diff --git a/CHANGELOG.md b/CHANGELOG.md
index ce63b3e..20a299e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- VMID-Allokator-Migration mit transaktionssicherer Reservation pro Cluster angelegt.
 - VMs-und-SSH-Keys-Migration mit Ressourcen-Mapping und eindeutigem Proxmox-VMID-Index angelegt.
 - Cluster-Migration fuer Proxmox-Verbindungen mit `encrypted_token bytea` angelegt.
 - Projekte-und-Quotas-Migration mit Defaults und Constraints angelegt.
diff --git a/TODO.md b/TODO.md
index aec39d2..20c9bdc 100644
--- a/TODO.md
+++ b/TODO.md
@@ -54,6 +54,11 @@ Arbeitsliste auf Basis von `proxmox-console-entwicklungsplan.md`. Die Entwurfsda
   - [x] VMs referenzieren eindeutig Projekt und Cluster
   - [x] Unique-Index auf `(cluster_id, proxmox_vmid)` gesetzt
   - [x] Ressourcen- und Pflichtfeld-Checks gesetzt
+- [x] E2-T06: VMID-Allokator
+  - [x] Clusterweite Allocator-Tabelle angelegt
+  - [x] VMID-Reservationen vor Proxmox-Calls modelliert
+  - [x] Transaktionssichere Funktion `reserve_next_vmid(cluster_id)` mit `SELECT ... FOR UPDATE` angelegt
+  - [x] Concurrency-Test mit 50 parallelen Reservierungen lokal verifiziert
 
 ## MVP-Backlog
 
@@ -97,3 +102,4 @@ Arbeitsliste auf Basis von `proxmox-console-entwicklungsplan.md`. Die Entwurfsda
 - 2026-06-10: Projekte-und-Quotas-Migration `0003_projects_and_quotas` angelegt und lokal gegen Supabase verifiziert.
 - 2026-06-10: Cluster-Migration `0004_clusters` angelegt und lokal gegen Supabase verifiziert.
 - 2026-06-10: VMs-und-SSH-Keys-Migration `0005_vms_and_ssh_keys` angelegt und lokal gegen Supabase verifiziert.
+- 2026-06-10: VMID-Allokator-Migration `0006_vmid_allocator` angelegt und mit 50 parallelen Reservierungen lokal gegen Supabase verifiziert.
diff --git a/migrations/0006_vmid_allocator.down.sql b/migrations/0006_vmid_allocator.down.sql
new file mode 100644
index 0000000..6050b2b
--- /dev/null
+++ b/migrations/0006_vmid_allocator.down.sql
@@ -0,0 +1,6 @@
+DROP FUNCTION IF EXISTS public.reserve_next_vmid(uuid);
+DROP INDEX IF EXISTS public.vmid_reservations_cluster_id_idx;
+DROP INDEX IF EXISTS public.vmid_reservations_reserved_key;
+DROP TABLE IF EXISTS public.vmid_reservations;
+DROP TABLE IF EXISTS public.cluster_vmid_allocators;
+DROP TYPE IF EXISTS public.vmid_reservation_status;
diff --git a/migrations/0006_vmid_allocator.up.sql b/migrations/0006_vmid_allocator.up.sql
new file mode 100644
index 0000000..af083c4
--- /dev/null
+++ b/migrations/0006_vmid_allocator.up.sql
@@ -0,0 +1,71 @@
+CREATE TYPE public.vmid_reservation_status AS ENUM ('reserved', 'released');
+
+CREATE TABLE public.cluster_vmid_allocators (
+	cluster_id uuid PRIMARY KEY REFERENCES public.clusters(id) ON DELETE CASCADE,
+	next_vmid integer NOT NULL DEFAULT 100,
+	created_at timestamptz NOT NULL DEFAULT now(),
+	updated_at timestamptz NOT NULL DEFAULT now(),
+	CONSTRAINT cluster_vmid_allocators_next_vmid_check CHECK (next_vmid > 0)
+);
+
+CREATE TABLE public.vmid_reservations (
+	id uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+	cluster_id uuid NOT NULL REFERENCES public.clusters(id) ON DELETE CASCADE,
+	proxmox_vmid integer NOT NULL,
+	status public.vmid_reservation_status NOT NULL DEFAULT 'reserved',
+	created_at timestamptz NOT NULL DEFAULT now(),
+	updated_at timestamptz NOT NULL DEFAULT now(),
+	CONSTRAINT vmid_reservations_proxmox_vmid_check CHECK (proxmox_vmid > 0)
+);
+
+CREATE UNIQUE INDEX vmid_reservations_reserved_key
+	ON public.vmid_reservations (cluster_id, proxmox_vmid)
+	WHERE status = 'reserved';
+
+CREATE INDEX vmid_reservations_cluster_id_idx ON public.vmid_reservations (cluster_id);
+
+CREATE OR REPLACE FUNCTION public.reserve_next_vmid(p_cluster_id uuid)
+RETURNS integer
+LANGUAGE plpgsql
+AS $$
+DECLARE
+	candidate integer;
+BEGIN
+	INSERT INTO public.cluster_vmid_allocators (cluster_id)
+	VALUES (p_cluster_id)
+	ON CONFLICT (cluster_id) DO NOTHING;
+
+	SELECT next_vmid
+	INTO candidate
+	FROM public.cluster_vmid_allocators
+	WHERE cluster_id = p_cluster_id
+	FOR UPDATE;
+
+	LOOP
+		EXIT WHEN NOT EXISTS (
+			SELECT 1
+			FROM public.vms
+			WHERE cluster_id = p_cluster_id
+				AND proxmox_vmid = candidate
+		) AND NOT EXISTS (
+			SELECT 1
+			FROM public.vmid_reservations
+			WHERE cluster_id = p_cluster_id
+				AND proxmox_vmid = candidate
+				AND status = 'reserved'
+		);
+
+		candidate := candidate + 1;
+	END LOOP;
+
+	INSERT INTO public.vmid_reservations (cluster_id, proxmox_vmid)
+	VALUES (p_cluster_id, candidate);
+
+	UPDATE public.cluster_vmid_allocators
+	SET next_vmid = candidate + 1,
+		updated_at = now()
+	WHERE cluster_id = p_cluster_id;
+
+	RETURN candidate;
+END;
+$$;