diff --git a/packages/api/src/import/chatgpt/convert.spec.ts b/packages/api/src/import/chatgpt/convert.spec.ts
index 8823f803bd..4ef4ef8823 100644
--- a/packages/api/src/import/chatgpt/convert.spec.ts
+++ b/packages/api/src/import/chatgpt/convert.spec.ts
@@ -25,7 +25,7 @@ const OPTIONS = {
 };
 
 describe('convertConversation', () => {
-  it('carries archive, pin, model, and external id onto the conversation', () => {
+  it('carries archive, pin, and external id onto the conversation, on the configured model', () => {
     const result = convertConversation(
       conversation({
         root: { id: 'root', message: null, parent: null, children: ['a'] },
@@ -46,7 +46,10 @@ describe('convertConversation', () => {
 
     expect(result.isArchived).toBe(true);
     expect(result.pinned).toBe(true);
-    expect(result.model).toBe('gpt-5-thinking');
+    /** Not `default_model_slug` ('gpt-5-thinking'): the conversation's model is
+     * what its next prompt is sent with, and a historical ChatGPT slug is not a
+     * model any endpoint serves. */
+    expect(result.model).toBe('gpt-4o');
     expect(result.externalId).toBe('ext-1');
     expect(result.title).toBe('Trip planning');
   });
diff --git a/packages/api/src/import/chatgpt/convert.ts b/packages/api/src/import/chatgpt/convert.ts
index 138209d237..24631980f9 100644
--- a/packages/api/src/import/chatgpt/convert.ts
+++ b/packages/api/src/import/chatgpt/convert.ts
@@ -210,8 +210,6 @@ export function convertConversation(
 
   orderTree(messages);
 
-  const { model } = resolveModel(conv.default_model_slug ?? undefined, options.defaultModel);
-
   return {
     conversationId: uuidv4(),
     externalId: conv.conversation_id,
@@ -219,7 +217,15 @@ export function convertConversation(
     createdAt: new Date(fallbackTime),
     isArchived: conv.is_archived === true,
     pinned: conv.is_starred === true || conv.pinned_time != null,
-    model,
+    /** The conversation's model is what its *next* prompt is sent with, so it
+     * has to be a model this deployment actually serves. `default_model_slug`
+     * is a historical ChatGPT identifier — `auto`, `research`, `gpt-5-t` — that
+     * no endpoint accepts, and setting it here would leave every imported
+     * conversation unusable until the user picked a model by hand. The
+     * per-message `model` keeps the historical slug for display, which is
+     * where it belongs; the Claude and Grok converters resolve this field the
+     * same way. */
+    model: options.defaultModel,
     messages,
   };
 }