diff --git a/backend/app/gateway/app.py b/backend/app/gateway/app.py
index dd5701083..aa49b4ffc 100644
--- a/backend/app/gateway/app.py
+++ b/backend/app/gateway/app.py
@@ -6,6 +6,7 @@ from contextlib import asynccontextmanager
 from fastapi import FastAPI
 from fastapi.middleware.cors import CORSMiddleware
 
+from app.gateway.auth_disabled import warn_if_auth_disabled_enabled
 from app.gateway.auth_middleware import AuthMiddleware
 from app.gateway.config import get_gateway_config
 from app.gateway.csrf_middleware import CSRFMiddleware, get_configured_cors_origins
@@ -172,6 +173,7 @@ async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
         startup_config = get_app_config()
         apply_logging_level(startup_config.log_level)
         logger.info("Configuration loaded successfully")
+        warn_if_auth_disabled_enabled()
     except Exception as e:
         error_msg = f"Failed to load configuration during gateway startup: {e}"
         logger.exception(error_msg)
diff --git a/backend/app/gateway/auth_disabled.py b/backend/app/gateway/auth_disabled.py
new file mode 100644
index 000000000..396de7129
--- /dev/null
+++ b/backend/app/gateway/auth_disabled.py
@@ -0,0 +1,54 @@
+"""Shared helpers for local/E2E auth-disabled mode."""
+
+from __future__ import annotations
+
+import logging
+import os
+from types import SimpleNamespace
+
+AUTH_DISABLED_ENV_VAR = "DEER_FLOW_AUTH_DISABLED"
+AUTH_DISABLED_USER_ID = "e2e-user"
+AUTH_DISABLED_USER_EMAIL = "e2e@test.local"
+
+AUTH_SOURCE_SESSION = "session"
+AUTH_SOURCE_INTERNAL = "internal"
+AUTH_SOURCE_AUTH_DISABLED = "auth_disabled"
+
+_PRODUCTION_ENV_VARS: tuple[str, ...] = ("DEER_FLOW_ENV", "ENVIRONMENT")
+_PRODUCTION_ENV_VALUES: frozenset[str] = frozenset({"prod", "production"})
+
+logger = logging.getLogger(__name__)
+
+
+def is_explicit_production_environment() -> bool:
+    return any(os.environ.get(name, "").strip().lower() in _PRODUCTION_ENV_VALUES for name in _PRODUCTION_ENV_VARS)
+
+
+def is_auth_disabled_requested() -> bool:
+    return os.environ.get(AUTH_DISABLED_ENV_VAR) == "1"
+
+
+def is_auth_disabled() -> bool:
+    return is_auth_disabled_requested() and not is_explicit_production_environment()
+
+
+def warn_if_auth_disabled_enabled() -> None:
+    if not is_auth_disabled():
+        return
+
+    logger.warning(
+        "%s=1 is active: authentication is bypassed and anonymous requests run as synthetic admin user %r. Do not enable this in shared or production deployments.",
+        AUTH_DISABLED_ENV_VAR,
+        AUTH_DISABLED_USER_ID,
+    )
+
+
+def get_auth_disabled_user():
+    return SimpleNamespace(
+        id=AUTH_DISABLED_USER_ID,
+        email=AUTH_DISABLED_USER_EMAIL,
+        password_hash=None,
+        system_role="admin",
+        needs_setup=False,
+        token_version=0,
+    )
diff --git a/backend/app/gateway/auth_middleware.py b/backend/app/gateway/auth_middleware.py
index 6b6452264..6d71186a0 100644
--- a/backend/app/gateway/auth_middleware.py
+++ b/backend/app/gateway/auth_middleware.py
@@ -17,6 +17,13 @@ from starlette.responses import JSONResponse
 from starlette.types import ASGIApp
 
 from app.gateway.auth.errors import AuthErrorCode, AuthErrorResponse
+from app.gateway.auth_disabled import (
+    AUTH_SOURCE_AUTH_DISABLED,
+    AUTH_SOURCE_INTERNAL,
+    AUTH_SOURCE_SESSION,
+    get_auth_disabled_user,
+    is_auth_disabled,
+)
 from app.gateway.authz import _ALL_PERMISSIONS, AuthContext
 from app.gateway.internal_auth import INTERNAL_AUTH_HEADER_NAME, get_internal_user, is_valid_internal_auth_token
 from deerflow.runtime.user_context import reset_current_user, set_current_user
@@ -80,8 +87,38 @@ class AuthMiddleware(BaseHTTPMiddleware):
         if is_valid_internal_auth_token(request.headers.get(INTERNAL_AUTH_HEADER_NAME)):
             internal_user = get_internal_user()
 
