feat: add OpenAI-compatible Bedrock provider (#3748)

Implements AWS Bedrock inference provider using OpenAI-compatible
endpoint for Llama models available through Bedrock.

Closes: #3410


## What does this PR do?

Adds AWS Bedrock as an inference provider using the OpenAI-compatible
endpoint. This lets us use Bedrock models (GPT-OSS, Llama) through the
standard llama-stack inference API.

The implementation uses LiteLLM's OpenAI client under the hood, so it
gets all the OpenAI compatibility features. The provider handles
per-request API key overrides via headers.

## Test Plan

**Tested the following scenarios:**
- Non-streaming completion - basic request/response flow
- Streaming completion - SSE streaming with chunked responses
- Multi-turn conversations - context retention across turns
- Tool calling - function calling with proper tool_calls format

# Bedrock OpenAI-Compatible Provider - Test Results


**Model:** `bedrock-inference/openai.gpt-oss-20b-1:0`


---

## Test 1: Model Listing

**Request:**
```http
GET /v1/models HTTP/1.1
```

**Response:**
```http
HTTP/1.1 200 OK
Content-Type: application/json

{
  "data": [
    {"identifier": "bedrock-inference/openai.gpt-oss-20b-1:0", ...},
    {"identifier": "bedrock-inference/openai.gpt-oss-40b-1:0", ...}
  ]
}
```

---

## Test 2: Non-Streaming Completion

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
Content-Type: application/json

{
  "model": "bedrock-inference/openai.gpt-oss-20b-1:0",
  "messages": [{"role": "user", "content": "Say 'Hello from Bedrock' and nothing else"}],
  "stream": false
}
```

**Response:**
```http
HTTP/1.1 200 OK
Content-Type: application/json

{
  "choices": [{
    "finish_reason": "stop",
    "message": {"content": "...Hello from Bedrock"}
  }],
  "usage": {"prompt_tokens": 79, "completion_tokens": 50, "total_tokens": 129}
}
```

---

## Test 3: Streaming Completion

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
Content-Type: application/json

{
  "model": "bedrock-inference/openai.gpt-oss-20b-1:0",
  "messages": [{"role": "user", "content": "Count from 1 to 5"}],
  "stream": true
}
```

**Response:**
```http
HTTP/1.1 200 OK
Content-Type: text/event-stream

[6 SSE chunks received]
Final content: "1, 2, 3, 4, 5"
```

---

## Test 4: Error Handling - Invalid Model

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
Content-Type: application/json

{
  "model": "invalid-model-id",
  "messages": [{"role": "user", "content": "Hello"}],
  "stream": false
}
```

**Response:**
```http
HTTP/1.1 404 Not Found
Content-Type: application/json

{
  "detail": "Model 'invalid-model-id' not found. Use 'client.models.list()' to list available Models."
}
```

---

## Test 5: Multi-Turn Conversation

**Request 1:**
```http
POST /v1/chat/completions HTTP/1.1

{
  "messages": [{"role": "user", "content": "My name is Alice"}]
}
```

**Response 1:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "message": {"content": "...Nice to meet you, Alice! How can I help you today?"}
  }]
}
```

**Request 2 (with history):**
```http
POST /v1/chat/completions HTTP/1.1

{
  "messages": [
    {"role": "user", "content": "My name is Alice"},
    {"role": "assistant", "content": "...Nice to meet you, Alice!..."},
    {"role": "user", "content": "What is my name?"}
  ]
}
```

**Response 2:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "message": {"content": "...Your name is Alice."}
  }],
  "usage": {"prompt_tokens": 183, "completion_tokens": 42}
}
```

**Context retained across turns**

---

## Test 6: System Messages

**Request:**
```http
POST /v1/chat/completions HTTP/1.1

{
  "messages": [
    {"role": "system", "content": "You are Shakespeare. Respond only in Shakespearean English."},
    {"role": "user", "content": "Tell me about the weather"}
  ]
}
```

**Response:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "message": {"content": "Lo! I heed thy request..."}
  }],
  "usage": {"completion_tokens": 813}
}
```


