feat: decouple Strands ContentBlock and BedrockModel (strands-agents#836)

Author: dbschmigelski

src/strands/models/bedrock.py

@@ -18,13 +18,13 @@
 
 from ..event_loop import streaming
 from ..tools import convert_pydantic_to_tool_spec
-from ..types.content import ContentBlock, Message, Messages
+from ..types.content import ContentBlock, Messages
 from ..types.exceptions import (
     ContextWindowOverflowException,
     ModelThrottledException,
 )
 from ..types.streaming import CitationsDelta, StreamEvent
-from ..types.tools import ToolChoice, ToolResult, ToolSpec
+from ..types.tools import ToolChoice, ToolSpec
 from ._validation import validate_config_keys
 from .model import Model
 
@@ -185,17 +185,6 @@ def get_config(self) -> BedrockConfig:
         """
         return self.config
 
-    def _should_include_tool_result_status(self) -> bool:
-        """Determine whether to include tool result status based on current config."""
-        include_status = self.config.get("include_tool_result_status", "auto")
-
-        if include_status is True:
-            return True
-        elif include_status is False:
-            return False
-        else:  # "auto"
-            return any(model in self.config["model_id"] for model in _MODELS_INCLUDE_STATUS)
-
     def format_request(
         self,
         messages: Messages,
@@ -281,14 +270,12 @@ def format_request(
             ),
         }
 
-    def _format_bedrock_messages(self, messages: Messages) -> Messages:
+    def _format_bedrock_messages(self, messages: Messages) -> list[dict[str, Any]]:
         """Format messages for Bedrock API compatibility.
 
         This function ensures messages conform to Bedrock's expected format by:
         - Filtering out SDK_UNKNOWN_MEMBER content blocks
-        - Cleaning tool result content blocks by removing additional fields that may be
-          useful for retaining information in hooks but would cause Bedrock validation
-          exceptions when presented with unexpected fields
+        - Eagerly filtering content blocks to only include Bedrock-supported fields
         - Ensuring all message content blocks are properly formatted for the Bedrock API
 
         Args:
@@ -298,17 +285,19 @@ def _format_bedrock_messages(self, messages: Messages) -> Messages:
             Messages formatted for Bedrock API compatibility
 
         Note:
-            Bedrock will throw validation exceptions when presented with additional
-            unexpected fields in tool result blocks.
-            https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ToolResultBlock.html
+            Unlike other APIs that ignore unknown fields, Bedrock only accepts a strict
+            subset of fields for each content block type and throws validation exceptions
+            when presented with unexpected fields. Therefore, we must eagerly filter all
+            content blocks to remove any additional fields before sending to Bedrock.
+            https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ContentBlock.html
         """
-        cleaned_messages = []
+        cleaned_messages: list[dict[str, Any]] = []
 
         filtered_unknown_members = False
         dropped_deepseek_reasoning_content = False
 
         for message in messages:
-            cleaned_content: list[ContentBlock] = []
+            cleaned_content: list[dict[str, Any]] = []
 
             for content_block in message["content"]:
                 # Filter out SDK_UNKNOWN_MEMBER content blocks
@@ -322,33 +311,13 @@ def _format_bedrock_messages(self, messages: Messages) -> Messages:
                     dropped_deepseek_reasoning_content = True
                     continue
 
-                if "toolResult" in content_block:
-                    # Create a new content block with only the cleaned toolResult
-                    tool_result: ToolResult = content_block["toolResult"]
+                # Format content blocks for Bedrock API compatibility
+                formatted_content = self._format_request_message_content(content_block)
+                cleaned_content.append(formatted_content)
 
-                    if self._should_include_tool_result_status():
-                        # Include status field
-                        cleaned_tool_result = ToolResult(
-                            content=tool_result["content"],
-                            toolUseId=tool_result["toolUseId"],
-                            status=tool_result["status"],
-                        )
-                    else:
-                        # Remove status field
-                        cleaned_tool_result = ToolResult(  # type: ignore[typeddict-item]
-                            toolUseId=tool_result["toolUseId"], content=tool_result["content"]
-                        )
-
-                    cleaned_block: ContentBlock = {"toolResult": cleaned_tool_result}
-                    cleaned_content.append(cleaned_block)
-                else:
-                    # Keep other content blocks as-is
-                    cleaned_content.append(content_block)
-
-            # Create new message with cleaned content (skip if empty for DeepSeek)
+            # Create new message with cleaned content (skip if empty)
             if cleaned_content:
-                cleaned_message: Message = Message(content=cleaned_content, role=message["role"])
-                cleaned_messages.append(cleaned_message)
+                cleaned_messages.append({"content": cleaned_content, "role": message["role"]})
 
         if filtered_unknown_members:
             logger.warning(
@@ -361,6 +330,184 @@ def _format_bedrock_messages(self, messages: Messages) -> Messages:
 
