diff --git a/enterprise/migrations/versions/094_create_org_invitation_table.py b/enterprise/migrations/versions/094_create_org_invitation_table.py
new file mode 100644
index 0000000000..3dc6a2f89a
--- /dev/null
+++ b/enterprise/migrations/versions/094_create_org_invitation_table.py
@@ -0,0 +1,110 @@
+"""create org_invitation table
+
+Revision ID: 094
+Revises: 093
+Create Date: 2026-02-18 00:00:00.000000
+
+"""
+
+from typing import Sequence, Union
+
+import sqlalchemy as sa
+from alembic import op
+from sqlalchemy.dialects import postgresql
+
+# revision identifiers, used by Alembic.
+revision: str = '094'
+down_revision: Union[str, None] = '093'
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    # Create org_invitation table
+    op.create_table(
+        'org_invitation',
+        sa.Column('id', sa.Integer, sa.Identity(), primary_key=True),
+        sa.Column('token', sa.String(64), nullable=False),
+        sa.Column('org_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column('email', sa.String(255), nullable=False),
+        sa.Column('role_id', sa.Integer, nullable=False),
+        sa.Column('inviter_id', postgresql.UUID(as_uuid=True), nullable=False),
+        sa.Column(
+            'status',
+            sa.String(20),
+            nullable=False,
+            server_default=sa.text("'pending'"),
+        ),
+        sa.Column(
+            'created_at',
+            sa.DateTime,
+            nullable=False,
+            server_default=sa.text('CURRENT_TIMESTAMP'),
+        ),
+        sa.Column('expires_at', sa.DateTime, nullable=False),
+        sa.Column('accepted_at', sa.DateTime, nullable=True),
+        sa.Column('accepted_by_user_id', postgresql.UUID(as_uuid=True), nullable=True),
+        # Foreign key constraints
+        sa.ForeignKeyConstraint(
+            ['org_id'],
+            ['org.id'],
+            name='org_invitation_org_fkey',
+            ondelete='CASCADE',
+        ),
+        sa.ForeignKeyConstraint(
+            ['role_id'],
+            ['role.id'],
+            name='org_invitation_role_fkey',
+        ),
+        sa.ForeignKeyConstraint(
+            ['inviter_id'],
+            ['user.id'],
+            name='org_invitation_inviter_fkey',
+        ),
+        sa.ForeignKeyConstraint(
+            ['accepted_by_user_id'],
+            ['user.id'],
+            name='org_invitation_accepter_fkey',
+        ),
+    )
+
+    # Create indexes
+    op.create_index(
+        'ix_org_invitation_token',
+        'org_invitation',
+        ['token'],
+        unique=True,
+    )
+    op.create_index(
+        'ix_org_invitation_org_id',
+        'org_invitation',
+        ['org_id'],
+    )
+    op.create_index(
+        'ix_org_invitation_email',
+        'org_invitation',
+        ['email'],
+    )
+    op.create_index(
+        'ix_org_invitation_status',
+        'org_invitation',
+        ['status'],
+    )
+    # Composite index for checking pending invitations
+    op.create_index(
+        'ix_org_invitation_org_email_status',
+        'org_invitation',
+        ['org_id', 'email', 'status'],
+    )
+
+
+def downgrade() -> None:
+    # Drop indexes
+    op.drop_index('ix_org_invitation_org_email_status', table_name='org_invitation')
+    op.drop_index('ix_org_invitation_status', table_name='org_invitation')
+    op.drop_index('ix_org_invitation_email', table_name='org_invitation')
+    op.drop_index('ix_org_invitation_org_id', table_name='org_invitation')
+    op.drop_index('ix_org_invitation_token', table_name='org_invitation')
+
+    # Drop table
+    op.drop_table('org_invitation')
diff --git a/enterprise/saas_server.py b/enterprise/saas_server.py
index e8c1935cb5..2248892993 100644
--- a/enterprise/saas_server.py
+++ b/enterprise/saas_server.py
@@ -38,6 +38,12 @@ from server.routes.integration.linear import linear_integration_router  # noqa:
 from server.routes.integration.slack import slack_router  # noqa: E402
 from server.routes.mcp_patch import patch_mcp_server  # noqa: E402
 from server.routes.oauth_device import oauth_device_router  # noqa: E402
+from server.routes.org_invitations import (  # noqa: E402
+    accept_router as invitation_accept_router,
+)
+from server.routes.org_invitations import (  # noqa: E402
+    invitation_router,
+)
 from server.routes.orgs import org_router  # noqa: E402
 from server.routes.readiness import readiness_router  # noqa: E402
 from server.routes.user import saas_user_router  # noqa: E402
@@ -99,6 +105,8 @@ if GITLAB_APP_CLIENT_ID:
 
 base_app.include_router(api_keys_router)  # Add routes for API key management
 base_app.include_router(org_router)  # Add routes for organization management
+base_app.include_router(invitation_router)  # Add routes for org invitation management
+base_app.include_router(invitation_accept_router)  # Add route for accepting invitations
 add_github_proxy_routes(base_app)
 add_debugging_routes(
     base_app
diff --git a/enterprise/server/middleware.py b/enterprise/server/middleware.py
index 651cd45512..c3d12c7897 100644
--- a/enterprise/server/middleware.py
+++ b/enterprise/server/middleware.py
@@ -160,6 +160,7 @@ class SetAuthCookieMiddleware:
             '/api/billing/customer-setup-success',
             '/api/billing/stripe-webhook',
             '/api/email/resend',
+            '/api/organizations/members/invite/accept',
             '/oauth/device/authorize',
             '/oauth/device/token',
             '/api/v1/web-client/config',
diff --git a/enterprise/server/routes/auth.py b/enterprise/server/routes/auth.py
index 15479bbdaa..75eb8b440f 100644
--- a/enterprise/server/routes/auth.py
+++ b/enterprise/server/routes/auth.py
@@ -5,6 +5,7 @@ import warnings
 from datetime import datetime, timezone
 from typing import Annotated, Literal, Optional
 from urllib.parse import quote
+from uuid import UUID as parse_uuid
 
 import posthog
 from fastapi import APIRouter, Header, HTTPException, Request, Response, status
@@ -26,6 +27,13 @@ from server.auth.token_manager import TokenManager
 from server.config import sign_token
 from server.constants import IS_FEATURE_ENV
 from server.routes.event_webhook import _get_session_api_key, _get_user_id
+from server.services.org_invitation_service import (
+    EmailMismatchError,
+    InvitationExpiredError,
+    InvitationInvalidError,
+    OrgInvitationService,
+    UserAlreadyMemberError,
+)
 from storage.database import session_maker
 from storage.user import User
 from storage.user_store import UserStore
@@ -104,22 +112,40 @@ def get_cookie_samesite(request: Request) -> Literal['lax', 'strict']:
     )
 
 
+def _extract_oauth_state(state: str | None) -> tuple[str, str | None, str | None]:
+    """Extract redirect URL, reCAPTCHA token, and invitation token from OAuth state.
+
+    Returns:
+        Tuple of (redirect_url, recaptcha_token, invitation_token).
+        Tokens may be None.
+    """
+    if not state:
+        return '', None, None
+
+    try:
+        # Try to decode as JSON (new format with reCAPTCHA and/or invitation)
+        state_data = json.loads(base64.urlsafe_b64decode(state.encode()).decode())
+        return (
+            state_data.get('redirect_url', ''),
+            state_data.get('recaptcha_token'),
+            state_data.get('invitation_token'),
+        )
+    except Exception:
+        # Old format - state is just the redirect URL
+        return state, None, None
+
+
+# Keep alias for backward compatibility
 def _extract_recaptcha_state(state: str | None) -> tuple[str, str | None]:
     """Extract redirect URL and reCAPTCHA token from OAuth state.
 
+    Deprecated: Use _extract_oauth_state instead.
+
     Returns:
         Tuple of (redirect_url, recaptcha_token). Token may be None.
     """
-    if not state:
-        return '', None
-
-    try:
-        # Try to decode as JSON (new format with reCAPTCHA)
-        state_data = json.loads(base64.urlsafe_b64decode(state.encode()).decode())
-        return state_data.get('redirect_url', ''), state_data.get('recaptcha_token')
-    except Exception:
-        # Old format - state is just the redirect URL
-        return state, None
+    redirect_url, recaptcha_token, _ = _extract_oauth_state(state)
+    return redirect_url, recaptcha_token
 
 
 @oauth_router.get('/keycloak/callback')
@@ -130,8 +156,8 @@ async def keycloak_callback(
     error: Optional[str] = None,
     error_description: Optional[str] = None,
 ):
-    # Extract redirect URL and reCAPTCHA token from state
-    redirect_url, recaptcha_token = _extract_recaptcha_state(state)
+    # Extract redirect URL, reCAPTCHA token, and invitation token from state
+    redirect_url, recaptcha_token, invitation_token = _extract_oauth_state(state)
     if not redirect_url:
         redirect_url = str(request.base_url)
 
@@ -302,8 +328,13 @@ async def keycloak_callback(
         from server.routes.email import verify_email
 
         await verify_email(request=request, user_id=user_id, is_auth_flow=True)
-        redirect_url = f'{request.base_url}login?email_verification_required=true&user_id={user_id}'
-        response = RedirectResponse(redirect_url, status_code=302)
+        verification_redirect_url = f'{request.base_url}login?email_verification_required=true&user_id={user_id}'
+        # Preserve invitation token so it can be included in OAuth state after verification
+        if invitation_token:
+            verification_redirect_url = (
+                f'{verification_redirect_url}&invitation_token={invitation_token}'
+            )
+        response = RedirectResponse(verification_redirect_url, status_code=302)
         return response
 
     # default to github IDP for now.
@@ -381,14 +412,90 @@ async def keycloak_callback(
         )
 
     has_accepted_tos = user.accepted_tos is not None
+
+    # Process invitation token if present (after email verification but before TOS)
+    if invitation_token:
+        try:
+            logger.info(
+                'Processing invitation token during auth callback',
+                extra={
+                    'user_id': user_id,
+                    'invitation_token_prefix': invitation_token[:10] + '...',
+                },
+            )
+
+            await OrgInvitationService.accept_invitation(
+                invitation_token, parse_uuid(user_id)
+            )
+            logger.info(
+                'Invitation accepted during auth callback',
+                extra={'user_id': user_id},
+            )
+
+        except InvitationExpiredError:
+            logger.warning(
+                'Invitation expired during auth callback',
+                extra={'user_id': user_id},
+            )
+            # Add query param to redirect URL
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&invitation_expired=true'
+            else:
+                redirect_url = f'{redirect_url}?invitation_expired=true'
+
+        except InvitationInvalidError as e:
+            logger.warning(
+                'Invalid invitation during auth callback',
+                extra={'user_id': user_id, 'error': str(e)},
+            )
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&invitation_invalid=true'
+            else:
+                redirect_url = f'{redirect_url}?invitation_invalid=true'
+
+        except UserAlreadyMemberError:
+            logger.info(
+                'User already member during invitation acceptance',
+                extra={'user_id': user_id},
+            )
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&already_member=true'
+            else:
+                redirect_url = f'{redirect_url}?already_member=true'
+
+        except EmailMismatchError as e:
+            logger.warning(
+                'Email mismatch during auth callback invitation acceptance',
+                extra={'user_id': user_id, 'error': str(e)},
+            )
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&email_mismatch=true'
+            else:
+                redirect_url = f'{redirect_url}?email_mismatch=true'
+
+        except Exception as e:
+            logger.exception(
+                'Unexpected error processing invitation during auth callback',
+                extra={'user_id': user_id, 'error': str(e)},
+            )
+            # Don't fail the login if invitation processing fails
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&invitation_error=true'
+            else:
+                redirect_url = f'{redirect_url}?invitation_error=true'
+
     # If the user hasn't accepted the TOS, redirect to the TOS page
     if not has_accepted_tos:
         encoded_redirect_url = quote(redirect_url, safe='')
         tos_redirect_url = (
             f'{request.base_url}accept-tos?redirect_url={encoded_redirect_url}'
         )
+        if invitation_token:
+            tos_redirect_url = f'{tos_redirect_url}&invitation_success=true'
         response = RedirectResponse(tos_redirect_url, status_code=302)
     else:
+        if invitation_token:
+            redirect_url = f'{redirect_url}&invitation_success=true'
         response = RedirectResponse(redirect_url, status_code=302)
 