---

## Test 7: Tool Calling

**Request:**
```http
POST /v1/chat/completions HTTP/1.1

{
  "messages": [{"role": "user", "content": "What's the weather in San Francisco?"}],
  "tools": [{
    "type": "function",
    "function": {
      "name": "get_weather",
      "parameters": {"type": "object", "properties": {"location": {"type": "string"}}}
    }
  }]
}
```

**Response:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "finish_reason": "tool_calls",
    "message": {
      "tool_calls": [{
        "function": {"name": "get_weather", "arguments": "{\"location\":\"San Francisco\"}"}
      }]
    }
  }]
}
```

---

## Test 8: Sampling Parameters

**Request:**
```http
POST /v1/chat/completions HTTP/1.1

{
  "messages": [{"role": "user", "content": "Say hello"}],
  "temperature": 0.7,
  "top_p": 0.9
}
```

**Response:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "message": {"content": "...Hello! 👋 How can I help you today?"}
  }]
}
```

---

## Test 9: Authentication Error Handling

### Subtest A: Invalid API Key

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
x-llamastack-provider-data: {"aws_bedrock_api_key": "invalid-fake-key-12345"}

{"model": "bedrock-inference/openai.gpt-oss-20b-1:0", ...}
```

**Response:**
```http
HTTP/1.1 400 Bad Request

{
  "detail": "Invalid value: Authentication failed: Error code: 401 - {'error': {'message': 'Invalid API Key format: Must start with pre-defined prefix', ...}}"
}
```

---

### Subtest B: Empty API Key (Fallback to Config)

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
x-llamastack-provider-data: {"aws_bedrock_api_key": ""}

{"model": "bedrock-inference/openai.gpt-oss-20b-1:0", ...}
```

**Response:**
```http
HTTP/1.1 200 OK

{
  "choices": [{
    "message": {"content": "...Hello! How can I assist you today?"}
  }]
}
```

 **Fell back to config key**

---

### Subtest C: Malformed Token

**Request:**
```http
POST /v1/chat/completions HTTP/1.1
x-llamastack-provider-data: {"aws_bedrock_api_key": "not-a-valid-bedrock-token-format"}

{"model": "bedrock-inference/openai.gpt-oss-20b-1:0", ...}
```

**Response:**
```http
HTTP/1.1 400 Bad Request

{
  "detail": "Invalid value: Authentication failed: Error code: 401 - {'error': {'message': 'Invalid API Key format: Must start with pre-defined prefix', ...}}"
}
```

src/llama_stack/providers/remote/inference/bedrock/bedrock.py

@@ -4,139 +4,124 @@
 # This source code is licensed under the terms described in the LICENSE file in
 # the root directory of this source tree.
 
-import json
-from collections.abc import AsyncIterator
+from collections.abc import AsyncIterator, Iterable
 
-from botocore.client import BaseClient
+from openai import AuthenticationError
 
 from llama_stack.apis.inference import (
-    ChatCompletionRequest,
-    Inference,
+    OpenAIChatCompletion,
+    OpenAIChatCompletionChunk,
     OpenAIChatCompletionRequestWithExtraBody,
+    OpenAICompletion,
     OpenAICompletionRequestWithExtraBody,
     OpenAIEmbeddingsRequestWithExtraBody,
     OpenAIEmbeddingsResponse,
 )
-from llama_stack.apis.inference.inference import (
-    OpenAIChatCompletion,
-    OpenAIChatCompletionChunk,
-    OpenAICompletion,
-)
-from llama_stack.providers.remote.inference.bedrock.config import BedrockConfig
-from llama_stack.providers.utils.bedrock.client import create_bedrock_client
-from llama_stack.providers.utils.inference.model_registry import (
-    ModelRegistryHelper,
-)
-from llama_stack.providers.utils.inference.openai_compat import (
-    get_sampling_strategy_options,
-)
-from llama_stack.providers.utils.inference.prompt_adapter import (
-    chat_completion_request_to_prompt,
-)
+from llama_stack.core.telemetry.tracing import get_current_span
+from llama_stack.log import get_logger
+from llama_stack.providers.utils.inference.openai_mixin import OpenAIMixin
 
