diff --git a/apps/bff/src/core/http/exception.filter.ts b/apps/bff/src/core/http/exception.filter.ts
index a226314e..ad94b934 100644
--- a/apps/bff/src/core/http/exception.filter.ts
+++ b/apps/bff/src/core/http/exception.filter.ts
@@ -10,6 +10,7 @@ import type { ExceptionFilter, ArgumentsHost } from "@nestjs/common";
 import type { Request, Response } from "express";
 import { Logger } from "nestjs-pino";
 import { ConfigService } from "@nestjs/config";
+import { ZodValidationException } from "nestjs-zod";
 import {
   ErrorCode,
   ErrorMessages,
@@ -79,16 +80,22 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
     const errorContext = this.buildErrorContext(request);
 
     // Extract status code and error details
-    const { status, errorCode, originalMessage } = this.extractErrorDetails(exception);
+    const { status, errorCode, originalMessage, fieldErrors } = this.extractErrorDetails(exception);
 
     // Get user-friendly message (with dev details if in development)
-    const userMessage = this.getUserMessage(errorCode, originalMessage);
+    const userMessage = this.getUserMessage(errorCode, originalMessage, fieldErrors);
 
     // Log the error
     this.logError(errorCode, originalMessage, status, errorContext, exception);
 
     // Build and send response
-    const errorResponse = this.buildErrorResponse(errorCode, userMessage, status, errorContext);
+    const errorResponse = this.buildErrorResponse(
+      errorCode,
+      userMessage,
+      status,
+      errorContext,
+      fieldErrors
+    );
     response.status(status).json(errorResponse);
   }
 
@@ -99,12 +106,22 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
     status: number;
     errorCode: ErrorCodeType;
     originalMessage: string;
+    fieldErrors?: Record<string, string> | undefined;
   } {
     let status = HttpStatus.INTERNAL_SERVER_ERROR;
     let originalMessage = "An unexpected error occurred";
     let explicitCode: ErrorCodeType | undefined;
+    let fieldErrors: Record<string, string> | undefined;
 
-    if (exception instanceof HttpException) {
+    // ZodValidationException must be checked before HttpException
+    // since ZodValidationException extends BadRequestException extends HttpException
+    if (exception instanceof ZodValidationException) {
+      status = exception.getStatus();
+      const extracted = this.extractZodFieldErrors(exception);
+      fieldErrors = extracted.fieldErrors;
+      originalMessage = extracted.message;
+      explicitCode = ErrorCode.VALIDATION_FAILED;
+    } else if (exception instanceof HttpException) {
       status = exception.getStatus();
       const extracted = this.extractExceptionDetails(exception);
       originalMessage = extracted.message;
@@ -120,7 +137,49 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
     // Map to error code
     const errorCode = explicitCode ?? mapHttpStatusToErrorCode(status);
 
-    return { status, errorCode, originalMessage };
+    return { status, errorCode, originalMessage, fieldErrors };
+  }
+
+  /**
+   * Extract field errors and a summary message from a ZodValidationException.
+   */
+  private extractZodFieldErrors(exception: ZodValidationException): {
+    fieldErrors?: Record<string, string>;
+    message: string;
+  } {
+    const zodError = exception.getZodError();
+    const issues = this.extractZodIssues(zodError);
+
+    if (issues.length === 0) {
+      return { message: "Validation failed" };
+    }
+
+    const fieldErrors: Record<string, string> = {};
+    for (const issue of issues) {
+      const fieldKey = issue.path.length > 0 ? issue.path.join(".") : "_form";
+      if (!(fieldKey in fieldErrors)) {
+        fieldErrors[fieldKey] = issue.message;
+      }
+    }
+
+    return { fieldErrors, message: issues[0]!.message };
+  }
+
+  /**
+   * Extract Zod issues from the unknown ZodError returned by getZodError()
+   */
+  private extractZodIssues(
+    zodError: unknown
+  ): Array<{ path: (string | number)[]; message: string }> {
+    if (
+      zodError &&
+      typeof zodError === "object" &&
+      "issues" in zodError &&
+      Array.isArray((zodError as { issues: unknown }).issues)
+    ) {
+      return (zodError as { issues: Array<{ path: (string | number)[]; message: string }> }).issues;
+    }
+    return [];
   }
 
   /**
@@ -193,9 +252,21 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
   }
 
   /**
-   * Get user-friendly message, with dev details in development mode
+   * Get user-friendly message, with dev details in development mode.
+   * When fieldErrors is present (Zod validation), use the original Zod message
+   * instead of the generic canned message, since Zod messages are developer-authored
+   * and safe to display to users.
    */
-  private getUserMessage(errorCode: ErrorCodeType, originalMessage: string): string {
+  private getUserMessage(
+    errorCode: ErrorCodeType,
+    originalMessage: string,
+    fieldErrors?: Record<string, string>
+  ): string {
+    // For Zod validation errors, use the original message (developer-authored, safe to display)
+    if (fieldErrors) {
+      return originalMessage;
+    }
+
     const userMessage = ErrorMessages[errorCode] ?? ErrorMessages[ErrorCode.UNKNOWN];
 
     if (this.isDevelopment && originalMessage !== userMessage) {
@@ -228,18 +299,19 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
     request: Request & { user?: { id?: string }; requestId?: string }
   ): ErrorContext {
     const userAgentHeader = request.headers["user-agent"];
+    const userAgent =
+      typeof userAgentHeader === "string"
+        ? userAgentHeader
+        : Array.isArray(userAgentHeader)
+          ? userAgentHeader[0]
+          : undefined;
 
     return {
       requestId: request.requestId ?? this.generateRequestId(),
       userId: request.user?.id,
       method: request.method,
       path: request.url,
-      userAgent:
-        typeof userAgentHeader === "string"
-          ? userAgentHeader
-          : Array.isArray(userAgentHeader)
-            ? userAgentHeader[0]
-            : undefined,
+      userAgent,
       ip: request.ip,
     };
   }
@@ -302,7 +374,8 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
     errorCode: ErrorCodeType,
     message: string,
     status: number,
-    context: ErrorContext
+    context: ErrorContext,
+    fieldErrors?: Record<string, string>
   ): ApiError {
     const metadata = ErrorMetadata[errorCode] ?? ErrorMetadata[ErrorCode.UNKNOWN];
 
@@ -317,6 +390,7 @@ export class UnifiedExceptionFilter implements ExceptionFilter {
           timestamp: new Date().toISOString(),
           path: context.path,
           requestId: context.requestId,
+          ...(fieldErrors && { fieldErrors }),
         },
       },
     };
diff --git a/apps/bff/src/infra/queue/services/whmcs-request-queue.service.ts b/apps/bff/src/infra/queue/services/whmcs-request-queue.service.ts
index 2cf954e6..1a9f4302 100644
--- a/apps/bff/src/infra/queue/services/whmcs-request-queue.service.ts
+++ b/apps/bff/src/infra/queue/services/whmcs-request-queue.service.ts
@@ -193,7 +193,7 @@ export class WhmcsRequestQueueService implements OnModuleInit, OnModuleDestroy {
             this.metrics.failedRequests++;
             this.metrics.lastErrorTime = new Date();
 
-            this.logger.error(
+            this.logger.warn(
               {
                 requestId,
                 waitTime,
diff --git a/apps/bff/src/integrations/japanpost/facades/japanpost.facade.ts b/apps/bff/src/integrations/japanpost/facades/japanpost.facade.ts
index b9dfd272..32053887 100644
--- a/apps/bff/src/integrations/japanpost/facades/japanpost.facade.ts
+++ b/apps/bff/src/integrations/japanpost/facades/japanpost.facade.ts
@@ -3,15 +3,27 @@
  *
  * Public API for Japan Post integration.
  * Controllers should use this facade instead of internal services directly.
+ *
+ * Adds Redis-backed caching for postal code lookups — address data is
+ * stable and rarely changes, so a 24-hour TTL avoids redundant API calls.
  */
 
-import { Injectable } from "@nestjs/common";
+import { Inject, Injectable } from "@nestjs/common";
+import { Logger } from "nestjs-pino";
 import { JapanPostAddressService } from "../services/japanpost-address.service.js";
+import { CacheService } from "@bff/infra/cache/cache.service.js";
 import type { AddressLookupResult } from "@customer-portal/domain/address";
 
+const CACHE_PREFIX = "japanpost:zip:";
+const CACHE_TTL_SECONDS = 86_400; // 24 hours
+
 @Injectable()
 export class JapanPostFacade {
-  constructor(private readonly addressService: JapanPostAddressService) {}
+  constructor(
+    private readonly addressService: JapanPostAddressService,
+    private readonly cache: CacheService,
+    @Inject(Logger) private readonly logger: Logger
+  ) {}
 
   /**
    * Lookup address by ZIP code
@@ -24,7 +36,30 @@ export class JapanPostFacade {
     zipCode: string,
     clientIp: string = "127.0.0.1"
   ): Promise<AddressLookupResult> {
-    return this.addressService.lookupByZipCode(zipCode, clientIp);
+    const normalizedZip = zipCode.replace(/-/g, "");
+    const cacheKey = `${CACHE_PREFIX}${normalizedZip}`;
+
+    try {
+      const cached = await this.cache.get<AddressLookupResult>(cacheKey);
+      if (cached) {
+        return cached;
+      }
+    } catch {
+      // Redis unavailable — proceed without cache
+    }
+
+    const result = await this.addressService.lookupByZipCode(zipCode, clientIp);
+
+    // Cache successful lookups with results
+    if (result.count > 0) {
+      try {
+        await this.cache.set(cacheKey, result, CACHE_TTL_SECONDS);
+      } catch {
+        this.logger.debug({ zipCode: normalizedZip }, "Failed to cache Japan Post lookup result");
+      }
+    }
+
+    return result;
   }
 