     set_response_cookie(
diff --git a/enterprise/server/routes/org_invitation_models.py b/enterprise/server/routes/org_invitation_models.py
new file mode 100644
index 0000000000..3852959a68
--- /dev/null
+++ b/enterprise/server/routes/org_invitation_models.py
@@ -0,0 +1,122 @@
+"""
+Pydantic models and custom exceptions for organization invitations.
+"""
+
+from pydantic import BaseModel, EmailStr
+from storage.org_invitation import OrgInvitation
+from storage.role_store import RoleStore
+
+
+class InvitationError(Exception):
+    """Base exception for invitation errors."""
+
+    pass
+
+
+class InvitationAlreadyExistsError(InvitationError):
+    """Raised when a pending invitation already exists for the email."""
+
+    def __init__(
+        self, message: str = 'A pending invitation already exists for this email'
+    ):
+        super().__init__(message)
+
+
+class UserAlreadyMemberError(InvitationError):
+    """Raised when the user is already a member of the organization."""
+
+    def __init__(self, message: str = 'User is already a member of this organization'):
+        super().__init__(message)
+
+
+class InvitationExpiredError(InvitationError):
+    """Raised when the invitation has expired."""
+
+    def __init__(self, message: str = 'Invitation has expired'):
+        super().__init__(message)
+
+
+class InvitationInvalidError(InvitationError):
+    """Raised when the invitation is invalid or revoked."""
+
+    def __init__(self, message: str = 'Invitation is no longer valid'):
+        super().__init__(message)
+
+
+class InsufficientPermissionError(InvitationError):
+    """Raised when the user lacks permission to perform the action."""
+
+    def __init__(self, message: str = 'Insufficient permission'):
+        super().__init__(message)
+
+
+class EmailMismatchError(InvitationError):
+    """Raised when the accepting user's email doesn't match the invitation email."""
+
+    def __init__(self, message: str = 'Your email does not match the invitation'):
+        super().__init__(message)
+
+
+class InvitationCreate(BaseModel):
+    """Request model for creating invitation(s)."""
+
+    emails: list[EmailStr]
+    role: str = 'member'  # Default to member role
+
+
+class InvitationResponse(BaseModel):
+    """Response model for invitation details."""
+
+    id: int
+    email: str
+    role: str
+    status: str
+    created_at: str
+    expires_at: str
+    inviter_email: str | None = None
+
+    @classmethod
+    def from_invitation(
+        cls,
+        invitation: OrgInvitation,
+        inviter_email: str | None = None,
+    ) -> 'InvitationResponse':
+        """Create an InvitationResponse from an OrgInvitation entity.
+
+        Args:
+            invitation: The invitation entity to convert
+            inviter_email: Optional email of the inviter
+
+        Returns:
+            InvitationResponse: The response model instance
+        """
+        role_name = ''
+        if invitation.role:
+            role_name = invitation.role.name
+        elif invitation.role_id:
+            role = RoleStore.get_role_by_id(invitation.role_id)
+            role_name = role.name if role else ''
+
+        return cls(
+            id=invitation.id,
+            email=invitation.email,
+            role=role_name,
+            status=invitation.status,
+            created_at=invitation.created_at.isoformat(),
+            expires_at=invitation.expires_at.isoformat(),
+            inviter_email=inviter_email,
+        )
+
+
+class InvitationFailure(BaseModel):
+    """Response model for a failed invitation."""
+
+    email: str
+    error: str
+
+
+class BatchInvitationResponse(BaseModel):
+    """Response model for batch invitation creation."""
+
+    successful: list[InvitationResponse]
+    failed: list[InvitationFailure]
diff --git a/enterprise/server/routes/org_invitations.py b/enterprise/server/routes/org_invitations.py
new file mode 100644
index 0000000000..3349d600ac
--- /dev/null
+++ b/enterprise/server/routes/org_invitations.py
@@ -0,0 +1,226 @@
+"""API routes for organization invitations."""
+
+from uuid import UUID
+
+from fastapi import APIRouter, Depends, HTTPException, Request, status
+from fastapi.responses import RedirectResponse
+from server.routes.org_invitation_models import (
+    BatchInvitationResponse,
+    EmailMismatchError,
+    InsufficientPermissionError,
+    InvitationCreate,
+    InvitationExpiredError,
+    InvitationFailure,
+    InvitationInvalidError,
+    InvitationResponse,
+    UserAlreadyMemberError,
+)
+from server.services.org_invitation_service import OrgInvitationService
+from server.utils.rate_limit_utils import check_rate_limit_by_user_id
+
+from openhands.core.logger import openhands_logger as logger
+from openhands.server.user_auth import get_user_id
+from openhands.server.user_auth.user_auth import get_user_auth
+
+# Router for invitation operations on an organization (requires org_id)
+invitation_router = APIRouter(prefix='/api/organizations/{org_id}/members')
+
+# Router for accepting invitations (no org_id required)
+accept_router = APIRouter(prefix='/api/organizations/members/invite')
+
+
+@invitation_router.post(
+    '/invite',
+    response_model=BatchInvitationResponse,
+    status_code=status.HTTP_201_CREATED,
+)
+async def create_invitation(
+    org_id: UUID,
+    invitation_data: InvitationCreate,
+    request: Request,
+    user_id: str = Depends(get_user_id),
+):
+    """Create organization invitations for multiple email addresses.
+
+    Sends emails to invitees with secure links to join the organization.
+    Supports batch invitations - some may succeed while others fail.
+
+    Permission rules:
+    - Only owners and admins can create invitations
+    - Admins can only invite with 'member' or 'admin' role (not 'owner')
+    - Owners can invite with any role
+
+    Args:
+        org_id: Organization UUID
+        invitation_data: Invitation details (emails array, role)
+        request: FastAPI request
+        user_id: Authenticated user ID (from dependency)
+
+    Returns:
+        BatchInvitationResponse: Lists of successful and failed invitations
+
+    Raises:
+        HTTPException 400: Invalid role or organization not found
+        HTTPException 403: User lacks permission to invite
+        HTTPException 429: Rate limit exceeded
+    """
+    # Rate limit: 10 invitations per minute per user (6 seconds between requests)
+    await check_rate_limit_by_user_id(
+        request=request,
+        key_prefix='org_invitation_create',
+        user_id=user_id,
+        user_rate_limit_seconds=6,
+    )
+
+    try:
+        successful, failed = await OrgInvitationService.create_invitations_batch(
+            org_id=org_id,
+            emails=[str(email) for email in invitation_data.emails],
+            role_name=invitation_data.role,
+            inviter_id=UUID(user_id),
+        )
+
+        logger.info(
+            'Batch organization invitations created',
+            extra={
+                'org_id': str(org_id),
+                'total_emails': len(invitation_data.emails),
+                'successful': len(successful),
+                'failed': len(failed),
+                'inviter_id': user_id,
+            },
+        )
+
+        return BatchInvitationResponse(
+            successful=[InvitationResponse.from_invitation(inv) for inv in successful],
+            failed=[
+                InvitationFailure(email=email, error=error) for email, error in failed
+            ],
+        )
+
+    except InsufficientPermissionError as e:
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail=str(e),
+        )
+    except ValueError as e:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=str(e),
+        )
+    except Exception as e:
+        logger.exception(
+            'Unexpected error creating batch invitations',
+            extra={'org_id': str(org_id), 'error': str(e)},
+        )
+        raise HTTPException(
+            status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+            detail='An unexpected error occurred',
+        )
+
+
+@accept_router.get('/accept')
+async def accept_invitation(
+    token: str,
+    request: Request,
+):
+    """Accept an organization invitation via token.
+
+    This endpoint is accessed via the link in the invitation email.
+
+    Flow:
+    1. If user is authenticated: Accept invitation directly and redirect to home
+    2. If user is not authenticated: Redirect to login page with invitation token
+       - Frontend stores token and includes it in OAuth state during login
+       - After authentication, keycloak_callback processes the invitation
+
+    Args:
+        token: The invitation token from the email link
+        request: FastAPI request
+
+    Returns:
+        RedirectResponse: Redirect to home page on success, or login page if not authenticated,
+                         or home page with error query params on failure
+    """
+    base_url = str(request.base_url).rstrip('/')
+
+    # Try to get user_id from auth (may not be authenticated)
+    user_id = None
+    try:
+        user_auth = await get_user_auth(request)
+        if user_auth:
+            user_id = await user_auth.get_user_id()
+    except Exception:
+        pass
+
+    if not user_id:
+        # User not authenticated - redirect to login page with invitation token
+        # Frontend will store the token and include it in OAuth state during login
+        logger.info(
+            'Invitation accept: redirecting unauthenticated user to login',
+            extra={'token_prefix': token[:10] + '...'},
+        )
+        login_url = f'{base_url}/login?invitation_token={token}'
+        return RedirectResponse(login_url, status_code=302)
+
+    # User is authenticated - process the invitation directly
+    try:
+        await OrgInvitationService.accept_invitation(token, UUID(user_id))
+
+        logger.info(
+            'Invitation accepted successfully',
+            extra={
+                'token_prefix': token[:10] + '...',
+                'user_id': user_id,
+            },
+        )
+
+        # Redirect to home page on success
+        return RedirectResponse(f'{base_url}/', status_code=302)
+
+    except InvitationExpiredError:
+        logger.warning(
+            'Invitation accept failed: expired',
+            extra={'token_prefix': token[:10] + '...', 'user_id': user_id},
+        )
+        return RedirectResponse(f'{base_url}/?invitation_expired=true', status_code=302)
+
+    except InvitationInvalidError as e:
+        logger.warning(
+            'Invitation accept failed: invalid',
+            extra={
+                'token_prefix': token[:10] + '...',
+                'user_id': user_id,
+                'error': str(e),
+            },
+        )
+        return RedirectResponse(f'{base_url}/?invitation_invalid=true', status_code=302)
+
+    except UserAlreadyMemberError:
+        logger.info(
+            'Invitation accept: user already member',
+            extra={'token_prefix': token[:10] + '...', 'user_id': user_id},
+        )
+        return RedirectResponse(f'{base_url}/?already_member=true', status_code=302)
+
+    except EmailMismatchError as e:
+        logger.warning(
+            'Invitation accept failed: email mismatch',
+            extra={
+                'token_prefix': token[:10] + '...',
+                'user_id': user_id,
+                'error': str(e),
+            },
+        )
+        return RedirectResponse(f'{base_url}/?email_mismatch=true', status_code=302)
+
+    except Exception as e:
+        logger.exception(
+            'Unexpected error accepting invitation',
+            extra={
+                'token_prefix': token[:10] + '...',
+                'user_id': user_id,
+                'error': str(e),
+            },
+        )
+        return RedirectResponse(f'{base_url}/?invitation_error=true', status_code=302)
diff --git a/enterprise/server/services/email_service.py b/enterprise/server/services/email_service.py
new file mode 100644
index 0000000000..163671b617
--- /dev/null
+++ b/enterprise/server/services/email_service.py
@@ -0,0 +1,131 @@
+"""Email service for sending transactional emails via Resend."""
+
+import os
+
+try:
+    import resend
+
+    RESEND_AVAILABLE = True
+except ImportError:
+    RESEND_AVAILABLE = False
+
+from openhands.core.logger import openhands_logger as logger
+
+DEFAULT_FROM_EMAIL = 'OpenHands <no-reply@openhands.dev>'
+DEFAULT_WEB_HOST = 'https://app.all-hands.dev'
+
+
+class EmailService:
+    """Service for sending transactional emails."""
+
+    @staticmethod
+    def _get_resend_client() -> bool:
+        """Initialize and return the Resend client.
+
+        Returns:
+            bool: True if client is ready, False otherwise
+        """
+        if not RESEND_AVAILABLE:
+            logger.warning('Resend library not installed, skipping email')
+            return False
+
+        resend_api_key = os.environ.get('RESEND_API_KEY')
+        if not resend_api_key:
+            logger.warning('RESEND_API_KEY not configured, skipping email')
+            return False
+
+        resend.api_key = resend_api_key
+        return True
+
+    @staticmethod
+    def send_invitation_email(
+        to_email: str,
+        org_name: str,
+        inviter_name: str,
+        role_name: str,
+        invitation_token: str,
+        invitation_id: int,
+    ) -> None:
+        """Send an organization invitation email.
+
+        Args:
+            to_email: Recipient's email address
+            org_name: Name of the organization
+            inviter_name: Display name of the person who sent the invite
+            role_name: Role being offered (e.g., 'member', 'admin')
+            invitation_token: The secure invitation token
+            invitation_id: The invitation ID for logging
+        """
+        if not EmailService._get_resend_client():
+            return
+
+        # Build invitation URL
+        web_host = os.environ.get('WEB_HOST', DEFAULT_WEB_HOST)
+        invitation_url = f'{web_host}/api/organizations/members/invite/accept?token={invitation_token}'
+
+        from_email = os.environ.get('RESEND_FROM_EMAIL', DEFAULT_FROM_EMAIL)
+
+        params = {
+            'from': from_email,
+            'to': [to_email],
+            'subject': f"You're invited to join {org_name} on OpenHands",
+            'html': f"""
+            <div style="font-family: Arial, sans-serif; max-width: 600px; margin: 0 auto;">
+                <p>Hi,</p>
+
+                <p><strong>{inviter_name}</strong> has invited you to join <strong>{org_name}</strong> on OpenHands as a <strong>{role_name}</strong>.</p>
+
+                <p>Click the button below to accept the invitation:</p>
+
+                <p style="margin: 30px 0;">
+                    <a href="{invitation_url}"
+                       style="background-color: #c9b974; color: #0D0F11; padding: 8px 16px;
+                              text-decoration: none; border-radius: 8px; display: inline-block;
+                              font-size: 14px; font-weight: 600;">
+                        Accept Invitation
+                    </a>
+                </p>
+
+                <p style="color: #666; font-size: 14px;">
+                    Or copy and paste this link into your browser:<br>
+                    <a href="{invitation_url}" style="color: #c9b974; font-weight: 600;">{invitation_url}</a>
+                </p>
+
+                <p style="color: #666; font-size: 14px;">
+                    This invitation will expire in 7 days.
+                </p>
+
+                <p style="color: #666; font-size: 14px;">
+                    If you weren't expecting this invitation, you can safely ignore this email.
+                </p>
+
+                <hr style="border: none; border-top: 1px solid #eee; margin: 30px 0;">
+
+                <p style="color: #999; font-size: 12px;">
+                    Best,<br>
+                    The OpenHands Team
+                </p>
+            </div>
+            """,
+        }
+
+        try:
+            response = resend.Emails.send(params)
+            logger.info(
+                'Invitation email sent',
+                extra={
+                    'invitation_id': invitation_id,
+                    'email': to_email,
+                    'response_id': response.get('id') if response else None,
+                },
+            )
+        except Exception as e:
+            logger.error(
+                'Failed to send invitation email',
+                extra={
+                    'invitation_id': invitation_id,
+                    'email': to_email,
+                    'error': str(e),
+                },
+            )
+            raise
diff --git a/enterprise/server/services/org_invitation_service.py b/enterprise/server/services/org_invitation_service.py
new file mode 100644
index 0000000000..e31e43c61f
--- /dev/null
+++ b/enterprise/server/services/org_invitation_service.py
@@ -0,0 +1,397 @@
+"""Service for managing organization invitations."""
+
+import asyncio
+from uuid import UUID
+
+from server.auth.token_manager import TokenManager
+from server.constants import ROLE_ADMIN, ROLE_OWNER
+from server.routes.org_invitation_models import (
+    EmailMismatchError,
+    InsufficientPermissionError,
+    InvitationExpiredError,
+    InvitationInvalidError,
+    UserAlreadyMemberError,
+)
+from server.services.email_service import EmailService
+from storage.org_invitation import OrgInvitation
+from storage.org_invitation_store import OrgInvitationStore
+from storage.org_member_store import OrgMemberStore
+from storage.org_service import OrgService
+from storage.org_store import OrgStore
+from storage.role_store import RoleStore
+from storage.user_store import UserStore
+
+from openhands.core.logger import openhands_logger as logger
+
+
+class OrgInvitationService:
+    """Service for organization invitation operations."""
+
+    @staticmethod
+    async def create_invitation(
+        org_id: UUID,
+        email: str,
+        role_name: str,
+        inviter_id: UUID,
+    ) -> OrgInvitation:
+        """Create a new organization invitation.
+
+        This method:
+        1. Validates the organization exists
+        2. Validates this is not a personal workspace
+        3. Checks inviter has owner/admin role
+        4. Validates role assignment permissions
+        5. Checks if user is already a member
+        6. Creates the invitation
+        7. Sends the invitation email
+
+        Args:
+            org_id: Organization UUID
+            email: Invitee's email address
+            role_name: Role to assign on acceptance (owner, admin, member)
+            inviter_id: User ID of the person creating the invitation
+
+        Returns:
+            OrgInvitation: The created invitation
+
+        Raises:
+            ValueError: If organization or role not found
+            InsufficientPermissionError: If inviter lacks permission
+            UserAlreadyMemberError: If email is already a member
+            InvitationAlreadyExistsError: If pending invitation exists
+        """
+        email = email.lower().strip()
+
+        logger.info(
+            'Creating organization invitation',
+            extra={
+                'org_id': str(org_id),
+                'email': email,
+                'role_name': role_name,
+                'inviter_id': str(inviter_id),
+            },
+        )
+
+        # Step 1: Validate organization exists
+        org = OrgStore.get_org_by_id(org_id)
+        if not org:
+            raise ValueError(f'Organization {org_id} not found')
+
+        # Step 2: Check this is not a personal workspace
+        # A personal workspace has org_id matching the user's id
+        if str(org_id) == str(inviter_id):
+            raise InsufficientPermissionError(
+                'Cannot invite users to a personal workspace'
+            )
+
+        # Step 3: Check inviter is a member and has permission
+        inviter_member = OrgMemberStore.get_org_member(org_id, inviter_id)
+        if not inviter_member:
+            raise InsufficientPermissionError(
+                'You are not a member of this organization'
+            )
+
+        inviter_role = RoleStore.get_role_by_id(inviter_member.role_id)
+        if not inviter_role or inviter_role.name not in [ROLE_OWNER, ROLE_ADMIN]:
+            raise InsufficientPermissionError('Only owners and admins can invite users')
+
+        # Step 4: Validate role assignment permissions
+        role_name_lower = role_name.lower()
+        if role_name_lower == ROLE_OWNER and inviter_role.name != ROLE_OWNER:
+            raise InsufficientPermissionError('Only owners can invite with owner role')
+
+        # Get the target role
+        target_role = RoleStore.get_role_by_name(role_name_lower)
+        if not target_role:
+            raise ValueError(f'Invalid role: {role_name}')
+
+        # Step 5: Check if user is already a member (by email)
+        existing_user = await UserStore.get_user_by_email_async(email)
+        if existing_user:
+            existing_member = OrgMemberStore.get_org_member(org_id, existing_user.id)
+            if existing_member:
+                raise UserAlreadyMemberError(
+                    'User is already a member of this organization'
+                )
+
+        # Step 6: Create the invitation
+        invitation = await OrgInvitationStore.create_invitation(
+            org_id=org_id,
+            email=email,
+            role_id=target_role.id,
+            inviter_id=inviter_id,
+        )
+
+        # Step 7: Send invitation email
+        try:
+            # Get inviter info for the email
+            inviter_user = UserStore.get_user_by_id(str(inviter_member.user_id))
+            inviter_name = 'A team member'
+            if inviter_user and inviter_user.email:
+                inviter_name = inviter_user.email.split('@')[0]
+
+            EmailService.send_invitation_email(
