diff --git a/joint_teapot/app.py b/joint_teapot/app.py
index 139e709..338b8e5 100644
--- a/joint_teapot/app.py
+++ b/joint_teapot/app.py
@@ -294,6 +294,36 @@ def create_personal_channels_on_mm(
     tea.pot.create_channels_for_individuals(invite_teaching_team)
 
 
+@app.command(
+    "update-group-channels-on-mm",
+    help="update Mattermost channels for student groups based on team information on Gitea; only add missing members",
+)
+def update_group_channels_on_mm(
+    prefix: str = Option("", help="Only process repositories starting with this prefix"),
+    suffix: str = Option("", help="Only process channels ending with this suffix"),
+    update_teaching_team: bool = Option(True, "--update-teaching-team/--no-update-teaching-team", help="Whether to update teaching team"),
+    dry_run: bool = Option(False, "--dry-run/--no-dry-run", help="Dry run: show what would be added without making changes"),
+) -> None:
+    groups = {
+        group_name: members
+        for group_name, members in tea.pot.gitea.get_all_teams().items()
+        if group_name.startswith(prefix)
+    }
+    logger.info(f"{len(groups)} group channel(s) to update" + (f" with suffix {suffix}" if suffix else ""))
+    tea.pot.mattermost.update_channels_for_groups(groups, suffix, update_teaching_team, dry_run)
+
+
+@app.command(
+    "update-personal-channels-on-mm",
+    help="update personal Mattermost channels for every student; only add missing members",
+)
+def update_personal_channels_on_mm(
+    update_teaching_team: bool = Option(True, "--update-teaching-team/--no-update-teaching-team", help="Whether to update teaching team"),
+    dry_run: bool = Option(False, "--dry-run/--no-dry-run", help="Dry run: show what would be added without making changes"),
+) -> None:
+    tea.pot.mattermost.update_channels_for_individuals(tea.pot.canvas.students, update_teaching_team, dry_run)
+
+
 @app.command(
     "create-webhooks-for-mm",
     help="create a pair of webhooks on gitea and mm for all student groups on gitea, "