diff --git a/Makefile b/Makefile
index 8f588ed..8d66848 100644
--- a/Makefile
+++ b/Makefile
@@ -23,6 +23,9 @@ db:
 db-stop:
 	docker compose down
 
+db-clean:
+	docker compose down -v
+
 db-ready:
 	@docker compose up -d db
 	@echo "Waiting for PostgreSQL to be ready..."
@@ -42,13 +45,13 @@ dev:
 	cd frontend && npm run dev & \
 	wait
 
-test-backend: db-ready
+test-backend: db-clean db-ready
 	cd backend && uv run pytest -v
 
 test-frontend:
 	cd frontend && npm run test
 
-test-e2e:
+test-e2e: db-clean db-ready
 	./scripts/e2e.sh
 
 test: test-backend test-frontend test-e2e
diff --git a/backend/main.py b/backend/main.py
index b5e18f5..73598e1 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -6,6 +6,7 @@ from fastapi import FastAPI, Depends, HTTPException, Response, status, Query
 from fastapi.middleware.cors import CORSMiddleware
 from pydantic import BaseModel, EmailStr
 from sqlalchemy import select, func, desc
+from sqlalchemy.exc import IntegrityError
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from auth import (
@@ -25,7 +26,7 @@ from auth import (
 from database import engine, get_db, Base
 from models import Counter, User, SumRecord, CounterRecord, Permission, Role, ROLE_REGULAR, Invite, InviteStatus
 from validation import validate_profile_fields
-from invite_utils import generate_invite_identifier, normalize_identifier
+from invite_utils import generate_invite_identifier, normalize_identifier, is_valid_identifier_format
 
 
 R = TypeVar("R", bound=BaseModel)
@@ -115,6 +116,10 @@ async def check_invite(
     """Check if an invite is valid and can be used for signup."""
     normalized = normalize_identifier(identifier)
     
+    # Validate format before querying database
+    if not is_valid_identifier_format(normalized):
+        return InviteCheckResponse(valid=False, error="Invalid invite code format")
+    
     result = await db.execute(
         select(Invite).where(Invite.identifier == normalized)
     )
@@ -441,18 +446,23 @@ async def require_regular_user(
     return current_user
 
 
+async def get_godfather_email(db: AsyncSession, godfather_id: int | None) -> str | None:
+    """Get the email of a godfather user by ID."""
+    if not godfather_id:
+        return None
+    result = await db.execute(
+        select(User.email).where(User.id == godfather_id)
+    )
+    return result.scalar_one_or_none()
+
+
 @app.get("/api/profile", response_model=ProfileResponse)
 async def get_profile(
     current_user: User = Depends(require_regular_user),
     db: AsyncSession = Depends(get_db),
 ):
     """Get the current user's profile (contact details and godfather)."""
-    godfather_email = None
-    if current_user.godfather_id:
-        result = await db.execute(
-            select(User.email).where(User.id == current_user.godfather_id)
-        )
-        godfather_email = result.scalar_one_or_none()
+    godfather_email = await get_godfather_email(db, current_user.godfather_id)
     
     return ProfileResponse(
         contact_email=current_user.contact_email,
@@ -493,13 +503,7 @@ async def update_profile(
     await db.commit()
     await db.refresh(current_user)
     
-    # Get godfather email if set
-    godfather_email = None
-    if current_user.godfather_id:
-        gf_result = await db.execute(
-            select(User.email).where(User.id == current_user.godfather_id)
-        )
-        godfather_email = gf_result.scalar_one_or_none()
+    godfather_email = await get_godfather_email(db, current_user.godfather_id)
     
     return ProfileResponse(
         contact_email=current_user.contact_email,
@@ -530,6 +534,9 @@ class InviteResponse(BaseModel):
     revoked_at: datetime | None
 
 
+MAX_INVITE_COLLISION_RETRIES = 3
+
+
 @app.post("/api/admin/invites", response_model=InviteResponse)
 async def create_invite(
     data: InviteCreate,
@@ -537,33 +544,46 @@ async def create_invite(
     _current_user: User = Depends(require_permission(Permission.MANAGE_INVITES)),
 ):
     """Create a new invite for a specified godfather user."""
-    # Validate godfather exists
-    result = await db.execute(select(User).where(User.id == data.godfather_id))
-    godfather = result.scalar_one_or_none()
-    if not godfather:
+    # Validate godfather exists and get their info
+    result = await db.execute(
+        select(User.id, User.email).where(User.id == data.godfather_id)
+    )
+    godfather_row = result.one_or_none()
+    if not godfather_row:
         raise HTTPException(
             status_code=status.HTTP_400_BAD_REQUEST,
             detail="Godfather user not found",
         )
+    godfather_id, godfather_email = godfather_row
     