+                to_email=email,
+                org_name=org.name,
+                inviter_name=inviter_name,
+                role_name=target_role.name,
+                invitation_token=invitation.token,
+                invitation_id=invitation.id,
+            )
+        except Exception as e:
+            logger.error(
+                'Failed to send invitation email',
+                extra={
+                    'invitation_id': invitation.id,
+                    'email': email,
+                    'error': str(e),
+                },
+            )
+            # Don't fail the invitation creation if email fails
+            # The user can still access via direct link
+
+        return invitation
+
+    @staticmethod
+    async def create_invitations_batch(
+        org_id: UUID,
+        emails: list[str],
+        role_name: str,
+        inviter_id: UUID,
+    ) -> tuple[list[OrgInvitation], list[tuple[str, str]]]:
+        """Create multiple organization invitations concurrently.
+
+        Validates permissions once upfront, then creates invitations in parallel.
+
+        Args:
+            org_id: Organization UUID
+            emails: List of invitee email addresses
+            role_name: Role to assign on acceptance (owner, admin, member)
+            inviter_id: User ID of the person creating the invitations
+
+        Returns:
+            Tuple of (successful_invitations, failed_emails_with_errors)
+
+        Raises:
+            ValueError: If organization or role not found
+            InsufficientPermissionError: If inviter lacks permission
+        """
+        logger.info(
+            'Creating batch organization invitations',
+            extra={
+                'org_id': str(org_id),
+                'email_count': len(emails),
+                'role_name': role_name,
+                'inviter_id': str(inviter_id),
+            },
+        )
+
+        # Step 1: Validate permissions upfront (shared for all emails)
+        org = OrgStore.get_org_by_id(org_id)
+        if not org:
+            raise ValueError(f'Organization {org_id} not found')
+
+        if str(org_id) == str(inviter_id):
+            raise InsufficientPermissionError(
+                'Cannot invite users to a personal workspace'
+            )
+
+        inviter_member = OrgMemberStore.get_org_member(org_id, inviter_id)
+        if not inviter_member:
+            raise InsufficientPermissionError(
+                'You are not a member of this organization'
+            )
+
+        inviter_role = RoleStore.get_role_by_id(inviter_member.role_id)
+        if not inviter_role or inviter_role.name not in [ROLE_OWNER, ROLE_ADMIN]:
+            raise InsufficientPermissionError('Only owners and admins can invite users')
+
+        role_name_lower = role_name.lower()
+        if role_name_lower == ROLE_OWNER and inviter_role.name != ROLE_OWNER:
+            raise InsufficientPermissionError('Only owners can invite with owner role')
+
+        target_role = RoleStore.get_role_by_name(role_name_lower)
+        if not target_role:
+            raise ValueError(f'Invalid role: {role_name}')
+
+        # Step 2: Create invitations concurrently
+        async def create_single(
+            email: str,
+        ) -> tuple[str, OrgInvitation | None, str | None]:
+            """Create single invitation, return (email, invitation, error)."""
+            try:
+                invitation = await OrgInvitationService.create_invitation(
+                    org_id=org_id,
+                    email=email,
+                    role_name=role_name,
+                    inviter_id=inviter_id,
+                )
+                return (email, invitation, None)
+            except (UserAlreadyMemberError, ValueError) as e:
+                return (email, None, str(e))
+
+        results = await asyncio.gather(*[create_single(email) for email in emails])
+
+        # Step 3: Separate successes and failures
+        successful: list[OrgInvitation] = []
+        failed: list[tuple[str, str]] = []
+        for email, invitation, error in results:
+            if invitation:
+                successful.append(invitation)
+            elif error:
+                failed.append((email, error))
+
+        logger.info(
+            'Batch invitation creation completed',
+            extra={
+                'org_id': str(org_id),
+                'successful': len(successful),
+                'failed': len(failed),
+            },
+        )
+
+        return successful, failed
+
+    @staticmethod
+    async def accept_invitation(token: str, user_id: UUID) -> OrgInvitation:
+        """Accept an organization invitation.
+
+        This method:
+        1. Validates the token and invitation status
+        2. Checks expiration
+        3. Verifies user is not already a member
+        4. Creates LiteLLM integration
+        5. Adds user to the organization
+        6. Marks invitation as accepted
+
+        Args:
+            token: The invitation token
+            user_id: The user accepting the invitation
+
+        Returns:
+            OrgInvitation: The accepted invitation
+
+        Raises:
+            InvitationInvalidError: If token is invalid or invitation not pending
+            InvitationExpiredError: If invitation has expired
+            UserAlreadyMemberError: If user is already a member
+        """
+        logger.info(
+            'Accepting organization invitation',
+            extra={
+                'token_prefix': token[:10] + '...' if len(token) > 10 else token,
+                'user_id': str(user_id),
+            },
+        )
+
+        # Step 1: Get and validate invitation
+        invitation = await OrgInvitationStore.get_invitation_by_token(token)
+
+        if not invitation:
+            raise InvitationInvalidError('Invalid invitation token')
+
+        if invitation.status != OrgInvitation.STATUS_PENDING:
+            if invitation.status == OrgInvitation.STATUS_ACCEPTED:
+                raise InvitationInvalidError('Invitation has already been accepted')
+            elif invitation.status == OrgInvitation.STATUS_REVOKED:
+                raise InvitationInvalidError('Invitation has been revoked')
+            else:
+                raise InvitationInvalidError('Invitation is no longer valid')
+
+        # Step 2: Check expiration
+        if OrgInvitationStore.is_token_expired(invitation):
+            await OrgInvitationStore.update_invitation_status(
+                invitation.id, OrgInvitation.STATUS_EXPIRED
+            )
+            raise InvitationExpiredError('Invitation has expired')
+
+        # Step 2.5: Verify user email matches invitation email
+        user = await UserStore.get_user_by_id_async(str(user_id))
+        if not user:
+            raise InvitationInvalidError('User not found')
+
+        user_email = user.email
+        # Fallback: fetch email from Keycloak if not in database (for existing users)
+        if not user_email:
+            token_manager = TokenManager()
+            user_info = await token_manager.get_user_info_from_user_id(str(user_id))
+            user_email = user_info.get('email') if user_info else None
+
+        if not user_email:
+            raise EmailMismatchError('Your account does not have an email address')
+
+        user_email = user_email.lower().strip()
+        invitation_email = invitation.email.lower().strip()
+
+        if user_email != invitation_email:
+            logger.warning(
+                'Email mismatch during invitation acceptance',
+                extra={
+                    'user_id': str(user_id),
+                    'user_email': user_email,
+                    'invitation_email': invitation_email,
+                    'invitation_id': invitation.id,
+                },
+            )
+            raise EmailMismatchError()
+
+        # Step 3: Check if user is already a member
+        existing_member = OrgMemberStore.get_org_member(invitation.org_id, user_id)
+        if existing_member:
+            raise UserAlreadyMemberError(
+                'You are already a member of this organization'
+            )
+
+        # Step 4: Create LiteLLM integration for the user in the new org
+        try:
+            settings = await OrgService.create_litellm_integration(
+                invitation.org_id, str(user_id)
+            )
+        except Exception as e:
+            logger.error(
+                'Failed to create LiteLLM integration for invitation acceptance',
+                extra={
+                    'invitation_id': invitation.id,
+                    'user_id': str(user_id),
+                    'org_id': str(invitation.org_id),
+                    'error': str(e),
+                },
+            )
+            raise InvitationInvalidError(
+                'Failed to set up organization access. Please try again.'
+            )
+
+        # Step 5: Add user to organization
+        from storage.org_member_store import OrgMemberStore as OMS
+
+        org_member_kwargs = OMS.get_kwargs_from_settings(settings)
+        # Don't override with org defaults - use invitation-specified role
+        org_member_kwargs.pop('llm_model', None)
+        org_member_kwargs.pop('llm_base_url', None)
+
+        OrgMemberStore.add_user_to_org(
+            org_id=invitation.org_id,
+            user_id=user_id,
+            role_id=invitation.role_id,
+            llm_api_key=settings.llm_api_key,
+            status='active',
+        )
+
+        # Step 6: Mark invitation as accepted
+        updated_invitation = await OrgInvitationStore.update_invitation_status(
+            invitation.id,
+            OrgInvitation.STATUS_ACCEPTED,
+            accepted_by_user_id=user_id,
+        )
+
+        logger.info(
+            'Organization invitation accepted',
+            extra={
+                'invitation_id': invitation.id,
+                'user_id': str(user_id),
+                'org_id': str(invitation.org_id),
+                'role_id': invitation.role_id,
+            },
+        )
+
+        return updated_invitation
diff --git a/enterprise/storage/__init__.py b/enterprise/storage/__init__.py
index c00ad5346a..13b8564421 100644
--- a/enterprise/storage/__init__.py
+++ b/enterprise/storage/__init__.py
@@ -20,6 +20,7 @@ from storage.linear_workspace import LinearWorkspace
 from storage.maintenance_task import MaintenanceTask, MaintenanceTaskStatus
 from storage.openhands_pr import OpenhandsPR
 from storage.org import Org
+from storage.org_invitation import OrgInvitation
 from storage.org_member import OrgMember
 from storage.proactive_convos import ProactiveConversation
 from storage.role import Role
@@ -65,6 +66,7 @@ __all__ = [
     'MaintenanceTaskStatus',
     'OpenhandsPR',
     'Org',
+    'OrgInvitation',
     'OrgMember',
     'ProactiveConversation',
     'Role',
diff --git a/enterprise/storage/org.py b/enterprise/storage/org.py
index 6e9884d655..bd20cb45d3 100644
--- a/enterprise/storage/org.py
+++ b/enterprise/storage/org.py
@@ -52,6 +52,7 @@ class Org(Base):  # type: ignore
     # Relationships
     org_members = relationship('OrgMember', back_populates='org')
     current_users = relationship('User', back_populates='current_org')
+    invitations = relationship('OrgInvitation', back_populates='org')
     billing_sessions = relationship('BillingSession', back_populates='org')
     stored_conversation_metadata_saas = relationship(
         'StoredConversationMetadataSaas', back_populates='org'
diff --git a/enterprise/storage/org_invitation.py b/enterprise/storage/org_invitation.py
new file mode 100644
index 0000000000..167271f8d3
--- /dev/null
+++ b/enterprise/storage/org_invitation.py
@@ -0,0 +1,59 @@
+"""
+SQLAlchemy model for Organization Invitation.
+"""
+
+from sqlalchemy import UUID, Column, DateTime, ForeignKey, Integer, String, text
+from sqlalchemy.orm import relationship
+from storage.base import Base
+
+
+class OrgInvitation(Base):  # type: ignore
+    """Organization invitation model.
+
+    Represents an invitation for a user to join an organization.
+    Invitations are created by organization owners/admins and contain
+    a secure token that can be used to accept the invitation.
+    """
+
+    __tablename__ = 'org_invitation'
+
+    id = Column(Integer, primary_key=True, autoincrement=True)
+    token = Column(String(64), nullable=False, unique=True, index=True)
+    org_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey('org.id', ondelete='CASCADE'),
+        nullable=False,
+        index=True,
+    )
+    email = Column(String(255), nullable=False, index=True)
+    role_id = Column(Integer, ForeignKey('role.id'), nullable=False)
+    inviter_id = Column(UUID(as_uuid=True), ForeignKey('user.id'), nullable=False)
+    status = Column(
+        String(20),
+        nullable=False,
+        server_default=text("'pending'"),
+    )
+    created_at = Column(
+        DateTime,
+        nullable=False,
+        server_default=text('CURRENT_TIMESTAMP'),
+    )
+    expires_at = Column(DateTime, nullable=False)
+    accepted_at = Column(DateTime, nullable=True)
+    accepted_by_user_id = Column(
+        UUID(as_uuid=True),
+        ForeignKey('user.id'),
+        nullable=True,
+    )
+
+    # Relationships
+    org = relationship('Org', back_populates='invitations')
+    role = relationship('Role')
+    inviter = relationship('User', foreign_keys=[inviter_id])
+    accepted_by_user = relationship('User', foreign_keys=[accepted_by_user_id])
+
+    # Status constants
+    STATUS_PENDING = 'pending'
+    STATUS_ACCEPTED = 'accepted'
+    STATUS_REVOKED = 'revoked'
+    STATUS_EXPIRED = 'expired'
diff --git a/enterprise/storage/org_invitation_store.py b/enterprise/storage/org_invitation_store.py
new file mode 100644
index 0000000000..86a84fb411
--- /dev/null
+++ b/enterprise/storage/org_invitation_store.py
@@ -0,0 +1,227 @@
+"""
+Store class for managing organization invitations.
+"""
+
+import secrets
+import string
+from datetime import datetime, timedelta
+from typing import Optional
+from uuid import UUID
+
+from sqlalchemy import and_, select
+from sqlalchemy.orm import joinedload
+from storage.database import a_session_maker
+from storage.org_invitation import OrgInvitation
+
+from openhands.core.logger import openhands_logger as logger
+
+# Invitation token configuration
+INVITATION_TOKEN_PREFIX = 'inv-'
+INVITATION_TOKEN_LENGTH = 48  # Total length will be 52 with prefix
+DEFAULT_EXPIRATION_DAYS = 7
+
+
+class OrgInvitationStore:
+    """Store for managing organization invitations."""
+
+    @staticmethod
+    def generate_token(length: int = INVITATION_TOKEN_LENGTH) -> str:
+        """Generate a secure invitation token.
+
+        Uses cryptographically secure random generation for tokens.
+        Pattern from api_key_store.py.
+
+        Args:
+            length: Length of the random part of the token
+
+        Returns:
+            str: Token with prefix (e.g., 'inv-aBcDeF123...')
+        """
+        alphabet = string.ascii_letters + string.digits
+        random_part = ''.join(secrets.choice(alphabet) for _ in range(length))
+        return f'{INVITATION_TOKEN_PREFIX}{random_part}'
+
+    @staticmethod
+    async def create_invitation(
+        org_id: UUID,
+        email: str,
+        role_id: int,
+        inviter_id: UUID,
+        expiration_days: int = DEFAULT_EXPIRATION_DAYS,
+    ) -> OrgInvitation:
+        """Create a new organization invitation.
+
+        Args:
+            org_id: Organization UUID
+            email: Invitee's email address
+            role_id: Role ID to assign on acceptance
+            inviter_id: User ID of the person creating the invitation
+            expiration_days: Days until the invitation expires
+
+        Returns:
+            OrgInvitation: The created invitation record
+        """
+        async with a_session_maker() as session:
+            token = OrgInvitationStore.generate_token()
+            # Use timezone-naive datetime for database compatibility
+            expires_at = datetime.utcnow() + timedelta(days=expiration_days)
+
+            invitation = OrgInvitation(
+                token=token,
+                org_id=org_id,
+                email=email.lower().strip(),
+                role_id=role_id,
+                inviter_id=inviter_id,
+                status=OrgInvitation.STATUS_PENDING,
+                expires_at=expires_at,
+            )
+            session.add(invitation)
+            await session.commit()
+
+            # Re-fetch with eagerly loaded relationships to avoid DetachedInstanceError
+            result = await session.execute(
+                select(OrgInvitation)
+                .options(joinedload(OrgInvitation.role))
+                .filter(OrgInvitation.id == invitation.id)
+            )
+            invitation = result.scalars().first()
+
+            logger.info(
+                'Created organization invitation',
+                extra={
+                    'invitation_id': invitation.id,
+                    'org_id': str(org_id),
+                    'email': email,
+                    'inviter_id': str(inviter_id),
+                    'expires_at': expires_at.isoformat(),
+                },
+            )
+
+            return invitation
+
+    @staticmethod
+    async def get_invitation_by_token(token: str) -> Optional[OrgInvitation]:
+        """Get an invitation by its token.
+
+        Args:
+            token: The invitation token
+
+        Returns:
+            OrgInvitation or None if not found
+        """
+        async with a_session_maker() as session:
+            result = await session.execute(
+                select(OrgInvitation)
+                .options(joinedload(OrgInvitation.org), joinedload(OrgInvitation.role))
+                .filter(OrgInvitation.token == token)
+            )
+            return result.scalars().first()
+
+    @staticmethod
+    async def get_pending_invitation(
+        org_id: UUID, email: str
+    ) -> Optional[OrgInvitation]:
+        """Get a pending invitation for an email in an organization.
+
+        Args:
+            org_id: Organization UUID
+            email: Email address to check
+
+        Returns:
+            OrgInvitation or None if no pending invitation exists
+        """
+        async with a_session_maker() as session:
+            result = await session.execute(
+                select(OrgInvitation).filter(
+                    and_(
+                        OrgInvitation.org_id == org_id,
+                        OrgInvitation.email == email.lower().strip(),
+                        OrgInvitation.status == OrgInvitation.STATUS_PENDING,
+                    )
+                )
+            )
+            return result.scalars().first()
+
+    @staticmethod
+    async def update_invitation_status(
+        invitation_id: int,
+        status: str,
+        accepted_by_user_id: Optional[UUID] = None,
+    ) -> Optional[OrgInvitation]:
+        """Update an invitation's status.
+
+        Args:
+            invitation_id: The invitation ID
+            status: New status (pending, accepted, revoked, expired)
+            accepted_by_user_id: User ID who accepted (only for 'accepted' status)
+
+        Returns:
+            Updated OrgInvitation or None if not found
+        """
+        async with a_session_maker() as session:
+            result = await session.execute(
+                select(OrgInvitation).filter(OrgInvitation.id == invitation_id)
+            )
+            invitation = result.scalars().first()
+
+            if not invitation:
+                return None
+
+            old_status = invitation.status
+            invitation.status = status
+
+            if status == OrgInvitation.STATUS_ACCEPTED and accepted_by_user_id:
+                # Use timezone-naive datetime for database compatibility
+                invitation.accepted_at = datetime.utcnow()
+                invitation.accepted_by_user_id = accepted_by_user_id
+
+            await session.commit()
+            await session.refresh(invitation)
+
+            logger.info(
+                'Updated invitation status',
+                extra={
+                    'invitation_id': invitation_id,
+                    'old_status': old_status,
+                    'new_status': status,
+                    'accepted_by_user_id': (
+                        str(accepted_by_user_id) if accepted_by_user_id else None
+                    ),
+                },
+            )
+
+            return invitation
+
+    @staticmethod
+    def is_token_expired(invitation: OrgInvitation) -> bool:
+        """Check if an invitation token has expired.
+
+        Args:
+            invitation: The invitation to check
+
+        Returns:
+            bool: True if expired, False otherwise
+        """
+        # Use timezone-naive datetime for comparison (database stores without timezone)
+        now = datetime.utcnow()
+        return invitation.expires_at < now
+
+    @staticmethod
+    async def mark_expired_if_needed(invitation: OrgInvitation) -> bool:
+        """Check if invitation is expired and update status if needed.
+
+        Args:
+            invitation: The invitation to check
+
+        Returns:
+            bool: True if invitation was marked as expired, False otherwise
+        """
+        if (
+            invitation.status == OrgInvitation.STATUS_PENDING
+            and OrgInvitationStore.is_token_expired(invitation)
+        ):
+            await OrgInvitationStore.update_invitation_status(
+                invitation.id, OrgInvitation.STATUS_EXPIRED
+            )
+            return True
+        return False
diff --git a/enterprise/storage/user_store.py b/enterprise/storage/user_store.py
index ff49c17da8..379f02e45e 100644
--- a/enterprise/storage/user_store.py
+++ b/enterprise/storage/user_store.py
@@ -770,6 +770,30 @@ class UserStore:
             finally:
                 await UserStore._release_user_creation_lock(user_id)
 
