diff --git a/apps/bff/src/integrations/freebit/services/freebit-auth.service.ts b/apps/bff/src/integrations/freebit/services/freebit-auth.service.ts
index 405a0172..64f35883 100644
--- a/apps/bff/src/integrations/freebit/services/freebit-auth.service.ts
+++ b/apps/bff/src/integrations/freebit/services/freebit-auth.service.ts
@@ -69,7 +69,7 @@ export class FreebitAuthService {
         throw new Error("Freebit API not configured: FREEBIT_OEM_KEY is missing");
       }
 
-      const request = FreebitProvider.schemas.auth.parse({
+      const request: FreebitAuthRequest = FreebitProvider.schemas.auth.parse({
         oemId: this.config.oemId,
         oemKey: this.config.oemKey,
       });
@@ -84,8 +84,9 @@ export class FreebitAuthService {
         throw new Error(`HTTP ${response.status}: ${response.statusText}`);
       }
 
-      const json = (await response.json()) as unknown;
-      const data = FreebitProvider.mapper.transformFreebitAuthResponse(json);
+      const json: unknown = await response.json();
+      const data: FreebitAuthResponse =
+        FreebitProvider.mapper.transformFreebitAuthResponse(json);
 
       if (data.resultCode !== "100" || !data.authKey) {
         throw new FreebitError(
diff --git a/apps/bff/src/integrations/whmcs/services/whmcs-currency.service.ts b/apps/bff/src/integrations/whmcs/services/whmcs-currency.service.ts
index 2fa728f7..36354534 100644
--- a/apps/bff/src/integrations/whmcs/services/whmcs-currency.service.ts
+++ b/apps/bff/src/integrations/whmcs/services/whmcs-currency.service.ts
@@ -165,10 +165,12 @@ export class WhmcsCurrencyService implements OnModuleInit {
       );
 
       // Extract currency indices
-      const currencyIndices = currencyKeys.map(key => {
-        const match = key.match(/currencies\[currency\]\[(\d+)\]\[id\]/);
-        return match ? parseInt(match[1]) : null;
-      }).filter(index => index !== null) as number[];
+      const currencyIndices = currencyKeys
+        .map(key => {
+          const match = key.match(/currencies\[currency\]\[(\d+)\]\[id\]/);
+          return match ? parseInt(match[1], 10) : null;
+        })
+        .filter((index): index is number => index !== null);
 
       // Build currency objects from the flat response
       for (const index of currencyIndices) {
diff --git a/apps/bff/src/integrations/whmcs/utils/whmcs-client.utils.ts b/apps/bff/src/integrations/whmcs/utils/whmcs-client.utils.ts
index 90a65b2f..eb9acefd 100644
--- a/apps/bff/src/integrations/whmcs/utils/whmcs-client.utils.ts
+++ b/apps/bff/src/integrations/whmcs/utils/whmcs-client.utils.ts
@@ -31,7 +31,10 @@ const toNumber = (value: unknown): number | null => {
 const toOptionalString = (value: unknown): string | undefined => {
   if (value === undefined || value === null) return undefined;
   if (typeof value === "string") return value;
-  return String(value);
+  if (typeof value === "number" || typeof value === "boolean") {
+    return String(value);
+  }
+  return undefined;
 };
 
 const toNullableBoolean = (value: unknown): boolean | null | undefined => {
diff --git a/apps/bff/src/modules/auth/infra/workflows/workflows/whmcs-link-workflow.service.ts b/apps/bff/src/modules/auth/infra/workflows/workflows/whmcs-link-workflow.service.ts
index 94ed376f..9549cc36 100644
--- a/apps/bff/src/modules/auth/infra/workflows/workflows/whmcs-link-workflow.service.ts
+++ b/apps/bff/src/modules/auth/infra/workflows/workflows/whmcs-link-workflow.service.ts
@@ -138,16 +138,14 @@ export class WhmcsLinkWorkflowService {
       const createdUser = await this.usersService.create({
         email,
         passwordHash: null,
-        firstName: String(clientDetails.firstname ?? ""),
-        lastName: String(clientDetails.lastname ?? ""),
-        company: String(clientDetails.companyname ?? ""), // Raw WHMCS field name
+        firstName: clientDetails.firstname ?? "",
+        lastName: clientDetails.lastname ?? "",
+        company: clientDetails.companyname ?? "", // Raw WHMCS field name
         phone:
-          String(
-            clientDetails.phonenumberformatted ??
-              clientDetails.phonenumber ??
-              clientDetails.telephoneNumber ??
-              ""
-          ), // Raw WHMCS field names
+          clientDetails.phonenumberformatted ??
+          clientDetails.phonenumber ??
+          clientDetails.telephoneNumber ??
+          "",
         emailVerified: true,
       });
 
diff --git a/apps/bff/src/modules/auth/presentation/http/auth.controller.ts b/apps/bff/src/modules/auth/presentation/http/auth.controller.ts
index 082749b7..41604d96 100644
--- a/apps/bff/src/modules/auth/presentation/http/auth.controller.ts
+++ b/apps/bff/src/modules/auth/presentation/http/auth.controller.ts
@@ -47,8 +47,9 @@ import {
   type AuthTokens,
 } from "@customer-portal/domain/auth";
 
