diff --git a/backend/alembic/versions/d4e5f6a7b8c9_add_logto_user_fields.py b/backend/alembic/versions/d4e5f6a7b8c9_add_logto_user_fields.py
new file mode 100644
index 0000000..6438154
--- /dev/null
+++ b/backend/alembic/versions/d4e5f6a7b8c9_add_logto_user_fields.py
@@ -0,0 +1,87 @@
+"""Add Logto fields to users table.
+
+Adds the columns required for Logto OIDC integration and general user-profile
+enhancements:
+
+- ``logto_id``      – the Logto subject claim (``sub``); acts as the stable
+                      external identity reference.
+- ``username``      – optional display username synced from Logto.
+- ``picture``       – profile-picture URL synced from Logto.
+- ``created_at``    – row-creation timestamp.
+- ``updated_at``    – last-update timestamp.
+
+``hashed_password`` is made nullable because Logto-authenticated users
+authenticate externally and have no local password.
+
+Revision ID: d4e5f6a7b8c9
+Revises: c3d4e5f6a7b8
+Create Date: 2026-03-30 10:00:00.000000
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+
+# revision identifiers, used by Alembic.
+revision: str = "d4e5f6a7b8c9"
+down_revision: Union[str, Sequence[str], None] = "c3d4e5f6a7b8"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    """Apply schema changes."""
+    with op.batch_alter_table("users") as batch_op:
+        # New columns
+        batch_op.add_column(
+            sa.Column("logto_id", sa.String(), nullable=True)
+        )
+        batch_op.add_column(
+            sa.Column("username", sa.String(), nullable=True)
+        )
+        batch_op.add_column(
+            sa.Column("picture", sa.String(), nullable=True)
+        )
+        batch_op.add_column(
+            sa.Column(
+                "created_at",
+                sa.DateTime(),
+                nullable=True,
+                server_default=sa.func.now(),
+            )
+        )
+        batch_op.add_column(
+            sa.Column(
+                "updated_at",
+                sa.DateTime(),
+                nullable=True,
+                server_default=sa.func.now(),
+            )
+        )
+        # Make hashed_password nullable (Logto users have no local password)
+        batch_op.alter_column("hashed_password", nullable=True)
+        # Set is_superuser default to True (all users are admins for now)
+        batch_op.alter_column("is_superuser", server_default=sa.true())
+
+    # Add unique index on logto_id
+    op.create_index(
+        op.f("ix_users_logto_id"),
+        "users",
+        ["logto_id"],
+        unique=True,
+    )
+
+
+def downgrade() -> None:
+    """Revert schema changes."""
+    op.drop_index(op.f("ix_users_logto_id"), table_name="users")
+
+    with op.batch_alter_table("users") as batch_op:
+        batch_op.drop_column("updated_at")
+        batch_op.drop_column("created_at")
+        batch_op.drop_column("picture")
+        batch_op.drop_column("username")
+        batch_op.drop_column("logto_id")
+        batch_op.alter_column("hashed_password", nullable=False)
+        batch_op.alter_column("is_superuser", server_default=sa.false())
diff --git a/backend/app/api/api_v1/api.py b/backend/app/api/api_v1/api.py
index 4a8978e..51512d3 100644
--- a/backend/app/api/api_v1/api.py
+++ b/backend/app/api/api_v1/api.py
@@ -1,6 +1,7 @@
 from fastapi import APIRouter
 
 from app.api.api_v1.endpoints import (
+    auth,
     domains,
     health,
     imap,
@@ -14,6 +15,7 @@ from app.api.api_v1.endpoints import (
 api_router = APIRouter()
 
 # Include all endpoint routers
+api_router.include_router(auth.router, prefix="/auth", tags=["auth"])
 api_router.include_router(health.router, tags=["health"])
 api_router.include_router(domains.router, prefix="/domains", tags=["domains"])
 api_router.include_router(reports.router, prefix="/reports", tags=["reports"])
diff --git a/backend/app/api/api_v1/endpoints/auth.py b/backend/app/api/api_v1/endpoints/auth.py
new file mode 100644
index 0000000..2bc2a1b
--- /dev/null
+++ b/backend/app/api/api_v1/endpoints/auth.py
@@ -0,0 +1,237 @@
+"""
+Authentication endpoints (Logto OIDC).
+
+Routes
+------
+GET  /sign-in         – Initiate the Logto sign-in flow.
+GET  /callback        – Handle the Logto authorization-code callback.
+GET  /sign-out        – Sign the user out (clears session + redirects to Logto).
+GET  /me              – Return the currently authenticated user's profile.
+"""
+
+from __future__ import annotations
+
+import logging
+from typing import Any, Dict, Optional
+
+from fastapi import APIRouter, Depends, HTTPException, Request, status
+from fastapi.responses import RedirectResponse
+from sqlalchemy.orm import Session
+
+from app.core.config import get_settings
+from app.core.database import get_db
+from app.core.logto import (
+    SESSION_COOKIE,
+    CookieStorage,
+    create_session_token,
+    decode_session_token,
+    make_logto_client,
+    sync_logto_user,
+)
+from app.models.user import User
+
+router = APIRouter()
+logger = logging.getLogger(__name__)
+settings = get_settings()
+
+# ── Helpers ───────────────────────────────────────────────────────────────────
+
+_SAFE_NEXT_PREFIXES = ("/",)  # only allow relative redirects after login
+
+
+def _safe_next(next_url: Optional[str]) -> str:
+    """Validate and return a safe post-login redirect path."""
+    if next_url and next_url.startswith("/") and not next_url.startswith("//"):
+        return next_url
+    return "/"
+
+
+def _logto_not_configured() -> HTTPException:
+    return HTTPException(
+        status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
+        detail=(
+            "Logto is not configured. "
+            "Set LOGTO_ENDPOINT, LOGTO_APP_ID, and LOGTO_APP_SECRET "
+            "in your environment."
+        ),
+    )
+
+
+def _get_redirect_uri(request: Request) -> str:
+    """Build the callback redirect URI, preferring the configured override."""
+    if settings.LOGTO_REDIRECT_URI:
+        return settings.LOGTO_REDIRECT_URI
+    base = str(request.base_url).rstrip("/")
+    return f"{base}/api/v1/auth/callback"
+
+
+# ── Endpoints ─────────────────────────────────────────────────────────────────
+
+
+@router.get("/sign-in")
+async def sign_in(
+    request: Request,
+    next: Optional[str] = None,
+) -> RedirectResponse:
+    """
+    Initiate the Logto OIDC sign-in flow.
+
+    Stores the PKCE sign-in session in a short-lived cookie and redirects the
+    browser to Logto's authorization endpoint.  The optional ``next`` query
+    parameter is persisted in a separate cookie and used to redirect the user
+    to their original page after a successful login.
+    """
+    if not settings.logto_configured:
+        raise _logto_not_configured()
+
+    storage = CookieStorage(request)
+    client = make_logto_client(storage)
+
+    sign_in_url: str = await client.signIn(redirectUri=_get_redirect_uri(request))
+
+    response = RedirectResponse(url=sign_in_url, status_code=302)
+    storage.apply_to_response(response)
+
+    # Persist the post-login destination so the callback can redirect there.
+    safe = _safe_next(next)
+    if safe != "/":
+        response.set_cookie(
+            key="logto_next",
+            value=safe,
+            httponly=True,
+            samesite="lax",
+            max_age=600,  # 10 minutes – must survive the Logto redirect round-trip
+        )
+
+    return response
+
+
+@router.get("/callback")
+async def callback(
+    request: Request,
+    db: Session = Depends(get_db),
+) -> RedirectResponse:
+    """
+    Handle the Logto authorization-code callback.
+
+    Exchanges the code for tokens, validates the ID token, upserts the local
+    user shadow record, issues the app-level session cookie, and clears the
+    temporary Logto cookies.
+    """
+    if not settings.logto_configured:
+        raise _logto_not_configured()
+
+    storage = CookieStorage(request)
+    client = make_logto_client(storage)
+
+    try:
+        await client.handleSignInCallback(str(request.url))
+    except Exception as exc:  # pylint: disable=broad-exception-caught
+        logger.warning("Logto callback error: %s", exc)
+        return RedirectResponse(url="/login?error=callback_failed", status_code=302)
+
+    try:
+        claims = await client.getIdTokenClaims()
+    except Exception as exc:  # pylint: disable=broad-exception-caught
+        logger.warning("Failed to extract ID-token claims: %s", exc)
+        return RedirectResponse(url="/login?error=token_error", status_code=302)
+
+    user = sync_logto_user(claims, db)
+
+    # Where to go after login
+    next_url = _safe_next(request.cookies.get("logto_next"))
+
+    response = RedirectResponse(url=next_url, status_code=302)
+
+    # Issue our own session cookie (independent of Logto from here on)
+    session_token = create_session_token(user.id)
+    response.set_cookie(
+        key=SESSION_COOKIE,
+        value=session_token,
+        httponly=True,
+        samesite="lax",
+        max_age=86_400,  # 24 hours
+    )
+
+    # Clean up all temporary Logto & next cookies
+    storage.clear_all_logto_cookies(response)
+    response.delete_cookie(key="logto_next", httponly=True, samesite="lax")
+
+    logger.info("User id=%d logged in via Logto.", user.id)
+    return response
+
+
+@router.get("/sign-out")
+async def sign_out(request: Request) -> RedirectResponse:
+    """
+    Sign the user out.
+
+    Clears the app session cookie and redirects to Logto's end-session
+    endpoint (if available) so that the Logto session is terminated too.
+    """
+    post_logout_url = str(request.base_url).rstrip("/")
+
+    # Best-effort: obtain Logto's end-session URL from OIDC metadata.
+    end_session_url: Optional[str] = None
+    if settings.logto_configured:
+        try:
+            storage = CookieStorage(request)
+            client = make_logto_client(storage)
+            core = await client.getOidcCore()
+            end_session_url = getattr(core.metadata, "end_session_endpoint", None)
+        except Exception:  # pylint: disable=broad-exception-caught
+            pass
+
+    if end_session_url:
+        redirect_to = f"{end_session_url}?post_logout_redirect_uri={post_logout_url}"
+    else:
+        redirect_to = "/login"
+
+    response = RedirectResponse(url=redirect_to, status_code=302)
+    response.delete_cookie(key=SESSION_COOKIE, httponly=True, samesite="lax")
+    return response
+
+
+@router.get("/me", response_model=None)
+async def get_current_user(
+    request: Request,
+    db: Session = Depends(get_db),
+) -> Dict[str, Any]:
+    """
+    Return the profile of the currently authenticated user.
+
+    Reads the ``dmarq_session`` cookie (issued at callback time) and looks up
+    the corresponding local ``User`` record.
+    """
+    token = request.cookies.get(SESSION_COOKIE)
+    if not token:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Not authenticated",
+        )
+
+    user_id = decode_session_token(token)
+    if user_id is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid or expired session",
+        )
+
+    user: Optional[User] = (
+        db.query(User).filter(User.id == user_id, User.is_active == True).first()  # noqa: E712
+    )
+    if user is None:
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="User not found or inactive",
+        )
+
+    return {
+        "id": user.id,
+        "email": user.email,
+        "full_name": user.full_name,
+        "username": user.username,
+        "picture": user.picture,
+        "is_superuser": user.is_superuser,
+        "logto_id": user.logto_id,
+    }
diff --git a/backend/app/core/config.py b/backend/app/core/config.py
index 73341d3..b6439ba 100644
--- a/backend/app/core/config.py
+++ b/backend/app/core/config.py
@@ -54,9 +54,29 @@ class Settings(BaseSettings):
     # Use: openssl rand -hex 32
     ADMIN_API_KEY: Optional[str] = None
 
