diff --git a/app/Actions/OpenSubscription.php b/app/Actions/OpenSubscription.php
new file mode 100644
index 0000000..9ead25d
--- /dev/null
+++ b/app/Actions/OpenSubscription.php
@@ -0,0 +1,52 @@
+<?php
+
+namespace App\Actions;
+
+use App\Models\Order;
+use App\Models\Subscription;
+
+/**
+ * Opens the contract a paid order bought.
+ *
+ * This is the moment the catalogue stops applying. Everything the customer is
+ * owed — price, quotas, seats, the hardware behind the plan — is copied onto
+ * the subscription here and never read from the catalogue again. Provisioning
+ * sizes the machine from this row, so an operator editing a plan afterwards
+ * cannot reach a customer who has already paid.
+ *
+ * `price_cents` is the catalogue's NET price, which is what PlanChange prorates
+ * against — deliberately not `Order::amount_cents`, which holds the GROSS total
+ * Stripe actually charged. The two can legitimately differ (VAT, and later
+ * coupons), and reconciling them is not this action's job: the proof register
+ * records what was charged per event, and Stripe's invoice is the authority for
+ * the amount. Copying a gross total into this net field would silently corrupt
+ * every pro-rata calculation that reads it.
+ */
+class OpenSubscription
+{
+    public function __invoke(Order $order, string $term = Subscription::TERM_MONTHLY): Subscription
+    {
+        // A retried webhook must not open a second contract for one purchase.
+        $existing = Subscription::query()->where('order_id', $order->id)->first();
+
+        if ($existing !== null) {
+            return $existing;
+        }
+
+        $start = now();
+
+        return Subscription::create(array_merge(
+            Subscription::snapshotFrom($order->plan, $term),
+            [
+                'customer_id' => $order->customer_id,
+                'order_id' => $order->id,
+                'started_at' => $start,
+                'current_period_start' => $start,
+                'current_period_end' => $term === Subscription::TERM_YEARLY
+                    ? $start->copy()->addYear()
+                    : $start->copy()->addMonth(),
+                'status' => 'active',
+            ],
+        ));
+    }
+}
diff --git a/app/Actions/StartCustomerProvisioning.php b/app/Actions/StartCustomerProvisioning.php
index c1f7b01..1ee2e76 100644
--- a/app/Actions/StartCustomerProvisioning.php
+++ b/app/Actions/StartCustomerProvisioning.php
@@ -5,6 +5,7 @@ namespace App\Actions;
 use App\Models\Customer;
 use App\Models\Order;
 use App\Models\ProvisioningRun;
+use App\Models\Subscription;
 use App\Provisioning\Jobs\AdvanceRunJob;
 use Illuminate\Database\UniqueConstraintViolationException;
 use Illuminate\Support\Facades\DB;
@@ -16,6 +17,8 @@ use Illuminate\Support\Facades\DB;
  */
 class StartCustomerProvisioning
 {
+    public function __construct(private OpenSubscription $openSubscription) {}
+
     /**
      * @param  array{id:string,email:string,name:?string,stripe_customer_id:?string,plan:string,datacenter:string,amount_cents:int,currency:string}  $event
      */
@@ -28,8 +31,10 @@ class StartCustomerProvisioning
         $customer = $this->resolveCustomer($event);
         $customer->ensureUser(); // portal login (also enables admin impersonation)
 
+        $openSubscription = $this->openSubscription;
+
         try {
-            [$order, $run] = DB::transaction(function () use ($event, $customer) {
+            [$order, $run] = DB::transaction(function () use ($event, $customer, $openSubscription) {
                 $order = Order::create([
                     'customer_id' => $customer->id,
                     'plan' => $event['plan'],
@@ -40,6 +45,24 @@ class StartCustomerProvisioning
                     'status' => 'paid',
                 ]);
 
+                // Freeze what they bought, now, while the catalogue still says
+                // what they were shown.
+                //
+                // Two cases are deliberately left WITHOUT a contract: a plan the
+                // catalogue does not know, and a payment in a currency the
+                // catalogue cannot express — freezing a EUR price onto a CHF
+                // payment would put the contract and the payment in permanent
+                // disagreement. Both still record the order, so the payment is
+                // traceable, and the run then fails visibly at ValidateOrder.
+                // Throwing here instead would roll the order back and leave
+                // Stripe retrying a webhook that can never succeed.
+                $sellable = Subscription::knowsPlan($order->plan)
+                    && strtoupper((string) $order->currency) === Subscription::catalogueCurrency();
+
+                if ($sellable) {
+                    $openSubscription($order);
+                }
+
                 $run = ProvisioningRun::create([
                     'subject_type' => Order::class,
                     'subject_id' => $order->id,
diff --git a/app/Models/Instance.php b/app/Models/Instance.php
index 84fcd44..b6484fa 100644
--- a/app/Models/Instance.php
+++ b/app/Models/Instance.php
@@ -7,6 +7,7 @@ use Illuminate\Database\Eloquent\Factories\HasFactory;
 use Illuminate\Database\Eloquent\Model;
 use Illuminate\Database\Eloquent\Relations\BelongsTo;
 use Illuminate\Database\Eloquent\Relations\HasMany;
+use Illuminate\Database\Eloquent\Relations\HasOne;
 
 class Instance extends Model
 {
@@ -48,6 +49,15 @@ class Instance extends Model
         return $this->belongsTo(Order::class);
     }
 