-type RequestWithCookies = Request & {
-  cookies: Record<string, any>;
+type CookieValue = string | undefined;
+type RequestWithCookies = Omit<Request, "cookies"> & {
+  cookies?: Record<string, CookieValue>;
 };
 
 const resolveAuthorizationHeader = (req: RequestWithCookies): string | undefined => {
diff --git a/apps/bff/src/modules/auth/presentation/http/guards/global-auth.guard.ts b/apps/bff/src/modules/auth/presentation/http/guards/global-auth.guard.ts
index b4d4f36c..dba8bd1f 100644
--- a/apps/bff/src/modules/auth/presentation/http/guards/global-auth.guard.ts
+++ b/apps/bff/src/modules/auth/presentation/http/guards/global-auth.guard.ts
@@ -15,8 +15,9 @@ import { TokenBlacklistService } from "../../../infra/token/token-blacklist.serv
 import { IS_PUBLIC_KEY } from "../../../decorators/public.decorator";
 import { getErrorMessage } from "@bff/core/utils/error.util";
 
-type RequestWithCookies = Request & {
-  cookies: Record<string, any>;
+type CookieValue = string | undefined;
+type RequestWithCookies = Omit<Request, "cookies"> & {
+  cookies?: Record<string, CookieValue>;
 };
 type RequestWithRoute = RequestWithCookies & {
   method: string;
diff --git a/apps/bff/src/modules/orders/services/order-fulfillment-orchestrator.service.ts b/apps/bff/src/modules/orders/services/order-fulfillment-orchestrator.service.ts
index 6c12ca0e..f6272c19 100644
--- a/apps/bff/src/modules/orders/services/order-fulfillment-orchestrator.service.ts
+++ b/apps/bff/src/modules/orders/services/order-fulfillment-orchestrator.service.ts
@@ -22,14 +22,7 @@ import {
   Providers as OrderProviders,
 } from "@customer-portal/domain/orders";
 
-export interface OrderItemMappingResult {
-  whmcsItems: any[];
-  summary: {
-    totalItems: number;
-    serviceItems: number;
-    activationItems: number;
-  };
-}
+type WhmcsOrderItemMappingResult = ReturnType<typeof OrderProviders.Whmcs.mapOrderToWhmcsItems>;
 
 export interface OrderFulfillmentStep {
   step: string;
@@ -44,7 +37,7 @@ export interface OrderFulfillmentContext {
   idempotencyKey: string;
   validation: OrderFulfillmentValidationResult | null;
   orderDetails?: OrderDetails;
-  mappingResult?: OrderItemMappingResult;
+  mappingResult?: WhmcsOrderItemMappingResult;
   whmcsResult?: WhmcsOrderResult;
   steps: OrderFulfillmentStep[];
 }
@@ -134,7 +127,7 @@ export class OrderFulfillmentOrchestrator {
     }
 
     // Step 3: Execute the main fulfillment workflow as a distributed transaction
-    let mappingResult: OrderItemMappingResult | undefined;
+    let mappingResult: WhmcsOrderItemMappingResult | undefined;
     let whmcsCreateResult: { orderId: number } | undefined;
     let whmcsAcceptResult: WhmcsOrderResult | undefined;
 
diff --git a/apps/bff/src/modules/subscriptions/sim-management/services/sim-plan.service.ts b/apps/bff/src/modules/subscriptions/sim-management/services/sim-plan.service.ts
index ea45e71d..b9d9ad4f 100644
--- a/apps/bff/src/modules/subscriptions/sim-management/services/sim-plan.service.ts
+++ b/apps/bff/src/modules/subscriptions/sim-management/services/sim-plan.service.ts
@@ -60,9 +60,13 @@ export class SimPlanService {
         scheduleOrigin: request.scheduledAt ? "user-provided" : "auto-default",
       });
 
