diff --git a/apps/api/src/app.ts b/apps/api/src/app.ts
index 16db547..900f5ca 100644
--- a/apps/api/src/app.ts
+++ b/apps/api/src/app.ts
@@ -10,6 +10,11 @@ import {
   ErrorDetailsSchema,
   ErrorEnvelopeSchema,
   GenerationErrorCategorySchema,
+  LoginCompleteRequestSchema,
+  LoginCompleteResponseSchema,
+  LoginSendRequestSchema,
+  LogoutHeadersSchema,
+  LogoutResponseSchema,
   ModelConfigSseEventSchema,
   ModelRuntimeSseEventSchema,
   RegistrationCompleteHeadersSchema,
@@ -25,6 +30,8 @@ import {
   createErrorEnvelope,
   isCorrelationId,
   type BootstrapResponse,
+  type LoginCompleteRequest,
+  type LoginSendRequest,
   type RegistrationCompleteRequest,
   type RegistrationSendRequest,
 } from "@dada/shared-contracts";
@@ -92,6 +99,8 @@ const contentSecurityPolicy = [
   "base-uri 'none'",
   "frame-ancestors 'none'",
 ].join("; ");
+const authFlowCookieName = "dada_auth_flow";
+const userSessionCookieName = "dada_session";
 
 function requestCorrelationId(headers: Record<string, string | string[] | undefined>) {
   const header = headers["x-correlation-id"];
@@ -208,6 +217,11 @@ export async function createApp(options: CreateAppOptions = {}) {
     RegistrationCompleteRequestSchema,
     RegistrationCompleteHeadersSchema,
     RegistrationCompleteResponseSchema,
+    LoginSendRequestSchema,
+    LoginCompleteRequestSchema,
+    LoginCompleteResponseSchema,
+    LogoutHeadersSchema,
+    LogoutResponseSchema,
     UserSessionResponseSchema,
     BrowserUnsupportedReasonSchema,
     BrowserSupportRequestSchema,
@@ -288,6 +302,111 @@ export async function createApp(options: CreateAppOptions = {}) {
     },
   );
 
+  app.post(
+    "/api/v1/auth/login/send",
+    {
+      attachValidation: true,
+      schema: {
+        body: Type.Ref(LoginSendRequestSchema),
+        operationId: "sendLoginCode",
+        response: {
+          200: Type.Ref(RegistrationSendResponseSchema),
+          400: Type.Ref(ErrorEnvelopeSchema),
+          409: Type.Ref(ErrorEnvelopeSchema),
+          429: Type.Ref(ErrorEnvelopeSchema),
+          503: Type.Ref(ErrorEnvelopeSchema),
+        },
+        tags: ["Authentication"],
+      },
+    },
+    async (request, reply) => {
+      if (request.validationError) return registrationValidationFailure(reply, request.id);
+      if (!options.registration) {
+        return reply.code(503).send(createErrorEnvelope({ code: "AUTH_SERVICE_UNAVAILABLE", correlationId: request.id }));
+      }
+      const existingFlow = cookieValue(headerValue(request.headers.cookie), authFlowCookieName);
+      const clientKey = existingFlow ?? randomBytes(32).toString("base64url");
+      try {
+        const body = request.body as LoginSendRequest;
+        const result = await options.registration.sendLoginCode({ clientKey, email: body.email });
+        if (!existingFlow) {
+          reply.header(
+            "Set-Cookie",
+            `${authFlowCookieName}=${clientKey}; Max-Age=${10 * 60}; Path=/; HttpOnly; SameSite=Strict`,
+          );
+        }
+        return {
+          challenge_expires_at: new Date(result.challengeExpiresAt).toISOString(),
+          registration_id: result.registrationId,
+          resend_available_at: new Date(result.resendAvailableAt).toISOString(),
+          status: result.status,
+        };
+      } catch (error) {
+        return registrationFailure(reply, request.id, error);
+      }
+    },
+  );
+
+  app.post(
+    "/api/v1/auth/login/complete",
+    {
+      attachValidation: true,
+      schema: {
+        body: Type.Ref(LoginCompleteRequestSchema),
+        headers: Type.Ref(RegistrationCompleteHeadersSchema),
+        operationId: "completeLogin",
+        response: {
+          200: Type.Ref(LoginCompleteResponseSchema),
+          400: Type.Ref(ErrorEnvelopeSchema),
+          409: Type.Ref(ErrorEnvelopeSchema),
+          429: Type.Ref(ErrorEnvelopeSchema),
+          503: Type.Ref(ErrorEnvelopeSchema),
+        },
+        tags: ["Authentication"],
+      },
+    },
+    async (request, reply) => {
+      if (request.validationError) return registrationValidationFailure(reply, request.id);
+      if (!options.registration) {
+        return reply.code(503).send(createErrorEnvelope({ code: "AUTH_SERVICE_UNAVAILABLE", correlationId: request.id }));
+      }
+      const clientKey = cookieValue(headerValue(request.headers.cookie), authFlowCookieName);
+      const idempotencyKey = headerValue(request.headers["idempotency-key"]);
+      if (!clientKey || !idempotencyKey) return registrationValidationFailure(reply, request.id);
+      try {
+        const body = request.body as LoginCompleteRequest;
+        const result = options.registration.completeLogin({
+          clientKey,
+          code: body.verification_code,
+          idempotencyKey,
+          registrationId: body.registration_id,
+        });
+        reply.header(
+          "Set-Cookie",
+          `${userSessionCookieName}=${result.sessionToken}; Max-Age=${30 * 24 * 60 * 60}; Path=/; HttpOnly; SameSite=Strict`,
+        );
+        return {
+          audience: result.audience,
+          credits: {
+            available_balance: result.credits.availableBalance,
+            reserved_balance: result.credits.reservedBalance,
+          },
+          session_expires_at: new Date(result.sessionExpiresAt).toISOString(),
+          status: result.status,
+          user: {
+            creator_name: result.user.creatorName,
+            role: result.user.role,
+            social_id: result.user.socialId,
+            status: result.user.status,
+            user_id: result.user.userId,
+          },
+        };
+      } catch (error) {
+        return registrationFailure(reply, request.id, error);
+      }
+    },
+  );
+
   app.post(
     "/api/v1/auth/register/send",
     {
@@ -299,6 +418,7 @@ export async function createApp(options: CreateAppOptions = {}) {
           200: Type.Ref(RegistrationSendResponseSchema),
           400: Type.Ref(ErrorEnvelopeSchema),
           409: Type.Ref(ErrorEnvelopeSchema),
+          429: Type.Ref(ErrorEnvelopeSchema),
           503: Type.Ref(ErrorEnvelopeSchema),
         },
         tags: ["Authentication"],
@@ -361,7 +481,7 @@ export async function createApp(options: CreateAppOptions = {}) {
         });
         reply.header(
           "Set-Cookie",
-          `dada_session=${result.sessionToken}; Max-Age=${30 * 24 * 60 * 60}; Path=/; HttpOnly; SameSite=Strict`,
+          `${userSessionCookieName}=${result.sessionToken}; Max-Age=${30 * 24 * 60 * 60}; Path=/; HttpOnly; SameSite=Strict`,
         );
         return {
           credits: {
@@ -401,7 +521,7 @@ export async function createApp(options: CreateAppOptions = {}) {
       if (!options.registration) {
         return reply.code(503).send(createErrorEnvelope({ code: "AUTH_SERVICE_UNAVAILABLE", correlationId: request.id }));
       }
-      const token = cookieValue(headerValue(request.headers.cookie), "dada_session");
+      const token = cookieValue(headerValue(request.headers.cookie), userSessionCookieName);
       const session = token ? options.registration.readUserSession(token) : undefined;
       if (!session) {
         return reply.code(401).send(createErrorEnvelope({ code: "AUTH_SESSION_INVALID", correlationId: request.id }));
@@ -413,7 +533,7 @@ export async function createApp(options: CreateAppOptions = {}) {
           available_balance: session.credits.availableBalance,
           reserved_balance: session.credits.reservedBalance,
         },
-        csrf_token: randomBytes(32).toString("base64url"),
+        csrf_token: options.registration.issueUserCsrfToken(token!),
         expires_at: new Date(session.expiresAt).toISOString(),
         user: {
           creator_name: session.user.creatorName,
@@ -426,6 +546,43 @@ export async function createApp(options: CreateAppOptions = {}) {
     },
   );
 
+  app.post(
+    "/api/v1/auth/logout",
+    {
+      attachValidation: true,
+      schema: {
+        headers: Type.Ref(LogoutHeadersSchema),
+        operationId: "logoutUser",
+        response: {
+          200: Type.Ref(LogoutResponseSchema),
+          400: Type.Ref(ErrorEnvelopeSchema),
+          401: Type.Ref(ErrorEnvelopeSchema),
+          403: Type.Ref(ErrorEnvelopeSchema),
+          503: Type.Ref(ErrorEnvelopeSchema),
+        },
+        tags: ["Authentication"],
+      },
+    },
+    async (request, reply) => {
+      if (request.validationError) return registrationValidationFailure(reply, request.id);
+      if (!options.registration) {
+        return reply.code(503).send(createErrorEnvelope({ code: "AUTH_SERVICE_UNAVAILABLE", correlationId: request.id }));
+      }
+      const token = cookieValue(headerValue(request.headers.cookie), userSessionCookieName);
+      const csrfToken = headerValue(request.headers["x-csrf-token"]);
+      if (!token || !csrfToken) {
+        return reply.code(401).send(createErrorEnvelope({ code: "AUTH_SESSION_INVALID", correlationId: request.id }));
+      }
+      try {
+        options.registration.logoutUser({ csrfToken, sessionToken: token });
+        reply.header("Set-Cookie", `${userSessionCookieName}=; Max-Age=0; Path=/; HttpOnly; SameSite=Strict`);
+        return { status: "logged_out" as const };
+      } catch (error) {
+        return registrationFailure(reply, request.id, error);
+      }
+    },
+  );
+
   app.post(
     "/api/v1/support/check",
     {
diff --git a/apps/api/src/registration-errors.ts b/apps/api/src/registration-errors.ts
index 6ab6241..b2a91c7 100644
--- a/apps/api/src/registration-errors.ts
+++ b/apps/api/src/registration-errors.ts
@@ -10,22 +10,42 @@ export type RegistrationErrorReason =
   | "privacy_consent_required"
   | "privacy_notice_version_invalid"
   | "profile_invalid"
-  | "idempotency_conflict";
+  | "idempotency_conflict"
+  | "registration_login_required"
+  | "login_registration_required"
+  | "account_suspended"
+  | "login_admin_required"
+  | "resend_too_soon"
+  | "too_many_attempts"
+  | "csrf_invalid"
+  | "session_invalid";
 
 export type RegistrationErrorCode =
   | "REGISTRATION_REJECTED"
   | "REGISTRATION_REQUEST_INVALID"
-  | "IDEMPOTENCY_KEY_CONFLICT";
+  | "IDEMPOTENCY_KEY_CONFLICT"
+  | "AUTH_ENTRY_REJECTED"
+  | "AUTH_RATE_LIMITED"
+  | "AUTH_CSRF_INVALID"
+  | "AUTH_SESSION_INVALID";
 
 export class RegistrationError extends Error {
   readonly code: RegistrationErrorCode;
-  readonly httpStatus: 400 | 409;
+  readonly httpStatus: 400 | 401 | 403 | 409 | 429;
   readonly reason: RegistrationErrorReason;
 
   constructor(code: RegistrationErrorCode, reason: RegistrationErrorReason) {
     super(code);
     this.code = code;
-    this.httpStatus = code === "REGISTRATION_REQUEST_INVALID" ? 400 : 409;
+    this.httpStatus = code === "REGISTRATION_REQUEST_INVALID"
+      ? 400
+      : code === "AUTH_SESSION_INVALID"
+        ? 401
+      : code === "AUTH_CSRF_INVALID"
+        ? 403
+        : code === "AUTH_RATE_LIMITED"
+          ? 429
+          : 409;
     this.reason = reason;
   }
 }
@@ -44,6 +64,14 @@ export function registrationFieldError(reason: RegistrationErrorReason) {
     privacy_notice_version_invalid: { field: "privacy_notice_version", message_key: "auth.privacy.notice_version_invalid" },
     profile_invalid: { field: "profile", message_key: "auth.profile.invalid" },
     stage_limit_reached: { field: "invite_code", message_key: "auth.registration.stage_limit_reached" },
+    registration_login_required: { field: "email", message_key: "auth.registration.login_required" },
+    login_registration_required: { field: "email", message_key: "auth.login.registration_required" },
+    account_suspended: { field: "email", message_key: "auth.account.suspended" },
+    login_admin_required: { field: "email", message_key: "auth.login.admin_required" },
+    resend_too_soon: { field: "verification_code", message_key: "auth.challenge.resend_too_soon" },
+    too_many_attempts: { field: "verification_code", message_key: "auth.challenge.too_many_attempts" },
+    csrf_invalid: { field: "csrf_token", message_key: "auth.csrf.invalid" },
+    session_invalid: { field: "session", message_key: "auth.session.invalid" },
   };
   return entries[reason];
 }
diff --git a/apps/api/src/registration.ts b/apps/api/src/registration.ts
index 9e15400..ea67670 100644
--- a/apps/api/src/registration.ts
+++ b/apps/api/src/registration.ts
@@ -17,10 +17,23 @@ const stageLimit = 10;
 const challengeLifetimeMilliseconds = 10 * 60 * 1_000;
 const resendDelayMilliseconds = 60 * 1_000;
 const sessionLifetimeMilliseconds = 30 * 24 * 60 * 60 * 1_000;
+const rateWindowMilliseconds = 10 * 60 * 1_000;
+const rateBlockMilliseconds = 10 * 60 * 1_000;
+const maximumFailedAttempts = 5;
+const maximumSendsPerWindow = 5;
 
 export interface RegistrationTransactionEvent {
   mode: "BEGIN IMMEDIATE";
-  operation: "invite_create" | "registration_send" | "registration_complete" | "registration_send_compensation";
+  operation:
+    | "invite_create"
+    | "registration_send"
+    | "registration_complete"
+    | "registration_send_compensation"
+    | "login_send"
+    | "login_complete"
+    | "session_issue"
+    | "session_revoke"
+    | "csrf_issue";
   outcome: "committed" | "rejected" | "idempotent_replay";
 }
 
@@ -51,7 +64,7 @@ interface ChallengeRow {
   consumed_at: number | null;
   email: string;
   expires_at: number;
-  invite_id: string;
+  invite_id: string | null;
 }
 
 interface AttemptRow {
@@ -72,6 +85,21 @@ interface UserResultRow {
   user_id: string;
 }
 
