diff --git a/litellm/main.py b/litellm/main.py
index 5ecfcf1db..ddeff3414 100644
--- a/litellm/main.py
+++ b/litellm/main.py
@@ -1835,7 +1835,7 @@ def embedding(
     try:
         response = None
         logging = litellm_logging_obj
-        logging.update_environment_variables(model=model, user="", optional_params=optional_params, litellm_params={"timeout": timeout, "azure": azure, "litellm_call_id": litellm_call_id, "logger_fn": logger_fn, "proxy_server_request": proxy_server_request, "model_info": model_info, "metadata": metadata, "aembedding": aembedding})
+        logging.update_environment_variables(model=model, user="", optional_params=optional_params, litellm_params={"timeout": timeout, "azure": azure, "litellm_call_id": litellm_call_id, "logger_fn": logger_fn, "proxy_server_request": proxy_server_request, "model_info": model_info, "metadata": metadata, "aembedding": aembedding, "preset_cache_key": None, "stream_response": {}})
         if azure == True or custom_llm_provider == "azure":
             # azure configs
             api_type = get_secret("AZURE_API_TYPE") or "azure"
diff --git a/litellm/router.py b/litellm/router.py
index 1721a381b..c01c7d42e 100644
--- a/litellm/router.py
+++ b/litellm/router.py
@@ -313,8 +313,8 @@ class Router:
                   **kwargs) -> Union[List[float], None]:
         # pick the one that is available (lowest TPM/RPM)
         deployment = self.get_available_deployment(model=model, input=input, specific_deployment=kwargs.pop("specific_deployment", None))
-        kwargs.setdefault("metadata", {}).update({"deployment": deployment["litellm_params"]["model"]})
-        kwargs["model_info"] = deployment.get("model_info", {})
+        kwargs.setdefault("model_info", {})
+        kwargs.setdefault("metadata", {}).update({"model_group": model, "deployment": deployment["litellm_params"]["model"]}) # [TODO]: move to using async_function_with_fallbacks
         data = deployment["litellm_params"].copy()
         for k, v in self.default_litellm_params.items(): 
             if k not in data: # prioritize model-specific params > default router params 
@@ -339,7 +339,7 @@ class Router:
                          **kwargs) -> Union[List[float], None]:
         # pick the one that is available (lowest TPM/RPM)
         deployment = self.get_available_deployment(model=model, input=input, specific_deployment=kwargs.pop("specific_deployment", None))
-        kwargs.setdefault("metadata", {}).update({"deployment": deployment["litellm_params"]["model"]})
+        kwargs.setdefault("metadata", {}).update({"model_group": model, "deployment": deployment["litellm_params"]["model"]})
         data = deployment["litellm_params"].copy()
         kwargs["model_info"] = deployment.get("model_info", {})
         for k, v in self.default_litellm_params.items(): 
diff --git a/litellm/tests/test_custom_callback_input.py b/litellm/tests/test_custom_callback_input.py
index 865ed4040..fa484dea0 100644
--- a/litellm/tests/test_custom_callback_input.py
+++ b/litellm/tests/test_custom_callback_input.py
@@ -22,8 +22,7 @@ from litellm.integrations.custom_logger import CustomLogger
 
 # Test interfaces
 ## 1. litellm.completion() + litellm.embeddings()
-## 2. router.completion() + router.embeddings() 
-## 3. proxy.completions + proxy.embeddings 
+## refer to test_custom_callback_input_router.py for the router +  proxy tests
 
 class CompletionCustomHandler(CustomLogger): # https://docs.litellm.ai/docs/observability/custom_callback#callback-class
     """
@@ -577,4 +576,4 @@ async def test_async_embedding_bedrock():
     except Exception as e: 
         pytest.fail(f"An exception occurred: {str(e)}")
 
-asyncio.run(test_async_embedding_bedrock())
\ No newline at end of file
+# asyncio.run(test_async_embedding_bedrock())
\ No newline at end of file
diff --git a/litellm/tests/test_custom_callback_router.py b/litellm/tests/test_custom_callback_router.py
new file mode 100644
index 000000000..38683bc2d
--- /dev/null
+++ b/litellm/tests/test_custom_callback_router.py
@@ -0,0 +1,398 @@
+### What this tests ####
+## This test asserts the type of data passed into each method of the custom callback handler
+import sys, os, time, inspect, asyncio, traceback
+from datetime import datetime
+import pytest
+sys.path.insert(0, os.path.abspath('../..'))