+      if (!scheduledAt) {
+        throw new BadRequestException("Failed to determine schedule date for plan change");
+      }
+
       const result = await this.freebitService.changeSimPlan(account, request.newPlanCode, {
         assignGlobalIp,
-        scheduledAt: scheduledAt!,
+        scheduledAt,
       });
 
       this.logger.log(`Successfully changed SIM plan for subscription ${subscriptionId}`, {
diff --git a/apps/bff/src/modules/users/users.service.ts b/apps/bff/src/modules/users/users.service.ts
index 214876d0..e54295f5 100644
--- a/apps/bff/src/modules/users/users.service.ts
+++ b/apps/bff/src/modules/users/users.service.ts
@@ -328,7 +328,10 @@ export class UsersService {
           const profile = await this.getProfile(userId);
           currency = profile.currency_code || currency;
         } catch (error) {
-          this.logger.warn("Could not fetch currency from profile", { userId });
+          this.logger.warn("Could not fetch currency from profile", {
+            userId,
+            error: getErrorMessage(error),
+          });
         }
         
         const summary: DashboardSummary = {
@@ -529,14 +532,15 @@ export class UsersService {
       let currency = "JPY"; // Default
       try {
         const client = await this.whmcsService.getClientDetails(mapping.whmcsClientId);
-        if (client && typeof client === 'object' && 'currency_code' in client) {
-          const currency_code = (client as any).currency_code;
-          if (currency_code) {
-            currency = currency_code;
-          }
+        const currencyCode = client.currency_code ?? client.raw.currency_code ?? null;
+        if (currencyCode) {
+          currency = currencyCode;
         }
       } catch (error) {
-        this.logger.warn("Could not fetch currency from WHMCS client", { userId });
+        this.logger.warn("Could not fetch currency from WHMCS client", {
+          userId,
+          error: getErrorMessage(error),
+        });
       }
 
       const summary: DashboardSummary = {
diff --git a/apps/bff/test/catalog-contract.spec.ts b/apps/bff/test/catalog-contract.spec.ts
index 3659971b..58ada1f0 100644
--- a/apps/bff/test/catalog-contract.spec.ts
+++ b/apps/bff/test/catalog-contract.spec.ts
@@ -1,10 +1,23 @@
 /// <reference types="jest" />
 import request from "supertest";
-import { INestApplication } from "@nestjs/common";
+import type { INestApplication } from "@nestjs/common";
 import { Test } from "@nestjs/testing";
+import type { Server } from "node:http";
 
 import { AppModule } from "../src/app.module";
-import { parseInternetCatalog } from "@customer-portal/domain/catalog";
+import {
+  parseInternetCatalog,
+  internetCatalogResponseSchema,
+} from "@customer-portal/domain/catalog";
+import { apiSuccessResponseSchema } from "@customer-portal/domain/common/schema";
+
+const internetCatalogApiResponseSchema = apiSuccessResponseSchema(internetCatalogResponseSchema);
+
+const isRecord = (value: unknown): value is Record<string, unknown> =>
+  typeof value === "object" && value !== null;
+
+const isHttpServer = (value: unknown): value is Server =>
+  isRecord(value) && typeof value.listen === "function" && typeof value.close === "function";
 
 describe("Catalog contract", () => {
   let app: INestApplication;
@@ -23,11 +36,15 @@ describe("Catalog contract", () => {
   });
 
   it("should return internet catalog matching domain schema", async () => {
-    const response = await request(app.getHttpServer()).get("/catalog/internet/plans");
+    const serverCandidate: unknown = app.getHttpServer();
+    if (!isHttpServer(serverCandidate)) {
+      throw new Error("Expected Nest application to expose an HTTP server");
+    }
+
+    const response = await request(serverCandidate).get("/catalog/internet/plans");
 
     expect(response.status).toBe(200);
-    expect(() => parseInternetCatalog(response.body.data)).not.toThrow();
+    const payload = internetCatalogApiResponseSchema.parse(response.body);
+    expect(() => parseInternetCatalog(payload.data)).not.toThrow();
   });
 });
-
-
diff --git a/apps/bff/tsconfig.json b/apps/bff/tsconfig.json
index f30f161f..5fa2f06b 100644
--- a/apps/bff/tsconfig.json
+++ b/apps/bff/tsconfig.json
@@ -27,6 +27,6 @@
       "module": "commonjs"
     }
   },
-  "include": ["src/**/*", "scripts/**/*"],
-  "exclude": ["node_modules", "dist", "**/*.spec.ts", "**/*.test.ts"]
+  "include": ["src/**/*", "scripts/**/*", "test/**/*"],
+  "exclude": ["node_modules", "dist"]
 }
diff --git a/apps/portal/src/features/billing/components/InvoiceTable/InvoiceTable.tsx b/apps/portal/src/features/billing/components/InvoiceTable/InvoiceTable.tsx
index eedf0bfb..ef1f1b9f 100644
--- a/apps/portal/src/features/billing/components/InvoiceTable/InvoiceTable.tsx
+++ b/apps/portal/src/features/billing/components/InvoiceTable/InvoiceTable.tsx
@@ -229,7 +229,9 @@ export function InvoiceTable({
                 <Button
                   size="sm"
                   variant="default"
-                  onClick={(e) => handlePayment(invoice, e)}
+                  onClick={event => {
+                    void handlePayment(invoice, event);
+                  }}
                   loading={isPaymentLoading}
                   className="text-xs font-medium shadow-sm"
                 >
@@ -241,7 +243,9 @@ export function InvoiceTable({
               <Button
                 size="sm"
                 variant="outline"
-                onClick={(e) => handleDownload(invoice, e)}
+                onClick={event => {
+                  void handleDownload(invoice, event);
+                }}
                 loading={isDownloadLoading}
                 leftIcon={!isDownloadLoading ? <ArrowDownTrayIcon className="h-4 w-4" /> : undefined}
                 className="text-xs font-medium border-gray-300 hover:border-gray-400 hover:bg-gray-50"
diff --git a/apps/portal/src/features/billing/hooks/usePaymentRefresh.ts b/apps/portal/src/features/billing/hooks/usePaymentRefresh.ts
index f1ee68c8..6b9bd52f 100644
--- a/apps/portal/src/features/billing/hooks/usePaymentRefresh.ts
+++ b/apps/portal/src/features/billing/hooks/usePaymentRefresh.ts
@@ -12,7 +12,7 @@ interface UsePaymentRefreshOptions {
   // When true, attaches focus/visibility listeners to refresh automatically
   attachFocusListeners?: boolean;
   // Optional custom detector for whether payment methods exist
-  hasMethods?: (data?: PaymentMethodList | undefined) => boolean;
+  hasMethods?: (data?: PaymentMethodList) => boolean;
 }
 
