feat: support AnthropicMessages API flavor for Bedrock-hosted Claude

CHANGELOG.md

@@ -2,6 +2,11 @@
 
 All notable changes to `uipath_llm_client` (core package) will be documented in this file.
 
+## [1.14.0] - 2026-06-15
+
+### Added
+- `ApiFlavor.ANTHROPIC_MESSAGES` (`"AnthropicMessages"`) for Bedrock-hosted Claude models that the discovery endpoint exposes with the native Anthropic Messages wire format. The value is the discovery string verbatim because it is forwarded as the `X-UiPath-LlmGateway-ApiFlavor` header. Also mapped in `API_FLAVOR_TO_VENDOR_TYPE` to `VendorType.AWSBEDROCK` so it resolves to the Bedrock passthrough route when discovery omits the vendor field.
+
 ## [1.13.1] - 2026-06-09
 
 ### Fixed

packages/uipath_langchain_client/CHANGELOG.md

@@ -2,6 +2,15 @@
 
 All notable changes to `uipath_langchain_client` will be documented in this file.
 
+## [1.14.0] - 2026-06-15
+
+### Added
+- Support for the `AnthropicMessages` API flavor on Bedrock-hosted Claude models. `get_chat_model` now routes discovery's `apiFlavor=AnthropicMessages` (vendor `AwsBedrock`) to `UiPathChatAnthropic` configured with `vendor_type=awsbedrock` and `api_flavor=ApiFlavor.ANTHROPIC_MESSAGES`. The client keeps the Bedrock passthrough URL but uses the native `Anthropic`/`AsyncAnthropic` SDK (model-in-body wire format), which the gateway requires for this flavor, instead of `AnthropicBedrock`.
+- `UiPathChatAnthropic` now accepts an explicit `api_flavor`. When set to `ApiFlavor.ANTHROPIC_MESSAGES` it selects the native Anthropic SDK regardless of `vendor_type`; otherwise the flavor and SDK are derived from `vendor_type` exactly as before (`awsbedrock` → `invoke` + `AnthropicBedrock`, unchanged).
+
+### Changed
+- Bumped `uipath-llm-client` floor to `>=1.14.0` to pick up `ApiFlavor.ANTHROPIC_MESSAGES`.
+
 ## [1.13.1] - 2026-06-09
 
 ### Fixed

packages/uipath_langchain_client/pyproject.toml

@@ -6,7 +6,7 @@ readme = "README.md"
 requires-python = ">=3.11"
 dependencies = [
     "langchain>=1.2.15,<2.0.0",
-    "uipath-llm-client>=1.13.1,<2.0.0",
+    "uipath-llm-client>=1.14.0,<2.0.0",
 ]
 
 [project.optional-dependencies]

packages/uipath_langchain_client/src/uipath_langchain_client/__version__.py

@@ -1,3 +1,3 @@
 __title__ = "UiPath LangChain Client"
 __description__ = "A Python client for interacting with UiPath's LLM services via LangChain."
-__version__ = "1.13.1"
+__version__ = "1.14.0"

packages/uipath_langchain_client/src/uipath_langchain_client/clients/anthropic/chat_models.py

@@ -40,10 +40,20 @@ class UiPathChatAnthropic(UiPathBaseChatModel, ChatAnthropic):
         freeze_base_url=True,
     )
     vendor_type: VendorType = VendorType.ANTHROPIC
+    api_flavor: ApiFlavor | str | None = None
+    """Explicit API flavor. When ``ApiFlavor.ANTHROPIC_MESSAGES``, the request
+    uses the native Anthropic Messages wire format (model in body) while routing
+    through the hosting vendor's passthrough URL (e.g. ``vendor_type=awsbedrock``
+    for a Bedrock-hosted Claude). Otherwise the flavor is derived from
+    ``vendor_type``."""
 