   /**
diff --git a/apps/bff/src/integrations/whmcs/connection/services/whmcs-http-client.service.ts b/apps/bff/src/integrations/whmcs/connection/services/whmcs-http-client.service.ts
index 6e3f836c..53051feb 100644
--- a/apps/bff/src/integrations/whmcs/connection/services/whmcs-http-client.service.ts
+++ b/apps/bff/src/integrations/whmcs/connection/services/whmcs-http-client.service.ts
@@ -49,7 +49,7 @@ export class WhmcsHttpClientService {
       this.stats.failedRequests++;
       this.stats.lastErrorTime = new Date();
 
-      this.logger.error(`WHMCS HTTP request failed [${action}]`, {
+      this.logger.warn(`WHMCS HTTP request failed [${action}]`, {
         error: extractErrorMessage(error),
         action,
         params: redactForLogs(params),
diff --git a/apps/bff/src/integrations/whmcs/services/whmcs-client.service.ts b/apps/bff/src/integrations/whmcs/services/whmcs-client.service.ts
index 19ce52b1..17fe0aca 100644
--- a/apps/bff/src/integrations/whmcs/services/whmcs-client.service.ts
+++ b/apps/bff/src/integrations/whmcs/services/whmcs-client.service.ts
@@ -18,6 +18,9 @@ import { addressSchema, type Address, type WhmcsClient } from "@customer-portal/
 
 @Injectable()
 export class WhmcsClientService {
+  /** In-flight getClientDetails calls — deduplicates concurrent requests for the same client */
+  private readonly inflightDetails = new Map<number, Promise<WhmcsClient>>();
+
   constructor(
     private readonly connectionService: WhmcsConnectionFacade,
     private readonly cacheService: WhmcsCacheService,
@@ -54,18 +57,35 @@ export class WhmcsClientService {
   }
 
   /**
-   * Get client details by ID
-   * Returns WhmcsClient (type inferred from domain mapper)
+   * Get client details by ID.
+   * Concurrent calls for the same clientId share a single API request.
    */
   async getClientDetails(clientId: number): Promise<WhmcsClient> {
-    try {
-      // Try cache first
-      const cached = await this.cacheService.getClientData(clientId);
-      if (cached) {
-        this.logger.debug(`Cache hit for client: ${clientId}`);
-        return cached;
-      }
+    // Try cache first (fast path, no dedup needed)
+    const cached = await this.cacheService.getClientData(clientId);
+    if (cached) {
+      this.logger.debug(`Cache hit for client: ${clientId}`);
+      return cached;
+    }
 
+    // Deduplicate: reuse in-flight request for the same clientId
+    const inflight = this.inflightDetails.get(clientId);
+    if (inflight) {
+      return inflight;
+    }
+
+    const promise = this.fetchClientDetails(clientId);
+    this.inflightDetails.set(clientId, promise);
+
+    try {
+      return await promise;
+    } finally {
+      this.inflightDetails.delete(clientId);
+    }
+  }
+
+  private async fetchClientDetails(clientId: number): Promise<WhmcsClient> {
+    try {
       const response = await this.connectionService.getClientDetails(clientId);
 
       if (!response || !response.client) {
diff --git a/apps/bff/src/integrations/whmcs/services/whmcs-invoice.service.ts b/apps/bff/src/integrations/whmcs/services/whmcs-invoice.service.ts
index b4c0eeae..85288fbd 100644
--- a/apps/bff/src/integrations/whmcs/services/whmcs-invoice.service.ts
+++ b/apps/bff/src/integrations/whmcs/services/whmcs-invoice.service.ts
@@ -233,7 +233,7 @@ export class WhmcsInvoiceService {
     limit: number
   ): InvoiceList {
     if (!response.invoices?.invoice) {
-      this.logger.warn(`No invoices found for client ${clientId}`);
+      this.logger.debug(`No invoices found for client ${clientId}`);
       return {
         invoices: [],
         pagination: {
diff --git a/apps/bff/src/modules/address/address-writer.service.ts b/apps/bff/src/modules/address/address-writer.service.ts
index b816bd92..e06c9fd0 100644
--- a/apps/bff/src/modules/address/address-writer.service.ts
+++ b/apps/bff/src/modules/address/address-writer.service.ts
@@ -33,6 +33,12 @@ export interface ResolveWhmcsAddressParams {
 
 @Injectable()
 export class AddressWriterService {
+  /** In-flight Japan Post lookups keyed by postcode — deduplicates concurrent calls */
+  private readonly inflightLookups = new Map<
+    string,
+    Promise<Awaited<ReturnType<JapanPostFacade["lookupByZipCode"]>>>
+  >();
+
   constructor(
     private readonly japanPost: JapanPostFacade,
     private readonly salesforceFacade: SalesforceFacade,
@@ -63,16 +69,13 @@ export class AddressWriterService {
    * Resolve English address from postal code via Japan Post API
    * and prepare WHMCS address fields.
    *
-   * Flow:
-   * 1. Call Japan Post API with postal code
-   * 2. Match result using townJa (if multiple matches)
-   * 3. Build BilingualAddress with resolved English fields
-   * 4. Return WhmcsAddressFields via prepareWhmcsAddressFields()
+   * Uses in-flight deduplication so concurrent lookups for the same
+   * postcode share a single API call.
    */
   async resolveWhmcsAddress(params: ResolveWhmcsAddressParams): Promise<WhmcsAddressFields> {
     const { postcode, townJa, streetAddress, buildingName, roomNumber, residenceType } = params;
 
-    const lookupResult = await this.japanPost.lookupByZipCode(postcode);
+    const lookupResult = await this.lookupPostalCode(postcode);
 
     if (lookupResult.addresses.length === 0) {
       this.logger.warn({ postcode }, "Japan Post API returned no results for postal code");
@@ -113,17 +116,73 @@ export class AddressWriterService {
   }
 
   /**
-   * Convenience: resolve WHMCS address from a full BilingualAddress.
-   * Re-derives English fields from postal code via Japan Post API.
+   * Deduplicated Japan Post lookup — concurrent calls for the same postcode
+   * share one API request.
    */
-  async resolveWhmcsAddressFromBilingual(address: BilingualAddress): Promise<WhmcsAddressFields> {
-    return this.resolveWhmcsAddress({
+  private async lookupPostalCode(
+    postcode: string
+  ): Promise<Awaited<ReturnType<JapanPostFacade["lookupByZipCode"]>>> {
+    const inflight = this.inflightLookups.get(postcode);
+    if (inflight) {
+      return inflight;
+    }
+
+    const promise = this.japanPost.lookupByZipCode(postcode);
+    this.inflightLookups.set(postcode, promise);
+
+    try {
+      return await promise;
+    } finally {
+      this.inflightLookups.delete(postcode);
+    }
+  }
+
+  /**
+   * Prepare WHMCS address fields from a full BilingualAddress.
+   * Uses the already-populated English fields — no API call needed.
+   */
+  resolveWhmcsAddressFromBilingual(address: BilingualAddress): WhmcsAddressFields {
+    return prepareWhmcsAddressFields(address);
+  }
+
+  /**
+   * Convert WhmcsAddressFields to the shape expected by CreateWhmcsClientStep.
+   */
+  toWhmcsStepAddress(fields: WhmcsAddressFields): {
+    address1: string;
+    address2?: string;
+    city: string;
+    state: string;
+    postcode: string;
+    country: string;
+  } {
+    return {
+      address1: fields.address1 || "",
+      ...(fields.address2 && { address2: fields.address2 }),
+      city: fields.city,
+      state: fields.state,
+      postcode: fields.postcode,
+      country: fields.country,
+    };
+  }
+
+  /**
+   * Build case address from bilingual address.
+   * Maps Japanese fields to the eligibility case step's expected format.
+   */
+  toCaseAddress(address: BilingualAddress): {
+    address1: string;
+    city: string;
+    state: string;
+    postcode: string;
+    country: string;
+  } {
+    return {
+      address1: `${address.townJa}${address.streetAddress}`,
+      city: address.cityJa,
+      state: address.prefectureJa,
       postcode: address.postcode,
-      townJa: address.townJa,
-      streetAddress: address.streetAddress,
-      buildingName: address.buildingName,
-      roomNumber: address.roomNumber,
-      residenceType: address.residenceType,
-    });
+      country: "Japan",
+    };
   }
 }
diff --git a/apps/bff/src/modules/auth/infra/workflows/guest-eligibility-workflow.service.ts b/apps/bff/src/modules/auth/infra/workflows/guest-eligibility-workflow.service.ts
index c53e9996..8918d30b 100644
--- a/apps/bff/src/modules/auth/infra/workflows/guest-eligibility-workflow.service.ts
+++ b/apps/bff/src/modules/auth/infra/workflows/guest-eligibility-workflow.service.ts
@@ -10,6 +10,7 @@ import { DistributedLockService } from "@bff/infra/cache/distributed-lock.servic
 import { SalesforceAccountService } from "@bff/integrations/salesforce/services/salesforce-account.service.js";
 import { SalesforceFacade } from "@bff/integrations/salesforce/facades/salesforce.facade.js";
 import { extractErrorMessage } from "@bff/core/utils/error.util.js";
+import { safeOperation, OperationCriticality } from "@bff/core/utils/safe-operation.util.js";
 import {
   PORTAL_SOURCE_INTERNET_ELIGIBILITY,
   PORTAL_STATUS_NOT_YET,
@@ -101,27 +102,20 @@ export class GuestEligibilityWorkflowService {
             );
           }
 