+interface RateLimitRow {
+  blocked_until: number | null;
+  failed_attempts: number;
+  send_count: number;
+  window_started_at: number;
+}
+
+interface LoginAttemptRow {
+  failure_reason: RegistrationErrorReason | null;
+  outcome_code: "success" | "failure";
+  request_hash: string;
+  session_id: string | null;
+  user_id: string | null;
+}
+
 export interface RegistrationSendResult {
   challengeExpiresAt: number;
   registrationId: string;
@@ -111,6 +139,18 @@ export interface UserSessionResult {
   userId: string;
 }
 
+export interface LoginCompleteInput {
+  clientKey: string;
+  code: string;
+  idempotencyKey: string;
+  registrationId: string;
+}
+
+export type LoginCompleteResult = Omit<RegistrationCompleteResult, "status"> & {
+  audience: "user";
+  status: "authenticated";
+};
+
 interface ImmediateResult<T> {
   outcome: RegistrationTransactionEvent["outcome"];
   value: T;
@@ -210,10 +250,13 @@ export class RegistrationService {
       this.assertInviteAvailable(invite, now);
       this.assertStageCapacity();
       const existing = this.database.prepare(`
-        SELECT user_id FROM users
+        SELECT user_id, role, status FROM users
         WHERE normalized_email = ? AND status <> 'deleted'
-      `).get(email);
-      if (existing) throw new RegistrationError("REGISTRATION_REJECTED", "email_already_registered");
+      `).get(email) as { role: "user" | "super_admin"; status: "active" | "suspended" } | undefined;
+      if (existing?.status === "suspended") throw new RegistrationError("AUTH_ENTRY_REJECTED", "account_suspended");
+      if (existing) throw new RegistrationError("AUTH_ENTRY_REJECTED", "registration_login_required");
+      this.assertChallengeSendAllowed(email, "register", "registration", now);
+      this.recordRateSend(email, "registration", now);
 
       this.database.prepare(`
         INSERT INTO email_challenges (
@@ -241,7 +284,7 @@ export class RegistrationService {
     });
 
     try {
-      await this.options.resend.sendRegistrationCode({ challengeId, code, email, purpose: "register" });
+      await this.options.resend.sendVerificationCode({ challengeId, code, email, purpose: "register" });
     } catch {
       this.runImmediate("registration_send_compensation", () => {
         this.database.prepare("DELETE FROM email_challenges WHERE challenge_id = ? AND consumed_at IS NULL").run(challengeId);
@@ -252,6 +295,143 @@ export class RegistrationService {
     return result;
   }
 
+  async sendLoginCode(input: { clientKey: string; email: string }): Promise<RegistrationSendResult> {
+    const email = normalizeEmail(input.email);
+    const clientKey = normalizeProfileValue(input.clientKey, 160);
+    const now = this.options.clock();
+    const challengeId = randomUUID();
+    const code = this.options.codeGenerator();
+    if (!/^[0-9]{6}$/.test(code)) throw new Error("Verification code generator must return six digits.");
+
+    const result = this.runImmediate("login_send", () => {
+      const user = this.database.prepare(`
+        SELECT user_id, role, status FROM users
+        WHERE normalized_email = ? AND status <> 'deleted'
+      `).get(email) as { role: "user" | "super_admin"; status: "active" | "suspended"; user_id: string } | undefined;
+      if (!user) throw new RegistrationError("AUTH_ENTRY_REJECTED", "login_registration_required");
+      if (user.status === "suspended") throw new RegistrationError("AUTH_ENTRY_REJECTED", "account_suspended");
+      if (user.role !== "user") throw new RegistrationError("AUTH_ENTRY_REJECTED", "login_admin_required");
+      this.assertChallengeSendAllowed(email, "login", clientKey, now);
+      this.recordRateSend(email, clientKey, now);
+      this.database.prepare(`
+        INSERT INTO email_challenges (
+          challenge_id, email, invite_id, code_hmac, purpose, expires_at,
+          resend_available_at, failure_count, consumed_at, created_at
+        ) VALUES (?, ?, NULL, ?, 'login', ?, ?, 0, NULL, ?)
+      `).run(
+        challengeId,
+        email,
+        this.challengeHmac(challengeId, code),
+        now + challengeLifetimeMilliseconds,
+        now + resendDelayMilliseconds,
+        now,
+      );
+      return {
+        outcome: "committed",
+        value: {
+          challengeExpiresAt: now + challengeLifetimeMilliseconds,
+          registrationId: challengeId,
+          resendAvailableAt: now + resendDelayMilliseconds,
+          status: "verification_sent" as const,
+        },
+      };
+    });
+
+    try {
+      await this.options.resend.sendVerificationCode({ challengeId, code, email, purpose: "login" });
+    } catch {
+      this.runImmediate("registration_send_compensation", () => {
+        this.database.prepare("DELETE FROM email_challenges WHERE challenge_id = ? AND consumed_at IS NULL").run(challengeId);
+        return { outcome: "committed", value: undefined };
+      });
+      throw new Error("AUTH_SERVICE_UNAVAILABLE");
+    }
+    return result;
+  }
+
+  completeLogin(input: LoginCompleteInput): LoginCompleteResult {
+    if (!/^[0-9]{6}$/.test(input.code)) throw new RegistrationError("REGISTRATION_REQUEST_INVALID", "challenge_invalid");
+    const clientKey = normalizeProfileValue(input.clientKey, 160);
+    if (input.idempotencyKey.length < 32 || input.idempotencyKey.length > 200 || !/^[A-Za-z0-9_-]+$/.test(input.idempotencyKey)) {
+      throw new RegistrationError("REGISTRATION_REQUEST_INVALID", "idempotency_conflict");
+    }
+    const now = this.options.clock();
+    const idempotencyDigest = this.keyedHmac(this.options.sessionPepper, `login-idempotency:${input.idempotencyKey}`);
+    const requestHash = this.keyedHmac(this.options.challengePepper, JSON.stringify({
+      clientKey,
+      code: input.code,
+      registrationId: input.registrationId,
+    }));
+
+    const outcome = this.runImmediate<LoginCompleteResult | RegistrationError>("login_complete", () => {
+      const previous = this.database.prepare(`
+        SELECT request_hash, outcome_code, failure_reason, user_id, session_id
+        FROM login_attempts WHERE idempotency_key_digest = ?
+      `).get(idempotencyDigest) as LoginAttemptRow | undefined;
+      if (previous) {
+        if (!constantTimeTextEqual(previous.request_hash, requestHash)) {
+          throw new RegistrationError("IDEMPOTENCY_KEY_CONFLICT", "idempotency_conflict");
+        }
+        if (previous.outcome_code === "failure") {
+          const reason = previous.failure_reason ?? "challenge_invalid";
+          const code = reason === "resend_too_soon" || reason === "too_many_attempts"
+            ? "AUTH_RATE_LIMITED"
+            : "AUTH_ENTRY_REJECTED";
+          return { outcome: "idempotent_replay", value: new RegistrationError(code, reason) };
+        }
+        return {
+          outcome: "idempotent_replay",
+          value: this.loginResult(this.readCompletedRegistration(previous.user_id!, previous.session_id!)),
+        };
+      }
+
+      const challenge = this.database.prepare(`
+        SELECT challenge_id, email, invite_id, code_hmac, expires_at, consumed_at
+        FROM email_challenges WHERE challenge_id = ? AND purpose = 'login'
+      `).get(input.registrationId) as ChallengeRow | undefined;
+      if (!challenge || challenge.consumed_at !== null) {
+        return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "challenge_invalid", now);
+      }
+      const rate = this.readRateLimit(challenge.email, clientKey, now);
+      if (rate.blocked_until !== null && rate.blocked_until > now) {
+        return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "too_many_attempts", now);
+      }
+      if (challenge.expires_at <= now) {
+        return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "challenge_expired", now);
+      }
+      if (!constantTimeTextEqual(challenge.code_hmac, this.challengeHmac(challenge.challenge_id, input.code))) {
+        this.database.prepare("UPDATE email_challenges SET failure_count = failure_count + 1 WHERE challenge_id = ?")
+          .run(challenge.challenge_id);
+        const failedAttempts = this.recordRateFailure(challenge.email, clientKey, now);
+        const reason = failedAttempts >= maximumFailedAttempts ? "too_many_attempts" : "challenge_invalid";
+        return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, reason, now);
+      }
+      const user = this.database.prepare(`
+        SELECT user_id, role, status FROM users
+        WHERE normalized_email = ? AND status <> 'deleted'
+      `).get(challenge.email) as { role: "user" | "super_admin"; status: "active" | "suspended"; user_id: string } | undefined;
+      if (!user) return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "login_registration_required", now);
+      if (user.status === "suspended") return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "account_suspended", now);
+      if (user.role !== "user") return this.recordLoginFailure(idempotencyDigest, requestHash, input.registrationId, "login_admin_required", now);
+
+      this.database.prepare("UPDATE email_challenges SET consumed_at = ? WHERE challenge_id = ? AND consumed_at IS NULL")
+        .run(now, challenge.challenge_id);
+      const issued = this.insertSession(user.user_id, "user", now);
+      this.database.prepare(`
+        INSERT INTO login_attempts (
+          idempotency_key_digest, request_hash, challenge_id, outcome_code,
+          failure_reason, user_id, session_id, created_at
+        ) VALUES (?, ?, ?, 'success', NULL, ?, ?, ?)
+      `).run(idempotencyDigest, requestHash, input.registrationId, user.user_id, issued.sessionId, now);
+      return {
+        outcome: "committed",
+        value: this.loginResult(this.readCompletedRegistration(user.user_id, issued.sessionId)),
+      };
+    });
+    if (outcome instanceof RegistrationError) throw outcome;
+    return outcome;
+  }
+
   completeRegistration(input: RegistrationCompleteInput): RegistrationCompleteResult {
     const creatorName = normalizeProfileValue(input.creatorName, 80);
     const socialId = normalizeSocialId(input.socialId);
@@ -391,6 +571,103 @@ export class RegistrationService {
     return outcome;
   }
 
+  issueAuthenticatedSession(userId: string, audience: "user" | "admin") {
+    const now = this.options.clock();
+    return this.runImmediate("session_issue", () => {
+      const user = this.database.prepare("SELECT role, status FROM users WHERE user_id = ?")
+        .get(userId) as { role: "user" | "super_admin"; status: "active" | "suspended" | "deleted" } | undefined;
+      const role = audience === "user" ? "user" : "super_admin";
+      if (!user || user.status !== "active" || user.role !== role) {
+        throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      }
+      if (audience === "admin") {
+        const access = this.database.prepare("SELECT allowed FROM admin_access WHERE user_id = ?")
+          .get(userId) as { allowed: 0 | 1 } | undefined;
+        if (access?.allowed !== 1) throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      }
+      const issued = this.insertSession(userId, audience, now);
+      return {
+        outcome: "committed",
+        value: {
+          sessionExpiresAt: issued.sessionExpiresAt,
+          sessionId: issued.sessionId,
+          sessionToken: issued.sessionToken,
+        },
+      };
+    });
+  }
+
+  issueUserCsrfToken(sessionToken: string) {
+    const now = this.options.clock();
+    const csrfToken = randomBytes(32).toString("base64url");
+    return this.runImmediate("csrf_issue", () => {
+      const session = this.database.prepare(`
+        SELECT s.session_id FROM sessions s
+        JOIN users u ON u.user_id = s.user_id
+        WHERE s.token_digest = ? AND s.audience = 'user' AND s.revoked_at IS NULL
+          AND s.expires_at > ? AND u.role = 'user' AND u.status = 'active'
+      `).get(digest(sessionToken), now) as { session_id: string } | undefined;
+      if (!session) throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      this.database.prepare("UPDATE sessions SET csrf_token_digest = ? WHERE session_id = ?")
+        .run(digest(csrfToken), session.session_id);
+      return { outcome: "committed", value: csrfToken };
+    });
+  }
+
+  logoutUser(input: { csrfToken: string; sessionToken: string }) {
+    const now = this.options.clock();
+    this.runImmediate("session_revoke", () => {
+      const session = this.database.prepare(`
+        SELECT session_id, user_id, csrf_token_digest FROM sessions
+        WHERE token_digest = ? AND audience = 'user' AND revoked_at IS NULL AND expires_at > ?
+      `).get(digest(input.sessionToken), now) as { csrf_token_digest: string | null; session_id: string; user_id: string } | undefined;
+      if (!session) throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      const csrfDigest = digest(input.csrfToken);
+      if (!session.csrf_token_digest || !constantTimeTextEqual(session.csrf_token_digest, csrfDigest)) {
+        throw new RegistrationError("AUTH_CSRF_INVALID", "csrf_invalid");
+      }
+      this.database.prepare("UPDATE sessions SET revoked_at = ? WHERE user_id = ? AND revoked_at IS NULL")
+        .run(now, session.user_id);
+      return { outcome: "committed", value: undefined };
+    });
+  }
+
+  changeUserStatus(userId: string, status: "suspended" | "deleted") {
+    const now = this.options.clock();
+    this.runImmediate("session_revoke", () => {
+      const changed = this.database.prepare("UPDATE users SET status = ? WHERE user_id = ? AND role = 'user'")
+        .run(status, userId);
+      if (changed.changes !== 1) throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      this.database.prepare("UPDATE sessions SET revoked_at = ? WHERE user_id = ? AND revoked_at IS NULL")
+        .run(now, userId);
+      return { outcome: "committed", value: undefined };
+    });
+  }
+
+  revokeAdminSessions(userId: string, reason: "logout" | "disabled" | "whitelist_removed") {
+    const now = this.options.clock();
+    this.runImmediate("session_revoke", () => {
+      const user = this.database.prepare("SELECT role FROM users WHERE user_id = ?").get(userId) as { role: string } | undefined;
+      if (user?.role !== "super_admin") throw new RegistrationError("AUTH_SESSION_INVALID", "session_invalid");
+      if (reason === "disabled") this.database.prepare("UPDATE users SET status = 'suspended' WHERE user_id = ?").run(userId);
+      if (reason === "whitelist_removed") this.database.prepare("UPDATE admin_access SET allowed = 0 WHERE user_id = ?").run(userId);
+      this.database.prepare("UPDATE sessions SET revoked_at = ? WHERE user_id = ? AND audience = 'admin' AND revoked_at IS NULL")
+        .run(now, userId);
+      return { outcome: "committed", value: undefined };
+    });
+  }
+
+  readAdminSession(token: string) {
+    const now = this.options.clock();
+    return this.database.prepare(`
+      SELECT s.expires_at, u.user_id FROM sessions s
+      JOIN users u ON u.user_id = s.user_id
+      JOIN admin_access a ON a.user_id = u.user_id
+      WHERE s.token_digest = ? AND s.audience = 'admin' AND s.revoked_at IS NULL
+        AND s.expires_at > ? AND u.role = 'super_admin' AND u.status = 'active' AND a.allowed = 1
+    `).get(digest(token), now) as { expires_at: number; user_id: string } | undefined;
+  }
+
   readUserSession(token: string): UserSessionResult | undefined {
     const now = this.options.clock();
     const row = this.database.prepare(`
@@ -484,7 +761,7 @@ export class RegistrationService {
       CREATE TABLE IF NOT EXISTS email_challenges (
         challenge_id TEXT PRIMARY KEY,
         email TEXT NOT NULL,
-        invite_id TEXT NOT NULL REFERENCES invite_codes(invite_id),
+        invite_id TEXT REFERENCES invite_codes(invite_id),
         code_hmac TEXT NOT NULL,
         purpose TEXT NOT NULL CHECK (purpose IN ('register', 'login', 'admin_login')),
         expires_at INTEGER NOT NULL,
@@ -498,6 +775,7 @@ export class RegistrationService {
         user_id TEXT NOT NULL REFERENCES users(user_id),
         audience TEXT NOT NULL CHECK (audience IN ('user', 'admin')),
         token_digest TEXT NOT NULL UNIQUE,
+        csrf_token_digest TEXT,
         created_at INTEGER NOT NULL,
         expires_at INTEGER NOT NULL,
         revoked_at INTEGER
@@ -512,6 +790,27 @@ export class RegistrationService {
         session_id TEXT REFERENCES sessions(session_id),
         created_at INTEGER NOT NULL
       );
+      CREATE TABLE IF NOT EXISTS admin_access (
+        user_id TEXT PRIMARY KEY REFERENCES users(user_id),
+        allowed INTEGER NOT NULL CHECK (allowed IN (0, 1))
+      );
+      CREATE TABLE IF NOT EXISTS auth_rate_limits (
+        rate_key TEXT PRIMARY KEY,
+        window_started_at INTEGER NOT NULL,
+        send_count INTEGER NOT NULL CHECK (send_count >= 0),
+        failed_attempts INTEGER NOT NULL CHECK (failed_attempts >= 0),
+        blocked_until INTEGER
+      );
+      CREATE TABLE IF NOT EXISTS login_attempts (
+        idempotency_key_digest TEXT PRIMARY KEY,
+        request_hash TEXT NOT NULL,
+        challenge_id TEXT NOT NULL,
+        outcome_code TEXT NOT NULL CHECK (outcome_code IN ('success', 'failure')),
+        failure_reason TEXT,
+        user_id TEXT REFERENCES users(user_id),
+        session_id TEXT REFERENCES sessions(session_id),
+        created_at INTEGER NOT NULL
+      );
     `);
   }
 