 export function usePaymentRefresh({
diff --git a/apps/portal/src/features/catalog/hooks/useConfigureParams.ts b/apps/portal/src/features/catalog/hooks/useConfigureParams.ts
index 0c664b0d..8c7fba93 100644
--- a/apps/portal/src/features/catalog/hooks/useConfigureParams.ts
+++ b/apps/portal/src/features/catalog/hooks/useConfigureParams.ts
@@ -1,85 +1,121 @@
 "use client";
 
 import { useSearchParams } from "next/navigation";
+import type { SimCardType, ActivationType, MnpData } from "@customer-portal/domain/sim";
 
 export type AccessMode = "IPoE-BYOR" | "PPPoE";
 
+const parseSimCardType = (value: string | null): SimCardType | null => {
+  if (value === "eSIM" || value === "Physical SIM") {
+    return value;
+  }
+  return null;
+};
+
+const parseActivationType = (value: string | null): ActivationType | null => {
+  if (value === "Immediate" || value === "Scheduled") {
+    return value;
+  }
+  return null;
+};
+
+const parsePortingGender = (
+  value: string | null
+): MnpData["portingGender"] | undefined => {
+  if (value === "Male" || value === "Female" || value === "Corporate/Other") {
+    return value;
+  }
+  return undefined;
+};
+
+const coalesce = <T>(...values: Array<T | null | undefined>): T | undefined => {
+  for (const candidate of values) {
+    if (candidate !== null && candidate !== undefined) {
+      return candidate;
+    }
+  }
+  return undefined;
+};
+
 export function useInternetConfigureParams() {
   const params = useSearchParams();
   const accessModeParam = params.get("accessMode");
-  const accessMode =
+  const accessMode: AccessMode | null =
     accessModeParam === "IPoE-BYOR" || accessModeParam === "PPPoE"
-      ? (accessModeParam as AccessMode)
+      ? accessModeParam
       : null;
   const installationSku = params.get("installationSku");
   const addonSkus = params.getAll("addonSku");
 
   return {
     accessMode,
-    installationSku: installationSku || null,
+    installationSku: installationSku ?? null,
     addonSkus,
   } as const;
 }
 
 export function useSimConfigureParams() {
   const params = useSearchParams();
-  const simTypeParam = params.get("simType");
-  const simType = simTypeParam === "eSIM" || simTypeParam === "Physical SIM" ? simTypeParam : null;
-  const eid = params.get("eid");
-  const activationTypeParam = params.get("activationType");
-  const activationType =
-    activationTypeParam === "Immediate" || activationTypeParam === "Scheduled"
-      ? activationTypeParam
-      : null;
-  const scheduledAt = params.get("scheduledAt") ?? params.get("scheduledDate");
-  const addonSkus = params.getAll("addonSku");
-  const isMnpParam = params.get("isMnp") ?? params.get("wantsMnp");
-  const isMnp = isMnpParam === "true";
 