+from typing import Optional, Literal, List
+from litellm import Router
+import litellm
+from litellm.integrations.custom_logger import CustomLogger
+
+# Test Scenarios (test across completion, streaming, embedding)
+## 1: Pre-API-Call
+## 2: Post-API-Call
+## 3: On LiteLLM Call success
+## 4: On LiteLLM Call failure
+## fallbacks 
+## retries 
+
+# Test cases 
+## 1. Simple Azure OpenAI acompletion + streaming call 
+## 2. Simple Azure OpenAI aembedding call 
+## 3. Azure OpenAI acompletion + streaming  call with retries
+## 4. Azure OpenAI aembedding call with retries
+## 5. Azure OpenAI acompletion + streaming call with fallbacks
+## 6. Azure OpenAI aembedding call with fallbacks
+
+# Test interfaces
+## 1. router.completion() + router.embeddings() 
+## 2. proxy.completions + proxy.embeddings 
+
+class CompletionCustomHandler(CustomLogger): # https://docs.litellm.ai/docs/observability/custom_callback#callback-class
+    """
+    The set of expected inputs to a custom handler for a 
+    """
+    # Class variables or attributes
+    def __init__(self):
+        self.errors = []
+        self.states: Optional[List[Literal["sync_pre_api_call", "async_pre_api_call", "post_api_call", "sync_stream", "async_stream", "sync_success", "async_success", "sync_failure", "async_failure"]]] = []
+
+    def log_pre_api_call(self, model, messages, kwargs): 
+        try: 
+            print(f'received kwargs in pre-input: {kwargs}')
+            self.states.append("sync_pre_api_call")
+            ## MODEL
+            assert isinstance(model, str)
+            ## MESSAGES
+            assert isinstance(messages, list)
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list) 
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            ### ROUTER-SPECIFIC KWARGS
+            assert isinstance(kwargs["litellm_params"]["metadata"], dict)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["model_group"], str)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["deployment"], str)
+            assert isinstance(kwargs["litellm_params"]["model_info"], dict)
+            assert isinstance(kwargs["litellm_params"]["model_info"]["id"], str)
+            assert isinstance(kwargs["litellm_params"]["proxy_server_request"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["preset_cache_key"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["stream_response"], dict)
+        except Exception as e: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+    def log_post_api_call(self, kwargs, response_obj, start_time, end_time): 
+        try:
+            self.states.append("post_api_call")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert end_time == None
+            ## RESPONSE OBJECT 
+            assert response_obj == None
+            ## KWARGS 
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert isinstance(kwargs['input'], (list, dict, str))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper)) or inspect.iscoroutine(kwargs['original_response']) or inspect.isasyncgen(kwargs['original_response'])
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+            ### ROUTER-SPECIFIC KWARGS
+            assert isinstance(kwargs["litellm_params"]["metadata"], dict)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["model_group"], str)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["deployment"], str)
+            assert isinstance(kwargs["litellm_params"]["model_info"], dict)
+            assert isinstance(kwargs["litellm_params"]["model_info"]["id"], str)
+            assert isinstance(kwargs["litellm_params"]["proxy_server_request"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["preset_cache_key"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["stream_response"], dict)
+        except: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+    
+    async def async_log_stream_event(self, kwargs, response_obj, start_time, end_time):
+        try:
+            self.states.append("async_stream")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert isinstance(end_time, datetime)
+            ## RESPONSE OBJECT 
+            assert isinstance(response_obj, litellm.ModelResponse)
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list) and isinstance(kwargs['messages'][0], dict)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert (isinstance(kwargs['input'], list) and isinstance(kwargs['input'][0], dict)) or isinstance(kwargs['input'], (dict, str))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper)) or inspect.isasyncgen(kwargs['original_response']) or inspect.iscoroutine(kwargs['original_response'])
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+        except: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+    def log_success_event(self, kwargs, response_obj, start_time, end_time): 
+        try:
+            self.states.append("sync_success")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert isinstance(end_time, datetime)
+            ## RESPONSE OBJECT 
+            assert isinstance(response_obj, litellm.ModelResponse)
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list) and isinstance(kwargs['messages'][0], dict)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert (isinstance(kwargs['input'], list) and isinstance(kwargs['input'][0], dict)) or isinstance(kwargs['input'], (dict, str))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper))
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+        except:
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+    def log_failure_event(self, kwargs, response_obj, start_time, end_time): 
+        try:
+            self.states.append("sync_failure")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert isinstance(end_time, datetime)
+            ## RESPONSE OBJECT 
+            assert response_obj == None
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list) and isinstance(kwargs['messages'][0], dict)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert (isinstance(kwargs['input'], list) and isinstance(kwargs['input'][0], dict)) or isinstance(kwargs['input'], (dict, str))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper)) or kwargs["original_response"] == None
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+        except: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+    
+    async def async_log_pre_api_call(self, model, messages, kwargs):
+        try: 
+            """
+            No-op. 