-    # Generate unique identifier
-    identifier = generate_invite_identifier()
-    
-    # Create invite
-    invite = Invite(
-        identifier=identifier,
-        godfather_id=godfather.id,
-        status=InviteStatus.READY,
-    )
-    db.add(invite)
-    await db.commit()
-    await db.refresh(invite)
+    # Try to create invite with retry on collision
+    invite: Invite | None = None
+    for attempt in range(MAX_INVITE_COLLISION_RETRIES):
+        identifier = generate_invite_identifier()
+        invite = Invite(
+            identifier=identifier,
+            godfather_id=godfather_id,
+            status=InviteStatus.READY,
+        )
+        db.add(invite)
+        try:
+            await db.commit()
+            await db.refresh(invite)
+            break
+        except IntegrityError:
+            await db.rollback()
+            if attempt == MAX_INVITE_COLLISION_RETRIES - 1:
+                raise HTTPException(
+                    status_code=status.HTTP_500_INTERNAL_SERVER_ERROR,
+                    detail="Failed to generate unique invite code. Please try again.",
+                )
     
+    assert invite is not None  # We either succeeded or raised an exception above
     return InviteResponse(
         id=invite.id,
         identifier=invite.identifier,
         godfather_id=invite.godfather_id,
-        godfather_email=godfather.email,
+        godfather_email=godfather_email,
         status=invite.status.value,
         used_by_id=invite.used_by_id,
         used_by_email=None,
@@ -596,26 +616,18 @@ async def get_my_invites(
     )
     invites = result.scalars().all()
     
-    responses = []
-    for invite in invites:
-        used_by_email = None
-        if invite.used_by_id:
-            # Fetch the user who used this invite
-            user_result = await db.execute(
-                select(User.email).where(User.id == invite.used_by_id)
-            )
-            used_by_email = user_result.scalar_one_or_none()
-        
-        responses.append(UserInviteResponse(
+    # Use preloaded used_by relationship (selectin loading)
+    return [
+        UserInviteResponse(
             id=invite.id,
             identifier=invite.identifier,
             status=invite.status.value,
-            used_by_email=used_by_email,
+            used_by_email=invite.used_by.email if invite.used_by else None,
             created_at=invite.created_at,
             spent_at=invite.spent_at,
-        ))
-    
-    return responses
+        )
+        for invite in invites
+    ]
 
 
 # Admin Invite Management
@@ -674,37 +686,23 @@ async def list_all_invites(
     total = count_result.scalar() or 0
     total_pages = (total + per_page - 1) // per_page if total > 0 else 1
     
-    # Get paginated invites
+    # Get paginated invites (relationships loaded via selectin)
     offset = (page - 1) * per_page
     query = query.order_by(desc(Invite.created_at)).offset(offset).limit(per_page)
     result = await db.execute(query)
     invites = result.scalars().all()
     
-    # Build responses with user emails
+    # Build responses using preloaded relationships
     records = []
     for invite in invites:
-        # Get godfather email
-        gf_result = await db.execute(
-            select(User.email).where(User.id == invite.godfather_id)
-        )
-        godfather_email = gf_result.scalar_one()
-        
-        # Get used_by email if applicable
-        used_by_email = None
-        if invite.used_by_id:
-            ub_result = await db.execute(
-                select(User.email).where(User.id == invite.used_by_id)
-            )
-            used_by_email = ub_result.scalar_one_or_none()
-        
         records.append(InviteResponse(
             id=invite.id,
             identifier=invite.identifier,
             godfather_id=invite.godfather_id,
-            godfather_email=godfather_email,
+            godfather_email=invite.godfather.email,
             status=invite.status.value,
             used_by_id=invite.used_by_id,
-            used_by_email=used_by_email,
+            used_by_email=invite.used_by.email if invite.used_by else None,
             created_at=invite.created_at,
             spent_at=invite.spent_at,
             revoked_at=invite.revoked_at,
@@ -746,20 +744,15 @@ async def revoke_invite(
     await db.commit()
     await db.refresh(invite)
     