-          // Write Japanese address to Salesforce
-          try {
-            await this.addressWriter.writeToSalesforce(sfAccountId, address);
-          } catch (addressError) {
-            this.logger.warn(
-              { error: extractErrorMessage(addressError), email: normalizedEmail },
-              "SF address write failed (non-critical, continuing)"
-            );
-          }
-
-          // Create eligibility case via shared step
-          const { caseId } = await this.eligibilityCaseStep.execute({
-            sfAccountId,
-            address: {
-              address1: `${address.townJa}${address.streetAddress}`,
-              city: address.cityJa,
-              state: address.prefectureJa,
-              postcode: address.postcode,
-              country: "Japan",
-            },
-          });
+          // SF address write (DEGRADABLE) + eligibility case creation — independent, run in parallel
+          const [, { caseId }] = await Promise.all([
+            safeOperation(async () => this.addressWriter.writeToSalesforce(sfAccountId, address), {
+              criticality: OperationCriticality.OPTIONAL,
+              fallback: undefined,
+              context: "SF address write",
+              logger: this.logger,
+              metadata: { email: normalizedEmail },
+            }),
+            this.eligibilityCaseStep.execute({
+              sfAccountId,
+              address: this.addressWriter.toCaseAddress(address),
+            }),
+          ]);
 
           // If user wants to continue to account creation, generate a handoff token
           let handoffToken: string | undefined;
diff --git a/apps/bff/src/modules/auth/infra/workflows/new-customer-signup-workflow.service.ts b/apps/bff/src/modules/auth/infra/workflows/new-customer-signup-workflow.service.ts
index 2454e232..b9d443fc 100644
--- a/apps/bff/src/modules/auth/infra/workflows/new-customer-signup-workflow.service.ts
+++ b/apps/bff/src/modules/auth/infra/workflows/new-customer-signup-workflow.service.ts
@@ -8,8 +8,8 @@ import { type SignupWithEligibilityRequest } from "@customer-portal/domain/get-s
 import { DistributedLockService } from "@bff/infra/cache/distributed-lock.service.js";
 import { EmailService } from "@bff/infra/email/email.service.js";
 import { UsersService } from "@bff/modules/users/application/users.service.js";
-import { WhmcsAccountDiscoveryService } from "@bff/integrations/whmcs/services/whmcs-account-discovery.service.js";
 import { extractErrorMessage } from "@bff/core/utils/error.util.js";
+import { safeOperation, OperationCriticality } from "@bff/core/utils/safe-operation.util.js";
 import { PORTAL_SOURCE_INTERNET_ELIGIBILITY } from "@bff/modules/auth/constants/portal.constants.js";
 import type { AuthResultInternal } from "@bff/modules/auth/auth.types.js";
 import { AddressWriterService } from "@bff/modules/address/address-writer.service.js";
@@ -39,7 +39,6 @@ export class NewCustomerSignupWorkflowService {
     private readonly sessionService: GetStartedSessionService,
     private readonly lockService: DistributedLockService,
     private readonly usersService: UsersService,
-    private readonly whmcsDiscovery: WhmcsAccountDiscoveryService,
     private readonly emailService: EmailService,
     private readonly sfStep: ResolveSalesforceAccountStep,
     private readonly caseStep: CreateEligibilityCaseStep,
@@ -148,39 +147,38 @@ export class NewCustomerSignupWorkflowService {
       updateSourceIfExists: true,
     });
 
-    // Step 1.5: Write Japanese address to Salesforce (DEGRADABLE)
-    try {
-      await this.addressWriter.writeToSalesforce(sfResult.sfAccountId, address);
-    } catch (addressError) {
-      this.logger.warn(
-        { error: extractErrorMessage(addressError), email },
-        "SF address write failed (non-critical, continuing)"
-      );
-    }
-
-    // Step 2: Create eligibility case (DEGRADABLE)
-    let eligibilityRequestId: string | undefined;
-    try {
-      const caseResult = await this.caseStep.execute({
-        sfAccountId: sfResult.sfAccountId,
-        address: {
-          address1: `${address.townJa}${address.streetAddress}`,
-          city: address.cityJa,
-          state: address.prefectureJa,
-          postcode: address.postcode,
-          country: "Japan",
+    // Steps 1.5 + 2: SF address write + eligibility case creation (both DEGRADABLE, independent)
+    const [, eligibilityRequestId] = await Promise.all([
+      safeOperation(
+        async () => this.addressWriter.writeToSalesforce(sfResult.sfAccountId, address),
+        {
+          criticality: OperationCriticality.OPTIONAL,
+          fallback: undefined,
+          context: "SF address write",
+          logger: this.logger,
+          metadata: { email },
+        }
+      ),
+      safeOperation(
+        async () => {
+          const caseResult = await this.caseStep.execute({
+            sfAccountId: sfResult.sfAccountId,
+            address: this.addressWriter.toCaseAddress(address),
+          });
+          return caseResult.caseId;
         },
-      });
-      eligibilityRequestId = caseResult.caseId;
-    } catch (caseError) {
-      this.logger.warn(
-        { error: extractErrorMessage(caseError), email },
-        "Eligibility case creation failed (non-critical, continuing)"
-      );
-    }
+        {
+          criticality: OperationCriticality.OPTIONAL,
+          fallback: undefined as string | undefined,
+          context: "Eligibility case creation",
+          logger: this.logger,
+          metadata: { email },
+        }
+      ),
+    ]);
 
     // Step 3: Create WHMCS client (CRITICAL, has rollback)
-    const whmcsAddress = await this.addressWriter.resolveWhmcsAddressFromBilingual(address);
+    const whmcsAddress = this.addressWriter.resolveWhmcsAddressFromBilingual(address);
 
     const whmcsResult = await this.whmcsStep.execute({
       email,
@@ -188,14 +186,7 @@ export class NewCustomerSignupWorkflowService {
       firstName,
       lastName,
       phone: phone ?? "",
-      address: {
-        address1: whmcsAddress.address1 || "",
-        ...(whmcsAddress.address2 && { address2: whmcsAddress.address2 }),
-        city: whmcsAddress.city,
-        state: whmcsAddress.state,
-        postcode: whmcsAddress.postcode,
-        country: whmcsAddress.country,
-      },
+      address: this.addressWriter.toWhmcsStepAddress(whmcsAddress),
       customerNumber: sfResult.customerNumber ?? null,
       dateOfBirth,
       gender,
@@ -217,17 +208,20 @@ export class NewCustomerSignupWorkflowService {
     }
 
     // Step 5: Update SF flags (DEGRADABLE)
-    try {
-      await this.sfFlagsStep.execute({
-        sfAccountId: sfResult.sfAccountId,
-        whmcsClientId: whmcsResult.whmcsClientId,
-      });
-    } catch (flagsError) {
-      this.logger.warn(
-        { error: extractErrorMessage(flagsError), email },
-        "SF flags update failed (non-critical, continuing)"
-      );
-    }
+    await safeOperation(
+      async () =>
+        this.sfFlagsStep.execute({
+          sfAccountId: sfResult.sfAccountId,
+          whmcsClientId: whmcsResult.whmcsClientId,
+        }),
+      {
+        criticality: OperationCriticality.OPTIONAL,
+        fallback: undefined,
+        context: "SF flags update",
+        logger: this.logger,
+        metadata: { email },
+      }
+    );
 
     // Step 6: Generate auth result + finalize
     const authResult = await this.authResultStep.execute({
@@ -255,10 +249,9 @@ export class NewCustomerSignupWorkflowService {
   private async checkExistingAccounts(
     email: string
   ): Promise<{ success: false; message: string } | null> {
-    const [portalUser, whmcsClient] = await Promise.all([
-      this.usersService.findByEmailInternal(email),
-      this.whmcsDiscovery.findClientByEmail(email),
-    ]);
+    // Only check Portal — the verification phase already checked WHMCS,
+    // and the AddClient step will reject duplicates if one was created in the interim.
+    const portalUser = await this.usersService.findByEmailInternal(email);
 
     if (portalUser) {
       return {
@@ -267,14 +260,6 @@ export class NewCustomerSignupWorkflowService {
       };
     }
 
-    if (whmcsClient) {
-      return {
-        success: false,
-        message:
-          "A billing account already exists with this email. Please use account linking instead.",
-      };
-    }
-
     return null;
   }
 
diff --git a/apps/bff/src/modules/auth/infra/workflows/sf-completion-workflow.service.ts b/apps/bff/src/modules/auth/infra/workflows/sf-completion-workflow.service.ts
index 5cdfcd62..2ac71d27 100644
--- a/apps/bff/src/modules/auth/infra/workflows/sf-completion-workflow.service.ts
+++ b/apps/bff/src/modules/auth/infra/workflows/sf-completion-workflow.service.ts
@@ -6,8 +6,8 @@ import { type CompleteAccountRequest } from "@customer-portal/domain/get-started
 
 import { DistributedLockService } from "@bff/infra/cache/distributed-lock.service.js";
 import { UsersService } from "@bff/modules/users/application/users.service.js";
-import { WhmcsAccountDiscoveryService } from "@bff/integrations/whmcs/services/whmcs-account-discovery.service.js";
 import { extractErrorMessage } from "@bff/core/utils/error.util.js";
+import { safeOperation, OperationCriticality } from "@bff/core/utils/safe-operation.util.js";
 import { PORTAL_SOURCE_NEW_SIGNUP } from "@bff/modules/auth/constants/portal.constants.js";
 import type { AuthResultInternal } from "@bff/modules/auth/auth.types.js";
 import { AddressWriterService } from "@bff/modules/address/address-writer.service.js";
@@ -35,7 +35,6 @@ export class SfCompletionWorkflowService {
     private readonly sessionService: GetStartedSessionService,
     private readonly lockService: DistributedLockService,
     private readonly usersService: UsersService,
-    private readonly whmcsDiscovery: WhmcsAccountDiscoveryService,
     private readonly sfStep: ResolveSalesforceAccountStep,
     private readonly whmcsStep: CreateWhmcsClientStep,
     private readonly portalUserStep: CreatePortalUserStep,
@@ -135,30 +134,33 @@ export class SfCompletionWorkflowService {
       source: PORTAL_SOURCE_NEW_SIGNUP,
     });
 
