Merge pull request #24368 from Chesars/fix/bedrock-converse-content-block-ordering

fix(bedrock): sort assistant content blocks so text precedes toolUse

litellm/litellm_core_utils/prompt_templates/factory.py

@@ -4051,6 +4051,36 @@ def _deduplicate_bedrock_tool_content(
     return _deduplicate_bedrock_content_blocks(tool_content, "toolResult")
 
 
+def _sort_bedrock_assistant_content_blocks(
+    blocks: List[BedrockContentBlock],
+) -> List[BedrockContentBlock]:
+    """
+    Sort assistant content blocks so that ``text`` blocks appear before
+    ``toolUse`` blocks.
+
+    Bedrock requires all ``text`` blocks to precede any ``toolUse`` blocks
+    within an assistant message.  When the Responses API converts
+    function_call items before message items, the resulting ``toolUse``
+    blocks can end up before ``text`` blocks, causing Bedrock to reject
+    the request with a 400 error because the ``toolUse`` → ``toolResult``
+    pairing is broken by the intervening ``text`` block.
+
+    Sort order (stable):
+      0 - reasoningContent
+      1 - text / image / document / video / other non-tool blocks
+      2 - toolUse
+    """
+
+    def _sort_key(block: BedrockContentBlock) -> int:
+        if "reasoningContent" in block:
+            return 0
+        if "toolUse" in block:
+            return 2
+        return 1
+
+    return sorted(blocks, key=_sort_key)
+
+
 def _insert_assistant_continue_message(
     messages: List[BedrockMessageBlock],
     assistant_continue_message: Optional[
@@ -4642,6 +4672,9 @@ class BedrockConverseMessagesProcessor:
             assistant_content = _deduplicate_bedrock_content_blocks(
                 assistant_content, "toolUse"
             )
+            assistant_content = _sort_bedrock_assistant_content_blocks(
+                assistant_content
+            )
 
             if assistant_content:
                 contents.append(
@@ -5007,6 +5040,9 @@ def _bedrock_converse_messages_pt(  # noqa: PLR0915
         assistant_content = _deduplicate_bedrock_content_blocks(
             assistant_content, "toolUse"
         )
+        assistant_content = _sort_bedrock_assistant_content_blocks(
+            assistant_content
+        )
 
         if assistant_content:
             contents.append(

tests/litellm_core_utils/test_bedrock_converse_dedup_factory.py

@@ -9,6 +9,7 @@ from litellm.litellm_core_utils.prompt_templates.factory import (
     _bedrock_converse_messages_pt,
     _deduplicate_bedrock_content_blocks,
     _deduplicate_bedrock_tool_content,
+    _sort_bedrock_assistant_content_blocks,
     BedrockConverseMessagesProcessor,
 )
 
