diff --git a/backend/app/gateway/auth/errors.py b/backend/app/gateway/auth/errors.py
index b5899ebd8..f4a68ae10 100644
--- a/backend/app/gateway/auth/errors.py
+++ b/backend/app/gateway/auth/errors.py
@@ -21,6 +21,7 @@ class AuthErrorCode(StrEnum):
     PROVIDER_NOT_FOUND = "provider_not_found"
     NOT_AUTHENTICATED = "not_authenticated"
     SYSTEM_ALREADY_INITIALIZED = "system_already_initialized"
+    REGISTRATION_DISABLED = "registration_disabled"
 
 
 class TokenError(StrEnum):
diff --git a/backend/app/gateway/routers/auth.py b/backend/app/gateway/routers/auth.py
index bf49ed50d..8b490c9cb 100644
--- a/backend/app/gateway/routers/auth.py
+++ b/backend/app/gateway/routers/auth.py
@@ -315,13 +315,46 @@ async def login_local(
     )
 
 
+def _local_registration_enabled() -> bool:
+    """Whether visitors may self-register a local account.
+
+    Local registration bypasses the OIDC provisioning policy entirely
+    (allowed_email_domains, require_verified_email, auto_create_users are only
+    enforced in the SSO callback), so SSO-provisioned deployments need a way to
+    close this path.
+
+    ``config.yaml`` is absent in bare-app contexts that never load it (tests build the
+    gateway without one). Registration was unconditionally open before this gate existed,
+    so an absent config file falls back to that same default rather than turning these two
+    endpoints into a hard dependency on the file. Only ``FileNotFoundError`` is caught:
+    a malformed config must not silently re-open a closed deployment, so it propagates.
+
+    ``/register`` reads this fresh on every request (``get_app_config`` reloads on file
+    change); ``/setup-status`` may serve it up to 60s stale via its per-IP result cache.
+    """
+    from deerflow.config.app_config import get_app_config
+
+    try:
+        return get_app_config().auth.local.allow_registration
+    except FileNotFoundError:
+        return True
+
+
 @router.post("/register", response_model=UserResponse, status_code=status.HTTP_201_CREATED)
 async def register(request: Request, response: Response, body: RegisterRequest):
     """Register a new user account (always 'user' role).
 
     The first admin is created explicitly through /initialize. This endpoint creates regular users.
     Auto-login by setting the session cookie.
+
+    Returns 403 when ``auth.local.allow_registration`` is false.
     """
+    if not _local_registration_enabled():
+        raise HTTPException(
+            status_code=status.HTTP_403_FORBIDDEN,
+            detail=AuthErrorResponse(code=AuthErrorCode.REGISTRATION_DISABLED, message="Self-registration is disabled on this deployment").model_dump(),
+        )
+
     try:
         user = await get_local_provider().create_user(email=body.email, password=body.password, system_role="user")
     except ValueError:
@@ -465,7 +498,7 @@ async def setup_status(request: Request):
 
             async def _compute_setup_status() -> dict:
                 admin_count = await get_local_provider().count_admin_users()
-                return {"needs_setup": admin_count == 0}
+                return {"needs_setup": admin_count == 0, "registration_enabled": _local_registration_enabled()}
 
             task = asyncio.create_task(_compute_setup_status())
             _SETUP_STATUS_INFLIGHT[client_ip] = task
diff --git a/backend/packages/harness/deerflow/config/auth_config.py b/backend/packages/harness/deerflow/config/auth_config.py
index b8ee0c74a..09f2b2380 100644
--- a/backend/packages/harness/deerflow/config/auth_config.py
+++ b/backend/packages/harness/deerflow/config/auth_config.py
@@ -67,7 +67,22 @@ class OIDCAuthConfig(BaseModel):
     )
 
 
+class LocalAuthConfig(BaseModel):
+    """Configuration for the built-in email/password authentication provider."""
+
+    allow_registration: bool = Field(
+        default=True,
+        description=(
+            "Allow visitors to self-register a local account via POST /api/v1/auth/register. "
+            "Set to false when accounts are provisioned exclusively through SSO — the OIDC "
+            "provisioning policy (allowed_email_domains, require_verified_email, auto_create_users) "
+            "does not apply to local registration."
+        ),
+    )
+
+
 class AuthAppConfig(BaseModel):
     """Authentication configuration section for the DeerFlow app config."""
 