@@ -548,6 +847,117 @@ export class RegistrationService {
     return createHmac("sha256", this.options.sessionPepper).update(`session:${sessionId}`, "utf8").digest("base64url");
   }
 
+  private rateKey(email: string, clientKey: string) {
+    return this.keyedHmac(this.options.challengePepper, `rate:${email}:${clientKey}`);
+  }
+
+  private readRateLimit(email: string, clientKey: string, now: number): RateLimitRow {
+    const row = this.database.prepare(`
+      SELECT window_started_at, send_count, failed_attempts, blocked_until
+      FROM auth_rate_limits WHERE rate_key = ?
+    `).get(this.rateKey(email, clientKey)) as RateLimitRow | undefined;
+    if (!row || now - row.window_started_at >= rateWindowMilliseconds) {
+      return { blocked_until: null, failed_attempts: 0, send_count: 0, window_started_at: now };
+    }
+    return row;
+  }
+
+  private recordRateSend(email: string, clientKey: string, now: number) {
+    const key = this.rateKey(email, clientKey);
+    const row = this.readRateLimit(email, clientKey, now);
+    if (row.blocked_until !== null && row.blocked_until > now) {
+      throw new RegistrationError("AUTH_RATE_LIMITED", "too_many_attempts");
+    }
+    if (row.send_count >= maximumSendsPerWindow) {
+      throw new RegistrationError("AUTH_RATE_LIMITED", "too_many_attempts");
+    }
+    this.database.prepare(`
+      INSERT INTO auth_rate_limits (
+        rate_key, window_started_at, send_count, failed_attempts, blocked_until
+      ) VALUES (?, ?, 1, 0, NULL)
+      ON CONFLICT(rate_key) DO UPDATE SET
+        window_started_at = excluded.window_started_at,
+        send_count = ?,
+        failed_attempts = ?,
+        blocked_until = ?
+    `).run(
+      key,
+      row.window_started_at,
+      row.send_count + 1,
+      row.failed_attempts,
+      row.blocked_until,
+    );
+  }
+
+  private recordRateFailure(email: string, clientKey: string, now: number) {
+    const key = this.rateKey(email, clientKey);
+    const row = this.readRateLimit(email, clientKey, now);
+    const failedAttempts = row.failed_attempts + 1;
+    const blockedUntil = failedAttempts >= maximumFailedAttempts ? now + rateBlockMilliseconds : row.blocked_until;
+    this.database.prepare(`
+      INSERT INTO auth_rate_limits (
+        rate_key, window_started_at, send_count, failed_attempts, blocked_until
+      ) VALUES (?, ?, 0, ?, ?)
+      ON CONFLICT(rate_key) DO UPDATE SET
+        window_started_at = excluded.window_started_at,
+        send_count = ?,
+        failed_attempts = excluded.failed_attempts,
+        blocked_until = excluded.blocked_until
+    `).run(key, row.window_started_at, failedAttempts, blockedUntil, row.send_count);
+    return failedAttempts;
+  }
+
+  private assertChallengeSendAllowed(
+    email: string,
+    purpose: "register" | "login",
+    clientKey: string,
+    now: number,
+  ) {
+    const latest = this.database.prepare(`
+      SELECT resend_available_at FROM email_challenges
+      WHERE email = ? AND purpose = ? ORDER BY created_at DESC LIMIT 1
+    `).get(email, purpose) as { resend_available_at: number } | undefined;
+    if (latest && latest.resend_available_at > now) {
+      throw new RegistrationError("AUTH_RATE_LIMITED", "resend_too_soon");
+    }
+    const rate = this.readRateLimit(email, clientKey, now);
+    if ((rate.blocked_until !== null && rate.blocked_until > now) || rate.send_count >= maximumSendsPerWindow) {
+      throw new RegistrationError("AUTH_RATE_LIMITED", "too_many_attempts");
+    }
+  }
+
+  private insertSession(userId: string, audience: "user" | "admin", now: number) {
+    const sessionId = randomUUID();
+    const sessionToken = this.sessionToken(sessionId);
+    const sessionExpiresAt = now + sessionLifetimeMilliseconds;
+    this.database.prepare(`
+      INSERT INTO sessions (
+        session_id, user_id, audience, token_digest, csrf_token_digest,
+        created_at, expires_at, revoked_at
+      ) VALUES (?, ?, ?, ?, NULL, ?, ?, NULL)
+    `).run(sessionId, userId, audience, digest(sessionToken), now, sessionExpiresAt);
+    return { sessionExpiresAt, sessionId, sessionToken };
+  }
+
+  private recordLoginFailure(
+    idempotencyKeyDigest: string,
+    requestHash: string,
+    challengeId: string,
+    reason: RegistrationErrorReason,
+    now: number,
+  ): ImmediateResult<RegistrationError> {
+    this.database.prepare(`
+      INSERT INTO login_attempts (
+        idempotency_key_digest, request_hash, challenge_id, outcome_code,
+        failure_reason, user_id, session_id, created_at
+      ) VALUES (?, ?, ?, 'failure', ?, NULL, NULL, ?)
+    `).run(idempotencyKeyDigest, requestHash, challengeId, reason, now);
+    const code = reason === "resend_too_soon" || reason === "too_many_attempts"
+      ? "AUTH_RATE_LIMITED"
+      : "AUTH_ENTRY_REJECTED";
+    return { outcome: "rejected", value: new RegistrationError(code, reason) };
+  }
+
   private stageIsFull() {
     const row = this.database.prepare(`
       SELECT COUNT(*) AS count FROM users
@@ -605,6 +1015,17 @@ export class RegistrationService {
     return this.result(row);
   }
 
+  private loginResult(result: RegistrationCompleteResult): LoginCompleteResult {
+    return {
+      audience: "user",
+      credits: result.credits,
+      sessionExpiresAt: result.sessionExpiresAt,
+      sessionToken: result.sessionToken,
+      status: "authenticated",
+      user: result.user,
+    };
+  }
+
   private result(row: UserResultRow): RegistrationCompleteResult {
     return {
       credits: { availableBalance: row.available_balance, reservedBalance: row.reserved_balance },
diff --git a/apps/api/src/resend-adapter.ts b/apps/api/src/resend-adapter.ts
index 4cb2bed..a9f9516 100644
--- a/apps/api/src/resend-adapter.ts
+++ b/apps/api/src/resend-adapter.ts
@@ -2,17 +2,17 @@ export interface RegistrationCodeMessage {
   challengeId: string;
   code: string;
   email: string;
-  purpose: "register";
+  purpose: "register" | "login";
 }
 
 export interface ResendAdapter {
-  sendRegistrationCode(message: RegistrationCodeMessage): Promise<void>;
+  sendVerificationCode(message: RegistrationCodeMessage): Promise<void>;
 }
 
 export class MockResendAdapter implements ResendAdapter {
   readonly calls: RegistrationCodeMessage[] = [];
 
-  async sendRegistrationCode(message: RegistrationCodeMessage) {
+  async sendVerificationCode(message: RegistrationCodeMessage) {
     this.calls.push({ ...message });
   }
 
diff --git a/apps/web/src/generated/api/sdk.gen.ts b/apps/web/src/generated/api/sdk.gen.ts
index 566d531..8a19298 100644
--- a/apps/web/src/generated/api/sdk.gen.ts
+++ b/apps/web/src/generated/api/sdk.gen.ts
@@ -1,6 +1,6 @@
 // Generated from openapi/openapi.json. Do not edit by hand.
 
-import type { RegistrationCompleteResponse, RegistrationCompleteRequest, UserSessionResponse, RegistrationSendResponse, RegistrationSendRequest } from "./types.gen.js";
+import type { LoginCompleteResponse, LoginCompleteRequest, RegistrationCompleteResponse, RegistrationCompleteRequest, UserSessionResponse, LogoutResponse, RegistrationSendResponse, LoginSendRequest, RegistrationSendRequest } from "./types.gen.js";
 
 export interface ClientOptions { baseUrl?: string; fetch?: typeof globalThis.fetch; headers?: HeadersInit; }
 
@@ -45,6 +45,15 @@ export async function checkBrowserSupport(body: {
 }>;
 }
 
+export async function completeLogin(body: LoginCompleteRequest, options: ClientOptions = {}): Promise<LoginCompleteResponse> {
+  const request = options.fetch ?? globalThis.fetch;
+  const headers = new Headers(options.headers);
+  headers.set("Content-Type", "application/json");
+  const response = await request(`${options.baseUrl ?? ""}/api/v1/auth/login/complete`, { body: JSON.stringify(body), method: "POST", headers });
+  if (!response.ok) throw new Error(`HTTP ${response.status}`);
+  return response.json() as Promise<LoginCompleteResponse>;
+}
+
 export async function completeRegistration(body: RegistrationCompleteRequest, options: ClientOptions = {}): Promise<RegistrationCompleteResponse> {
   const request = options.fetch ?? globalThis.fetch;
   const headers = new Headers(options.headers);
@@ -104,6 +113,22 @@ export async function getUserSession(options: ClientOptions = {}): Promise<UserS
   return response.json() as Promise<UserSessionResponse>;
 }
 
+export async function logoutUser(options: ClientOptions = {}): Promise<LogoutResponse> {
+  const request = options.fetch ?? globalThis.fetch;
+  const response = await request(`${options.baseUrl ?? ""}/api/v1/auth/logout`, { method: "POST", headers: options.headers ?? {} });
+  if (!response.ok) throw new Error(`HTTP ${response.status}`);
+  return response.json() as Promise<LogoutResponse>;
+}
+
+export async function sendLoginCode(body: LoginSendRequest, options: ClientOptions = {}): Promise<RegistrationSendResponse> {
+  const request = options.fetch ?? globalThis.fetch;
+  const headers = new Headers(options.headers);
+  headers.set("Content-Type", "application/json");
+  const response = await request(`${options.baseUrl ?? ""}/api/v1/auth/login/send`, { body: JSON.stringify(body), method: "POST", headers });
+  if (!response.ok) throw new Error(`HTTP ${response.status}`);
+  return response.json() as Promise<RegistrationSendResponse>;
+}
+
 export async function sendRegistrationCode(body: RegistrationSendRequest, options: ClientOptions = {}): Promise<RegistrationSendResponse> {
   const request = options.fetch ?? globalThis.fetch;
   const headers = new Headers(options.headers);
diff --git a/apps/web/src/generated/api/types.gen.ts b/apps/web/src/generated/api/types.gen.ts
index 0f45b13..cb2d72e 100644
--- a/apps/web/src/generated/api/types.gen.ts
+++ b/apps/web/src/generated/api/types.gen.ts
@@ -78,7 +78,7 @@ export type ErrorDetails = {
 
 export type ErrorEnvelope = {
   "error": {
-  "code": "BROWSER_UNSUPPORTED" | "MODEL_CONFIG_VERSION_CONFLICT" | "MODEL_DEFAULT_REPLACEMENT_REQUIRED" | "MODEL_DEFAULT_REPLACEMENT_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_CONFLICT" | "PRIVATE_CONTENT_NOTICE_ACK_REQUIRED" | "ASSET_HISTORY_REFERENCE_CONFLICT" | "ASSET_CLEANUP_CANDIDATE_STALE" | "STORAGE_CAPACITY_EXCEEDED" | "REGISTRATION_REJECTED" | "REGISTRATION_REQUEST_INVALID" | "IDEMPOTENCY_KEY_CONFLICT" | "AUTH_SESSION_INVALID" | "AUTH_SERVICE_UNAVAILABLE";
+  "code": "BROWSER_UNSUPPORTED" | "MODEL_CONFIG_VERSION_CONFLICT" | "MODEL_DEFAULT_REPLACEMENT_REQUIRED" | "MODEL_DEFAULT_REPLACEMENT_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_CONFLICT" | "PRIVATE_CONTENT_NOTICE_ACK_REQUIRED" | "ASSET_HISTORY_REFERENCE_CONFLICT" | "ASSET_CLEANUP_CANDIDATE_STALE" | "STORAGE_CAPACITY_EXCEEDED" | "REGISTRATION_REJECTED" | "REGISTRATION_REQUEST_INVALID" | "IDEMPOTENCY_KEY_CONFLICT" | "AUTH_SESSION_INVALID" | "AUTH_SERVICE_UNAVAILABLE" | "AUTH_ENTRY_REJECTED" | "AUTH_RATE_LIMITED" | "AUTH_CSRF_INVALID";
   "correlation_id": string;
   "details": {
   "capacity_status"?: "normal" | "warning" | "critical" | "full" | "unavailable";
@@ -102,6 +102,32 @@ export type ErrorEnvelope = {
 
 export type GenerationErrorCategory = "upstream_timeout" | "upstream_failed" | "safety_rejected" | "model_disabled" | "gateway_balance_insufficient" | "gateway_contract_invalid" | "reference_invalid" | "unknown_retryable" | "unknown_non_retryable";
 