+    /**
+     * The contract this machine fulfils. The authority on what the customer is
+     * entitled to — the catalogue only describes what we sell today.
+     */
+    public function subscription(): HasOne
+    {
+        return $this->hasOne(Subscription::class);
+    }
+
     public function host(): BelongsTo
     {
         return $this->belongsTo(Host::class);
diff --git a/app/Models/Order.php b/app/Models/Order.php
index e84e361..db4b645 100644
--- a/app/Models/Order.php
+++ b/app/Models/Order.php
@@ -85,6 +85,12 @@ class Order extends Model implements ProvisioningSubject
         return $this->hasOne(Instance::class);
     }
 
+    /** The contract this order opened, if it was the purchase that opened one. */
+    public function subscription(): HasOne
+    {
+        return $this->hasOne(Subscription::class);
+    }
+
     public function runs(): MorphMany
     {
         return $this->morphMany(ProvisioningRun::class, 'subject');
diff --git a/app/Models/Subscription.php b/app/Models/Subscription.php
index 6d8d3b8..4be6deb 100644
--- a/app/Models/Subscription.php
+++ b/app/Models/Subscription.php
@@ -53,6 +53,7 @@ class Subscription extends Model
             'ram_mb' => 'integer',
             'cores' => 'integer',
             'disk_gb' => 'integer',
+            'template_vmid' => 'integer',
             'tier' => 'integer',
             'started_at' => 'datetime',
             'current_period_start' => 'datetime',
@@ -72,11 +73,28 @@ class Subscription extends Model
         return $this->belongsTo(Customer::class);
     }
 
+    public function order(): BelongsTo
+    {
+        return $this->belongsTo(Order::class);
+    }
+
     public function instance(): BelongsTo
     {
         return $this->belongsTo(Instance::class);
     }
 
+    /** Whether the catalogue still sells this plan at all. */
+    public static function knowsPlan(string $plan): bool
+    {
+        return (array) config("provisioning.plans.{$plan}") !== [];
+    }
+
+    /** The single currency every catalogue price is expressed in. */
+    public static function catalogueCurrency(): string
+    {
+        return strtoupper((string) config('provisioning.currency', 'EUR'));
+    }
+
     /** Take today's catalogue entry and freeze it onto a new subscription. */
     public static function snapshotFrom(string $plan, string $term = self::TERM_MONTHLY): array
     {
@@ -100,7 +118,7 @@ class Subscription extends Model
             // A yearly term is twelve months of the same price. Any discount
             // belongs in the catalogue, not hidden in this conversion.
             'price_cents' => $term === self::TERM_YEARLY ? $monthly * 12 : $monthly,
-            'currency' => 'EUR',
+            'currency' => self::catalogueCurrency(),
             'quota_gb' => (int) ($catalogue['quota_gb'] ?? 0),
             'traffic_gb' => (int) ($catalogue['traffic_gb'] ?? 0),
             'seats' => (int) ($catalogue['seats'] ?? 0),
@@ -108,6 +126,9 @@ class Subscription extends Model
             'cores' => (int) ($catalogue['cores'] ?? 0),
             'disk_gb' => (int) ($catalogue['disk_gb'] ?? 0),
             'performance' => $catalogue['performance'] ?? null,
+            // Copied so provisioning never has to ask the catalogue what to
+            // clone. Not in FROZEN — see the migration for why.
+            'template_vmid' => isset($catalogue['template_vmid']) ? (int) $catalogue['template_vmid'] : null,
             // Frozen too: which direction a later change goes must not depend
             // on where the plan sits in today's catalogue.
             'tier' => (int) ($catalogue['tier'] ?? 0),
diff --git a/app/Provisioning/Steps/Customer/CustomerStep.php b/app/Provisioning/Steps/Customer/CustomerStep.php
index c105652..2a38490 100644
--- a/app/Provisioning/Steps/Customer/CustomerStep.php
+++ b/app/Provisioning/Steps/Customer/CustomerStep.php
@@ -5,6 +5,7 @@ namespace App\Provisioning\Steps\Customer;
 use App\Models\Instance;
 use App\Models\Order;
 use App\Models\ProvisioningRun;
+use App\Models\Subscription;
 use App\Provisioning\Contracts\ProvisioningStep;
 use App\Provisioning\Steps\ManagesRunResources;
 use App\Services\Proxmox\ProxmoxClient;
@@ -43,10 +44,35 @@ abstract class CustomerStep implements ProvisioningStep
         return $id ? Instance::query()->find($id) : null;
     }
 
-    /** @return array<string, mixed> */
+    /** The contract this run is carrying out, or null if none was opened. */
+    protected function subscription(ProvisioningRun $run): ?Subscription
+    {
+        return Subscription::query()->where('order_id', $this->order($run)->id)->first();
+    }
+
+    /**
+     * What the customer actually bought — read from their frozen snapshot, never
+     * from config('provisioning.plans').
+     *
+     * The catalogue says what we sell TODAY. Sizing a machine from it would mean
+     * that shrinking a plan resizes the VM of a customer who bought the larger
+     * one, on their next run. Empty when no contract exists, so ValidateOrder
+     * can fail the run closed instead of quietly falling back to the catalogue.
+     *
+     * @return array<string, mixed>
+     */
     protected function plan(ProvisioningRun $run): array
     {
-        return config('provisioning.plans.'.$this->order($run)->plan, []);
+        $subscription = $this->subscription($run);
+
+        if ($subscription === null) {
+            return [];
+        }
+
+        return $subscription->only([
+            'plan', 'term', 'price_cents', 'currency', 'quota_gb', 'traffic_gb',
+            'seats', 'ram_mb', 'cores', 'disk_gb', 'performance', 'template_vmid', 'tier',
+        ]);
     }
 