-  // Optional detailed MNP fields if present
-  const mnp = {
-    reservationNumber:
-      params.get("mnpNumber") ??
-      params.get("reservationNumber") ??
-      params.get("mnp_reservationNumber") ??
-      undefined,
-    expiryDate:
-      params.get("mnpExpiry") ??
-      params.get("expiryDate") ??
-      params.get("mnp_expiryDate") ??
-      undefined,
-    phoneNumber:
-      params.get("mnpPhone") ??
-      params.get("phoneNumber") ??
-      params.get("mnp_phoneNumber") ??
-      undefined,
-    mvnoAccountNumber:
-      params.get("mvnoAccountNumber") ?? params.get("mnp_mvnoAccountNumber") ?? undefined,
-    portingLastName:
-      params.get("portingLastName") ?? params.get("mnp_portingLastName") ?? undefined,
-    portingFirstName:
-      params.get("portingFirstName") ?? params.get("mnp_portingFirstName") ?? undefined,
-    portingLastNameKatakana:
-      params.get("portingLastNameKatakana") ??
-      params.get("mnp_portingLastNameKatakana") ??
-      undefined,
-    portingFirstNameKatakana:
-      params.get("portingFirstNameKatakana") ??
-      params.get("mnp_portingFirstNameKatakana") ??
-      undefined,
-    portingGender:
-      (params.get("portingGender") as "Male" | "Female" | "Corporate/Other" | undefined) ??
-      (params.get("mnp_portingGender") as "Male" | "Female" | "Corporate/Other" | undefined) ??
-      undefined,
-    portingDateOfBirth:
-      params.get("portingDateOfBirth") ?? params.get("mnp_portingDateOfBirth") ?? undefined,
-  } as const;
+  const simType = parseSimCardType(params.get("simType"));
+  const activationType = parseActivationType(params.get("activationType"));
+  const scheduledAt =
+    coalesce(params.get("scheduledAt"), params.get("scheduledDate")) ?? null;
+  const addonSkus = params.getAll("addonSku");
+  const isMnp =
+    coalesce(params.get("isMnp"), params.get("wantsMnp"))?.toLowerCase() === "true";
+  const eid = params.get("eid") ?? null;
+
+  const mnp: Partial<MnpData> = {
+    reservationNumber: coalesce(
+      params.get("mnpNumber"),
+      params.get("reservationNumber"),
+      params.get("mnp_reservationNumber")
+    ),
+    expiryDate: coalesce(
+      params.get("mnpExpiry"),
+      params.get("expiryDate"),
+      params.get("mnp_expiryDate")
+    ),
+    phoneNumber: coalesce(
+      params.get("mnpPhone"),
+      params.get("phoneNumber"),
+      params.get("mnp_phoneNumber")
+    ),
+    mvnoAccountNumber: coalesce(
+      params.get("mvnoAccountNumber"),
+      params.get("mnp_mvnoAccountNumber")
+    ),
+    portingLastName: coalesce(
+      params.get("portingLastName"),
+      params.get("mnp_portingLastName")
+    ),
+    portingFirstName: coalesce(
+      params.get("portingFirstName"),
+      params.get("mnp_portingFirstName")
+    ),
+    portingLastNameKatakana: coalesce(
+      params.get("portingLastNameKatakana"),
+      params.get("mnp_portingLastNameKatakana")
+    ),
+    portingFirstNameKatakana: coalesce(
+      params.get("portingFirstNameKatakana"),
+      params.get("mnp_portingFirstNameKatakana")
+    ),
+    portingGender: parsePortingGender(
+      coalesce(params.get("portingGender"), params.get("mnp_portingGender")) ?? null
+    ),
+    portingDateOfBirth: coalesce(
+      params.get("portingDateOfBirth"),
+      params.get("mnp_portingDateOfBirth")
+    ),
+  };
 
   return {
     simType,
-    eid: eid || null,
+    eid,
     activationType,
-    scheduledAt: scheduledAt || null,
+    scheduledAt,
     addonSkus,
     isMnp,
     mnp,
diff --git a/apps/portal/src/features/catalog/hooks/useSimConfigure.ts b/apps/portal/src/features/catalog/hooks/useSimConfigure.ts
index 16205520..fca51102 100644
--- a/apps/portal/src/features/catalog/hooks/useSimConfigure.ts
+++ b/apps/portal/src/features/catalog/hooks/useSimConfigure.ts
@@ -1,6 +1,6 @@
 "use client";
 
-import { useEffect, useMemo, useState, useCallback } from "react";
+import { useEffect, useMemo, useState, useCallback, useRef } from "react";
 import { useSearchParams } from "next/navigation";
 import { useSimCatalog, useSimPlan, useSimConfigureParams } from ".";
 import { useZodForm } from "@customer-portal/validation";
@@ -59,6 +59,29 @@ export type UseSimConfigureResult = {
   buildCheckoutSearchParams: () => URLSearchParams;
 };
 