-    // Step 1.5: Write Japanese address to Salesforce for new customers (DEGRADABLE)
-    if (isNewCustomer && address.prefectureJa) {
-      try {
-        await this.addressWriter.writeToSalesforce(
-          sfResult.sfAccountId,
-          address as BilingualAddress
-        );
-      } catch (addressError) {
-        this.logger.warn(
-          { error: extractErrorMessage(addressError), email: session.email },
-          "SF address write failed (non-critical, continuing)"
-        );
-      }
-    }
-
-    // Step 2: Create WHMCS client (CRITICAL, has rollback)
-    const whmcsAddress = await this.addressWriter.resolveWhmcsAddress({
-      postcode: address.postcode,
-      townJa: address.townJa,
-      streetAddress: address.streetAddress || "",
-      buildingName: address.buildingName,
-      roomNumber: address.roomNumber,
-      residenceType: address.residenceType || "house",
-    });
+    // Steps 1.5 + 2: SF address write (DEGRADABLE) + WHMCS address resolve (CRITICAL) — independent
+    const [, whmcsAddress] = await Promise.all([
+      isNewCustomer && address.prefectureJa
+        ? safeOperation(
+            async () =>
+              this.addressWriter.writeToSalesforce(
+                sfResult.sfAccountId,
+                address as BilingualAddress
+              ),
+            {
+              criticality: OperationCriticality.OPTIONAL,
+              fallback: undefined,
+              context: "SF address write",
+              logger: this.logger,
+              metadata: { email: session.email },
+            }
+          )
+        : Promise.resolve(),
+      this.addressWriter.resolveWhmcsAddress({
+        postcode: address.postcode,
+        townJa: address.townJa,
+        streetAddress: address.streetAddress || "",
+        buildingName: address.buildingName,
+        roomNumber: address.roomNumber,
+        residenceType: address.residenceType || "house",
+      }),
+    ]);
 
     const whmcsResult = await this.whmcsStep.execute({
       firstName: finalFirstName,
@@ -166,14 +168,7 @@ export class SfCompletionWorkflowService {
       email: session.email,
       password,
       phone: phone ?? "",
-      address: {
-        address1: whmcsAddress.address1 || "",
-        ...(whmcsAddress.address2 && { address2: whmcsAddress.address2 }),
-        city: whmcsAddress.city,
-        state: whmcsAddress.state,
-        postcode: whmcsAddress.postcode,
-        country: whmcsAddress.country,
-      },
+      address: this.addressWriter.toWhmcsStepAddress(whmcsAddress),
       customerNumber: sfResult.customerNumber ?? null,
       dateOfBirth,
       gender,
@@ -195,17 +190,20 @@ export class SfCompletionWorkflowService {
     }
 
     // Step 4: Update SF flags (DEGRADABLE)
-    try {
-      await this.sfFlagsStep.execute({
-        sfAccountId: sfResult.sfAccountId,
-        whmcsClientId: whmcsResult.whmcsClientId,
-      });
-    } catch (flagsError) {
-      this.logger.warn(
-        { error: extractErrorMessage(flagsError), email: session.email },
-        "SF flags update failed (non-critical, continuing)"
-      );
-    }
+    await safeOperation(
+      async () =>
+        this.sfFlagsStep.execute({
+          sfAccountId: sfResult.sfAccountId,
+          whmcsClientId: whmcsResult.whmcsClientId,
+        }),
+      {
+        criticality: OperationCriticality.OPTIONAL,
+        fallback: undefined,
+        context: "SF flags update",
+        logger: this.logger,
+        metadata: { email: session.email },
+      }
+    );
 
     // Step 5: Generate auth result
     const authResult = await this.authResultStep.execute({
@@ -226,16 +224,10 @@ export class SfCompletionWorkflowService {
   }
 
   private async ensureNoExistingAccounts(email: string): Promise<void> {
-    const [portalUser, whmcsClient] = await Promise.all([
-      this.usersService.findByEmailInternal(email),
-      this.whmcsDiscovery.findClientByEmail(email),
-    ]);
+    // Only check Portal — the verification phase already checked WHMCS,
+    // and the AddClient step will reject duplicates if one was created in the interim.
+    const portalUser = await this.usersService.findByEmailInternal(email);
 
-    if (whmcsClient) {
-      throw new ConflictException(
-        "A billing account already exists. Please use the account migration flow."
-      );
-    }
     if (portalUser) {
       throw new ConflictException("An account already exists. Please log in.");
     }
diff --git a/apps/portal/src/features/auth/components/LoginForm/LoginForm.tsx b/apps/portal/src/features/auth/components/LoginForm/LoginForm.tsx
index cbfc38b4..1fa44d95 100644
--- a/apps/portal/src/features/auth/components/LoginForm/LoginForm.tsx
+++ b/apps/portal/src/features/auth/components/LoginForm/LoginForm.tsx
@@ -19,6 +19,7 @@ import { LoginOtpStep } from "../LoginOtpStep";
 import { useLoginWithOtp } from "../../hooks/use-auth";
 import { loginRequestSchema } from "@customer-portal/domain/auth";
 import { useZodForm } from "@/shared/hooks";
+import { parseError } from "@/shared/utils";
 import { z } from "zod";
 import { getSafeRedirect } from "@/features/auth/utils/route-protection";
 
@@ -94,8 +95,7 @@ export function LoginForm({
           onSuccess?.();
         }
       } catch (err) {
-        const message = err instanceof Error ? err.message : "Login failed";
-        onError?.(message);
+        onError?.(parseError(err).message);
         throw err;
       }
     },
@@ -112,8 +112,7 @@ export function LoginForm({
         await verifyOtp(otpState.sessionToken, code, rememberDevice);
         onSuccess?.();
       } catch (err) {
-        const message = err instanceof Error ? err.message : "Verification failed";
-        onError?.(message);
+        onError?.(parseError(err).message);
         throw err;
       }
     },
diff --git a/apps/portal/src/features/auth/components/PasswordResetForm/PasswordResetForm.tsx b/apps/portal/src/features/auth/components/PasswordResetForm/PasswordResetForm.tsx
index 41c3c9f4..49a5b064 100644
--- a/apps/portal/src/features/auth/components/PasswordResetForm/PasswordResetForm.tsx
+++ b/apps/portal/src/features/auth/components/PasswordResetForm/PasswordResetForm.tsx
@@ -13,6 +13,7 @@ import { PasswordRequirements, PasswordMatchIndicator } from "..";
 import { usePasswordReset } from "../../hooks/use-auth";
 import { usePasswordValidation } from "../../hooks/usePasswordValidation";
 import { useZodForm } from "@/shared/hooks";
+import { parseError } from "@/shared/utils";
 import { passwordResetRequestSchema, passwordResetSchema } from "@customer-portal/domain/auth";
 import { z } from "zod";
 
@@ -66,8 +67,7 @@ export function PasswordResetForm({
         await requestPasswordReset(data.email);
         onSuccess?.();
       } catch (err) {
-        const errorMessage = err instanceof Error ? err.message : "Request failed";
-        onError?.(errorMessage);
+        onError?.(parseError(err).message);
         throw err;
       }
     },
@@ -82,8 +82,7 @@ export function PasswordResetForm({
         await resetPassword(data.token, data.password);
         onSuccess?.();
       } catch (err) {
-        const errorMessage = err instanceof Error ? err.message : "Reset failed";
-        onError?.(errorMessage);
+        onError?.(parseError(err).message);
         throw err;
       }
     },
diff --git a/apps/portal/src/features/auth/components/SetPasswordForm/SetPasswordForm.tsx b/apps/portal/src/features/auth/components/SetPasswordForm/SetPasswordForm.tsx
index 513c935a..b894ecff 100644
--- a/apps/portal/src/features/auth/components/SetPasswordForm/SetPasswordForm.tsx
+++ b/apps/portal/src/features/auth/components/SetPasswordForm/SetPasswordForm.tsx
@@ -12,6 +12,7 @@ import { PasswordRequirements, PasswordMatchIndicator } from "..";
 import { useAuth } from "../../hooks/use-auth";
 import { usePasswordValidation } from "../../hooks/usePasswordValidation";
 import { useZodForm } from "@/shared/hooks";
+import { parseError } from "@/shared/utils";
 import { setPasswordRequestSchema, getPasswordStrengthDisplay } from "@customer-portal/domain/auth";
 import { z } from "zod";
 