+    # ── Logto OIDC ────────────────────────────────────────────────────────────
+    # Set these to enable Logto-based authentication.
+    # LOGTO_ENDPOINT:    the base URL of your Logto instance,
+    #                    e.g. "https://your-tenant.logto.app" or a self-hosted URL.
+    # LOGTO_APP_ID:      the Client ID of the "Traditional Web" application in Logto.
+    # LOGTO_APP_SECRET:  the Client Secret of the same application.
+    # LOGTO_REDIRECT_URI (optional): override the default callback URL.
+    #                    Defaults to <base_url>/api/v1/auth/callback.
+    LOGTO_ENDPOINT: Optional[str] = None
+    LOGTO_APP_ID: Optional[str] = None
+    LOGTO_APP_SECRET: Optional[str] = None
+    LOGTO_REDIRECT_URI: Optional[str] = None
+
+    @property
+    def logto_configured(self) -> bool:
+        """Return True when the minimum Logto settings are present."""
+        return bool(self.LOGTO_ENDPOINT and self.LOGTO_APP_ID and self.LOGTO_APP_SECRET)
+
     @validator("ADMIN_API_KEY", pre=True, always=True)
     @classmethod
-    def validate_admin_api_key(cls, v: Optional[str]) -> Optional[str]:  # pylint: disable=no-self-argument
+    def validate_admin_api_key(
+        cls, v: Optional[str]
+    ) -> Optional[str]:  # pylint: disable=no-self-argument
         """Warn if ADMIN_API_KEY is set but too short."""
         if v is not None and len(v) < 32:
             logger.warning(
diff --git a/backend/app/core/database.py b/backend/app/core/database.py
index 1fd824e..9be825a 100644
--- a/backend/app/core/database.py
+++ b/backend/app/core/database.py
@@ -1,10 +1,9 @@
 import os
-from typing import AsyncGenerator, Generator
+from typing import Generator
 from urllib.parse import urlparse, urlunparse
 
 from sqlalchemy import create_engine
 from sqlalchemy.engine import make_url
-from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker, create_async_engine
 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy.orm import sessionmaker
 
diff --git a/backend/app/core/logto.py b/backend/app/core/logto.py
new file mode 100644
index 0000000..3112116
--- /dev/null
+++ b/backend/app/core/logto.py
@@ -0,0 +1,218 @@
+"""
+Logto OIDC integration helpers.
+
+Provides:
+- ``CookieStorage``       – Logto SDK Storage adapter backed by HTTP cookies.
+- ``make_logto_client``   – Factory that builds a per-request LogtoClient.
+- ``create_session_token``/``decode_session_token`` – thin JWT helpers for the
+  app-level session cookie (independent of Logto after the initial callback).
+- ``sync_logto_user``     – Upserts the local User shadow record from Logto claims.
+"""
+
+from __future__ import annotations
+
+import logging
+from datetime import datetime, timedelta
+from typing import Optional
+
+from fastapi import Request, Response
+from jose import JWTError, jwt
+from logto import IdTokenClaims, LogtoClient, LogtoConfig, PersistKey, Scope, Storage, UserInfoScope
+from sqlalchemy.orm import Session
+
+from app.core.config import get_settings
+from app.models.user import User
+
+logger = logging.getLogger(__name__)
+settings = get_settings()
+
+# ── Constants ────────────────────────────────────────────────────────────────
+
+SESSION_COOKIE = "dmarq_session"
+
+# Short-lived: only needed while the browser is being redirected to Logto and back.
+_SIGN_IN_SESSION_MAX_AGE = 600  # 10 minutes
+# The app-level session lasts 24 hours by default; the Logto ID-token has its own
+# expiry but we don't keep it in the browser beyond the callback request.
+_SESSION_MAX_AGE = 86_400  # 24 hours
+
+
+# ── Cookie-backed Logto Storage ───────────────────────────────────────────────
+
+
+class CookieStorage(Storage):
+    """
+    Storage adapter for the Logto SDK that persists the OIDC session data
+    (sign-in session, tokens) in HTTP-only cookies.
+
+    Usage::
+
+        storage = CookieStorage(request)
+        client  = make_logto_client(storage)
+        url     = await client.signIn(redirect_uri=…)
+        # build a response, then:
+        storage.apply_to_response(response)
+        return response
+    """
+
+    _COOKIE_PREFIX = "logto_"
+
+    def __init__(self, request: Request) -> None:
+        self._request = request
+        # Pending writes/deletes – applied to the Response via apply_to_response().
+        self._writes: dict[str, Optional[str]] = {}
+        self._deletes: set[str] = set()
+
+    # ── Storage protocol ──────────────────────────────────────────────────────
+
+    def get(self, key: PersistKey) -> Optional[str]:  # type: ignore[override]
+        if key in self._writes:
+            return self._writes[key]
+        if key in self._deletes:
+            return None
+        return self._request.cookies.get(self._COOKIE_PREFIX + key)
+
+    def set(self, key: PersistKey, value: Optional[str]) -> None:  # type: ignore[override]
+        self._writes[key] = value
+        self._deletes.discard(key)
+
+    def delete(self, key: PersistKey) -> None:  # type: ignore[override]
+        self._deletes.add(key)
+        self._writes.pop(key, None)
+
+    # ── Response helper ───────────────────────────────────────────────────────
+
+    def apply_to_response(self, response: Response) -> None:
+        """Flush pending cookie mutations onto *response*."""
+        for key, value in self._writes.items():
+            if value is None:
+                continue
+            max_age = _SIGN_IN_SESSION_MAX_AGE if key == "signInSession" else _SESSION_MAX_AGE
+            response.set_cookie(
+                key=self._COOKIE_PREFIX + key,
+                value=value,
+                httponly=True,
+                samesite="lax",
+                max_age=max_age,
+            )
+        for key in self._deletes:
+            response.delete_cookie(
+                key=self._COOKIE_PREFIX + key,
+                httponly=True,
+                samesite="lax",
+            )
+
+    def clear_all_logto_cookies(self, response: Response) -> None:
+        """Remove every Logto cookie (called after we've issued our own session)."""
+        for key in ("signInSession", "idToken", "accessTokenMap", "refreshToken"):
+            response.delete_cookie(
+                key=self._COOKIE_PREFIX + key,
+                httponly=True,
+                samesite="lax",
+            )
+
+
+# ── LogtoClient factory ───────────────────────────────────────────────────────
+
+
+def make_logto_client(storage: CookieStorage) -> LogtoClient:
+    """Return a per-request ``LogtoClient`` bound to *storage*."""
+    return LogtoClient(
+        LogtoConfig(
+            endpoint=settings.LOGTO_ENDPOINT or "",
+            appId=settings.LOGTO_APP_ID or "",
+            appSecret=settings.LOGTO_APP_SECRET,
+            scopes=[
+                UserInfoScope.email,
+                UserInfoScope.profile,
+                Scope.offlineAccess,
+            ],
+        ),
+        storage=storage,
+    )
+
+
+# ── App-level session JWT (independent of Logto after first login) ────────────
+
+
+def create_session_token(user_id: int) -> str:
+    """Mint a signed HS256 JWT for *user_id* with a 24-hour lifetime."""
+    payload = {
+        "sub": str(user_id),
+        "type": "dmarq_session",
+        "exp": datetime.utcnow() + timedelta(seconds=_SESSION_MAX_AGE),
+    }
+    return jwt.encode(payload, settings.SECRET_KEY, algorithm=settings.ALGORITHM)
+
+
+def decode_session_token(token: str) -> Optional[int]:
+    """
+    Validate *token* and return the user's local DB id.
+
+    Returns ``None`` on any error (expired, wrong type, bad signature, …).
+    """
+    try:
+        payload = jwt.decode(token, settings.SECRET_KEY, algorithms=[settings.ALGORITHM])
+        if payload.get("type") != "dmarq_session":
+            return None
+        return int(payload["sub"])
+    except (JWTError, ValueError, TypeError):
+        return None
+
+
+# ── Local user sync ───────────────────────────────────────────────────────────
+
+
+def sync_logto_user(claims: IdTokenClaims, db: Session) -> User:
+    """
+    Upsert the local ``User`` shadow record from Logto ID-token claims.
+
+    Lookup order:
+    1. Match on ``logto_id`` (``sub`` claim) – fastest, stable.
+    2. Fall back to matching on email if the user was created before Logto
+       integration and doesn't have a ``logto_id`` yet.
+    3. Create a brand-new record if neither match.
+
+    All users are treated as admins (``is_superuser=True``) until RBAC is
+    added in a future milestone.
+    """
+    logto_id: str = claims.sub
+    email: str = claims.email or f"{logto_id}@logto.local"
+
+    # 1. Try existing Logto-linked user
+    user: Optional[User] = db.query(User).filter(User.logto_id == logto_id).first()
+
+    if user is None:
+        # 2. Try to link a legacy user by email
+        user = db.query(User).filter(User.email == email).first()
+        if user is not None:
+            user.logto_id = logto_id
+            logger.info(
+                "Linked existing user id=%d (%s) to Logto sub=%s",
+                user.id,
+                email,
+                logto_id,
+            )
+
+    if user is None:
+        # 3. Create new user
+        user = User(
+            logto_id=logto_id,
+            email=email,
+            is_active=True,
+            is_superuser=True,
+            is_verified=bool(getattr(claims, "email_verified", False)),
+        )
+        db.add(user)
+        db.flush()  # populate user.id before commit
+        logger.info("Created new user id=%d from Logto sub=%s (%s)", user.id, logto_id, email)
+
+    # Always refresh profile from latest claims
+    user.full_name = getattr(claims, "name", None) or user.full_name
+    user.username = getattr(claims, "username", None) or user.username
+    user.picture = getattr(claims, "picture", None) or user.picture
+    user.updated_at = datetime.utcnow()
+
+    db.commit()
+    db.refresh(user)
+    return user
diff --git a/backend/app/core/security.py b/backend/app/core/security.py
index c016dc3..0c55ad9 100644
--- a/backend/app/core/security.py
+++ b/backend/app/core/security.py
@@ -4,7 +4,7 @@ import secrets
 from datetime import datetime, timedelta
 from typing import Any, Optional, Union
 
-from fastapi import HTTPException, Security, status
+from fastapi import HTTPException, Request, Security, status
 from fastapi.security import APIKeyHeader, HTTPAuthorizationCredentials, HTTPBearer
 from jose import JWTError, jwt
 from passlib.context import CryptContext
@@ -162,42 +162,55 @@ async def verify_token(
 
 
 async def require_admin_auth(
+    request: Request,
     api_key: Optional[str] = Security(api_key_header),
     bearer: Optional[HTTPAuthorizationCredentials] = Security(security_bearer),
 ) -> dict:
     """
-    Dependency to require either API key or JWT token authentication for admin endpoints.
+    Dependency to require authentication for admin/API endpoints.
 