+const parseSimCardTypeParam = (value: string | null): SimCardType | null => {
+  if (value === "eSIM" || value === "Physical SIM") {
+    return value;
+  }
+  return null;
+};
+
+const parseActivationTypeParam = (value: string | null): ActivationType | null => {
+  if (value === "Immediate" || value === "Scheduled") {
+    return value;
+  }
+  return null;
+};
+
+const parsePortingGenderParam = (
+  value: string | null
+): MnpData["portingGender"] | undefined => {
+  if (value === "Male" || value === "Female" || value === "Corporate/Other") {
+    return value;
+  }
+  return undefined;
+};
+
 export function useSimConfigure(planId?: string): UseSimConfigureResult {
   const searchParams = useSearchParams();
   const { data: simData, isLoading: simLoading } = useSimCatalog();
@@ -96,6 +119,22 @@ export function useSimConfigure(planId?: string): UseSimConfigureResult {
     initialValues,
   });
 
+  const defaultMnpData: MnpData = useMemo(
+    () => ({
+      reservationNumber: "",
+      expiryDate: "",
+      phoneNumber: "",
+      mvnoAccountNumber: "",
+      portingLastName: "",
+      portingFirstName: "",
+      portingLastNameKatakana: "",
+      portingFirstNameKatakana: "",
+      portingGender: "",
+      portingDateOfBirth: "",
+    }),
+    []
+  );
+
   // Convenience setters that update the Zod form
   const setSimType = useCallback((value: SimCardType) => setValue("simType", value), [setValue]);
   const setEid = useCallback((value: string) => setValue("eid", value), [setValue]);
@@ -114,90 +153,176 @@ export function useSimConfigure(planId?: string): UseSimConfigureResult {
   const setWantsMnp = useCallback((value: boolean) => setValue("wantsMnp", value), [setValue]);
   const setMnpData = useCallback((value: MnpData) => setValue("mnpData", value), [setValue]);
 
+  const searchParamsString = useMemo(() => searchParams.toString(), [searchParams]);
+  const parsedSearchParams = useMemo(
+    () => new URLSearchParams(searchParamsString),
+    [searchParamsString]
+  );
+
+  const resolvedParams = useMemo(() => {
+    const initialSimType =
+      configureParams.simType ??
+      parseSimCardTypeParam(parsedSearchParams.get("simType")) ??
+      "eSIM";
+    const initialActivationType =
+      configureParams.activationType ??
+      parseActivationTypeParam(parsedSearchParams.get("activationType")) ??
+      "Immediate";
+
+    const addonSkuSet = new Set<string>();
+    configureParams.addonSkus.forEach(sku => addonSkuSet.add(sku));
+    const addonQuery = parsedSearchParams.get("addons");
+    if (addonQuery) {
+      addonQuery
+        .split(",")
+        .map(sku => sku.trim())
+        .filter(Boolean)
+        .forEach(sku => addonSkuSet.add(sku));
+    }
+
+    const scheduledAtRaw =
+      configureParams.scheduledAt ??
+      parsedSearchParams.get("scheduledAt") ??
+      parsedSearchParams.get("scheduledDate") ??
+      "";
+    const scheduledActivationDate = scheduledAtRaw
+      ? scheduledAtRaw.includes("-")
+        ? scheduledAtRaw
+        : `${scheduledAtRaw.slice(0, 4)}-${scheduledAtRaw.slice(4, 6)}-${scheduledAtRaw.slice(6, 8)}`
+      : "";
+
+    const wantsMnp =
+      configureParams.isMnp ||
+      parsedSearchParams.get("isMnp") === "true" ||
+      parsedSearchParams.get("wantsMnp") === "true";
+
+    const resolveField = (value?: string | null) => value ?? "";
+    const paramFallback = (primary?: string | null, secondary?: string | null) =>
+      resolveField(primary ?? secondary ?? undefined);
+
+    const mnp = configureParams.mnp;
+    const resolvedMnpData: MnpData = wantsMnp
+      ? {
+          reservationNumber: paramFallback(mnp.reservationNumber, parsedSearchParams.get("mnpNumber")),
+          expiryDate: paramFallback(mnp.expiryDate, parsedSearchParams.get("mnpExpiry")),
+          phoneNumber: paramFallback(mnp.phoneNumber, parsedSearchParams.get("mnpPhone")),
+          mvnoAccountNumber: paramFallback(
+            mnp.mvnoAccountNumber,
+            parsedSearchParams.get("mvnoAccountNumber")
+          ),
+          portingLastName: paramFallback(mnp.portingLastName, parsedSearchParams.get("portingLastName")),
+          portingFirstName: paramFallback(
+            mnp.portingFirstName,
+            parsedSearchParams.get("portingFirstName")
+          ),
+          portingLastNameKatakana: paramFallback(
+            mnp.portingLastNameKatakana,
+            parsedSearchParams.get("portingLastNameKatakana")
+          ),
+          portingFirstNameKatakana: paramFallback(
+            mnp.portingFirstNameKatakana,
+            parsedSearchParams.get("portingFirstNameKatakana")
+          ),
+          portingGender:
+            mnp.portingGender ??
+            parsePortingGenderParam(parsedSearchParams.get("portingGender")) ??
+            parsePortingGenderParam(parsedSearchParams.get("mnp_portingGender")) ??
+            "",
+          portingDateOfBirth: paramFallback(
+            mnp.portingDateOfBirth,
+            parsedSearchParams.get("portingDateOfBirth")
+          ),
+        }
+      : {
+          reservationNumber: "",
+          expiryDate: "",
+          phoneNumber: "",
+          mvnoAccountNumber: "",
+          portingLastName: "",
+          portingFirstName: "",
+          portingLastNameKatakana: "",
+          portingFirstNameKatakana: "",
+          portingGender: "",
+          portingDateOfBirth: "",
+        };
+
+    return {
+      simType: initialSimType,
+      eid: configureParams.eid ?? parsedSearchParams.get("eid") ?? "",
+      selectedAddons: Array.from(addonSkuSet),
+      activationType: initialActivationType,
+      scheduledActivationDate,
+      wantsMnp,
+      mnpData: resolvedMnpData,
+    };
+  }, [configureParams, parsedSearchParams]);
+
+  const appliedParamsSignatureRef = useRef<string | null>(null);
+
   // Initialize from URL params
   useEffect(() => {
-    let mounted = true;
-    const initializeFromParams = () => {
-      if (simLoading || !simData) return;
+    if (simLoading || !simData) return;
 
