSION_TOKEN environment variables
An EKS pod's IAM role (IRSA), an ECS task role, or an EC2 instance profile

The identity needs the bedrock:InvokeModel and bedrock:InvokeModelWithResponseStream permissions on the models callers ask for. When no credentials are available, requests fail with 503 Service Unavailable and the message AWS credentials are not available.

Region

The signing region comes from the server host, such as us-east-1 for https://bedrock-runtime.us-east-1.amazonaws.com. When the host doesn't contain a region, for example a VPC endpoint, Zilla Plus uses the AWS default region chain, such as the AWS_REGION environment variable.

Accepting the Bedrock Converse API

An llm · server with dialect: aws-bedrock, or with no dialect, also accepts requests in the Bedrock Converse API: POST /model/{modelId}/converse and POST /model/{modelId}/converse-stream. The model is taken from the path, so llm · proxy routes these requests like any other, to Bedrock or to another provider, and the reply comes back as Converse JSON or as a Converse event stream.

north_llm_server:
  type: llm
  kind: server
  options:
    dialect: aws-bedrock
  exit: north_llm_proxy

When the server has options.authorization, the request's Authorization header is checked against the guard with the credentials template, and a rejected request gets 403 with the error type UnrecognizedClientException. Zilla Plus doesn't verify AWS Signature Version 4 on incoming requests.

Errors are returned in the Bedrock format, with the error type in the x-amzn-errortype header and a {"message": ...} body:

Status	Error type
`400`	`ValidationException`
`401`, `403`	`AccessDeniedException`
`404`	`ResourceNotFoundException`
`408`	`ModelTimeoutException`
`429`	`ThrottlingException`
`503`	`ServiceUnavailableException`
Other `4xx`	`ValidationException`
Other `5xx`	`InternalServerException`

A request to any other path, including InvokeModel, gets 404 with the error type NotFoundException, and a request whose content type isn't JSON gets 415 with UnsupportedMediaTypeException.

Limits

A request must fit in one of Zilla's buffer slots, 32 KiB by default. Each event of a reply streamed from Bedrock must also fit in a buffer slot.
Bedrock doesn't report reasoning tokens.

Next Steps

OpenAI Apps on AWS Bedrock: serve OpenAI applications from Bedrock.
llm · client: the full llm · client reference.