diff --git a/backend/auth.py b/backend/auth.py
index 9e464c3..ed05a6d 100644
--- a/backend/auth.py
+++ b/backend/auth.py
@@ -6,10 +6,10 @@ import uuid
 from datetime import datetime, timedelta, timezone
 from typing import Annotated
 
+import bcrypt
 import jwt
 from fastapi import Depends, HTTPException, status
 from fastapi.security import OAuth2PasswordBearer
-from passlib.context import CryptContext
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -19,17 +19,15 @@ from models import User, UserRole
 
 # ── Password hashing ─────────────────────────────────────────────────────────
 
-_pwd_ctx = CryptContext(schemes=["bcrypt"], deprecated="auto")
-
 
 def hash_password(plain: str) -> str:
     """Hash a plaintext password with bcrypt."""
-    return _pwd_ctx.hash(plain)
+    return bcrypt.hashpw(plain.encode("utf-8"), bcrypt.gensalt()).decode("utf-8")
 
 
 def verify_password(plain: str, hashed: str) -> bool:
     """Verify a plaintext password against a bcrypt hash."""
-    return _pwd_ctx.verify(plain, hashed)
+    return bcrypt.checkpw(plain.encode("utf-8"), hashed.encode("utf-8"))
 
 
 # ── JWT ──────────────────────────────────────────────────────────────────────
diff --git a/backend/main.py b/backend/main.py
index c1202d8..68bde81 100644
--- a/backend/main.py
+++ b/backend/main.py
@@ -12,7 +12,7 @@ from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
 from config import get_settings
-from routers import creators, health, ingest, pipeline, reports, search, stats, techniques, topics, videos
+from routers import auth, creators, health, ingest, pipeline, reports, search, stats, techniques, topics, videos
 
 
 def _setup_logging() -> None:
@@ -78,6 +78,7 @@ app.add_middleware(
 app.include_router(health.router)
 