+        auth_source = AUTH_SOURCE_SESSION
+        access_token = request.cookies.get("access_token")
+
         # Non-public path: require session cookie
-        if internal_user is None and not request.cookies.get("access_token"):
+        if internal_user is not None:
+            user = internal_user
+            auth_source = AUTH_SOURCE_INTERNAL
+        elif access_token:
+            # Strict JWT validation: reject junk/expired tokens with 401
+            # right here instead of silently passing through. This closes
+            # the "junk cookie bypass" gap (AUTH_TEST_PLAN test 7.5.8):
+            # without this, non-isolation routes like /api/models would
+            # accept any cookie-shaped string as authentication.
+            #
+            # We call the *strict* resolver so that fine-grained error
+            # codes (token_expired, token_invalid, user_not_found, …)
+            # propagate from AuthErrorCode, not get flattened into one
+            # generic code. BaseHTTPMiddleware doesn't let HTTPException
+            # bubble up, so we catch and render it as JSONResponse here.
+            from app.gateway.deps import get_current_user_from_request
+
+            try:
+                user = await get_current_user_from_request(request)
+            except HTTPException as exc:
+                if not is_auth_disabled():
+                    return JSONResponse(status_code=exc.status_code, content={"detail": exc.detail})
+                user = get_auth_disabled_user()
+                auth_source = AUTH_SOURCE_AUTH_DISABLED
+        elif is_auth_disabled():
+            user = get_auth_disabled_user()
+            auth_source = AUTH_SOURCE_AUTH_DISABLED
+        else:
             return JSONResponse(
                 status_code=401,
                 content={
@@ -92,32 +129,12 @@ class AuthMiddleware(BaseHTTPMiddleware):
                 },
             )
 
-        # Strict JWT validation: reject junk/expired tokens with 401
-        # right here instead of silently passing through. This closes
-        # the "junk cookie bypass" gap (AUTH_TEST_PLAN test 7.5.8):
-        # without this, non-isolation routes like /api/models would
-        # accept any cookie-shaped string as authentication.
-        #
-        # We call the *strict* resolver so that fine-grained error
-        # codes (token_expired, token_invalid, user_not_found, …)
-        # propagate from AuthErrorCode, not get flattened into one
-        # generic code. BaseHTTPMiddleware doesn't let HTTPException
-        # bubble up, so we catch and render it as JSONResponse here.
-        from app.gateway.deps import get_current_user_from_request
-
-        if internal_user is not None:
-            user = internal_user
-        else:
-            try:
-                user = await get_current_user_from_request(request)
-            except HTTPException as exc:
-                return JSONResponse(status_code=exc.status_code, content={"detail": exc.detail})
-
         # Stamp both request.state.user (for the contextvar pattern)
         # and request.state.auth (so @require_permission's "auth is
         # None" branch short-circuits instead of running the entire
         # JWT-decode + DB-lookup pipeline a second time per request).
         request.state.user = user
+        request.state.auth_source = auth_source
         request.state.auth = AuthContext(user=user, permissions=_ALL_PERMISSIONS)
         token = set_current_user(user)
         try:
diff --git a/backend/app/gateway/csrf_middleware.py b/backend/app/gateway/csrf_middleware.py
index f34882032..c9edb83b2 100644
--- a/backend/app/gateway/csrf_middleware.py
+++ b/backend/app/gateway/csrf_middleware.py
@@ -14,6 +14,8 @@ from starlette.middleware.base import BaseHTTPMiddleware
 from starlette.responses import JSONResponse
 from starlette.types import ASGIApp
 
+from app.gateway.auth_disabled import is_auth_disabled
+
 CSRF_COOKIE_NAME = "csrf_token"
 CSRF_HEADER_NAME = "X-CSRF-Token"
 CSRF_TOKEN_LENGTH = 64  # bytes
@@ -38,6 +40,9 @@ def should_check_csrf(request: Request) -> bool:
     if request.method not in ("POST", "PUT", "DELETE", "PATCH"):
         return False
 
