diff --git a/src/lib/responses/ResponseInputItems.ts b/src/lib/responses/ResponseInputItems.ts
new file mode 100644
index 000000000..e26e08121
--- /dev/null
+++ b/src/lib/responses/ResponseInputItems.ts
@@ -0,0 +1,70 @@
+import type {
+  ResponseFunctionShellCallOutputContent,
+  ResponseInputItem,
+  ResponseOutputItem,
+} from '../../resources/responses/responses';
+
+export type ResponseInputItemLike = ResponseInputItem | ResponseOutputItem;
+
+type ResponseShellCallOutputInputItem = Extract<ResponseInputItem, { type: 'shell_call_output' }>;
+
+/**
+ * Normalizes a mixed array of stored response history items into clean
+ * `ResponseInputItem`s that can be sent back to `responses.create()`.
+ */
+export function toResponseInputItems(items: Iterable<ResponseInputItemLike>): ResponseInputItem[] {
+  return Array.from(items, toResponseInputItem);
+}
+
+/**
+ * Normalizes a stored response history item into a clean `ResponseInputItem`.
+ */
+export function toResponseInputItem(item: ResponseInputItemLike): ResponseInputItem {
+  switch (item.type) {
+    case 'apply_patch_call': {
+      return stripCreatedBy(item);
+    }
+
+    case 'apply_patch_call_output': {
+      return stripCreatedBy(item);
+    }
+
+    case 'compaction': {
+      return stripCreatedBy(item);
+    }
+
+    case 'shell_call': {
+      return stripCreatedBy(item);
+    }
+
+    case 'shell_call_output': {
+      const output: ResponseShellCallOutputInputItem['output'] = item.output.map(
+        (chunk) => stripCreatedBy(chunk) as ResponseFunctionShellCallOutputContent,
+      );
+      return {
+        ...(stripCreatedBy(item) as ResponseShellCallOutputInputItem),
+        output,
+      };
+    }
+
+    case 'tool_search_call': {
+      return stripCreatedBy(item);
+    }
+
+    case 'tool_search_output': {
+      return stripCreatedBy(item);
+    }
+
+    default:
+      return item;
+  }
+}
+
+function stripCreatedBy<T extends object>(item: T): T {
+  if (!('created_by' in item)) {
+    return item;
+  }
+
+  const { created_by: _createdBy, ...rest } = item as T & { created_by?: string };
+  return rest as T;
+}
diff --git a/tests/lib/ResponseInputItems.test.ts b/tests/lib/ResponseInputItems.test.ts
new file mode 100644
index 000000000..29178a040
--- /dev/null
+++ b/tests/lib/ResponseInputItems.test.ts
@@ -0,0 +1,143 @@
+import { toResponseInputItems } from 'openai/lib/responses/ResponseInputItems';
+import type { ResponseInputItem, ResponseOutputItem } from 'openai/resources/responses';
+
+describe('toResponseInputItems', () => {
+  test('normalizes mixed response history items', () => {
+    const history: Array<ResponseInputItem | ResponseOutputItem> = [
+      {
+        type: 'function_call_output',
+        call_id: 'function_call_123',
+        output: 'done',
+      },
+      {
+        type: 'tool_search_call',
+        id: 'tool_search_item_123',
+        call_id: 'tool_search_call_123',
+        arguments: { query: 'schema' },
+        execution: 'server',
+        status: 'completed',
+        created_by: 'assistant',
+      },
+      {
+        type: 'compaction',
+        id: 'compaction_123',
+        encrypted_content: 'encrypted',
+        created_by: 'assistant',
+      },
+      {
+        type: 'shell_call',
+        id: 'shell_call_123',
+        call_id: 'shell_call_123',
+        action: {
+          commands: ['pwd'],
+          max_output_length: 512,
+          timeout_ms: 1000,
+        },
+        environment: null,
+        status: 'completed',
+        created_by: 'assistant',
+      },
+      {
+        type: 'shell_call_output',
+        id: 'shell_call_output_123',
+        call_id: 'shell_call_123',
+        max_output_length: 512,