     oidc: OIDCAuthConfig = Field(default_factory=OIDCAuthConfig, description="OIDC SSO authentication settings")
+    local: LocalAuthConfig = Field(default_factory=LocalAuthConfig, description="Built-in email/password authentication settings")
diff --git a/backend/tests/test_local_registration_gate.py b/backend/tests/test_local_registration_gate.py
new file mode 100644
index 000000000..9fb103aac
--- /dev/null
+++ b/backend/tests/test_local_registration_gate.py
@@ -0,0 +1,166 @@
+"""Local self-registration gate (``auth.local.allow_registration``).
+
+The OIDC provisioning policy (``allowed_email_domains``, ``require_verified_email``,
+``auto_create_users``) is enforced only in the SSO callback via
+``get_or_provision_oidc_user``. ``POST /api/v1/auth/register`` creates a local account
+without consulting any of it, so an SSO-provisioned deployment that declares a domain
+allowlist can still be joined by any address through the local path. These tests pin the
+gate that lets such a deployment close it.
+"""
+
+import secrets
+
+import pytest
+from fastapi.testclient import TestClient
+
+from app.gateway.auth.config import AuthConfig, set_auth_config
+from deerflow.config.auth_config import AuthAppConfig, LocalAuthConfig
+
+_TEST_SECRET = "test-secret-key-for-registration-gate-tests-only"
+
+
+@pytest.fixture(autouse=True)
+def _persistence_engine(tmp_path):
+    """Per-test SQLite engine + clean ``deps._cached_*`` (mirrors test_auth_type_system).
+
+    These tests drive the real ``/register`` handler, which reaches
+    ``SQLiteUserRepository`` → ``get_session_factory``. A fresh DB per test also means
+    the admin slot is empty for the /initialize case.
+    """
+    import asyncio
+
+    from app.gateway import deps
+    from deerflow.persistence.engine import close_engine, init_engine
+
+    asyncio.run(init_engine("sqlite", url=f"sqlite+aiosqlite:///{tmp_path}/registration_gate.db", sqlite_dir=str(tmp_path)))
+    deps._cached_local_provider = None
+    deps._cached_repo = None
+    try:
+        yield
+    finally:
+        deps._cached_local_provider = None
+        deps._cached_repo = None
+        asyncio.run(close_engine())
+
+
+@pytest.fixture
+def client(monkeypatch):
+    """TestClient whose gate reads a config we control.
+
+    Overrides only ``auth.local`` on a deep copy of the real config: the app lifespan
+    reads other sections (``database`` above all) to initialise the engine, and a
+    narrower stub would abort startup and leak an uninitialised engine into the
+    globals ``app.gateway.deps`` caches for the rest of the session.
+    """
+    from pathlib import Path
+
+    from deerflow.config.app_config import AppConfig
+
+    # config.yaml is gitignored, so tests cannot rely on it existing. The committed
+    # example is a valid config and gives every other section (database above all)
+    # a real value for the app lifespan.
+    baseline = AppConfig.from_file(str(Path(__file__).resolve().parents[2] / "config.example.yaml"))
+
+    def _make(*, allow_registration: bool) -> TestClient:
+        set_auth_config(AuthConfig(jwt_secret=_TEST_SECRET))
+        patched = baseline.model_copy(deep=True)
+        patched.auth = AuthAppConfig(local=LocalAuthConfig(allow_registration=allow_registration), oidc=baseline.auth.oidc)
+        monkeypatch.setattr("deerflow.config.app_config.get_app_config", lambda: patched)
+        # setup-status memoizes per client IP; drop it so each direction is read fresh.
+        from app.gateway.routers import auth as auth_router
+
+        auth_router._SETUP_STATUS_CACHE.clear()
+
+        from app.gateway.app import create_app
+
+        return TestClient(create_app())
+
+    return _make
+
+
+def _unique_email(prefix: str) -> str:
+    return f"{prefix}-{secrets.token_hex(4)}@test.com"
+
+
+def test_register_succeeds_when_registration_allowed(client):