     /**
diff --git a/app/Provisioning/Steps/Customer/ReserveResources.php b/app/Provisioning/Steps/Customer/ReserveResources.php
index 43039d1..43443f8 100644
--- a/app/Provisioning/Steps/Customer/ReserveResources.php
+++ b/app/Provisioning/Steps/Customer/ReserveResources.php
@@ -30,10 +30,19 @@ class ReserveResources extends CustomerStep
         $existing = Instance::query()->where('order_id', $order->id)->first();
         if ($existing !== null) {
             $this->putContext($run, $existing);
+            $this->linkToSubscription($run, $existing);
 
             return StepResult::advance();
         }
 
+        $subscription = $this->subscription($run);
+
+        if ($subscription === null) {
+            return StepResult::fail('no_subscription');
+        }
+
+        // Sizes come from the contract, not the catalogue: this customer gets
+        // the machine they paid for even if the plan was edited since.
         $plan = $this->plan($run);
 
         // Place + create under a per-datacenter lock so concurrent reservations
@@ -63,11 +72,26 @@ class ReserveResources extends CustomerStep
         }
 
         $this->putContext($run, $instance);
+        $this->linkToSubscription($run, $instance);
         $this->recordResource($run, $instance->host, 'instance_id', (string) $instance->id);
 
         return StepResult::advance();
     }
 
+    /**
+     * Point the contract at the machine that fulfils it, so anything asking
+     * "what is this customer entitled to?" can get there from either end.
+     * instance_id is not part of the frozen snapshot, so this is allowed.
+     */
+    private function linkToSubscription(ProvisioningRun $run, Instance $instance): void
+    {
+        $subscription = $this->subscription($run);
+
+        if ($subscription !== null && $subscription->instance_id !== $instance->id) {
+            $subscription->update(['instance_id' => $instance->id]);
+        }
+    }
+
     private function putContext(ProvisioningRun $run, Instance $instance): void
     {
         $run->mergeContext([
diff --git a/app/Provisioning/Steps/Customer/ValidateOrder.php b/app/Provisioning/Steps/Customer/ValidateOrder.php
index 4fed5db..b7a376d 100644
--- a/app/Provisioning/Steps/Customer/ValidateOrder.php
+++ b/app/Provisioning/Steps/Customer/ValidateOrder.php
@@ -24,8 +24,11 @@ class ValidateOrder extends CustomerStep
         if (! in_array($order->status, ['paid', 'provisioning'], true)) {
             return StepResult::fail('order_not_paid');
         }
+        // Fail closed. No contract means nothing frozen to build from, and
+        // sizing the machine from today's catalogue instead is exactly the bug
+        // the snapshot exists to prevent.
         if ($this->plan($run) === []) {
-            return StepResult::fail('unknown_plan');
+            return StepResult::fail('no_subscription');
         }
         if (blank($order->datacenter)) {
             return StepResult::fail('invalid_datacenter');
diff --git a/app/Services/Traffic/TrafficMeter.php b/app/Services/Traffic/TrafficMeter.php
index 4815896..ef98583 100644
--- a/app/Services/Traffic/TrafficMeter.php
+++ b/app/Services/Traffic/TrafficMeter.php
@@ -37,10 +37,20 @@ final readonly class TrafficMeter
         );
     }
 
-    /** Plan allowance plus purchased add-on packs. */
+    /**
+     * Plan allowance plus purchased add-on packs.
+     *
+     * The allowance comes from the customer's contract, not from today's
+     * catalogue: cutting a plan's traffic must not start throttling someone who
+     * bought the larger allowance. Instances provisioned before contracts
+     * existed have none, and for those the catalogue is still the only answer —
+     * that fallback goes away once Phase 2 backfills them.
+     */
     public static function quotaGb(Instance $instance): int
     {
-        $plan = (int) (config("provisioning.plans.{$instance->plan}.traffic_gb") ?? 0);
+        $plan = (int) ($instance->subscription?->traffic_gb
+            ?? config("provisioning.plans.{$instance->plan}.traffic_gb")
+            ?? 0);
         $addonGb = (int) config('provisioning.traffic.addon.gb', 1000);
 
         return $plan + ($instance->traffic_addons ?? 0) * $addonGb;
diff --git a/config/provisioning.php b/config/provisioning.php
index 2faca93..f4555ff 100644
--- a/config/provisioning.php
+++ b/config/provisioning.php
@@ -62,6 +62,11 @@ return [
         ],
     ],
 
+    // The one currency the catalogue is priced in. Plan prices carry no currency
+    // of their own, so a payment in anything else cannot be frozen onto a
+    // contract without the contract and the payment disagreeing forever.
+    'currency' => env('CLUPILOT_CURRENCY', 'EUR'),
+
     // Plan → resource sizing + monthly price + Nextcloud blueprint template VMID.
     // quota_gb/disk_gb/ram_mb/cores drive infrastructure placement and are
     // ADMIN-ONLY. Customers compare seats, storage, performance class and
diff --git a/database/factories/OrderFactory.php b/database/factories/OrderFactory.php
index 8cd8ee4..48cfdee 100644
--- a/database/factories/OrderFactory.php
+++ b/database/factories/OrderFactory.php
@@ -2,8 +2,10 @@
 
 namespace Database\Factories;
 
+use App\Actions\OpenSubscription;
 use App\Models\Customer;
 use App\Models\Order;
+use App\Models\Subscription;
 use Illuminate\Database\Eloquent\Factories\Factory;
 