-      if (mounted) {
-        // Set initial values from URL params or defaults
-        const initialSimType =
-          (configureParams.simType as SimCardType | null) ??
-          (searchParams.get("simType") as SimCardType) ??
-          "eSIM";
-        const initialActivationType =
-          (configureParams.activationType as ActivationType | null) ??
-          (searchParams.get("activationType") as ActivationType) ??
-          "Immediate";
+    const signature = JSON.stringify(resolvedParams);
+    if (appliedParamsSignatureRef.current === signature) {
+      return;
+    }
 
-        setSimType(initialSimType);
-        setEid(configureParams.eid ?? searchParams.get("eid") ?? "");
-        const addonSkuSet = new Set<string>();
-        configureParams.addonSkus.forEach(sku => addonSkuSet.add(sku));
-        searchParams
-          .get("addons")
-          ?.split(",")
-          .filter(Boolean)
-          .forEach(sku => addonSkuSet.add(sku));
-        setSelectedAddons(Array.from(addonSkuSet));
-        setActivationType(initialActivationType);
-        const scheduledAt =
-          configureParams.scheduledAt ??
-          searchParams.get("scheduledAt") ??
-          searchParams.get("scheduledDate") ??
-          "";
-        if (scheduledAt) {
-          setScheduledActivationDate(
-            scheduledAt.includes("-")
-              ? scheduledAt
-              : `${scheduledAt.slice(0, 4)}-${scheduledAt.slice(4, 6)}-${scheduledAt.slice(6, 8)}`
-          );
-        }
-
-        const wantsMnp = configureParams.isMnp;
-        setWantsMnp(wantsMnp);
-
-        if (wantsMnp) {
-          const mnp = configureParams.mnp;
-          setMnpData({
-            reservationNumber: mnp.reservationNumber ?? "",
-            expiryDate: mnp.expiryDate ?? "",
-            phoneNumber: mnp.phoneNumber ?? "",
-            mvnoAccountNumber: mnp.mvnoAccountNumber ?? "",
-            portingLastName: mnp.portingLastName ?? "",
-            portingFirstName: mnp.portingFirstName ?? "",
-            portingLastNameKatakana: mnp.portingLastNameKatakana ?? "",
-            portingFirstNameKatakana: mnp.portingFirstNameKatakana ?? "",
-            portingGender: mnp.portingGender ?? "",
-            portingDateOfBirth: mnp.portingDateOfBirth ?? "",
-          });
-        } else {
-          setMnpData({
-            reservationNumber: "",
-            expiryDate: "",
-            phoneNumber: "",
-            mvnoAccountNumber: "",
-            portingLastName: "",
-            portingFirstName: "",
-            portingLastNameKatakana: "",
-            portingFirstNameKatakana: "",
-            portingGender: "",
-            portingDateOfBirth: "",
-          });
-        }
-      }
+    const arrayEquals = (a: string[], b: string[]) => {
+      if (a.length !== b.length) return false;
+      const setA = new Set(a);
+      return b.every(item => setA.has(item));
     };
 