 # Versioned API
+app.include_router(auth.router, prefix="/api/v1")
 app.include_router(creators.router, prefix="/api/v1")
 app.include_router(ingest.router, prefix="/api/v1")
 app.include_router(pipeline.router, prefix="/api/v1")
diff --git a/backend/requirements.txt b/backend/requirements.txt
index 58085b0..a2547d0 100644
--- a/backend/requirements.txt
+++ b/backend/requirements.txt
@@ -16,7 +16,7 @@ pyyaml>=6.0,<7.0
 psycopg2-binary>=2.9,<3.0
 watchdog>=4.0,<5.0
 PyJWT>=2.8,<3.0
-passlib[bcrypt]>=1.7,<2.0
+bcrypt>=4.0,<6.0
 # Test dependencies
 pytest>=8.0,<10.0
 pytest-asyncio>=0.24,<1.0
diff --git a/backend/routers/auth.py b/backend/routers/auth.py
new file mode 100644
index 0000000..79b1219
--- /dev/null
+++ b/backend/routers/auth.py
@@ -0,0 +1,168 @@
+"""Auth router — registration, login, profile management."""
+
+from __future__ import annotations
+
+import logging
+from datetime import datetime, timezone
+from typing import Annotated
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from sqlalchemy import select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from auth import (
+    create_access_token,
+    get_current_user,
+    hash_password,
+    verify_password,
+)
+from database import get_session
+from models import Creator, InviteCode, User
+from schemas import (
+    LoginRequest,
+    RegisterRequest,
+    TokenResponse,
+    UpdateProfileRequest,
+    UserResponse,
+)
+
+logger = logging.getLogger("chrysopedia.auth")
+
+router = APIRouter(prefix="/auth", tags=["auth"])
+
+
+# ── Registration ─────────────────────────────────────────────────────────────
+
+
+@router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
+async def register(
+    body: RegisterRequest,
+    session: Annotated[AsyncSession, Depends(get_session)],
+):
+    """Register a new user with a valid invite code."""
+    # 1. Validate invite code
+    result = await session.execute(
+        select(InviteCode).where(InviteCode.code == body.invite_code)
+    )
+    invite = result.scalar_one_or_none()
+    if invite is None:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Invalid invite code")
+
+    now = datetime.now(timezone.utc).replace(tzinfo=None)
+    if invite.expires_at is not None and invite.expires_at < now:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Invite code has expired")
+
+    if invite.uses_remaining <= 0:
+        raise HTTPException(status_code=status.HTTP_403_FORBIDDEN, detail="Invite code exhausted")
+
+    # 2. Check email uniqueness
+    existing = await session.execute(select(User).where(User.email == body.email))
+    if existing.scalar_one_or_none() is not None:
+        raise HTTPException(status_code=status.HTTP_409_CONFLICT, detail="Email already registered")
+
+    # 3. Optionally resolve creator_id from slug
+    creator_id = None
+    if body.creator_slug:
+        creator_result = await session.execute(
+            select(Creator).where(Creator.slug == body.creator_slug)
+        )
+        creator = creator_result.scalar_one_or_none()
+        if creator is not None:
+            creator_id = creator.id
+
+    # 4. Create user
+    user = User(
+        email=body.email,
+        hashed_password=hash_password(body.password),
+        display_name=body.display_name,
+        creator_id=creator_id,
+    )
+    session.add(user)
+
+    # 5. Decrement invite code uses
+    invite.uses_remaining -= 1
+
+    await session.commit()
+    await session.refresh(user)
+
+    logger.info("User registered: %s (email=%s)", user.id, user.email)
+    return user
+
+
+# ── Login ────────────────────────────────────────────────────────────────────
+
+
+@router.post("/login", response_model=TokenResponse)
+async def login(
+    body: LoginRequest,
+    session: Annotated[AsyncSession, Depends(get_session)],
+):
+    """Authenticate with email + password, return JWT."""
+    result = await session.execute(select(User).where(User.email == body.email))
+    user = result.scalar_one_or_none()
+
+    if user is None or not verify_password(body.password, user.hashed_password):
+        raise HTTPException(
+            status_code=status.HTTP_401_UNAUTHORIZED,
+            detail="Invalid email or password",
+        )
+
+    token = create_access_token(user.id, user.role.value)
+    logger.info("User logged in: %s", user.id)
+    return TokenResponse(access_token=token)
+
+
+# ── Profile ──────────────────────────────────────────────────────────────────
+
+
+@router.get("/me", response_model=UserResponse)
+async def get_profile(
+    current_user: Annotated[User, Depends(get_current_user)],
+):
+    """Return the current user's profile."""
+    return current_user
+
+
+@router.put("/me", response_model=UserResponse)
+async def update_profile(
+    body: UpdateProfileRequest,
+    current_user: Annotated[User, Depends(get_current_user)],
+    session: Annotated[AsyncSession, Depends(get_session)],
+):
+    """Update the current user's display name and/or password."""
+    if body.display_name is not None:
+        current_user.display_name = body.display_name
+
+    if body.new_password is not None:
+        if body.current_password is None:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Current password required to set new password",
+            )
+        if not verify_password(body.current_password, current_user.hashed_password):
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Current password is incorrect",
+            )
+        current_user.hashed_password = hash_password(body.new_password)
+
+    await session.commit()
+    await session.refresh(current_user)
+
+    logger.info("Profile updated: %s", current_user.id)
+    return current_user
+
+
+# ── Seed ─────────────────────────────────────────────────────────────────────
+
+
+async def seed_invite_codes(session: AsyncSession) -> None:
+    """Create default invite code if none exist. Call from lifespan or CLI."""
+    result = await session.execute(select(InviteCode))
+    if result.scalar_one_or_none() is None:
+        session.add(InviteCode(
+            code="CHRYSOPEDIA-ALPHA-2026",
+            uses_remaining=100,
+        ))
+        await session.commit()
+        logger.info("Seeded default invite code: CHRYSOPEDIA-ALPHA-2026")
diff --git a/backend/tests/conftest.py b/backend/tests/conftest.py
index 9de778f..86aa3c1 100644
--- a/backend/tests/conftest.py
+++ b/backend/tests/conftest.py
@@ -34,9 +34,12 @@ from main import app  # noqa: E402
 from models import (  # noqa: E402
     ContentType,
     Creator,
+    InviteCode,
     ProcessingStatus,
     SourceVideo,
     TranscriptSegment,
+    User,
+    UserRole,
 )
 