+    if is_auth_disabled():
+        return False
+
     path = request.url.path.rstrip("/")
     # Exempt /api/v1/auth/me endpoint
     if path == "/api/v1/auth/me":
diff --git a/backend/app/gateway/deps.py b/backend/app/gateway/deps.py
index 5739d217d..c192828d9 100644
--- a/backend/app/gateway/deps.py
+++ b/backend/app/gateway/deps.py
@@ -331,6 +331,17 @@ async def get_current_user_from_request(request: Request):
 
     Raises HTTPException 401 if not authenticated.
     """
+    state = getattr(request, "state", None)
+    state_user = getattr(state, "user", None)
+    from app.gateway.auth_disabled import AUTH_SOURCE_AUTH_DISABLED, AUTH_SOURCE_INTERNAL, AUTH_SOURCE_SESSION
+
+    if state_user is not None and getattr(state, "auth_source", None) in {
+        AUTH_SOURCE_SESSION,
+        AUTH_SOURCE_AUTH_DISABLED,
+        AUTH_SOURCE_INTERNAL,
+    }:
+        return state_user
+
     from app.gateway.auth import decode_token
     from app.gateway.auth.errors import AuthErrorCode, AuthErrorResponse, TokenError, token_error_to_code
 
diff --git a/backend/app/gateway/langgraph_auth.py b/backend/app/gateway/langgraph_auth.py
index 202fab2d5..3ab3d2070 100644
--- a/backend/app/gateway/langgraph_auth.py
+++ b/backend/app/gateway/langgraph_auth.py
@@ -20,6 +20,7 @@ from langgraph_sdk import Auth
 
 from app.gateway.auth.errors import TokenError
 from app.gateway.auth.jwt import decode_token
+from app.gateway.auth_disabled import AUTH_DISABLED_USER_ID, is_auth_disabled
 from app.gateway.deps import get_local_provider
 
 auth = Auth()
@@ -38,6 +39,9 @@ def _check_csrf(request) -> None:
     if method.upper() not in _CSRF_METHODS:
         return
 
+    if is_auth_disabled():
+        return
+
     cookie_token = request.cookies.get("csrf_token")
     header_token = request.headers.get("x-csrf-token")
 
@@ -66,6 +70,9 @@ async def authenticate(request):
     # are rejected early, even if the cookie carries a valid JWT.
     _check_csrf(request)
 
+    if is_auth_disabled():
+        return AUTH_DISABLED_USER_ID
+
     token = request.cookies.get("access_token")
     if not token:
         raise Auth.exceptions.HTTPException(
diff --git a/backend/app/gateway/routers/auth.py b/backend/app/gateway/routers/auth.py
index e57182c26..ee4f074d2 100644
--- a/backend/app/gateway/routers/auth.py
+++ b/backend/app/gateway/routers/auth.py
@@ -341,9 +341,19 @@ async def change_password(request: Request, response: Response, body: ChangePass
     - Re-issues session cookie with new token_version
     """
     from app.gateway.auth.password import hash_password_async, verify_password_async
+    from app.gateway.auth_disabled import AUTH_SOURCE_AUTH_DISABLED
 
     user = await get_current_user_from_request(request)
 
+    if getattr(request.state, "auth_source", None) == AUTH_SOURCE_AUTH_DISABLED:
+        raise HTTPException(
+            status_code=status.HTTP_400_BAD_REQUEST,
+            detail=AuthErrorResponse(
+                code=AuthErrorCode.INVALID_CREDENTIALS,
+                message="Password changes are not available when DEER_FLOW_AUTH_DISABLED=1.",
+            ).model_dump(),
+        )
+
     if user.password_hash is None:
         raise HTTPException(status_code=status.HTTP_400_BAD_REQUEST, detail=AuthErrorResponse(code=AuthErrorCode.INVALID_CREDENTIALS, message="OAuth users cannot change password").model_dump())
 
diff --git a/backend/tests/test_auth_middleware.py b/backend/tests/test_auth_middleware.py
index 726786ac9..838bf57af 100644
--- a/backend/tests/test_auth_middleware.py
+++ b/backend/tests/test_auth_middleware.py
@@ -4,6 +4,7 @@ import pytest
 from starlette.testclient import TestClient
 
 from app.gateway.auth_middleware import AuthMiddleware, _is_public
+from app.gateway.csrf_middleware import CSRFMiddleware
 
