diff --git a/src/services/resource-publisher.ts b/src/services/resource-publisher.ts
index 1c4c17a..efd39fe 100644
--- a/src/services/resource-publisher.ts
+++ b/src/services/resource-publisher.ts
@@ -429,6 +429,7 @@ export async function publishResource(
         descriptor.workspace,
         config.envMapping
       );
+      json = normalizeSubscriptionOwnerId(json);
     }
 
     // ApiRelease: normalize properties.apiId from source ARM path to target ARM path.
@@ -1158,6 +1159,37 @@ function normalizeSubscriptionScope(
   return json;
 }
 
+/**
+ * Normalise the `properties.ownerId` field of a Subscription resource.
+ *
+ * APIM returns ownerId as a full ARM resource path on GET, e.g.:
+ *   /subscriptions/{sub}/resourceGroups/{rg}/providers/Microsoft.ApiManagement/service/{svc}/users/1
+ *
+ * The PUT endpoint requires a relative URL in the format `/users/{userId}`,
+ * so a subscription extracted from one instance would otherwise carry the
+ * source instance's service path. Strip the service ARM prefix like
+ * normalizeSubscriptionScope does for scope. Unlike scope, envMapping
+ * affixes must NOT be applied — a user id is not an affixed resource name.
+ * Already-relative values are left untouched.
+ */
+function normalizeSubscriptionOwnerId(
+  json: Record<string, unknown>
+): Record<string, unknown> {
+  const props = json.properties as Record<string, unknown> | undefined;
+  const ownerId = props?.ownerId;
+  if (typeof ownerId !== 'string') return json;
+
+  const serviceOwnerMatch = ownerId.match(
+    /^\/subscriptions\/[^/]+\/resourceGroups\/[^/]+\/providers\/Microsoft\.ApiManagement\/service\/[^/]+(\/users\/[^/]+)$/i
+  );
+  if (!serviceOwnerMatch?.[1]) return json;
+
+  return {
+    ...json,
+    properties: { ...props, ownerId: serviceOwnerMatch[1] },
+  };
+}
+
 export function applyApiPathPrefix(
   json: Record<string, unknown>,
   descriptor: ResourceDescriptor,
diff --git a/tests/unit/services/resource-publisher.test.ts b/tests/unit/services/resource-publisher.test.ts
index c64597b..6add006 100644
--- a/tests/unit/services/resource-publisher.test.ts
+++ b/tests/unit/services/resource-publisher.test.ts
@@ -1385,6 +1385,105 @@ describe('resource-publisher', () => {
       expect(client.putResource).toHaveBeenCalledTimes(1);
     });
 
+    it('should normalize ownerId from source service ARM path to relative /users path', async () => {
+      const client = createMockClient();
+      const store = createMockStore();
+
+      // ownerId carries the SOURCE service coordinates after extract
+      const sourceArmPrefix =
+        '/subscriptions/src-sub/resourceGroups/src-rg/providers/Microsoft.ApiManagement/service/src-apim';
+      const targetArmPrefix =
+        '/subscriptions/sub-1/resourceGroups/rg-1/providers/Microsoft.ApiManagement/service/apim-1';
+
+      store.readResource.mockResolvedValue({
+        name: 'team-a-product-sub',
+        properties: {
+          ownerId: `${sourceArmPrefix}/users/1`,
+          scope: `${targetArmPrefix}/products/starter`,
+          displayName: 'Team A starter product',
+          state: 'active',
+        },
+      });
+
+      const descriptor: ResourceDescriptor = {
+        type: ResourceType.Subscription,
+        nameParts: ['team-a-product-sub'],
+      };
+
+      await publishResource(client, store, testContext, descriptor, testConfig);
+
+      const putJson = client.putResource.mock.calls[0][2] as Record<string, unknown>;
+      const props = putJson.properties as Record<string, unknown>;
+      expect(props.ownerId).toBe('/users/1');
+    });
+
+    it('should leave already-relative ownerId untouched', async () => {
+      const client = createMockClient();
+      const store = createMockStore();
+
+      const armScopePrefix =
+        '/subscriptions/sub-1/resourceGroups/rg-1/providers/Microsoft.ApiManagement/service/apim-1';
+
+      store.readResource.mockResolvedValue({
+        name: 'team-a-product-sub',
+        properties: {
+          ownerId: '/users/42',
+          scope: `${armScopePrefix}/products/starter`,
+          displayName: 'Team A starter product',
+          state: 'active',
+        },
+      });
+
+      const descriptor: ResourceDescriptor = {
+        type: ResourceType.Subscription,
+        nameParts: ['team-a-product-sub'],
+      };
+
+      await publishResource(client, store, testContext, descriptor, testConfig);
+
+      const putJson = client.putResource.mock.calls[0][2] as Record<string, unknown>;
+      const props = putJson.properties as Record<string, unknown>;
+      expect(props.ownerId).toBe('/users/42');
+    });
+
+    it('should not apply envMapping affixes to normalized ownerId', async () => {
+      const client = createMockClient();
+      const store = createMockStore();
+
+      const sourceArmPrefix =
+        '/subscriptions/src-sub/resourceGroups/src-rg/providers/Microsoft.ApiManagement/service/src-apim';
+
+      store.readResource.mockResolvedValue({
+        name: 'team-a-product-sub',
+        properties: {
+          ownerId: `${sourceArmPrefix}/users/1`,
+          scope: `${sourceArmPrefix}/products/starter`,
+          displayName: 'Team A starter product',
+          state: 'active',
+        },
+      });
+
+      const descriptor: ResourceDescriptor = {
+        type: ResourceType.Subscription,
+        nameParts: ['team-a-product-sub'],
+      };
+      const config: PublishConfig = {
+        ...testConfig,
+        envMapping: buildEnvMapping({
+          namePrefix: 'dev-',
+          appliesTo: [ResourceType.Product],
+        }),
+      };
+
+      await publishResource(client, store, testContext, descriptor, config);
+
+      const putJson = client.putResource.mock.calls[0][2] as Record<string, unknown>;
+      const props = putJson.properties as Record<string, unknown>;
+      // scope gets the affixed product name, ownerId must not be affixed
+      expect(props.scope).toBe('/products/dev-starter');
+      expect(props.ownerId).toBe('/users/1');
+    });
+
     describe('ApiOperation text normalization', () => {
       it('sets displayName and description to empty string when omitted', async () => {
         const client = createMockClient();