@@ -445,3 +446,133 @@ def test_bedrock_converse_filters_empty_list_content():
     assert len(text_blocks) == 2
     assert text_blocks[0]["text"] == "Hello"
     assert text_blocks[1]["text"] == "World"
+
+
+# ---------------------------------------------------------------------------
+# Content block ordering tests (text before toolUse)
+# ---------------------------------------------------------------------------
+
+
+def _make_tooluse_before_text_messages():
+    """Return messages where the assistant message has a tool_call followed by
+    a separate assistant message with text content.  When merged, the toolUse
+    block would end up before the text block without sorting."""
+    return [
+        {"role": "user", "content": "What's the weather?"},
+        {
+            "role": "assistant",
+            "content": None,
+            "tool_calls": [
+                {
+                    "id": "tooluse_abc123",
+                    "type": "function",
+                    "function": {
+                        "name": "get_weather",
+                        "arguments": '{"location": "Paris"}',
+                    },
+                }
+            ],
+        },
+        {
+            "role": "assistant",
+            "content": "Let me check the weather for you.",
+        },
+        {
+            "role": "tool",
+            "tool_call_id": "tooluse_abc123",
+            "content": '{"temp": 22}',
+        },
+    ]
+
+
+def test_sort_bedrock_assistant_content_blocks_text_before_tooluse():
+    """Direct unit test: text blocks should come before toolUse blocks."""
+    blocks = [
+        {"toolUse": {"toolUseId": "id_1", "name": "fn_a", "input": {}}},
+        {"text": "thinking..."},
+    ]
+
+    result = _sort_bedrock_assistant_content_blocks(blocks)
+
+    assert len(result) == 2
+    assert "text" in result[0]
+    assert "toolUse" in result[1]
+
+
+def test_sort_bedrock_assistant_content_blocks_reasoning_first():
+    """reasoningContent blocks should come before text and toolUse."""
+    blocks = [
+        {"toolUse": {"toolUseId": "id_1", "name": "fn_a", "input": {}}},
+        {"text": "thinking..."},
+        {"reasoningContent": {"reasoningText": {"text": "reasoning"}}},
+    ]
+
+    result = _sort_bedrock_assistant_content_blocks(blocks)
+
+    assert "reasoningContent" in result[0]
+    assert "text" in result[1]
+    assert "toolUse" in result[2]
+
+
+def test_sort_bedrock_assistant_content_blocks_preserves_order_when_correct():
+    """If blocks are already in the correct order, sorting should not change them."""
+    blocks = [
+        {"text": "hello"},
+        {"toolUse": {"toolUseId": "id_1", "name": "fn_a", "input": {}}},
+        {"toolUse": {"toolUseId": "id_2", "name": "fn_b", "input": {}}},
+    ]
+
+    result = _sort_bedrock_assistant_content_blocks(blocks)
+
+    assert result == blocks
+
+
+def test_bedrock_converse_sorts_text_before_tooluse_sync():
+    """Verify the sync path sorts text blocks before toolUse blocks in
+    assistant messages."""
+    messages = _make_tooluse_before_text_messages()
+    result = _bedrock_converse_messages_pt(messages, MODEL, PROVIDER)
+
+    assistant_msgs = [msg for msg in result if msg["role"] == "assistant"]
+    assert len(assistant_msgs) == 1
+
+    content = assistant_msgs[0]["content"]
+    text_indices = [i for i, b in enumerate(content) if "text" in b]
+    tool_indices = [i for i, b in enumerate(content) if "toolUse" in b]
+
+    # All text blocks must come before all toolUse blocks
+    assert max(text_indices) < min(tool_indices), (
+        f"text blocks at {text_indices} should all precede toolUse blocks at {tool_indices}"
+    )
+
+
+@pytest.mark.asyncio
+async def test_bedrock_converse_sorts_text_before_tooluse_async():
+    """Verify the async path sorts text blocks before toolUse blocks in
+    assistant messages."""
+    messages = _make_tooluse_before_text_messages()
+    result = await BedrockConverseMessagesProcessor._bedrock_converse_messages_pt_async(
+        messages, MODEL, PROVIDER
+    )
+
+    assistant_msgs = [msg for msg in result if msg["role"] == "assistant"]
+    assert len(assistant_msgs) == 1
+
+    content = assistant_msgs[0]["content"]
+    text_indices = [i for i, b in enumerate(content) if "text" in b]
+    tool_indices = [i for i, b in enumerate(content) if "toolUse" in b]
+
+    assert max(text_indices) < min(tool_indices), (
+        f"text blocks at {text_indices} should all precede toolUse blocks at {tool_indices}"
+    )
+
+
+@pytest.mark.asyncio
+async def test_bedrock_converse_content_ordering_sync_async_parity():
+    """Sync and async paths should produce identical content block ordering."""
+    messages = _make_tooluse_before_text_messages()
+    sync_result = _bedrock_converse_messages_pt(messages, MODEL, PROVIDER)
+    async_result = await BedrockConverseMessagesProcessor._bedrock_converse_messages_pt_async(
+        messages, MODEL, PROVIDER
+    )
+    assert sync_result == async_result