 TEST_DATABASE_URL = os.getenv(
@@ -190,3 +193,47 @@ def pre_ingested_video(sync_engine):
         session.close()
 
     return result
+
+
+# ── Auth fixtures ────────────────────────────────────────────────────────────
+
+_TEST_INVITE_CODE = "TEST-INVITE-2026"
+_TEST_EMAIL = "testuser@chrysopedia.com"
+_TEST_PASSWORD = "securepass123"
+
+
+@pytest_asyncio.fixture()
+async def invite_code(db_engine):
+    """Create a test invite code in the DB and return the code string."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        code = InviteCode(code=_TEST_INVITE_CODE, uses_remaining=10)
+        session.add(code)
+        await session.commit()
+    return _TEST_INVITE_CODE
+
+
+@pytest_asyncio.fixture()
+async def registered_user(client, invite_code):
+    """Register a user via the API and return the response dict."""
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": _TEST_EMAIL,
+        "password": _TEST_PASSWORD,
+        "display_name": "Test User",
+        "invite_code": invite_code,
+    })
+    assert resp.status_code == 201
+    return resp.json()
+
+
+@pytest_asyncio.fixture()
+async def auth_headers(client, registered_user):
+    """Log in and return Authorization headers dict."""
+    resp = await client.post("/api/v1/auth/login", json={
+        "email": _TEST_EMAIL,
+        "password": _TEST_PASSWORD,
+    })
+    assert resp.status_code == 200
+    token = resp.json()["access_token"]
+    return {"Authorization": f"Bearer {token}"}
+
diff --git a/backend/tests/test_auth.py b/backend/tests/test_auth.py
new file mode 100644
index 0000000..c48a8c4
--- /dev/null
+++ b/backend/tests/test_auth.py
@@ -0,0 +1,314 @@
+"""Integration tests for the auth router — registration, login, profile."""
+
+import uuid
+from datetime import datetime, timedelta, timezone
+
+import pytest
+import pytest_asyncio
+from sqlalchemy.ext.asyncio import AsyncSession, async_sessionmaker
+
+from models import InviteCode, User
+
+
+# ── Registration ─────────────────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_register_valid(client, invite_code):
+    """Register with a valid invite code → 201 + user created."""
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "newuser@example.com",
+        "password": "strongpass1",
+        "display_name": "New User",
+        "invite_code": invite_code,
+    })
+    assert resp.status_code == 201
+    data = resp.json()
+    assert data["email"] == "newuser@example.com"
+    assert data["display_name"] == "New User"
+    assert data["role"] == "creator"
+    assert "id" in data
+    # Password not leaked
+    assert "hashed_password" not in data
+
+
+@pytest.mark.asyncio
+async def test_register_invalid_invite_code(client, invite_code):
+    """Register with a wrong invite code → 403."""
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "bad@example.com",
+        "password": "strongpass1",
+        "display_name": "Bad",
+        "invite_code": "WRONG-CODE",
+    })
+    assert resp.status_code == 403
+    assert "Invalid invite code" in resp.json()["detail"]
+
+
+@pytest.mark.asyncio
+async def test_register_expired_invite_code(client, db_engine):
+    """Register with an expired invite code → 403."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        past = (datetime.now(timezone.utc) - timedelta(days=1)).replace(tzinfo=None)
+        session.add(InviteCode(code="EXPIRED-CODE", uses_remaining=10, expires_at=past))
+        await session.commit()
+
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "exp@example.com",
+        "password": "strongpass1",
+        "display_name": "Expired",
+        "invite_code": "EXPIRED-CODE",
+    })
+    assert resp.status_code == 403
+    assert "expired" in resp.json()["detail"].lower()
+
+
+@pytest.mark.asyncio
+async def test_register_exhausted_invite_code(client, db_engine):