-    # Get godfather email
-    gf_result = await db.execute(
-        select(User.email).where(User.id == invite.godfather_id)
-    )
-    godfather_email = gf_result.scalar_one()
-    
+    # Use preloaded relationships (selectin loading)
     return InviteResponse(
         id=invite.id,
         identifier=invite.identifier,
         godfather_id=invite.godfather_id,
-        godfather_email=godfather_email,
+        godfather_email=invite.godfather.email,
         status=invite.status.value,
         used_by_id=invite.used_by_id,
-        used_by_email=None,
+        used_by_email=invite.used_by.email if invite.used_by else None,
         created_at=invite.created_at,
         spent_at=invite.spent_at,
         revoked_at=invite.revoked_at,
diff --git a/backend/tests/helpers.py b/backend/tests/helpers.py
index 5ee20c5..e1fa202 100644
--- a/backend/tests/helpers.py
+++ b/backend/tests/helpers.py
@@ -3,7 +3,7 @@ import uuid
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from models import User, Invite, InviteStatus, ROLE_ADMIN
+from models import User, Invite, InviteStatus
 from invite_utils import generate_invite_identifier
 
 
@@ -12,36 +12,32 @@ def unique_email(prefix: str = "test") -> str:
     return f"{prefix}-{uuid.uuid4().hex[:8]}@example.com"
 
 
-async def create_invite_for_registration(db: AsyncSession, godfather_email: str) -> str:
+async def create_invite_for_godfather(db: AsyncSession, godfather_id: int) -> str:
     """
-    Create an invite that can be used for registration.
-    Returns the invite identifier.
+    Create an invite for an existing godfather user.
+    
+    Args:
+        db: Database session
+        godfather_id: ID of the existing user who will be the godfather
+        
+    Returns:
+        The invite identifier.
+        
+    Raises:
+        ValueError: If the godfather user doesn't exist.
     """
-    # Find godfather
-    result = await db.execute(select(User).where(User.email == godfather_email))
+    # Verify godfather exists
+    result = await db.execute(select(User).where(User.id == godfather_id))
     godfather = result.scalar_one_or_none()
     
     if not godfather:
-        # Create a godfather user (admin can create invites)
-        from auth import get_password_hash
-        from models import Role
-        
-        result = await db.execute(select(Role).where(Role.name == ROLE_ADMIN))
-        admin_role = result.scalar_one_or_none()
-        
-        godfather = User(
-            email=godfather_email,
-            hashed_password=get_password_hash("password123"),
-            roles=[admin_role] if admin_role else [],
-        )
-        db.add(godfather)
-        await db.flush()
+        raise ValueError(f"Godfather user with ID {godfather_id} not found")
     
     # Create invite
     identifier = generate_invite_identifier()
     invite = Invite(
         identifier=identifier,
-        godfather_id=godfather.id,
+        godfather_id=godfather_id,
         status=InviteStatus.READY,
     )
     db.add(invite)
@@ -49,3 +45,29 @@ async def create_invite_for_registration(db: AsyncSession, godfather_email: str)
     
     return identifier
 
+
+# Backwards-compatible alias that gets a user by email
+async def create_invite_for_registration(db: AsyncSession, godfather_email: str) -> str:
+    """
+    Create an invite for an existing godfather user (looked up by email).
+    
+    The godfather must already exist in the database.
+    
+    Args:
+        db: Database session
+        godfather_email: Email of the existing user who will be the godfather
+        
+    Returns:
+        The invite identifier.
+        
+    Raises:
+        ValueError: If the godfather user doesn't exist.
+    """
+    result = await db.execute(select(User).where(User.email == godfather_email))
+    godfather = result.scalar_one_or_none()
+    
+    if not godfather:
+        raise ValueError(f"Godfather user with email '{godfather_email}' not found. "
+                        "Create the user first using create_user_with_roles().")
+    
+    return await create_invite_for_godfather(db, godfather.id)
diff --git a/backend/tests/test_auth.py b/backend/tests/test_auth.py
index e5576be..026ca66 100644
--- a/backend/tests/test_auth.py
+++ b/backend/tests/test_auth.py
@@ -6,7 +6,9 @@ users will create invites first via the helper function.
 import pytest
 
 from auth import COOKIE_NAME
-from tests.helpers import unique_email, create_invite_for_registration
+from models import ROLE_REGULAR
+from tests.helpers import unique_email, create_invite_for_godfather
+from tests.conftest import create_user_with_roles
 