     @model_validator(mode="after")
     def setup_api_flavor_and_version(self) -> Self:
         self.api_config.vendor_type = self.vendor_type
+        match self.api_flavor:
+            case ApiFlavor.ANTHROPIC_MESSAGES:
+                self.api_config.api_flavor = ApiFlavor.ANTHROPIC_MESSAGES
+                return self
         match self.vendor_type:
             case VendorType.ANTHROPIC:
                 self.api_config.api_flavor = None
@@ -67,6 +77,15 @@ def setup_api_flavor_and_version(self) -> Self:
     def _anthropic_client(
         self,
     ) -> Anthropic | AnthropicVertex | AnthropicBedrock | AnthropicFoundry:
+        match self.api_config.api_flavor:
+            case ApiFlavor.ANTHROPIC_MESSAGES:
+                return Anthropic(
+                    api_key="PLACEHOLDER",
+                    base_url=str(self.uipath_sync_client.base_url),
+                    default_headers=dict(self.uipath_sync_client.headers),
+                    max_retries=0,  # handled by the UiPathBaseChatModel
+                    http_client=self.uipath_sync_client,
+                )
         match self.vendor_type:
             case VendorType.ANTHROPIC:
                 return Anthropic(
@@ -111,6 +130,15 @@ def _anthropic_client(
     def _async_anthropic_client(
         self,
     ) -> AsyncAnthropic | AsyncAnthropicVertex | AsyncAnthropicBedrock | AsyncAnthropicFoundry:
+        match self.api_config.api_flavor:
+            case ApiFlavor.ANTHROPIC_MESSAGES:
+                return AsyncAnthropic(
+                    api_key="PLACEHOLDER",
+                    base_url=str(self.uipath_async_client.base_url),
+                    default_headers=dict(self.uipath_async_client.headers),
+                    max_retries=0,  # handled by the UiPathBaseChatModel
+                    http_client=self.uipath_async_client,
+                )
         match self.vendor_type:
             case VendorType.ANTHROPIC:
                 return AsyncAnthropic(

packages/uipath_langchain_client/src/uipath_langchain_client/factory.py

@@ -190,6 +190,21 @@ def get_chat_model(
                 **model_kwargs,
             )
         case VendorType.AWSBEDROCK:
+            if api_flavor == ApiFlavor.ANTHROPIC_MESSAGES:
+                from uipath_langchain_client.clients.anthropic.chat_models import (
+                    UiPathChatAnthropic,
+                )
+
+                return UiPathChatAnthropic(
+                    model=model_name,
+                    settings=client_settings,
+                    vendor_type=VendorType.AWSBEDROCK,
+                    api_flavor=ApiFlavor.ANTHROPIC_MESSAGES,
+                    byo_connection_id=byo_connection_id,
+                    model_details=model_details,
+                    **model_kwargs,
+                )
+
             if api_flavor == ApiFlavor.INVOKE:
                 if model_family == ModelFamily.ANTHROPIC_CLAUDE:
                     from uipath_langchain_client.clients.bedrock.chat_models import (

src/uipath/llm_client/__version__.py

@@ -1,3 +1,3 @@
 __title__ = "UiPath LLM Client"
 __description__ = "A Python client for interacting with UiPath's LLM services."
-__version__ = "1.13.1"
+__version__ = "1.14.0"

src/uipath/llm_client/clients/litellm/client.py

@@ -99,6 +99,7 @@
     ByomApiFlavor.GEMINI_EMBEDDINGS: "gemini",
     ByomApiFlavor.AWS_BEDROCK_INVOKE: "bedrock",
     ByomApiFlavor.AWS_BEDROCK_CONVERSE: "bedrock",
+    ByomApiFlavor.ANTHROPIC_MESSAGES: "bedrock",
 }
 
 

src/uipath/llm_client/settings/constants.py

@@ -32,6 +32,7 @@ class ApiFlavor(StrEnum):
     CONVERSE = "converse"
     INVOKE = "invoke"
     ANTHROPIC_CLAUDE = "anthropic-claude"
+    ANTHROPIC_MESSAGES = "AnthropicMessages"
 
 
 class ByomApiFlavor(StrEnum):
@@ -44,6 +45,7 @@ class ByomApiFlavor(StrEnum):
     GEMINI_EMBEDDINGS = "GeminiEmbeddings"
     AWS_BEDROCK_INVOKE = "AwsBedrockInvoke"
     AWS_BEDROCK_CONVERSE = "AwsBedrockConverse"
+    ANTHROPIC_MESSAGES = "AnthropicMessages"
 