+    """Register with an invite code that has uses_remaining=0 → 403."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        session.add(InviteCode(code="EXHAUSTED", uses_remaining=0))
+        await session.commit()
+
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "nope@example.com",
+        "password": "strongpass1",
+        "display_name": "Nope",
+        "invite_code": "EXHAUSTED",
+    })
+    assert resp.status_code == 403
+    assert "exhausted" in resp.json()["detail"].lower()
+
+
+@pytest.mark.asyncio
+async def test_register_invite_code_decrements(client, db_engine):
+    """Invite code uses_remaining decrements after registration."""
+    factory = async_sessionmaker(db_engine, class_=AsyncSession, expire_on_commit=False)
+    async with factory() as session:
+        session.add(InviteCode(code="SINGLE-USE", uses_remaining=1))
+        await session.commit()
+
+    # First registration succeeds
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "first@example.com",
+        "password": "strongpass1",
+        "display_name": "First",
+        "invite_code": "SINGLE-USE",
+    })
+    assert resp.status_code == 201
+
+    # Second registration with same code fails (exhausted)
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "second@example.com",
+        "password": "strongpass1",
+        "display_name": "Second",
+        "invite_code": "SINGLE-USE",
+    })
+    assert resp.status_code == 403
+
+
+@pytest.mark.asyncio
+async def test_register_duplicate_email(client, invite_code, registered_user):
+    """Register with an already-used email → 409."""
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "testuser@chrysopedia.com",
+        "password": "anotherpass1",
+        "display_name": "Dup",
+        "invite_code": invite_code,
+    })
+    assert resp.status_code == 409
+    assert "already registered" in resp.json()["detail"].lower()
+
+
+# ── Login ────────────────────────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_login_success(client, registered_user):
+    """Login with correct credentials → 200 + JWT."""
+    resp = await client.post("/api/v1/auth/login", json={
+        "email": "testuser@chrysopedia.com",
+        "password": "securepass123",
+    })
+    assert resp.status_code == 200
+    data = resp.json()
+    assert "access_token" in data
+    assert data["token_type"] == "bearer"
+
+
+@pytest.mark.asyncio
+async def test_login_wrong_password(client, registered_user):
+    """Login with wrong password → 401."""
+    resp = await client.post("/api/v1/auth/login", json={
+        "email": "testuser@chrysopedia.com",
+        "password": "wrongpassword",
+    })
+    assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+async def test_login_nonexistent_email(client):
+    """Login with an email that doesn't exist → 401."""
+    resp = await client.post("/api/v1/auth/login", json={
+        "email": "nobody@example.com",
+        "password": "somepass123",
+    })
+    assert resp.status_code == 401
+
+
+# ── Profile (GET /me) ───────────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_get_me_authenticated(client, auth_headers):
+    """GET /me with valid token → 200 + profile."""
+    resp = await client.get("/api/v1/auth/me", headers=auth_headers)
+    assert resp.status_code == 200
+    data = resp.json()
+    assert data["email"] == "testuser@chrysopedia.com"
+    assert data["display_name"] == "Test User"
+
+
+@pytest.mark.asyncio
+async def test_get_me_no_token(client, db_engine):
+    """GET /me without token → 401."""
+    resp = await client.get("/api/v1/auth/me")
+    assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+async def test_get_me_invalid_token(client, db_engine):
+    """GET /me with garbage token → 401."""
+    resp = await client.get("/api/v1/auth/me", headers={
+        "Authorization": "Bearer invalid.garbage.token",
+    })
+    assert resp.status_code == 401
+
+
+@pytest.mark.asyncio
+async def test_get_me_expired_token(client, db_engine, invite_code):