+            Not implemented yet. 
+            """
+            pass
+        except Exception as e: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+    async def async_log_success_event(self, kwargs, response_obj, start_time, end_time):
+        try: 
+            self.states.append("async_success")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert isinstance(end_time, datetime)
+            ## RESPONSE OBJECT 
+            assert isinstance(response_obj, (litellm.ModelResponse, litellm.EmbeddingResponse))
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert isinstance(kwargs['input'], (list, dict, str))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper)) or inspect.isasyncgen(kwargs['original_response']) or inspect.iscoroutine(kwargs['original_response'])
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+            ### ROUTER-SPECIFIC KWARGS
+            assert isinstance(kwargs["litellm_params"]["metadata"], dict)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["model_group"], str)
+            assert isinstance(kwargs["litellm_params"]["metadata"]["deployment"], str)
+            assert isinstance(kwargs["litellm_params"]["model_info"], dict)
+            assert isinstance(kwargs["litellm_params"]["model_info"]["id"], str)
+            assert isinstance(kwargs["litellm_params"]["proxy_server_request"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["preset_cache_key"], Optional[str])
+            assert isinstance(kwargs["litellm_params"]["stream_response"], dict)
+        except: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+    async def async_log_failure_event(self, kwargs, response_obj, start_time, end_time):
+        try:
+            print(f"received original response: {kwargs['original_response']}")
+            self.states.append("async_failure")
+            ## START TIME 
+            assert isinstance(start_time, datetime)
+            ## END TIME 
+            assert isinstance(end_time, datetime)
+            ## RESPONSE OBJECT 
+            assert response_obj == None
+            ## KWARGS
+            assert isinstance(kwargs['model'], str)
+            assert isinstance(kwargs['messages'], list)
+            assert isinstance(kwargs['optional_params'], dict)
+            assert isinstance(kwargs['litellm_params'], dict) 
+            assert isinstance(kwargs['start_time'], Optional[datetime])
+            assert isinstance(kwargs['stream'], bool)
+            assert isinstance(kwargs['user'], Optional[str])
+            assert isinstance(kwargs['input'], (list, str, dict))
+            assert isinstance(kwargs['api_key'], Optional[str])
+            assert isinstance(kwargs['original_response'], (str, litellm.CustomStreamWrapper)) or inspect.isasyncgen(kwargs['original_response']) or inspect.iscoroutine(kwargs['original_response']) or kwargs['original_response'] == None
+            assert isinstance(kwargs['additional_args'], Optional[dict])
+            assert isinstance(kwargs['log_event_type'], str) 
+        except: 
+            print(f"Assertion Error: {traceback.format_exc()}")
+            self.errors.append(traceback.format_exc())
+
+# Simple Azure OpenAI call 
+## COMPLETION
+@pytest.mark.asyncio
+async def test_async_chat_azure():
+    try: 
+        customHandler = CompletionCustomHandler()
+        customHandler_streaming = CompletionCustomHandler()
+        customHandler_failure = CompletionCustomHandler()
+        litellm.callbacks = [customHandler]
+        model_list = [
+                    { 
+                        "model_name": "gpt-3.5-turbo", # openai model name 
+                        "litellm_params": { # params for litellm completion/embedding call 
+                            "model": "azure/chatgpt-v-2", 
+                            "api_key": os.getenv("AZURE_API_KEY"),
+                            "api_version": os.getenv("AZURE_API_VERSION"),
+                            "api_base": os.getenv("AZURE_API_BASE")
+                        },
+                        "tpm": 240000,
+                        "rpm": 1800
+                    },
+                ]
+        router = Router(model_list=model_list) # type: ignore
+        response = await router.acompletion(model="gpt-3.5-turbo",
+                                messages=[{
+                                    "role": "user",
+                                    "content": "Hi 👋 - i'm openai"
+                                }])
+        await asyncio.sleep(2)
+        assert len(customHandler.errors) == 0
+        assert len(customHandler.states) == 3 # pre, post, success
+        # streaming 
+        litellm.callbacks = [customHandler_streaming]
+        router2 = Router(model_list=model_list) # type: ignore
+        response = await router2.acompletion(model="gpt-3.5-turbo",
+                                messages=[{
+                                    "role": "user",
+                                    "content": "Hi 👋 - i'm openai"
