diff --git a/.changeset/preserve-model-message-created-at.md b/.changeset/preserve-model-message-created-at.md
new file mode 100644
index 000000000..ddb62be11
--- /dev/null
+++ b/.changeset/preserve-model-message-created-at.md
@@ -0,0 +1,5 @@
+---
+'@tanstack/ai': patch
+---
+
+Preserve `UIMessage.createdAt` when converting messages to and from `ModelMessage` so persisted transcripts retain their original timestamps.
diff --git a/packages/ai/src/activities/chat/messages.ts b/packages/ai/src/activities/chat/messages.ts
index 87dbb17f1..153cf5711 100644
--- a/packages/ai/src/activities/chat/messages.ts
+++ b/packages/ai/src/activities/chat/messages.ts
@@ -186,6 +186,9 @@ function buildUserOrToolMessage(uiMessage: UIMessage): ModelMessage {
   return {
     role: uiMessage.role as 'user' | 'assistant' | 'tool',
     content: collapseContentParts(contentParts),
+    ...(uiMessage.createdAt !== undefined && {
+      createdAt: uiMessage.createdAt,
+    }),
   }
 }
 
@@ -248,6 +251,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
         content,
         ...(hasToolCalls && { toolCalls: current.toolCalls }),
         ...(pendingThinking.length > 0 && { thinking: pendingThinking }),
+        ...(uiMessage.createdAt !== undefined && {
+          createdAt: uiMessage.createdAt,
+        }),
       })
       pendingThinking = []
     }
@@ -291,6 +297,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
             role: 'tool',
             content: part.content,
             toolCallId: part.toolCallId,
+            ...(uiMessage.createdAt !== undefined && {
+              createdAt: uiMessage.createdAt,
+            }),
           })
           emittedToolResultIds.add(part.toolCallId)
         }
@@ -350,6 +359,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
         role: 'tool',
         content: normalizeToolResult(part.output),
         toolCallId: part.id,
+        ...(uiMessage.createdAt !== undefined && {
+          createdAt: uiMessage.createdAt,
+        }),
       })
       emittedToolResultIds.add(part.id)
     }
@@ -372,6 +384,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
             : 'User denied this action',
         }),
         toolCallId: part.id,
+        ...(uiMessage.createdAt !== undefined && {
+          createdAt: uiMessage.createdAt,
+        }),
       })
       emittedToolResultIds.add(part.id)
     }
@@ -382,6 +397,9 @@ function buildAssistantMessages(uiMessage: UIMessage): Array<ModelMessage> {
     messageList.push({
       role: 'assistant',
       content: null,
+      ...(uiMessage.createdAt !== undefined && {
+        createdAt: uiMessage.createdAt,
+      }),
     })
   }
 
@@ -469,6 +487,9 @@ export function modelMessageToUIMessage(
     id: id || generateMessageId(),
     role: modelMessage.role === 'tool' ? 'assistant' : modelMessage.role,
     parts,
+    ...(modelMessage.createdAt !== undefined && {
+      createdAt: modelMessage.createdAt,
+    }),
   }
 }
 
@@ -659,7 +680,7 @@ export function normalizeToUIMessage(
     // ModelMessage - convert to UIMessage
     return {
       ...modelMessageToUIMessage(message, generateId()),
-      createdAt: new Date(),
+      createdAt: message.createdAt ?? new Date(),
     }
   }
 }
diff --git a/packages/ai/src/types.ts b/packages/ai/src/types.ts
index 6893dd710..0996ba05a 100644
--- a/packages/ai/src/types.ts
+++ b/packages/ai/src/types.ts
@@ -376,6 +376,11 @@ export interface ModelMessage<
    * resume the SAME message bubble in place (see `@tanstack/ai-persistence`).
    */
   id?: string
+  /**
+   * Optional message creation timestamp. When present, message converters
+   * preserve it across persist → hydrate round-trips.
+   */
+  createdAt?: Date
 }
 
 /**
diff --git a/packages/ai/tests/message-converters.test.ts b/packages/ai/tests/message-converters.test.ts
index f037a396d..5f99916c2 100644
--- a/packages/ai/tests/message-converters.test.ts
+++ b/packages/ai/tests/message-converters.test.ts
@@ -1202,14 +1202,29 @@ describe('Message Converters', () => {
       expect(result.parts).toEqual([{ type: 'text', content: 'Hello' }])
       expect(result.createdAt).toBeTruthy()
     })
+
+    it('should preserve createdAt when converting a ModelMessage', () => {
+      const createdAt = new Date('2025-01-01')
+      const message: ModelMessage = {
+        role: 'user',
+        content: 'Hello',
+        createdAt,
+      }
+
+      const result = normalizeToUIMessage(message, () => 'generated-id')
+
+      expect(result.createdAt).toBe(createdAt)
+    })
   })
 
   describe('Round-trip symmetry: UI -> Model -> UI', () => {
     it('should round-trip simple text user message', () => {
+      const createdAt = new Date('2025-01-01')
       const original: UIMessage = {
         id: 'msg-1',
         role: 'user',
         parts: [{ type: 'text', content: 'Hello world' }],
+        createdAt,
       }
 
       const modelMessages = uiMessageToModelMessages(original)
@@ -1218,6 +1233,59 @@ describe('Message Converters', () => {
       expect(uiMessages.length).toBe(1)
       expect(uiMessages[0]?.role).toBe(original.role)
       expect(uiMessages[0]?.parts).toEqual(original.parts)
+      expect(uiMessages[0]?.createdAt).toBe(createdAt)
+    })
+
+    it('should preserve createdAt for assistant segments and tool results', () => {
+      const createdAt = new Date('2025-01-01')
+      const original: UIMessage = {
+        id: 'msg-1',
+        role: 'assistant',
+        parts: [
+          { type: 'text', content: 'Checking inventory.' },
+          {
+            type: 'tool-call',
+            id: 'tc-1',
+            name: 'getInventory',
+            arguments: '{}',
+            state: 'input-complete',
+          },
+          {
+            type: 'tool-result',
+            toolCallId: 'tc-1',
+            content: '{"ok":true}',
+            state: 'complete',
+          },
+        ],
+        createdAt,
+      }
+
+      const modelMessages = uiMessageToModelMessages(original)
+
+      expect(modelMessages).toEqual([
+        {
+          role: 'assistant',
+          content: 'Checking inventory.',
+          toolCalls: [
+            {
+              id: 'tc-1',
+              type: 'function',
+              function: { name: 'getInventory', arguments: '{}' },
+            },
+          ],
+          createdAt,
+        },
+        {
+          role: 'tool',
+          content: '{"ok":true}',
+          toolCallId: 'tc-1',
+          createdAt,
+        },
+      ])
+
+      const uiMessages = modelMessagesToUIMessages(modelMessages)
+      expect(uiMessages).toHaveLength(1)
+      expect(uiMessages[0]?.createdAt).toBe(createdAt)
     })
 
     it('should round-trip assistant with tool-call + tool-result', () => {