diff --git a/packages/client-utils/CHANGELOG.md b/packages/client-utils/CHANGELOG.md
index 0d9765451c..e473a16d10 100644
--- a/packages/client-utils/CHANGELOG.md
+++ b/packages/client-utils/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- **BREAKING:** Make `chainId` required on `rampBuy` / `rampSell` `ActivityItem` variants, matching every other activity kind. `mapRampsOrder` now returns `null` when no CAIP chain id can be resolved from the order (empty or unparseable `network`, missing `cryptoCurrency.chainId` / `assetId`), instead of emitting an item with an undefined `chainId` ([#9777](https://github.com/MetaMask/core/pull/9777))
+
 ## [1.6.0]
 
 ### Added
diff --git a/packages/client-utils/src/mappers/ramps-order-mapper.test.ts b/packages/client-utils/src/mappers/ramps-order-mapper.test.ts
index 4adf272924..75ec0765c3 100644
--- a/packages/client-utils/src/mappers/ramps-order-mapper.test.ts
+++ b/packages/client-utils/src/mappers/ramps-order-mapper.test.ts
@@ -102,14 +102,14 @@ describe('mapRampsOrder', () => {
     expect(item?.status).toBe('pending');
   });
 
-  it('maps a precreated stub order with an empty chain id to an undefined chainId, not eip155:0', () => {
+  it('hides a precreated stub order with an empty chain id instead of mapping eip155:0', () => {
     const item = mapRampsOrder({
       ...baseOrder,
       network: { chainId: '' },
       cryptoCurrency: undefined,
     });
 
-    expect(item?.chainId).toBeUndefined();
+    expect(item).toBeNull();
   });
 
   it('falls through an unparseable network name to cryptoCurrency.chainId', () => {
@@ -139,24 +139,24 @@ describe('mapRampsOrder', () => {
     expect(item?.chainId).toBe('eip155:1');
   });
 
-  it('returns an undefined chainId when cryptoCurrency.assetId has no valid chain segment', () => {
+  it('hides an order when cryptoCurrency.assetId has no valid chain segment', () => {
     const item = mapRampsOrder({
       ...baseOrder,
       network: 'ethereum',
       cryptoCurrency: { assetId: 'not-an-asset-id', symbol: 'ETH' },
     });
 
-    expect(item?.chainId).toBeUndefined();
+    expect(item).toBeNull();
   });
 
-  it('returns an undefined chainId when network is an unparseable name and crypto currency has no chain', () => {
+  it('hides an order when network is an unparseable name and crypto currency has no chain', () => {
     const item = mapRampsOrder({
       ...baseOrder,
       network: 'ethereum',
       cryptoCurrency: undefined,
     });
 
-    expect(item?.chainId).toBeUndefined();
+    expect(item).toBeNull();
   });
 
   it.each(['0x', '0x0000'])(
diff --git a/packages/client-utils/src/mappers/ramps-order-mapper.ts b/packages/client-utils/src/mappers/ramps-order-mapper.ts
index 13709953ef..8794d31d53 100644
--- a/packages/client-utils/src/mappers/ramps-order-mapper.ts
+++ b/packages/client-utils/src/mappers/ramps-order-mapper.ts
@@ -143,13 +143,19 @@ function isPlausibleRampTxHash(txHash: string): boolean {
  *
  * @param order - The ramps order to map.
  * @returns The normalized activity item, or `null` if the order's status
- * should not be surfaced in the activity list.
+ * should not be surfaced in the activity list, or if no CAIP chain id can be
+ * resolved from the order.
  */
 export function mapRampsOrder(order: RampsOrderLike): ActivityItem | null {
   if (HIDDEN_STATUSES.has(order.status) || order.excludeFromPurchases) {
     return null;
   }
 