-    Checks API key first, then falls back to JWT token.
+    Accepts (in priority order):
+    1. ``dmarq_session`` cookie – set after a successful Logto login.
+    2. ``X-API-Key`` header    – static admin key for programmatic access.
+    3. ``Authorization: Bearer <token>`` header – app-issued JWT.
 
-    Args:
-        api_key: Optional API key from X-API-Key header
-        bearer: Optional JWT token from Authorization header
-
-    Returns:
-        Authentication context (api_key or token payload)
-
-    Raises:
-        HTTPException: If no valid authentication is provided
+    Returns an authentication context dict describing how the request was
+    authenticated.  Raises ``HTTP 401`` when no valid credential is present.
     """
-    # Try API key first
+    # 1. Session cookie (Logto-backed app session)
+    from app.core.logto import SESSION_COOKIE, decode_session_token  # local import
+
+    session_token = request.cookies.get(SESSION_COOKIE)
+    if session_token:
+        user_id = decode_session_token(session_token)
+        if user_id is not None:
+            return {"auth_type": "session", "user_id": user_id}
+
+    # 2. Static admin API key
     if api_key and verify_api_key(api_key):
         return {"auth_type": "api_key", "api_key": api_key}
 
-    # Try JWT token
+    # 3. Bearer JWT (app-issued; also covers Bearer tokens set by older clients)
     if bearer:
+        from app.core.logto import decode_session_token as _dec  # local import
+
+        user_id = _dec(bearer.credentials)
+        if user_id is not None:
+            return {"auth_type": "bearer", "user_id": user_id}
+
+        # Fallback: legacy python-jose JWT (pre-Logto API keys / CI tokens)
         try:
             payload = jwt.decode(
                 bearer.credentials, settings.SECRET_KEY, algorithms=[settings.ALGORITHM]
             )
             return {"auth_type": "jwt", "payload": payload}
         except JWTError as e:
-            logger.warning("Invalid JWT token: %s", str(e))
+            logger.warning("Invalid Bearer JWT: %s", str(e))
 
-    # No valid authentication provided
+    # No valid authentication
     raise HTTPException(
         status_code=status.HTTP_401_UNAUTHORIZED,
-        detail="Authentication required. Provide either X-API-Key header or Bearer token.",
+        detail="Authentication required. Provide a session cookie, X-API-Key header, or Bearer token.",
         headers={"WWW-Authenticate": "ApiKey, Bearer"},
     )
 
diff --git a/backend/app/main.py b/backend/app/main.py
index 2b6ac92..f52fc6e 100644
--- a/backend/app/main.py
+++ b/backend/app/main.py
@@ -17,10 +17,11 @@ from app.api.api_v1.api import api_router
 from app.core.config import get_settings
 from app.core.database import Base, SessionLocal, engine
 from app.core.security import add_api_key, generate_api_key, require_admin_auth
+from app.middleware.auth import AuthRedirectMiddleware
 from app.middleware.security import SecurityHeadersMiddleware
 from app.models.mail_source import MailSource  # noqa: F401 – ensure table is registered
-from app.services.gmail_client import GmailClient
 from app.models.user import User  # noqa: F401 – ensure User mapper is registered
+from app.services.gmail_client import GmailClient
 from app.services.imap_client import IMAPClient
 from app.services.report_store import ReportStore
 
@@ -255,6 +256,9 @@ def create_app() -> FastAPI:
     environment = os.getenv("ENVIRONMENT", "development")
     application.add_middleware(SecurityHeadersMiddleware, environment=environment)
 
+    # Auth redirect middleware – protects HTML pages; must sit outside CORS
+    application.add_middleware(AuthRedirectMiddleware)
+
     # Improved CORS configuration - restrict to specific methods and headers
     if settings.BACKEND_CORS_ORIGINS:
         application.add_middleware(
@@ -362,13 +366,28 @@ async def dashboard(request: Request):
 
 
 @app.get("/login", response_class=HTMLResponse)
-async def login(request: Request):
-    return templates.TemplateResponse(request, "login.html", {"app_name": settings.PROJECT_NAME})
+async def login(request: Request, next: str = "/"):
+    return templates.TemplateResponse(
+        request,
+        "login.html",
+        {
+            "app_name": settings.PROJECT_NAME,
+            "logto_configured": settings.logto_configured,
+            "next": next,
+        },
+    )
 
 
 @app.get("/setup", response_class=HTMLResponse)
 async def setup(request: Request):
-    return templates.TemplateResponse(request, "setup.html", {"app_name": settings.PROJECT_NAME})
+    return templates.TemplateResponse(
+        request,
+        "setup.html",
+        {
+            "app_name": settings.PROJECT_NAME,
+            "logto_configured": settings.logto_configured,
+        },
+    )
 
 
 @app.get("/domains", response_class=HTMLResponse)
@@ -418,9 +437,7 @@ async def reports(request: Request):
 @app.get("/reports/{report_id}", response_class=HTMLResponse)
 async def report_detail(request: Request, report_id: str):
     """View detailed information for a specific DMARC report"""
-    return templates.TemplateResponse(
-        request, "report_detail.html", {"report_id": report_id}
-    )
+    return templates.TemplateResponse(request, "report_detail.html", {"report_id": report_id})
 
 
 @app.get("/settings", response_class=HTMLResponse)
diff --git a/backend/app/middleware/auth.py b/backend/app/middleware/auth.py
new file mode 100644
index 0000000..a87f608
--- /dev/null
+++ b/backend/app/middleware/auth.py
@@ -0,0 +1,80 @@
+"""
+Authentication redirect middleware.
+
+Intercepts browser requests for protected HTML pages and redirects
+unauthenticated visitors to ``/login`` (or ``/setup`` if Logto is not yet
+configured).
+
+API routes (``/api/…``) are intentionally left to handle their own 401
+responses so that programmatic clients are not broken.
+"""
+
+from __future__ import annotations
+
+from starlette.middleware.base import BaseHTTPMiddleware
+from starlette.requests import Request
+from starlette.responses import RedirectResponse, Response
+from starlette.types import ASGIApp
+
+from app.core.logto import SESSION_COOKIE, decode_session_token
+
+# Paths that are always publicly accessible
+_PUBLIC_PATHS: frozenset[str] = frozenset(
+    {
+        "/login",
+        "/setup",
+        "/health",
+        "/healthz",
+    }
+)
+
+# Request path prefixes that bypass auth checks
+_PUBLIC_PREFIXES: tuple[str, ...] = (
+    "/api/",
+    "/static/",
+    "/docs",
+    "/redoc",
+    "/openapi",
+)
+
+
+class AuthRedirectMiddleware(BaseHTTPMiddleware):
+    """
+    Redirect unauthenticated browser requests to the appropriate page.
+
+    Decision tree
+    -------------
+    1. Path is public → pass through.
+    2. Session cookie present and valid → pass through.
+    3. Logto not configured → redirect to ``/setup``.
+    4. Otherwise → redirect to ``/login?next=<original_path>``.
+    """
+
+    def __init__(self, app: ASGIApp) -> None:
+        super().__init__(app)
+
+    async def dispatch(self, request: Request, call_next) -> Response:  # type: ignore[override]
+        path = request.url.path
+
+        # ── 1. Public paths & prefixes ────────────────────────────────────────
+        if path in _PUBLIC_PATHS:
+            return await call_next(request)
+        if any(path.startswith(p) for p in _PUBLIC_PREFIXES):
+            return await call_next(request)
+
+        # ── 2. Valid session cookie ───────────────────────────────────────────
+        token = request.cookies.get(SESSION_COOKIE)
+        if token and decode_session_token(token) is not None:
+            return await call_next(request)
+
+        # ── 3. Logto not configured ───────────────────────────────────────────
+        from app.core.config import get_settings  # local import avoids circular dep
+
+        if not get_settings().logto_configured:
+            return RedirectResponse(url="/setup", status_code=302)
+
+        # ── 4. Redirect to login ──────────────────────────────────────────────
+        next_path = request.url.path
+        if request.url.query:
+            next_path = f"{next_path}?{request.url.query}"
+        return RedirectResponse(url=f"/login?next={next_path}", status_code=302)
diff --git a/backend/app/models/user.py b/backend/app/models/user.py
index 1370a83..cc60640 100644
--- a/backend/app/models/user.py
+++ b/backend/app/models/user.py
@@ -1,24 +1,44 @@
-from sqlalchemy import Boolean, Column, Integer, String
+from datetime import datetime
+
+from sqlalchemy import Boolean, Column, DateTime, Integer, String
 from sqlalchemy.orm import relationship
 
 from app.core.database import Base
 
 
 class User(Base):
-    """User model"""
+    """User model – local shadow of the identity managed by Logto."""
 
     __tablename__ = "users"
 
     id = Column(Integer, primary_key=True, index=True)
     email = Column(String, unique=True, index=True, nullable=False)
-    hashed_password = Column(String, nullable=False)
+    # Logto subject claim (the user's stable ID inside Logto).
+    # Null for users that pre-date Logto integration or for
+    # programmatic/service accounts created directly in the DB.
+    logto_id = Column(String, unique=True, index=True, nullable=True)
+    # hashed_password kept for possible future local-auth fallback; nullable
+    # because Logto users authenticate externally and have no local password.
+    hashed_password = Column(String, nullable=True)
     is_active = Column(Boolean, default=True)
-    is_superuser = Column(Boolean, default=False)
+    # For now all users are treated as admin.  RBAC tiers are planned.
+    is_superuser = Column(Boolean, default=True)
     is_verified = Column(Boolean, default=False)
 
-    # Additional fields
+    # Profile – synced from Logto claims on every login
     full_name = Column(String, nullable=True)
+    username = Column(String, nullable=True)
     organization = Column(String, nullable=True)
+    picture = Column(String, nullable=True)
+
+    # Timestamps
+    created_at = Column(DateTime, default=datetime.utcnow, nullable=True)
+    updated_at = Column(
+        DateTime,
+        default=datetime.utcnow,
+        onupdate=datetime.utcnow,
+        nullable=True,
+    )
 