 /** @extends Factory<Order> */
@@ -22,4 +24,18 @@ class OrderFactory extends Factory
             'status' => 'paid',
         ];
     }
+
+    /**
+     * A purchase that opened a contract — what a paid order looks like in
+     * production, and what provisioning now requires. An unknown plan is left
+     * without one on purpose, so the fail-closed path stays testable.
+     */
+    public function withSubscription(string $term = Subscription::TERM_MONTHLY): static
+    {
+        return $this->afterCreating(function (Order $order) use ($term) {
+            if (Subscription::knowsPlan($order->plan)) {
+                app(OpenSubscription::class)($order, $term);
+            }
+        });
+    }
 }
diff --git a/database/migrations/2026_07_26_030000_link_subscriptions_to_orders.php b/database/migrations/2026_07_26_030000_link_subscriptions_to_orders.php
new file mode 100644
index 0000000..040ea62
--- /dev/null
+++ b/database/migrations/2026_07_26_030000_link_subscriptions_to_orders.php
@@ -0,0 +1,177 @@
+<?php
+
+use Illuminate\Database\Migrations\Migration;
+use Illuminate\Database\Schema\Blueprint;
+use Illuminate\Support\Carbon;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Schema;
+use Illuminate\Support\Str;
+
+/**
+ * Gives provisioning a way to reach the contract, and the contract everything
+ * provisioning needs.
+ *
+ * Until now the pipeline re-read config/provisioning.php by the order's plan
+ * name, so the snapshot protected the customer's price but not their machine:
+ * shrinking a plan resized an existing customer's VM on the next run. The
+ * pipeline's subject is the order, so the order is how it finds the snapshot.
+ */
+return new class extends Migration
+{
+    public function up(): void
+    {
+        Schema::table('subscriptions', function (Blueprint $table) {
+            // The order that opened this contract. Unique, because one purchase
+            // opens one contract — later upgrades and add-ons are their own
+            // orders against the same subscription, never new subscriptions.
+            $table->foreignId('order_id')->nullable()->unique()->after('customer_id')
+                ->constrained()->nullOnDelete();
+
+            // The blueprint the customer's VM is cloned from. Frozen here so the
+            // pipeline stops reading the live catalogue — but deliberately NOT
+            // in Subscription::FROZEN: this is how we build the machine, not a
+            // condition the customer is owed, and an operator has to be able to
+            // point a contract at a replacement template when the old one is
+            // gone, without cancelling the contract to do it.
+            $table->unsignedInteger('template_vmid')->nullable()->after('performance');
+        });
+
+        $this->backfillContracts();
+    }
+
+    public function down(): void
+    {
+        Schema::table('subscriptions', function (Blueprint $table) {
+            $table->dropConstrainedForeignId('order_id');
+            $table->dropColumn('template_vmid');
+        });
+
+        // Backfilled contracts are deliberately left in place. Deleting a
+        // customer's contract to undo a schema change would destroy the record
+        // of what they are owed; a stale row is the lesser harm.
+    }
+
+    /**
+     * Give every order that already bought something the contract it should
+     * always have had.
+     *
+     * Provisioning now fails closed without one, so an order that is paid or
+     * mid-flight when this deploys would otherwise stop dead at ValidateOrder.
+     *
+     * Everything is inlined rather than routed through Subscription — a
+     * migration has to keep working when the model moves on.
+     */
+    private function backfillContracts(): void
+    {
+        $plans = (array) config('provisioning.plans');
+        $currency = strtoupper((string) config('provisioning.currency', 'EUR'));
+
+        $orders = DB::table('orders')
+            ->where('type', 'new')  // only a purchase opens a contract
+            ->where(function ($query) {
+                $query
+                    ->whereIn('status', ['paid', 'provisioning', 'active'])
+                    // A failed run does not undo a payment: onProvisioningFailed()
+                    // marks the order failed and refunds nothing, and from now on
+                    // such an order keeps the contract opened before provisioning
+                    // ever started. Backfill matches that — but only where the
+                    // money is evidenced, since an order that was never paid can
+                    // end up failed too. Only the paid webhook sets
+                    // stripe_event_id; the cart leaves it null and pending.
+                    ->orWhere(fn ($paid) => $paid
+                        ->where('status', 'failed')
+                        ->whereNotNull('stripe_event_id'));
+            })
+            ->orderBy('id')
+            ->get();
+
+        foreach ($orders as $order) {
+            if (DB::table('subscriptions')->where('order_id', $order->id)->exists()) {
+                continue;
+            }
+
+            $plan = $plans[$order->plan] ?? null;
+
+            if ($plan === null) {
+                continue; // a plan we no longer sell: nothing left to reconstruct from
+            }
+
+            // A payment in a currency the catalogue cannot express gets no
+            // contract, exactly as the checkout path refuses one — writing an
+            // EUR price against a CHF payment would bake in a disagreement.
+            if (strtoupper((string) $order->currency) !== $currency) {
+                continue;
+            }
+
+            // What was actually delivered outranks what the catalogue says now:
+            // the catalogue may already have drifted from what this customer was
+            // sold, and the running machine is the honest record of their terms.
+            $instance = DB::table('instances')->where('order_id', $order->id)->first();
+
+            // A contract may already exist and simply have no order_id, because
+            // nothing set one before this migration. Adopt it rather than open a
+            // second: two active contracts for one purchase make "what is this
+            // customer owed?" unanswerable, and its frozen terms are the real
+            // ones — reconstructing them from the catalogue would be a guess.
+            $orphan = DB::table('subscriptions')
+                ->whereNull('order_id')
+                ->where('customer_id', $order->customer_id)
+                ->where('plan', $order->plan)
+                ->when(
+                    $instance !== null,
+                    fn ($q) => $q->where(fn ($m) => $m->where('instance_id', $instance->id)->orWhereNull('instance_id')),
+                    fn ($q) => $q->whereNull('instance_id'),
+                )
+                ->orderBy('id')
+                ->first();
+
+            if ($orphan !== null) {
+                DB::table('subscriptions')->where('id', $orphan->id)->update(array_filter([
+                    'order_id' => $order->id,
+                    // Fill only what is missing. The snapshot itself is left
+                    // untouched: it is what this customer was actually sold.
+                    'instance_id' => $orphan->instance_id ?? $instance->id ?? null,
+                    'template_vmid' => $orphan->template_vmid
+                        ?? (isset($plan['template_vmid']) ? (int) $plan['template_vmid'] : null),
+                    'updated_at' => now(),
+                ], fn ($value) => $value !== null));
+
+                continue;
+            }
+
+            // Anchor the term on the purchase and roll it forward to the period
+            // that is running now, so the next renewal lands where it should.
+            $start = Carbon::parse($order->created_at);
+            $end = $start->copy()->addMonth();
+            while ($end->isPast()) {
+                $end->addMonth();
+            }
+
+            DB::table('subscriptions')->insert([
+                'uuid' => (string) Str::uuid(),
+                'customer_id' => $order->customer_id,
+                'order_id' => $order->id,
+                'instance_id' => $instance->id ?? null,
+                'plan' => $order->plan,
+                'tier' => (int) ($plan['tier'] ?? 0),
+                'term' => 'monthly',
+                'price_cents' => (int) ($plan['price_cents'] ?? 0),
+                'currency' => $currency,
+                'quota_gb' => (int) ($instance->quota_gb ?? $plan['quota_gb'] ?? 0),
+                'traffic_gb' => (int) ($plan['traffic_gb'] ?? 0),
+                'seats' => (int) ($plan['seats'] ?? 0),
+                'ram_mb' => (int) ($instance->ram_mb ?? $plan['ram_mb'] ?? 0),
+                'cores' => (int) ($instance->cores ?? $plan['cores'] ?? 0),
+                'disk_gb' => (int) ($instance->disk_gb ?? $plan['disk_gb'] ?? 0),
+                'performance' => $plan['performance'] ?? null,
+                'template_vmid' => isset($plan['template_vmid']) ? (int) $plan['template_vmid'] : null,
+                'started_at' => $start,
+                'current_period_start' => $end->copy()->subMonth(),
+                'current_period_end' => $end,
+                'status' => 'active',
+                'created_at' => now(),
+                'updated_at' => now(),
+            ]);
+        }
+    }
+};
diff --git a/phpunit.xml b/phpunit.xml
index 50f2621..e1bffaa 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -30,6 +30,11 @@
         <!-- Fixed test key: storing a VPN config must be exercised, and a
              random one would make a decryption failure irreproducible. -->
         <env name="VPN_CONFIG_KEY" value="Y2x1cGlsb3QtdGVzdC1vbmx5LXZwbi1rZXktMzJieXQ=" force="true"/>
+        <!-- Blank so the suite never picks up the operator's real webhook secret
+             from .env: with one set, every unsigned test payload is rejected as
+             an invalid signature. The two tests that DO exercise verification
+             set the secret themselves. -->
+        <env name="STRIPE_WEBHOOK_SECRET" value="" force="true"/>
         <env name="APP_MAINTENANCE_DRIVER" value="file"/>
         <env name="BCRYPT_ROUNDS" value="4" force="true"/>
         <env name="BROADCAST_CONNECTION" value="null" force="true"/>
diff --git a/tests/Feature/Provisioning/CustomerProvisioningEndToEndTest.php b/tests/Feature/Provisioning/CustomerProvisioningEndToEndTest.php
index 7ab87b0..d899641 100644
--- a/tests/Feature/Provisioning/CustomerProvisioningEndToEndTest.php
+++ b/tests/Feature/Provisioning/CustomerProvisioningEndToEndTest.php
@@ -20,7 +20,7 @@ it('provisions a paid order all the way to active (mocked)', function () {
     // Fake defaults: tasks stopped/OK, guest agent up, cert reachable.
 