 # ── _is_public unit tests ─────────────────────────────────────────────────
 
@@ -88,7 +89,9 @@ def test_unknown_api_path_is_protected():
 
 def _make_app():
     """Create a minimal FastAPI app with AuthMiddleware for testing."""
-    from fastapi import FastAPI
+    from fastapi import FastAPI, Request
+
+    from deerflow.runtime.user_context import get_effective_user_id
 
     app = FastAPI()
     app.add_middleware(AuthMiddleware)
@@ -98,8 +101,16 @@ def _make_app():
         return {"status": "ok"}
 
     @app.get("/api/v1/auth/me")
-    async def auth_me():
-        return {"id": "1", "email": "test@test.com"}
+    async def auth_me(request: Request):
+        from app.gateway.deps import get_current_user_from_request
+
+        user = await get_current_user_from_request(request)
+        return {
+            "id": str(user.id),
+            "email": user.email,
+            "system_role": user.system_role,
+            "needs_setup": user.needs_setup,
+        }
 
     @app.get("/api/v1/auth/setup-status")
     async def setup_status():
@@ -109,6 +120,29 @@ def _make_app():
     async def models_get():
         return {"models": []}
 
+    @app.get("/api/whoami")
+    async def whoami(request: Request):
+        user = request.state.user
+        return {
+            "id": str(user.id),
+            "email": getattr(user, "email", None),
+            "system_role": getattr(user, "system_role", None),
+            "context_user_id": get_effective_user_id(),
+        }
+
+    @app.get("/api/current-user-from-dep")
+    async def current_user_from_dep(request: Request):
+        from app.gateway.deps import get_current_user_from_request
+
+        user = await get_current_user_from_request(request)
+        state_user = request.state.user
+        return {
+            "id": str(user.id),
+            "state_id": str(state_user.id),
+            "auth_source": request.state.auth_source,
+            "context_user_id": get_effective_user_id(),
+        }
+
     @app.put("/api/mcp/config")
     async def mcp_put():
         return {"ok": True}
@@ -132,8 +166,24 @@ def _make_app():
     return app
 
 
+def _make_auth_csrf_app():
+    """Create a minimal app with production middleware ordering."""
+    from fastapi import FastAPI
+
+    app = FastAPI()
+    app.add_middleware(AuthMiddleware)
+    app.add_middleware(CSRFMiddleware)
+
+    @app.post("/api/threads/abc/runs/stream")
+    async def protected_mutation():
+        return {"ok": True}
+
+    return app
+
+
 @pytest.fixture
-def client():
+def client(monkeypatch):
+    monkeypatch.delenv("DEER_FLOW_AUTH_DISABLED", raising=False)
     return TestClient(_make_app())
 
 
@@ -161,6 +211,139 @@ def test_protected_path_no_cookie_returns_401(client):
     assert body["detail"]["code"] == "not_authenticated"
 
