fix (provider/anthropic): revert cd458a8 (#8536)

## Background


cd458a8
did not fix the underlying issue and caused
#8516

## Summary

Revert #cd458a8c1667df86e6987a1f2e06159823453864

## Related Issues

#8516 #8474

Author: lgrammel

.changeset/early-bugs-raise.md

@@ -0,0 +1,5 @@
+---
+'@ai-sdk/anthropic': patch
+---
+
+fix (provider/anthropic): revert cd458a8c1667df86e6987a1f2e06159823453864

packages/anthropic/src/convert-to-anthropic-messages-prompt.test.ts

@@ -372,7 +372,7 @@ describe('tool messages', () => {
     });
   });
 
-  it('should combine tool and user messages with tool_result first', async () => {
+  it('should combine user and tool messages', async () => {
     const result = await convertToAnthropicMessagesPrompt({
       prompt: [
         {
@@ -409,13 +409,8 @@ describe('tool messages', () => {
                 tool_use_id: 'tool-call-1',
                 is_error: undefined,
                 content: JSON.stringify({ test: 'This is a tool message' }),
-                cache_control: undefined,
-              },
-              {
-                type: 'text',
-                text: 'This is a user message',
-                cache_control: undefined,
               },
+              { type: 'text', text: 'This is a user message' },
             ],
           },
         ],
@@ -425,84 +420,6 @@ describe('tool messages', () => {
     });
   });
 
-  it('should place tool_result before user text in combined messages', async () => {
-    // Ensures tool_result parts appear first in combined user messages
-    const result = await convertToAnthropicMessagesPrompt({
-      prompt: [
-        {
-          role: 'user',
-          content: [{ type: 'text', text: 'generate 10 items' }],
-        },
-        {
-          role: 'assistant',
-          content: [
-            {
-              type: 'tool-call',
-              toolCallId: 'tool-example-123',
-              toolName: 'json',
-              input: {
-                message: 'generate 10 items',
-              },
-            },
-            {
-              type: 'text',
-              text: 'I generated code for 10 items.',
-            },
-          ],
-        },
-        {
-          role: 'tool',
-          content: [
-            {
-              type: 'tool-result',
-              toolCallId: 'tool-example-123',
-              toolName: 'json',
-              output: {
-                type: 'json',
-                value: {
-                  code: 'export const code = () => [...]',
-                  packageJson: '{}',
-                },
-              },
-            },
-          ],
-        },
-        {
-          role: 'user',
-          content: [{ type: 'text', text: 'generate 100 items' }],
-        },
-      ],
-      sendReasoning: true,
-      warnings: [],
-    });
-
-    // The key fix: tool_result and user content are combined in a single message
-    // but tool_result appears FIRST to satisfy Claude's validation requirements
-    expect(result.prompt.messages).toHaveLength(3);
-    expect(result.prompt.messages[0].role).toBe('user');
-    expect(result.prompt.messages[1].role).toBe('assistant');
-    expect(result.prompt.messages[2].role).toBe('user'); // combined tool_result + user message
-
-    // Verify tool_result comes before user text in the combined message
-    expect(result.prompt.messages[2].content).toEqual([
-      {
-        type: 'tool_result',
-        tool_use_id: 'tool-example-123',
-        is_error: undefined,
-        content: JSON.stringify({
-          code: 'export const code = () => [...]',
-          packageJson: '{}',
-        }),
-        cache_control: undefined,
-      },
-      {
-        type: 'text',
-        text: 'generate 100 items',
-        cache_control: undefined,
-      },
-    ]);
-  });
-
   it('should handle tool result with content parts', async () => {
     const result = await convertToAnthropicMessagesPrompt({
       prompt: [
@@ -573,170 +490,6 @@ describe('tool messages', () => {
       }
     `);
   });
-
-  it('should place tool_result before user text in combined message', async () => {
-    // Combines tool_result and user text in a single message (preserving role alternation)
-    // but tool_result parts appear first, satisfying Claude's validation requirements
-
-    const result = await convertToAnthropicMessagesPrompt({
-      prompt: [
-        {
-          role: 'tool',
-          content: [
-            {
-              type: 'tool-result',
-              toolName: 'analyze-tool',
-              toolCallId: 'tool-call-123',
-              output: {
-                type: 'json',
-                value: { analysis: 'Tool execution completed' },
-              },
-            },
-          ],
-        },
-        {
-          role: 'user',
-          content: [
-            { type: 'text', text: 'Thanks! Now please provide more details.' },
-          ],
-        },
-      ],
-      sendReasoning: true,
-      warnings: [],
-    });
-
-    // Fixed behavior: still combines in single message, but tool_result comes first
-    // This satisfies Claude's "tool_result immediately after tool_use" requirement
-    expect(result).toEqual({
-      prompt: {
-        messages: [
-          {
-            role: 'user',
-            content: [
-              {
-                type: 'tool_result',
-                tool_use_id: 'tool-call-123',
-                is_error: undefined,
-                content: JSON.stringify({
-                  analysis: 'Tool execution completed',
-                }),
-              },
-              {
-                type: 'text',
-                text: 'Thanks! Now please provide more details.',
-              },
-            ],
-          },
-        ],
-        system: undefined,
-      },
-      betas: new Set(),
-    });
-  });
-
-  it('should place multiple tool_result parts before user text in correct order', async () => {
-    // Test multiple tool_use scenario: tool_result parts should appear first
-    // and maintain the same order as their corresponding tool_use ids
-    const result = await convertToAnthropicMessagesPrompt({
-      prompt: [
-        {
-          role: 'tool',
-          content: [
-            {
-              type: 'tool-result',
-              toolName: 'search-tool',
-              toolCallId: 'search-123',
-              output: { type: 'text', value: 'Search result' },
-            },
-            {
-              type: 'tool-result',
-              toolName: 'analyze-tool',
-              toolCallId: 'analyze-456',
-              output: { type: 'json', value: { status: 'complete' } },
-            },
-          ],
-        },
-        {
-          role: 'user',
-          content: [
-            {
-              type: 'text',
-              text: 'Great! What do you think about these results?',
-            },
-          ],
-        },
-      ],
-      sendReasoning: false,
-      warnings: [],
-    });
-
-    expect(result.prompt.messages).toHaveLength(1);
-    expect(result.prompt.messages[0]).toEqual({
-      role: 'user',
-      content: [
-        {
-          type: 'tool_result',
-          tool_use_id: 'search-123',
-          content: 'Search result',
-          is_error: undefined,
-        },
-        {
-          type: 'tool_result',
-          tool_use_id: 'analyze-456',
-          content: JSON.stringify({ status: 'complete' }),
-          is_error: undefined,
-        },
-        { type: 'text', text: 'Great! What do you think about these results?' },
-      ],
-    });
-  });
-
-  it('should place error tool_result parts before user text', async () => {
-    // Test error tool results: should also appear first even when is_error: true
-    const result = await convertToAnthropicMessagesPrompt({
-      prompt: [
-        {
-          role: 'tool',
-          content: [
-            {
-              type: 'tool-result',
-              toolName: 'failing-tool',
-              toolCallId: 'fail-789',
-              output: { type: 'error-text', value: 'Tool execution failed' },
-            },
-          ],
-        },
-        {
-          role: 'user',
-          content: [
-            {
-              type: 'text',
-              text: 'The tool failed. Can you try a different approach?',
-            },
-          ],
-        },
-      ],
-      sendReasoning: false,
-      warnings: [],
-    });
-
-    expect(result.prompt.messages).toHaveLength(1);
-    expect(result.prompt.messages[0]).toEqual({
-      role: 'user',
-      content: [
-        {
-          type: 'tool_result',
-          tool_use_id: 'fail-789',
-          content: 'Tool execution failed',
-          is_error: true,
-        },
-        {
-          type: 'text',
-          text: 'The tool failed. Can you try a different approach?',
-        },
-      ],
-    });
-  });
 });
 