 
 # Registration tests (with invite)
@@ -15,9 +17,10 @@ async def test_register_success(client_factory):
     """Can register with valid invite code."""
     email = unique_email("register")
     
-    # Create invite
+    # Create godfather user and invite
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("godfather"))
+        godfather = await create_user_with_roles(db, unique_email("godfather"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     response = await client_factory.post(
         "/api/auth/register",
@@ -44,10 +47,11 @@ async def test_register_duplicate_email(client_factory):
     """Cannot register with already-used email."""
     email = unique_email("duplicate")
     
-    # Create two invites
+    # Create godfather and two invites
     async with client_factory.get_db_session() as db:
-        invite1 = await create_invite_for_registration(db, unique_email("gf1"))
-        invite2 = await create_invite_for_registration(db, unique_email("gf2"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite1 = await create_invite_for_godfather(db, godfather.id)
+        invite2 = await create_invite_for_godfather(db, godfather.id)
     
     # First registration
     await client_factory.post(
@@ -76,7 +80,8 @@ async def test_register_duplicate_email(client_factory):
 async def test_register_invalid_email(client_factory):
     """Cannot register with invalid email format."""
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     response = await client_factory.post(
         "/api/auth/register",
@@ -133,7 +138,8 @@ async def test_login_success(client_factory):
     email = unique_email("login")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     await client_factory.post(
         "/api/auth/register",
@@ -161,7 +167,8 @@ async def test_login_wrong_password(client_factory):
     email = unique_email("wrongpass")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     await client_factory.post(
         "/api/auth/register",
@@ -214,7 +221,8 @@ async def test_get_me_success(client_factory):
     email = unique_email("me")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg_response = await client_factory.post(
         "/api/auth/register",
@@ -269,7 +277,8 @@ async def test_cookie_from_register_works_for_me(client_factory):
     email = unique_email("tokentest")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg_response = await client_factory.post(
         "/api/auth/register",
@@ -294,7 +303,8 @@ async def test_cookie_from_login_works_for_me(client_factory):
     email = unique_email("logintoken")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     await client_factory.post(
         "/api/auth/register",
@@ -325,8 +335,9 @@ async def test_multiple_users_isolated(client_factory):
     email2 = unique_email("user2")
     
     async with client_factory.get_db_session() as db:
-        invite1 = await create_invite_for_registration(db, unique_email("gf1"))
-        invite2 = await create_invite_for_registration(db, unique_email("gf2"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite1 = await create_invite_for_godfather(db, godfather.id)
+        invite2 = await create_invite_for_godfather(db, godfather.id)
     
     resp1 = await client_factory.post(
         "/api/auth/register",
@@ -366,7 +377,8 @@ async def test_password_is_hashed(client_factory):
     email = unique_email("hashtest")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     await client_factory.post(
         "/api/auth/register",
@@ -389,7 +401,8 @@ async def test_case_sensitive_password(client_factory):
     email = unique_email("casetest")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     await client_factory.post(
         "/api/auth/register",
@@ -413,7 +426,8 @@ async def test_logout_success(client_factory):
     email = unique_email("logout")
     
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg_response = await client_factory.post(
         "/api/auth/register",
diff --git a/backend/tests/test_counter.py b/backend/tests/test_counter.py
index b9c4cba..2bbc55e 100644
--- a/backend/tests/test_counter.py
+++ b/backend/tests/test_counter.py
@@ -5,7 +5,9 @@ Note: Registration now requires an invite code.
 import pytest
 
 from auth import COOKIE_NAME
-from tests.helpers import unique_email, create_invite_for_registration
+from models import ROLE_REGULAR
+from tests.helpers import unique_email, create_invite_for_godfather
+from tests.conftest import create_user_with_roles
 