     Host::factory()->active()->create(['datacenter' => 'fsn', 'node' => 'pve', 'total_gb' => 1000]);
-    $order = Order::factory()->create(['status' => 'paid', 'plan' => 'start', 'datacenter' => 'fsn']);
+    $order = Order::factory()->withSubscription()->create(['status' => 'paid', 'plan' => 'start', 'datacenter' => 'fsn']);
     $run = ProvisioningRun::factory()->create([
         'subject_type' => Order::class, 'subject_id' => $order->id, 'pipeline' => 'customer', 'context' => [],
     ]);
@@ -68,7 +68,7 @@ it('does not duplicate external resources when a step re-runs after a crash', fu
     $s['pve']->guestScript('occ status', 0, '{"installed":true,"maintenance":false}');
 
     Host::factory()->active()->create(['datacenter' => 'fsn', 'node' => 'pve', 'total_gb' => 1000]);
-    $order = Order::factory()->create(['status' => 'paid', 'plan' => 'start', 'datacenter' => 'fsn']);
+    $order = Order::factory()->withSubscription()->create(['status' => 'paid', 'plan' => 'start', 'datacenter' => 'fsn']);
     $run = ProvisioningRun::factory()->create([
         'subject_type' => Order::class, 'subject_id' => $order->id, 'pipeline' => 'customer', 'context' => [],
     ]);
diff --git a/tests/Feature/Provisioning/CustomerStepBaseTest.php b/tests/Feature/Provisioning/CustomerStepBaseTest.php
index 49ecb41..3cce1dc 100644
--- a/tests/Feature/Provisioning/CustomerStepBaseTest.php
+++ b/tests/Feature/Provisioning/CustomerStepBaseTest.php
@@ -6,7 +6,7 @@ use App\Models\ProvisioningRun;
 use Tests\Support\Steps\ProbeCustomerStep;
 