     # Relationships
     user_domains = relationship("UserDomain", back_populates="user", cascade="all, delete-orphan")
diff --git a/backend/app/templates/layouts/base.html b/backend/app/templates/layouts/base.html
index 25dda64..f3e5b98 100644
--- a/backend/app/templates/layouts/base.html
+++ b/backend/app/templates/layouts/base.html
@@ -19,7 +19,8 @@
 </head>
 <body class="min-h-screen bg-base-100 font-body antialiased">
     <!-- Updated Menu Bar -->
-    <header class="navbar bg-primary text-primary-content">
+    <header class="navbar bg-primary text-primary-content"
+            x-data="userMenu()" x-init="loadUser()">
         <div class="flex-1">
             <a href="/" class="btn btn-ghost normal-case text-xl">
                 <img src="/static/img/monogram_light.png" alt="DMARQ Logo" class="w-8 h-8 mr-2">
@@ -35,6 +36,41 @@
                 <li><a href="/mail-sources">Mail Sources</a></li>
                 <li><a href="/settings">Settings</a></li>
             </ul>
+            <!-- User menu -->
+            <div class="ml-2">
+                <template x-if="user">
+                    <div class="dropdown dropdown-end">
+                        <label tabindex="0" class="btn btn-ghost btn-circle avatar placeholder">
+                            <div class="bg-primary-content text-primary rounded-full w-8">
+                                <template x-if="user.picture">
+                                    <img :src="user.picture" :alt="user.full_name || user.email" class="rounded-full w-8 h-8 object-cover">
+                                </template>
+                                <template x-if="!user.picture">
+                                    <span class="text-sm font-semibold" x-text="(user.full_name || user.email || '?')[0].toUpperCase()"></span>
+                                </template>
+                            </div>
+                        </label>
+                        <ul tabindex="0" class="menu menu-sm dropdown-content mt-3 z-[1] p-2 shadow bg-base-100 text-base-content rounded-box w-56">
+                            <li class="menu-title px-2 py-1">
+                                <span class="text-xs font-semibold truncate" x-text="user.full_name || user.email"></span>
+                                <span class="text-xs text-base-content/50 truncate" x-text="user.email" x-show="user.full_name"></span>
+                            </li>
+                            <li><a href="/settings">Settings</a></li>
+                            <li>
+                                <a href="/api/v1/auth/sign-out" class="text-error">
+                                    <svg xmlns="http://www.w3.org/2000/svg" class="h-4 w-4" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M17 16l4-4m0 0l-4-4m4 4H7m6 4v1a3 3 0 01-3 3H6a3 3 0 01-3-3V7a3 3 0 013-3h4a3 3 0 013 3v1"/>
+                                    </svg>
+                                    Sign out
+                                </a>
+                            </li>
+                        </ul>
+                    </div>
+                </template>
+                <template x-if="!user">
+                    <a href="/login" class="btn btn-ghost btn-sm">Sign in</a>
+                </template>
+            </div>
         </div>
     </header>
 
@@ -45,7 +81,26 @@
 
     <!-- Scripts -->
     {% block scripts %}{% endblock %}
-    
+
+    <!-- User-menu Alpine component -->
+    <script>
+        function userMenu() {
+            return {
+                user: null,
+                async loadUser() {
+                    try {
+                        const res = await fetch('/api/v1/auth/me');
+                        if (res.ok) {
+                            this.user = await res.json();
+                        }
+                    } catch (_) {
+                        // silently ignore – user is simply not shown
+                    }
+                },
+            };
+        }
+    </script>
+
     <!-- Initialize theme from localStorage -->
     <script>
         document.addEventListener('DOMContentLoaded', function() {
diff --git a/backend/app/templates/login.html b/backend/app/templates/login.html
new file mode 100644
index 0000000..26e1afd
--- /dev/null
+++ b/backend/app/templates/login.html
@@ -0,0 +1,114 @@
+<!DOCTYPE html>
+<html lang="en" data-theme="dmarqlight">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Sign In – {{ app_name }}</title>
+
+    <link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@400;500;600;700&family=Open+Sans:wght@400;500;600&display=swap" rel="stylesheet">
+    <script src="https://cdn.tailwindcss.com"></script>
+    <link href="https://cdn.jsdelivr.net/npm/daisyui@4.12.24/dist/full.css" rel="stylesheet" type="text/css"/>
+    <script defer src="https://cdn.jsdelivr.net/npm/alpinejs@3.x.x/dist/cdn.min.js"></script>
+</head>
+<body class="min-h-screen bg-base-200 flex items-center justify-center font-sans antialiased">
+
+<div class="w-full max-w-md px-4">
+    <!-- Logo / brand -->
+    <div class="text-center mb-8">
+        <a href="/" class="inline-flex items-center gap-3">
+            <img src="/static/img/monogram_light.png" alt="{{ app_name }} logo" class="w-12 h-12">
+            <span class="text-3xl font-bold text-primary font-heading">{{ app_name }}</span>
+        </a>
+        <p class="mt-2 text-base-content/60 text-sm">DMARC Monitoring &amp; Analysis</p>
+    </div>
+
+    <div class="card bg-base-100 shadow-xl">
+        <div class="card-body gap-6">
+            <h1 class="card-title text-xl justify-center">Sign in to your account</h1>
+
+            {% if not logto_configured %}
+            <!-- Logto not yet configured -->
+            <div role="alert" class="alert alert-warning">
+                <svg xmlns="http://www.w3.org/2000/svg" class="h-5 w-5 shrink-0" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M12 9v2m0 4h.01M10.29 3.86L1.82 18a2 2 0 001.71 3h16.94a2 2 0 001.71-3L13.71 3.86a2 2 0 00-3.42 0z"/>
+                </svg>
+                <div>
+                    <p class="font-semibold">Authentication not configured</p>
+                    <p class="text-sm">Logto is not set up yet. Please visit the
+                        <a href="/setup" class="link link-warning font-medium">setup page</a>
+                        for configuration instructions.
+                    </p>
+                </div>
+            </div>
+            {% else %}
+
+            <!-- Error banner (shown when ?error= is present) -->
+            <div x-data="{ error: new URLSearchParams(window.location.search).get('error') }"
+                 x-show="error" x-cloak>
+                <div role="alert" class="alert alert-error">
+                    <svg xmlns="http://www.w3.org/2000/svg" class="h-5 w-5 shrink-0" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M6 18L18 6M6 6l12 12"/>
+                    </svg>
+                    <div>
+                        <p class="font-semibold">Sign-in failed</p>
+                        <p class="text-sm" x-text="error === 'callback_failed'
+                            ? 'The authentication callback failed. Please try again.'
+                            : error === 'token_error'
+                            ? 'Could not read authentication token. Please try again.'
+                            : 'An unexpected error occurred. Please try again.'">
+                        </p>
+                    </div>
+                </div>
+            </div>
+
+            <!-- Primary sign-in button -->
+            <div class="space-y-3">
+                <a href="/api/v1/auth/sign-in?next={{ next | urlencode }}"
+                   class="btn btn-primary btn-lg w-full gap-2">
+                    <!-- Logto "shield" icon approximation -->
+                    <svg xmlns="http://www.w3.org/2000/svg" class="w-5 h-5" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2"
+                              d="M12 2L4 5v6c0 5.25 3.5 9.74 8 11 4.5-1.26 8-5.75 8-11V5L12 2z"/>
+                    </svg>
+                    Sign in with Logto
+                </a>
+
+                <p class="text-center text-xs text-base-content/50">
+                    Logto securely handles authentication.
+                    Your credentials are never sent to {{ app_name }}.
+                </p>
+            </div>
+
+            <div class="divider text-xs text-base-content/40">What is Logto?</div>
+
+            <div class="text-sm text-base-content/60 space-y-1">
+                <p>
+                    <a href="https://logto.io" target="_blank" rel="noopener" class="link link-primary">Logto</a>
+                    is an open-source identity platform that supports email/password login,
+                    social providers (Google, GitHub, …), passkeys, and multi-factor authentication.
+                </p>
+                <p>
+                    It can be self-hosted alongside {{ app_name }} or used via the
+                    <a href="https://cloud.logto.io" target="_blank" rel="noopener" class="link link-primary">Logto Cloud</a>
+                    free tier.
+                </p>
+            </div>
+            {% endif %}
+        </div>
+    </div>
+
+    <p class="text-center mt-6 text-xs text-base-content/40">
+        &copy; {{ app_name }} – DMARC Monitoring Platform
+    </p>
+</div>
+
+<script>
+    // Restore dark-mode preference from localStorage (mirrors base.html logic)
+    (function () {
+        if (localStorage.getItem('darkMode') === 'true') {
+            document.documentElement.setAttribute('data-theme', 'dmarqdark');
+        }
+    })();
+</script>
+</body>
+</html>
diff --git a/backend/app/templates/settings.html b/backend/app/templates/settings.html
index 7ad0b87..3b41bf6 100644
--- a/backend/app/templates/settings.html
+++ b/backend/app/templates/settings.html
@@ -342,14 +342,19 @@ function settingsApp() {
         showCfToken: false,
         showSmtpPw: false,
 
+        // Session cookie is sent automatically by the browser (httpOnly, same-origin).
+        // No manual auth header needed for API calls from the UI.
         apiHeaders() {
-            const key = localStorage.getItem('adminApiKey') || '';
-            return { 'Content-Type': 'application/json', 'X-API-Key': key };
+            return { 'Content-Type': 'application/json' };
         },
 
