From fc9988b686ba23fd8da6c469e77380f620e87622 Mon Sep 17 00:00:00 2001
From: Harshit Jain <48647625+Harshit28j@users.noreply.github.com>
Date: Mon, 19 Jan 2026 19:48:02 +0530
Subject: [PATCH] fix/bedrock-inconsistent-postcall-hook (#19151)

* fix/bedrock-inconsistent-postcall-hook

* Add condition check to avoid multiple validation
---
 .../guardrail_hooks/bedrock_guardrails.py     | 110 +++++++++++++-----
 1 file changed, 83 insertions(+), 27 deletions(-)

diff --git a/litellm/proxy/guardrails/guardrail_hooks/bedrock_guardrails.py b/litellm/proxy/guardrails/guardrail_hooks/bedrock_guardrails.py
index 59032189438..d3e8a74945f 100644
--- a/litellm/proxy/guardrails/guardrail_hooks/bedrock_guardrails.py
+++ b/litellm/proxy/guardrails/guardrail_hooks/bedrock_guardrails.py
@@ -893,15 +893,53 @@ class BedrockGuardrail(CustomGuardrail, BaseAWSLLM):
                 return
 
         #########################################################
-        ########## 1. Make parallel Bedrock API requests ##########
+        ########## 1. Make Bedrock API requests ##########
         #########################################################
+        # Import asyncio for parallel execution
+        import asyncio
+
+        # Determine if INPUT validation is needed in post_call
+        # Skip INPUT validation if pre_call or during_call is already enabled
+        # (to avoid redundant validation - those hooks would have already validated INPUT)
+        should_validate_input = not (
+            self._event_hook_is_event_type(GuardrailEventHooks.pre_call)
+            or self._event_hook_is_event_type(GuardrailEventHooks.during_call)
+        )
+
         output_content_bedrock: Optional[Union[BedrockGuardrailResponse, str]] = None
-        try:
-            output_content_bedrock = await self.make_bedrock_api_request(
+
+        if should_validate_input:
+            # Prepare input messages (with optional filtering for latest role message)
+            input_filter = self._prepare_guardrail_messages_for_role(
+                messages=new_messages
+            )
+            input_messages = input_filter.payload_messages or new_messages
+
+            # Create tasks for parallel execution of both INPUT and OUTPUT validation
+            input_task = self.make_bedrock_api_request(
+                source="INPUT",
+                messages=input_messages,
+                request_data=data,
+            )
+            output_task = self.make_bedrock_api_request(
                 source="OUTPUT", response=response, request_data=data
             )
-        except GuardrailInterventionNormalStringError as e:
-            output_content_bedrock = e.message
+
+            # Execute both requests in parallel
+            try:
+                _, output_content_bedrock = await asyncio.gather(
+                    input_task, output_task
+                )
+            except GuardrailInterventionNormalStringError as e:
+                output_content_bedrock = e.message
+        else:
+            # Only run OUTPUT validation (INPUT was already validated in pre_call or during_call)
+            try:
+                output_content_bedrock = await self.make_bedrock_api_request(
+                    source="OUTPUT", response=response, request_data=data
+                )
+            except GuardrailInterventionNormalStringError as e:
+                output_content_bedrock = e.message
 
         #########################################################
         ########## 2. Apply masking to response with output guardrail response ##########
@@ -910,7 +948,7 @@ class BedrockGuardrail(CustomGuardrail, BaseAWSLLM):
             response = self.create_guardrail_blocked_response(
                 response=output_content_bedrock
             )
-        else:
+        elif output_content_bedrock is not None:
             self._apply_masking_to_response(
                 response=response,
                 bedrock_guardrail_response=output_content_bedrock,
@@ -997,36 +1035,54 @@ class BedrockGuardrail(CustomGuardrail, BaseAWSLLM):
         )
         if isinstance(assembled_model_response, ModelResponse):
             ####################################################################
-            ########## 1. Make parallel Bedrock Apply Guardrail API requests ##########
+            ########## 1. Make Bedrock Apply Guardrail API requests ##########
 
             # Bedrock will raise an exception if this violates the guardrail policy
             ###################################################################
-            # Create tasks for parallel execution
-            input_filter = self._prepare_guardrail_messages_for_role(
-                messages=request_data.get("messages")
+            # Determine if INPUT validation is needed in post_call
+            # Skip INPUT validation if pre_call or during_call is already enabled
+            # (to avoid redundant validation - those hooks would have already validated INPUT)
+            should_validate_input = not (
+                self._event_hook_is_event_type(GuardrailEventHooks.pre_call)
+                or self._event_hook_is_event_type(GuardrailEventHooks.during_call)
             )
-            input_messages = input_filter.payload_messages or request_data.get(
-                "messages"
-            )
-            input_task = self.make_bedrock_api_request(
-                source="INPUT",
-                messages=input_messages,
-                request_data=request_data,
-            )  # Only input messages
+
             output_guardrail_response: Optional[
                 Union[BedrockGuardrailResponse, str]
             ] = None
-            output_task = self.make_bedrock_api_request(
-                source="OUTPUT", response=assembled_model_response
-            )  # Only response
 
-            # Execute both requests in parallel
-            try:
-                _, output_guardrail_response = await asyncio.gather(
-                    input_task, output_task
+            if should_validate_input:
+                # Create tasks for parallel execution
+                input_filter = self._prepare_guardrail_messages_for_role(
+                    messages=request_data.get("messages")
                 )
-            except GuardrailInterventionNormalStringError as e:
-                output_guardrail_response = e.message
+                input_messages = input_filter.payload_messages or request_data.get(
+                    "messages"
+                )
+                input_task = self.make_bedrock_api_request(
+                    source="INPUT",
+                    messages=input_messages,
+                    request_data=request_data,
+                )  # Only input messages
+                output_task = self.make_bedrock_api_request(
+                    source="OUTPUT", response=assembled_model_response
+                )  # Only response
+
+                # Execute both requests in parallel
+                try:
+                    _, output_guardrail_response = await asyncio.gather(
+                        input_task, output_task
+                    )
+                except GuardrailInterventionNormalStringError as e:
+                    output_guardrail_response = e.message
+            else:
+                # Only run OUTPUT validation (INPUT was already validated in pre_call or during_call)
+                try:
+                    output_guardrail_response = await self.make_bedrock_api_request(
+                        source="OUTPUT", response=assembled_model_response
+                    )
+                except GuardrailInterventionNormalStringError as e:
+                    output_guardrail_response = e.message
 
             #########################################################################
             ########## 2. Apply masking to response with output guardrail response ##########