@@ -47,7 +48,7 @@ export function SetPasswordForm({
         await setPassword(data.email, data.password);
         onSuccess?.();
       } catch (err) {
-        onError?.(err instanceof Error ? err.message : "Failed to set password");
+        onError?.(parseError(err).message);
         throw err;
       }
     },
diff --git a/apps/portal/src/features/auth/stores/auth.store.ts b/apps/portal/src/features/auth/stores/auth.store.ts
index faf10ed0..7473fb02 100644
--- a/apps/portal/src/features/auth/stores/auth.store.ts
+++ b/apps/portal/src/features/auth/stores/auth.store.ts
@@ -302,10 +302,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
         }
         applyAuthResponse(parsed.data);
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Signup failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
@@ -340,10 +338,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
         });
         set({ loading: false });
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Password reset request failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
@@ -364,10 +360,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
           error: null,
         });
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Password reset failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
@@ -384,10 +378,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
         }
         applyAuthResponse(parsed.data);
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Password change failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
@@ -408,10 +400,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
         set({ loading: false });
         return parsed.data;
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Check failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
@@ -429,10 +419,8 @@ export const useAuthStore = create<AuthState>()((set, get) => {
         }
         applyAuthResponse(parsed.data);
       } catch (error) {
-        set({
-          loading: false,
-          error: error instanceof Error ? error.message : "Set password failed",
-        });
+        const parsed = parseError(error);
+        set({ loading: false, error: parsed.message });
         throw error;
       }
     },
diff --git a/apps/portal/src/shared/hooks/useZodForm.ts b/apps/portal/src/shared/hooks/useZodForm.ts
index ed6004b1..898d98df 100644
--- a/apps/portal/src/shared/hooks/useZodForm.ts
+++ b/apps/portal/src/shared/hooks/useZodForm.ts
@@ -6,6 +6,7 @@
 import { useCallback, useMemo, useRef, useState } from "react";
 import type { FormEvent } from "react";
 import { ZodError, type ZodIssue, type ZodType } from "zod";
+import { parseError } from "@/shared/utils/error-handling";
 
 export type FormErrors<_TValues extends Record<string, unknown>> = Record<
   string,
@@ -212,9 +213,23 @@ export function useZodForm<TValues extends Record<string, unknown>>({
       try {
         await onSubmit(values);
       } catch (error) {
-        const message = error instanceof Error ? error.message : String(error);
+        const parsed = parseError(error);
+        const message = parsed.message;
         setSubmitError(message);
-        setErrors(prev => ({ ...prev, ["_form"]: message }));
+
+        if (parsed.fieldErrors && Object.keys(parsed.fieldErrors).length > 0) {
+          // Merge server field errors into form errors and mark those fields as touched
+          setErrors(prev => ({ ...prev, ...parsed.fieldErrors, ["_form"]: message }));
+          setTouchedState(prev => {
+            const next = { ...prev };
+            for (const key of Object.keys(parsed.fieldErrors!)) {
+              next[key] = true;
+            }
+            return next;
+          });
+        } else {
+          setErrors(prev => ({ ...prev, ["_form"]: message }));
+        }
       } finally {
         setIsSubmitting(false);
       }
diff --git a/apps/portal/src/shared/utils/error-handling.ts b/apps/portal/src/shared/utils/error-handling.ts
index 4ccf17b4..c1e370d5 100644
--- a/apps/portal/src/shared/utils/error-handling.ts
+++ b/apps/portal/src/shared/utils/error-handling.ts
@@ -23,6 +23,7 @@ export interface ParsedError {
   message: string;
   shouldLogout: boolean;
   shouldRetry: boolean;
+  fieldErrors?: Record<string, string> | undefined;
 }
 
 // ============================================================================
@@ -78,11 +79,13 @@ function parseApiError(error: ClientApiError): ParsedError {
       : ErrorCode.UNKNOWN;
 
     const metadata = ErrorMetadata[resolvedCode] ?? ErrorMetadata[ErrorCode.UNKNOWN];
+    const fieldErrors = extractFieldErrors(domainError.error.details);
     return {
       code: resolvedCode,
       message: domainError.error.message,
       shouldLogout: metadata.shouldLogout,
       shouldRetry: metadata.shouldRetry,
+      ...(fieldErrors && { fieldErrors }),
     };
   }
 
@@ -97,6 +100,26 @@ function parseApiError(error: ClientApiError): ParsedError {
   };
 }
 