         async loadSettings() {
             try {
                 const res = await fetch('/api/v1/settings', { headers: this.apiHeaders() });
+                if (res.status === 401 || res.status === 403) {
+                    window.location.href = '/login?next=/settings';
+                    return;
+                }
                 if (!res.ok) {
                     this.showFlash('Failed to load settings: ' + res.statusText, false);
                     return;
diff --git a/backend/app/templates/setup.html b/backend/app/templates/setup.html
new file mode 100644
index 0000000..b6e3cce
--- /dev/null
+++ b/backend/app/templates/setup.html
@@ -0,0 +1,178 @@
+<!DOCTYPE html>
+<html lang="en" data-theme="dmarqlight">
+<head>
+    <meta charset="UTF-8">
+    <meta name="viewport" content="width=device-width, initial-scale=1.0">
+    <title>Setup – {{ app_name }}</title>
+
+    <link href="https://fonts.googleapis.com/css2?family=Montserrat:wght@400;500;600;700&family=Open+Sans:wght@400;500;600&display=swap" rel="stylesheet">
+    <script src="https://cdn.tailwindcss.com"></script>
+    <link href="https://cdn.jsdelivr.net/npm/daisyui@4.12.24/dist/full.css" rel="stylesheet" type="text/css"/>
+    <script defer src="https://cdn.jsdelivr.net/npm/alpinejs@3.x.x/dist/cdn.min.js"></script>
+</head>
+<body class="min-h-screen bg-base-200 font-sans antialiased">
+
+<div class="max-w-3xl mx-auto px-4 py-12">
+
+    <!-- Logo / brand -->
+    <div class="text-center mb-10">
+        <a href="/" class="inline-flex items-center gap-3">
+            <img src="/static/img/monogram_light.png" alt="{{ app_name }} logo" class="w-12 h-12">
+            <span class="text-3xl font-bold text-primary font-heading">{{ app_name }}</span>
+        </a>
+        <h1 class="mt-3 text-2xl font-semibold">First-run Setup</h1>
+        <p class="mt-1 text-base-content/60 text-sm">Configure Logto to enable user authentication.</p>
+    </div>
+
+    {% if logto_configured %}
+    <!-- Already configured -->
+    <div class="card bg-base-100 shadow-xl mb-8">
+        <div class="card-body">
+            <div role="alert" class="alert alert-success">
+                <svg xmlns="http://www.w3.org/2000/svg" class="h-6 w-6 shrink-0" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                    <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M5 13l4 4L19 7"/>
+                </svg>
+                <div>
+                    <p class="font-semibold">Logto is configured!</p>
+                    <p class="text-sm">Authentication is ready. You can now
+                        <a href="/login" class="link link-success font-medium">sign in</a>.
+                    </p>
+                </div>
+            </div>
+        </div>
+    </div>
+    {% endif %}
+
+    <!-- Step-by-step guide -->
+    <div class="space-y-6">
+
+        <!-- Step 1 -->
+        <div class="card bg-base-100 shadow">
+            <div class="card-body">
+                <h2 class="card-title text-lg">
+                    <span class="badge badge-primary badge-lg mr-2">1</span>
+                    Deploy or sign up for Logto
+                </h2>
+                <p class="text-sm text-base-content/70">
+                    Choose one of the options below.  Both are free to start.
+                </p>
+                <div class="grid grid-cols-1 sm:grid-cols-2 gap-4 mt-2">
+                    <div class="border border-base-300 rounded-lg p-4 space-y-2">
+                        <p class="font-semibold text-sm">☁️ Logto Cloud (recommended)</p>
+                        <p class="text-xs text-base-content/60">
+                            Sign up at
+                            <a href="https://cloud.logto.io" target="_blank" rel="noopener" class="link link-primary">cloud.logto.io</a>.
+                            The free tier supports unlimited users.
+                        </p>
+                    </div>
+                    <div class="border border-base-300 rounded-lg p-4 space-y-2">
+                        <p class="font-semibold text-sm">🐳 Self-hosted (Docker)</p>
+                        <p class="text-xs text-base-content/60">
+                            Add Logto to your <code class="font-mono">docker-compose.yml</code>
+                            (see the
+                            <a href="https://docs.logto.io/docs/recipes/deployment/" target="_blank" rel="noopener" class="link link-primary">Logto deployment guide</a>).
+                        </p>
+                    </div>
+                </div>
+            </div>
+        </div>
+
+        <!-- Step 2 -->
+        <div class="card bg-base-100 shadow">
+            <div class="card-body">
+                <h2 class="card-title text-lg">
+                    <span class="badge badge-primary badge-lg mr-2">2</span>
+                    Create a "Traditional Web" application in Logto
+                </h2>
+                <ol class="list-decimal list-inside text-sm text-base-content/70 space-y-1 mt-1">
+                    <li>Open the <strong>Logto Console</strong> → <em>Applications</em> → <em>Create application</em>.</li>
+                    <li>Choose <strong>Traditional Web</strong>.</li>
+                    <li>Enter a name, e.g. <em>DMARQ</em>.</li>
+                    <li>
+                        Set the <strong>Redirect URI</strong> to:<br>
+                        <code class="font-mono bg-base-200 px-2 py-0.5 rounded text-xs break-all">
+                            &lt;your-dmarq-url&gt;/api/v1/auth/callback
+                        </code>
+                    </li>
+                    <li>
+                        Set the <strong>Post Sign-out Redirect URI</strong> to:<br>
+                        <code class="font-mono bg-base-200 px-2 py-0.5 rounded text-xs break-all">
+                            &lt;your-dmarq-url&gt;/login
+                        </code>
+                    </li>
+                    <li>Save and note the <strong>App ID</strong> and <strong>App Secret</strong>.</li>
+                </ol>
+            </div>
+        </div>
+
+        <!-- Step 3 -->
+        <div class="card bg-base-100 shadow">
+            <div class="card-body">
+                <h2 class="card-title text-lg">
+                    <span class="badge badge-primary badge-lg mr-2">3</span>
+                    Set environment variables and restart {{ app_name }}
+                </h2>
+                <p class="text-sm text-base-content/70 mb-3">
+                    Add the following to your <code class="font-mono">.env</code> file or Docker environment:
+                </p>
+                <div class="mockup-code text-xs">
+                    <pre><code># Logto endpoint – the base URL of your Logto instance
+LOGTO_ENDPOINT=https://&lt;your-tenant&gt;.logto.app
+
+# Application credentials from the Logto Console
+LOGTO_APP_ID=&lt;your-app-id&gt;
+LOGTO_APP_SECRET=&lt;your-app-secret&gt;
+
+# Optional: override the callback URL (defaults to &lt;base_url&gt;/api/v1/auth/callback)
+# LOGTO_REDIRECT_URI=https://dmarc.example.com/api/v1/auth/callback</code></pre>
+                </div>
+                <div role="alert" class="alert alert-info mt-4 text-sm">
+                    <svg xmlns="http://www.w3.org/2000/svg" class="h-5 w-5 shrink-0" fill="none" viewBox="0 0 24 24" stroke="currentColor">
+                        <path stroke-linecap="round" stroke-linejoin="round" stroke-width="2" d="M13 16h-1v-4h-1m1-4h.01M12 2a10 10 0 100 20A10 10 0 0012 2z"/>
+                    </svg>
+                    <p>
+                        For Docker Compose, set these in the <code class="font-mono">environment:</code> section
+                        of the <em>backend</em> service and run <code class="font-mono">docker compose up -d --force-recreate</code>.
+                    </p>
+                </div>
+            </div>
+        </div>
+
+        <!-- Step 4 -->
+        <div class="card bg-base-100 shadow">
+            <div class="card-body">
+                <h2 class="card-title text-lg">
+                    <span class="badge badge-primary badge-lg mr-2">4</span>
+                    (Optional) Add authentication providers in Logto
+                </h2>
+                <p class="text-sm text-base-content/70">
+                    Logto lets you enable social providers (Google, GitHub, Microsoft, …),
+                    SMS / email passwordless, and multi-factor authentication entirely through
+                    its console – no code changes needed in {{ app_name }}.
+                </p>
+                <p class="text-sm text-base-content/70 mt-2">
+                    See the
+                    <a href="https://docs.logto.io/docs/recipes/configure-connectors/" target="_blank" rel="noopener" class="link link-primary">Logto connector docs</a>
+                    for details.
+                </p>
+            </div>
+        </div>
+
+        {% if logto_configured %}
+        <div class="text-center mt-4">
+            <a href="/login" class="btn btn-primary btn-lg">Go to Sign-in</a>
+        </div>
+        {% endif %}
+
+    </div><!-- /space-y-6 -->
+</div>
+
+<script>
+    (function () {
+        if (localStorage.getItem('darkMode') === 'true') {
+            document.documentElement.setAttribute('data-theme', 'dmarqdark');
+        }
+    })();
+</script>
+</body>
+</html>
diff --git a/backend/app/tests/test_auth.py b/backend/app/tests/test_auth.py
new file mode 100644
index 0000000..7dbcade
--- /dev/null
+++ b/backend/app/tests/test_auth.py
@@ -0,0 +1,239 @@
+"""
+Tests for the Logto-based authentication layer.
+
+These tests exercise:
+- Session-token creation and decoding (app.core.logto)
+- CookieStorage read/write/delete semantics
+- sync_logto_user DB upsert logic
+- /api/v1/auth/me – authenticated and unauthenticated
+- /api/v1/auth/sign-in – Logto not configured → 503
+- /api/v1/auth/sign-out – always clears the session cookie
+
+All tests use the in-memory SQLite fixture from conftest.py.
+Logto SDK calls are mocked so no live Logto instance is needed.
+"""
+
+from __future__ import annotations
+
+from unittest.mock import MagicMock, patch
+
+from fastapi.testclient import TestClient
+
+from app.core.logto import (
+    SESSION_COOKIE,
+    CookieStorage,
+    create_session_token,
+    decode_session_token,
+    sync_logto_user,
+)
+from app.models.user import User
+
+# ── Session token helpers ─────────────────────────────────────────────────────
+
+
+class TestSessionToken:
+    def test_roundtrip(self):
+        token = create_session_token(user_id=7)
+        assert decode_session_token(token) == 7
+
+    def test_invalid_token_returns_none(self):
+        assert decode_session_token("not.a.token") is None
+
+    def test_wrong_type_returns_none(self):
+        """A generic JWT without the dmarq_session type claim should be rejected."""
+        from jose import jwt
+
+        from app.core.config import get_settings
+
+        s = get_settings()
+        payload = {"sub": "5", "type": "other"}
+        bad_token = jwt.encode(payload, s.SECRET_KEY, algorithm=s.ALGORITHM)
+        assert decode_session_token(bad_token) is None
+
+
+# ── CookieStorage ─────────────────────────────────────────────────────────────
+
+
+class TestCookieStorage:
+    def _make_request(self, cookies: dict = None):
+        req = MagicMock()
+        req.cookies = cookies or {}
+        return req
+
+    def _make_response(self):
+        from starlette.responses import Response
+
+        return Response()
+
+    def test_get_from_request_cookies(self):
+        req = self._make_request({"logto_idToken": "abc123"})
+        storage = CookieStorage(req)
+        assert storage.get("idToken") == "abc123"
+
+    def test_pending_write_shadows_cookie(self):
+        req = self._make_request({"logto_idToken": "old"})
+        storage = CookieStorage(req)
+        storage.set("idToken", "new")
+        assert storage.get("idToken") == "new"
+
+    def test_delete_shadows_cookie(self):
+        req = self._make_request({"logto_idToken": "exists"})
+        storage = CookieStorage(req)
+        storage.delete("idToken")
+        assert storage.get("idToken") is None
+
+    def test_apply_to_response_sets_cookies(self):
+        storage = CookieStorage(self._make_request())
+        storage.set("idToken", "tok123")
+        resp = self._make_response()
+        storage.apply_to_response(resp)
+        # Cookie header should contain the key
+        header_str = str(resp.headers.get("set-cookie", ""))
+        assert "logto_idToken" in header_str
+
+    def test_apply_to_response_deletes_cookies(self):
+        req = self._make_request({"logto_idToken": "old"})
+        storage = CookieStorage(req)
+        storage.delete("idToken")
+        resp = self._make_response()
+        storage.apply_to_response(resp)
+        header_str = str(resp.headers.get("set-cookie", ""))
+        assert "logto_idToken" in header_str
+        # A deleted cookie is set with max-age=0
+        assert "Max-Age=0" in header_str or "expires" in header_str.lower()
+
+
+# ── sync_logto_user ───────────────────────────────────────────────────────────
+
+
+class TestSyncLogtoUser:
+    def _claims(self, sub="logto-sub-1", email="user@example.com", name="Test User"):
+        claims = MagicMock()
+        claims.sub = sub
+        claims.email = email
+        claims.name = name
+        claims.username = None
+        claims.picture = None
+        claims.email_verified = True
+        return claims
+
+    def test_creates_new_user(self, db_session):
+        claims = self._claims()
+        user = sync_logto_user(claims, db_session)
+        assert user.id is not None
+        assert user.logto_id == "logto-sub-1"
+        assert user.email == "user@example.com"
+        assert user.full_name == "Test User"
+        assert user.is_superuser is True
+
+    def test_returns_existing_user_by_logto_id(self, db_session):
+        # Create user first
+        claims = self._claims()
+        user1 = sync_logto_user(claims, db_session)
+        uid = user1.id
+
+        # Second call with same sub → same user, no duplicate
+        user2 = sync_logto_user(claims, db_session)
+        assert user2.id == uid
+        total = db_session.query(User).count()
+        assert total == 1
+
+    def test_links_existing_user_by_email(self, db_session):
+        """Legacy user with matching email but no logto_id gets linked."""
+        legacy = User(email="user@example.com", is_active=True, is_superuser=True)
+        db_session.add(legacy)
+        db_session.commit()
+
+        claims = self._claims(sub="new-sub", email="user@example.com")
+        user = sync_logto_user(claims, db_session)
+
+        assert user.id == legacy.id
+        assert user.logto_id == "new-sub"
+
+    def test_updates_profile_on_subsequent_login(self, db_session):
+        claims = self._claims(name="Old Name")
+        sync_logto_user(claims, db_session)
+
+        claims2 = self._claims(name="New Name")
+        user = sync_logto_user(claims2, db_session)
+        assert user.full_name == "New Name"
+
+
+# ── /api/v1/auth/me ───────────────────────────────────────────────────────────
+
+
+class TestAuthMeEndpoint:
+    def test_me_unauthenticated_returns_401(self, client: TestClient):
+        res = client.get("/api/v1/auth/me")
+        assert res.status_code == 401
+
+    def test_me_with_valid_session_returns_user(self, client: TestClient, db_session):
+        # Create a user in the DB
+        user = User(
+            email="me@example.com",
+            logto_id="sub-me",
+            is_active=True,
+            is_superuser=True,
+        )
+        db_session.add(user)
+        db_session.commit()
+        db_session.refresh(user)
+
+        token = create_session_token(user.id)
+        res = client.get("/api/v1/auth/me", cookies={SESSION_COOKIE: token})
+        assert res.status_code == 200
+        data = res.json()
+        assert data["email"] == "me@example.com"
+        assert data["logto_id"] == "sub-me"
+
+    def test_me_with_invalid_session_returns_401(self, client: TestClient):
+        res = client.get("/api/v1/auth/me", cookies={SESSION_COOKIE: "garbage"})
+        assert res.status_code == 401
+
+    def test_me_with_inactive_user_returns_401(self, client: TestClient, db_session):
+        user = User(
+            email="inactive@example.com",
+            logto_id="sub-inactive",
+            is_active=False,
+            is_superuser=True,
+        )
+        db_session.add(user)
+        db_session.commit()
+        db_session.refresh(user)
+
+        token = create_session_token(user.id)
+        res = client.get("/api/v1/auth/me", cookies={SESSION_COOKIE: token})
+        assert res.status_code == 401
+
+
+# ── /api/v1/auth/sign-in ─────────────────────────────────────────────────────
+
+
+class TestSignInEndpoint:
+    def test_sign_in_without_logto_config_returns_503(self, client: TestClient):
+        """When Logto is not configured the endpoint must return 503."""
+        with patch("app.api.api_v1.endpoints.auth.settings") as mock_settings:
+            mock_settings.logto_configured = False
+            res = client.get("/api/v1/auth/sign-in", follow_redirects=False)
+        assert res.status_code == 503
+
+
+# ── /api/v1/auth/sign-out ────────────────────────────────────────────────────
+
+
+class TestSignOutEndpoint:
+    def test_sign_out_clears_session_cookie(self, client: TestClient):
+        """Sign-out must delete the dmarq_session cookie regardless of Logto config."""
+        token = create_session_token(user_id=1)
+        # Use allow_redirects=False so we see the redirect response with cookies
+        res = client.get(
+            "/api/v1/auth/sign-out",
+            cookies={SESSION_COOKIE: token},
+            follow_redirects=False,
+        )
+        # Should redirect (to /login or Logto end_session)
+        assert res.status_code in (302, 307)
+        # The session cookie must be cleared (max-age=0 or expires in past)
+        set_cookie = res.headers.get("set-cookie", "")
+        assert SESSION_COOKIE in set_cookie
+        assert "Max-Age=0" in set_cookie or "max-age=0" in set_cookie
diff --git a/backend/app/tests/test_gmail_client.py b/backend/app/tests/test_gmail_client.py
index 4ef3c23..bd65339 100644
--- a/backend/app/tests/test_gmail_client.py
+++ b/backend/app/tests/test_gmail_client.py
@@ -9,8 +9,8 @@ import base64
 import email as email_mod
 import json
 from email import encoders as email_encoders
-from email.mime.multipart import MIMEMultipart
 from email.mime.base import MIMEBase
+from email.mime.multipart import MIMEMultipart
 from email.mime.text import MIMEText
 from typing import Optional
 from unittest.mock import MagicMock, patch
@@ -19,7 +19,6 @@ import pytest
 