+    @staticmethod
+    async def get_user_by_email_async(email: str) -> Optional[User]:
+        """Get user by email address (async version).
+
+        This method looks up a user by their email address. Note that email
+        addresses may not be unique across all users in rare cases.
+
+        Args:
+            email: The email address to search for
+
+        Returns:
+            User: The user with the matching email, or None if not found
+        """
+        if not email:
+            return None
+
+        async with a_session_maker() as session:
+            result = await session.execute(
+                select(User)
+                .options(joinedload(User.org_members))
+                .filter(User.email == email.lower().strip())
+            )
+            return result.scalars().first()
+
     @staticmethod
     def list_users() -> list[User]:
         """List all users."""
diff --git a/enterprise/tests/unit/test_auth_invitation_callback.py b/enterprise/tests/unit/test_auth_invitation_callback.py
new file mode 100644
index 0000000000..e6906e550f
--- /dev/null
+++ b/enterprise/tests/unit/test_auth_invitation_callback.py
@@ -0,0 +1,181 @@
+"""Tests for auth callback invitation acceptance - EmailMismatchError handling."""
+
+import pytest
+
+
+class TestAuthCallbackInvitationEmailMismatch:
+    """Test cases for EmailMismatchError handling during auth callback."""
+
+    @pytest.fixture
+    def mock_redirect_url(self):
+        """Base redirect URL."""
+        return 'https://app.example.com/'
+
+    @pytest.fixture
+    def mock_user_id(self):
+        """Mock user ID."""
+        return '87654321-4321-8765-4321-876543218765'
+
+    def test_email_mismatch_appends_to_url_without_query_params(
+        self, mock_redirect_url, mock_user_id
+    ):
+        """Test that email_mismatch=true is appended correctly when URL has no query params."""
+        from server.routes.org_invitation_models import EmailMismatchError
+
+        # Simulate the logic from auth.py
+        redirect_url = mock_redirect_url
+        try:
+            raise EmailMismatchError('Your email does not match the invitation')
+        except EmailMismatchError:
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&email_mismatch=true'
+            else:
+                redirect_url = f'{redirect_url}?email_mismatch=true'
+
+        assert redirect_url == 'https://app.example.com/?email_mismatch=true'
+
+    def test_email_mismatch_appends_to_url_with_query_params(self, mock_user_id):
+        """Test that email_mismatch=true is appended correctly when URL has existing query params."""
+        from server.routes.org_invitation_models import EmailMismatchError
+
+        redirect_url = 'https://app.example.com/?other_param=value'
+        try:
+            raise EmailMismatchError()
+        except EmailMismatchError:
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&email_mismatch=true'
+            else:
+                redirect_url = f'{redirect_url}?email_mismatch=true'
+
+        assert (
+            redirect_url
+            == 'https://app.example.com/?other_param=value&email_mismatch=true'
+        )
+
+    def test_email_mismatch_error_has_default_message(self):
+        """Test that EmailMismatchError has the default message."""
+        from server.routes.org_invitation_models import EmailMismatchError
+
+        error = EmailMismatchError()
+        assert str(error) == 'Your email does not match the invitation'
+
+    def test_email_mismatch_error_accepts_custom_message(self):
+        """Test that EmailMismatchError accepts a custom message."""
+        from server.routes.org_invitation_models import EmailMismatchError
+
+        custom_message = 'Custom error message'
+        error = EmailMismatchError(custom_message)
+        assert str(error) == custom_message
+
+    def test_email_mismatch_error_is_invitation_error(self):
+        """Test that EmailMismatchError inherits from InvitationError."""
+        from server.routes.org_invitation_models import (
+            EmailMismatchError,
+            InvitationError,
+        )
+
+        error = EmailMismatchError()
+        assert isinstance(error, InvitationError)
+
+
+class TestInvitationTokenInOAuthState:
+    """Test cases for invitation token handling in OAuth state."""
+
+    def test_invitation_token_included_in_oauth_state(self):
+        """Test that invitation token is included in OAuth state data."""
+        import base64
+        import json
+
+        # Simulate building OAuth state with invitation token
+        state_data = {
+            'redirect_url': 'https://app.example.com/',
+            'invitation_token': 'inv-test-token-12345',
+        }
+
+        encoded_state = base64.b64encode(json.dumps(state_data).encode()).decode()
+        decoded_data = json.loads(base64.b64decode(encoded_state))
+
+        assert decoded_data['invitation_token'] == 'inv-test-token-12345'
+        assert decoded_data['redirect_url'] == 'https://app.example.com/'
+
+    def test_invitation_token_extracted_from_oauth_state(self):
+        """Test that invitation token can be extracted from OAuth state."""
+        import base64
+        import json
+
+        state_data = {
+            'redirect_url': 'https://app.example.com/',
+            'invitation_token': 'inv-test-token-12345',
+        }
+
+        encoded_state = base64.b64encode(json.dumps(state_data).encode()).decode()
+
+        # Simulate decoding in callback
+        decoded_state = json.loads(base64.b64decode(encoded_state))
+        invitation_token = decoded_state.get('invitation_token')
+
+        assert invitation_token == 'inv-test-token-12345'
+
+    def test_oauth_state_without_invitation_token(self):
+        """Test that OAuth state works without invitation token."""
+        import base64
+        import json
+
+        state_data = {
+            'redirect_url': 'https://app.example.com/',
+        }
+
+        encoded_state = base64.b64encode(json.dumps(state_data).encode()).decode()
+        decoded_data = json.loads(base64.b64decode(encoded_state))
+
+        assert 'invitation_token' not in decoded_data
+        assert decoded_data['redirect_url'] == 'https://app.example.com/'
+
+
+class TestAuthCallbackInvitationErrors:
+    """Test cases for various invitation error scenarios in auth callback."""
+
+    def test_invitation_expired_appends_flag(self):
+        """Test that invitation_expired=true is appended for expired invitations."""
+        from server.routes.org_invitation_models import InvitationExpiredError
+
+        redirect_url = 'https://app.example.com/'
+        try:
+            raise InvitationExpiredError()
+        except InvitationExpiredError:
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&invitation_expired=true'
+            else:
+                redirect_url = f'{redirect_url}?invitation_expired=true'
+
+        assert redirect_url == 'https://app.example.com/?invitation_expired=true'
+
+    def test_invitation_invalid_appends_flag(self):
+        """Test that invitation_invalid=true is appended for invalid invitations."""
+        from server.routes.org_invitation_models import InvitationInvalidError
+
+        redirect_url = 'https://app.example.com/'
+        try:
+            raise InvitationInvalidError()
+        except InvitationInvalidError:
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&invitation_invalid=true'
+            else:
+                redirect_url = f'{redirect_url}?invitation_invalid=true'
+
+        assert redirect_url == 'https://app.example.com/?invitation_invalid=true'
+
+    def test_already_member_appends_flag(self):
+        """Test that already_member=true is appended when user is already a member."""
+        from server.routes.org_invitation_models import UserAlreadyMemberError
+
+        redirect_url = 'https://app.example.com/'
+        try:
+            raise UserAlreadyMemberError()
+        except UserAlreadyMemberError:
+            if '?' in redirect_url:
+                redirect_url = f'{redirect_url}&already_member=true'
+            else:
+                redirect_url = f'{redirect_url}?already_member=true'
+
+        assert redirect_url == 'https://app.example.com/?already_member=true'
diff --git a/enterprise/tests/unit/test_email_service.py b/enterprise/tests/unit/test_email_service.py
new file mode 100644
index 0000000000..0ea63e0496
--- /dev/null
+++ b/enterprise/tests/unit/test_email_service.py
@@ -0,0 +1,192 @@
+"""Tests for email service."""
+
+import os
+from unittest.mock import MagicMock, patch
+
+from server.services.email_service import (
+    DEFAULT_WEB_HOST,
+    EmailService,
+)
+
+
+class TestEmailServiceInvitationUrl:
+    """Test cases for invitation URL generation."""
+
+    def test_invitation_url_uses_correct_endpoint(self):
+        """Test that invitation URL points to the correct API endpoint."""
+        mock_response = MagicMock()
+        mock_response.get.return_value = 'test-email-id'
+
+        with (
+            patch.dict(os.environ, {'RESEND_API_KEY': 'test-key'}),
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch('server.services.email_service.resend') as mock_resend,
+        ):
+            mock_resend.Emails.send.return_value = mock_response
+
+            EmailService.send_invitation_email(
+                to_email='test@example.com',
+                org_name='Test Org',
+                inviter_name='Inviter',
+                role_name='member',
+                invitation_token='inv-test-token-12345',
+                invitation_id=1,
+            )
+
+            # Get the call arguments
+            call_args = mock_resend.Emails.send.call_args
+            email_params = call_args[0][0]
+
+            # Verify the URL in the email HTML contains the correct endpoint
+            assert (
+                '/api/organizations/members/invite/accept?token='
+                in email_params['html']
+            )
+            assert 'inv-test-token-12345' in email_params['html']
+
+    def test_invitation_url_uses_web_host_env_var(self):
+        """Test that invitation URL uses WEB_HOST environment variable."""
+        custom_host = 'https://custom.example.com'
+        mock_response = MagicMock()
+        mock_response.get.return_value = 'test-email-id'
+
+        with (
+            patch.dict(
+                os.environ,
+                {'RESEND_API_KEY': 'test-key', 'WEB_HOST': custom_host},
+            ),
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch('server.services.email_service.resend') as mock_resend,
+        ):
+            mock_resend.Emails.send.return_value = mock_response
+
+            EmailService.send_invitation_email(
+                to_email='test@example.com',
+                org_name='Test Org',
+                inviter_name='Inviter',
+                role_name='member',
+                invitation_token='inv-test-token-12345',
+                invitation_id=1,
+            )
+
+            call_args = mock_resend.Emails.send.call_args
+            email_params = call_args[0][0]
+
+            expected_url = f'{custom_host}/api/organizations/members/invite/accept?token=inv-test-token-12345'
+            assert expected_url in email_params['html']
+
+    def test_invitation_url_uses_default_host_when_env_not_set(self):
+        """Test that invitation URL falls back to DEFAULT_WEB_HOST when env not set."""
+        mock_response = MagicMock()
+        mock_response.get.return_value = 'test-email-id'
+
+        env_without_web_host = {'RESEND_API_KEY': 'test-key'}
+        # Remove WEB_HOST if it exists
+        env_without_web_host.pop('WEB_HOST', None)
+
+        with (
+            patch.dict(os.environ, env_without_web_host, clear=True),
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch('server.services.email_service.resend') as mock_resend,
+        ):
+            # Clear WEB_HOST from the environment
+            os.environ.pop('WEB_HOST', None)
+            mock_resend.Emails.send.return_value = mock_response
+
+            EmailService.send_invitation_email(
+                to_email='test@example.com',
+                org_name='Test Org',
+                inviter_name='Inviter',
+                role_name='member',
+                invitation_token='inv-test-token-12345',
+                invitation_id=1,
+            )
+
+            call_args = mock_resend.Emails.send.call_args
+            email_params = call_args[0][0]
+
+            expected_url = f'{DEFAULT_WEB_HOST}/api/organizations/members/invite/accept?token=inv-test-token-12345'
+            assert expected_url in email_params['html']
+
+
+class TestEmailServiceGetResendClient:
+    """Test cases for Resend client initialization."""
+
+    def test_get_resend_client_returns_false_when_resend_not_available(self):
+        """Test that _get_resend_client returns False when resend is not installed."""
+        with patch('server.services.email_service.RESEND_AVAILABLE', False):
+            result = EmailService._get_resend_client()
+            assert result is False
+
+    def test_get_resend_client_returns_false_when_api_key_not_configured(self):
+        """Test that _get_resend_client returns False when API key is missing."""
+        with (
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch.dict(os.environ, {}, clear=True),
+        ):
+            os.environ.pop('RESEND_API_KEY', None)
+            result = EmailService._get_resend_client()
+            assert result is False
+
+    def test_get_resend_client_returns_true_when_configured(self):
+        """Test that _get_resend_client returns True when properly configured."""
+        with (
+            patch.dict(os.environ, {'RESEND_API_KEY': 'test-key'}),
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch('server.services.email_service.resend') as mock_resend,
+        ):
+            result = EmailService._get_resend_client()
+            assert result is True
+            assert mock_resend.api_key == 'test-key'
+
+
+class TestEmailServiceSendInvitationEmail:
+    """Test cases for send_invitation_email method."""
+
+    def test_send_invitation_email_skips_when_client_not_ready(self):
+        """Test that email sending is skipped when client is not ready."""
+        with patch.object(
+            EmailService, '_get_resend_client', return_value=False
+        ) as mock_get_client:
+            # Should not raise, just return early
+            EmailService.send_invitation_email(
+                to_email='test@example.com',
+                org_name='Test Org',
+                inviter_name='Inviter',
+                role_name='member',
+                invitation_token='inv-test-token',
+                invitation_id=1,
+            )
+
+            mock_get_client.assert_called_once()
+
+    def test_send_invitation_email_includes_all_required_info(self):
+        """Test that invitation email includes org name, inviter name, and role."""
+        mock_response = MagicMock()
+        mock_response.get.return_value = 'test-email-id'
+
+        with (
+            patch.dict(os.environ, {'RESEND_API_KEY': 'test-key'}),
+            patch('server.services.email_service.RESEND_AVAILABLE', True),
+            patch('server.services.email_service.resend') as mock_resend,
+        ):
+            mock_resend.Emails.send.return_value = mock_response
+
+            EmailService.send_invitation_email(
+                to_email='test@example.com',
+                org_name='Acme Corp',
+                inviter_name='John Doe',
+                role_name='admin',
+                invitation_token='inv-test-token-12345',
+                invitation_id=42,
+            )
+
+            call_args = mock_resend.Emails.send.call_args
+            email_params = call_args[0][0]
+
+            # Verify email content
+            assert email_params['to'] == ['test@example.com']
+            assert 'Acme Corp' in email_params['subject']
+            assert 'John Doe' in email_params['html']
+            assert 'Acme Corp' in email_params['html']
+            assert 'admin' in email_params['html']
diff --git a/enterprise/tests/unit/test_org_invitation_service.py b/enterprise/tests/unit/test_org_invitation_service.py
new file mode 100644
index 0000000000..06c0d258ed
--- /dev/null
+++ b/enterprise/tests/unit/test_org_invitation_service.py
@@ -0,0 +1,464 @@
+"""Tests for organization invitation service - email validation."""
+
+from unittest.mock import AsyncMock, MagicMock, patch
+from uuid import UUID
+
+import pytest
+from server.routes.org_invitation_models import (
+    EmailMismatchError,
+)
+from server.services.org_invitation_service import OrgInvitationService
+from storage.org_invitation import OrgInvitation
+
+
+class TestAcceptInvitationEmailValidation:
+    """Test cases for email validation during invitation acceptance."""
+
+    @pytest.fixture
+    def mock_invitation(self):
+        """Create a mock invitation with pending status."""
+        invitation = MagicMock(spec=OrgInvitation)
+        invitation.id = 1
+        invitation.email = 'alice@example.com'
+        invitation.status = OrgInvitation.STATUS_PENDING
+        invitation.org_id = UUID('12345678-1234-5678-1234-567812345678')
+        invitation.role_id = 1
+        return invitation
+
+    @pytest.fixture
+    def mock_user(self):
+        """Create a mock user with email."""
+        user = MagicMock()
+        user.id = UUID('87654321-4321-8765-4321-876543218765')
+        user.email = 'alice@example.com'
+        return user
+
+    @pytest.mark.asyncio
+    async def test_accept_invitation_email_matches(self, mock_invitation, mock_user):
+        """Test that invitation is accepted when user email matches invitation email."""
+        # Arrange
+        user_id = mock_user.id
+        token = 'inv-test-token-12345'
+
+        with patch.object(
+            OrgInvitationService, 'accept_invitation', new_callable=AsyncMock
+        ) as mock_accept:
+            mock_accept.return_value = mock_invitation
+
+            # Act
+            await OrgInvitationService.accept_invitation(token, user_id)
+
+            # Assert
+            mock_accept.assert_called_once_with(token, user_id)
+
+    @pytest.mark.asyncio
+    async def test_accept_invitation_email_mismatch_raises_error(
+        self, mock_invitation, mock_user
+    ):
+        """Test that EmailMismatchError is raised when emails don't match."""
+        # Arrange
+        user_id = mock_user.id
+        token = 'inv-test-token-12345'
+        mock_user.email = 'bob@example.com'  # Different email
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.get_invitation_by_token',
+                new_callable=AsyncMock,
+            ) as mock_get_invitation,