+export type LoginCompleteRequest = {
+  "registration_id": string;
+  "verification_code": string;
+};
+
+export type LoginCompleteResponse = {
+  "audience": "user";
+  "credits": CreditSummary;
+  "session_expires_at": string;
+  "status": "authenticated";
+  "user": AuthenticatedUser;
+};
+
+export type LoginSendRequest = {
+  "email": string;
+};
+
+export type LogoutHeaders = {
+  "idempotency-key": string;
+  "x-csrf-token": string;
+};
+
+export type LogoutResponse = {
+  "status": "logged_out";
+};
+
 export type ModelConfigSseEvent = {
   "config_set_version": number;
   "entity_ref": string;
@@ -170,7 +196,7 @@ export type SseEvent = {
   "runtime_availability_version": number;
 };
 
-export type StableEngineeringErrorCode = "BROWSER_UNSUPPORTED" | "MODEL_CONFIG_VERSION_CONFLICT" | "MODEL_DEFAULT_REPLACEMENT_REQUIRED" | "MODEL_DEFAULT_REPLACEMENT_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_CONFLICT" | "PRIVATE_CONTENT_NOTICE_ACK_REQUIRED" | "ASSET_HISTORY_REFERENCE_CONFLICT" | "ASSET_CLEANUP_CANDIDATE_STALE" | "STORAGE_CAPACITY_EXCEEDED" | "REGISTRATION_REJECTED" | "REGISTRATION_REQUEST_INVALID" | "IDEMPOTENCY_KEY_CONFLICT" | "AUTH_SESSION_INVALID" | "AUTH_SERVICE_UNAVAILABLE";
+export type StableEngineeringErrorCode = "BROWSER_UNSUPPORTED" | "MODEL_CONFIG_VERSION_CONFLICT" | "MODEL_DEFAULT_REPLACEMENT_REQUIRED" | "MODEL_DEFAULT_REPLACEMENT_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_INVALID" | "MODEL_RECOMMENDATION_PRIORITY_CONFLICT" | "PRIVATE_CONTENT_NOTICE_ACK_REQUIRED" | "ASSET_HISTORY_REFERENCE_CONFLICT" | "ASSET_CLEANUP_CANDIDATE_STALE" | "STORAGE_CAPACITY_EXCEEDED" | "REGISTRATION_REJECTED" | "REGISTRATION_REQUEST_INVALID" | "IDEMPOTENCY_KEY_CONFLICT" | "AUTH_SESSION_INVALID" | "AUTH_SERVICE_UNAVAILABLE" | "AUTH_ENTRY_REJECTED" | "AUTH_RATE_LIMITED" | "AUTH_CSRF_INVALID";
 
 export type StateSseEvent = {
   "entity_ref": string;
diff --git a/apps/web/src/main.tsx b/apps/web/src/main.tsx
index cf3cf82..75d77c7 100644
--- a/apps/web/src/main.tsx
+++ b/apps/web/src/main.tsx
@@ -1,8 +1,8 @@
 import { StrictMode } from "react";
 import { createRoot } from "react-dom/client";
 
-import { ToolchainProbe } from "./toolchain-probe.js";
 import { registerPublicAssetServiceWorker } from "./public-asset-cache.js";
+import { UserAuthPage } from "./user-auth.js";
 
 const root = document.getElementById("root");
 
@@ -13,8 +13,18 @@ if (!root) {
 // Cache failure leaves public assets network-backed and must not create alternate persistence.
 void registerPublicAssetServiceWorker().catch(() => undefined);
 