 from app.services.gmail_client import GmailClient
 
-
 # ---------------------------------------------------------------------------
 # Helpers
 # ---------------------------------------------------------------------------
@@ -234,9 +233,7 @@ class TestGetGmailEmail:
         assert result is None
 
     def test_returns_none_on_exception(self):
-        with patch(
-            "app.services.gmail_client.httpx.get", side_effect=Exception("network error")
-        ):
+        with patch("app.services.gmail_client.httpx.get", side_effect=Exception("network error")):
             result = GmailClient.get_gmail_email("some-token")
 
         assert result is None
@@ -264,8 +261,9 @@ class TestBuildService:
         client._mock_creds.refresh_token = "ref"
 
         mock_service = MagicMock()
-        with patch("app.services.gmail_client.build", return_value=mock_service), patch(
-            "app.services.gmail_client.Request"
+        with (
+            patch("app.services.gmail_client.build", return_value=mock_service),
+            patch("app.services.gmail_client.Request"),
         ):
             svc = client._build_service()
 
@@ -278,9 +276,7 @@ class TestBuildService:
         client._mock_creds.refresh_token = "ref"
         client._mock_creds.refresh.side_effect = Exception("refresh failed")
 
-        with patch("app.services.gmail_client.Request"), patch(
-            "app.services.gmail_client.build"
-        ):
+        with patch("app.services.gmail_client.Request"), patch("app.services.gmail_client.build"):
             with pytest.raises(Exception, match="refresh failed"):
                 client._build_service()
 
@@ -397,9 +393,7 @@ class TestProcessMessage:
     def test_fetches_and_processes_message(self):
         """Happy path: message fetched, attachments processed."""
         client = _make_client()
-        raw_email = _make_raw_email(
-            [{"filename": "report.xml", "content": b"<xml/>"}]
-        )
+        raw_email = _make_raw_email([{"filename": "report.xml", "content": b"<xml/>"}])
         raw_b64 = _b64_raw(raw_email)
 
         service = MagicMock()
@@ -440,9 +434,7 @@ class TestProcessMessage:
 class TestProcessAttachments:
     def test_no_attachments_returns_zero(self):
         client = _make_client()
-        msg = email_mod.message_from_bytes(
-            b"From: a@b.com\r\nTo: c@d.com\r\n\r\nHello"
-        )
+        msg = email_mod.message_from_bytes(b"From: a@b.com\r\nTo: c@d.com\r\n\r\nHello")
         stats = {"reports_found": 0, "errors": []}
         count = client._process_attachments(msg, stats)
         assert count == 0
@@ -450,9 +442,7 @@ class TestProcessAttachments:
     def test_non_dmarc_attachment_skipped(self):
         """An inline or non-DMARC file should not count as a report."""
         client = _make_client()
-        raw = _make_raw_email(
-            [{"filename": "photo.png", "content": b"\x89PNG"}]
-        )
+        raw = _make_raw_email([{"filename": "photo.png", "content": b"\x89PNG"}])
         msg = email_mod.message_from_bytes(raw)
         stats = {"reports_found": 0, "errors": []}
         count = client._process_attachments(msg, stats)
@@ -462,9 +452,7 @@ class TestProcessAttachments:
     def test_dmarc_xml_attachment_is_parsed(self):
         """A .xml attachment is parsed via DMARCParser and counts as a report."""
         client = _make_client()
-        raw = _make_raw_email(
-            [{"filename": "report.xml", "content": b"<xml_content/>"}]
-        )
+        raw = _make_raw_email([{"filename": "report.xml", "content": b"<xml_content/>"}])
         msg = email_mod.message_from_bytes(raw)
         stats = {"reports_found": 0, "errors": []}
 
@@ -484,9 +472,7 @@ class TestProcessAttachments:
         """A DMARC-named attachment with truly empty payload is skipped gracefully."""
         client = _make_client()
         # Build an attachment with empty bytes – base64 of b"" is b""
-        raw = _make_raw_email(
-            [{"filename": "report.zip", "content": b""}]
-        )
+        raw = _make_raw_email([{"filename": "report.zip", "content": b""}])
         msg = email_mod.message_from_bytes(raw)
         stats = {"reports_found": 0, "errors": []}
         count = client._process_attachments(msg, stats)
@@ -536,9 +522,7 @@ class TestProcessAttachments:
 class TestFetchReports:
     def test_returns_failure_when_build_service_raises(self):
         client = _make_client()
-        with patch.object(
-            client, "_build_service", side_effect=Exception("auth error")
-        ):
+        with patch.object(client, "_build_service", side_effect=Exception("auth error")):
             result = client.fetch_reports()
 
         assert result["success"] is False
@@ -547,8 +531,9 @@ class TestFetchReports:
     def test_returns_failure_when_list_messages_raises(self):
         client = _make_client()
         mock_service = MagicMock()
-        with patch.object(client, "_build_service", return_value=mock_service), patch.object(
-            client, "_list_dmarc_message_ids", side_effect=Exception("list error")
+        with (
+            patch.object(client, "_build_service", return_value=mock_service),
+            patch.object(client, "_list_dmarc_message_ids", side_effect=Exception("list error")),
         ):
             result = client.fetch_reports()
 
@@ -557,8 +542,9 @@ class TestFetchReports:
     def test_returns_success_with_no_messages(self):
         client = _make_client()
         mock_service = MagicMock()
-        with patch.object(client, "_build_service", return_value=mock_service), patch.object(
-            client, "_list_dmarc_message_ids", return_value=[]
+        with (
+            patch.object(client, "_build_service", return_value=mock_service),
+            patch.object(client, "_list_dmarc_message_ids", return_value=[]),
         ):
             result = client.fetch_reports()
 
@@ -568,9 +554,11 @@ class TestFetchReports:
     def test_skips_already_ingested_messages(self):
         client = _make_client(already_ingested=["id1"])
         mock_service = MagicMock()
-        with patch.object(client, "_build_service", return_value=mock_service), patch.object(
-            client, "_list_dmarc_message_ids", return_value=["id1", "id2"]
-        ), patch.object(client, "_process_message", return_value=0) as mock_proc:
+        with (
+            patch.object(client, "_build_service", return_value=mock_service),
+            patch.object(client, "_list_dmarc_message_ids", return_value=["id1", "id2"]),
+            patch.object(client, "_process_message", return_value=0) as mock_proc,
+        ):
             result = client.fetch_reports()
 