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.is_token_expired'
+            ) as mock_is_expired,
+            patch(
+                'server.services.org_invitation_service.UserStore.get_user_by_id_async',
+                new_callable=AsyncMock,
+            ) as mock_get_user,
+        ):
+            mock_get_invitation.return_value = mock_invitation
+            mock_is_expired.return_value = False
+            mock_get_user.return_value = mock_user
+
+            # Act & Assert
+            with pytest.raises(EmailMismatchError):
+                await OrgInvitationService.accept_invitation(token, user_id)
+
+    @pytest.mark.asyncio
+    async def test_accept_invitation_user_no_email_keycloak_fallback_matches(
+        self, mock_invitation
+    ):
+        """Test that Keycloak email is used when user has no email in database."""
+        # Arrange
+        user_id = UUID('87654321-4321-8765-4321-876543218765')
+        token = 'inv-test-token-12345'
+
+        mock_user = MagicMock()
+        mock_user.id = user_id
+        mock_user.email = None  # No email in database
+
+        mock_keycloak_user_info = {'email': 'alice@example.com'}  # Email from Keycloak
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.get_invitation_by_token',
+                new_callable=AsyncMock,
+            ) as mock_get_invitation,
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.is_token_expired'
+            ) as mock_is_expired,
+            patch(
+                'server.services.org_invitation_service.UserStore.get_user_by_id_async',
+                new_callable=AsyncMock,
+            ) as mock_get_user,
+            patch(
+                'server.services.org_invitation_service.TokenManager'
+            ) as mock_token_manager_class,
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.get_org_member'
+            ) as mock_get_member,
+            patch(
+                'server.services.org_invitation_service.OrgService.create_litellm_integration',
+                new_callable=AsyncMock,
+            ) as mock_create_litellm,
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.add_user_to_org'
+            ),
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.update_invitation_status',
+                new_callable=AsyncMock,
+            ) as mock_update_status,
+        ):
+            mock_get_invitation.return_value = mock_invitation
+            mock_is_expired.return_value = False
+            mock_get_user.return_value = mock_user
+
+            # Mock TokenManager instance
+            mock_token_manager = MagicMock()
+            mock_token_manager.get_user_info_from_user_id = AsyncMock(
+                return_value=mock_keycloak_user_info
+            )
+            mock_token_manager_class.return_value = mock_token_manager
+
+            mock_get_member.return_value = None  # Not already a member
+            mock_create_litellm.return_value = MagicMock(llm_api_key='test-key')
+            mock_update_status.return_value = mock_invitation
+
+            # Act - should not raise error because Keycloak email matches
+            await OrgInvitationService.accept_invitation(token, user_id)
+
+            # Assert
+            mock_token_manager.get_user_info_from_user_id.assert_called_once_with(
+                str(user_id)
+            )
+
+    @pytest.mark.asyncio
+    async def test_accept_invitation_no_email_anywhere_raises_error(
+        self, mock_invitation
+    ):
+        """Test that EmailMismatchError is raised when user has no email in database or Keycloak."""
+        # Arrange
+        user_id = UUID('87654321-4321-8765-4321-876543218765')
+        token = 'inv-test-token-12345'
+
+        mock_user = MagicMock()
+        mock_user.id = user_id
+        mock_user.email = None  # No email in database
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.get_invitation_by_token',
+                new_callable=AsyncMock,
+            ) as mock_get_invitation,
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.is_token_expired'
+            ) as mock_is_expired,
+            patch(
+                'server.services.org_invitation_service.UserStore.get_user_by_id_async',
+                new_callable=AsyncMock,
+            ) as mock_get_user,
+            patch(
+                'server.services.org_invitation_service.TokenManager'
+            ) as mock_token_manager_class,
+        ):
+            mock_get_invitation.return_value = mock_invitation
+            mock_is_expired.return_value = False
+            mock_get_user.return_value = mock_user
+
+            # Mock TokenManager to return no email
+            mock_token_manager = MagicMock()
+            mock_token_manager.get_user_info_from_user_id = AsyncMock(return_value={})
+            mock_token_manager_class.return_value = mock_token_manager
+
+            # Act & Assert
+            with pytest.raises(EmailMismatchError) as exc_info:
+                await OrgInvitationService.accept_invitation(token, user_id)
+
+            assert 'does not have an email address' in str(exc_info.value)
+
+    @pytest.mark.asyncio
+    async def test_accept_invitation_email_comparison_is_case_insensitive(
+        self, mock_invitation
+    ):
+        """Test that email comparison is case insensitive."""
+        # Arrange
+        user_id = UUID('87654321-4321-8765-4321-876543218765')
+        token = 'inv-test-token-12345'
+
+        mock_user = MagicMock()
+        mock_user.id = user_id
+        mock_user.email = 'ALICE@EXAMPLE.COM'  # Uppercase email
+
+        mock_invitation.email = 'alice@example.com'  # Lowercase in invitation
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.get_invitation_by_token',
+                new_callable=AsyncMock,
+            ) as mock_get_invitation,
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.is_token_expired'
+            ) as mock_is_expired,
+            patch(
+                'server.services.org_invitation_service.UserStore.get_user_by_id_async',
+                new_callable=AsyncMock,
+            ) as mock_get_user,
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.get_org_member'
+            ) as mock_get_member,
+            patch(
+                'server.services.org_invitation_service.OrgService.create_litellm_integration',
+                new_callable=AsyncMock,
+            ) as mock_create_litellm,
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.add_user_to_org'
+            ),
+            patch(
+                'server.services.org_invitation_service.OrgInvitationStore.update_invitation_status',
+                new_callable=AsyncMock,
+            ) as mock_update_status,
+        ):
+            mock_get_invitation.return_value = mock_invitation
+            mock_is_expired.return_value = False
+            mock_get_user.return_value = mock_user
+            mock_get_member.return_value = None
+            mock_create_litellm.return_value = MagicMock(llm_api_key='test-key')
+            mock_update_status.return_value = mock_invitation
+
+            # Act - should not raise error because emails match case-insensitively
+            await OrgInvitationService.accept_invitation(token, user_id)
+
+            # Assert - invitation was accepted (update_invitation_status was called)
+            mock_update_status.assert_called_once()
+
+
+class TestCreateInvitationsBatch:
+    """Test cases for batch invitation creation."""
+
+    @pytest.fixture
+    def org_id(self):
+        """Organization UUID for testing."""
+        return UUID('12345678-1234-5678-1234-567812345678')
+
+    @pytest.fixture
+    def inviter_id(self):
+        """Inviter UUID for testing."""
+        return UUID('87654321-4321-8765-4321-876543218765')
+
+    @pytest.fixture
+    def mock_org(self):
+        """Create a mock organization."""
+        org = MagicMock()
+        org.id = UUID('12345678-1234-5678-1234-567812345678')
+        org.name = 'Test Org'
+        return org
+
+    @pytest.fixture
+    def mock_inviter_member(self):
+        """Create a mock inviter member with owner role."""
+        member = MagicMock()
+        member.user_id = UUID('87654321-4321-8765-4321-876543218765')
+        member.role_id = 1
+        return member
+
+    @pytest.fixture
+    def mock_owner_role(self):
+        """Create a mock owner role."""
+        role = MagicMock()
+        role.id = 1
+        role.name = 'owner'
+        return role
+
+    @pytest.fixture
+    def mock_member_role(self):
+        """Create a mock member role."""
+        role = MagicMock()
+        role.id = 3
+        role.name = 'member'
+        return role
+
+    @pytest.mark.asyncio
+    async def test_batch_creates_all_invitations_successfully(
+        self,
+        org_id,
+        inviter_id,
+        mock_org,
+        mock_inviter_member,
+        mock_owner_role,
+        mock_member_role,
+    ):
+        """Test that batch creation succeeds for all valid emails."""
+        # Arrange
+        emails = ['alice@example.com', 'bob@example.com']
+        mock_invitation_1 = MagicMock(spec=OrgInvitation)
+        mock_invitation_1.id = 1
+        mock_invitation_2 = MagicMock(spec=OrgInvitation)
+        mock_invitation_2.id = 2
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgStore.get_org_by_id',
+                return_value=mock_org,
+            ),
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.get_org_member',
+                return_value=mock_inviter_member,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_id',
+                return_value=mock_owner_role,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_name',
+                return_value=mock_member_role,
+            ),
+            patch.object(
+                OrgInvitationService,
+                'create_invitation',
+                new_callable=AsyncMock,
+                side_effect=[mock_invitation_1, mock_invitation_2],
+            ),
+        ):
+            # Act
+            successful, failed = await OrgInvitationService.create_invitations_batch(
+                org_id=org_id,
+                emails=emails,
+                role_name='member',
+                inviter_id=inviter_id,
+            )
+
+            # Assert
+            assert len(successful) == 2
+            assert len(failed) == 0
+
+    @pytest.mark.asyncio
+    async def test_batch_handles_partial_success(
+        self,
+        org_id,
+        inviter_id,
+        mock_org,
+        mock_inviter_member,
+        mock_owner_role,
+        mock_member_role,
+    ):
+        """Test that batch returns partial results when some emails fail."""
+        # Arrange
+        from server.routes.org_invitation_models import UserAlreadyMemberError
+
+        emails = ['alice@example.com', 'existing@example.com']
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.id = 1
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgStore.get_org_by_id',
+                return_value=mock_org,
+            ),
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.get_org_member',
+                return_value=mock_inviter_member,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_id',
+                return_value=mock_owner_role,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_name',
+                return_value=mock_member_role,
+            ),
+            patch.object(
+                OrgInvitationService,
+                'create_invitation',
+                new_callable=AsyncMock,
+                side_effect=[mock_invitation, UserAlreadyMemberError()],
+            ),
+        ):
+            # Act
+            successful, failed = await OrgInvitationService.create_invitations_batch(
+                org_id=org_id,
+                emails=emails,
+                role_name='member',
+                inviter_id=inviter_id,
+            )
+
+            # Assert
+            assert len(successful) == 1
+            assert len(failed) == 1
+            assert failed[0][0] == 'existing@example.com'
+
+    @pytest.mark.asyncio
+    async def test_batch_fails_entirely_on_permission_error(self, org_id, inviter_id):
+        """Test that permission error fails the entire batch upfront."""
+        # Arrange
+
+        emails = ['alice@example.com', 'bob@example.com']
+
+        with patch(
+            'server.services.org_invitation_service.OrgStore.get_org_by_id',
+            return_value=None,  # Organization not found
+        ):
+            # Act & Assert
+            with pytest.raises(ValueError) as exc_info:
+                await OrgInvitationService.create_invitations_batch(
+                    org_id=org_id,
+                    emails=emails,
+                    role_name='member',
+                    inviter_id=inviter_id,
+                )
+
+            assert 'not found' in str(exc_info.value)
+
+    @pytest.mark.asyncio
+    async def test_batch_fails_on_invalid_role(
+        self, org_id, inviter_id, mock_org, mock_inviter_member, mock_owner_role
+    ):
+        """Test that invalid role fails the entire batch."""
+        # Arrange
+        emails = ['alice@example.com']
+
+        with (
+            patch(
+                'server.services.org_invitation_service.OrgStore.get_org_by_id',
+                return_value=mock_org,
+            ),
+            patch(
+                'server.services.org_invitation_service.OrgMemberStore.get_org_member',
+                return_value=mock_inviter_member,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_id',
+                return_value=mock_owner_role,
+            ),
+            patch(
+                'server.services.org_invitation_service.RoleStore.get_role_by_name',
+                return_value=None,  # Invalid role
+            ),
+        ):
+            # Act & Assert
+            with pytest.raises(ValueError) as exc_info:
+                await OrgInvitationService.create_invitations_batch(
+                    org_id=org_id,
+                    emails=emails,
+                    role_name='invalid_role',
+                    inviter_id=inviter_id,
+                )
+
+            assert 'Invalid role' in str(exc_info.value)
diff --git a/enterprise/tests/unit/test_org_invitation_store.py b/enterprise/tests/unit/test_org_invitation_store.py
new file mode 100644
index 0000000000..304922d569
--- /dev/null
+++ b/enterprise/tests/unit/test_org_invitation_store.py
@@ -0,0 +1,308 @@
+"""Tests for organization invitation store."""
+
+from datetime import datetime, timedelta
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from storage.org_invitation import OrgInvitation
+from storage.org_invitation_store import (
+    INVITATION_TOKEN_LENGTH,
+    INVITATION_TOKEN_PREFIX,
+    OrgInvitationStore,
+)
+
+
+class TestGenerateToken:
+    """Test cases for token generation."""
+
+    def test_generate_token_has_correct_prefix(self):
+        """Test that generated tokens have the correct prefix."""
+        token = OrgInvitationStore.generate_token()
+        assert token.startswith(INVITATION_TOKEN_PREFIX)
+
+    def test_generate_token_has_correct_length(self):
+        """Test that generated tokens have the correct total length."""
+        token = OrgInvitationStore.generate_token()
+        expected_length = len(INVITATION_TOKEN_PREFIX) + INVITATION_TOKEN_LENGTH
+        assert len(token) == expected_length
+
+    def test_generate_token_uses_alphanumeric_characters(self):
+        """Test that generated tokens use only alphanumeric characters."""
+        token = OrgInvitationStore.generate_token()
+        # Remove prefix and check the rest is alphanumeric
+        random_part = token[len(INVITATION_TOKEN_PREFIX) :]
+        assert random_part.isalnum()
+
+    def test_generate_token_is_unique(self):
+        """Test that generated tokens are unique (probabilistically)."""
+        tokens = [OrgInvitationStore.generate_token() for _ in range(100)]
+        assert len(set(tokens)) == 100
+
+
+class TestIsTokenExpired:
+    """Test cases for token expiration checking."""
+
+    def test_token_not_expired_when_future(self):
+        """Test that tokens with future expiration are not expired."""
+        invitation = MagicMock(spec=OrgInvitation)
+        invitation.expires_at = datetime.utcnow() + timedelta(days=1)
+
+        result = OrgInvitationStore.is_token_expired(invitation)
+        assert result is False
+
+    def test_token_expired_when_past(self):
+        """Test that tokens with past expiration are expired."""
+        invitation = MagicMock(spec=OrgInvitation)
+        invitation.expires_at = datetime.utcnow() - timedelta(seconds=1)
+
+        result = OrgInvitationStore.is_token_expired(invitation)
+        assert result is True
+
+    def test_token_expired_at_exact_boundary(self):
+        """Test that tokens at exact expiration time are expired."""
+        # A token that expires "now" should be expired
+        now = datetime.utcnow()
+        invitation = MagicMock(spec=OrgInvitation)
+        invitation.expires_at = now - timedelta(microseconds=1)
+
+        result = OrgInvitationStore.is_token_expired(invitation)
+        assert result is True
+
+
+class TestCreateInvitation:
+    """Test cases for invitation creation."""
+
+    @pytest.mark.asyncio
+    async def test_create_invitation_normalizes_email(self):
+        """Test that email is normalized (lowercase, stripped) on creation."""
+        mock_session = AsyncMock()
+        mock_session.add = MagicMock()
+        mock_session.commit = AsyncMock()
+        mock_session.execute = AsyncMock()
+
+        # Mock the result of the re-fetch query
+        mock_result = MagicMock()
+        mock_invitation = MagicMock()
+        mock_invitation.id = 1
+        mock_invitation.email = 'test@example.com'
+        mock_result.scalars.return_value.first.return_value = mock_invitation
+        mock_session.execute.return_value = mock_result
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            from uuid import UUID
+
+            await OrgInvitationStore.create_invitation(
+                org_id=UUID('12345678-1234-5678-1234-567812345678'),
+                email='  TEST@EXAMPLE.COM  ',
+                role_id=1,
+                inviter_id=UUID('87654321-4321-8765-4321-876543218765'),
+            )
+
+            # Verify that the OrgInvitation was created with normalized email
+            add_call = mock_session.add.call_args
+            created_invitation = add_call[0][0]
+            assert created_invitation.email == 'test@example.com'
+
+
+class TestGetInvitationByToken:
+    """Test cases for getting invitation by token."""
+
+    @pytest.mark.asyncio
+    async def test_get_invitation_by_token_returns_invitation(self):
+        """Test that get_invitation_by_token returns the invitation when found."""