 describe('assistant messages', () => {

packages/anthropic/src/convert-to-anthropic-messages-prompt.ts

@@ -311,21 +311,7 @@ export async function convertToAnthropicMessagesPrompt({
           }
         }
 
-        // Reorder content parts to ensure tool_result blocks appear first
-        // This satisfies Claude's "tool_result immediately after tool_use" validation
-        // while preserving the intentional message combining from #2067 (role alternation fix #2047)
-        const toolResultParts = anthropicContent.filter(
-          part => part.type === 'tool_result',
-        );
-        const otherParts = anthropicContent.filter(
-          part => part.type !== 'tool_result',
-        );
-        const reorderedContent =
-          toolResultParts.length > 0
-            ? [...toolResultParts, ...otherParts]
-            : anthropicContent;
-
-        messages.push({ role: 'user', content: reorderedContent });
+        messages.push({ role: 'user', content: anthropicContent });
 
         break;
       }
@@ -577,6 +563,7 @@ function groupIntoBlocks(
           currentBlock = { type: 'system', messages: [] };
           blocks.push(currentBlock);
         }
+
         currentBlock.messages.push(message);
         break;
       }
@@ -585,6 +572,7 @@ function groupIntoBlocks(
           currentBlock = { type: 'assistant', messages: [] };
           blocks.push(currentBlock);
         }
+
         currentBlock.messages.push(message);
         break;
       }
@@ -593,6 +581,7 @@ function groupIntoBlocks(
           currentBlock = { type: 'user', messages: [] };
           blocks.push(currentBlock);
         }
+
         currentBlock.messages.push(message);
         break;
       }
@@ -601,6 +590,7 @@ function groupIntoBlocks(
           currentBlock = { type: 'user', messages: [] };
           blocks.push(currentBlock);
         }
+
         currentBlock.messages.push(message);
         break;
       }