         # Only id2 should be processed; id1 is already ingested
@@ -582,9 +570,11 @@ class TestFetchReports:
     def test_tracks_new_ingested_ids(self):
         client = _make_client()
         mock_service = MagicMock()
-        with patch.object(client, "_build_service", return_value=mock_service), patch.object(
-            client, "_list_dmarc_message_ids", return_value=["id1", "id2"]
-        ), patch.object(client, "_process_message", return_value=0):
+        with (
+            patch.object(client, "_build_service", return_value=mock_service),
+            patch.object(client, "_list_dmarc_message_ids", return_value=["id1", "id2"]),
+            patch.object(client, "_process_message", return_value=0),
+        ):
             result = client.fetch_reports()
 
         assert "id1" in result["new_ingested_ids"]
@@ -612,9 +602,11 @@ class TestFetchReports:
             stats["reports_found"] += 1
             return 1
 
-        with patch.object(client, "_build_service", return_value=mock_service), patch.object(
-            client, "_list_dmarc_message_ids", return_value=["id1"]
-        ), patch.object(client, "_process_message", side_effect=_process_side_effect):
+        with (
+            patch.object(client, "_build_service", return_value=mock_service),
+            patch.object(client, "_list_dmarc_message_ids", return_value=["id1"]),
+            patch.object(client, "_process_message", side_effect=_process_side_effect),
+        ):
             result = client.fetch_reports()
 
         assert "newdomain.example" in result["new_domains"]
diff --git a/backend/app/tests/test_imap_client.py b/backend/app/tests/test_imap_client.py
index 1a4ed35..34c9040 100644
--- a/backend/app/tests/test_imap_client.py
+++ b/backend/app/tests/test_imap_client.py
@@ -19,7 +19,6 @@ import pytest
 from app.services.imap_client import IMAPClient
 from app.services.report_store import ReportStore
 
-
 # ---------------------------------------------------------------------------
 # Helpers
 # ---------------------------------------------------------------------------
@@ -316,9 +315,7 @@ class TestIsDmarcReportEmail:
 
     def test_dmarc_sender_matches(self):
         client = self._make_client()
-        msg = self._make_msg(
-            subject="Weekly report", from_addr="noreply@google.com"
-        )
+        msg = self._make_msg(subject="Weekly report", from_addr="noreply@google.com")
         assert client._is_dmarc_report_email(msg) is True
 
     def test_xml_attachment_matches(self):
@@ -443,9 +440,7 @@ class TestProcessAttachments:
 
     def test_bad_attachment_does_not_raise(self):
         client = self._make_client()
-        msg = email.message_from_bytes(
-            _make_email_with_attachment("report.xml", b"not xml at all")
-        )
+        msg = email.message_from_bytes(_make_email_with_attachment("report.xml", b"not xml at all"))
         # Should not raise; just returns 0
         count = client._process_attachments(msg)
         assert count == 0
diff --git a/backend/app/tests/test_mail_sources.py b/backend/app/tests/test_mail_sources.py
index 8efa9cb..1705ec9 100644
--- a/backend/app/tests/test_mail_sources.py
+++ b/backend/app/tests/test_mail_sources.py
@@ -503,9 +503,7 @@ class TestGmailAPIMailSource:
             return_value=mock_gmail_client,
         ):
             # First set the access token directly
-            with patch(
-                "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-            ) as mock_get:
+            with patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get:
                 mock_source = MagicMock()
                 mock_source.method = "GMAIL_API"
                 mock_source.gmail_access_token = "valid-token"
@@ -627,10 +625,9 @@ class TestGmailAPIMailSource:
         mock_client.fetch_reports.return_value = mock_fetch_results
         mock_client.get_refreshed_tokens.return_value = None
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-        ) as mock_get, patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client
+        with (
+            patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get,
+            patch("app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client),
         ):
             mock_source = MagicMock()
             mock_source.method = "GMAIL_API"
@@ -843,9 +840,7 @@ class TestGmailCallbackGet:
         )
         source_id = create_resp.json()["id"]
 
-        resp = authed_client.get(
-            f"/api/v1/mail-sources/{source_id}/gmail/callback?code=xyz"
-        )
+        resp = authed_client.get(f"/api/v1/mail-sources/{source_id}/gmail/callback?code=xyz")
         assert resp.status_code == 404
 
     def test_callback_token_exchange_error_returns_html_400(self, authed_client: TestClient):
@@ -860,9 +855,7 @@ class TestGmailCallbackGet:
             "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
             side_effect=ValueError("bad token"),
         ):
-            resp = authed_client.get(
-                f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc"
-            )
+            resp = authed_client.get(f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc")
 
         assert resp.status_code == 400
         assert "token exchange failed" in resp.text.lower() or "failed" in resp.text.lower()
@@ -879,9 +872,7 @@ class TestGmailCallbackGet:
             "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
             return_value={},  # empty – no access_token key
         ):
-            resp = authed_client.get(
-                f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc"
-            )
+            resp = authed_client.get(f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc")
 
         assert resp.status_code == 400
 
@@ -893,16 +884,17 @@ class TestGmailCallbackGet:
         )
         source_id = create_resp.json()["id"]
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
-            return_value={"access_token": "acc", "refresh_token": "ref"},
-        ), patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
-            return_value="user@gmail.com",
+        with (
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
+                return_value={"access_token": "acc", "refresh_token": "ref"},
+            ),
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
+                return_value="user@gmail.com",
+            ),
         ):
-            resp = authed_client.get(
-                f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc"
-            )
+            resp = authed_client.get(f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc")
 
         assert resp.status_code == 200
         assert "connected successfully" in resp.text.lower() or "gmail" in resp.text.lower()
@@ -920,16 +912,17 @@ class TestGmailCallbackGet:
         )
         source_id = create_resp.json()["id"]
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
-            return_value={"access_token": "acc"},  # no refresh token
-        ), patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
-            return_value=None,
+        with (
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
+                return_value={"access_token": "acc"},  # no refresh token
+            ),
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
+                return_value=None,
+            ),
         ):
-            resp = authed_client.get(
-                f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc"
-            )
+            resp = authed_client.get(f"/api/v1/mail-sources/{source_id}/gmail/callback?code=abc")
 
         assert resp.status_code == 200
         get_resp = authed_client.get(f"/api/v1/mail-sources/{source_id}")
@@ -999,12 +992,15 @@ class TestGmailCallbackPost:
         )
         source_id = create_resp.json()["id"]
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
-            return_value={"access_token": "acc", "refresh_token": "ref"},
-        ), patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
-            return_value="user@gmail.com",
+        with (
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.exchange_code_for_tokens",
+                return_value={"access_token": "acc", "refresh_token": "ref"},
+            ),
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient.get_gmail_email",
+                return_value="user@gmail.com",
+            ),
         ):
             resp = authed_client.post(
                 f"/api/v1/mail-sources/{source_id}/gmail/callback",
@@ -1052,10 +1048,9 @@ class TestGmailFetchExtra:
         mock_client.fetch_reports.return_value = mock_fetch_results
         mock_client.get_refreshed_tokens.return_value = None
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-        ) as mock_get, patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client
+        with (
+            patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get,
+            patch("app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client),
         ):
             mock_source = MagicMock()
             mock_source.method = "GMAIL_API"
@@ -1099,10 +1094,9 @@ class TestGmailFetchExtra:
             "refresh_token": "new_refresh",
         }
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-        ) as mock_get, patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client
+        with (
+            patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get,
+            patch("app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client),
         ):
             mock_source = MagicMock()
             mock_source.method = "GMAIL_API"
@@ -1141,11 +1135,12 @@ class TestGmailFetchExtra:
         mock_client.fetch_reports.return_value = mock_fetch_results
         mock_client.get_refreshed_tokens.return_value = None
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-        ) as mock_get, patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client
-        ) as mock_gmail_class:
+        with (
+            patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get,
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient", return_value=mock_client
+            ) as mock_gmail_class,
+        ):
             # Configure the class-level static helpers used inside the endpoint
             mock_gmail_class.load_ingested_ids.return_value = ["id1"]
             mock_gmail_class.dump_ingested_ids.return_value = '["id1","id2","id3"]'
@@ -1188,18 +1183,19 @@ class TestGmailTestConnectionFailure:
         source_id = create_resp.json()["id"]
 
         mock_service = MagicMock()
-        mock_service.users.return_value.getProfile.return_value.execute.side_effect = (
-            Exception("internal oauth error: token expired")
+        mock_service.users.return_value.getProfile.return_value.execute.side_effect = Exception(
+            "internal oauth error: token expired"
         )
         mock_gmail_client = MagicMock()
         mock_gmail_client._build_service.return_value = mock_service
 
-        with patch(
-            "app.api.api_v1.endpoints.mail_sources.GmailClient",
-            return_value=mock_gmail_client,
-        ), patch(
-            "app.api.api_v1.endpoints.mail_sources._get_source_or_404"
-        ) as mock_get:
+        with (
+            patch(
+                "app.api.api_v1.endpoints.mail_sources.GmailClient",
+                return_value=mock_gmail_client,
+            ),
+            patch("app.api.api_v1.endpoints.mail_sources._get_source_or_404") as mock_get,
+        ):
             mock_source = MagicMock()
             mock_source.method = "GMAIL_API"
             mock_source.gmail_access_token = "tok"
@@ -1274,10 +1270,11 @@ class TestPollSingleGmailSource:
         mock_db.__exit__ = MagicMock(return_value=False)
         mock_db.query.return_value.get.return_value = mock_db_source
 
-        with patch("app.main.GmailClient", return_value=mock_client), patch(
-            "app.main.SessionLocal", return_value=mock_db
-        ), patch("app.main.GmailClient.load_ingested_ids", return_value=[]), patch(
-            "app.main.GmailClient.dump_ingested_ids", return_value='["id1","id2"]'
+        with (
+            patch("app.main.GmailClient", return_value=mock_client),
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
+            patch("app.main.GmailClient.dump_ingested_ids", return_value='["id1","id2"]'),
         ):
             _poll_single_gmail_source(src)
 
@@ -1303,9 +1300,11 @@ class TestPollSingleGmailSource:
         mock_db = MagicMock()
         mock_db.query.return_value.get.return_value = MagicMock()
 
-        with patch("app.main.GmailClient", return_value=mock_client), patch(
-            "app.main.SessionLocal", return_value=mock_db
-        ), patch("app.main.GmailClient.load_ingested_ids", return_value=[]):
+        with (
+            patch("app.main.GmailClient", return_value=mock_client),
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
+        ):
             _poll_single_gmail_source(src)  # should not raise
 
     def test_logs_error_on_failure(self):
@@ -1329,9 +1328,11 @@ class TestPollSingleGmailSource:
         mock_db = MagicMock()
         mock_db.query.return_value.get.return_value = MagicMock()
 
-        with patch("app.main.GmailClient", return_value=mock_client), patch(
-            "app.main.SessionLocal", return_value=mock_db
-        ), patch("app.main.GmailClient.load_ingested_ids", return_value=[]):
+        with (
+            patch("app.main.GmailClient", return_value=mock_client),
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
+        ):
             _poll_single_gmail_source(src)  # should not raise
 
     def test_persists_refreshed_tokens(self):
@@ -1358,9 +1359,11 @@ class TestPollSingleGmailSource:
         mock_db = MagicMock()
         mock_db.query.return_value.get.return_value = mock_db_source
 