 
+def test_auth_disabled_allows_protected_path_without_cookie(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    client = TestClient(_make_app())
+
+    res = client.get("/api/models")
+
+    assert res.status_code == 200
+    assert res.json() == {"models": []}
+
+
+def test_auth_disabled_stamps_e2e_admin_user_without_cookie(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    client = TestClient(_make_app())
+
+    res = client.get("/api/whoami")
+
+    assert res.status_code == 200
+    assert res.json() == {
+        "id": "e2e-user",
+        "email": "e2e@test.local",
+        "system_role": "admin",
+        "context_user_id": "e2e-user",
+    }
+
+
+def test_auth_disabled_auth_me_reuses_middleware_user_without_cookie(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    client = TestClient(_make_app())
+
+    res = client.get("/api/v1/auth/me")
+
+    assert res.status_code == 200
+    assert res.json() == {
+        "id": "e2e-user",
+        "email": "e2e@test.local",
+        "system_role": "admin",
+        "needs_setup": False,
+    }
+
+
+def test_auth_disabled_does_not_clobber_valid_session_cookie(monkeypatch):
+    from types import SimpleNamespace
+
+    async def fake_current_user(request):
+        return SimpleNamespace(
+            id="session-user",
+            email="session@test.local",
+            system_role="user",
+            needs_setup=False,
+        )
+
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    monkeypatch.setattr("app.gateway.deps.get_current_user_from_request", fake_current_user)
+    client = TestClient(_make_app())
+
+    res = client.get("/api/whoami", cookies={"access_token": "valid-session"})
+
+    assert res.status_code == 200
+    assert res.json() == {
+        "id": "session-user",
+        "email": "session@test.local",
+        "system_role": "user",
+        "context_user_id": "session-user",
+    }
+
+
+def test_auth_disabled_does_not_clobber_internal_auth_identity(monkeypatch):
+    from app.gateway.internal_auth import create_internal_auth_headers
+    from deerflow.runtime.user_context import DEFAULT_USER_ID
+
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    client = TestClient(_make_app())
+
+    res = client.get(
+        "/api/current-user-from-dep",
+        headers=create_internal_auth_headers(),
+    )
+
+    assert res.status_code == 200
+    assert res.json() == {
+        "id": DEFAULT_USER_ID,
+        "state_id": DEFAULT_USER_ID,
+        "auth_source": "internal",
+        "context_user_id": DEFAULT_USER_ID,
+    }
+
+
+def test_auth_disabled_skips_csrf_for_state_changing_requests(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    client = TestClient(_make_auth_csrf_app())
+
+    res = client.post("/api/threads/abc/runs/stream")
+
+    assert res.status_code == 200
+    assert res.json() == {"ok": True}
+
+
+def test_auth_disabled_is_ignored_in_explicit_production_env(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    monkeypatch.setenv("DEER_FLOW_ENV", "production")
+    client = TestClient(_make_app())
+
+    res = client.get("/api/models")
+
+    assert res.status_code == 401
+
+
+def test_auth_disabled_startup_warning_when_effective(monkeypatch, caplog):
+    from app.gateway.auth_disabled import warn_if_auth_disabled_enabled
+
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    monkeypatch.delenv("DEER_FLOW_ENV", raising=False)
+    monkeypatch.delenv("ENVIRONMENT", raising=False)
+
+    with caplog.at_level("WARNING", logger="app.gateway.auth_disabled"):
+        warn_if_auth_disabled_enabled()
+
+    assert "authentication is bypassed" in caplog.text
+    assert "e2e-user" in caplog.text
+
+
+def test_auth_disabled_startup_warning_suppressed_in_explicit_production_env(monkeypatch, caplog):
+    from app.gateway.auth_disabled import warn_if_auth_disabled_enabled
+
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+    monkeypatch.setenv("ENVIRONMENT", "production")
+
+    with caplog.at_level("WARNING", logger="app.gateway.auth_disabled"):
+        warn_if_auth_disabled_enabled()
+
+    assert "authentication is bypassed" not in caplog.text
+
+
 def test_protected_path_with_junk_cookie_rejected(client):
     """Junk cookie → 401. Middleware strictly validates the JWT now
     (AUTH_TEST_PLAN test 7.5.8); it no longer silently passes bad
diff --git a/backend/tests/test_langgraph_auth.py b/backend/tests/test_langgraph_auth.py
index d2ee81051..1d2d71e7c 100644
--- a/backend/tests/test_langgraph_auth.py
+++ b/backend/tests/test_langgraph_auth.py
@@ -21,6 +21,7 @@ from langgraph_sdk import Auth
 from app.gateway.auth.config import AuthConfig, set_auth_config
 from app.gateway.auth.jwt import create_access_token, decode_token
 from app.gateway.auth.models import User
+from app.gateway.auth_disabled import AUTH_DISABLED_USER_ID
 from app.gateway.langgraph_auth import add_owner_filter, authenticate
 
 # ── Helpers ───────────────────────────────────────────────────────────────
@@ -59,6 +60,14 @@ def test_no_cookie_raises_401():
     assert "Not authenticated" in str(exc.value.detail)
 