+  const chainId = resolveRampsOrderChainId(order);
+  if (!chainId) {
+    return null;
+  }
+
   // The V2 API returns `orderType` uppercased (e.g. `'BUY'`); normalize since
   // some call sites (e.g. locally-created stub orders) use lowercase. Transak
   // deposits (`'DEPOSIT'`) are a buy variant, not a sell.
@@ -184,8 +190,6 @@ export function mapRampsOrder(order: RampsOrderLike): ActivityItem | null {
     },
   ];
 
-  const chainId = resolveRampsOrderChainId(order);
-
   return {
     type: isBuy ? 'rampBuy' : 'rampSell',
     chainId,
diff --git a/packages/client-utils/src/types.ts b/packages/client-utils/src/types.ts
index 0aed7e8956..08c8c5c00c 100644
--- a/packages/client-utils/src/types.ts
+++ b/packages/client-utils/src/types.ts
@@ -176,34 +176,26 @@ export type ActivityItem =
         transactionProtocol?: string;
       }
     >
-  | (Omit<
-      ActivityData<
-        'rampBuy' | 'rampSell',
-        {
-          from?: string;
-          fiat?: FiatAmount;
-          token?: TokenAmount;
-          fees?: Fee[];
-          provider?: {
-            id?: string;
-            name?: string;
-            orderLink?: string;
-          };
-          statusDescription?: string;
-          paymentDetails?: RampOrderPaymentDetail[];
-          // Stable identifier for orders that may not have a hash yet (e.g. a
-          // ramp order pending fiat settlement, where `hash` is empty until it
-          // settles on-chain). Lives in `data` as a ramp-specific property.
+  | ActivityData<
+      'rampBuy' | 'rampSell',
+      {
+        from?: string;
+        fiat?: FiatAmount;
+        token?: TokenAmount;
+        fees?: Fee[];
+        provider?: {
           id?: string;
-        }
-      >,
-      'chainId'
-    > & {
-      // Precreated stub orders (see `RampsController.addPrecreatedOrder`) may
-      // not have an assigned network yet, so unlike every other activity
-      // kind, a ramp order's chain id isn't guaranteed.
-      chainId?: CaipChainId;
-    });
+          name?: string;
+          orderLink?: string;
+        };
+        statusDescription?: string;
+        paymentDetails?: RampOrderPaymentDetail[];
+        // Stable identifier for orders that may not have a hash yet (e.g. a
+        // ramp order pending fiat settlement, where `hash` is empty until it
+        // settles on-chain). Lives in `data` as a ramp-specific property.
+        id?: string;
+      }
+    >;
 
 // Note: Update core-backend
 export type ValueTransfer = _ValueTransfer & {
diff --git a/packages/ramps-controller/CHANGELOG.md b/packages/ramps-controller/CHANGELOG.md
index 2483f3bc0c..9ecedd1ecd 100644
--- a/packages/ramps-controller/CHANGELOG.md
+++ b/packages/ramps-controller/CHANGELOG.md
@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Changed
+
+- **BREAKING:** Require a non-empty `chainId` on `addPrecreatedOrder`. Callers must seed the selected token's chain so precreated stubs (and pending flips before API enrichment) always carry a network. Empty or whitespace `chainId` is a no-op, matching empty `orderId` handling. ([#9777](https://github.com/MetaMask/core/pull/9777))
+
 ## [19.0.0]
 
