diff --git a/src/databases/officer_db/src/dashboards/queries.ts b/src/databases/officer_db/src/dashboards/queries.ts
index d2533314..e5ed65b4 100644
--- a/src/databases/officer_db/src/dashboards/queries.ts
+++ b/src/databases/officer_db/src/dashboards/queries.ts
@@ -86,22 +86,47 @@ function buildDashboardSet(data: UpsertDashboardData, now: Date): Record<string,
   return set;
 }
 
+/**
+ * Create or update a dashboard, in ONE statement.
+ *
+ * This was update-then-insert, which is a read-then-write race, and creating a dashboard walks straight
+ * into it: the client sends `workspaces` (the list) and `ws-layout-<id>` (the layout) as two separate
+ * PATCHes. Both call this, both found no row, both INSERTed, and the loser hit the primary key. Observed
+ * 2026-08-15 — the surviving row and the failing insert were stamped ONE MILLISECOND apart, and the user
+ * saw "Internal Server Error" for a dashboard that had in fact been created.
+ *
+ * `ON CONFLICT DO UPDATE` makes the two orderings equivalent instead of one of them fatal. `set` only
+ * carries the fields the caller actually passed, so whichever request lands second updates its own column
+ * and leaves the other's alone.
+ *
+ * The `where` is not decoration. `dashboards.id` is a GLOBAL primary key fed by a slug, so two accounts
+ * naming a dashboard the same thing collide — and without this, the second one's write would silently
+ * take over the first one's row. With it, the update matches nothing and the write is dropped. That is
+ * still wrong, but it is wrong in the direction of not handing someone another account's dashboard, and
+ * the real fix is a composite key (see TODO.md).
+ */
 export async function upsertDashboard(userId: number, id: string, data: UpsertDashboardData): Promise<void> {
   const now = new Date();
-  if (await updateDashboard(userId, id, data)) return;
 
-  await db.insert(dashboards).values({
-    id,
-    userId,
-    name: data.name ?? id,
-    config: data.config ?? {},
-    layout: data.layout ?? null,
-    terminals: data.terminals ?? {},
-    hostTerminals: data.hostTerminals ?? {},
-    sortOrder: data.sortOrder ?? 0,
-    createdAt: now,
-    updatedAt: now,
-  });
+  await db
+    .insert(dashboards)
+    .values({
+      id,
+      userId,
+      name: data.name ?? id,
+      config: data.config ?? {},
+      layout: data.layout ?? null,
+      terminals: data.terminals ?? {},
+      hostTerminals: data.hostTerminals ?? {},
+      sortOrder: data.sortOrder ?? 0,
+      createdAt: now,
+      updatedAt: now,
+    })
+    .onConflictDoUpdate({
+      target: dashboards.id,
+      set: buildDashboardSet(data, now),
+      where: eq(dashboards.userId, userId),
+    });
 }
 
 /**