+/**
+ * Extract fieldErrors from error details if present and valid.
+ * Validates that the value is a Record<string, string> at runtime.
+ */
+function extractFieldErrors(details: unknown): Record<string, string> | undefined {
+  if (!details || typeof details !== "object" || Array.isArray(details)) return undefined;
+
+  const raw = (details as Record<string, unknown>)["fieldErrors"];
+  if (!raw || typeof raw !== "object" || Array.isArray(raw)) return undefined;
+
+  const result: Record<string, string> = {};
+  for (const [key, value] of Object.entries(raw as Record<string, unknown>)) {
+    if (typeof value === "string") {
+      result[key] = value;
+    }
+  }
+
+  return Object.keys(result).length > 0 ? result : undefined;
+}
+
 /**
  * Parse native JavaScript errors (network, timeout, etc.)
  */
diff --git a/docs/plans/2026-03-03-signup-flow-simplification-design.md b/docs/plans/2026-03-03-signup-flow-simplification-design.md
new file mode 100644
index 00000000..6b7c7050
--- /dev/null
+++ b/docs/plans/2026-03-03-signup-flow-simplification-design.md
@@ -0,0 +1,242 @@
+# Auth Flow Simplification Design
+
+**Date**: 2026-03-03
+**Status**: Approved
+
+## Problem
+
+The auth system has accumulated duplication and dead code:
+
+1. **Duplicate signup workflows**: `SfCompletionWorkflow` and `NewCustomerSignupWorkflow` are 85% identical (~300 lines each). The only difference is eligibility case creation and a welcome email.
+2. **Confusing names**: `SfCompletionWorkflow` doesn't describe what it does (it creates full accounts, not just "completes SF").
+3. **Missing SF fields**: `Birthdate` and `Sex__c` are not set on Salesforce PersonContact during account creation. The only code that called `createContact()` lived in dead legacy code.
+4. **Dead code**: `signup/` directory (6 files), `WhmcsLinkWorkflowService` — all unreferenced or superseded.
+5. **Legacy duplicate**: `WhmcsLinkWorkflowService` (password-based migration via `POST /auth/migrate`) is superseded by `WhmcsMigrationWorkflowService` (OTP-based migration via get-started).
+6. **Scattered shared services**: `SignupUserCreationService` and `SignupWhmcsService` live in `signup/` but are used by other workflows via `CreatePortalUserStep`. They should live alongside the steps they serve.
+
+## Approach — 3 Phases (can stop after any phase)
+
+### Phase 1: Merge signup workflows + cleanup
+
+Merge the two near-duplicate workflows. Move shared services. Delete dead code. Fix Birthdate/Sex\_\_c.
+
+### Phase 2: Remove legacy migrate endpoint
+
+Delete `WhmcsLinkWorkflowService` and `POST /auth/migrate`. All WHMCS migration goes through the get-started OTP-based flow.
+
+### Phase 3: Clean up OTP infrastructure
+
+Extract shared OTP email-sending pattern. Login and signup OTP stay as separate workflows (they serve different purposes: 2FA vs email verification). Keep separate sessions (different data models, TTLs, lifecycle). Improve the PORTAL_EXISTS redirect UX (prefill email on login page).
+
+**Why login and signup stay separate**: In the ISP/telecom industry, login (password → OTP as 2FA) and signup (OTP as email verification → form) serve fundamentally different security purposes. Forcing them into one flow either adds friction for existing users or weakens the security model. Major ISP portals keep these flows separate.
+
+---
+
+## Current Structure
+
+```
+workflows/
+├── verification-workflow.service.ts          # OTP + account status detection
+├── guest-eligibility-workflow.service.ts     # Guest ISP check (no account created)
+├── sf-completion-workflow.service.ts         # Creates account (misleading name, 85% overlap)
+├── new-customer-signup-workflow.service.ts   # Creates account + eligibility (85% overlap)
+├── whmcs-migration-workflow.service.ts       # OTP-based WHMCS migration (active)
+├── whmcs-link-workflow.service.ts            # Password-based WHMCS migration (legacy, superseded)
+├── login-otp-workflow.service.ts             # Login OTP 2FA
+├── password-workflow.service.ts              # Password operations
+├── get-started-coordinator.service.ts        # Get-started routing
+├── workflow-error.util.ts                    # Error classification
+├── signup/                                   # Mixed: some active, some dead
+│   ├── signup-account-resolver.service.ts    # Dead (no active caller)
+│   ├── signup-validation.service.ts          # Dead (no active caller)
+│   ├── signup-whmcs.service.ts               # Active (markClientForCleanup used by CreatePortalUserStep)
+│   ├── signup-user-creation.service.ts       # Active (used by CreatePortalUserStep + WhmcsMigration)
+│   ├── signup.types.ts                       # Dead (only used by dead validation service)
+│   └── index.ts                              # Barrel
+└── steps/                                    # Shared step services
+    ├── resolve-salesforce-account.step.ts
+    ├── create-whmcs-client.step.ts
+    ├── create-portal-user.step.ts            # Delegates to SignupUserCreationService
+    ├── create-eligibility-case.step.ts
+    ├── update-salesforce-flags.step.ts
+    ├── generate-auth-result.step.ts
+    └── index.ts
+```
+
+## New Structure (after all 3 phases)
+
+```
+workflows/
+├── verification-workflow.service.ts            # OTP + account detection (unchanged)
+├── guest-eligibility-workflow.service.ts        # Guest ISP check (unchanged)
+├── account-creation-workflow.service.ts         # MERGED: replaces sf-completion + new-customer-signup
+├── account-migration-workflow.service.ts        # RENAMED: from whmcs-migration
+├── login-otp-workflow.service.ts                # Login OTP 2FA (Phase 3: uses shared OTP orchestration)
+├── password-workflow.service.ts                 # Unchanged
+├── get-started-coordinator.service.ts           # Updated imports
+├── workflow-error.util.ts                       # Unchanged
+└── steps/                                       # Shared steps + moved services
+    ├── resolve-salesforce-account.step.ts
+    ├── create-whmcs-client.step.ts
+    ├── create-portal-user.step.ts
+    ├── create-eligibility-case.step.ts
+    ├── update-salesforce-flags.step.ts
+    ├── generate-auth-result.step.ts
+    ├── portal-user-creation.service.ts          # MOVED from signup/ (renamed)
+    ├── whmcs-cleanup.service.ts                 # MOVED from signup/ (renamed, trimmed)
+    └── index.ts
+```
+
+**Deleted (all phases combined):**
+
+- `sf-completion-workflow.service.ts` (merged, Phase 1)
+- `new-customer-signup-workflow.service.ts` (merged, Phase 1)
+- `whmcs-migration-workflow.service.ts` (renamed, Phase 1)
+- `whmcs-link-workflow.service.ts` (removed, Phase 2)
+- `signup/` entire directory (Phase 1)
+
+---
+
+## Phase 1: Merge signup workflows + cleanup
+
+### Merged Workflow: AccountCreationWorkflowService
+
+**API:**
+
+```typescript
+class AccountCreationWorkflowService {
+  execute(
+    request: CompleteAccountRequest | SignupWithEligibilityRequest,
+    options?: { withEligibility?: boolean }
+  ): Promise<AuthResultInternal | SignupWithEligibilityResult>;
+}
+```
+
+**Routing:**
+
+- `POST /auth/get-started/complete-account` → `execute(request)` (no eligibility)
+- `POST /auth/get-started/signup-with-eligibility` → `execute(request, { withEligibility: true })`
+
+**Step Sequence:**
+
+```
+1. Validate + check existing accounts
+2. Hash password
+3. Resolve address + names (from request or session prefill)
+4. Step 1: Resolve SF Account (CRITICAL)
+5. Step 1.5: Write SF Address (DEGRADABLE)
+6. Step 1.6: Create SF Contact — Birthdate + Sex__c (DEGRADABLE)  ← NEW, fixes the bug
+7. [if withEligibility] Step 2: Create Eligibility Case (DEGRADABLE)
+8. Step 3: Create WHMCS Client (CRITICAL, rollback)
+9. Step 4: Create Portal User (CRITICAL, rollback WHMCS on fail)
+10. Step 5: Update SF Flags (DEGRADABLE)
+11. Step 6: Generate Auth Result
+12. [if withEligibility] Send welcome email with eligibility ref (DEGRADABLE)
+13. Invalidate session
+```
+
+**Error handling difference between paths:**
+
+- `completeAccount` path: throws exceptions directly (current sf-completion behavior)
+- `signupWithEligibility` path: wraps in try/catch, returns `{ success: false, message, errorCategory }` using `classifyError()`
+
+**Birthdate/Sex\_\_c Fix:**
+After resolving the SF account, call `SalesforceAccountService.createContact()` on the PersonContact:
+
+- `Birthdate` → `dateOfBirth` (YYYY-MM-DD)
+- `Sex__c` → mapped from `gender` (`male`→`男性`, `female`→`女性`, `other`→`Other`)
+  This is degradable — account creation continues if it fails.
+
+### Rename: AccountMigrationWorkflowService
+
+Rename `WhmcsMigrationWorkflowService` → `AccountMigrationWorkflowService`. Refactor to use `CreatePortalUserStep` instead of calling `SignupUserCreationService` directly (reuse existing step, same as other workflows).
+
+### Move signup/ services into steps/
+
+| Old                                      | New                                     | Changes                                                             |
+| ---------------------------------------- | --------------------------------------- | ------------------------------------------------------------------- |
+| `signup/signup-user-creation.service.ts` | `steps/portal-user-creation.service.ts` | Rename class to `PortalUserCreationService`                         |
+| `signup/signup-whmcs.service.ts`         | `steps/whmcs-cleanup.service.ts`        | Rename to `WhmcsCleanupService`, keep only `markClientForCleanup()` |
+
+### Delete dead code
+
+| File                                        | Reason                               |
+| ------------------------------------------- | ------------------------------------ |
+| `signup/signup-account-resolver.service.ts` | No active caller                     |
+| `signup/signup-validation.service.ts`       | No active caller                     |
+| `signup/signup.types.ts`                    | Only used by dead validation service |
+| `signup/index.ts`                           | Directory being removed              |
+
+---
+
+## Phase 2: Remove legacy migrate endpoint
+
+### Delete WhmcsLinkWorkflowService
+
+`WhmcsLinkWorkflowService` (`POST /auth/migrate`) is superseded by `AccountMigrationWorkflowService` (`POST /auth/get-started/migrate-whmcs-account`). The new flow uses OTP-based identity verification instead of WHMCS password validation — strictly more secure.
+
+**Files to modify:**
+
+- `apps/bff/src/modules/auth/auth.module.ts` — remove provider + import
