fix: bedrock chat converter reasoning messages closes #3688

core/providers/bedrock/bedrock_test.go

@@ -3923,6 +3923,71 @@ func TestMultiTurnReasoningContentPassthrough(t *testing.T) {
 		assert.True(t, foundReasoning, "Expected reasoning content block in assistant message")
 	})
 
+	t.Run("AssistantMessage_WithReasoningAndToolCalls_ReasoningComesFirst", func(t *testing.T) {
+		reasoningText := "I need to call a tool to answer this."
+		signature := "sig_abc123"
+		assistantContent := "Let me check that for you."
+		toolCallID := "tooluse_abc123"
+
+		bifrostReq := &schemas.BifrostChatRequest{
+			Provider: schemas.Bedrock,
+			Model:    "anthropic.claude-sonnet-4-6",
+			Input: []schemas.ChatMessage{
+				{
+					Role:    schemas.ChatMessageRoleUser,
+					Content: &schemas.ChatMessageContent{ContentStr: schemas.Ptr("What time is it?")},
+				},
+				{
+					Role:    schemas.ChatMessageRoleAssistant,
+					Content: &schemas.ChatMessageContent{ContentStr: &assistantContent},
+					ChatAssistantMessage: &schemas.ChatAssistantMessage{
+						ReasoningDetails: []schemas.ChatReasoningDetails{
+							{
+								Index:     0,
+								Type:      schemas.BifrostReasoningDetailsTypeText,
+								Text:      &reasoningText,
+								Signature: &signature,
+							},
+						},
+						ToolCalls: []schemas.ChatAssistantMessageToolCall{
+							{
+								ID:   &toolCallID,
+								Type: schemas.Ptr("function"),
+								Function: schemas.ChatAssistantMessageToolCallFunction{
+									Name:      schemas.Ptr("get_time"),
+									Arguments: "{}",
+								},
+							},
+						},
+					},
+				},
+			},
+		}
+
+		ctx := schemas.NewBifrostContext(context.Background(), schemas.NoDeadline)
+		result, err := bedrock.ToBedrockChatCompletionRequest(ctx, bifrostReq)
+		require.NoError(t, err)
+		require.NotNil(t, result)
+
+		assistantMsg := result.Messages[1]
+		// reasoning + text + tool_use = at least 3 blocks
+		require.GreaterOrEqual(t, len(assistantMsg.Content), 3)
+
+		// Reasoning MUST be the first block
+		assert.NotNil(t, assistantMsg.Content[0].ReasoningContent,
+			"reasoning block must be first content block; got %+v", assistantMsg.Content[0])
+
+		// tool_use must appear after reasoning
+		var foundToolUse bool
+		for _, block := range assistantMsg.Content[1:] {
+			if block.ToolUse != nil {
+				foundToolUse = true
+				break
+			}
+		}
+		assert.True(t, foundToolUse, "tool_use block must appear after reasoning block")
+	})
+
 	t.Run("AssistantMessage_WithoutReasoningDetails_NoReasoningContent", func(t *testing.T) {
 		assistantContent := "Simple response"
 

core/providers/bedrock/utils.go

@@ -739,25 +739,9 @@ func convertMessage(ctx context.Context, msg schemas.ChatMessage) (BedrockMessag
 		Role: BedrockMessageRole(msg.Role),
 	}
 
-	// Convert content
 	var contentBlocks []BedrockContentBlock
-	if msg.Content != nil {
-		var err error
-		contentBlocks, err = convertContent(ctx, *msg.Content)
-		if err != nil {
-			return BedrockMessage{}, fmt.Errorf("failed to convert content: %w", err)
-		}
-	}
-
-	// Add tool calls if present (for assistant messages)
-	if msg.ChatAssistantMessage != nil && msg.ChatAssistantMessage.ToolCalls != nil {
-		for _, toolCall := range msg.ChatAssistantMessage.ToolCalls {
-			toolUseBlock := convertToolCallToContentBlock(toolCall)
-			contentBlocks = append(contentBlocks, toolUseBlock)
-		}
-	}
 
-	// Add reasoning content if present (for multi-turn conversations with thinking)
+	// Add reasoning content first
 	if msg.ChatAssistantMessage != nil && len(msg.ChatAssistantMessage.ReasoningDetails) > 0 {
 		for _, detail := range msg.ChatAssistantMessage.ReasoningDetails {
 			if detail.Type == schemas.BifrostReasoningDetailsTypeText {
@@ -773,6 +757,22 @@ func convertMessage(ctx context.Context, msg schemas.ChatMessage) (BedrockMessag
 		}
 	}
 
+	// Convert text/image content
+	if msg.Content != nil {
+		textBlocks, err := convertContent(ctx, *msg.Content)
+		if err != nil {
+			return BedrockMessage{}, fmt.Errorf("failed to convert content: %w", err)
+		}
+		contentBlocks = append(contentBlocks, textBlocks...)
+	}
+
+	// Add tool calls last (for assistant messages)
+	if msg.ChatAssistantMessage != nil && msg.ChatAssistantMessage.ToolCalls != nil {
+		for _, toolCall := range msg.ChatAssistantMessage.ToolCalls {
+			contentBlocks = append(contentBlocks, convertToolCallToContentBlock(toolCall))
+		}
+	}
+
 	bedrockMsg.Content = contentBlocks
 	return bedrockMsg, nil
 }