 it('resolves order, instance and plan from the run', function () {
-    $order = Order::factory()->create(['plan' => 'team']);
+    $order = Order::factory()->withSubscription()->create(['plan' => 'team']);
     $instance = Instance::factory()->create();
     $run = ProvisioningRun::factory()->create([
         'subject_type' => Order::class,
diff --git a/tests/Feature/Provisioning/CustomerStepsTest.php b/tests/Feature/Provisioning/CustomerStepsTest.php
index 42f07f1..d925782 100644
--- a/tests/Feature/Provisioning/CustomerStepsTest.php
+++ b/tests/Feature/Provisioning/CustomerStepsTest.php
@@ -27,7 +27,7 @@ use Illuminate\Support\Facades\Notification;
 /** A run whose order is paid but nothing is reserved yet. */
 function orderRun(array $attrs = [], array $context = []): ProvisioningRun
 {
-    $order = Order::factory()->create($attrs);
+    $order = Order::factory()->withSubscription()->create($attrs);
 
     return ProvisioningRun::factory()->create([
         'subject_type' => Order::class,
@@ -41,7 +41,7 @@ function orderRun(array $attrs = [], array $context = []): ProvisioningRun
 function reservedRun(array $extraContext = [], array $instanceAttrs = []): array
 {
     $host = Host::factory()->active()->create(['datacenter' => 'fsn', 'node' => 'pve']);
-    $order = Order::factory()->create(['datacenter' => 'fsn', 'plan' => 'start']);
+    $order = Order::factory()->withSubscription()->create(['datacenter' => 'fsn', 'plan' => 'start']);
     $instance = Instance::factory()->create(array_merge([
         'order_id' => $order->id, 'customer_id' => $order->customer_id,
         'host_id' => $host->id, 'vmid' => 101, 'status' => 'provisioning',
diff --git a/tests/Feature/Provisioning/SubscriptionSnapshotTest.php b/tests/Feature/Provisioning/SubscriptionSnapshotTest.php
new file mode 100644
index 0000000..446e989
--- /dev/null
+++ b/tests/Feature/Provisioning/SubscriptionSnapshotTest.php
@@ -0,0 +1,305 @@
+<?php
+
+use App\Actions\OpenSubscription;
+use App\Models\Host;
+use App\Models\Instance;
+use App\Models\Order;
+use App\Models\ProvisioningRun;
+use App\Models\Subscription;
+use App\Provisioning\Jobs\AdvanceRunJob;
+use App\Provisioning\Steps\Customer\CloneVirtualMachine;
+use App\Provisioning\Steps\Customer\ReserveResources;
+use App\Provisioning\Steps\Customer\ValidateOrder;
+use App\Services\Proxmox\ProxmoxClient;
+use Illuminate\Support\Facades\DB;
+use Illuminate\Support\Facades\Queue;
+
+/**
+ * The catalogue describes what we sell today. A customer who has already paid
+ * bought today's terms and keeps them — so once an order is paid, nothing the
+ * operator changes in the catalogue may reach that customer, not their price
+ * and not the machine they were promised.
+ */
+
+/** A paid order with its contract already opened, plus a host to place it on. */
+function paidOrderWithSubscription(string $plan = 'team'): array
+{
+    $host = Host::factory()->active()->create(['datacenter' => 'fsn', 'node' => 'pve']);
+    $order = Order::factory()->create(['datacenter' => 'fsn', 'plan' => $plan, 'status' => 'paid']);
+    $subscription = app(OpenSubscription::class)($order);
+
+    $run = ProvisioningRun::factory()->create([
+        'subject_type' => Order::class,
+        'subject_id' => $order->id,
+        'pipeline' => 'customer',
+        'context' => [],
+    ]);
+
+    return compact('host', 'order', 'subscription', 'run');
+}
+
+it('freezes the catalogue onto a subscription when the checkout is paid', function () {
+    Queue::fake();
+
+    $this->postJson(route('webhooks.stripe'), [
+        'id' => 'evt_snap',
+        'type' => 'checkout.session.completed',
+        'data' => ['object' => [
+            'id' => 'cs_snap',
+            'payment_status' => 'paid',
+            'customer_details' => ['email' => 'kunde@example.com', 'name' => 'Kanzlei Berger'],
+            'amount_total' => 17900,
+            'currency' => 'eur',
+            'metadata' => ['plan' => 'team', 'datacenter' => 'fsn'],
+        ]],
+    ])->assertOk();
+
+    $order = Order::query()->where('stripe_event_id', 'cs_snap')->sole();
+    $subscription = Subscription::query()->where('order_id', $order->id)->sole();
+
+    expect($subscription->plan)->toBe('team')
+        ->and($subscription->customer_id)->toBe($order->customer_id)
+        ->and($subscription->ram_mb)->toBe(8192)
+        ->and($subscription->disk_gb)->toBe(540)
+        ->and($subscription->price_cents)->toBe(17900)
+        ->and($subscription->tier)->toBe(2)
+        ->and($subscription->status)->toBe('active')
+        ->and($subscription->current_period_end->greaterThan($subscription->current_period_start))->toBeTrue();
+});
+
+it('opens exactly one contract when Stripe retries the webhook', function () {
+    Queue::fake();
+
+    $event = [
+        'id' => 'evt_twice',
+        'type' => 'checkout.session.completed',
+        'data' => ['object' => [
+            'id' => 'cs_twice',
+            'payment_status' => 'paid',
+            'customer_details' => ['email' => 'zwei@example.com'],
+            'amount_total' => 4900,
+            'currency' => 'eur',
+            'metadata' => ['plan' => 'start', 'datacenter' => 'fsn'],
+        ]],
+    ];
+
+    $this->postJson(route('webhooks.stripe'), $event)->assertOk();
+    $this->postJson(route('webhooks.stripe'), $event)->assertOk();
+
+    expect(Subscription::query()->count())->toBe(1);
+    Queue::assertPushed(AdvanceRunJob::class, 1);
+});
+
+it('sizes the machine from the contract, not from a catalogue edited afterwards', function () {