+    """Default (allow_registration=True) keeps self-registration working."""
+    resp = client(allow_registration=True).post(
+        "/api/v1/auth/register",
+        json={"email": _unique_email("gate-allowed"), "password": "Tr0ub4dor3a!"},
+    )
+    assert resp.status_code == 201
+
+
+def test_register_rejected_when_registration_disabled(client):
+    """allow_registration=False closes the local self-registration path."""
+    resp = client(allow_registration=False).post(
+        "/api/v1/auth/register",
+        json={"email": _unique_email("gate-denied"), "password": "Tr0ub4dor3a!"},
+    )
+    assert resp.status_code == 403
+    assert resp.json()["detail"]["code"] == "registration_disabled"
+
+
+def test_register_rejected_before_the_account_is_created(client):
+    """The gate runs ahead of user creation — a denied email stays unregistered.
+
+    Guards against a gate placed after ``create_user``, which would 403 the caller
+    while still persisting the account.
+    """
+    email = _unique_email("gate-not-persisted")
+    denied = client(allow_registration=False)
+    assert denied.post("/api/v1/auth/register", json={"email": email, "password": "Tr0ub4dor3a!"}).status_code == 403
+
+    # Re-open registration: the same address must still be free, i.e. the denied
+    # attempt created nothing. A leaked account would surface as 400 email_already_exists.
+    resp = client(allow_registration=True).post(
+        "/api/v1/auth/register",
+        json={"email": email, "password": "Tr0ub4dor3a!"},
+    )
+    assert resp.status_code == 201
+
+
+def test_registration_defaults_to_allowed():
+    """The default must stay True — this change is meant to add an opt-in, not flip behaviour.
+
+    Flipping the default would silently close self-registration on every existing
+    deployment that never sets the key.
+    """
+    assert LocalAuthConfig().allow_registration is True
+    assert AuthAppConfig().local.allow_registration is True
+
+
+def test_gate_falls_back_to_open_when_config_is_absent(monkeypatch):
+    """No config.yaml → the pre-gate default (open), not a 500.
+
+    Bare-app contexts never load a config file. Before this gate, /register and
+    /setup-status did not read the app config at all; the fallback keeps that true.
+    """
+    from app.gateway.routers import auth as auth_router
+
+    def _raise() -> None:
+        raise FileNotFoundError("`config.yaml` file not found in the project root")
+
+    monkeypatch.setattr("deerflow.config.app_config.get_app_config", _raise)
+    assert auth_router._local_registration_enabled() is True
+
+
+@pytest.mark.parametrize("allowed", [True, False])
+def test_setup_status_reports_registration_state(client, allowed):
+    """The login page needs the flag to decide whether to offer a signup entry."""
+    resp = client(allow_registration=allowed).get("/api/v1/auth/setup-status")
+    assert resp.status_code == 200
+    assert resp.json()["registration_enabled"] is allowed
+
+
+def test_initialize_is_not_gated_by_the_registration_flag(client):
+    """Closing self-registration must never block first-boot admin creation.
+
+    ``config.example.yaml`` promises that turning the flag off cannot lock an operator
+    out of a fresh install; the per-test engine gives us a genuinely empty admin slot.
+    """
+    resp = client(allow_registration=False).post(
+        "/api/v1/auth/initialize",
+        json={"email": _unique_email("gate-initialize"), "password": "Tr0ub4dor3a!"},
+    )
+    assert resp.status_code == 201
diff --git a/config.example.yaml b/config.example.yaml
index 0e6583692..f63930449 100644
--- a/config.example.yaml
+++ b/config.example.yaml
@@ -15,7 +15,7 @@
 # ============================================================================
 # Bump this number when the config schema changes.
 # Run `make config-upgrade` to merge new fields into your local config.yaml.
-config_version: 28
+config_version: 29
 