-        with patch("app.main.GmailClient", return_value=mock_client), patch(
-            "app.main.SessionLocal", return_value=mock_db
-        ), patch("app.main.GmailClient.load_ingested_ids", return_value=[]):
+        with (
+            patch("app.main.GmailClient", return_value=mock_client),
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
+        ):
             _poll_single_gmail_source(src)
 
         assert mock_db_source.gmail_access_token == "new-acc"
@@ -1432,9 +1435,11 @@ class TestTriggerPollGmailSource:
         mock_gc.get_refreshed_tokens.return_value = None
         mock_db = MagicMock()
 
-        with patch("app.main.GmailClient", return_value=mock_gc), patch(
-            "app.main.GmailClient.load_ingested_ids", return_value=[]
-        ), patch("app.main.GmailClient.dump_ingested_ids", return_value='["id1"]'):
+        with (
+            patch("app.main.GmailClient", return_value=mock_gc),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
+            patch("app.main.GmailClient.dump_ingested_ids", return_value='["id1"]'),
+        ):
             result = _trigger_poll_gmail_source(src, mock_db)
 
         assert result["success"] is True
@@ -1459,8 +1464,9 @@ class TestTriggerPollGmailSource:
         }
         mock_db = MagicMock()
 
-        with patch("app.main.GmailClient", return_value=mock_gc), patch(
-            "app.main.GmailClient.load_ingested_ids", return_value=[]
+        with (
+            patch("app.main.GmailClient", return_value=mock_gc),
+            patch("app.main.GmailClient.load_ingested_ids", return_value=[]),
         ):
             _trigger_poll_gmail_source(src, mock_db)
 
@@ -1510,9 +1516,7 @@ class TestPollSourceForTrigger:
         src.id = 3
         src.name = "Gmail exc"
 
-        with patch(
-            "app.main._trigger_poll_gmail_source", side_effect=Exception("boom")
-        ):
+        with patch("app.main._trigger_poll_gmail_source", side_effect=Exception("boom")):
             result = _poll_source_for_trigger(src, MagicMock())
 
         assert result["success"] is False
@@ -1541,9 +1545,7 @@ class TestPollSourceForTrigger:
         src.id = 5
         src.name = "IMAP exc"
 
-        with patch(
-            "app.main._trigger_poll_imap_source", side_effect=Exception("imap fail")
-        ):
+        with patch("app.main._trigger_poll_imap_source", side_effect=Exception("imap fail")):
             result = _poll_source_for_trigger(src, MagicMock())
 
         assert result["success"] is False
@@ -1576,9 +1578,10 @@ class TestPollAllEnabledSources:
         mock_db = MagicMock()
         mock_db.query.return_value.filter.return_value.all.return_value = [src]
 
-        with patch("app.main.SessionLocal", return_value=mock_db), patch(
-            "app.main._poll_single_gmail_source"
-        ) as mock_gmail:
+        with (
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main._poll_single_gmail_source") as mock_gmail,
+        ):
             _poll_all_enabled_sources()
 
         mock_gmail.assert_called_once_with(src)
@@ -1594,9 +1597,10 @@ class TestPollAllEnabledSources:
         mock_db = MagicMock()
         mock_db.query.return_value.filter.return_value.all.return_value = [src]
 
-        with patch("app.main.SessionLocal", return_value=mock_db), patch(
-            "app.main._poll_single_imap_source"
-        ) as mock_imap:
+        with (
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main._poll_single_imap_source") as mock_imap,
+        ):
             _poll_all_enabled_sources()
 
         mock_imap.assert_called_once_with(src)
@@ -1612,8 +1616,9 @@ class TestPollAllEnabledSources:
         mock_db = MagicMock()
         mock_db.query.return_value.filter.return_value.all.return_value = [src]
 
-        with patch("app.main.SessionLocal", return_value=mock_db), patch(
-            "app.main._poll_single_gmail_source", side_effect=Exception("crash")
+        with (
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main._poll_single_gmail_source", side_effect=Exception("crash")),
         ):
             _poll_all_enabled_sources()  # should not raise
 
@@ -1628,8 +1633,9 @@ class TestPollAllEnabledSources:
         mock_db = MagicMock()
         mock_db.query.return_value.filter.return_value.all.return_value = [src]
 
-        with patch("app.main.SessionLocal", return_value=mock_db), patch(
-            "app.main._poll_single_imap_source", side_effect=Exception("imap crash")
+        with (
+            patch("app.main.SessionLocal", return_value=mock_db),
+            patch("app.main._poll_single_imap_source", side_effect=Exception("imap crash")),
         ):
             _poll_all_enabled_sources()  # should not raise
 
@@ -1653,8 +1659,8 @@ class TestTriggerPollEndpoint:
 
     def test_trigger_poll_with_enabled_sources(self):
         """With enabled sources, the endpoint dispatches and returns results."""
-        from app.main import app as main_app
         from app.core.security import require_admin_auth
+        from app.main import app as main_app
 
         async def mock_auth():
             return {"auth_type": "api_key"}
@@ -1681,8 +1687,9 @@ class TestTriggerPollEndpoint:
             }
 
             with TestClient(main_app) as tc:
-                with patch("app.main.SessionLocal", return_value=mock_db), patch(
-                    "app.main._poll_source_for_trigger", return_value=mock_result
+                with (
+                    patch("app.main.SessionLocal", return_value=mock_db),
+                    patch("app.main._poll_source_for_trigger", return_value=mock_result),
                 ):
                     resp = tc.post("/api/v1/admin/trigger-poll")
 
diff --git a/backend/app/tests/test_security_extra.py b/backend/app/tests/test_security_extra.py
index 48183d1..4e98290 100644
--- a/backend/app/tests/test_security_extra.py
+++ b/backend/app/tests/test_security_extra.py
@@ -15,7 +15,6 @@ from app.core.security import (
     verify_token,
 )
 
-
 # ---------------------------------------------------------------------------
 # create_access_token
 # ---------------------------------------------------------------------------
@@ -84,6 +83,16 @@ class TestVerifyToken:
 
 
 class TestRequireAdminAuth:
+    """Unit tests for the require_admin_auth dependency."""
+
+    def _make_request(self, cookies: dict = None):
+        """Build a minimal mock Request with optional cookies."""
+        from unittest.mock import MagicMock
+
+        req = MagicMock()
+        req.cookies = cookies or {}
+        return req
+
     @pytest.mark.asyncio
     async def test_valid_api_key_returns_auth_context(self):
         from app.core.security import require_admin_auth
@@ -91,7 +100,9 @@ class TestRequireAdminAuth:
         key = generate_api_key()
         add_api_key(key)
         try:
-            result = await require_admin_auth(api_key=key, bearer=None)
+            result = await require_admin_auth(
+                request=self._make_request(), api_key=key, bearer=None
+            )
             assert result["auth_type"] == "api_key"
         finally:
             from app.core.security import _api_keys
@@ -106,7 +117,7 @@ class TestRequireAdminAuth:
         from fastapi.security import HTTPAuthorizationCredentials
 
         creds = HTTPAuthorizationCredentials(scheme="Bearer", credentials=token)
-        result = await require_admin_auth(api_key=None, bearer=creds)
+        result = await require_admin_auth(request=self._make_request(), api_key=None, bearer=creds)
         assert result["auth_type"] == "jwt"
         assert result["payload"]["sub"] == "admin-user"
 
@@ -117,11 +128,9 @@ class TestRequireAdminAuth:
 
         from app.core.security import require_admin_auth
 
-        creds = HTTPAuthorizationCredentials(
-            scheme="Bearer", credentials="bad.token.value"
-        )
+        creds = HTTPAuthorizationCredentials(scheme="Bearer", credentials="bad.token.value")
         with pytest.raises(HTTPException) as exc_info:
-            await require_admin_auth(api_key=None, bearer=creds)
+            await require_admin_auth(request=self._make_request(), api_key=None, bearer=creds)
         assert exc_info.value.status_code == 401
 
     @pytest.mark.asyncio
@@ -131,9 +140,24 @@ class TestRequireAdminAuth:
         from app.core.security import require_admin_auth
 
         with pytest.raises(HTTPException) as exc_info:
-            await require_admin_auth(api_key=None, bearer=None)
+            await require_admin_auth(request=self._make_request(), api_key=None, bearer=None)
         assert exc_info.value.status_code == 401
 
+    @pytest.mark.asyncio
+    async def test_valid_session_cookie_returns_auth_context(self):
+        """A valid dmarq_session cookie should authenticate successfully."""
+        from app.core.logto import create_session_token
+        from app.core.security import require_admin_auth
+
+        token = create_session_token(user_id=42)
+        result = await require_admin_auth(
+            request=self._make_request(cookies={"dmarq_session": token}),
+            api_key=None,
+            bearer=None,
+        )
+        assert result["auth_type"] == "session"
+        assert result["user_id"] == 42
+
 
 # ---------------------------------------------------------------------------
 # get_api_key dependency
diff --git a/backend/app/tests/test_stats_endpoints.py b/backend/app/tests/test_stats_endpoints.py
index bdf5e35..6a970dd 100644
--- a/backend/app/tests/test_stats_endpoints.py
+++ b/backend/app/tests/test_stats_endpoints.py
@@ -89,18 +89,14 @@ class TestDomainStatistics:
         response = client.get("/api/v1/stats/domain/example.com?force_refresh=true")
         assert response.status_code == 200
 
-    def test_domain_stats_force_refresh_calls_invalidate_with_domain(
-        self, client: TestClient
-    ):
+    def test_domain_stats_force_refresh_calls_invalidate_with_domain(self, client: TestClient):
         """Verify invalidate_cache is called with the domain ID."""
         with patch("app.api.api_v1.endpoints.stats.StatsSummarizer") as MockSummarizer:
             mock_instance = MagicMock()
             mock_instance.calculate_summary_statistics.return_value = {"total": 0}
             MockSummarizer.return_value = mock_instance
 
-            response = client.get(
-                "/api/v1/stats/domain/example.com?force_refresh=true"
-            )
+            response = client.get("/api/v1/stats/domain/example.com?force_refresh=true")
             assert response.status_code == 200
             mock_instance.invalidate_cache.assert_called_once_with("example.com")
 
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 058cde9..8e82af1 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -1,18 +1,13 @@
 fastapi>=0.96.0
 uvicorn>=0.22.0
 sqlalchemy>=2.0.0
-aiosqlite>=0.19.0
-asyncpg>=0.27.0
 pydantic>=2.0.0
 pydantic-settings>=2.0.0
 python-jose[cryptography]>=3.3.0
 passlib[bcrypt]>=1.7.4
 python-multipart>=0.0.6
-fastapi-users[sqlalchemy]>=15.0.0
-fastapi-users-db-sqlalchemy>=7.0.0
-httpx-oauth>=0.14.0
-pyotp>=2.8.0
-qrcode[pil]>=7.4.0
+logto>=0.2.0
+aiohttp>=3.8.0
 alembic>=1.11.0
 pytest>=7.3.1
 pytest-asyncio>=0.21.0