diff --git a/packages/data-schemas/src/methods/chatProject.spec.ts b/packages/data-schemas/src/methods/chatProject.spec.ts
index ca60fd0a7b..53f283a5a0 100644
--- a/packages/data-schemas/src/methods/chatProject.spec.ts
+++ b/packages/data-schemas/src/methods/chatProject.spec.ts
@@ -313,13 +313,17 @@ describe('ChatProject methods', () => {
     ]);
     await SharedLink.create({ conversationId: 'convo-1', user, shareId: uuidv4() });
 
-    await methods.assignConversationToProject(
+    const result = await methods.assignConversationToProject(
       user,
       'convo-1',
       project._id!.toString(),
       ephemeralConfig,
     );
 
+    expect(result?.conversation.isTemporary).toBe(true);
+    expect(result?.conversation.expiredAt).toBeInstanceOf(Date);
+    expect(result?.conversation.chatProjectId).toBe(project._id!.toString());
+
     const conversation = await Conversation.findOne({
       user,
       conversationId: 'convo-1',
diff --git a/packages/data-schemas/src/methods/chatProject.ts b/packages/data-schemas/src/methods/chatProject.ts
index cb7dd7fb35..45772512d7 100644
--- a/packages/data-schemas/src/methods/chatProject.ts
+++ b/packages/data-schemas/src/methods/chatProject.ts
@@ -486,6 +486,16 @@ export function createChatProjectMethods(mongoose: typeof import('mongoose')): C
     }
 
     const previousProjectId = conversation.chatProjectId ?? null;
+
+    /**
+     * Convert the touched conversation to the forced (ephemeral) window before capturing the
+     * updated document. The caller returns this object straight to the client, which writes it
+     * into the active conversation and the React Query cache, so it must already carry the
+     * isTemporary/expiredAt fields rather than a stale pre-conversion snapshot. A no-op outside
+     * forced retention.
+     */
+    await forceConversationRetention(user, conversationId, interfaceConfig);
+
     const update =
       normalizedProjectId == null
         ? { $unset: { chatProjectId: '' } }
@@ -500,8 +510,6 @@ export function createChatProjectMethods(mongoose: typeof import('mongoose')): C
       return null;
     }
 
-    await forceConversationRetention(user, conversationId, interfaceConfig);
-
     const projectIds = new Set(
       [previousProjectId, normalizedProjectId].filter((id): id is string => Boolean(id)),
     );