 
 API_FLAVOR_TO_VENDOR_TYPE: dict[str, VendorType] = {
@@ -53,6 +55,7 @@ class ByomApiFlavor(StrEnum):
     ApiFlavor.ANTHROPIC_CLAUDE: VendorType.VERTEXAI,
     ApiFlavor.CONVERSE: VendorType.AWSBEDROCK,
     ApiFlavor.INVOKE: VendorType.AWSBEDROCK,
+    ByomApiFlavor.ANTHROPIC_MESSAGES: VendorType.AWSBEDROCK,
     ByomApiFlavor.OPENAI_CHAT_COMPLETIONS: VendorType.OPENAI,
     ByomApiFlavor.OPENAI_RESPONSES: VendorType.OPENAI,
     ByomApiFlavor.OPENAI_EMBEDDINGS: VendorType.OPENAI,
@@ -69,4 +72,5 @@ class ByomApiFlavor(StrEnum):
     ByomApiFlavor.GEMINI_GENERATE_CONTENT: ApiFlavor.GENERATE_CONTENT,
     ByomApiFlavor.AWS_BEDROCK_INVOKE: ApiFlavor.INVOKE,
     ByomApiFlavor.AWS_BEDROCK_CONVERSE: ApiFlavor.CONVERSE,
+    ByomApiFlavor.ANTHROPIC_MESSAGES: ApiFlavor.ANTHROPIC_MESSAGES,
 }

tests/core/features/test_api_config.py

@@ -3,7 +3,13 @@
 import pytest
 
 from uipath.llm_client.settings import UiPathAPIConfig
-from uipath.llm_client.settings.constants import ApiFlavor, ApiType, RoutingMode, VendorType
+from uipath.llm_client.settings.constants import (
+    API_FLAVOR_TO_VENDOR_TYPE,
+    ApiFlavor,
+    ApiType,
+    RoutingMode,
+    VendorType,
+)
 
 
 class TestUiPathAPIConfig:
@@ -83,6 +89,10 @@ def test_api_flavor_values(self):
         assert ApiFlavor.CONVERSE == "converse"
         assert ApiFlavor.INVOKE == "invoke"
         assert ApiFlavor.ANTHROPIC_CLAUDE == "anthropic-claude"
+        assert ApiFlavor.ANTHROPIC_MESSAGES == "AnthropicMessages"
+
+    def test_anthropic_messages_maps_to_bedrock_vendor(self):
+        assert API_FLAVOR_TO_VENDOR_TYPE[ApiFlavor.ANTHROPIC_MESSAGES] == VendorType.AWSBEDROCK
 
     def test_enum_string_comparison(self):
         assert ApiType.COMPLETIONS == "completions"

tests/langchain/clients/anthropic/test_unit.py

@@ -3,11 +3,17 @@
 from typing import Any
 
 import pytest
+from anthropic import (
+    Anthropic,
+    AnthropicBedrock,
+    AsyncAnthropic,
+    AsyncAnthropicBedrock,
+)
 from langchain_core.language_models.chat_models import BaseChatModel
 from langchain_tests.unit_tests import ChatModelUnitTests
 from uipath_langchain_client.clients.anthropic.chat_models import UiPathChatAnthropic
 
-from uipath.llm_client.settings import UiPathBaseSettings
+from uipath.llm_client.settings import ApiFlavor, UiPathBaseSettings, VendorType
 
 ANTHROPIC_CHAT_CLASSES = [UiPathChatAnthropic]
 
@@ -32,3 +38,67 @@ def chat_model_params(self) -> dict[str, Any]:
 