+    ['order' => $order, 'run' => $run] = paidOrderWithSubscription('team');
+
+    // The operator shrinks the team plan after this customer has paid for it.
+    config()->set('provisioning.plans.team.ram_mb', 4096);
+    config()->set('provisioning.plans.team.cores', 2);
+    config()->set('provisioning.plans.team.disk_gb', 120);
+    config()->set('provisioning.plans.team.quota_gb', 100);
+
+    expect(app(ReserveResources::class)->execute($run)->type)->toBe('advance');
+
+    $instance = Instance::query()->where('order_id', $order->id)->sole();
+
+    expect($instance->ram_mb)->toBe(8192)
+        ->and($instance->cores)->toBe(4)
+        ->and($instance->disk_gb)->toBe(540)
+        ->and($instance->quota_gb)->toBe(500);
+});
+
+it('links the instance back to the contract it was provisioned for', function () {
+    ['order' => $order, 'subscription' => $subscription, 'run' => $run] = paidOrderWithSubscription('team');
+
+    app(ReserveResources::class)->execute($run);
+
+    $instance = Instance::query()->where('order_id', $order->id)->sole();
+
+    expect($subscription->fresh()->instance_id)->toBe($instance->id);
+});
+
+it('clones the template the contract was sold with, not a later one', function () {
+    ['host' => $host, 'order' => $order, 'run' => $run] = paidOrderWithSubscription('team');
+
+    $instance = Instance::factory()->create([
+        'order_id' => $order->id, 'customer_id' => $order->customer_id,
+        'host_id' => $host->id, 'status' => 'provisioning',
+    ]);
+    $run->mergeContext(['instance_id' => $instance->id, 'host_id' => $host->id, 'node' => 'pve']);
+
+    // A new blueprint is published after this customer bought.
+    config()->set('provisioning.plans.team.template_vmid', 9999);
+
+    $cloned = null;
+    $pve = Mockery::mock(ProxmoxClient::class);
+    $pve->shouldReceive('forHost')->andReturnSelf();
+    $pve->shouldReceive('nextVmid')->andReturn(120);
+    $pve->shouldReceive('vmExists')->andReturn(false);
+    $pve->shouldReceive('cloneVm')->andReturnUsing(function ($node, $template, $vmid, $name) use (&$cloned) {
+        $cloned = $template;
+
+        return 'UPID:pve:clone';
+    });
+    $pve->shouldReceive('taskStatus')->andReturn(['status' => 'stopped', 'exitstatus' => 'OK']);
+
+    app()->instance(ProxmoxClient::class, $pve);
+
+    expect(app(CloneVirtualMachine::class)->execute($run->fresh())->type)->toBe('advance')
+        ->and($cloned)->toBe(9000);
+});
+
+it('backfills a contract for an order that was already paid before contracts existed', function () {
+    // An order from before this migration: paid, machine running, no contract.
+    $order = Order::factory()->create(['status' => 'active', 'plan' => 'team', 'created_at' => now()->subMonths(3)]);
+    $instance = Instance::factory()->create([
+        'order_id' => $order->id, 'customer_id' => $order->customer_id,
+        // Sized from a catalogue that has since been cut back.
+        'quota_gb' => 750, 'disk_gb' => 800, 'ram_mb' => 16384, 'cores' => 6,
+    ]);
+
+    $migration = require database_path('migrations/2026_07_26_030000_link_subscriptions_to_orders.php');
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+
+    $subscription = Subscription::query()->where('order_id', $order->id)->sole();
+
+    // Reconstructed from what was actually delivered, not from today's plan.
+    expect($subscription->ram_mb)->toBe(16384)
+        ->and($subscription->cores)->toBe(6)
+        ->and($subscription->disk_gb)->toBe(800)
+        ->and($subscription->quota_gb)->toBe(750)
+        ->and($subscription->instance_id)->toBe($instance->id)
+        ->and($subscription->status)->toBe('active')
+        // The term is anchored on the purchase and rolled forward to the period
+        // running now, so the next renewal lands on the right day.
+        ->and($subscription->started_at->toDateString())->toBe(now()->subMonths(3)->toDateString())
+        ->and($subscription->current_period_end->isFuture())->toBeTrue();
+
+    // Running it twice must not open a second contract.
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+    expect(Subscription::query()->where('order_id', $order->id)->count())->toBe(1);
+});
+
+it('backfills no contract for an order that never bought anything', function () {
+    // Never paid: the cart leaves an order pending with no Stripe event, and a
+    // run against it fails without any money having changed hands.
+    $failed = Order::factory()->create(['status' => 'failed', 'plan' => 'team', 'stripe_event_id' => null]);
+    $pending = Order::factory()->create(['status' => 'pending', 'plan' => 'team', 'stripe_event_id' => null]);
+
+    $migration = require database_path('migrations/2026_07_26_030000_link_subscriptions_to_orders.php');
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+
+    expect(Subscription::query()->whereIn('order_id', [$failed->id, $pending->id])->exists())->toBeFalse();
+});
+
+it('adopts a contract that already exists instead of opening a second one', function () {
+    $order = Order::factory()->create(['status' => 'active', 'plan' => 'team']);
+    $instance = Instance::factory()->create(['order_id' => $order->id, 'customer_id' => $order->customer_id]);
+
+    // A contract from before anything set order_id — carrying terms that have
+    // since been cut from the catalogue.
+    $existing = Subscription::factory()->create([
+        'customer_id' => $order->customer_id,
+        'instance_id' => $instance->id,
+        'order_id' => null,
+        'template_vmid' => null,
+    ]);
