diff --git a/migrations/mysql/2026-11-02-120000_reset_user_key_id/down.sql b/migrations/mysql/2026-11-02-120000_reset_user_key_id/down.sql
new file mode 100644
index 00000000..e69de29b
diff --git a/migrations/mysql/2026-11-02-120000_reset_user_key_id/up.sql b/migrations/mysql/2026-11-02-120000_reset_user_key_id/up.sql
new file mode 100644
index 00000000..eeffa854
--- /dev/null
+++ b/migrations/mysql/2026-11-02-120000_reset_user_key_id/up.sql
@@ -0,0 +1,4 @@
+-- Key rotations before this kept the id of the old user key, so every new
+-- cipher was refused from then on. Stale ids can't be told apart, so clear
+-- all of them; clients record their current key's id again when it's empty.
+UPDATE users SET key_id = NULL;
diff --git a/migrations/postgresql/2026-11-02-120000_reset_user_key_id/down.sql b/migrations/postgresql/2026-11-02-120000_reset_user_key_id/down.sql
new file mode 100644
index 00000000..e69de29b
diff --git a/migrations/postgresql/2026-11-02-120000_reset_user_key_id/up.sql b/migrations/postgresql/2026-11-02-120000_reset_user_key_id/up.sql
new file mode 100644
index 00000000..eeffa854
--- /dev/null
+++ b/migrations/postgresql/2026-11-02-120000_reset_user_key_id/up.sql
@@ -0,0 +1,4 @@
+-- Key rotations before this kept the id of the old user key, so every new
+-- cipher was refused from then on. Stale ids can't be told apart, so clear
+-- all of them; clients record their current key's id again when it's empty.
+UPDATE users SET key_id = NULL;
diff --git a/migrations/sqlite/2026-11-02-120000_reset_user_key_id/down.sql b/migrations/sqlite/2026-11-02-120000_reset_user_key_id/down.sql
new file mode 100644
index 00000000..e69de29b
diff --git a/migrations/sqlite/2026-11-02-120000_reset_user_key_id/up.sql b/migrations/sqlite/2026-11-02-120000_reset_user_key_id/up.sql
new file mode 100644
index 00000000..eeffa854
--- /dev/null
+++ b/migrations/sqlite/2026-11-02-120000_reset_user_key_id/up.sql
@@ -0,0 +1,4 @@
+-- Key rotations before this kept the id of the old user key, so every new
+-- cipher was refused from then on. Stale ids can't be told apart, so clear
+-- all of them; clients record their current key's id again when it's empty.
+UPDATE users SET key_id = NULL;