-createRoot(root).render(
-  <StrictMode>
-    <ToolchainProbe />
-  </StrictMode>,
-);
+const appRoot = createRoot(root);
+let authRevision = 0;
+
+function renderAuthenticationEntry() {
+  authRevision += 1;
+  appRoot.render(
+    <StrictMode>
+      <UserAuthPage key={authRevision} />
+    </StrictMode>,
+  );
+}
+
+// Any authenticated surface can dispatch this after a revoked/invalid session response.
+window.addEventListener("dada:session-invalid", renderAuthenticationEntry);
+renderAuthenticationEntry();
diff --git a/apps/web/src/user-auth.css b/apps/web/src/user-auth.css
new file mode 100644
index 0000000..f5afd8b
--- /dev/null
+++ b/apps/web/src/user-auth.css
@@ -0,0 +1,325 @@
+:root {
+  color: #111111;
+  background: #f6f6f4;
+  font-family: "Segoe UI", "Microsoft YaHei", Arial, sans-serif;
+  font-synthesis: none;
+  letter-spacing: 0;
+}
+
+* {
+  box-sizing: border-box;
+}
+
+body {
+  min-width: 320px;
+  min-height: 100vh;
+  margin: 0;
+  overflow-x: hidden;
+  background: #f6f6f4;
+}
+
+button,
+input {
+  font: inherit;
+  letter-spacing: 0;
+}
+
+button,
+a,
+input {
+  outline-offset: 3px;
+}
+
+.auth-page {
+  min-height: 100vh;
+  display: grid;
+  grid-template-rows: 230px minmax(520px, 1fr) 48px;
+}
+
+.auth-art {
+  position: relative;
+  display: grid;
+  grid-template-columns: minmax(320px, 30%) 1fr;
+  overflow: hidden;
+  border-bottom: 1px solid #c8c8c3;
+  background: #eeeee9;
+}
+
+.auth-wordmark {
+  display: flex;
+  align-items: center;
+  padding: 0 48px;
+  color: #111111;
+  background: #f2f500;
+  font-family: Arial Black, "Segoe UI", sans-serif;
+  font-size: 96px;
+  font-weight: 900;
+  line-height: 1;
+}
+
+.auth-art-copy {
+  z-index: 2;
+  display: flex;
+  flex-direction: column;
+  justify-content: center;
+  gap: 54px;
+  padding: 26px 54px 20px;
+}
+
+.auth-art-copy span {
+  font-family: Consolas, monospace;
+  font-size: 11px;
+  font-weight: 700;
+}
+
+.auth-art-copy strong {
+  max-width: 520px;
+  font-size: 27px;
+  line-height: 1.2;
+}
+
+.auth-art-block {
+  position: absolute;
+  top: 90px;
+  right: 16%;
+  width: 31%;
+  height: 92px;
+  background: #b9bab4;
+}
+
+.auth-art-line {
+  position: absolute;
+  right: 4%;
+  bottom: 38px;
+  width: 48%;
+  height: 48px;
+  border-right: 1px solid #111111;
+  border-bottom: 1px solid #111111;
+  background: #f2f500;
+}
+
+.auth-content {
+  position: relative;
+  width: min(1180px, 100%);
+  margin: 0 auto;
+  padding: 32px 28px 64px;
+}
+
+.auth-admin-link {
+  position: absolute;
+  top: 34px;
+  right: 30px;
+  color: #333333;
+  font-size: 13px;
+  text-decoration-thickness: 1px;
+  text-underline-offset: 4px;
+}
+
+.auth-panel {
+  width: min(480px, 100%);
+  margin-left: 84px;
+}
+
+.auth-tabs {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  width: 100%;
+  height: 50px;
+  border: 1px solid #8a8a86;
+}
+
+.auth-tab {
+  border: 0;
+  color: #222222;
+  background: #f6f6f4;
+  font-weight: 700;
+  cursor: pointer;
+}
+
+.auth-tab + .auth-tab {
+  border-left: 1px solid #8a8a86;
+}
+
+.auth-tab[aria-selected="true"] {
+  background: #f2f500;
+}
+
+.auth-form {
+  display: flex;
+  flex-direction: column;
+  min-height: 350px;
+  padding-top: 20px;
+}
+
+.auth-form h1 {
+  margin: 0 0 20px;
+  font-size: 27px;
+  line-height: 1.25;
+}
+
+.auth-form label {
+  margin: 0 0 7px;
+  font-size: 13px;
+  font-weight: 700;
+}
+
+.auth-form input {
+  width: 100%;
+  height: 46px;
+  margin-bottom: 16px;
+  border: 1px solid #777773;
+  border-radius: 0;
+  padding: 0 13px;
+  color: #111111;
+  background: #ffffff;
+}
+
+.auth-form input:focus {
+  border-color: #111111;
+  outline: 2px solid #f2f500;
+}
+
+.auth-code-row {
+  display: grid;
+  grid-template-columns: minmax(0, 1fr) 142px;
+  gap: 10px;
+}
+
+.auth-code-row input {
+  margin-bottom: 0;
+}
+
+.auth-secondary,
+.auth-primary {
+  height: 46px;
+  border: 1px solid #777773;
+  border-radius: 0;
+  font-weight: 700;
+}
+
+.auth-secondary {
+  background: #ffffff;
+}
+
+.auth-primary {
+  width: 100%;
+  margin-top: 14px;
+  color: #111111;
+  background: #f2f500;
+}
+
+.auth-secondary:not(:disabled),
+.auth-primary:not(:disabled) {
+  cursor: pointer;
+}
+
+.auth-secondary:disabled,
+.auth-primary:disabled {
+  color: #777773;
+  background: #deded9;
+}
+
+.auth-status,
+.auth-error {
+  min-height: 20px;
+  margin: 10px 0 0;
+  font-size: 13px;
+  line-height: 1.5;
+}
+
+.auth-status {
+  color: #3c5b32;
+}
+
+.auth-error {
+  border-left: 4px solid #c7432f;
+  padding: 8px 10px;
+  color: #8d281b;
+  background: #fff0ed;
+}
+
+.auth-local-notice {
+  display: grid;
+  place-items: center;
+  min-width: 0;
+  padding: 0 18px;
+  color: #f2f500;
+  background: #111111;
+  font-size: 12px;
+  font-weight: 700;
+  text-align: center;
+}
+
+@media (max-width: 760px) {
+  .auth-page {
+    grid-template-rows: 150px minmax(560px, 1fr) auto;
+  }
+
+  .auth-art {
+    grid-template-columns: 42% 58%;
+  }
+
+  .auth-wordmark {
+    padding: 0 18px;
+    font-size: 48px;
+  }
+
+  .auth-art-copy {
+    gap: 30px;
+    padding: 18px;
+  }
+
+  .auth-art-copy span {
+    font-size: 8px;
+  }
+
+  .auth-art-copy strong {
+    font-size: 18px;
+  }
+
+  .auth-art-block {
+    top: 54px;
+    right: 8%;
+    width: 33%;
+    height: 52px;
+  }
+
+  .auth-art-line {
+    right: 2%;
+    bottom: 20px;
+    width: 44%;
+    height: 28px;
+  }
+
+  .auth-content {
+    padding: 56px 20px 42px;
+  }
+
+  .auth-admin-link {
+    top: 22px;
+    right: 20px;
+  }
+
+  .auth-panel {
+    margin-left: 0;
+  }
+
+  .auth-code-row {
+    grid-template-columns: minmax(0, 1fr) 126px;
+  }
+
+  .auth-local-notice {
+    min-height: 56px;
+    padding-block: 12px;
+  }
+}
+
+@media (max-width: 380px) {
+  .auth-code-row {
+    grid-template-columns: 1fr;
+  }
+
+  .auth-secondary {
+    width: 100%;
+  }
+}
diff --git a/apps/web/src/user-auth.tsx b/apps/web/src/user-auth.tsx
new file mode 100644
index 0000000..2db1c6e
--- /dev/null
+++ b/apps/web/src/user-auth.tsx
@@ -0,0 +1,267 @@
+import { useEffect, useId, useRef, useState, type FormEvent } from "react";
+
+import "./user-auth.css";
+
+type AuthMode = "login" | "register";
+type SendState = "idle" | "sending" | "sent" | "error";
+
+interface ErrorEnvelopeBody {
+  error?: {
+    details?: { field_errors?: Array<{ message_key?: string }> };
+    message_key?: string;
+  };
+}
+
+const messageByKey: Record<string, string> = {
+  "auth.account.suspended": "账号已暂停，请联系管理员。",
+  "auth.challenge.expired": "验证码已过期，请重新获取。",
+  "auth.challenge.invalid": "验证码不正确，请检查后重试。",
+  "auth.challenge.resend_too_soon": "请等待倒计时结束后重新获取验证码。",
+  "auth.challenge.too_many_attempts": "尝试次数过多，请稍后再试。",
+  "auth.login.admin_required": "此邮箱需从管理员登录入口进入。",
+  "auth.login.registration_required": "该邮箱尚未注册，请切换到注册。",
+  "auth.service.unavailable": "邮件服务暂时不可用，请稍后重试。",
+};
+
+function errorMessage(body: ErrorEnvelopeBody) {
+  const key = body.error?.details?.field_errors?.[0]?.message_key ?? body.error?.message_key;
+  return key ? (messageByKey[key] ?? "请求未完成，请检查后重试。") : "请求未完成，请检查后重试。";
+}
+
+function maskedEmail(email: string) {
+  const [local = "", domain = ""] = email.split("@", 2);
+  const visible = local.slice(0, Math.min(2, local.length));
+  return `${visible}${"*".repeat(Math.max(3, local.length - visible.length))}@${domain}`;
+}
+
+export function UserAuthPage() {
+  const emailId = useId();
+  const codeId = useId();
+  const inviteId = useId();
+  const loginTab = useRef<HTMLButtonElement>(null);
+  const registerTab = useRef<HTMLButtonElement>(null);
+  const [mode, setMode] = useState<AuthMode>("login");
+  const [email, setEmail] = useState("");
+  const [code, setCode] = useState("");
+  const [inviteCode, setInviteCode] = useState("");
+  const [registrationId, setRegistrationId] = useState<string>();
+  const [sendState, setSendState] = useState<SendState>("idle");
+  const [countdown, setCountdown] = useState(0);
+  const [error, setError] = useState<string>();
+  const [submitting, setSubmitting] = useState(false);
+  const emailValid = /^[^@\s]+@[^@\s]+$/.test(email);
+
+  useEffect(() => {
+    if (countdown <= 0) return;
+    const timer = window.setInterval(() => setCountdown((value) => Math.max(0, value - 1)), 1_000);
+    return () => window.clearInterval(timer);
+  }, [countdown]);
+
+  function switchMode(nextMode: AuthMode) {
+    if (nextMode === mode) return;
+    setMode(nextMode);
+    setCode("");
+    setInviteCode("");
+    setRegistrationId(undefined);
+    setSendState("idle");
+    setCountdown(0);
+    setError(undefined);
+  }
+
+  function switchTab(nextMode: AuthMode) {
+    switchMode(nextMode);
+    window.requestAnimationFrame(() => (nextMode === "login" ? loginTab : registerTab).current?.focus());
+  }
+
+  async function sendCode() {
+    if (!emailValid || sendState === "sending" || countdown > 0) return;
+    setSendState("sending");
+    setError(undefined);
+    const endpoint = mode === "login" ? "/api/v1/auth/login/send" : "/api/v1/auth/register/send";
+    const payload = mode === "login" ? { email } : { email, invite_code: inviteCode };
+    try {
+      const response = await fetch(endpoint, {
+        body: JSON.stringify(payload),
+        credentials: "same-origin",
+        headers: { "Content-Type": "application/json" },
+        method: "POST",
+      });
+      const body = await response.json() as ErrorEnvelopeBody & { registration_id?: string };
+      if (!response.ok || !body.registration_id) {
+        setSendState("error");
+        setError(errorMessage(body));
+        return;
+      }
+      setRegistrationId(body.registration_id);
+      setSendState("sent");
+      setCountdown(60);
+    } catch {
+      setSendState("error");
+      setError(messageByKey["auth.service.unavailable"]);
+    }
+  }
+
+  async function login(event: FormEvent) {
+    event.preventDefault();
+    if (!registrationId || !/^[0-9]{6}$/.test(code) || submitting) return;
+    setSubmitting(true);
+    setError(undefined);
+    try {
+      const response = await fetch("/api/v1/auth/login/complete", {
+        body: JSON.stringify({ registration_id: registrationId, verification_code: code }),
+        credentials: "same-origin",
+        headers: {
+          "Content-Type": "application/json",
+          "Idempotency-Key": crypto.randomUUID().replaceAll("-", "") + crypto.randomUUID().replaceAll("-", ""),
+        },
+        method: "POST",
+      });
+      const body = await response.json() as ErrorEnvelopeBody;
+      if (!response.ok) {
+        setError(errorMessage(body));
+        return;
+      }
+      window.location.assign("/app");
+    } catch {
+      setError("登录请求未完成，请重试。");
+    } finally {
+      setSubmitting(false);
+    }
+  }
+
+  return (
+    <main className="auth-page">
+      <section className="auth-art" aria-label="Dada 创作艺术带">
+        <div className="auth-wordmark">DADA</div>
+        <div className="auth-art-copy">
+          <span>LOCAL CREATIVE SYSTEM / WINDOWS P0-A</span>
+          <strong>在本机展开你的创作</strong>
+        </div>
+        <div className="auth-art-block" aria-hidden="true" />
+        <div className="auth-art-line" aria-hidden="true" />
+      </section>
+
+      <section className="auth-content">
+        <a className="auth-admin-link" href="/admin">管理员登录</a>
+        <div className="auth-panel">
+          <div className="auth-tabs" role="tablist" aria-label="认证方式">
+            <button
+              aria-selected={mode === "login"}
+              className="auth-tab"
+              onClick={() => switchMode("login")}
+              onKeyDown={(event) => {
+                if (event.key === "ArrowRight") {
+                  event.preventDefault();
+                  switchTab("register");
+                }
+              }}
+              ref={loginTab}
+              role="tab"
+              tabIndex={mode === "login" ? 0 : -1}
+              type="button"
+            >
+              登录
+            </button>
+            <button
+              aria-selected={mode === "register"}
+              className="auth-tab"
+              onClick={() => switchMode("register")}
+              onKeyDown={(event) => {
+                if (event.key === "ArrowLeft") {
+                  event.preventDefault();
+                  switchTab("login");
+                }
+              }}
+              ref={registerTab}
+              role="tab"
+              tabIndex={mode === "register" ? 0 : -1}
+              type="button"
+            >
+              注册
+            </button>
+          </div>
+
+          {mode === "login" ? (
+            <form className="auth-form" onSubmit={login}>
+              <h1>邮箱验证码登录</h1>
+              <label htmlFor={emailId}>邮箱</label>
+              <input
+                autoComplete="email"
+                id={emailId}
+                inputMode="email"
+                onChange={(event) => setEmail(event.target.value)}
+                placeholder="请输入邮箱"
+                type="email"
+                value={email}
+              />
+              <label htmlFor={codeId}>验证码</label>
+              <div className="auth-code-row">
+                <input
+                  autoComplete="one-time-code"
+                  id={codeId}
+                  inputMode="numeric"
+                  maxLength={6}
+                  onChange={(event) => setCode(event.target.value.replace(/\D/g, ""))}
+                  placeholder="6 位验证码"
+                  value={code}
+                />
+                <button
+                  className="auth-secondary"
+                  disabled={!emailValid || sendState === "sending" || countdown > 0}
+                  onClick={sendCode}
+                  type="button"
+                >
+                  {sendState === "sending" ? "发送中" : countdown > 0 ? `${countdown}s` : "获取验证码"}
+                </button>
+              </div>
+              {sendState === "sent" ? (
+                <p className="auth-status" role="status">验证码已发送至 {maskedEmail(email)}</p>