 
 # Protected endpoint tests - without auth
@@ -39,7 +41,8 @@ async def test_increment_counter_invalid_cookie(client_factory):
 @pytest.mark.asyncio
 async def test_get_counter_authenticated(client_factory):
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg = await client_factory.post(
         "/api/auth/register",
@@ -61,7 +64,8 @@ async def test_get_counter_authenticated(client_factory):
 @pytest.mark.asyncio
 async def test_increment_counter(client_factory):
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg = await client_factory.post(
         "/api/auth/register",
@@ -87,7 +91,8 @@ async def test_increment_counter(client_factory):
 @pytest.mark.asyncio
 async def test_increment_counter_multiple(client_factory):
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg = await client_factory.post(
         "/api/auth/register",
@@ -115,7 +120,8 @@ async def test_increment_counter_multiple(client_factory):
 @pytest.mark.asyncio
 async def test_get_counter_after_increment(client_factory):
     async with client_factory.get_db_session() as db:
-        invite_code = await create_invite_for_registration(db, unique_email("gf"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite_code = await create_invite_for_godfather(db, godfather.id)
     
     reg = await client_factory.post(
         "/api/auth/register",
@@ -141,10 +147,11 @@ async def test_get_counter_after_increment(client_factory):
 # Counter is shared between users
 @pytest.mark.asyncio
 async def test_counter_shared_between_users(client_factory):
-    # Create invites for two users
+    # Create godfather and invites for two users
     async with client_factory.get_db_session() as db:
-        invite1 = await create_invite_for_registration(db, unique_email("gf1"))
-        invite2 = await create_invite_for_registration(db, unique_email("gf2"))
+        godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+        invite1 = await create_invite_for_godfather(db, godfather.id)
+        invite2 = await create_invite_for_godfather(db, godfather.id)
     
     # Create first user
     reg1 = await client_factory.post(
diff --git a/backend/tests/test_invites.py b/backend/tests/test_invites.py
index 8a07a37..ad05850 100644
--- a/backend/tests/test_invites.py
+++ b/backend/tests/test_invites.py
@@ -397,6 +397,47 @@ async def test_created_invite_persisted_in_db(client_factory, admin_user, regula
             assert invite.status == InviteStatus.READY
 
 
+@pytest.mark.asyncio
+async def test_create_invite_retries_on_collision(client_factory, admin_user, regular_user):
+    """Create invite retries with new identifier on collision."""
+    from unittest.mock import patch
+    
+    async with client_factory.create(cookies=admin_user["cookies"]) as client:
+        async with client_factory.get_db_session() as db:
+            result = await db.execute(
+                select(User).where(User.email == regular_user["email"])
+            )
+            godfather = result.scalar_one()
+        
+        # Create first invite normally
+        response1 = await client.post(
+            "/api/admin/invites",
+            json={"godfather_id": godfather.id},
+        )
+        assert response1.status_code == 200
+        identifier1 = response1.json()["identifier"]
+        
+        # Mock generator to first return the same identifier (collision), then a new one
+        call_count = 0
+        def mock_generator():
+            nonlocal call_count
+            call_count += 1
+            if call_count == 1:
+                return identifier1  # Will collide
+            return f"unique-word-{call_count:02d}"  # Won't collide
+        
+        with patch("main.generate_invite_identifier", side_effect=mock_generator):
+            response2 = await client.post(
+                "/api/admin/invites",
+                json={"godfather_id": godfather.id},
+            )
+            
+            assert response2.status_code == 200
+            # Should have retried and gotten a new identifier
+            assert response2.json()["identifier"] != identifier1
+            assert call_count >= 2  # At least one retry
+
+
 # ============================================================================
 # Invite Check API Tests (Phase 3)
 # ============================================================================
@@ -441,6 +482,32 @@ async def test_check_invite_not_found(client_factory):
         assert "not found" in data["error"].lower()
 