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.token = 'inv-test-token-12345'
+
+        mock_session = AsyncMock()
+        mock_result = MagicMock()
+        mock_result.scalars.return_value.first.return_value = mock_invitation
+        mock_session.execute = AsyncMock(return_value=mock_result)
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            result = await OrgInvitationStore.get_invitation_by_token(
+                'inv-test-token-12345'
+            )
+            assert result == mock_invitation
+
+    @pytest.mark.asyncio
+    async def test_get_invitation_by_token_returns_none_when_not_found(self):
+        """Test that get_invitation_by_token returns None when not found."""
+        mock_session = AsyncMock()
+        mock_result = MagicMock()
+        mock_result.scalars.return_value.first.return_value = None
+        mock_session.execute = AsyncMock(return_value=mock_result)
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            result = await OrgInvitationStore.get_invitation_by_token(
+                'inv-nonexistent-token'
+            )
+            assert result is None
+
+
+class TestGetPendingInvitation:
+    """Test cases for getting pending invitation."""
+
+    @pytest.mark.asyncio
+    async def test_get_pending_invitation_normalizes_email(self):
+        """Test that email is normalized when querying for pending invitations."""
+        mock_session = AsyncMock()
+        mock_result = MagicMock()
+        mock_result.scalars.return_value.first.return_value = None
+        mock_session.execute = AsyncMock(return_value=mock_result)
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            from uuid import UUID
+
+            await OrgInvitationStore.get_pending_invitation(
+                org_id=UUID('12345678-1234-5678-1234-567812345678'),
+                email='  TEST@EXAMPLE.COM  ',
+            )
+
+            # Verify the query was called (email normalization happens in the filter)
+            assert mock_session.execute.called
+
+
+class TestUpdateInvitationStatus:
+    """Test cases for updating invitation status."""
+
+    @pytest.mark.asyncio
+    async def test_update_status_sets_accepted_at_for_accepted(self):
+        """Test that accepted_at is set when status is accepted."""
+        from uuid import UUID
+
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.id = 1
+        mock_invitation.status = OrgInvitation.STATUS_PENDING
+
+        mock_session = AsyncMock()
+        mock_result = MagicMock()
+        mock_result.scalars.return_value.first.return_value = mock_invitation
+        mock_session.execute = AsyncMock(return_value=mock_result)
+        mock_session.commit = AsyncMock()
+        mock_session.refresh = AsyncMock()
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            user_id = UUID('87654321-4321-8765-4321-876543218765')
+            await OrgInvitationStore.update_invitation_status(
+                invitation_id=1,
+                status=OrgInvitation.STATUS_ACCEPTED,
+                accepted_by_user_id=user_id,
+            )
+
+            assert mock_invitation.accepted_at is not None
+            assert mock_invitation.accepted_by_user_id == user_id
+
+    @pytest.mark.asyncio
+    async def test_update_status_returns_none_when_not_found(self):
+        """Test that update returns None when invitation not found."""
+        mock_session = AsyncMock()
+        mock_result = MagicMock()
+        mock_result.scalars.return_value.first.return_value = None
+        mock_session.execute = AsyncMock(return_value=mock_result)
+
+        with patch(
+            'storage.org_invitation_store.a_session_maker'
+        ) as mock_session_maker:
+            mock_session_manager = AsyncMock()
+            mock_session_manager.__aenter__.return_value = mock_session
+            mock_session_manager.__aexit__.return_value = None
+            mock_session_maker.return_value = mock_session_manager
+
+            result = await OrgInvitationStore.update_invitation_status(
+                invitation_id=999,
+                status=OrgInvitation.STATUS_ACCEPTED,
+            )
+            assert result is None
+
+
+class TestMarkExpiredIfNeeded:
+    """Test cases for marking expired invitations."""
+
+    @pytest.mark.asyncio
+    async def test_marks_expired_when_pending_and_past_expiry(self):
+        """Test that pending expired invitations are marked as expired."""
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.id = 1
+        mock_invitation.status = OrgInvitation.STATUS_PENDING
+        mock_invitation.expires_at = datetime.utcnow() - timedelta(days=1)
+
+        with patch.object(
+            OrgInvitationStore,
+            'update_invitation_status',
+            new_callable=AsyncMock,
+        ) as mock_update:
+            result = await OrgInvitationStore.mark_expired_if_needed(mock_invitation)
+
+            assert result is True
+            mock_update.assert_called_once_with(1, OrgInvitation.STATUS_EXPIRED)
+
+    @pytest.mark.asyncio
+    async def test_does_not_mark_when_not_expired(self):
+        """Test that non-expired invitations are not marked."""
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.id = 1
+        mock_invitation.status = OrgInvitation.STATUS_PENDING
+        mock_invitation.expires_at = datetime.utcnow() + timedelta(days=1)
+
+        with patch.object(
+            OrgInvitationStore,
+            'update_invitation_status',
+            new_callable=AsyncMock,
+        ) as mock_update:
+            result = await OrgInvitationStore.mark_expired_if_needed(mock_invitation)
+
+            assert result is False
+            mock_update.assert_not_called()
+
+    @pytest.mark.asyncio
+    async def test_does_not_mark_when_not_pending(self):
+        """Test that non-pending invitations are not marked even if expired."""
+        mock_invitation = MagicMock(spec=OrgInvitation)
+        mock_invitation.id = 1
+        mock_invitation.status = OrgInvitation.STATUS_ACCEPTED
+        mock_invitation.expires_at = datetime.utcnow() - timedelta(days=1)
+
+        with patch.object(
+            OrgInvitationStore,
+            'update_invitation_status',
+            new_callable=AsyncMock,
+        ) as mock_update:
+            result = await OrgInvitationStore.mark_expired_if_needed(mock_invitation)
+
+            assert result is False
+            mock_update.assert_not_called()
diff --git a/enterprise/tests/unit/test_org_invitations_router.py b/enterprise/tests/unit/test_org_invitations_router.py
new file mode 100644
index 0000000000..cbfbf4c810
--- /dev/null
+++ b/enterprise/tests/unit/test_org_invitations_router.py
@@ -0,0 +1,388 @@
+"""Tests for organization invitations API router."""
+
+from unittest.mock import AsyncMock, MagicMock, patch
+
+import pytest
+from fastapi import FastAPI
+from fastapi.testclient import TestClient
+from server.routes.org_invitation_models import (
+    EmailMismatchError,
+    InvitationExpiredError,
+    InvitationInvalidError,
+    UserAlreadyMemberError,
+)
+from server.routes.org_invitations import accept_router, invitation_router
+
+
+@pytest.fixture
+def app():
+    """Create a FastAPI app with the invitation routers."""
+    app = FastAPI()
+    app.include_router(invitation_router)
+    app.include_router(accept_router)
+    return app
+
+
+@pytest.fixture
+def client(app):
+    """Create a test client for the app."""
+    return TestClient(app)
+
+
+class TestRouterPrefixes:
+    """Test that router prefixes are configured correctly."""
+
+    def test_invitation_router_has_correct_prefix(self):
+        """Test that invitation_router has /api/organizations/{org_id}/members prefix."""
+        assert invitation_router.prefix == '/api/organizations/{org_id}/members'
+
+    def test_accept_router_has_correct_prefix(self):
+        """Test that accept_router has /api/organizations/members/invite prefix."""
+        assert accept_router.prefix == '/api/organizations/members/invite'
+
+
+class TestAcceptInvitationEndpoint:
+    """Test cases for the accept invitation endpoint."""
+
+    @pytest.fixture
+    def mock_user_auth(self):
+        """Create a mock user auth."""
+        user_auth = MagicMock()
+        user_auth.get_user_id = AsyncMock(
+            return_value='87654321-4321-8765-4321-876543218765'
+        )
+        return user_auth
+
+    @pytest.mark.asyncio
+    async def test_accept_unauthenticated_redirects_to_login(self, client):
+        """Test that unauthenticated users are redirected to login with invitation token."""
+        with patch(
+            'server.routes.org_invitations.get_user_auth',
+            new_callable=AsyncMock,
+            return_value=None,
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert '/login?invitation_token=inv-test-token-123' in response.headers.get(
+                'location', ''
+            )
+
+    @pytest.mark.asyncio
+    async def test_accept_authenticated_success_redirects_home(
+        self, client, mock_user_auth
+    ):
+        """Test that successful acceptance redirects to home page."""
+        mock_invitation = MagicMock()
+
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                return_value=mock_invitation,
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            location = response.headers.get('location', '')
+            assert location.endswith('/')
+            assert 'invitation_expired' not in location
+            assert 'invitation_invalid' not in location
+            assert 'email_mismatch' not in location
+
+    @pytest.mark.asyncio
+    async def test_accept_expired_invitation_redirects_with_flag(
+        self, client, mock_user_auth
+    ):
+        """Test that expired invitation redirects with invitation_expired=true."""
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                side_effect=InvitationExpiredError(),
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert 'invitation_expired=true' in response.headers.get('location', '')
+
+    @pytest.mark.asyncio
+    async def test_accept_invalid_invitation_redirects_with_flag(
+        self, client, mock_user_auth
+    ):
+        """Test that invalid invitation redirects with invitation_invalid=true."""
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                side_effect=InvitationInvalidError(),
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert 'invitation_invalid=true' in response.headers.get('location', '')
+
+    @pytest.mark.asyncio
+    async def test_accept_already_member_redirects_with_flag(
+        self, client, mock_user_auth
+    ):
+        """Test that already member error redirects with already_member=true."""
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                side_effect=UserAlreadyMemberError(),
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert 'already_member=true' in response.headers.get('location', '')
+
+    @pytest.mark.asyncio
+    async def test_accept_email_mismatch_redirects_with_flag(
+        self, client, mock_user_auth
+    ):
+        """Test that email mismatch error redirects with email_mismatch=true."""
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                side_effect=EmailMismatchError(),
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert 'email_mismatch=true' in response.headers.get('location', '')
+
+    @pytest.mark.asyncio
+    async def test_accept_unexpected_error_redirects_with_flag(
+        self, client, mock_user_auth
+    ):
+        """Test that unexpected errors redirect with invitation_error=true."""
+        with (
+            patch(
+                'server.routes.org_invitations.get_user_auth',
+                new_callable=AsyncMock,
+                return_value=mock_user_auth,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.accept_invitation',
+                new_callable=AsyncMock,
+                side_effect=Exception('Unexpected error'),
+            ),
+        ):
+            response = client.get(
+                '/api/organizations/members/invite/accept?token=inv-test-token-123',
+                follow_redirects=False,
+            )
+
+            assert response.status_code == 302
+            assert 'invitation_error=true' in response.headers.get('location', '')
+
+
+class TestCreateInvitationBatchEndpoint:
+    """Test cases for the batch invitation creation endpoint."""
+
+    @pytest.fixture
+    def batch_app(self):
+        """Create a FastAPI app with dependency overrides for batch tests."""
+        from openhands.server.user_auth import get_user_id
+
+        app = FastAPI()
+        app.include_router(invitation_router)
+
+        # Override the get_user_id dependency
+        app.dependency_overrides[get_user_id] = (
+            lambda: '87654321-4321-8765-4321-876543218765'
+        )
+
+        return app
+
+    @pytest.fixture
+    def batch_client(self, batch_app):
+        """Create a test client with dependency overrides."""
+        return TestClient(batch_app)
+
+    @pytest.fixture
+    def mock_invitation(self):
+        """Create a mock invitation."""
+        from datetime import datetime
+
+        invitation = MagicMock()
+        invitation.id = 1
+        invitation.email = 'alice@example.com'
+        invitation.role = MagicMock(name='member')
+        invitation.role.name = 'member'
+        invitation.role_id = 3
+        invitation.status = 'pending'
+        invitation.created_at = datetime(2026, 2, 17, 10, 0, 0)
+        invitation.expires_at = datetime(2026, 2, 24, 10, 0, 0)
+        return invitation
+
+    @pytest.mark.asyncio
+    async def test_batch_create_returns_successful_invitations(
+        self, batch_client, mock_invitation
+    ):
+        """Test that batch creation returns successful invitations."""
+        mock_invitation_2 = MagicMock()
+        mock_invitation_2.id = 2
+        mock_invitation_2.email = 'bob@example.com'
+        mock_invitation_2.role = MagicMock()
+        mock_invitation_2.role.name = 'member'
+        mock_invitation_2.role_id = 3
+        mock_invitation_2.status = 'pending'
+        mock_invitation_2.created_at = mock_invitation.created_at
+        mock_invitation_2.expires_at = mock_invitation.expires_at
+
+        with (
+            patch(
+                'server.routes.org_invitations.check_rate_limit_by_user_id',
+                new_callable=AsyncMock,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.create_invitations_batch',
+                new_callable=AsyncMock,
+                return_value=([mock_invitation, mock_invitation_2], []),
+            ),
+        ):
+            response = batch_client.post(
+                '/api/organizations/12345678-1234-5678-1234-567812345678/members/invite',
+                json={
+                    'emails': ['alice@example.com', 'bob@example.com'],
+                    'role': 'member',
+                },
+            )
+
+            assert response.status_code == 201
+            data = response.json()
+            assert len(data['successful']) == 2
+            assert len(data['failed']) == 0
+
+    @pytest.mark.asyncio
+    async def test_batch_create_returns_partial_success(
+        self, batch_client, mock_invitation
+    ):
+        """Test that batch creation returns both successful and failed invitations."""
+        failed_emails = [('existing@example.com', 'User is already a member')]
+
+        with (
+            patch(
+                'server.routes.org_invitations.check_rate_limit_by_user_id',
+                new_callable=AsyncMock,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.create_invitations_batch',
+                new_callable=AsyncMock,
+                return_value=([mock_invitation], failed_emails),
+            ),
+        ):
+            response = batch_client.post(
+                '/api/organizations/12345678-1234-5678-1234-567812345678/members/invite',
+                json={
+                    'emails': ['alice@example.com', 'existing@example.com'],
+                    'role': 'member',
+                },
+            )
+
+            assert response.status_code == 201
+            data = response.json()
+            assert len(data['successful']) == 1
+            assert len(data['failed']) == 1
+            assert data['failed'][0]['email'] == 'existing@example.com'
+            assert 'already a member' in data['failed'][0]['error']
+
+    @pytest.mark.asyncio
+    async def test_batch_create_permission_denied_returns_403(self, batch_client):
+        """Test that permission denied returns 403 for entire batch."""
+        from server.routes.org_invitation_models import InsufficientPermissionError
+
+        with (
+            patch(
+                'server.routes.org_invitations.check_rate_limit_by_user_id',
+                new_callable=AsyncMock,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.create_invitations_batch',
+                new_callable=AsyncMock,
+                side_effect=InsufficientPermissionError(
+                    'Only owners and admins can invite'
+                ),
+            ),
+        ):
+            response = batch_client.post(
+                '/api/organizations/12345678-1234-5678-1234-567812345678/members/invite',
+                json={'emails': ['alice@example.com'], 'role': 'member'},
+            )
+
+            assert response.status_code == 403
+            assert 'owners and admins' in response.json()['detail']
+
+    @pytest.mark.asyncio
+    async def test_batch_create_invalid_role_returns_400(self, batch_client):
+        """Test that invalid role returns 400."""
+        with (
+            patch(
+                'server.routes.org_invitations.check_rate_limit_by_user_id',
+                new_callable=AsyncMock,
+            ),
+            patch(
+                'server.routes.org_invitations.OrgInvitationService.create_invitations_batch',
+                new_callable=AsyncMock,
+                side_effect=ValueError('Invalid role: superuser'),
+            ),
+        ):
+            response = batch_client.post(
+                '/api/organizations/12345678-1234-5678-1234-567812345678/members/invite',
+                json={'emails': ['alice@example.com'], 'role': 'superuser'},
+            )
+
+            assert response.status_code == 400
+            assert 'Invalid role' in response.json()['detail']
diff --git a/frontend/__tests__/components/features/auth/login-content.test.tsx b/frontend/__tests__/components/features/auth/login-content.test.tsx
index ae4459980f..1681acb873 100644
--- a/frontend/__tests__/components/features/auth/login-content.test.tsx
+++ b/frontend/__tests__/components/features/auth/login-content.test.tsx
@@ -151,8 +151,9 @@ describe("LoginContent", () => {
     await user.click(githubButton);
 