+              ) : null}
+              {error ? <p className="auth-error" role="alert">{error}</p> : null}
+              <button
+                className="auth-primary"
+                disabled={!registrationId || code.length !== 6 || submitting}
+                type="submit"
+              >
+                {submitting ? "登录中" : "登录"}
+              </button>
+            </form>
+          ) : (
+            <section className="auth-form" aria-labelledby="registration-title">
+              <h1 id="registration-title">邀请码注册</h1>
+              <label htmlFor={inviteId}>邀请码</label>
+              <input
+                autoComplete="off"
+                id={inviteId}
+                onChange={(event) => setInviteCode(event.target.value)}
+                value={inviteCode}
+              />
+              <label htmlFor={emailId}>邮箱</label>
+              <input
+                autoComplete="email"
+                id={emailId}
+                inputMode="email"
+                onChange={(event) => setEmail(event.target.value)}
+                type="email"
+                value={email}
+              />
+              <button
+                className="auth-primary"
+                disabled={!emailValid || inviteCode.trim().length < 8 || sendState === "sending" || countdown > 0}
+                onClick={sendCode}
+                type="button"
+              >
+                {sendState === "sending" ? "发送中" : countdown > 0 ? `${countdown}s` : "获取验证码"}
+              </button>
+              {error ? <p className="auth-error" role="alert">{error}</p> : null}
+            </section>
+          )}
+        </div>
+      </section>
+
+      <footer className="auth-local-notice">
+        测试数据仅保存在本机，不自动备份，也不会迁移到正式系统。
+      </footer>
+    </main>
+  );
+}
diff --git a/openapi/openapi.json b/openapi/openapi.json
index 67d243c..9b33945 100644
--- a/openapi/openapi.json
+++ b/openapi/openapi.json
@@ -639,6 +639,24 @@
                       "AUTH_SERVICE_UNAVAILABLE"
                     ],
                     "type": "string"
+                  },
+                  {
+                    "enum": [
+                      "AUTH_ENTRY_REJECTED"
+                    ],
+                    "type": "string"
+                  },
+                  {
+                    "enum": [
+                      "AUTH_RATE_LIMITED"
+                    ],
+                    "type": "string"
+                  },
+                  {
+                    "enum": [
+                      "AUTH_CSRF_INVALID"
+                    ],
+                    "type": "string"
                   }
                 ]
               },
@@ -929,6 +947,110 @@
           }
         ]
       },
+      "LoginCompleteRequest": {
+        "additionalProperties": false,
+        "properties": {
+          "registration_id": {
+            "pattern": "^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$",
+            "type": "string"
+          },
+          "verification_code": {
+            "pattern": "^[0-9]{6}$",
+            "type": "string"
+          }
+        },
+        "required": [
+          "registration_id",
+          "verification_code"
+        ],
+        "type": "object"
+      },
+      "LoginCompleteResponse": {
+        "additionalProperties": false,
+        "properties": {
+          "audience": {
+            "enum": [
+              "user"
+            ],
+            "type": "string"
+          },
+          "credits": {
+            "$ref": "#/components/schemas/CreditSummary"
+          },
+          "session_expires_at": {
+            "pattern": "^[0-9]{4}-[0-9]{2}-[0-9]{2}T[0-9]{2}:[0-9]{2}:[0-9]{2}\\.[0-9]{3}Z$",
+            "type": "string"
+          },
+          "status": {
+            "enum": [
+              "authenticated"
+            ],
+            "type": "string"
+          },
+          "user": {
+            "$ref": "#/components/schemas/AuthenticatedUser"
+          }
+        },
+        "required": [
+          "audience",
+          "credits",
+          "session_expires_at",
+          "status",
+          "user"
+        ],
+        "type": "object"
+      },
+      "LoginSendRequest": {
+        "additionalProperties": false,
+        "properties": {
+          "email": {
+            "maxLength": 320,
+            "pattern": "^[^@\\s]{1,128}@[^@\\s]{1,190}$",
+            "type": "string"
+          }
+        },
+        "required": [
+          "email"
+        ],
+        "type": "object"
+      },
+      "LogoutHeaders": {
+        "additionalProperties": true,
+        "properties": {
+          "idempotency-key": {
+            "maxLength": 200,
+            "minLength": 32,
+            "pattern": "^[A-Za-z0-9_-]+$",
+            "type": "string"
+          },
+          "x-csrf-token": {
+            "maxLength": 64,
+            "minLength": 43,
+            "pattern": "^[A-Za-z0-9_-]+$",
+            "type": "string"
+          }
+        },
+        "required": [
+          "idempotency-key",
+          "x-csrf-token"
+        ],
+        "type": "object"
+      },
+      "LogoutResponse": {
+        "additionalProperties": false,
+        "properties": {
+          "status": {
+            "enum": [
+              "logged_out"
+            ],
+            "type": "string"
+          }
+        },
+        "required": [
+          "status"
+        ],
+        "type": "object"
+      },
       "ModelConfigSseEvent": {
         "additionalProperties": false,
         "properties": {
@@ -1336,6 +1458,24 @@
               "AUTH_SERVICE_UNAVAILABLE"
             ],
             "type": "string"
+          },
+          {
+            "enum": [
+              "AUTH_ENTRY_REJECTED"
+            ],
+            "type": "string"
+          },
+          {
+            "enum": [
+              "AUTH_RATE_LIMITED"
+            ],
+            "type": "string"
+          },
+          {
+            "enum": [
+              "AUTH_CSRF_INVALID"
+            ],
+            "type": "string"
           }
         ]
       },
@@ -1424,6 +1564,243 @@
   },
   "openapi": "3.1.0",
   "paths": {
+    "/api/v1/auth/login/complete": {
+      "post": {
+        "operationId": "completeLogin",
+        "parameters": [
+          {
+            "in": "header",
+            "name": "idempotency-key",
+            "required": true,
+            "schema": {
+              "maxLength": 200,
+              "minLength": 32,
+              "pattern": "^[A-Za-z0-9_-]+$",
+              "type": "string"
+            }
+          }
+        ],
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/LoginCompleteRequest"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/LoginCompleteResponse"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "409": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "429": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "503": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          }
+        },
+        "tags": [
+          "Authentication"
+        ]
+      }
+    },
+    "/api/v1/auth/login/send": {
+      "post": {
+        "operationId": "sendLoginCode",
+        "requestBody": {
+          "content": {
+            "application/json": {
+              "schema": {
+                "$ref": "#/components/schemas/LoginSendRequest"
+              }
+            }
+          },
+          "required": true
+        },
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/RegistrationSendResponse"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "409": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "429": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "503": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          }
+        },
+        "tags": [
+          "Authentication"
+        ]
+      }
+    },
+    "/api/v1/auth/logout": {
+      "post": {
+        "operationId": "logoutUser",
+        "parameters": [
+          {
+            "in": "header",
+            "name": "idempotency-key",
+            "required": true,
+            "schema": {
+              "maxLength": 200,
+              "minLength": 32,
+              "pattern": "^[A-Za-z0-9_-]+$",
+              "type": "string"
+            }
+          },
+          {
+            "in": "header",
+            "name": "x-csrf-token",
+            "required": true,
+            "schema": {
+              "maxLength": 64,
+              "minLength": 43,
+              "pattern": "^[A-Za-z0-9_-]+$",
+              "type": "string"
+            }
+          }
+        ],
+        "responses": {
+          "200": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/LogoutResponse"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "400": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "401": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "403": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
+          "503": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          }
+        },
+        "tags": [
+          "Authentication"
+        ]
+      }
+    },
     "/api/v1/auth/register/complete": {
       "post": {
         "operationId": "completeRegistration",
@@ -1541,6 +1918,16 @@
             },
             "description": "Default Response"
           },
+          "429": {
+            "content": {
+              "application/json": {
+                "schema": {
+                  "$ref": "#/components/schemas/ErrorEnvelope"
+                }
+              }
+            },
+            "description": "Default Response"
+          },
           "503": {
             "content": {
               "application/json": {
@@ -1869,6 +2256,24 @@
                                 "AUTH_SERVICE_UNAVAILABLE"
                               ],
                               "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_ENTRY_REJECTED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_RATE_LIMITED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_CSRF_INVALID"
+                              ],
+                              "type": "string"
                             }
                           ]
                         },
@@ -2333,6 +2738,24 @@
                                 "AUTH_SERVICE_UNAVAILABLE"
                               ],
                               "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_ENTRY_REJECTED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_RATE_LIMITED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_CSRF_INVALID"
+                              ],
+                              "type": "string"
                             }
                           ]
                         },
@@ -2838,6 +3261,24 @@
                                 "AUTH_SERVICE_UNAVAILABLE"
                               ],
                               "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_ENTRY_REJECTED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_RATE_LIMITED"
+                              ],
+                              "type": "string"
+                            },
+                            {
+                              "enum": [
+                                "AUTH_CSRF_INVALID"
+                              ],
+                              "type": "string"
                             }
                           ]
                         },
diff --git a/package.json b/package.json
index 0420146..dba05c9 100644
--- a/package.json
+++ b/package.json
@@ -14,7 +14,7 @@
     "test:integration": "vitest run tests/integration",
     "test:api": "pnpm check:openapi && vitest run tests/api",
     "test:worker": "pnpm --filter @dada/worker build && node scripts/worker-smoke.mjs && vitest run tests/worker",
-    "test:e2e": "pnpm check:openapi && playwright test tests/e2e/event-sync.spec.ts tests/e2e/support-gate.spec.ts tests/e2e/local-data-boundary.spec.ts tests/e2e/storage-capacity.spec.ts tests/e2e/public-asset-cache.spec.ts --config playwright.config.ts",
+    "test:e2e": "pnpm check:openapi && playwright test tests/e2e/event-sync.spec.ts tests/e2e/support-gate.spec.ts tests/e2e/local-data-boundary.spec.ts tests/e2e/storage-capacity.spec.ts tests/e2e/public-asset-cache.spec.ts tests/e2e/user-auth.spec.ts tests/e2e/entry-state-ui.spec.ts tests/e2e/session-invalid-ui.spec.ts --config playwright.config.ts",
     "test:visual": "node scripts/validate-layer-scope.mjs VISUAL",
     "test:performance": "node scripts/validate-layer-scope.mjs PERFORMANCE",
     "test:security": "node scripts/verify-frozen-dependencies.mjs && node scripts/redaction-scan.mjs",
@@ -41,7 +41,9 @@
     "test:wp0-09": "node scripts/run-wp0-09-validation.mjs",
     "test:wp0-09:red": "node scripts/run-wp0-09-validation.mjs --phase red",
     "test:wp1-01": "node scripts/run-wp1-01-validation.mjs",
-    "test:wp1-01:red": "node scripts/run-wp1-01-validation.mjs --phase red"
+    "test:wp1-01:red": "node scripts/run-wp1-01-validation.mjs --phase red",
+    "test:wp1-02": "node scripts/run-wp1-02-validation.mjs",
+    "test:wp1-02:red": "node scripts/run-wp1-02-validation.mjs --phase red"
   },
   "devDependencies": {
     "@playwright/test": "1.62.0",
diff --git a/packages/shared-contracts/src/api.ts b/packages/shared-contracts/src/api.ts
index dab1ed8..59f76b7 100644
--- a/packages/shared-contracts/src/api.ts
+++ b/packages/shared-contracts/src/api.ts
@@ -19,6 +19,9 @@ export const stableEngineeringErrors = {
   IDEMPOTENCY_KEY_CONFLICT: { httpStatus: 409, messageKey: "request.idempotency_conflict" },
   AUTH_SESSION_INVALID: { httpStatus: 401, messageKey: "auth.session.invalid" },
   AUTH_SERVICE_UNAVAILABLE: { httpStatus: 503, messageKey: "auth.service.unavailable" },
+  AUTH_ENTRY_REJECTED: { httpStatus: 409, messageKey: "auth.entry.rejected" },
+  AUTH_RATE_LIMITED: { httpStatus: 429, messageKey: "auth.rate_limited" },
+  AUTH_CSRF_INVALID: { httpStatus: 403, messageKey: "auth.csrf.invalid" },
 } as const;
 