 ### Added
diff --git a/packages/ramps-controller/src/RampsController-method-action-types.ts b/packages/ramps-controller/src/RampsController-method-action-types.ts
index 714c11a3fc..3898e4fea1 100644
--- a/packages/ramps-controller/src/RampsController-method-action-types.ts
+++ b/packages/ramps-controller/src/RampsController-method-action-types.ts
@@ -321,7 +321,7 @@ export type RampsControllerGetBuyWidgetDataAction = {
  * @param params.orderId - Full order ID (e.g. "/providers/paypal/orders/abc123") or order code.
  * @param params.providerCode - Canonical provider code (e.g. "paypal", "transak").
  * @param params.walletAddress - Wallet address for the order.
- * @param params.chainId - Optional chain ID for the order.
+ * @param params.chainId - Chain ID for the order (decimal, hex, or CAIP-2). Must be non-empty.
  */
 export type RampsControllerAddPrecreatedOrderAction = {
   type: `RampsController:addPrecreatedOrder`;
diff --git a/packages/ramps-controller/src/RampsController.test.ts b/packages/ramps-controller/src/RampsController.test.ts
index cde0a1ca64..54dca251d3 100644
--- a/packages/ramps-controller/src/RampsController.test.ts
+++ b/packages/ramps-controller/src/RampsController.test.ts
@@ -8870,6 +8870,7 @@ describe('RampsController', () => {
         expect(stub?.provider?.id).toBe('paypal');
         expect(stub?.walletAddress).toBe('0xabc');
         expect(stub?.status).toBe(RampsOrderStatus.Precreated);
+        expect(stub?.network).toStrictEqual({ chainId: '1', name: '' });
       });
     });
 
@@ -8879,11 +8880,16 @@ describe('RampsController', () => {
           orderId: 'plain-order-id',
           providerCode: 'transak',
           walletAddress: '0xdef',
+          chainId: 'eip155:1',
         });
 
         expect(controller.state.orders[0]?.providerOrderId).toBe(
           'plain-order-id',
         );
+        expect(controller.state.orders[0]?.network).toStrictEqual({
+          chainId: 'eip155:1',
+          name: '',
+        });
       });
     });
 
@@ -8893,6 +8899,20 @@ describe('RampsController', () => {
           orderId: '/providers/paypal/orders/',
           providerCode: 'paypal',
           walletAddress: '0xabc',
+          chainId: '1',
+        });
+
+        expect(controller.state.orders).toHaveLength(0);
+      });
+    });
+
+    it('skips addOrder when chainId is empty or whitespace', async () => {
+      await withController(({ controller, rootMessenger }) => {
+        rootMessenger.call('RampsController:addPrecreatedOrder', {
+          orderId: '/providers/paypal/orders/abc123',
+          providerCode: 'paypal',
+          walletAddress: '0xabc',
+          chainId: '   ',
         });
 
         expect(controller.state.orders).toHaveLength(0);
diff --git a/packages/ramps-controller/src/RampsController.ts b/packages/ramps-controller/src/RampsController.ts
index d454386b80..3f88e46e0c 100644
--- a/packages/ramps-controller/src/RampsController.ts
+++ b/packages/ramps-controller/src/RampsController.ts
@@ -2618,13 +2618,13 @@ export class RampsController extends BaseController<
    * @param params.orderId - Full order ID (e.g. "/providers/paypal/orders/abc123") or order code.
    * @param params.providerCode - Canonical provider code (e.g. "paypal", "transak").
    * @param params.walletAddress - Wallet address for the order.
-   * @param params.chainId - Optional chain ID for the order.
+   * @param params.chainId - Chain ID for the order (decimal, hex, or CAIP-2). Must be non-empty.
    */
   addPrecreatedOrder(params: {
     orderId: string;
     providerCode: string;
     walletAddress: string;
-    chainId?: string;
+    chainId: string;
   }): void {
     const { orderId, providerCode, walletAddress, chainId } = params;
 
@@ -2632,6 +2632,9 @@ export class RampsController extends BaseController<
     if (!orderCode?.trim()) {
       return;
     }
+    if (!chainId.trim()) {
+      return;
+    }
     const stubOrder: RampsOrder = {
       providerOrderId: orderCode,
       provider: {
@@ -2654,7 +2657,7 @@ export class RampsController extends BaseController<
       providerOrderLink: '',
       totalFeesFiat: 0,
       txHash: '',
-      network: chainId ? { chainId, name: '' } : { chainId: '', name: '' },
+      network: { chainId, name: '' },
       canBeUpdated: true,
       idHasExpired: false,
       excludeFromPurchases: false,