+    """GET /me with an expired JWT → 401."""
+    from auth import create_access_token
+
+    # Register a user first
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "expired@example.com",
+        "password": "strongpass1",
+        "display_name": "Expired Token User",
+        "invite_code": invite_code,
+    })
+    assert resp.status_code == 201
+    user_id = resp.json()["id"]
+
+    # Create a token that expires immediately
+    token = create_access_token(user_id, "creator", expires_minutes=-1)
+    resp = await client.get("/api/v1/auth/me", headers={
+        "Authorization": f"Bearer {token}",
+    })
+    assert resp.status_code == 401
+
+
+# ── Profile (PUT /me) ───────────────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_update_display_name(client, auth_headers):
+    """PUT /me updates display_name → 200 + new name."""
+    resp = await client.put("/api/v1/auth/me", json={
+        "display_name": "Updated Name",
+    }, headers=auth_headers)
+    assert resp.status_code == 200
+    assert resp.json()["display_name"] == "Updated Name"
+
+    # Verify persistence
+    resp2 = await client.get("/api/v1/auth/me", headers=auth_headers)
+    assert resp2.json()["display_name"] == "Updated Name"
+
+
+@pytest.mark.asyncio
+async def test_update_password(client, invite_code):
+    """PUT /me changes password → can login with new password."""
+    # Register
+    await client.post("/api/v1/auth/register", json={
+        "email": "pwchange@example.com",
+        "password": "oldpassword1",
+        "display_name": "PW User",
+        "invite_code": invite_code,
+    })
+    # Login
+    login_resp = await client.post("/api/v1/auth/login", json={
+        "email": "pwchange@example.com",
+        "password": "oldpassword1",
+    })
+    token = login_resp.json()["access_token"]
+    headers = {"Authorization": f"Bearer {token}"}
+
+    # Change password
+    resp = await client.put("/api/v1/auth/me", json={
+        "current_password": "oldpassword1",
+        "new_password": "newpassword1",
+    }, headers=headers)
+    assert resp.status_code == 200
+
+    # Old password fails
+    resp_old = await client.post("/api/v1/auth/login", json={
+        "email": "pwchange@example.com",
+        "password": "oldpassword1",
+    })
+    assert resp_old.status_code == 401
+
+    # New password works
+    resp_new = await client.post("/api/v1/auth/login", json={
+        "email": "pwchange@example.com",
+        "password": "newpassword1",
+    })
+    assert resp_new.status_code == 200
+
+
+# ── Malformed inputs (422 validation) ───────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_register_missing_fields(client):
+    """Register with missing fields → 422."""
+    resp = await client.post("/api/v1/auth/register", json={})
+    assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_register_empty_password(client):
+    """Register with empty password → 422 (min_length=8)."""
+    resp = await client.post("/api/v1/auth/register", json={
+        "email": "a@b.com",
+        "password": "",
+        "display_name": "X",
+        "invite_code": "CODE",
+    })
+    assert resp.status_code == 422
+
+
+@pytest.mark.asyncio
+async def test_login_empty_body(client):
+    """Login with empty body → 422."""
+    resp = await client.post("/api/v1/auth/login", json={})
+    assert resp.status_code == 422
+
+
+# ── Public endpoints unaffected ──────────────────────────────────────────────
+
+
+@pytest.mark.asyncio
+async def test_public_techniques_no_auth(client, db_engine):
+    """GET /api/v1/techniques works without auth."""
+    resp = await client.get("/api/v1/techniques")
+    # 200 even if empty — no 401/403
+    assert resp.status_code == 200
+
+
+@pytest.mark.asyncio
+async def test_public_creators_no_auth(client, db_engine):
+    """GET /api/v1/creators works without auth."""
+    resp = await client.get("/api/v1/creators")
+    assert resp.status_code == 200