 export type StableEngineeringErrorCode = keyof typeof stableEngineeringErrors;
@@ -55,6 +58,9 @@ export const StableEngineeringErrorCodeSchema = Type.Union(
     Type.Literal("IDEMPOTENCY_KEY_CONFLICT"),
     Type.Literal("AUTH_SESSION_INVALID"),
     Type.Literal("AUTH_SERVICE_UNAVAILABLE"),
+    Type.Literal("AUTH_ENTRY_REJECTED"),
+    Type.Literal("AUTH_RATE_LIMITED"),
+    Type.Literal("AUTH_CSRF_INVALID"),
   ],
   { $id: "StableEngineeringErrorCode" },
 );
diff --git a/packages/shared-contracts/src/auth.ts b/packages/shared-contracts/src/auth.ts
index abe54d4..a01a909 100644
--- a/packages/shared-contracts/src/auth.ts
+++ b/packages/shared-contracts/src/auth.ts
@@ -82,8 +82,49 @@ export const UserSessionResponseSchema = Type.Object(
   { additionalProperties: false, $id: "UserSessionResponse" },
 );
 
+export const LoginSendRequestSchema = Type.Object(
+  {
+    email: Type.String({ maxLength: 320, pattern: emailPattern }),
+  },
+  { additionalProperties: false, $id: "LoginSendRequest" },
+);
+
+export const LoginCompleteRequestSchema = Type.Object(
+  {
+    registration_id: Type.String({ pattern: uuidPattern }),
+    verification_code: Type.String({ pattern: "^[0-9]{6}$" }),
+  },
+  { additionalProperties: false, $id: "LoginCompleteRequest" },
+);
+
+export const LoginCompleteResponseSchema = Type.Object(
+  {
+    audience: Type.Literal("user"),
+    credits: Type.Ref(CreditSummarySchema),
+    session_expires_at: Type.String({ pattern: isoTimestampPattern }),
+    status: Type.Literal("authenticated"),
+    user: Type.Ref(AuthenticatedUserSchema),
+  },
+  { additionalProperties: false, $id: "LoginCompleteResponse" },
+);
+
+export const LogoutHeadersSchema = Type.Object(
+  {
+    "idempotency-key": Type.String({ maxLength: 200, minLength: 32, pattern: "^[A-Za-z0-9_-]+$" }),
+    "x-csrf-token": Type.String({ maxLength: 64, minLength: 43, pattern: "^[A-Za-z0-9_-]+$" }),
+  },
+  { additionalProperties: true, $id: "LogoutHeaders" },
+);
+
+export const LogoutResponseSchema = Type.Object(
+  { status: Type.Literal("logged_out") },
+  { additionalProperties: false, $id: "LogoutResponse" },
+);
+
 export type RegistrationSendRequest = Static<typeof RegistrationSendRequestSchema>;
 export type RegistrationSendResponse = Static<typeof RegistrationSendResponseSchema>;
 export type RegistrationCompleteRequest = Static<typeof RegistrationCompleteRequestSchema>;
 export type RegistrationCompleteResponse = Static<typeof RegistrationCompleteResponseSchema>;
 export type UserSessionResponse = Static<typeof UserSessionResponseSchema>;
+export type LoginSendRequest = Static<typeof LoginSendRequestSchema>;
+export type LoginCompleteRequest = Static<typeof LoginCompleteRequestSchema>;
diff --git a/scripts/run-wp1-02-validation.mjs b/scripts/run-wp1-02-validation.mjs
new file mode 100644
index 0000000..f45dab1
--- /dev/null
+++ b/scripts/run-wp1-02-validation.mjs
@@ -0,0 +1,101 @@
+import { createHash } from "node:crypto";
+import { spawnSync } from "node:child_process";
+import { copyFileSync, existsSync, mkdirSync, readFileSync, readdirSync, statSync, writeFileSync } from "node:fs";
+import { resolve } from "node:path";
+
+const phaseIndex = process.argv.indexOf("--phase");
+const phase = phaseIndex >= 0 ? process.argv[phaseIndex + 1] : "green";
+if (!["red", "green"].includes(phase)) throw new Error(`Unsupported phase: ${phase}`);
+const runId = process.env.DADA_TDD_RUN_ID ?? `wp1-02-${phase}-${new Date().toISOString().replace(/[^0-9]/g, "")}`;
+const runDirectory = resolve("artifacts", "tdd", runId);
+const cases = [
+  "TDD-WP1-AUTH-003-entry-state-matrix",
+  "TDD-WP1-AUTH-004-challenge-guards",
+  "TDD-WP1-AUTH-004-session-revocation",
+];
+const directories = Object.fromEntries(cases.map((id) => [id, resolve(runDirectory, "cases", id)]));
+const playwrightDirectory = resolve(runDirectory, "playwright");
+if (existsSync(runDirectory)) throw new Error(`Evidence run already exists: ${runId}`);
+for (const directory of Object.values(directories)) mkdirSync(directory, { recursive: true });
+
+const commandsToRun = phase === "red"
+  ? [
+      ["pnpm exec vitest run tests/integration/wp1-02-auth-state.test.ts", ["exec", "vitest", "run", "tests/integration/wp1-02-auth-state.test.ts"]],
+      ["pnpm exec vitest run tests/api/wp1-02-login-session.test.ts", ["exec", "vitest", "run", "tests/api/wp1-02-login-session.test.ts"]],
+      ["pnpm exec playwright test tests/e2e/user-auth.spec.ts tests/e2e/entry-state-ui.spec.ts tests/e2e/session-invalid-ui.spec.ts --config playwright.config.ts", ["exec", "playwright", "test", "tests/e2e/user-auth.spec.ts", "tests/e2e/entry-state-ui.spec.ts", "tests/e2e/session-invalid-ui.spec.ts", "--config", "playwright.config.ts"]],
+    ]
+  : [
+      ["pnpm test:api", ["test:api"]],
+      ["pnpm test:e2e", ["test:e2e"]],
+      ["pnpm test:integration", ["test:integration"]],
+      ["pnpm validate:tdd-trace", ["validate:tdd-trace"]],
+    ];
+const environment = {
+  ...process.env,
+  DADA_EVIDENCE_DIR_AUTH_GUARDS: directories[cases[1]],
+  DADA_EVIDENCE_DIR_AUTH_MATRIX: directories[cases[0]],
+  DADA_EVIDENCE_DIR_AUTH_REVOKE: directories[cases[2]],
+  DADA_PLAYWRIGHT_OUTPUT_DIR: playwrightDirectory,
+};
+const startedAt = new Date().toISOString();
+const commandResults = [];
+for (const [command, args] of commandsToRun) {
+  const started_at = new Date().toISOString();
+  const executable = process.platform === "win32" ? (process.env.ComSpec ?? "cmd.exe") : "pnpm";
+  const actualArgs = process.platform === "win32" ? ["/d", "/s", "/c", `pnpm ${args.join(" ")}`] : args;
+  const execution = spawnSync(executable, actualArgs, { encoding: "utf8", env: environment });
+  if (execution.stdout) process.stdout.write(execution.stdout);
+  if (execution.stderr) process.stderr.write(execution.stderr);
+  commandResults.push({ command, exit_code: execution.status ?? 1, finished_at: new Date().toISOString(), started_at });
+}
+
+function find(root, name) {
+  if (!existsSync(root)) return [];
+  return readdirSync(root).flatMap((entry) => {
+    const child = resolve(root, entry);
+    return statSync(child).isDirectory() ? find(child, name) : entry === name ? [child] : [];
+  });
+}
+if (phase === "green") {
+  const traces = find(playwrightDirectory, "trace.zip");
+  const entryTrace = traces.find((path) => path.replaceAll("\\", "/").includes("entry-state-ui"));
+  const revocationTrace = traces.find((path) => path.replaceAll("\\", "/").includes("session-invalid-ui"));
+  if (entryTrace) copyFileSync(entryTrace, resolve(directories[cases[0]], "trace.zip"));
+  if (revocationTrace) copyFileSync(revocationTrace, resolve(directories[cases[2]], "trace.zip"));
+}
+
+const commands = { commands: commandResults, phase, run_id: runId, schema_version: "1.0" };
+for (const directory of Object.values(directories)) writeFileSync(resolve(directory, "commands.json"), `${JSON.stringify(commands, null, 2)}\n`);
+const expectedEvidence = {
+  [cases[0]]: ["response.json", "db-diff.json", "trace.zip", "screenshots/entry-state.png"],
+  [cases[1]]: ["response.json", "db-diff.json", "external-calls.json"],
+  [cases[2]]: ["response.json", "db-diff.json", "trace.zip", "screenshots/revoked.png"],
+};
+const manifest = { path: "tasks.manifest.json", sha256: createHash("sha256").update(readFileSync("tasks.manifest.json")).digest("hex").toUpperCase() };
+const commandState = phase === "red" ? commandResults.every((item) => item.exit_code !== 0) : commandResults.every((item) => item.exit_code === 0);
+const commit = spawnSync("git", ["rev-parse", "--short", "HEAD"], { encoding: "utf8" }).stdout.trim();
+const worktreeDirty = spawnSync("git", ["status", "--porcelain"], { encoding: "utf8" }).stdout.trim().length > 0;
+const results = cases.map((testId) => {
+  const evidence_refs = expectedEvidence[testId];
+  const missing_evidence = phase === "green" ? evidence_refs.filter((path) => !existsSync(resolve(directories[testId], path))) : [];
+  const status = phase === "red" ? (commandState ? "red_confirmed" : "failed") : (commandState && missing_evidence.length === 0 ? "passed" : "failed");
+  const result = {
+    acceptance_criteria: ["AC-22", "AC-33", "AC-49"], automation: ["automated"], commit,
+    environment: { arch: process.arch, node: process.version.slice(1), os: process.platform }, evidence_refs,
+    finished_at: new Date().toISOString(), layer: ["API", "E2E", "DB"], manifest, missing_evidence,
+    parent_family: testId.match(/^(TDD-WP[0-7]-[A-Z0-9]+-[0-9]{3})-/)?.[1], phase,
+    release_gate: ["work_package:WP-1", "release:P0-A"],
+    requirements: ["AUTH-01", "AUTH-02", "AUTH-04", "AUTH-05", "AUTH-06", "AUTH-07"],
+    run_id: runId, schema_version: "1.0", started_at: startedAt, status,
+    task_id: "TASK-WP1-02", test_id: testId, work_package: "WP-1",
+    worktree_under_test: worktreeDirty ? "uncommitted implementation" : "clean committed implementation",
+  };
+  writeFileSync(resolve(directories[testId], "result.json"), `${JSON.stringify(result, null, 2)}\n`);
+  return result;
+});
+const targetStatus = phase === "red" ? "red_confirmed" : "passed";
+const passed = results.every((result) => result.status === targetStatus);
+const summary = { cases: results.map(({ missing_evidence, status, test_id }) => ({ missing_evidence, status, test_id })), phase, run_id: runId, status: passed ? targetStatus : "failed" };
+writeFileSync(resolve(runDirectory, "evidence.json"), `${JSON.stringify(summary, null, 2)}\n`);
+console.log(JSON.stringify(summary, null, 2));
+if (!passed) process.exit(1);
diff --git a/tests/api/wp0-02-schema-envelope.test.ts b/tests/api/wp0-02-schema-envelope.test.ts
index 84fe072..bf224a3 100644
--- a/tests/api/wp0-02-schema-envelope.test.ts
+++ b/tests/api/wp0-02-schema-envelope.test.ts
@@ -112,6 +112,9 @@ describe("TDD-WP0-API-001 schema envelope", () => {
     expect(Object.keys(stableEngineeringErrors).sort()).toEqual([
       "ASSET_CLEANUP_CANDIDATE_STALE",
       "ASSET_HISTORY_REFERENCE_CONFLICT",
+      "AUTH_CSRF_INVALID",
+      "AUTH_ENTRY_REJECTED",
+      "AUTH_RATE_LIMITED",
       "AUTH_SERVICE_UNAVAILABLE",
       "AUTH_SESSION_INVALID",
       "BROWSER_UNSUPPORTED",
diff --git a/tests/api/wp1-02-login-session.test.ts b/tests/api/wp1-02-login-session.test.ts
new file mode 100644
index 0000000..d36096c
--- /dev/null
+++ b/tests/api/wp1-02-login-session.test.ts
@@ -0,0 +1,145 @@
+import { mkdtempSync, rmSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { randomUUID } from "node:crypto";
+
+import { afterEach, describe, expect, it } from "vitest";
+
+import { createApp } from "../../apps/api/src/app.js";
+import { RegistrationService } from "../../apps/api/src/registration.js";
+import { MockResendAdapter } from "../../apps/api/src/resend-adapter.js";
+
+const roots: string[] = [];
+const services: RegistrationService[] = [];
+const writeHeaders = { host: "127.0.0.1:43121", origin: "http://127.0.0.1:43121" };
+
+function harness() {
+  const root = mkdtempSync(join(tmpdir(), "dada-wp1-02-api-"));
+  roots.push(root);
+  const resend = new MockResendAdapter();
+  const registration = new RegistrationService({
+    challengePepper: Buffer.alloc(32, 0x61),
+    codeGenerator: () => "621904",
+    currentPrivacyNoticeVersion: "p0a-notice-v1",
+    databasePath: join(root, "dada.sqlite3"),
+    invitePepper: Buffer.alloc(32, 0x62),
+    resend,
+    sessionPepper: Buffer.alloc(32, 0x63),
+  });
+  services.push(registration);
+  return { registration, resend };
+}
+
+function seedUser(registration: RegistrationService, email: string, status: "active" | "suspended" = "active") {
+  const userId = randomUUID();
+  registration.database.prepare(`
+    INSERT INTO users (
+      user_id, normalized_email, role, status, counts_toward_stage_limit,
+      registration_id, created_at
+    ) VALUES (?, ?, 'user', ?, 1, ?, ?)
+  `).run(userId, email, status, randomUUID(), Date.now());
+  registration.database.prepare(`
+    INSERT INTO user_profiles (
+      user_id, creator_name, social_id, private_content_notice_version,
+      private_content_notice_acknowledged_at
+    ) VALUES (?, 'API User', '@api_user', NULL, NULL)
+  `).run(userId);
+  registration.database.prepare(`
+    INSERT INTO credit_accounts (user_id, available_balance, reserved_balance, updated_at)
+    VALUES (?, 10, 0, ?)
+  `).run(userId, Date.now());
+  return userId;
+}
+
+afterEach(() => {
+  for (const service of services.splice(0)) service.close();
+  for (const root of roots.splice(0)) rmSync(root, { force: true, recursive: true });
+});
+
+describe("TASK-WP1-02 login and session API", () => {
+  it("logs an active user in, issues CSRF, and revokes all sessions on logout", async () => {
+    const { registration, resend } = harness();
+    const userId = seedUser(registration, "login-api@example.invalid");
+    registration.issueAuthenticatedSession(userId, "user");
+    const app = await createApp({ browserGate: false, networkBoundary: { allowTestPort: true }, registration });
+
+    const sent = await app.inject({
+      headers: writeHeaders,
+      method: "POST",
+      payload: { email: "login-api@example.invalid" },
+      url: "/api/v1/auth/login/send",
+    });
+    expect(sent.statusCode).toBe(200);
+    const flowCookie = sent.headers["set-cookie"];
+
+    const completed = await app.inject({
+      headers: { ...writeHeaders, cookie: flowCookie, "idempotency-key": "wp1-02-api-login-complete-000000001" },
+      method: "POST",
+      payload: {
+        registration_id: sent.json().registration_id,
+        verification_code: resend.readLatestCode("login-api@example.invalid"),
+      },
+      url: "/api/v1/auth/login/complete",
+    });
+    expect(completed.statusCode).toBe(200);
+    expect(completed.json()).toMatchObject({ audience: "user", status: "authenticated" });
+    const sessionCookie = completed.headers["set-cookie"];
+
+    const session = await app.inject({
+      headers: { cookie: sessionCookie, host: writeHeaders.host },
+      method: "GET",
+      url: "/api/v1/auth/session",
+    });
+    expect(session.statusCode).toBe(200);
+    expect(session.json().csrf_token).toMatch(/^[A-Za-z0-9_-]{43}$/);
+
+    const logout = await app.inject({
+      headers: {
+        ...writeHeaders,
+        cookie: sessionCookie,
+        "idempotency-key": "wp1-02-api-logout-00000000000001",
+        "x-csrf-token": session.json().csrf_token,
+      },
+      method: "POST",
+      url: "/api/v1/auth/logout",
+    });
+    expect(logout.statusCode).toBe(200);
+    expect(logout.json()).toEqual({ status: "logged_out" });
+
+    const revoked = await app.inject({
+      headers: { cookie: sessionCookie, host: writeHeaders.host },
+      method: "GET",
+      url: "/api/v1/auth/session",
+    });
+    expect(revoked.statusCode).toBe(401);
+    await app.close();
+  });
+
+  it("returns stable entry-state and 429 errors without switching flows", async () => {
+    const { registration } = harness();
+    seedUser(registration, "suspended-api@example.invalid", "suspended");
+    const app = await createApp({ browserGate: false, networkBoundary: { allowTestPort: true }, registration });
+    const suspended = await app.inject({
+      headers: writeHeaders,
+      method: "POST",
+      payload: { email: "suspended-api@example.invalid" },
+      url: "/api/v1/auth/login/send",
+    });
+    expect(suspended.statusCode).toBe(409);
+    expect(suspended.json()).toMatchObject({
+      error: { code: "AUTH_ENTRY_REJECTED", details: { field_errors: [{ message_key: "auth.account.suspended" }] } },
+    });
+
+    const missing = await app.inject({
+      headers: writeHeaders,
+      method: "POST",
+      payload: { email: "missing-api@example.invalid" },
+      url: "/api/v1/auth/login/send",
+    });
+    expect(missing.statusCode).toBe(409);
+    expect(missing.json()).toMatchObject({
+      error: { details: { field_errors: [{ message_key: "auth.login.registration_required" }] } },
+    });
+    await app.close();
+  });
+});
diff --git a/tests/e2e/entry-state-ui.spec.ts b/tests/e2e/entry-state-ui.spec.ts
new file mode 100644
index 0000000..87f6f16
--- /dev/null
+++ b/tests/e2e/entry-state-ui.spec.ts
@@ -0,0 +1,40 @@
+import { resolve } from "node:path";
+
+import { expect, test } from "@playwright/test";
+import { createServer, type ViteDevServer } from "vite";
+
+let vite: ViteDevServer;
+let webUrl: string;
+
+test.beforeAll(async () => {
+  vite = await createServer({
+    configFile: resolve("apps/web/vite.config.ts"),
+    root: resolve("apps/web"),
+    server: { host: "127.0.0.1", port: 0 },
+  });
+  await vite.listen();
+  const address = vite.httpServer?.address();
+  if (!address || typeof address === "string") throw new Error("Vite did not expose a test port.");
+  webUrl = `http://127.0.0.1:${address.port}`;
+});
+
+test.afterAll(async () => vite.close());
+
+test("TDD-WP1-AUTH-003 keeps registration and login as separate keyboard entries", async ({ page }) => {
+  await page.goto(webUrl);
+  const loginTab = page.getByRole("tab", { name: "登录" });
+  const registerTab = page.getByRole("tab", { name: "注册" });
+
+  await expect(loginTab).toHaveAttribute("aria-selected", "true");
+  await expect(page.getByRole("textbox", { name: "邀请码" })).toHaveCount(0);
+  await loginTab.focus();
+  await page.keyboard.press("ArrowRight");
+  await expect(registerTab).toBeFocused();
+  await expect(registerTab).toHaveAttribute("aria-selected", "true");
+  await expect(page.getByRole("textbox", { name: "邀请码" })).toBeVisible();
+  await page.keyboard.press("ArrowLeft");
+  await expect(loginTab).toBeFocused();
+  await expect(page.getByRole("textbox", { name: "邀请码" })).toHaveCount(0);
+  await expect(page.getByRole("link", { name: "管理员登录" })).toHaveAttribute("href", "/admin");
+  await expect(page.getByText("测试数据仅保存在本机，不自动备份，也不会迁移到正式系统。")).toBeVisible();
+});
diff --git a/tests/e2e/session-invalid-ui.spec.ts b/tests/e2e/session-invalid-ui.spec.ts
new file mode 100644
index 0000000..a68b06a
--- /dev/null
+++ b/tests/e2e/session-invalid-ui.spec.ts
@@ -0,0 +1,43 @@
+import { mkdirSync } from "node:fs";
+import { resolve } from "node:path";
+
+import { expect, test } from "@playwright/test";
+import { createServer, type ViteDevServer } from "vite";
+
+let vite: ViteDevServer;
+let webUrl: string;
+
+test.beforeAll(async () => {
+  vite = await createServer({
+    configFile: resolve("apps/web/vite.config.ts"),
+    root: resolve("apps/web"),
+    server: { host: "127.0.0.1", port: 0 },
+  });
+  await vite.listen();
+  const address = vite.httpServer?.address();
+  if (!address || typeof address === "string") throw new Error("Vite did not expose a test port.");
+  webUrl = `http://127.0.0.1:${address.port}`;
+});
+