 # ============================================================================
 # Logging
@@ -2003,7 +2003,24 @@ authorization:
 #   2. Add Valid Redirect URI: http://localhost:8001/api/v1/auth/callback/keycloak
 #   3. Add Web Origin: http://localhost:8001 (or your frontend origin)
 
+# ============================================================================
+# Local (email/password) authentication
+# ============================================================================
+# Self-registration via POST /api/v1/auth/register is open by default: anyone
+# who can reach the Gateway may create a regular user account.
+#
+# The OIDC provisioning policy below (allowed_email_domains, require_verified_email,
+# auto_create_users) is enforced only in the SSO callback. It does NOT constrain local
+# registration, so on an SSO-provisioned deployment leaving this open lets a visitor
+# create an account outside that policy. Set allow_registration: false there.
+#
+# The first admin account is always created through /initialize regardless of this
+# setting, so turning it off cannot lock you out of a fresh install.
+
 # auth:
+#   local:
+#     allow_registration: false
+#
 #   oidc:
 #     enabled: true
 #     # Base URL of the frontend, used for redirects after SSO callback.
diff --git a/deploy/helm/deer-flow/README.md b/deploy/helm/deer-flow/README.md
index 6eb8fdbf1..4405af16a 100644
--- a/deploy/helm/deer-flow/README.md
+++ b/deploy/helm/deer-flow/README.md
@@ -124,7 +124,7 @@ they resolve from the `secrets` map):
 
 ```yaml
 config: |
-  config_version: 28
+  config_version: 29
   models:
     - name: gpt-4
       use: langchain_openai:ChatOpenAI
diff --git a/deploy/helm/deer-flow/values.yaml b/deploy/helm/deer-flow/values.yaml
index 7fb10bd55..47b988cd2 100644
--- a/deploy/helm/deer-flow/values.yaml
+++ b/deploy/helm/deer-flow/values.yaml
@@ -240,7 +240,7 @@ ingress:
 # -- DeerFlow config.yaml content. Secrets MUST stay as $VAR references — never
 #    inline literal secret values here. The default enables provisioner sandbox.
 config: |
-  config_version: 28
+  config_version: 29
   log_level: info
 
   models: []
diff --git a/frontend/src/core/auth/setup.ts b/frontend/src/core/auth/setup.ts
index aafa13a47..055dc05c2 100644
--- a/frontend/src/core/auth/setup.ts
+++ b/frontend/src/core/auth/setup.ts
@@ -2,6 +2,7 @@ import { parseAuthError } from "./types";
 
 export type SetupStatusResponse = {
   needs_setup?: boolean;
+  registration_enabled?: boolean;
 };
 
 export type SetupStatusCheck = {
@@ -30,5 +31,11 @@ export function isSystemAlreadyInitializedError(data: unknown): boolean {
 }
 
 export function canCreateRegularAccount(check: SetupStatusCheck): boolean {
-  return check.checked && check.status?.needs_setup !== true;
+  // registration_enabled is absent on older Gateways; treat that as allowed so
+  // the signup entry only disappears when the backend actively closes it.
+  return (
+    check.checked &&
+    check.status?.needs_setup !== true &&
+    check.status?.registration_enabled !== false
+  );
 }
diff --git a/frontend/tests/unit/core/auth/setup.test.ts b/frontend/tests/unit/core/auth/setup.test.ts
index 5b0607b47..2937fc2a2 100644
--- a/frontend/tests/unit/core/auth/setup.test.ts
+++ b/frontend/tests/unit/core/auth/setup.test.ts
@@ -56,6 +56,28 @@ describe("auth setup helpers", () => {
     expect(canCreateRegularAccount({ checked: true, status: null })).toBe(true);
   });
 
+  test("regular sign-up follows the gateway's registration_enabled flag", () => {
+    expect(
+      canCreateRegularAccount({
+        checked: true,
+        status: { needs_setup: false, registration_enabled: false },
+      }),
+    ).toBe(false);
+    expect(
+      canCreateRegularAccount({
+        checked: true,
+        status: { needs_setup: false, registration_enabled: true },
+      }),
+    ).toBe(true);
+    // Older Gateways omit the field; absent must not hide the signup entry.
+    expect(
+      canCreateRegularAccount({
+        checked: true,
+        status: { needs_setup: false },
+      }),
+    ).toBe(true);
+  });
+
   test("detects already-initialized setup conflicts", () => {
     expect(
       isSystemAlreadyInitializedError({