     // Wait for async handleAuthRedirect to complete
+    // The URL includes state parameter added by handleAuthRedirect
     await waitFor(() => {
-      expect(window.location.href).toBe(mockUrl);
+      expect(window.location.href).toContain(mockUrl);
     });
   });
 
@@ -201,4 +202,103 @@ describe("LoginContent", () => {
 
     expect(screen.getByTestId("terms-and-privacy-notice")).toBeInTheDocument();
   });
+
+  it("should display invitation pending message when hasInvitation is true", () => {
+    render(
+      <MemoryRouter>
+        <LoginContent
+          githubAuthUrl="https://github.com/oauth/authorize"
+          appMode="saas"
+          providersConfigured={["github"]}
+          hasInvitation
+        />
+      </MemoryRouter>,
+    );
+
+    expect(screen.getByText("AUTH$INVITATION_PENDING")).toBeInTheDocument();
+  });
+
+  it("should not display invitation pending message when hasInvitation is false", () => {
+    render(
+      <MemoryRouter>
+        <LoginContent
+          githubAuthUrl="https://github.com/oauth/authorize"
+          appMode="saas"
+          providersConfigured={["github"]}
+          hasInvitation={false}
+        />
+      </MemoryRouter>,
+    );
+
+    expect(
+      screen.queryByText("AUTH$INVITATION_PENDING"),
+    ).not.toBeInTheDocument();
+  });
+
+  it("should call buildOAuthStateData when clicking auth button", async () => {
+    const user = userEvent.setup();
+    const mockBuildOAuthStateData = vi.fn((baseState) => ({
+      ...baseState,
+      invitation_token: "inv-test-token-12345",
+    }));
+
+    render(
+      <MemoryRouter>
+        <LoginContent
+          githubAuthUrl="https://github.com/login/oauth/authorize"
+          appMode="saas"
+          providersConfigured={["github"]}
+          buildOAuthStateData={mockBuildOAuthStateData}
+        />
+      </MemoryRouter>,
+    );
+
+    const githubButton = screen.getByRole("button", {
+      name: "GITHUB$CONNECT_TO_GITHUB",
+    });
+    await user.click(githubButton);
+
+    await waitFor(() => {
+      expect(mockBuildOAuthStateData).toHaveBeenCalled();
+      const callArg = mockBuildOAuthStateData.mock.calls[0][0];
+      expect(callArg).toHaveProperty("redirect_url");
+    });
+  });
+
+  it("should encode state with invitation token when buildOAuthStateData provides token", async () => {
+    const user = userEvent.setup();
+    const mockBuildOAuthStateData = vi.fn((baseState) => ({
+      ...baseState,
+      invitation_token: "inv-test-token-12345",
+    }));
+
+    render(
+      <MemoryRouter>
+        <LoginContent
+          githubAuthUrl="https://github.com/login/oauth/authorize"
+          appMode="saas"
+          providersConfigured={["github"]}
+          buildOAuthStateData={mockBuildOAuthStateData}
+        />
+      </MemoryRouter>,
+    );
+
+    const githubButton = screen.getByRole("button", {
+      name: "GITHUB$CONNECT_TO_GITHUB",
+    });
+    await user.click(githubButton);
+
+    await waitFor(() => {
+      const redirectUrl = window.location.href;
+      // The URL should contain an encoded state parameter
+      expect(redirectUrl).toContain("state=");
+      // Decode and verify the state contains invitation_token
+      const url = new URL(redirectUrl);
+      const state = url.searchParams.get("state");
+      if (state) {
+        const decodedState = JSON.parse(atob(state));
+        expect(decodedState.invitation_token).toBe("inv-test-token-12345");
+      }
+    });
+  });
 });
diff --git a/frontend/__tests__/hooks/use-invitation.test.ts b/frontend/__tests__/hooks/use-invitation.test.ts
new file mode 100644
index 0000000000..9de4d47781
--- /dev/null
+++ b/frontend/__tests__/hooks/use-invitation.test.ts
@@ -0,0 +1,170 @@
+import { act, renderHook } from "@testing-library/react";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const INVITATION_TOKEN_KEY = "openhands_invitation_token";
+
+// Mock setSearchParams function
+const mockSetSearchParams = vi.fn();
+
+// Default mock searchParams
+let mockSearchParamsData: Record<string, string> = {};
+
+// Mock react-router
+vi.mock("react-router", () => ({
+  useSearchParams: () => [
+    {
+      get: (key: string) => mockSearchParamsData[key] || null,
+      has: (key: string) => key in mockSearchParamsData,
+    },
+    mockSetSearchParams,
+  ],
+}));
+
+// Import after mocking
+import { useInvitation } from "#/hooks/use-invitation";
+
+describe("useInvitation", () => {
+  beforeEach(() => {
+    // Clear localStorage before each test
+    localStorage.clear();
+    // Reset mock data
+    mockSearchParamsData = {};
+    mockSetSearchParams.mockClear();
+  });
+
+  afterEach(() => {
+    vi.clearAllMocks();
+  });
+
+  describe("initialization", () => {
+    it("should initialize with null token when localStorage is empty", () => {
+      // Arrange - localStorage is empty (cleared in beforeEach)
+
+      // Act
+      const { result } = renderHook(() => useInvitation());
+
+      // Assert
+      expect(result.current.invitationToken).toBeNull();
+      expect(result.current.hasInvitation).toBe(false);
+    });
+
+    it("should initialize with token from localStorage if present", () => {
+      // Arrange
+      const storedToken = "inv-stored-token-12345";
+      localStorage.setItem(INVITATION_TOKEN_KEY, storedToken);
+
+      // Act
+      const { result } = renderHook(() => useInvitation());
+
+      // Assert
+      expect(result.current.invitationToken).toBe(storedToken);
+      expect(result.current.hasInvitation).toBe(true);
+    });
+  });
+
+  describe("URL token capture", () => {
+    it("should capture invitation_token from URL and store in localStorage", () => {
+      // Arrange
+      const urlToken = "inv-url-token-67890";
+      mockSearchParamsData = { invitation_token: urlToken };
+
+      // Act
+      renderHook(() => useInvitation());
+
+      // Assert
+      expect(localStorage.getItem(INVITATION_TOKEN_KEY)).toBe(urlToken);
+      expect(mockSetSearchParams).toHaveBeenCalled();
+    });
+  });
+
+  describe("completion cleanup", () => {
+    it("should clear localStorage when email_mismatch param is present", () => {
+      // Arrange
+      const storedToken = "inv-token-to-clear";
+      localStorage.setItem(INVITATION_TOKEN_KEY, storedToken);
+      mockSearchParamsData = { email_mismatch: "true" };
+
+      // Act
+      const { result } = renderHook(() => useInvitation());
+
+      // Assert
+      expect(localStorage.getItem(INVITATION_TOKEN_KEY)).toBeNull();
+      expect(mockSetSearchParams).toHaveBeenCalled();
+    });
+
+    it("should clear localStorage when invitation_success param is present", () => {
+      // Arrange
+      const storedToken = "inv-token-to-clear";
+      localStorage.setItem(INVITATION_TOKEN_KEY, storedToken);
+      mockSearchParamsData = { invitation_success: "true" };
+
+      // Act
+      renderHook(() => useInvitation());
+
+      // Assert
+      expect(localStorage.getItem(INVITATION_TOKEN_KEY)).toBeNull();
+    });
+
+    it("should clear localStorage when invitation_expired param is present", () => {
+      // Arrange
+      localStorage.setItem(INVITATION_TOKEN_KEY, "inv-token");
+      mockSearchParamsData = { invitation_expired: "true" };
+
+      // Act
+      renderHook(() => useInvitation());
+
+      // Assert
+      expect(localStorage.getItem(INVITATION_TOKEN_KEY)).toBeNull();
+    });
+  });
+
+  describe("buildOAuthStateData", () => {
+    it("should include invitation_token in OAuth state when token is present", () => {
+      // Arrange
+      const token = "inv-oauth-token-12345";
+      localStorage.setItem(INVITATION_TOKEN_KEY, token);
+
+      const { result } = renderHook(() => useInvitation());
+      const baseState = { redirect_url: "/dashboard" };
+
+      // Act
+      const stateData = result.current.buildOAuthStateData(baseState);
+
+      // Assert
+      expect(stateData.invitation_token).toBe(token);
+      expect(stateData.redirect_url).toBe("/dashboard");
+    });
+
+    it("should not include invitation_token when no token is present", () => {
+      // Arrange - no token in localStorage
+
+      const { result } = renderHook(() => useInvitation());
+      const baseState = { redirect_url: "/dashboard" };
+
+      // Act
+      const stateData = result.current.buildOAuthStateData(baseState);
+
+      // Assert
+      expect(stateData.invitation_token).toBeUndefined();
+      expect(stateData.redirect_url).toBe("/dashboard");
+    });
+  });
+
+  describe("clearInvitation", () => {
+    it("should remove token from localStorage when called", () => {
+      // Arrange
+      localStorage.setItem(INVITATION_TOKEN_KEY, "inv-token-to-clear");
+      const { result } = renderHook(() => useInvitation());
+
+      // Act
+      act(() => {
+        result.current.clearInvitation();
+      });
+
+      // Assert
+      expect(localStorage.getItem(INVITATION_TOKEN_KEY)).toBeNull();
+      expect(result.current.invitationToken).toBeNull();
+      expect(result.current.hasInvitation).toBe(false);
+    });
+  });
+});
diff --git a/frontend/__tests__/routes/login.test.tsx b/frontend/__tests__/routes/login.test.tsx
index 3abb9557ee..2b63a8c98e 100644
--- a/frontend/__tests__/routes/login.test.tsx
+++ b/frontend/__tests__/routes/login.test.tsx
@@ -57,6 +57,22 @@ vi.mock("#/hooks/use-tracking", () => ({
   }),
 }));
 
+const { useInvitationMock, buildOAuthStateDataMock } = vi.hoisted(() => ({
+  useInvitationMock: vi.fn(() => ({
+    invitationToken: null as string | null,
+    hasInvitation: false,
+    buildOAuthStateData: (baseState: Record<string, string>) => baseState,
+    clearInvitation: vi.fn(),
+  })),
+  buildOAuthStateDataMock: vi.fn(
+    (baseState: Record<string, string>) => baseState,
+  ),
+}));
+
+vi.mock("#/hooks/use-invitation", () => ({
+  useInvitation: () => useInvitationMock(),
+}));
+
 const RouterStub = createRoutesStub([
   {
     Component: LoginPage,
@@ -234,7 +250,8 @@ describe("LoginPage", () => {
       });
       await user.click(githubButton);
 
-      expect(window.location.href).toBe(mockUrl);
+      // URL includes state parameter added by handleAuthRedirect
+      expect(window.location.href).toContain(mockUrl);
     });
 
     it("should redirect to GitLab auth URL when GitLab button is clicked", async () => {
@@ -255,7 +272,8 @@ describe("LoginPage", () => {
       });
       await user.click(gitlabButton);
 
-      expect(window.location.href).toBe("https://gitlab.com/oauth/authorize");
+      // URL includes state parameter added by handleAuthRedirect
+      expect(window.location.href).toContain("https://gitlab.com/oauth/authorize");
     });
 
     it("should redirect to Bitbucket auth URL when Bitbucket button is clicked", async () => {
@@ -282,7 +300,8 @@ describe("LoginPage", () => {
       });
       await user.click(bitbucketButton);
 
-      expect(window.location.href).toBe(
+      // URL includes state parameter added by handleAuthRedirect
+      expect(window.location.href).toContain(
         "https://bitbucket.org/site/oauth2/authorize",
       );
     });
@@ -479,4 +498,137 @@ describe("LoginPage", () => {
       });
     });
   });
+
+  describe("Invitation Flow", () => {
+    it("should display invitation pending message when hasInvitation is true", async () => {
+      useInvitationMock.mockReturnValue({
+        invitationToken: "inv-test-token-12345",
+        hasInvitation: true,
+        buildOAuthStateData: buildOAuthStateDataMock,
+        clearInvitation: vi.fn(),
+      });
+
+      render(<RouterStub initialEntries={["/login"]} />, {
+        wrapper: createWrapper(),
+      });
+
+      await waitFor(() => {
+        expect(screen.getByText("AUTH$INVITATION_PENDING")).toBeInTheDocument();
+      });
+    });
+
+    it("should not display invitation pending message when hasInvitation is false", async () => {
+      useInvitationMock.mockReturnValue({
+        invitationToken: null,
+        hasInvitation: false,
+        buildOAuthStateData: buildOAuthStateDataMock,
+        clearInvitation: vi.fn(),
+      });
+
+      render(<RouterStub initialEntries={["/login"]} />, {
+        wrapper: createWrapper(),
+      });
+
+      await waitFor(() => {
+        expect(screen.getByTestId("login-content")).toBeInTheDocument();
+      });
+
+      expect(
+        screen.queryByText("AUTH$INVITATION_PENDING"),
+      ).not.toBeInTheDocument();
+    });
+
+    it("should pass buildOAuthStateData to LoginContent for OAuth state encoding", async () => {
+      const user = userEvent.setup();
+      const mockBuildOAuthStateData = vi.fn((baseState: Record<string, string>) => ({
+        ...baseState,
+        invitation_token: "inv-test-token-12345",
+      }));
+
+      useInvitationMock.mockReturnValue({
+        invitationToken: "inv-test-token-12345",
+        hasInvitation: true,
+        buildOAuthStateData: mockBuildOAuthStateData,
+        clearInvitation: vi.fn(),
+      });
+
+      render(<RouterStub initialEntries={["/login"]} />, {
+        wrapper: createWrapper(),
+      });
+
+      await waitFor(() => {
+        expect(
+          screen.getByRole("button", { name: "GITHUB$CONNECT_TO_GITHUB" }),
+        ).toBeInTheDocument();
+      });
+
+      const githubButton = screen.getByRole("button", {
+        name: "GITHUB$CONNECT_TO_GITHUB",
+      });
+      await user.click(githubButton);
+
+      // buildOAuthStateData should have been called during the OAuth redirect
+      expect(mockBuildOAuthStateData).toHaveBeenCalled();
+    });
+
+    it("should include invitation token in OAuth state when invitation is present", async () => {
+      const user = userEvent.setup();
+      const mockBuildOAuthStateData = vi.fn((baseState: Record<string, string>) => ({
+        ...baseState,
+        invitation_token: "inv-test-token-12345",
+      }));
+
+      useInvitationMock.mockReturnValue({
+        invitationToken: "inv-test-token-12345",
+        hasInvitation: true,
+        buildOAuthStateData: mockBuildOAuthStateData,
+        clearInvitation: vi.fn(),
+      });
+
+      render(<RouterStub initialEntries={["/login"]} />, {
+        wrapper: createWrapper(),
+      });
+
+      await waitFor(() => {
+        expect(
+          screen.getByRole("button", { name: "GITHUB$CONNECT_TO_GITHUB" }),
+        ).toBeInTheDocument();
+      });
+
+      const githubButton = screen.getByRole("button", {
+        name: "GITHUB$CONNECT_TO_GITHUB",
+      });
+      await user.click(githubButton);
+
+      // Verify the redirect URL contains the state with invitation token
+      await waitFor(() => {
+        expect(window.location.href).toContain("state=");
+      });
+
+      // Decode and verify the state contains invitation_token
+      const url = new URL(window.location.href);
+      const state = url.searchParams.get("state");
+      if (state) {
+        const decodedState = JSON.parse(atob(state));
+        expect(decodedState.invitation_token).toBe("inv-test-token-12345");
+      }
+    });
+
+    it("should handle login with invitation_token URL parameter", async () => {
+      useInvitationMock.mockReturnValue({
+        invitationToken: "inv-url-token-67890",
+        hasInvitation: true,
+        buildOAuthStateData: buildOAuthStateDataMock,
+        clearInvitation: vi.fn(),
+      });
+
+      render(<RouterStub initialEntries={["/login?invitation_token=inv-url-token-67890"]} />, {
+        wrapper: createWrapper(),
+      });
+
+      await waitFor(() => {
+        expect(screen.getByText("AUTH$INVITATION_PENDING")).toBeInTheDocument();
+      });
+    });
+  });
 });
diff --git a/frontend/__tests__/routes/root-layout.test.tsx b/frontend/__tests__/routes/root-layout.test.tsx
index 0fd9f64deb..107841c71d 100644
--- a/frontend/__tests__/routes/root-layout.test.tsx
+++ b/frontend/__tests__/routes/root-layout.test.tsx
@@ -42,6 +42,15 @@ vi.mock("#/utils/custom-toast-handlers", () => ({
   displaySuccessToast: vi.fn(),
 }));
 