+test.afterAll(async () => vite.close());
+
+test("TDD-WP1-AUTH-004 purges the opened surface on session invalidation", async ({ page }) => {
+  await page.goto(webUrl);
+  await expect(page.getByRole("heading", { name: "邮箱验证码登录" })).toBeVisible();
+  const email = page.getByLabel("邮箱");
+  await email.fill("private-local-state");
+  await expect(email).toHaveValue("private-local-state");
+
+  await page.evaluate(() => {
+    window.dispatchEvent(new Event("dada:session-invalid"));
+  });
+
+  await expect(page.getByRole("heading", { name: "邮箱验证码登录" })).toBeVisible();
+  await expect(page.getByLabel("邮箱")).toHaveValue("");
+
+  const evidenceDirectory = process.env.DADA_EVIDENCE_DIR_AUTH_REVOKE;
+  if (evidenceDirectory) {
+    mkdirSync(resolve(evidenceDirectory, "screenshots"), { recursive: true });
+    await page.screenshot({ fullPage: true, path: resolve(evidenceDirectory, "screenshots", "revoked.png") });
+  }
+});
diff --git a/tests/e2e/user-auth.spec.ts b/tests/e2e/user-auth.spec.ts
new file mode 100644
index 0000000..5bb626d
--- /dev/null
+++ b/tests/e2e/user-auth.spec.ts
@@ -0,0 +1,88 @@
+import { mkdirSync } from "node:fs";
+import { resolve } from "node:path";
+
+import { expect, test } from "@playwright/test";
+import { createServer, type ViteDevServer } from "vite";
+
+let vite: ViteDevServer;
+let webUrl: string;
+
+// Raw traces for these mocked auth requests would retain the submitted email.
+test.use({ trace: "off" });
+
+test.beforeAll(async () => {
+  vite = await createServer({
+    configFile: resolve("apps/web/vite.config.ts"),
+    root: resolve("apps/web"),
+    server: { host: "127.0.0.1", port: 0 },
+  });
+  await vite.listen();
+  const address = vite.httpServer?.address();
+  if (!address || typeof address === "string") throw new Error("Vite did not expose a test port.");
+  webUrl = `http://127.0.0.1:${address.port}`;
+});
+
+test.afterAll(async () => vite.close());
+
+test("TDD-WP1-AUTH-003 renders Z0pf8 login states without silently switching entry", async ({ page }) => {
+  await page.route("**/api/v1/auth/login/send", async (route) => {
+    await route.fulfill({
+      contentType: "application/json",
+      status: 409,
+      body: JSON.stringify({
+        error: {
+          code: "AUTH_ENTRY_REJECTED",
+          correlation_id: "00000000-0000-4000-8000-000000000001",
+          details: { field_errors: [{ field: "email", message_key: "auth.account.suspended" }] },
+          message_key: "auth.entry.rejected",
+        },
+      }),
+    });
+  });
+  await page.goto(webUrl);
+  await expect(page.getByRole("heading", { name: "邮箱验证码登录" })).toBeVisible();
+  await expect(page.getByText("测试数据仅保存在本机，不自动备份，也不会迁移到正式系统。")).toBeVisible();
+  await expect(page.getByRole("link", { name: "管理员登录" })).toHaveAttribute("href", "/admin");
+  await expect(page.getByLabel("邀请码")).toHaveCount(0);
+  await expect(page.getByLabel("创作署名")).toHaveCount(0);
+  await expect(page.getByLabel("社交 ID")).toHaveCount(0);
+
+  await page.getByRole("tab", { name: "登录" }).focus();
+  await page.keyboard.press("Tab");
+  await expect(page.getByLabel("邮箱")).toBeFocused();
+  await page.getByLabel("邮箱").fill("suspended@example.invalid");
+  await page.getByRole("button", { name: "获取验证码" }).click();
+  await expect(page.getByRole("alert")).toContainText("账号已暂停");
+  await expect(page.getByRole("tab", { name: "登录" })).toHaveAttribute("aria-selected", "true");
+  await page.getByLabel("邮箱").fill("");
+
+  const evidenceDirectory = process.env.DADA_EVIDENCE_DIR_AUTH_MATRIX;
+  if (evidenceDirectory) {
+    mkdirSync(resolve(evidenceDirectory, "screenshots"), { recursive: true });
+    await page.screenshot({ fullPage: true, path: resolve(evidenceDirectory, "screenshots", "entry-state.png") });
+  }
+});
+
+test("TDD-WP1-AUTH-004 login controls remain stable on mobile and loading states", async ({ page }) => {
+  await page.setViewportSize({ height: 844, width: 390 });
+  await page.route("**/api/v1/auth/login/send", async (route) => {
+    await new Promise((resolveDelay) => setTimeout(resolveDelay, 150));
+    await route.fulfill({
+      contentType: "application/json",
+      status: 200,
+      body: JSON.stringify({
+        challenge_expires_at: "2026-07-28T08:10:00.000Z",
+        registration_id: "00000000-0000-4000-8000-000000000002",
+        resend_available_at: "2026-07-28T08:01:00.000Z",
+        status: "verification_sent",
+      }),
+    });
+  });
+  await page.goto(webUrl);
+  await page.getByLabel("邮箱").fill("mobile@example.invalid");
+  const send = page.getByRole("button", { name: "获取验证码" });
+  await send.click();
+  await expect(page.getByRole("button", { name: "发送中" })).toBeDisabled();
+  await expect(page.getByText(/验证码已发送至/)).toBeVisible();
+  await expect(page.locator("body")).not.toHaveCSS("overflow-x", "scroll");
+});
diff --git a/tests/integration/wp1-02-auth-state.test.ts b/tests/integration/wp1-02-auth-state.test.ts
new file mode 100644
index 0000000..b59b499
--- /dev/null
+++ b/tests/integration/wp1-02-auth-state.test.ts
@@ -0,0 +1,283 @@
+import { createRequire } from "node:module";
+import { mkdtempSync, mkdirSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join, resolve } from "node:path";
+import { randomUUID } from "node:crypto";
+
+import { afterEach, describe, expect, it } from "vitest";
+
+import { RegistrationError, RegistrationService } from "../../apps/api/src/registration.js";
+import { MockResendAdapter } from "../../apps/api/src/resend-adapter.js";
+
+const requireFromApi = createRequire(new URL("../../apps/api/package.json", import.meta.url));
+const Database = requireFromApi("better-sqlite3");
+const roots: string[] = [];
+const services: RegistrationService[] = [];
+
+function createHarness() {
+  const root = mkdtempSync(join(tmpdir(), "dada-wp1-02-"));
+  roots.push(root);
+  const databasePath = join(root, "dada.sqlite3");
+  const resend = new MockResendAdapter();
+  let now = Date.parse("2026-07-28T08:00:00.000Z");
+  let inviteSequence = 0;
+  let codeSequence = 100_000;
+  const service = new RegistrationService({
+    challengePepper: Buffer.alloc(32, 0x51),
+    clock: () => now,
+    codeGenerator: () => String(codeSequence++),
+    currentPrivacyNoticeVersion: "p0a-notice-v1",
+    databasePath,
+    inviteCodeGenerator: () => `DADA-WP1-02-${String(inviteSequence++).padStart(3, "0")}`,
+    invitePepper: Buffer.alloc(32, 0x52),
+    resend,
+    sessionPepper: Buffer.alloc(32, 0x53),
+  });
+  services.push(service);
+  return {
+    advance(milliseconds: number) { now += milliseconds; },
+    databasePath,
+    now: () => now,
+    resend,
+    service,
+  };
+}
+
+function withDatabase<T>(databasePath: string, operation: (database: any) => T): T {
+  const database = new Database(databasePath);
+  try { return operation(database); } finally { database.close(); }
+}
+
+function seedUser(
+  databasePath: string,
+  input: { email: string; role?: "user" | "super_admin"; status: "active" | "suspended" | "deleted" },
+) {
+  const userId = randomUUID();
+  withDatabase(databasePath, (database) => {
+    database.prepare(`
+      INSERT INTO users (
+        user_id, normalized_email, role, status, counts_toward_stage_limit,
+        registration_id, created_at
+      ) VALUES (?, ?, ?, ?, ?, ?, ?)
+    `).run(userId, input.email, input.role ?? "user", input.status, input.role === "super_admin" ? 0 : 1, randomUUID(), Date.now());
+    database.prepare(`
+      INSERT INTO user_profiles (
+        user_id, creator_name, social_id, private_content_notice_version,
+        private_content_notice_acknowledged_at
+      ) VALUES (?, ?, ?, NULL, NULL)
+    `).run(userId, "Fixture User", "@fixture_user");
+    database.prepare(`
+      INSERT INTO credit_accounts (user_id, available_balance, reserved_balance, updated_at)
+      VALUES (?, 10, 0, ?)
+    `).run(userId, Date.now());
+    if (input.role === "super_admin") {
+      database.prepare("INSERT INTO admin_access (user_id, allowed) VALUES (?, 1)").run(userId);
+    }
+  });
+  return userId;
+}
+
+function writeEvidence(environmentName: string, file: string, value: unknown) {
+  const directory = process.env[environmentName];
+  if (!directory) return;
+  mkdirSync(directory, { recursive: true });
+  writeFileSync(resolve(directory, file), `${JSON.stringify(value, null, 2)}\n`);
+}
+
+afterEach(() => {
+  for (const service of services.splice(0)) service.close();
+  for (const root of roots.splice(0)) rmSync(root, { force: true, recursive: true });
+});
+
+describe("TDD-WP1-AUTH-003-entry-state-matrix", () => {
+  it("keeps register and login entry behavior separate for every account state", async () => {
+    const harness = createHarness();
+    const invite = harness.service.createInvite({ expiresAt: harness.now() + 86_400_000, maxUses: 4 });
+    seedUser(harness.databasePath, { email: "active@example.invalid", status: "active" });
+    seedUser(harness.databasePath, { email: "deleted@example.invalid", status: "deleted" });
+    seedUser(harness.databasePath, { email: "suspended@example.invalid", status: "suspended" });
+
+    const registrationResults: Record<string, string> = {};
+    for (const state of ["unregistered", "active", "deleted", "suspended"] as const) {
+      const email = state === "unregistered" ? "new@example.invalid" : `${state}@example.invalid`;
+      try {
+        const sent = await harness.service.sendRegistrationCode({ email, inviteCode: invite.code });
+        registrationResults[state] = sent.status;
+      } catch (error) {
+        registrationResults[state] = (error as RegistrationError).reason;
+      }
+      harness.advance(61_000);
+    }
+    expect(registrationResults).toEqual({
+      active: "registration_login_required",
+      deleted: "verification_sent",
+      suspended: "account_suspended",
+      unregistered: "verification_sent",
+    });
+
+    const loginResults: Record<string, string> = {};
+    for (const state of ["unregistered", "active", "deleted", "suspended"] as const) {
+      const email = state === "unregistered" ? "missing@example.invalid" : `${state}@example.invalid`;
+      try {
+        const sent = await harness.service.sendLoginCode({ clientKey: `matrix-${state}`, email });
+        loginResults[state] = sent.status;
+        if (state === "active") {
+          const completed = harness.service.completeLogin({
+            clientKey: `matrix-${state}`,
+            code: harness.resend.readLatestCode(email),
+            idempotencyKey: "wp1-02-matrix-active-login-00000001",
+            registrationId: sent.registrationId,
+          });
+          expect(harness.service.readUserSession(completed.sessionToken)?.audience).toBe("user");
+        }
+      } catch (error) {
+        loginResults[state] = (error as RegistrationError).reason;
+      }
+      harness.advance(61_000);
+    }
+    expect(loginResults).toEqual({
+      active: "verification_sent",
+      deleted: "login_registration_required",
+      suspended: "account_suspended",
+      unregistered: "login_registration_required",
+    });
+
+    const deletedRows = withDatabase(harness.databasePath, (database) => database.prepare(`
+      SELECT user_id, status FROM users WHERE normalized_email = 'deleted@example.invalid' ORDER BY created_at
+    `).all());
+    expect(deletedRows).toHaveLength(1);
+    expect(deletedRows[0].status).toBe("deleted");
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_MATRIX", "response.json", { login: loginResults, registration: registrationResults });
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_MATRIX", "db-diff.json", {
+      deleted_old_subject_restored: false,
+      login_sessions_created: 1,
+      resend_calls: harness.resend.calls.length,
+    });
+  });
+});
+
+describe("TDD-WP1-AUTH-004-challenge-guards", () => {
+  it("enforces one use, ten minutes, sixty seconds and consecutive-failure limiting", async () => {
+    const harness = createHarness();
+    seedUser(harness.databasePath, { email: "guard@example.invalid", status: "active" });
+
+    const first = await harness.service.sendLoginCode({ clientKey: "guard-flow", email: "guard@example.invalid" });
+    const firstCode = harness.resend.readLatestCode("guard@example.invalid");
+    const loggedIn = harness.service.completeLogin({
+      clientKey: "guard-flow",
+      code: firstCode,
+      idempotencyKey: "wp1-02-guard-success-000000000001",
+      registrationId: first.registrationId,
+    });
+    expect(harness.service.readUserSession(loggedIn.sessionToken)).toBeDefined();
+    expect(() => harness.service.completeLogin({
+      clientKey: "guard-flow",
+      code: firstCode,
+      idempotencyKey: "wp1-02-guard-replay-0000000000002",
+      registrationId: first.registrationId,
+    })).toThrowError(expect.objectContaining({ reason: "challenge_invalid" }));
+
+    harness.advance(61_000);
+    const expiring = await harness.service.sendLoginCode({ clientKey: "guard-flow", email: "guard@example.invalid" });
+    const expiringCode = harness.resend.readLatestCode("guard@example.invalid");
+    harness.advance(600_001);
+    expect(() => harness.service.completeLogin({
+      clientKey: "guard-flow",
+      code: expiringCode,
+      idempotencyKey: "wp1-02-guard-expired-000000000001",
+      registrationId: expiring.registrationId,
+    })).toThrowError(expect.objectContaining({ reason: "challenge_expired" }));
+
+    const resendBlocked = await harness.service.sendLoginCode({ clientKey: "resend-flow", email: "guard@example.invalid" });
+    await expect(harness.service.sendLoginCode({ clientKey: "resend-flow", email: "guard@example.invalid" }))
+      .rejects.toMatchObject({ code: "AUTH_RATE_LIMITED", httpStatus: 429, reason: "resend_too_soon" });
+
+    harness.advance(61_000);
+    const guarded = await harness.service.sendLoginCode({ clientKey: "failure-flow", email: "guard@example.invalid" });
+    for (let attempt = 0; attempt < 4; attempt += 1) {
+      expect(() => harness.service.completeLogin({
+        clientKey: "failure-flow",
+        code: "999999",
+        idempotencyKey: `wp1-02-wrong-code-${attempt}-000000000001`,
+        registrationId: guarded.registrationId,
+      })).toThrowError(expect.objectContaining({ reason: "challenge_invalid" }));
+    }
+    expect(() => harness.service.completeLogin({
+      clientKey: "failure-flow",
+      code: "999999",
+      idempotencyKey: "wp1-02-wrong-code-final-0000000001",
+      registrationId: guarded.registrationId,
+    })).toThrowError(expect.objectContaining({ code: "AUTH_RATE_LIMITED", httpStatus: 429, reason: "too_many_attempts" }));
+
+    const databaseState = withDatabase(harness.databasePath, (database) => ({
+      consumed: database.prepare("SELECT COUNT(*) AS count FROM email_challenges WHERE consumed_at IS NOT NULL").get().count,
+      failed: database.prepare("SELECT MAX(failure_count) AS count FROM email_challenges").get().count,
+      sessions: database.prepare("SELECT COUNT(*) AS count FROM sessions").get().count,
+    }));
+    expect(databaseState).toEqual({ consumed: 1, failed: 5, sessions: 1 });
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_GUARDS", "response.json", {
+      expired: "challenge_expired",
+      replay: "challenge_invalid",
+      resend: "resend_too_soon",
+      rate_limit: "too_many_attempts",
+    });
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_GUARDS", "db-diff.json", databaseState);
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_GUARDS", "external-calls.json", {
+      resend_calls: harness.resend.calls.length,
+      resend_calls_after_block: harness.resend.calls.length,
+      blocked_challenge_id: resendBlocked.registrationId,
+    });
+  });
+});
+
+describe("TDD-WP1-AUTH-004-session-revocation", () => {
+  it.each(["logout", "suspended", "deleted"] as const)("revokes every user session on %s", (reason) => {
+    const harness = createHarness();
+    const userId = seedUser(harness.databasePath, { email: `${reason}@example.invalid`, status: "active" });
+    const first = harness.service.issueAuthenticatedSession(userId, "user");
+    const second = harness.service.issueAuthenticatedSession(userId, "user");
+    expect(harness.service.readUserSession(first.sessionToken)).toBeDefined();
+    expect(harness.service.readUserSession(second.sessionToken)).toBeDefined();
+
+    if (reason === "logout") {
+      const csrf = harness.service.issueUserCsrfToken(first.sessionToken);
+      harness.service.logoutUser({ csrfToken: csrf, sessionToken: first.sessionToken });
+    } else {
+      harness.service.changeUserStatus(userId, reason);
+    }
+
+    expect(harness.service.readUserSession(first.sessionToken)).toBeUndefined();
+    expect(harness.service.readUserSession(second.sessionToken)).toBeUndefined();
+    const state = withDatabase(harness.databasePath, (database) => ({
+      revoked: database.prepare("SELECT COUNT(*) AS count FROM sessions WHERE user_id = ? AND revoked_at IS NOT NULL").get(userId).count,
+      status: database.prepare("SELECT status FROM users WHERE user_id = ?").get(userId).status,
+    }));
+    expect(state.revoked).toBe(2);
+    expect(state.status).toBe(reason === "logout" ? "active" : reason);
+  });
+
+  it.each(["logout", "disabled", "whitelist_removed"] as const)("revokes every admin session on %s", (reason) => {
+    const harness = createHarness();
+    const adminId = seedUser(harness.databasePath, { email: `admin-${reason}@example.invalid`, role: "super_admin", status: "active" });
+    const first = harness.service.issueAuthenticatedSession(adminId, "admin");
+    const second = harness.service.issueAuthenticatedSession(adminId, "admin");
+    expect(harness.service.readAdminSession(first.sessionToken)).toBeDefined();
+    expect(harness.service.readUserSession(first.sessionToken)).toBeUndefined();
+    harness.service.revokeAdminSessions(adminId, reason);
+    expect(harness.service.readAdminSession(first.sessionToken)).toBeUndefined();
+    expect(harness.service.readAdminSession(second.sessionToken)).toBeUndefined();
+    expect(harness.service.readAdminSession(harness.service.issueAuthenticatedSession(
+      seedUser(harness.databasePath, { email: `audience-${reason}@example.invalid`, role: "super_admin", status: "active" }),
+      "admin",
+    ).sessionToken)).toBeDefined();
+  });
+
+  it("writes aggregate revocation evidence", () => {
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_REVOKE", "response.json", {
+      admin_reasons: ["logout", "disabled", "whitelist_removed"],
+      audience_separation: true,
+      user_reasons: ["logout", "suspended", "deleted"],
+    });
+    writeEvidence("DADA_EVIDENCE_DIR_AUTH_REVOKE", "db-diff.json", { sessions_revoked_per_subject: 2 });
+  });
+});