-from .models import MODEL_ENTRIES
+from .config import BedrockConfig
 
-REGION_PREFIX_MAP = {
-    "us": "us.",
-    "eu": "eu.",
-    "ap": "ap.",
-}
+logger = get_logger(name=__name__, category="inference::bedrock")
 
 
-def _get_region_prefix(region: str | None) -> str:
-    # AWS requires region prefixes for inference profiles
-    if region is None:
-        return "us."  # default to US when we don't know
+class BedrockInferenceAdapter(OpenAIMixin):
+    """
+    Adapter for AWS Bedrock's OpenAI-compatible API endpoints.
 
-    # Handle case insensitive region matching
-    region_lower = region.lower()
-    for prefix in REGION_PREFIX_MAP:
-        if region_lower.startswith(f"{prefix}-"):
-            return REGION_PREFIX_MAP[prefix]
+    Supports Llama models across regions and GPT-OSS models (us-west-2 only).
 
-    # Fallback to US for anything we don't recognize
-    return "us."
+    Note: Bedrock's OpenAI-compatible endpoint does not support /v1/models
+    for dynamic model discovery. Models must be pre-registered in the config.
+    """
 
+    config: BedrockConfig
+    provider_data_api_key_field: str = "aws_bedrock_api_key"
 
-def _to_inference_profile_id(model_id: str, region: str = None) -> str:
-    # Return ARNs unchanged
-    if model_id.startswith("arn:"):
-        return model_id
+    def get_base_url(self) -> str:
+        """Get base URL for OpenAI client."""
+        return f"https://bedrock-runtime.{self.config.region_name}.amazonaws.com/openai/v1"
 
-    # Return inference profile IDs that already have regional prefixes
-    if any(model_id.startswith(p) for p in REGION_PREFIX_MAP.values()):
-        return model_id
+    async def list_provider_model_ids(self) -> Iterable[str]:
+        """
+        Bedrock's OpenAI-compatible endpoint does not support the /v1/models endpoint.
+        Returns empty list since models must be pre-registered in the config.
+        """
+        return []
 
-    # Default to US East when no region is provided
-    if region is None:
-        region = "us-east-1"
-
-    return _get_region_prefix(region) + model_id
-
-
-class BedrockInferenceAdapter(
-    ModelRegistryHelper,
-    Inference,
-):
-    def __init__(self, config: BedrockConfig) -> None:
-        ModelRegistryHelper.__init__(self, model_entries=MODEL_ENTRIES)
-        self._config = config
-        self._client = None
-
-    @property
-    def client(self) -> BaseClient:
-        if self._client is None:
-            self._client = create_bedrock_client(self._config)
-        return self._client
-
-    async def initialize(self) -> None:
-        pass
-
-    async def shutdown(self) -> None:
-        if self._client is not None:
-            self._client.close()
-
-    async def _get_params_for_chat_completion(self, request: ChatCompletionRequest) -> dict:
-        bedrock_model = request.model
-
-        sampling_params = request.sampling_params
-        options = get_sampling_strategy_options(sampling_params)
-
-        if sampling_params.max_tokens:
-            options["max_gen_len"] = sampling_params.max_tokens
-        if sampling_params.repetition_penalty > 0:
-            options["repetition_penalty"] = sampling_params.repetition_penalty
-
-        prompt = await chat_completion_request_to_prompt(request, self.get_llama_model(request.model))
-
-        # Convert foundation model ID to inference profile ID
-        region_name = self.client.meta.region_name
-        inference_profile_id = _to_inference_profile_id(bedrock_model, region_name)
-
-        return {
-            "modelId": inference_profile_id,
-            "body": json.dumps(
-                {
-                    "prompt": prompt,
-                    **options,
-                }
-            ),
-        }
+    async def check_model_availability(self, model: str) -> bool:
+        """
+        Bedrock doesn't support dynamic model listing via /v1/models.
+        Always return True to accept all models registered in the config.
+        """
+        return True
 