+    DB::table('subscriptions')->where('id', $existing->id)->update(['ram_mb' => 32768]);
+
+    $migration = require database_path('migrations/2026_07_26_030000_link_subscriptions_to_orders.php');
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+
+    expect(Subscription::query()->where('customer_id', $order->customer_id)->count())->toBe(1);
+
+    $adopted = Subscription::query()->where('order_id', $order->id)->sole();
+
+    expect($adopted->id)->toBe($existing->id)
+        ->and($adopted->ram_mb)->toBe(32768)          // their real terms, not the catalogue's
+        ->and($adopted->template_vmid)->toBe(9000);   // only the missing piece filled in
+});
+
+it('backfills no contract for a payment the catalogue cannot price', function () {
+    $order = Order::factory()->create(['status' => 'active', 'plan' => 'team', 'currency' => 'CHF']);
+
+    $migration = require database_path('migrations/2026_07_26_030000_link_subscriptions_to_orders.php');
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+
+    expect(Subscription::query()->where('order_id', $order->id)->exists())->toBeFalse();
+});
+
+it('backfills a contract for a payment whose provisioning failed', function () {
+    // Nothing refunds this order — onProvisioningFailed() just marks it failed —
+    // so the customer is still owed what they paid for.
+    $order = Order::factory()->create([
+        'status' => 'failed', 'plan' => 'team', 'stripe_event_id' => 'cs_paid_then_failed',
+    ]);
+
+    $migration = require database_path('migrations/2026_07_26_030000_link_subscriptions_to_orders.php');
+    (new ReflectionMethod($migration, 'backfillContracts'))->invoke($migration);
+
+    expect(Subscription::query()->where('order_id', $order->id)->sole()->plan)->toBe('team');
+});
+
+it('refuses to provision an order that has no contract', function () {
+    $order = Order::factory()->create(['status' => 'paid', 'plan' => 'team']);
+    $run = ProvisioningRun::factory()->create([
+        'subject_type' => Order::class, 'subject_id' => $order->id, 'pipeline' => 'customer', 'context' => [],
+    ]);
+
+    $result = app(ValidateOrder::class)->execute($run);
+
+    expect($result->type)->toBe('fail')
+        ->and($result->reason)->toBe('no_subscription');
+});
+
+it('opens no contract for a payment in a currency the catalogue cannot express', function () {
+    Queue::fake();
+
+    $this->postJson(route('webhooks.stripe'), [
+        'id' => 'evt_chf',
+        'type' => 'checkout.session.completed',
+        'data' => ['object' => [
+            'id' => 'cs_chf',
+            'payment_status' => 'paid',
+            'customer_details' => ['email' => 'schweiz@example.com'],
+            'amount_total' => 17900,
+            'currency' => 'chf',
+            'metadata' => ['plan' => 'team', 'datacenter' => 'fsn'],
+        ]],
+    ])->assertOk();
+
+    // Freezing a EUR price onto a CHF payment would leave the contract and the
+    // payment disagreeing forever, so no contract is opened — but the payment
+    // is still recorded, and the run stops visibly instead of building anything.
+    $order = Order::query()->where('stripe_event_id', 'cs_chf')->sole();
+
+    expect($order->currency)->toBe('CHF')
+        ->and(Subscription::query()->where('order_id', $order->id)->exists())->toBeFalse();
+
+    $run = ProvisioningRun::query()->where('subject_id', $order->id)->sole();
+    expect(app(ValidateOrder::class)->execute($run)->reason)->toBe('no_subscription');
+});
+
+it('leaves a paid order behind when the plan is unknown, instead of losing the payment', function () {
+    Queue::fake();
+
+    $this->postJson(route('webhooks.stripe'), [
+        'id' => 'evt_ghost',
+        'type' => 'checkout.session.completed',
+        'data' => ['object' => [
+            'id' => 'cs_ghost',
+            'payment_status' => 'paid',
+            'customer_details' => ['email' => 'geist@example.com'],
+            'amount_total' => 4900,
+            'currency' => 'eur',
+            'metadata' => ['plan' => 'ghost', 'datacenter' => 'fsn'],
+        ]],
+    ])->assertOk();
+
+    // The order is recorded so the payment is traceable; the run fails visibly.
+    $order = Order::query()->where('stripe_event_id', 'cs_ghost')->sole();
+    expect(Subscription::query()->where('order_id', $order->id)->exists())->toBeFalse();
+
+    $run = ProvisioningRun::query()->where('subject_id', $order->id)->sole();
+    expect(app(ValidateOrder::class)->execute($run)->type)->toBe('fail');
+});
diff --git a/tests/Feature/TrafficTest.php b/tests/Feature/TrafficTest.php
index 69476be..0c16a57 100644
--- a/tests/Feature/TrafficTest.php
+++ b/tests/Feature/TrafficTest.php
@@ -128,6 +128,21 @@ it('counts add-on packs towards the allowance', function () {
     expect(TrafficMeter::quotaGb($instance->fresh()))->toBe(3000);
 });
 
+it('keeps the allowance the customer bought when the catalogue is cut', function () {
+    [, , $instance] = trafficSetup();
+
+    App\Models\Subscription::factory()->create([
+        'customer_id' => $instance->customer_id,
+        'instance_id' => $instance->id,
+        ...App\Models\Subscription::snapshotFrom('start'),
+    ]);
+
+    // Half the traffic off the start plan, after this customer bought it.
+    config()->set('provisioning.plans.start.traffic_gb', 500);
+
+    expect(TrafficMeter::quotaGb($instance->fresh()))->toBe(1000);
+});
+
 it('shows the customer what is left, and offers a top-up when it gets tight', function () {
     [, $customer, $instance] = trafficSetup();
     $user = User::factory()->create(['email' => $customer->email]);