 
+@pytest.mark.asyncio
+async def test_check_invite_invalid_format(client_factory):
+    """Check endpoint returns error for invalid format without querying DB."""
+    async with client_factory.create() as client:
+        # Missing number part
+        response = await client.get("/api/invites/word-word/check")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["valid"] is False
+        assert "format" in data["error"].lower()
+        
+        # Single digit number
+        response = await client.get("/api/invites/word-word-1/check")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["valid"] is False
+        assert "format" in data["error"].lower()
+        
+        # Too many parts
+        response = await client.get("/api/invites/word-word-word-00/check")
+        assert response.status_code == 200
+        data = response.json()
+        assert data["valid"] is False
+        assert "format" in data["error"].lower()
+
+
 @pytest.mark.asyncio
 async def test_check_invite_case_insensitive(client_factory, admin_user, regular_user):
     """Check endpoint handles case-insensitive identifiers."""
diff --git a/backend/tests/test_permissions.py b/backend/tests/test_permissions.py
index 4981d5f..efcfa67 100644
--- a/backend/tests/test_permissions.py
+++ b/backend/tests/test_permissions.py
@@ -305,10 +305,13 @@ class TestSecurityBypassAttempts:
         Test that new registrations cannot claim admin role.
         New users should only get 'regular' role by default.
         """
-        from tests.helpers import unique_email, create_invite_for_registration
+        from tests.helpers import unique_email, create_invite_for_godfather
+        from tests.conftest import create_user_with_roles
+        from models import ROLE_REGULAR
         
         async with client_factory.get_db_session() as db:
-            invite_code = await create_invite_for_registration(db, unique_email("gf"))
+            godfather = await create_user_with_roles(db, unique_email("gf"), "pass123", [ROLE_REGULAR])
+            invite_code = await create_invite_for_godfather(db, godfather.id)
         
         response = await client_factory.post(
             "/api/auth/register",
diff --git a/frontend/app/admin/invites/page.tsx b/frontend/app/admin/invites/page.tsx
index bce5613..d60b219 100644
--- a/frontend/app/admin/invites/page.tsx
+++ b/frontend/app/admin/invites/page.tsx
@@ -43,7 +43,7 @@ export default function AdminInvitesPage() {
   const [createError, setCreateError] = useState<string | null>(null);
   const [users, setUsers] = useState<UserOption[]>([]);
   const { user, isLoading, isAuthorized } = useRequireAuth({
-    requiredPermission: Permission.VIEW_AUDIT, // Admins have this
+    requiredPermission: Permission.MANAGE_INVITES,
     fallbackRedirect: "/",
   });
 
diff --git a/frontend/app/components/Header.tsx b/frontend/app/components/Header.tsx
index e0eabfc..927a60a 100644
--- a/frontend/app/components/Header.tsx
+++ b/frontend/app/components/Header.tsx
@@ -43,37 +43,11 @@ export function Header({ currentPage }: HeaderProps) {
 
   if (!user) return null;
 
-  // For admin pages, show admin navigation
-  if (isAdminUser && (currentPage === "audit" || currentPage === "admin-invites")) {
-    return (
-      <div style={sharedStyles.header}>
-        <div style={sharedStyles.nav}>
-          {ADMIN_NAV_ITEMS.map((item, index) => (
-            <span key={item.id}>
-              {index > 0 && <span style={sharedStyles.navDivider}>•</span>}
-              {item.id === currentPage ? (
-                <span style={sharedStyles.navCurrent}>{item.label}</span>
-              ) : (
-                <a href={item.href} style={sharedStyles.navLink}>
-                  {item.label}
-                </a>
-              )}
-            </span>
-          ))}
-        </div>
-        <div style={sharedStyles.userInfo}>
-          <span style={sharedStyles.userEmail}>{user.email}</span>
-          <button onClick={handleLogout} style={sharedStyles.logoutBtn}>
-            Sign out
-          </button>
-        </div>
-      </div>
-    );
-  }
-
-  // For regular pages, build nav with links
-  const visibleItems = REGULAR_NAV_ITEMS.filter(
-    (item) => !item.regularOnly || isRegularUser
+  // Build nav items based on user role
+  // Admin users see admin nav items, regular users see regular nav items
+  const navItems = isAdminUser ? ADMIN_NAV_ITEMS : REGULAR_NAV_ITEMS;
+  const visibleItems = navItems.filter(
+    (item) => (!item.regularOnly || isRegularUser) && (!item.adminOnly || isAdminUser)
   );
 
   return (
diff --git a/frontend/app/page.test.tsx b/frontend/app/page.test.tsx
index 1c8d106..5990ca2 100644
--- a/frontend/app/page.test.tsx
+++ b/frontend/app/page.test.tsx
@@ -258,9 +258,9 @@ describe("Home - Navigation", () => {
 
     render(<Home />);
     