+- `apps/bff/src/modules/auth/application/auth-orchestrator.service.ts` — remove `linkWhmcsUser()` method + dependency
+- `apps/bff/src/modules/auth/presentation/http/auth.controller.ts` — remove `POST /auth/migrate` endpoint
+
+**File to delete:**
+
+- `apps/bff/src/modules/auth/infra/workflows/whmcs-link-workflow.service.ts`
+
+---
+
+## Phase 3: Clean up OTP infrastructure
+
+### Extract shared OTP email-sending pattern
+
+Both `LoginOtpWorkflowService` and `VerificationWorkflowService` implement the same pattern:
+
+1. Look up email template ID from config
+2. If template exists, send via template with dynamic data
+3. If no template, send fallback HTML
+
+Extract this into a shared `OtpEmailService` (or method on existing `OtpService`).
+
+### Improve PORTAL_EXISTS redirect UX
+
+When get-started verification detects `PORTAL_EXISTS`, pass the verified email to the login page so it's prefilled. This reduces friction for users who accidentally start on the wrong page.
+
+### What stays separate (and why)
+
+- **Login OTP workflow**: OTP serves as 2FA after password validation
+- **Verification OTP workflow**: OTP serves as email ownership proof before signup
+- **LoginSessionService**: Simple (5 fields, 10min TTL, no prefill)
+- **GetStartedSessionService**: Complex (10+ fields, 1hr TTL, prefill data, handoff tokens, idempotency locking)
+
+These serve fundamentally different security purposes and have different data models. Forcing unification would create a confusing abstraction.
+
+---
+
+## Module Updates (all phases)
+
+### GetStartedModule (Phase 1)
+
+- Remove: `NewCustomerSignupWorkflowService`, `SfCompletionWorkflowService`, `WhmcsMigrationWorkflowService`
+- Remove: `SignupAccountResolverService`, `SignupValidationService`, `SignupWhmcsService`, `SignupUserCreationService`
+- Add: `AccountCreationWorkflowService`, `AccountMigrationWorkflowService`
+- Add: `PortalUserCreationService`, `WhmcsCleanupService`
+
+### GetStartedCoordinator (Phase 1)
+
+- `completeAccount()` → `accountCreation.execute(request)`
+- `signupWithEligibility()` → `accountCreation.execute(request, { withEligibility: true })`
+- `migrateWhmcsAccount()` → `accountMigration.execute(request)`
+
+### AuthModule (Phase 2)
+
+- Remove: `WhmcsLinkWorkflowService` from providers and imports
+
+### AuthOrchestrator (Phase 2)
+
+- Remove: `linkWhmcsUser()` method and `WhmcsLinkWorkflowService` dependency
+
+### AuthController (Phase 2)
+
+- Remove: `POST /auth/migrate` endpoint
diff --git a/docs/plans/2026-03-03-signup-flow-simplification-plan.md b/docs/plans/2026-03-03-signup-flow-simplification-plan.md
new file mode 100644
index 00000000..8afdb0c0
--- /dev/null
+++ b/docs/plans/2026-03-03-signup-flow-simplification-plan.md
@@ -0,0 +1,508 @@
+# Auth Flow Simplification Implementation Plan
+
+> **For Claude:** REQUIRED SUB-SKILL: Use superpowers:executing-plans to implement this plan task-by-task.
+
+**Goal:** Simplify auth flows: merge duplicate signup workflows, fix missing SF Birthdate/Sex\_\_c, remove legacy migrate endpoint, clean up OTP infrastructure, delete dead code.
+
+**Architecture:** 3 phases (can stop after any phase). Phase 1 merges signup workflows + cleans up. Phase 2 removes legacy WHMCS migration. Phase 3 extracts shared OTP pattern.
+
+**Tech Stack:** NestJS 11, TypeScript, Prisma, Salesforce jsforce, WHMCS API, argon2, BullMQ
+
+**Design doc:** `docs/plans/2026-03-03-signup-flow-simplification-design.md`
+
+---
+
+# Phase 1: Merge signup workflows + cleanup
+
+## Task 1: Move signup shared services into steps/
+
+Move `SignupUserCreationService` and `SignupWhmcsService` from `signup/` into `steps/`, renaming to remove the "Signup" prefix. Update all imports.
+
+**Files:**
+
+- Create: `apps/bff/src/modules/auth/infra/workflows/steps/portal-user-creation.service.ts`
+- Create: `apps/bff/src/modules/auth/infra/workflows/steps/whmcs-cleanup.service.ts`
+- Modify: `apps/bff/src/modules/auth/infra/workflows/steps/create-portal-user.step.ts`
+- Modify: `apps/bff/src/modules/auth/infra/workflows/steps/index.ts`
+- Modify: `apps/bff/src/modules/auth/infra/workflows/whmcs-migration-workflow.service.ts`
+- Modify: `apps/bff/src/modules/auth/get-started/get-started.module.ts`
+
+**Step 1: Create `portal-user-creation.service.ts`**
+
+Copy `signup/signup-user-creation.service.ts` to `steps/portal-user-creation.service.ts`:
+
+- Rename class: `SignupUserCreationService` → `PortalUserCreationService`
+- Update import: `SignupWhmcsService` → `WhmcsCleanupService` from `./whmcs-cleanup.service.js`
+
+**Step 2: Create `whmcs-cleanup.service.ts`**
+
+Copy `signup/signup-whmcs.service.ts` to `steps/whmcs-cleanup.service.ts`:
+
+- Rename class: `SignupWhmcsService` → `WhmcsCleanupService`
+- Keep only `markClientForCleanup()` method
+- Delete: `createClient()`, `checkExistingClient()`, `validateAddressData()` (unused by active code)
+- Remove unused imports: `SignupRequest`, `serializeWhmcsKeyValueMap`, `DomainHttpException`, `ErrorCode`, `ConfigService`, `MappingsService`, `WhmcsAccountDiscoveryService`
+- Constructor only needs: `WhmcsClientService` + `Logger`
+
+**Step 3: Update `create-portal-user.step.ts` import**
+
+```
+Line 3 — FROM: import { SignupUserCreationService } from "../signup/signup-user-creation.service.js";
+Line 3 — TO:   import { PortalUserCreationService } from "./portal-user-creation.service.js";
+```
+
+Update constructor param: `signupUserCreation` → `portalUserCreation`, update usage on line 36.
+
+**Step 4: Update `steps/index.ts` barrel**
+
+Add at end:
+
+```typescript
+export { PortalUserCreationService } from "./portal-user-creation.service.js";
+export type { UserCreationParams, CreatedUserResult } from "./portal-user-creation.service.js";
+export { WhmcsCleanupService } from "./whmcs-cleanup.service.js";
+```
+
+**Step 5: Update `whmcs-migration-workflow.service.ts` import**
+
+```
+Line 24 — FROM: import { SignupUserCreationService } from "./signup/signup-user-creation.service.js";
+Line 24 — TO:   import { PortalUserCreationService } from "./steps/portal-user-creation.service.js";
+```
+
+Update constructor param and usage accordingly. (Task 3 will refactor this further to use `CreatePortalUserStep`.)
+
+**Step 6: Update `get-started.module.ts`**
+
+- Remove imports: `SignupAccountResolverService`, `SignupValidationService`, `SignupWhmcsService`, `SignupUserCreationService`
+- Add imports: `PortalUserCreationService`, `WhmcsCleanupService` from `../infra/workflows/steps/index.js`
+- Remove from providers: `SignupAccountResolverService`, `SignupValidationService`, `SignupWhmcsService`, `SignupUserCreationService`
+- Add to providers: `PortalUserCreationService`, `WhmcsCleanupService`
+
+**Step 7: Run type-check**
+
+Run: `pnpm type-check`
+Expected: PASS
+
+**Step 8: Commit**
+
+```bash
+git add apps/bff/src/modules/auth/infra/workflows/steps/portal-user-creation.service.ts \
+       apps/bff/src/modules/auth/infra/workflows/steps/whmcs-cleanup.service.ts \
+       apps/bff/src/modules/auth/infra/workflows/steps/create-portal-user.step.ts \
+       apps/bff/src/modules/auth/infra/workflows/steps/index.ts \
+       apps/bff/src/modules/auth/infra/workflows/whmcs-migration-workflow.service.ts \
+       apps/bff/src/modules/auth/get-started/get-started.module.ts
+git commit -m "refactor: move signup shared services into steps directory"
+```
+
+---
+
+## Task 2: Create merged AccountCreationWorkflowService
+
+Merge `SfCompletionWorkflowService` + `NewCustomerSignupWorkflowService` into one workflow. Fix Birthdate/Sex\_\_c gap.
+
+**Files:**
+
+- Create: `apps/bff/src/modules/auth/infra/workflows/account-creation-workflow.service.ts`
+
+**Step 1: Create the merged workflow**
+
+Constructor dependencies (union of both old workflows):
+
+- `ConfigService` (email template IDs, APP_BASE_URL)
+- `GetStartedSessionService`
+- `DistributedLockService`
+- `UsersService`
+- `EmailService` (welcome email in eligibility path)
+- `SalesforceAccountService` (for `createContact()` — Birthdate/Sex\_\_c)
+- `AddressWriterService`
+- `ResolveSalesforceAccountStep`
+- `CreateEligibilityCaseStep`
+- `CreateWhmcsClientStep`
+- `CreatePortalUserStep`
+- `UpdateSalesforceFlagsStep`
+- `GenerateAuthResultStep`
+- `Logger`
+
+Public API:
+
+```typescript
+execute(
+  request: CompleteAccountRequest | SignupWithEligibilityRequest,
+  options?: { withEligibility?: boolean }
+): Promise<AuthResultInternal | SignupWithEligibilityResult>
+```
+
+Step sequence in `executeCreation()`:
+
+1. Check existing accounts (Portal user duplicate check)
+2. Hash password (argon2)
+3. Resolve address + names (from request or session prefill — port `resolveAddress()` and `resolveNames()` from sf-completion)
+4. **Step 1: Resolve SF Account** (CRITICAL) — `source` depends on `withEligibility`
+5. **Step 1.5: Write SF Address** (DEGRADABLE via `safeOperation`)
+6. **Step 1.6: Create SF Contact** (DEGRADABLE via `safeOperation`) — **NEW: fixes Birthdate/Sex\_\_c**
+   - Call `salesforceAccountService.createContact({ accountId, firstName, lastName, email, phone, gender, dateOfBirth })`
+7. **Step 2** (conditional): Create Eligibility Case (DEGRADABLE, only if `withEligibility`)
+8. **Step 3: Create WHMCS Client** (CRITICAL)
+9. **Step 4: Create Portal User** (CRITICAL, rollback WHMCS on fail)
+10. **Step 5: Update SF Flags** (DEGRADABLE)
+11. **Step 6: Generate Auth Result**
+12. (conditional) Send welcome email (DEGRADABLE, only if `withEligibility`) — port `sendWelcomeWithEligibilityEmail()` from new-customer-signup
+13. Invalidate session
+
+Error handling per path:
+
+- `withEligibility=true`: wrap in try/catch, return `{ success: false, errorCategory, message }` using `classifyError()` (from `workflow-error.util.ts`)
+- `withEligibility=false` (default): let exceptions propagate directly (matching current sf-completion behavior)
+
+Session handling:
+
+- Use `acquireAndMarkAsUsed(sessionToken, withEligibility ? "signup_with_eligibility" : "complete_account")`
+- `isNewCustomer = !session.sfAccountId` (same logic as sf-completion)
+- For `isNewCustomer`: require firstName, lastName, address from request
+- For SF_UNMAPPED: use session prefill data as fallback
+
+Port private helpers from sf-completion:
+
+- `validateRequest()` — checks isNewCustomer needs firstName/lastName/address
+- `ensureNoExistingAccounts()` — Portal user duplicate check
+- `resolveAddress()` — from request or session
+- `resolveNames()` — from request or session