     @pytest.mark.xfail(reason="Skipping serdes test for now")
     def test_serdes(self, *args: Any, **kwargs: Any) -> None: ...
+
+
+def _build(client_settings: UiPathBaseSettings, **kwargs: Any) -> UiPathChatAnthropic:
+    return UiPathChatAnthropic(
+        model="anthropic.claude-sonnet-4-6",
+        settings=client_settings,
+        model_details={},
+        **kwargs,
+    )
+
+
+class TestAnthropicMessagesFlavor:
+    """AnthropicMessages uses the native Anthropic SDK (model-in-body wire format)
+    over the awsbedrock passthrough URL."""
+
+    def test_sets_anthropic_messages_flavor_over_bedrock_url(
+        self, client_settings: UiPathBaseSettings
+    ):
+        chat = _build(
+            client_settings,
+            vendor_type=VendorType.AWSBEDROCK,
+            api_flavor=ApiFlavor.ANTHROPIC_MESSAGES,
+        )
+        assert chat.api_config.vendor_type == VendorType.AWSBEDROCK
+        assert chat.api_config.api_flavor == ApiFlavor.ANTHROPIC_MESSAGES
+
+    def test_uses_native_anthropic_sdk(self, client_settings: UiPathBaseSettings):
+        chat = _build(
+            client_settings,
+            vendor_type=VendorType.AWSBEDROCK,
+            api_flavor=ApiFlavor.ANTHROPIC_MESSAGES,
+        )
+        assert isinstance(chat._anthropic_client, Anthropic)
+        assert not isinstance(chat._anthropic_client, AnthropicBedrock)
+        assert isinstance(chat._async_anthropic_client, AsyncAnthropic)
+        assert not isinstance(chat._async_anthropic_client, AsyncAnthropicBedrock)
+
+    def test_flavor_is_orthogonal_to_vendor_type(self, client_settings: UiPathBaseSettings):
+        chat = _build(
+            client_settings,
+            vendor_type=VendorType.ANTHROPIC,
+            api_flavor=ApiFlavor.ANTHROPIC_MESSAGES,
+        )
+        assert chat.api_config.api_flavor == ApiFlavor.ANTHROPIC_MESSAGES
+        assert isinstance(chat._anthropic_client, Anthropic)
+
+
+class TestVendorDerivedDefaultsUnchanged:
+    """Regression guard: omitting api_flavor preserves the prior vendor-derived behavior."""
+
+    def test_bedrock_without_flavor_uses_invoke_and_anthropic_bedrock(
+        self, client_settings: UiPathBaseSettings
+    ):
+        chat = _build(client_settings, vendor_type=VendorType.AWSBEDROCK)
+        assert chat.api_config.api_flavor == ApiFlavor.INVOKE
+        assert isinstance(chat._anthropic_client, AnthropicBedrock)
+        assert isinstance(chat._async_anthropic_client, AsyncAnthropicBedrock)
+
+    def test_anthropic_vendor_defaults_to_anthropic_client(
+        self, client_settings: UiPathBaseSettings
+    ):
+        chat = _build(client_settings, vendor_type=VendorType.ANTHROPIC)
+        assert isinstance(chat._anthropic_client, Anthropic)
+        assert not isinstance(chat._anthropic_client, AnthropicBedrock)

tests/langchain/features/test_factory_function.py

@@ -6,7 +6,7 @@
 from uipath_langchain_client.factory import get_chat_model, get_embedding_model
 
 from tests.langchain.conftest import COMPLETION_MODEL_NAMES, EMBEDDING_MODEL_NAMES
-from uipath.llm_client.settings import ApiFlavor, UiPathBaseSettings
+from uipath.llm_client.settings import ApiFlavor, UiPathBaseSettings, VendorType
 
 
 @pytest.mark.vcr
@@ -333,3 +333,49 @@ def test_no_kwarg_keeps_settings_value(self, monkeypatch: pytest.MonkeyPatch):
         )
         assert captured["settings"] is original
         original.model_copy.assert_not_called()
+
+
+class TestFactoryAnthropicMessagesRouting:
+    """AwsBedrock + ``apiFlavor=AnthropicMessages`` routes to ``UiPathChatAnthropic``
+    configured for the native Anthropic Messages wire format over the Bedrock
+    passthrough URL (not the Bedrock Converse/Invoke clients)."""
+
+    def _capture(
+        self,
+        monkeypatch: pytest.MonkeyPatch,
+        model_info: dict,
+        **factory_kwargs,
+    ) -> dict:
+        settings = MagicMock()
+        settings.get_model_info.return_value = model_info
+        captured: dict = {}
+
+        class _StubModel:
+            def __init__(self, **kwargs):
+                captured.update(kwargs)
+
+        monkeypatch.setattr(
+            "uipath_langchain_client.clients.anthropic.chat_models.UiPathChatAnthropic",
+            _StubModel,
+        )
+        get_chat_model(
+            model_name=model_info["modelName"],
+            client_settings=settings,
+            **factory_kwargs,
+        )
+        return captured
+
+    def test_anthropic_messages_routes_to_uipath_chat_anthropic(
+        self, monkeypatch: pytest.MonkeyPatch
+    ):
+        captured = self._capture(
+            monkeypatch,
+            {
+                "modelName": "anthropic.claude-sonnet-4-6",
+                "vendor": "AwsBedrock",
+                "apiFlavor": "AnthropicMessages",
+                "modelFamily": "AnthropicClaude",
+            },
+        )
+        assert captured["vendor_type"] == VendorType.AWSBEDROCK
+        assert captured["api_flavor"] == ApiFlavor.ANTHROPIC_MESSAGES