-    // Wait for render, then check profile link is not present
+    // Wait for render - admin sees admin nav (Audit, Invites) not regular nav
     await waitFor(() => {
-      expect(screen.getByText("Counter")).toBeDefined();
+      expect(screen.getByText("Audit")).toBeDefined();
     });
     expect(screen.queryByText("My Profile")).toBeNull();
   });
diff --git a/frontend/app/signup/[code]/page.tsx b/frontend/app/signup/[code]/page.tsx
index 6b3bd6e..6cc8ae3 100644
--- a/frontend/app/signup/[code]/page.tsx
+++ b/frontend/app/signup/[code]/page.tsx
@@ -7,10 +7,13 @@ import { useAuth } from "../../auth-context";
 export default function SignupWithCodePage() {
   const params = useParams();
   const router = useRouter();
-  const { user } = useAuth();
+  const { user, isLoading } = useAuth();
   const code = params.code as string;
 
   useEffect(() => {
+    // Wait for auth check to complete before redirecting
+    if (isLoading) return;
+    
     if (user) {
       // Already logged in, redirect to home
       router.replace("/");
@@ -18,7 +21,7 @@ export default function SignupWithCodePage() {
       // Redirect to signup with code as query param
       router.replace(`/signup?code=${encodeURIComponent(code)}`);
     }
-  }, [user, code, router]);
+  }, [user, isLoading, code, router]);
 
   return (
     <main style={{ 
diff --git a/frontend/app/signup/page.test.tsx b/frontend/app/signup/page.test.tsx
index 3be6767..b25d956 100644
--- a/frontend/app/signup/page.test.tsx
+++ b/frontend/app/signup/page.test.tsx
@@ -5,10 +5,11 @@ import SignupPage from "./page";
 const mockPush = vi.fn();
 vi.mock("next/navigation", () => ({
   useRouter: () => ({ push: mockPush }),
+  useSearchParams: () => ({ get: () => null }),
 }));
 
 vi.mock("../auth-context", () => ({
-  useAuth: () => ({ register: vi.fn() }),
+  useAuth: () => ({ user: null, register: vi.fn() }),
 }));
 
 beforeEach(() => vi.clearAllMocks());
@@ -16,19 +17,18 @@ afterEach(() => cleanup());
 
 test("renders signup form with title", () => {
   render(<SignupPage />);
-  expect(screen.getByRole("heading", { name: "Create account" })).toBeDefined();
+  // Step 1 shows "Join with Invite" title (invite code entry)
+  expect(screen.getByRole("heading", { name: "Join with Invite" })).toBeDefined();
 });
 
-test("renders email and password inputs", () => {
+test("renders invite code input", () => {
   render(<SignupPage />);
-  expect(screen.getByLabelText("Email")).toBeDefined();
-  expect(screen.getByLabelText("Password")).toBeDefined();
-  expect(screen.getByLabelText("Confirm Password")).toBeDefined();
+  expect(screen.getByLabelText("Invite Code")).toBeDefined();
 });
 
-test("renders create account button", () => {
+test("renders continue button", () => {
   render(<SignupPage />);
-  expect(screen.getByRole("button", { name: "Create account" })).toBeDefined();
+  expect(screen.getByRole("button", { name: "Continue" })).toBeDefined();
 });
 
 test("renders link to login", () => {
diff --git a/frontend/app/signup/page.tsx b/frontend/app/signup/page.tsx
index 982f54d..4398979 100644
--- a/frontend/app/signup/page.tsx
+++ b/frontend/app/signup/page.tsx
@@ -1,6 +1,6 @@
 "use client";
 
-import { useState, useEffect, Suspense } from "react";
+import { useState, useEffect, useCallback, Suspense } from "react";
 import { useRouter, useSearchParams } from "next/navigation";
 import { useAuth } from "../auth-context";
 import { api } from "../api";
@@ -20,6 +20,7 @@ function SignupContent() {
   const [inviteValid, setInviteValid] = useState<boolean | null>(null);
   const [inviteError, setInviteError] = useState("");
   const [isCheckingInvite, setIsCheckingInvite] = useState(false);
+  const [isCheckingInitialCode, setIsCheckingInitialCode] = useState(!!initialCode);
   
   const [email, setEmail] = useState("");
   const [password, setPassword] = useState("");
@@ -37,14 +38,7 @@ function SignupContent() {
     }
   }, [user, router]);
 