-    initializeFromParams();
-    return () => {
-      mounted = false;
+    const mnpEquals = (a: MnpData | undefined, b: MnpData) => {
+      const left = a ?? defaultMnpData;
+      return (
+        left.reservationNumber === b.reservationNumber &&
+        left.expiryDate === b.expiryDate &&
+        left.phoneNumber === b.phoneNumber &&
+        left.mvnoAccountNumber === b.mvnoAccountNumber &&
+        left.portingLastName === b.portingLastName &&
+        left.portingFirstName === b.portingFirstName &&
+        left.portingLastNameKatakana === b.portingLastNameKatakana &&
+        left.portingFirstNameKatakana === b.portingFirstNameKatakana &&
+        left.portingGender === b.portingGender &&
+        left.portingDateOfBirth === b.portingDateOfBirth
+      );
     };
+
+    if (values.simType !== resolvedParams.simType) {
+      setSimType(resolvedParams.simType);
+    }
+
+    if (values.eid !== resolvedParams.eid) {
+      setEid(resolvedParams.eid);
+    }
+
+    if (!arrayEquals(values.selectedAddons, resolvedParams.selectedAddons)) {
+      setSelectedAddons(resolvedParams.selectedAddons);
+    }
+
+    if (values.activationType !== resolvedParams.activationType) {
+      setActivationType(resolvedParams.activationType);
+    }
+
+    if (values.scheduledActivationDate !== resolvedParams.scheduledActivationDate) {
+      setScheduledActivationDate(resolvedParams.scheduledActivationDate);
+    }
+
+    if (values.wantsMnp !== resolvedParams.wantsMnp) {
+      setWantsMnp(resolvedParams.wantsMnp);
+    }
+
+    if (!mnpEquals(values.mnpData, resolvedParams.mnpData)) {
+      setMnpData(resolvedParams.mnpData);
+    }
+
+    appliedParamsSignatureRef.current = signature;
   }, [
     simLoading,
     simData,
-    searchParams,
-    configureParams,
+    resolvedParams,
     setSimType,
     setEid,
     setSelectedAddons,
@@ -205,6 +330,14 @@ export function useSimConfigure(planId?: string): UseSimConfigureResult {
     setScheduledActivationDate,
     setWantsMnp,
     setMnpData,
+    values.simType,
+    values.eid,
+    values.selectedAddons,
+    values.activationType,
+    values.scheduledActivationDate,
+    values.wantsMnp,
+    values.mnpData,
+    defaultMnpData,
   ]);
 
   // Step transition handler (memoized)
@@ -363,18 +496,7 @@ export function useSimConfigure(planId?: string): UseSimConfigureResult {
     setScheduledActivationDate,
     wantsMnp: values.wantsMnp,
     setWantsMnp,
-    mnpData: values.mnpData || {
-      reservationNumber: "",
-      expiryDate: "",
-      phoneNumber: "",
-      mvnoAccountNumber: "",
-      portingLastName: "",
-      portingFirstName: "",
-      portingLastNameKatakana: "",
-      portingFirstNameKatakana: "",
-      portingGender: "" as const,
-      portingDateOfBirth: "",
-    },
+    mnpData: values.mnpData || defaultMnpData,
     setMnpData,
 
     // Step orchestration
diff --git a/apps/portal/src/lib/api/response-helpers.ts b/apps/portal/src/lib/api/response-helpers.ts
index 3d9edaf6..e0b1e5a2 100644
--- a/apps/portal/src/lib/api/response-helpers.ts
+++ b/apps/portal/src/lib/api/response-helpers.ts
@@ -4,6 +4,7 @@ import {
   type ApiErrorResponse,
   type ApiSuccessResponse,
 } from "@customer-portal/domain/common";
+import type { ZodTypeAny, infer as ZodInfer } from "zod";
 
 /**
  * API Response Helper Types and Functions
@@ -86,7 +87,12 @@ export function parseDomainError(payload: unknown): ApiErrorResponse | null {
   return parsed.success ? parsed.data : null;
 }
 
-export function buildSuccessResponse<T>(data: T, schema: (value: T) => T): ApiSuccessResponse<T> {
-  return apiSuccessResponseSchema({ parse: () => schema(data) } as any).parse({ success: true, data });
+export function buildSuccessResponse<T extends ZodTypeAny>(
+  data: ZodInfer<T>,
+  schema: T
+): ApiSuccessResponse<ZodInfer<T>> {
+  return apiSuccessResponseSchema(schema).parse({
+    success: true,
+    data,
+  });
 }
-
diff --git a/apps/portal/src/lib/hooks/useCurrency.ts b/apps/portal/src/lib/hooks/useCurrency.ts
index 048da5d5..19ca3c5a 100644
--- a/apps/portal/src/lib/hooks/useCurrency.ts
+++ b/apps/portal/src/lib/hooks/useCurrency.ts
@@ -30,7 +30,7 @@ export function useCurrency() {
       }
     };
 
-    loadCurrency();
+    void loadCurrency();
   }, []);
 
   return {