+                                }],
+                                stream=True)
+        async for chunk in response: 
+            continue
+        await asyncio.sleep(1)
+        print(f"customHandler.states: {customHandler_streaming.states}")
+        assert len(customHandler_streaming.errors) == 0
+        assert len(customHandler_streaming.states) >= 4 # pre, post, stream (multiple times), success
+        # failure 
+        model_list = [
+                    { 
+                        "model_name": "gpt-3.5-turbo", # openai model name 
+                        "litellm_params": { # params for litellm completion/embedding call 
+                            "model": "azure/chatgpt-v-2", 
+                            "api_key": "my-bad-key",
+                            "api_version": os.getenv("AZURE_API_VERSION"),
+                            "api_base": os.getenv("AZURE_API_BASE")
+                        },
+                        "tpm": 240000,
+                        "rpm": 1800
+                    },
+                ]
+        litellm.callbacks = [customHandler_failure]
+        router3 = Router(model_list=model_list) # type: ignore
+        try: 
+            response = await router3.acompletion(model="gpt-3.5-turbo",
+                                    messages=[{
+                                        "role": "user",
+                                        "content": "Hi 👋 - i'm openai"
+                                    }])
+            print(f"response in router3 acompletion: {response}")
+        except:
+            pass
+        await asyncio.sleep(1)
+        print(f"customHandler.states: {customHandler_failure.states}")
+        assert len(customHandler_failure.errors) == 0
+        assert len(customHandler_failure.states) == 3 # pre, post, failure
+        assert "async_failure" in customHandler_failure.states
+    except Exception as e: 
+        print(f"Assertion Error: {traceback.format_exc()}")
+        pytest.fail(f"An exception occurred - {str(e)}")
+# asyncio.run(test_async_chat_azure())
+## EMBEDDING
+async def test_async_embedding_azure():
+    try: 
+        customHandler = CompletionCustomHandler()
+        customHandler_failure = CompletionCustomHandler()
+        litellm.callbacks = [customHandler]
+        model_list = [
+                    { 
+                        "model_name": "azure-embedding-model", # openai model name 
+                        "litellm_params": { # params for litellm completion/embedding call 
+                            "model": "azure/azure-embedding-model", 
+                            "api_key": os.getenv("AZURE_API_KEY"),
+                            "api_version": os.getenv("AZURE_API_VERSION"),
+                            "api_base": os.getenv("AZURE_API_BASE")
+                        },
+                        "tpm": 240000,
+                        "rpm": 1800
+                    },
+                ]
+        router = Router(model_list=model_list) # type: ignore
+        response = await router.aembedding(model="azure-embedding-model",
+                                input=["hello from litellm!"])
+        await asyncio.sleep(2)
+        assert len(customHandler.errors) == 0
+        assert len(customHandler.states) == 3 # pre, post, success
+        # failure 
+        model_list = [
+                    { 
+                        "model_name": "azure-embedding-model", # openai model name 
+                        "litellm_params": { # params for litellm completion/embedding call 
+                            "model": "azure/azure-embedding-model", 
+                            "api_key": "my-bad-key",
+                            "api_version": os.getenv("AZURE_API_VERSION"),
+                            "api_base": os.getenv("AZURE_API_BASE")
+                        },
+                        "tpm": 240000,
+                        "rpm": 1800
+                    },
+                ]
+        litellm.callbacks = [customHandler_failure]
+        router3 = Router(model_list=model_list) # type: ignore
+        try: 
+            response = await router3.aembedding(model="azure-embedding-model",
+                                input=["hello from litellm!"])
+            print(f"response in router3 aembedding: {response}")
+        except:
+            pass
+        await asyncio.sleep(1)
+        print(f"customHandler.states: {customHandler_failure.states}")
+        assert len(customHandler_failure.errors) == 0
+        assert len(customHandler_failure.states) == 3 # pre, post, failure
+        assert "async_failure" in customHandler_failure.states
+    except Exception as e: 
+        print(f"Assertion Error: {traceback.format_exc()}")
+        pytest.fail(f"An exception occurred - {str(e)}")
+asyncio.run(test_async_embedding_azure())
+# Azure OpenAI call w/ Retries
+## COMPLETION
+## EMBEDDING
+
+# Azure OpenAI call w/ fallbacks
+## COMPLETION
+## EMBEDDING