diff --git a/apps/api/src/api/user_config.py b/apps/api/src/api/user_config.py
index af2da07..917bfa9 100644
--- a/apps/api/src/api/user_config.py
+++ b/apps/api/src/api/user_config.py
@@ -112,7 +112,8 @@ async def update_user_config(
     # Merge updates
     update_data = data.model_dump(exclude_unset=True)
     logger.info("Updating user config for user %s: %s", user_id, update_data)
-    config.config.update(update_data)
+    # SQLAlchemy JSON doesn't track dict mutations, so we replace the whole dict
+    config.config = {**config.config, **update_data}
 
     await session.commit()
     await session.refresh(config)
diff --git a/apps/web/src/api/settings.ts b/apps/web/src/api/settings.ts
index 4114854..af99e89 100644
--- a/apps/web/src/api/settings.ts
+++ b/apps/web/src/api/settings.ts
@@ -9,11 +9,11 @@ export interface UserConfig {
 }
 
 export interface UserConfigUpdate {
-  default_editor?: string;
-  theme?: string;
-  git_user_name?: string;
-  git_user_email?: string;
-  last_session_id?: string;
+  default_editor?: string | null;
+  theme?: string | null;
+  git_user_name?: string | null;
+  git_user_email?: string | null;
+  last_session_id?: string | null;
 }
 
 export const getUserConfig = async (): Promise<UserConfig> => {
diff --git a/apps/web/src/pages/settings.tsx b/apps/web/src/pages/settings.tsx
index d8478f7..3d28e4b 100644
--- a/apps/web/src/pages/settings.tsx
+++ b/apps/web/src/pages/settings.tsx
@@ -46,9 +46,9 @@ export const SettingsPage = () => {
     try {
       const update: UserConfigUpdate = {
         theme: config.theme,
-        default_editor: config.default_editor ?? undefined,
-        git_user_name: config.git_user_name ?? undefined,
-        git_user_email: config.git_user_email ?? undefined,
+        default_editor: config.default_editor,
+        git_user_name: config.git_user_name,
+        git_user_email: config.git_user_email,
       };
       console.log("Sending update:", update);
       const updated = await updateUserConfig(update);