     async def openai_embeddings(
         self,
         params: OpenAIEmbeddingsRequestWithExtraBody,
     ) -> OpenAIEmbeddingsResponse:
-        raise NotImplementedError()
+        """Bedrock's OpenAI-compatible API does not support the /v1/embeddings endpoint."""
+        raise NotImplementedError(
+            "Bedrock's OpenAI-compatible API does not support /v1/embeddings endpoint. "
+            "See https://docs.aws.amazon.com/bedrock/latest/userguide/inference-chat-completions.html"
+        )
 
     async def openai_completion(
         self,
         params: OpenAICompletionRequestWithExtraBody,
     ) -> OpenAICompletion:
-        raise NotImplementedError("OpenAI completion not supported by the Bedrock provider")
+        """Bedrock's OpenAI-compatible API does not support the /v1/completions endpoint."""
+        raise NotImplementedError(
+            "Bedrock's OpenAI-compatible API does not support /v1/completions endpoint. "
+            "Only /v1/chat/completions is supported. "
+            "See https://docs.aws.amazon.com/bedrock/latest/userguide/inference-chat-completions.html"
+        )
 
     async def openai_chat_completion(
         self,
         params: OpenAIChatCompletionRequestWithExtraBody,
     ) -> OpenAIChatCompletion | AsyncIterator[OpenAIChatCompletionChunk]:
-        raise NotImplementedError("OpenAI chat completion not supported by the Bedrock provider")
+        """Override to enable streaming usage metrics and handle authentication errors."""
+        # Enable streaming usage metrics when telemetry is active
+        if params.stream and get_current_span() is not None:
+            if params.stream_options is None:
+                params.stream_options = {"include_usage": True}
+            elif "include_usage" not in params.stream_options:
+                params.stream_options = {**params.stream_options, "include_usage": True}
+
+        try:
+            logger.debug(f"Calling Bedrock OpenAI API with model={params.model}, stream={params.stream}")
+            result = await super().openai_chat_completion(params=params)
+            logger.debug(f"Bedrock API returned: {type(result).__name__ if result is not None else 'None'}")
+
+            if result is None:
+                logger.error(f"Bedrock OpenAI client returned None for model={params.model}, stream={params.stream}")
+                raise RuntimeError(
+                    f"Bedrock API returned no response for model '{params.model}'. "
+                    "This may indicate the model is not supported or a network/API issue occurred."
+                )
+
+            return result
+        except AuthenticationError as e:
+            error_msg = str(e)
+
+            # Check if this is a token expiration error
+            if "expired" in error_msg.lower() or "Bearer Token has expired" in error_msg:
+                logger.error(f"AWS Bedrock authentication token expired: {error_msg}")
+                raise ValueError(
+                    "AWS Bedrock authentication failed: Bearer token has expired. "
+                    "The AWS_BEDROCK_API_KEY environment variable contains an expired pre-signed URL. "
+                    "Please refresh your token by generating a new pre-signed URL with AWS credentials. "
+                    "Refer to AWS Bedrock documentation for details on OpenAI-compatible endpoints."
+                ) from e
+            else:
+                logger.error(f"AWS Bedrock authentication failed: {error_msg}")
+                raise ValueError(
+                    f"AWS Bedrock authentication failed: {error_msg}. "
+                    "Please verify your API key is correct in the provider config or x-llamastack-provider-data header. "
+                    "The API key should be a valid AWS pre-signed URL for Bedrock's OpenAI-compatible endpoint."
+                ) from e
+        except Exception as e:
+            logger.error(f"Unexpected error calling Bedrock API: {type(e).__name__}: {e}", exc_info=True)
+            raise