-  // Check invite code on mount if provided in URL
-  useEffect(() => {
-    if (initialCode) {
-      checkInvite(initialCode);
-    }
-  }, [initialCode]);
-
-  const checkInvite = async (code: string) => {
+  const checkInvite = useCallback(async (code: string) => {
     if (!code.trim()) {
       setInviteValid(null);
       setInviteError("");
@@ -72,7 +66,14 @@ function SignupContent() {
     } finally {
       setIsCheckingInvite(false);
     }
-  };
+  }, []);
+
+  // Check invite code on mount if provided in URL
+  useEffect(() => {
+    if (initialCode) {
+      checkInvite(initialCode).finally(() => setIsCheckingInitialCode(false));
+    }
+  }, [initialCode, checkInvite]);
 
   const handleInviteSubmit = (e: React.FormEvent) => {
     e.preventDefault();
@@ -110,6 +111,21 @@ function SignupContent() {
     return null;
   }
 
+  // Show loading state while checking initial code from URL
+  if (isCheckingInitialCode) {
+    return (
+      <main style={styles.main}>
+        <div style={styles.container}>
+          <div style={styles.card}>
+            <div style={{ textAlign: "center", color: "rgba(255,255,255,0.6)" }}>
+              Checking invite code...
+            </div>
+          </div>
+        </div>
+      </main>
+    );
+  }
+
   // Step 1: Enter invite code
   if (!inviteValid) {
     return (
diff --git a/frontend/e2e/auth.spec.ts b/frontend/e2e/auth.spec.ts
index 57cebdb..c42f106 100644
--- a/frontend/e2e/auth.spec.ts
+++ b/frontend/e2e/auth.spec.ts
@@ -79,6 +79,53 @@ test.describe("Authentication Flow", () => {
   });
 });
 
+test.describe("Logged-in User Visiting Invite URL", () => {
+  test("redirects to home when logged-in user visits direct invite URL", async ({ page, request }) => {
+    const email = uniqueEmail();
+    const inviteCode = await createInvite(request);
+
+    // First sign up to create a user
+    await page.goto("/signup");
+    await page.fill('input#inviteCode', inviteCode);
+    await page.click('button[type="submit"]');
+    await expect(page.locator("h1")).toHaveText("Create account");
+    
+    await page.fill('input#email', email);
+    await page.fill('input#password', "password123");
+    await page.fill('input#confirmPassword', "password123");
+    await page.click('button[type="submit"]');
+    await expect(page).toHaveURL("/");
+
+    // Create another invite
+    const anotherInvite = await createInvite(request);
+
+    // Visit invite URL while logged in - should redirect to home
+    await page.goto(`/signup/${anotherInvite}`);
+    await expect(page).toHaveURL("/");
+  });
+
+  test("redirects to home when logged-in user visits signup page", async ({ page, request }) => {
+    const email = uniqueEmail();
+    const inviteCode = await createInvite(request);
+
+    // Sign up and stay logged in
+    await page.goto("/signup");
+    await page.fill('input#inviteCode', inviteCode);
+    await page.click('button[type="submit"]');
+    await expect(page.locator("h1")).toHaveText("Create account");
+    
+    await page.fill('input#email', email);
+    await page.fill('input#password', "password123");
+    await page.fill('input#confirmPassword', "password123");
+    await page.click('button[type="submit"]');
+    await expect(page).toHaveURL("/");
+
+    // Try to visit signup page while logged in - should redirect to home
+    await page.goto("/signup");
+    await expect(page).toHaveURL("/");
+  });
+});
+
 test.describe("Signup with Invite", () => {
   test.beforeEach(async ({ page }) => {
     await clearAuth(page);
diff --git a/scripts/e2e.sh b/scripts/e2e.sh
index 9dad206..afbe160 100755
--- a/scripts/e2e.sh
+++ b/scripts/e2e.sh
@@ -14,12 +14,6 @@ fi
 pkill -f "uvicorn main:app" 2>/dev/null || true
 sleep 1
 
-# Start db
-docker compose up -d db
-
-# Wait for db to be ready
-sleep 2
-
 # Seed the database with roles and test users
 cd backend
 echo "Seeding database..."