         return cleaned_messages
 
+    def _should_include_tool_result_status(self) -> bool:
+        """Determine whether to include tool result status based on current config."""
+        include_status = self.config.get("include_tool_result_status", "auto")
+
+        if include_status is True:
+            return True
+        elif include_status is False:
+            return False
+        else:  # "auto"
+            return any(model in self.config["model_id"] for model in _MODELS_INCLUDE_STATUS)
+
+    def _format_request_message_content(self, content: ContentBlock) -> dict[str, Any]:
+        """Format a Bedrock content block.
+
+        Bedrock strictly validates content blocks and throws exceptions for unknown fields.
+        This function extracts only the fields that Bedrock supports for each content type.
+
+        Args:
+            content: Content block to format.
+
+        Returns:
+            Bedrock formatted content block.
+
+        Raises:
+            TypeError: If the content block type is not supported by Bedrock.
+        """
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_CachePointBlock.html
+        if "cachePoint" in content:
+            return {"cachePoint": {"type": content["cachePoint"]["type"]}}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_DocumentBlock.html
+        if "document" in content:
+            document = content["document"]
+            result: dict[str, Any] = {}
+
+            # Handle required fields (all optional due to total=False)
+            if "name" in document:
+                result["name"] = document["name"]
+            if "format" in document:
+                result["format"] = document["format"]
+
+            # Handle source
+            if "source" in document:
+                result["source"] = {"bytes": document["source"]["bytes"]}
+
+            # Handle optional fields
+            if "citations" in document and document["citations"] is not None:
+                result["citations"] = {"enabled": document["citations"]["enabled"]}
+            if "context" in document:
+                result["context"] = document["context"]
+
+            return {"document": result}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_GuardrailConverseContentBlock.html
+        if "guardContent" in content:
+            guard = content["guardContent"]
+            guard_text = guard["text"]
+            result = {"text": {"text": guard_text["text"], "qualifiers": guard_text["qualifiers"]}}
+            return {"guardContent": result}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ImageBlock.html
+        if "image" in content:
+            image = content["image"]
+            source = image["source"]
+            formatted_source = {}
+            if "bytes" in source:
+                formatted_source = {"bytes": source["bytes"]}
+            result = {"format": image["format"], "source": formatted_source}
+            return {"image": result}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ReasoningContentBlock.html
+        if "reasoningContent" in content:
+            reasoning = content["reasoningContent"]
+            result = {}
+
+            if "reasoningText" in reasoning:
+                reasoning_text = reasoning["reasoningText"]
+                result["reasoningText"] = {}
+                if "text" in reasoning_text:
+                    result["reasoningText"]["text"] = reasoning_text["text"]
+                # Only include signature if truthy (avoid empty strings)
+                if reasoning_text.get("signature"):
+                    result["reasoningText"]["signature"] = reasoning_text["signature"]
+
+            if "redactedContent" in reasoning:
+                result["redactedContent"] = reasoning["redactedContent"]
+
+            return {"reasoningContent": result}
+
+        # Pass through text and other simple content types
+        if "text" in content:
+            return {"text": content["text"]}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ToolResultBlock.html
+        if "toolResult" in content:
+            tool_result = content["toolResult"]
+            formatted_content: list[dict[str, Any]] = []
+            for tool_result_content in tool_result["content"]:
+                if "json" in tool_result_content:
+                    # Handle json field since not in ContentBlock but valid in ToolResultContent
+                    formatted_content.append({"json": tool_result_content["json"]})
+                else:
+                    formatted_content.append(
+                        self._format_request_message_content(cast(ContentBlock, tool_result_content))
+                    )
+
+            result = {
+                "content": formatted_content,
+                "toolUseId": tool_result["toolUseId"],
+            }
+            if "status" in tool_result and self._should_include_tool_result_status():
+                result["status"] = tool_result["status"]
+            return {"toolResult": result}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_ToolUseBlock.html
+        if "toolUse" in content:
+            tool_use = content["toolUse"]
+            return {
+                "toolUse": {
+                    "input": tool_use["input"],
+                    "name": tool_use["name"],
+                    "toolUseId": tool_use["toolUseId"],
+                }
+            }
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_VideoBlock.html
+        if "video" in content:
+            video = content["video"]
+            source = video["source"]
+            formatted_source = {}
+            if "bytes" in source:
+                formatted_source = {"bytes": source["bytes"]}
+            result = {"format": video["format"], "source": formatted_source}
+            return {"video": result}
+
+        # https://docs.aws.amazon.com/bedrock/latest/APIReference/API_runtime_CitationsContentBlock.html
+        if "citationsContent" in content:
+            citations = content["citationsContent"]
+            result = {}
+
+            if "citations" in citations:
+                result["citations"] = []
+                for citation in citations["citations"]:
+                    filtered_citation: dict[str, Any] = {}
+                    if "location" in citation:
+                        location = citation["location"]
+                        filtered_location = {}
+                        # Filter location fields to only include Bedrock-supported ones
+                        if "documentIndex" in location:
+                            filtered_location["documentIndex"] = location["documentIndex"]
+                        if "start" in location:
+                            filtered_location["start"] = location["start"]
+                        if "end" in location:
+                            filtered_location["end"] = location["end"]
+                        filtered_citation["location"] = filtered_location
+                    if "sourceContent" in citation:
+                        filtered_source_content: list[dict[str, Any]] = []
+                        for source_content in citation["sourceContent"]:
+                            if "text" in source_content:
+                                filtered_source_content.append({"text": source_content["text"]})
+                        if filtered_source_content:
+                            filtered_citation["sourceContent"] = filtered_source_content
+                    if "title" in citation:
+                        filtered_citation["title"] = citation["title"]
+                    result["citations"].append(filtered_citation)
+
+            if "content" in citations:
+                filtered_content: list[dict[str, Any]] = []
+                for generated_content in citations["content"]:
+                    if "text" in generated_content:
+                        filtered_content.append({"text": generated_content["text"]})
+                if filtered_content:
+                    result["content"] = filtered_content
+
+            return {"citationsContent": result}
+
+        raise TypeError(f"content_type=<{next(iter(content))}> | unsupported type")
+
     def _has_blocked_guardrail(self, guardrail_data: dict[str, Any]) -> bool:
         """Check if guardrail data contains any blocked policies.