 
+def test_auth_disabled_skips_csrf_and_authenticates_e2e_user(monkeypatch):
+    monkeypatch.setenv("DEER_FLOW_AUTH_DISABLED", "1")
+
+    identity = asyncio.run(authenticate(_req(method="POST")))
+
+    assert identity == AUTH_DISABLED_USER_ID
+
+
 def test_invalid_jwt_raises_401():
     with pytest.raises(Auth.exceptions.HTTPException) as exc:
         asyncio.run(authenticate(_req({"access_token": "garbage"})))
diff --git a/frontend/playwright.real-backend.config.ts b/frontend/playwright.real-backend.config.ts
index 9db673b90..091386686 100644
--- a/frontend/playwright.real-backend.config.ts
+++ b/frontend/playwright.real-backend.config.ts
@@ -7,8 +7,9 @@ import { defineConfig, devices } from "@playwright/test";
  * so the mock-based suite is untouched.
  *
  * Two webServers are started: the replay gateway (:8011) and the frontend
- * (:3000, pointed at the gateway). Auth uses a throwaway test account the spec
- * registers at runtime — no secrets.
+ * (:3000, pointed at the gateway). Auth-disabled mode is enabled on both
+ * servers so the no-cookie e2e contract is covered; specs that need session
+ * cookies still register a throwaway test account at runtime.
  */
 export default defineConfig({
   testDir: "./tests/e2e-real-backend",
@@ -38,7 +39,10 @@ export default defineConfig({
       // Mount the test-only run/message seeder used by multi-run-order.spec.ts
       // (#3352). The endpoint exists only on this replay gateway, never in the
       // production app.
-      env: { DEERFLOW_ENABLE_TEST_SEED: "1" },
+      env: {
+        DEERFLOW_ENABLE_TEST_SEED: "1",
+        DEER_FLOW_AUTH_DISABLED: "1",
+      },
     },
     {
       command: "pnpm build && pnpm start",
diff --git a/frontend/src/core/auth/auth-disabled-user.ts b/frontend/src/core/auth/auth-disabled-user.ts
new file mode 100644
index 000000000..2e26a8911
--- /dev/null
+++ b/frontend/src/core/auth/auth-disabled-user.ts
@@ -0,0 +1,23 @@
+import type { User } from "./types";
+
+export const AUTH_DISABLED_USER: User = {
+  id: "e2e-user",
+  email: "e2e@test.local",
+  system_role: "admin",
+  needs_setup: false,
+};
+
+const PRODUCTION_ENV_VALUES = new Set(["prod", "production"]);
+
+function isExplicitProductionEnvironment() {
+  return ["DEER_FLOW_ENV", "ENVIRONMENT"].some((name) =>
+    PRODUCTION_ENV_VALUES.has((process.env[name] ?? "").trim().toLowerCase()),
+  );
+}
+
+export function isAuthDisabledMode() {
+  return (
+    process.env.DEER_FLOW_AUTH_DISABLED === "1" &&
+    !isExplicitProductionEnvironment()
+  );
+}
diff --git a/frontend/src/core/auth/server.ts b/frontend/src/core/auth/server.ts
index 5712f1e89..198ef087c 100644
--- a/frontend/src/core/auth/server.ts
+++ b/frontend/src/core/auth/server.ts
@@ -2,6 +2,7 @@ import { cookies } from "next/headers";
 
 import { isStaticWebsiteOnly } from "../static-mode";
 
+import { AUTH_DISABLED_USER, isAuthDisabledMode } from "./auth-disabled-user";
 import { getGatewayConfig } from "./gateway-config";
 import { STATIC_WEBSITE_USER } from "./static-user";
 import { type AuthResult, userSchema } from "./types";
@@ -20,15 +21,10 @@ export async function getServerSideUser(): Promise<AuthResult> {
     };
   }
 
-  if (process.env.DEER_FLOW_AUTH_DISABLED === "1") {
+  if (isAuthDisabledMode()) {
     return {
       tag: "authenticated",
-      user: {
-        id: "e2e-user",
-        email: "e2e@test.local",
-        system_role: "admin",
-        needs_setup: false,
-      },
+      user: AUTH_DISABLED_USER,
     };
   }
 
diff --git a/frontend/src/core/threads/hooks.ts b/frontend/src/core/threads/hooks.ts
index 4418a9e26..2ac1a1814 100644
--- a/frontend/src/core/threads/hooks.ts
+++ b/frontend/src/core/threads/hooks.ts
@@ -364,7 +364,7 @@ export function useThreadStream({
     loadMore: loadMoreHistory,
     loading: isHistoryLoading,
     appendMessages,
-  } = useThreadHistory(onStreamThreadId ?? "");
+  } = useThreadHistory(onStreamThreadId ?? "", { enabled: !isMock });
 
   // Keep listeners ref updated with latest callbacks
   useEffect(() => {
@@ -854,8 +854,15 @@ export function useThreadStream({
   } as const;
 }
 
