diff --git a/prisma/migrations/20260901180000_move_remaining_umbral_sessions_to_1400_argentina/migration.sql b/prisma/migrations/20260901180000_move_remaining_umbral_sessions_to_1400_argentina/migration.sql
new file mode 100644
index 00000000..60b19a3d
--- /dev/null
+++ b/prisma/migrations/20260901180000_move_remaining_umbral_sessions_to_1400_argentina/migration.sql
@@ -0,0 +1,37 @@
+-- Sai moved the two remaining public-cycle sessions to 14:00 Argentina
+-- (America/Argentina/Cordoba, UTC-3), which is 17:00 UTC. Historical sessions
+-- keep their actual times. Access, facilitator and room state remain intact.
+WITH corrected_sessions ("id", "scheduled_at") AS (
+    VALUES
+        ('50000000-0000-4000-8000-202609050001'::uuid, '2026-09-05 17:00:00'::timestamp),
+        ('50000000-0000-4000-8000-202609120001'::uuid, '2026-09-12 17:00:00'::timestamp)
+)
+UPDATE "scheduled_sessions" AS session
+SET
+    "scheduled_at" = corrected_sessions."scheduled_at",
+    "updated_at" = CURRENT_TIMESTAMP
+FROM corrected_sessions
+WHERE session."id" = corrected_sessions."id"
+  AND session."status" = 'SCHEDULED'::"ScheduledSessionStatus";
+
+DO $$
+DECLARE
+    initialized_count integer;
+    corrected_count integer;
+BEGIN
+    SELECT count(*) INTO initialized_count FROM "users";
+
+    SELECT count(*) INTO corrected_count
+    FROM "scheduled_sessions"
+    WHERE ("id", "scheduled_at") IN (
+        ('50000000-0000-4000-8000-202609050001'::uuid, '2026-09-05 17:00:00'::timestamp),
+        ('50000000-0000-4000-8000-202609120001'::uuid, '2026-09-12 17:00:00'::timestamp)
+    )
+      AND "status" = 'SCHEDULED'::"ScheduledSessionStatus";
+
+    IF initialized_count = 0 AND corrected_count <> 0 THEN
+        RAISE EXCEPTION 'Empty installation contains a partial remaining Umbral cycle';
+    ELSIF initialized_count > 0 AND corrected_count <> 2 THEN
+        RAISE EXCEPTION 'Remaining Umbral sessions must both start at 17:00 UTC';
+    END IF;
+END $$;
diff --git a/src/lib/__tests__/public-cycle.test.ts b/src/lib/__tests__/public-cycle.test.ts
index cdc849ee..2a546df4 100644
--- a/src/lib/__tests__/public-cycle.test.ts
+++ b/src/lib/__tests__/public-cycle.test.ts
@@ -14,7 +14,7 @@ describe('public four-Saturday cycle', () => {
         expect(isPublicCycleSession('10000000-0000-4000-8000-000000000001')).toBe(false);
     });
 
-    it('keeps the final migration contract at the confirmed 16:00 UTC', () => {
+    it('preserves the historical four-session correction at 16:00 UTC', () => {
         const migration = readFileSync(
             new URL(
                 '../../../prisma/migrations/20260821194000_correct_four_saturday_cycle_start/migration.sql',
@@ -31,6 +31,22 @@ describe('public four-Saturday cycle', () => {
         expect(migration).not.toContain('14:00:00');
     });
 
+    it('moves only the two remaining sessions to 14:00 Argentina / 17:00 UTC', () => {
+        const migration = readFileSync(
+            new URL(
+                '../../../prisma/migrations/20260901180000_move_remaining_umbral_sessions_to_1400_argentina/migration.sql',
+                import.meta.url,
+            ),
+            'utf8',
+        );
+
+        expect(migration).toContain("'2026-09-05 17:00:00'::timestamp");
+        expect(migration).toContain("'2026-09-12 17:00:00'::timestamp");
+        expect(migration).not.toContain('2026-08-22 17:00:00');
+        expect(migration).not.toContain('2026-08-29 17:00:00');
+        expect(migration).toContain('corrected_count <> 2');
+    });
+
     it('recognizes only an entirely anonymous COMP entitlement for a reviewed public room', () => {
         const candidate = {
             staffUser: null,