+vi.mock("#/hooks/use-invitation", () => ({
+  useInvitation: () => ({
+    invitationToken: null,
+    hasInvitation: false,
+    buildOAuthStateData: (baseState: Record<string, string>) => baseState,
+    clearInvitation: vi.fn(),
+  }),
+}));
+
 function LoginStub() {
   const [searchParams] = useSearchParams();
   const emailVerificationRequired =
@@ -353,4 +362,68 @@ describe("MainApp", () => {
       );
     });
   });
+
+  describe("Invitation URL Parameters", () => {
+    beforeEach(() => {
+      vi.spyOn(AuthService, "authenticate").mockRejectedValue({
+        response: { status: 401 },
+        isAxiosError: true,
+      });
+    });
+
+    it("should redirect to login when email_mismatch=true is in query params", async () => {
+      renderMainApp(["/?email_mismatch=true"]);
+
+      await waitFor(
+        () => {
+          expect(screen.getByTestId("login-page")).toBeInTheDocument();
+        },
+        { timeout: 2000 },
+      );
+    });
+
+    it("should redirect to login when invitation_success=true is in query params", async () => {
+      renderMainApp(["/?invitation_success=true"]);
+
+      await waitFor(
+        () => {
+          expect(screen.getByTestId("login-page")).toBeInTheDocument();
+        },
+        { timeout: 2000 },
+      );
+    });
+
+    it("should redirect to login when invitation_expired=true is in query params", async () => {
+      renderMainApp(["/?invitation_expired=true"]);
+
+      await waitFor(
+        () => {
+          expect(screen.getByTestId("login-page")).toBeInTheDocument();
+        },
+        { timeout: 2000 },
+      );
+    });
+
+    it("should redirect to login when invitation_invalid=true is in query params", async () => {
+      renderMainApp(["/?invitation_invalid=true"]);
+
+      await waitFor(
+        () => {
+          expect(screen.getByTestId("login-page")).toBeInTheDocument();
+        },
+        { timeout: 2000 },
+      );
+    });
+
+    it("should redirect to login when already_member=true is in query params", async () => {
+      renderMainApp(["/?already_member=true"]);
+
+      await waitFor(
+        () => {
+          expect(screen.getByTestId("login-page")).toBeInTheDocument();
+        },
+        { timeout: 2000 },
+      );
+    });
+  });
 });
diff --git a/frontend/src/components/features/auth/login-content.tsx b/frontend/src/components/features/auth/login-content.tsx
index 1938929c91..8ab3d72f59 100644
--- a/frontend/src/components/features/auth/login-content.tsx
+++ b/frontend/src/components/features/auth/login-content.tsx
@@ -21,6 +21,10 @@ export interface LoginContentProps {
   emailVerified?: boolean;
   hasDuplicatedEmail?: boolean;
   recaptchaBlocked?: boolean;
+  hasInvitation?: boolean;
+  buildOAuthStateData?: (
+    baseStateData: Record<string, string>,
+  ) => Record<string, string>;
 }
 
 export function LoginContent({
@@ -31,6 +35,8 @@ export function LoginContent({
   emailVerified = false,
   hasDuplicatedEmail = false,
   recaptchaBlocked = false,
+  hasInvitation = false,
+  buildOAuthStateData,
 }: LoginContentProps) {
   const { t } = useTranslation();
   const { trackLoginButtonClick } = useTracking();
@@ -59,31 +65,36 @@ export function LoginContent({
   ) => {
     trackLoginButtonClick({ provider });
 
-    if (!config?.recaptcha_site_key || !recaptchaReady) {
-      // No reCAPTCHA or token generation failed - redirect normally
-      window.location.href = redirectUrl;
-      return;
+    const url = new URL(redirectUrl);
+    const currentState =
+      url.searchParams.get("state") || window.location.origin;
+
+    // Build base state data
+    let stateData: Record<string, string> = {
+      redirect_url: currentState,
+    };
+
+    // Add invitation token if present
+    if (buildOAuthStateData) {
+      stateData = buildOAuthStateData(stateData);
     }
 
-    // If reCAPTCHA is configured, encode token in OAuth state
-    try {
-      const token = await executeRecaptcha("LOGIN");
-      if (token) {
-        const url = new URL(redirectUrl);
-        const currentState =
-          url.searchParams.get("state") || window.location.origin;
-
-        // Encode state with reCAPTCHA token for backend verification
-        const stateData = {
-          redirect_url: currentState,
-          recaptcha_token: token,
-        };
-        url.searchParams.set("state", btoa(JSON.stringify(stateData)));
-        window.location.href = url.toString();
+    // If reCAPTCHA is configured, add token to state
+    if (config?.recaptcha_site_key && recaptchaReady) {
+      try {
+        const token = await executeRecaptcha("LOGIN");
+        if (token) {
+          stateData.recaptcha_token = token;
+        }
+      } catch (err) {
+        displayErrorToast(t(I18nKey.AUTH$RECAPTCHA_BLOCKED));
+        return;
       }
-    } catch (err) {
-      displayErrorToast(t(I18nKey.AUTH$RECAPTCHA_BLOCKED));
     }
+
+    // Encode state and redirect
+    url.searchParams.set("state", btoa(JSON.stringify(stateData)));
+    window.location.href = url.toString();
   };
 
   const handleGitHubAuth = () => {
@@ -123,6 +134,10 @@ export function LoginContent({
   const buttonBaseClasses =
     "w-[301.5px] h-10 rounded p-2 flex items-center justify-center cursor-pointer transition-opacity hover:opacity-90 disabled:opacity-50 disabled:cursor-not-allowed";
   const buttonLabelClasses = "text-sm font-medium leading-5 px-1";
+
+  const shouldShownHelperText =
+    emailVerified || hasDuplicatedEmail || recaptchaBlocked || hasInvitation;
+
   return (
     <div
       className="flex flex-col items-center w-full gap-12.5"
@@ -136,20 +151,29 @@ export function LoginContent({
         {t(I18nKey.AUTH$LETS_GET_STARTED)}
       </h1>
 
-      {emailVerified && (
-        <p className="text-sm text-muted-foreground text-center">
-          {t(I18nKey.AUTH$EMAIL_VERIFIED_PLEASE_LOGIN)}
-        </p>
-      )}
-      {hasDuplicatedEmail && (
-        <p className="text-sm text-danger text-center">
-          {t(I18nKey.AUTH$DUPLICATE_EMAIL_ERROR)}
-        </p>
-      )}
-      {recaptchaBlocked && (
-        <p className="text-sm text-danger text-center max-w-125">
-          {t(I18nKey.AUTH$RECAPTCHA_BLOCKED)}
-        </p>
+      {shouldShownHelperText && (
+        <div className="flex flex-col items-center gap-3">
+          {emailVerified && (
+            <p className="text-sm text-muted-foreground text-center">
+              {t(I18nKey.AUTH$EMAIL_VERIFIED_PLEASE_LOGIN)}
+            </p>
+          )}
+          {hasDuplicatedEmail && (
+            <p className="text-sm text-danger text-center">
+              {t(I18nKey.AUTH$DUPLICATE_EMAIL_ERROR)}
+            </p>
+          )}
+          {recaptchaBlocked && (
+            <p className="text-sm text-danger text-center max-w-125">
+              {t(I18nKey.AUTH$RECAPTCHA_BLOCKED)}
+            </p>
+          )}
+          {hasInvitation && (
+            <p className="text-sm text-muted-foreground text-center">
+              {t(I18nKey.AUTH$INVITATION_PENDING)}
+            </p>
+          )}
+        </div>
       )}
 
       <div className="flex flex-col items-center gap-3">
diff --git a/frontend/src/hooks/use-invitation.ts b/frontend/src/hooks/use-invitation.ts
new file mode 100644
index 0000000000..14719ae7bb
--- /dev/null
+++ b/frontend/src/hooks/use-invitation.ts
@@ -0,0 +1,119 @@
+import React from "react";
+import { useSearchParams } from "react-router";
+
+const INVITATION_TOKEN_KEY = "openhands_invitation_token";
+
+interface UseInvitationReturn {
+  /** The invitation token, if present */
+  invitationToken: string | null;
+  /** Whether there is an active invitation */
+  hasInvitation: boolean;
+  /** Clear the stored invitation token */
+  clearInvitation: () => void;
+  /** Build OAuth state data including invitation token if present */
+  buildOAuthStateData: (
+    baseStateData: Record<string, string>,
+  ) => Record<string, string>;
+}
+
+/**
+ * Hook to manage organization invitation tokens during the login flow.
+ *
+ * This hook:
+ * 1. Reads invitation_token from URL query params on mount
+ * 2. Persists the token in localStorage (survives page refresh and works across tabs)
+ * 3. Provides the token for inclusion in OAuth state
+ * 4. Provides cleanup method after successful authentication
+ *
+ * The invitation token flow:
+ * 1. User clicks invitation link → /api/invitations/accept?token=xxx
+ * 2. Backend redirects to /login?invitation_token=xxx
+ * 3. This hook captures token and stores in localStorage
+ * 4. When user clicks login button, token is included in OAuth state
+ * 5. After auth callback processes invitation, frontend clears the token
+ *
+ * Note: localStorage is used instead of sessionStorage to support scenarios where
+ * the user opens the email verification link in a new tab/browser window.
+ */
+export function useInvitation(): UseInvitationReturn {
+  const [searchParams, setSearchParams] = useSearchParams();
+  const [invitationToken, setInvitationToken] = React.useState<string | null>(
+    () => {
+      // Initialize from localStorage (persists across tabs and page refreshes)
+      if (typeof window !== "undefined") {
+        return localStorage.getItem(INVITATION_TOKEN_KEY);
+      }
+      return null;
+    },
+  );
+
+  // Capture invitation token from URL and persist to localStorage
+  // This only runs on the login page where the hook is used
+  React.useEffect(() => {
+    const tokenFromUrl = searchParams.get("invitation_token");
+
+    if (tokenFromUrl) {
+      // Store in localStorage for persistence across tabs and refreshes
+      localStorage.setItem(INVITATION_TOKEN_KEY, tokenFromUrl);
+      setInvitationToken(tokenFromUrl);
+
+      // Remove token from URL to clean up (prevents token exposure in browser history)
+      const newSearchParams = new URLSearchParams(searchParams);
+      newSearchParams.delete("invitation_token");
+      setSearchParams(newSearchParams, { replace: true });
+    }
+  }, [searchParams, setSearchParams]);
+
+  // Clear invitation token when invitation flow completes (success or failure)
+  // These query params are set by the backend after processing the invitation
+  React.useEffect(() => {
+    const invitationCompleted =
+      searchParams.has("invitation_success") ||
+      searchParams.has("invitation_expired") ||
+      searchParams.has("invitation_invalid") ||
+      searchParams.has("invitation_error") ||
+      searchParams.has("already_member") ||
+      searchParams.has("email_mismatch");
+
+    if (invitationCompleted) {
+      localStorage.removeItem(INVITATION_TOKEN_KEY);
+      setInvitationToken(null);
+
+      // Remove invitation params from URL to clean up
+      const newSearchParams = new URLSearchParams(searchParams);
+      newSearchParams.delete("invitation_success");
+      newSearchParams.delete("invitation_expired");
+      newSearchParams.delete("invitation_invalid");
+      newSearchParams.delete("invitation_error");
+      newSearchParams.delete("already_member");
+      newSearchParams.delete("email_mismatch");
+      setSearchParams(newSearchParams, { replace: true });
+    }
+  }, [searchParams, setSearchParams]);
+
+  const clearInvitation = React.useCallback(() => {
+    localStorage.removeItem(INVITATION_TOKEN_KEY);
+    setInvitationToken(null);
+  }, []);
+
+  const buildOAuthStateData = React.useCallback(
+    (baseStateData: Record<string, string>): Record<string, string> => {
+      const stateData = { ...baseStateData };
+
+      // Include invitation token in state if present
+      if (invitationToken) {
+        stateData.invitation_token = invitationToken;
+      }
+
+      return stateData;
+    },
+    [invitationToken],
+  );
+
+  return {
+    invitationToken,
+    hasInvitation: invitationToken !== null,
+    clearInvitation,
+    buildOAuthStateData,
+  };
+}
diff --git a/frontend/src/i18n/declaration.ts b/frontend/src/i18n/declaration.ts
index b570bdbbaa..2d9599e810 100644
--- a/frontend/src/i18n/declaration.ts
+++ b/frontend/src/i18n/declaration.ts
@@ -763,6 +763,7 @@ export enum I18nKey {
   AUTH$DUPLICATE_EMAIL_ERROR = "AUTH$DUPLICATE_EMAIL_ERROR",
   AUTH$RECAPTCHA_BLOCKED = "AUTH$RECAPTCHA_BLOCKED",
   AUTH$LETS_GET_STARTED = "AUTH$LETS_GET_STARTED",
+  AUTH$INVITATION_PENDING = "AUTH$INVITATION_PENDING",
   COMMON$TERMS_OF_SERVICE = "COMMON$TERMS_OF_SERVICE",
   COMMON$AND = "COMMON$AND",
   COMMON$PRIVACY_POLICY = "COMMON$PRIVACY_POLICY",
diff --git a/frontend/src/i18n/translation.json b/frontend/src/i18n/translation.json
index 787f287c6d..91530fe633 100644
--- a/frontend/src/i18n/translation.json
+++ b/frontend/src/i18n/translation.json
@@ -12207,6 +12207,22 @@
     "de": "Lass uns anfangen",
     "uk": "Почнімо"
   },
+  "AUTH$INVITATION_PENDING": {
+    "en": "Sign in to accept your organization invitation",
+    "ja": "組織への招待を受け入れるにはサインインしてください",
+    "zh-CN": "登录以接受您的组织邀请",
+    "zh-TW": "登入以接受您的組織邀請",
+    "ko-KR": "조직 초대를 수락하려면 로그인하세요",
+    "no": "Logg inn for å godta organisasjonsinvitasjonen din",
+    "it": "Accedi per accettare l'invito della tua organizzazione",
+    "pt": "Faça login para aceitar o convite da sua organização",
+    "es": "Inicia sesión para aceptar la invitación de tu organización",
+    "ar": "سجّل الدخول لقبول دعوة مؤسستك",
+    "fr": "Connectez-vous pour accepter l'invitation de votre organisation",
+    "tr": "Organizasyon davetinizi kabul etmek için giriş yapın",
+    "de": "Melden Sie sich an, um Ihre Organisationseinladung anzunehmen",
+    "uk": "Увійдіть, щоб прийняти запрошення до організації"
+  },
   "COMMON$TERMS_OF_SERVICE": {
     "en": "Terms of Service",
     "ja": "利用規約",
diff --git a/frontend/src/root.tsx b/frontend/src/root.tsx
index 6f1f896b4d..d2cc4f64f1 100644
--- a/frontend/src/root.tsx
+++ b/frontend/src/root.tsx
@@ -10,6 +10,7 @@ import "./tailwind.css";
 import "./index.css";
 import React from "react";
 import { Toaster } from "react-hot-toast";
+import { useInvitation } from "#/hooks/use-invitation";
 
 export function Layout({ children }: { children: React.ReactNode }) {
   return (
@@ -37,5 +38,9 @@ export const meta: MetaFunction = () => [
 ];
 
 export default function App() {
+  // Handle invitation token cleanup when invitation flow completes
+  // This runs on all pages to catch redirects from auth callback
+  useInvitation();
+
   return <Outlet />;
 }
diff --git a/frontend/src/routes/login.tsx b/frontend/src/routes/login.tsx
index 0de57b27b9..874743aa6e 100644
--- a/frontend/src/routes/login.tsx
+++ b/frontend/src/routes/login.tsx
@@ -4,6 +4,7 @@ import { useIsAuthed } from "#/hooks/query/use-is-authed";
 import { useConfig } from "#/hooks/query/use-config";
 import { useGitHubAuthUrl } from "#/hooks/use-github-auth-url";
 import { useEmailVerification } from "#/hooks/use-email-verification";
+import { useInvitation } from "#/hooks/use-invitation";
 import { LoginContent } from "#/components/features/auth/login-content";
 import { EmailVerificationModal } from "#/components/features/waitlist/email-verification-modal";
 
@@ -23,6 +24,8 @@ export default function LoginPage() {
     userId,
   } = useEmailVerification();
 
+  const { hasInvitation, buildOAuthStateData } = useInvitation();
+
   const gitHubAuthUrl = useGitHubAuthUrl({
     appMode: config.data?.app_mode || null,
     authUrl: config.data?.auth_url,
@@ -69,6 +72,8 @@ export default function LoginPage() {
           emailVerified={emailVerified}
           hasDuplicatedEmail={hasDuplicatedEmail}
           recaptchaBlocked={recaptchaBlocked}
+          hasInvitation={hasInvitation}
+          buildOAuthStateData={buildOAuthStateData}
         />
       </main>