-export function useThreadHistory(threadId: string) {
-  const runs = useThreadRuns(threadId);
+type ThreadHistoryOptions = {
+  enabled?: boolean;
+};
+
+export function useThreadHistory(
+  threadId: string,
+  { enabled = true }: ThreadHistoryOptions = {},
+) {
+  const runs = useThreadRuns(threadId, { enabled });
   const threadIdRef = useRef(threadId);
   const runsRef = useRef(runs.data ?? []);
   const indexRef = useRef(-1);
@@ -864,10 +871,15 @@ export function useThreadHistory(threadId: string) {
   const loadingRunIdRef = useRef<string | null>(null);
   const loadedRunIdsRef = useRef<Set<string>>(new Set());
   const runBeforeSeqRef = useRef<Map<string, number>>(new Map());
+  const loadGenerationRef = useRef(0);
   const [loading, setLoading] = useState(false);
   const [messages, setMessages] = useState<Message[]>([]);
 
   const loadMessages = useCallback(async () => {
+    if (!enabled) {
+      return;
+    }
+    const loadGeneration = loadGenerationRef.current;
     if (loadingRef.current) {
       const pendingRunIndex = findLatestUnloadedRunIndex(
         runsRef.current,
@@ -921,12 +933,15 @@ export function useThreadHistory(threadId: string) {
         }).then((res) => {
           return res.json();
         });
+        if (
+          loadGenerationRef.current !== loadGeneration ||
+          threadIdRef.current !== requestThreadId
+        ) {
+          return;
+        }
         const _messages = result.data
           .filter((m) => !m.metadata.caller?.startsWith("middleware:"))
           .map((m) => m.content);
-        if (threadIdRef.current !== requestThreadId) {
-          return;
-        }
         setMessages((prev) =>
           dedupeMessagesByIdentity([..._messages, ...prev]),
         );
@@ -961,16 +976,19 @@ export function useThreadHistory(threadId: string) {
     } catch (err) {
       console.error(err);
     } finally {
-      loadingRef.current = false;
-      loadingRunIdRef.current = null;
-      setLoading(false);
+      if (loadGenerationRef.current === loadGeneration) {
+        loadingRef.current = false;
+        loadingRunIdRef.current = null;
+        setLoading(false);
+      }
     }
-  }, []);
+  }, [enabled]);
   useEffect(() => {
     const threadChanged = threadIdRef.current !== threadId;
     threadIdRef.current = threadId;
 
-    if (threadChanged) {
+    if (!enabled || threadChanged) {
+      loadGenerationRef.current += 1;
       runsRef.current = [];
       indexRef.current = -1;
       pendingLoadRef.current = false;
@@ -982,6 +1000,10 @@ export function useThreadHistory(threadId: string) {
       setMessages([]);
     }
 
+    if (!enabled) {
+      return;
+    }
+
     if (runs.data && runs.data.length > 0) {
       runsRef.current = runs.data ?? [];
       indexRef.current = findLatestUnloadedRunIndex(
@@ -992,14 +1014,15 @@ export function useThreadHistory(threadId: string) {
     loadMessages().catch(() => {
       toast.error("Failed to load thread history.");
     });
-  }, [threadId, runs.data, loadMessages]);
+  }, [enabled, threadId, runs.data, loadMessages]);
 
   const appendMessages = useCallback((_messages: Message[]) => {
     setMessages((prev) => {
       return dedupeMessagesByIdentity([...prev, ..._messages]);
     });
   }, []);
-  const hasMore = indexRef.current >= 0 || !runs.data;
+  const hasMore =
+    enabled && Boolean(threadId) && (indexRef.current >= 0 || !runs.data);
   return {
     runs: runs.data,
     messages,
@@ -1077,7 +1100,10 @@ export function useThreads(
   });
 }
 