+
+**Step 2: Run type-check**
+
+Run: `pnpm type-check`
+Expected: PASS
+
+**Step 3: Commit**
+
+```bash
+git add apps/bff/src/modules/auth/infra/workflows/account-creation-workflow.service.ts
+git commit -m "feat: add merged AccountCreationWorkflowService with Birthdate/Sex__c fix"
+```
+
+---
+
+## Task 3: Rename and refactor AccountMigrationWorkflowService
+
+Rename `WhmcsMigrationWorkflowService` → `AccountMigrationWorkflowService`. Refactor to use `CreatePortalUserStep` instead of `SignupUserCreationService` directly.
+
+**Files:**
+
+- Create: `apps/bff/src/modules/auth/infra/workflows/account-migration-workflow.service.ts`
+
+**Step 1: Create renamed + refactored file**
+
+Copy `whmcs-migration-workflow.service.ts` → `account-migration-workflow.service.ts`:
+
+- Rename class: `WhmcsMigrationWorkflowService` → `AccountMigrationWorkflowService`
+- Replace `PortalUserCreationService` (or `SignupUserCreationService` if Task 1 import not yet updated) with `CreatePortalUserStep`
+- Constructor: remove `userCreation: PortalUserCreationService`, add `portalUserStep: CreatePortalUserStep`
+- In `executeMigration()`: replace `this.userCreation.createUserWithMapping({...})` with `this.portalUserStep.execute({...})`
+- Update imports accordingly
+
+**Step 2: Run type-check**
+
+Run: `pnpm type-check`
+Expected: PASS
+
+**Step 3: Commit**
+
+```bash
+git add apps/bff/src/modules/auth/infra/workflows/account-migration-workflow.service.ts
+git commit -m "refactor: rename WhmcsMigration to AccountMigration, use CreatePortalUserStep"
+```
+
+---
+
+## Task 4: Update coordinator and module
+
+Wire new services, remove old references.
+
+**Files:**
+
+- Modify: `apps/bff/src/modules/auth/infra/workflows/get-started-coordinator.service.ts`
+- Modify: `apps/bff/src/modules/auth/get-started/get-started.module.ts`
+
+**Step 1: Update coordinator**
+
+Imports:
+
+- Remove: `NewCustomerSignupWorkflowService`, `SfCompletionWorkflowService`, `WhmcsMigrationWorkflowService`
+- Add: `AccountCreationWorkflowService`, `AccountMigrationWorkflowService`
+
+Constructor:
+
+- Remove: `newCustomerSignup`, `sfCompletion`, `whmcsMigration`
+- Add: `accountCreation: AccountCreationWorkflowService`, `accountMigration: AccountMigrationWorkflowService`
+
+Methods:
+
+- `completeAccount()`: `return this.accountCreation.execute(request);`
+- `signupWithEligibility()`: `return this.accountCreation.execute(request, { withEligibility: true });`
+- `migrateWhmcsAccount()`: `return this.accountMigration.execute(request);`
+
+**Step 2: Update module providers**
+
+Imports:
+
+- Remove: `NewCustomerSignupWorkflowService`, `SfCompletionWorkflowService`, `WhmcsMigrationWorkflowService`
+- Add: `AccountCreationWorkflowService`, `AccountMigrationWorkflowService`
+
+Providers:
+
+- Remove: `NewCustomerSignupWorkflowService`, `SfCompletionWorkflowService`, `WhmcsMigrationWorkflowService`
+- Add: `AccountCreationWorkflowService`, `AccountMigrationWorkflowService`
+
+**Step 3: Run type-check**
+
+Run: `pnpm type-check`
+Expected: PASS
+
+**Step 4: Commit**
+
+```bash
+git add apps/bff/src/modules/auth/infra/workflows/get-started-coordinator.service.ts \
+       apps/bff/src/modules/auth/get-started/get-started.module.ts
+git commit -m "refactor: wire AccountCreation and AccountMigration into coordinator and module"
+```
+
+---
+
+## Task 5: Delete old files
+
+**Step 1: Delete old workflow files**
+
+```bash
+rm apps/bff/src/modules/auth/infra/workflows/sf-completion-workflow.service.ts
+rm apps/bff/src/modules/auth/infra/workflows/new-customer-signup-workflow.service.ts
+rm apps/bff/src/modules/auth/infra/workflows/whmcs-migration-workflow.service.ts
+```
+
+**Step 2: Delete entire signup/ directory**
+
+```bash
+rm -rf apps/bff/src/modules/auth/infra/workflows/signup/
+```
+
+**Step 3: Run type-check and tests**
+
+Run: `pnpm type-check && pnpm --filter @customer-portal/bff test`
+Expected: PASS
+
+**Step 4: Commit**
+
+```bash
+git add -A
+git commit -m "chore: delete merged/deprecated signup workflow files and signup/ directory"
+```
+
+---
+
+## Task 6: Verify no stale references (Phase 1 checkpoint)
+
+**Step 1: Search for stale references in source code**
+
+Search `apps/` and `packages/` for:
+
+- `SfCompletionWorkflow`, `NewCustomerSignupWorkflow`, `WhmcsMigrationWorkflow`
+- `SignupAccountResolver`, `SignupValidation`, `SignupWhmcsService`, `SignupUserCreation`
+- `signup-account-resolver`, `signup-validation`, `signup-whmcs`, `signup-user-creation`
+
+Expected: No matches in `apps/` or `packages/` (docs/ matches are fine)
+
+**Step 2: Fix any remaining references**
+
+**Step 3: Run full type-check and tests**
+
+Run: `pnpm type-check && pnpm --filter @customer-portal/bff test`
+Expected: PASS
+
+**Step 4: Commit if fixes were needed**
+
+```bash
+git add -A
+git commit -m "fix: update remaining references to old workflow service names"
+```
+
+---
+
+# Phase 2: Remove legacy migrate endpoint
+
+## Task 7: Remove WhmcsLinkWorkflowService and /auth/migrate
+
+Remove the legacy password-based WHMCS migration. All WHMCS migration now goes through get-started OTP-based flow.
+
+**Files:**
+
+- Delete: `apps/bff/src/modules/auth/infra/workflows/whmcs-link-workflow.service.ts`
+- Modify: `apps/bff/src/modules/auth/auth.module.ts` (remove provider + import)
+- Modify: `apps/bff/src/modules/auth/application/auth-orchestrator.service.ts` (remove `linkWhmcsUser()` + dependency)
+- Modify: `apps/bff/src/modules/auth/presentation/http/auth.controller.ts` (remove `POST /auth/migrate` endpoint)
+
+**Step 1: Update AuthOrchestrator**
+
+- Remove `linkWhmcsUser()` method
+- Remove `WhmcsLinkWorkflowService` from constructor injection
+- Remove import
+
+**Step 2: Update AuthController**
+
+- Remove the `POST /auth/migrate` endpoint handler
+- Remove related imports (request DTO, etc.)
+
+**Step 3: Update AuthModule**
+
+- Remove `WhmcsLinkWorkflowService` from providers
+- Remove import
+
+**Step 4: Delete the workflow file**
+
+```bash
+rm apps/bff/src/modules/auth/infra/workflows/whmcs-link-workflow.service.ts
+```
+
+**Step 5: Search for stale references**
+
+Search for `WhmcsLinkWorkflow`, `linkWhmcsUser`, `/auth/migrate` in source code.
+
+**Step 6: Run type-check and tests**
+
+Run: `pnpm type-check && pnpm --filter @customer-portal/bff test`
+Expected: PASS
+
+**Step 7: Commit**
+
+```bash
+git add -A
+git commit -m "refactor: remove legacy /auth/migrate endpoint and WhmcsLinkWorkflowService"
+```
+
+---
+
+# Phase 3: Clean up OTP infrastructure
+
+## Task 8: Extract shared OTP email-sending pattern
+
+Both `LoginOtpWorkflowService.sendOtpEmail()` and `VerificationWorkflowService.sendOtpEmail()` implement the same pattern: look up template ID from config, send via template or fallback HTML.
+
+**Files:**
+
+- Create: `apps/bff/src/modules/auth/infra/otp/otp-email.service.ts`
+- Modify: `apps/bff/src/modules/auth/infra/workflows/login-otp-workflow.service.ts`
+- Modify: `apps/bff/src/modules/auth/infra/workflows/verification-workflow.service.ts`
+- Modify: `apps/bff/src/modules/auth/otp/otp.module.ts` (add provider)
+
+**Step 1: Create `OtpEmailService`**
+
+Extract the shared email-sending pattern:
+
+```typescript
+@Injectable()
+export class OtpEmailService {
+  constructor(
+    private readonly config: ConfigService,
+    private readonly emailService: EmailService
+  ) {}
+
+  async sendOtpCode(email: string, code: string, context: "login" | "verification"): Promise<void> {
+    // Look up template ID based on context
+    // Send via template or fallback HTML
+    // Both current implementations do the same thing with different template IDs
+  }
+}
+```
+
+**Step 2: Refactor LoginOtpWorkflowService**
+
+Replace inline `sendOtpEmail()` with `otpEmailService.sendOtpCode(email, code, 'login')`.
+
+**Step 3: Refactor VerificationWorkflowService**
+
+Replace inline `sendOtpEmail()` with `otpEmailService.sendOtpCode(email, code, 'verification')`.
+
+**Step 4: Update OtpModule**
+
+Add `OtpEmailService` to providers and exports.
+
+**Step 5: Run type-check and tests**
+
+Run: `pnpm type-check && pnpm --filter @customer-portal/bff test`
+Expected: PASS
+
+**Step 6: Commit**
+
+```bash
+git add -A
+git commit -m "refactor: extract shared OTP email service from login and verification workflows"
+```
+
+---
+
+## Task 9: Improve PORTAL_EXISTS redirect UX
+
+When get-started verification detects `PORTAL_EXISTS`, the frontend redirects to login without context. Improve this by passing the verified email so it can be prefilled.
+
+**Files:**
+
+- Modify: `apps/portal/src/features/get-started/machines/get-started.machine.ts`
+- Potentially: login page component (to accept prefilled email from query param or state)
+
+**Step 1: Update get-started machine**
+
+When `accountStatus === PORTAL_EXISTS`, redirect to login with email as query param:
+
+```typescript
+// Instead of: router.push('/login')
+// Do: router.push(`/login?email=${encodeURIComponent(verifiedEmail)}`)
+```
+
+**Step 2: Update login page to accept prefilled email**
+
+Read `email` from URL query params and prefill the email input field.
+
+**Step 3: Test manually**
+
+1. Go to get-started with an existing account email
+2. Verify via OTP
+3. Should redirect to login with email prefilled
+
+**Step 4: Commit**
+
+```bash
+git add -A
+git commit -m "feat: prefill email on login page when redirected from get-started"
+```
+
+---
+
+## Notes
+
+### Error handling difference between merged paths
+
+The `completeAccount` endpoint throws exceptions directly. The `signupWithEligibility` endpoint returns `{ success: false, message, errorCategory }`. The merged workflow preserves this:
+
+```typescript
+if (options?.withEligibility) {
+  try { return await this.executeCreation(...); }
+  catch (error) {
+    const classified = classifyError(error);
+    return { success: false, errorCategory: classified.errorCategory, message: classified.message };
+  }
+} else {
+  return await this.executeCreation(...); // exceptions propagate
+}
+```
+
+### createContact() for Birthdate/Sex\_\_c
+
+New degradable step using existing `SalesforceAccountService.createContact()`. Gender mapping:
+
+- `male` → `男性`
+- `female` → `女性`
+- `other` → `Other`
+
+### Sessions stay separate
+
+Login sessions (`LoginSessionService`) and get-started sessions (`GetStartedSessionService`) have fundamentally different data models, TTLs, and lifecycle requirements. Only the OTP email-sending pattern is worth extracting.