+        output: [
+          {
+            stdout: '/workspace\n',
+            stderr: '',
+            outcome: { type: 'exit', exit_code: 0 },
+            created_by: 'assistant',
+          },
+        ],
+        status: 'completed',
+        created_by: 'assistant',
+      },
+      {
+        type: 'apply_patch_call',
+        id: 'apply_patch_call_123',
+        call_id: 'apply_patch_call_123',
+        operation: {
+          type: 'create_file',
+          path: 'notes.txt',
+          diff: 'hello',
+        },
+        status: 'completed',
+        created_by: 'assistant',
+      },
+      {
+        type: 'apply_patch_call_output',
+        id: 'apply_patch_call_output_123',
+        call_id: 'apply_patch_call_123',
+        output: 'created notes.txt',
+        status: 'completed',
+        created_by: 'assistant',
+      },
+    ];
+
+    expect(toResponseInputItems(history)).toEqual([
+      {
+        type: 'function_call_output',
+        call_id: 'function_call_123',
+        output: 'done',
+      },
+      {
+        type: 'tool_search_call',
+        id: 'tool_search_item_123',
+        call_id: 'tool_search_call_123',
+        arguments: { query: 'schema' },
+        execution: 'server',
+        status: 'completed',
+      },
+      {
+        type: 'compaction',
+        id: 'compaction_123',
+        encrypted_content: 'encrypted',
+      },
+      {
+        type: 'shell_call',
+        id: 'shell_call_123',
+        call_id: 'shell_call_123',
+        action: {
+          commands: ['pwd'],
+          max_output_length: 512,
+          timeout_ms: 1000,
+        },
+        environment: null,
+        status: 'completed',
+      },
+      {
+        type: 'shell_call_output',
+        id: 'shell_call_output_123',
+        call_id: 'shell_call_123',
+        max_output_length: 512,
+        output: [
+          {
+            stdout: '/workspace\n',
+            stderr: '',
+            outcome: { type: 'exit', exit_code: 0 },
+          },
+        ],
+        status: 'completed',
+      },
+      {
+        type: 'apply_patch_call',
+        id: 'apply_patch_call_123',
+        call_id: 'apply_patch_call_123',
+        operation: {
+          type: 'create_file',
+          path: 'notes.txt',
+          diff: 'hello',
+        },
+        status: 'completed',
+      },
+      {
+        type: 'apply_patch_call_output',
+        id: 'apply_patch_call_output_123',
+        call_id: 'apply_patch_call_123',
+        output: 'created notes.txt',
+        status: 'completed',
+      },
+    ]);
+  });
+});
diff --git a/tests/responsesItems.test.ts b/tests/responsesItems.test.ts
index 84853fcf3..97bb50c53 100644
--- a/tests/responsesItems.test.ts
+++ b/tests/responsesItems.test.ts
@@ -1,4 +1,7 @@
 import OpenAI from 'openai/index';
+import { toResponseInputItems } from 'openai/lib/responses/ResponseInputItems';
+import type { ResponseInputItem, ResponseOutputItem } from 'openai/resources/responses';
+
 const openai = new OpenAI({ apiKey: 'example-api-key' });
 
 describe('responses item types', () => {
@@ -12,10 +15,25 @@ const unused = async () => {
     model: 'gpt-5.1',
     input: 'You are a helpful assistant.',
   });
+
+  const history: Array<ResponseInputItem | ResponseOutputItem> = [
+    {
+      type: 'function_call_output',
+      call_id: 'call_123',
+      output: 'done',
+    },
+    ...response.output,
+  ];
+
   await openai.responses.create({
     model: 'gpt-5.1',
     // check type compatibility
     input: response.output,
   });
+  await openai.responses.create({
+    model: 'gpt-5.1',
+    // check mixed history normalization
+    input: toResponseInputItems(history),
+  });
   expect(true).toBe(true);
 };