-export function useThreadRuns(threadId?: string) {
+export function useThreadRuns(
+  threadId?: string,
+  { enabled = true }: { enabled?: boolean } = {},
+) {
   const apiClient = getAPIClient();
   return useQuery<Run[]>({
     queryKey: ["thread", threadId],
@@ -1088,6 +1114,7 @@ export function useThreadRuns(threadId?: string) {
       const response = await apiClient.runs.list(threadId);
       return response;
     },
+    enabled: enabled && Boolean(threadId),
     refetchOnWindowFocus: false,
   });
 }
diff --git a/frontend/tests/e2e-real-backend/auth-disabled-contract.spec.ts b/frontend/tests/e2e-real-backend/auth-disabled-contract.spec.ts
new file mode 100644
index 000000000..23cb08d40
--- /dev/null
+++ b/frontend/tests/e2e-real-backend/auth-disabled-contract.spec.ts
@@ -0,0 +1,16 @@
+import { expect, test } from "@playwright/test";
+
+import { AUTH_DISABLED_USER } from "../../src/core/auth/auth-disabled-user";
+
+const APP = "http://localhost:3000";
+
+test.describe("auth-disabled contract (real backend)", () => {
+  test("gateway /auth/me returns the frontend synthetic user without a cookie", async ({
+    context,
+  }) => {
+    const resp = await context.request.get(`${APP}/api/v1/auth/me`);
+
+    expect(resp.status(), await resp.text()).toBe(200);
+    await expect(resp.json()).resolves.toEqual(AUTH_DISABLED_USER);
+  });
+});
diff --git a/frontend/tests/e2e-real-backend/real-backend-render.spec.ts b/frontend/tests/e2e-real-backend/real-backend-render.spec.ts
index 97c367d41..19047445b 100644
--- a/frontend/tests/e2e-real-backend/real-backend-render.spec.ts
+++ b/frontend/tests/e2e-real-backend/real-backend-render.spec.ts
@@ -101,10 +101,11 @@ test.describe("real backend render (replay, no API key)", () => {
       EXPECTED_SUGGESTION,
       "fixture should contain a suggestions turn (re-record; the record spec waits for /suggestions)",
     ).not.toBe("");
-    await expect(page.getByText(EXPECTED_TITLE)).toBeVisible({
+    const chat = page.locator("#chat");
+    await expect(chat.getByText(EXPECTED_TITLE)).toBeVisible({
       timeout: 60_000,
     });
-    await expect(page.getByText(EXPECTED_SUGGESTION)).toBeVisible({
+    await expect(chat.getByText(EXPECTED_SUGGESTION)).toBeVisible({
       timeout: 30_000,
     });
 
diff --git a/frontend/tests/e2e/chat.spec.ts b/frontend/tests/e2e/chat.spec.ts
index 4650a3c2c..50ab3c871 100644
--- a/frontend/tests/e2e/chat.spec.ts
+++ b/frontend/tests/e2e/chat.spec.ts
@@ -12,6 +12,7 @@ test.describe("Chat workspace", () => {
 
     const textarea = page.getByPlaceholder(/how can i assist you/i);
     await expect(textarea).toBeVisible({ timeout: 15_000 });
+    await expect(page.getByRole("button", { name: /load more/i })).toBeHidden();
   });
 
   test("can type a message in the input box", async ({ page }) => {
diff --git a/frontend/tests/e2e/thread-history.spec.ts b/frontend/tests/e2e/thread-history.spec.ts
index 19fce310a..9476ca4ab 100644
--- a/frontend/tests/e2e/thread-history.spec.ts
+++ b/frontend/tests/e2e/thread-history.spec.ts
@@ -18,6 +18,7 @@ const THREADS = [
     updated_at: "2025-06-02T12:00:00Z",
   },
 ];
+const DEMO_THREAD_ID = "7cfa5f8f-a2f8-47ad-acbd-da7137baf990";
 
 test.describe("Thread history", () => {
   test("sidebar shows existing threads", async ({ page }) => {
@@ -61,6 +62,84 @@ test.describe("Thread history", () => {
     ).toBeVisible({ timeout: 15_000 });
   });
 
+  test("mock thread does not load real backend run history", async ({
+    page,
+  }) => {
+    mockLangGraphAPI(page, {
+      threads: [
+        {
+          thread_id: DEMO_THREAD_ID,
+          title: "Forecasting 2026 Trends and Opportunities",
+          updated_at: "2025-06-01T12:00:00Z",
+          messages: [
+            {
+              type: "human",
+              id: `run-human-${DEMO_THREAD_ID}`,
+              content: [
+                {
+                  type: "text",
+                  text: "This run-message endpoint should not be called.",
+                },
+              ],
+            },
+          ],
+        },
+      ],
+    });
+    const backendRunHistoryUrls: string[] = [];
+    await page.route(
+      /\/api\/langgraph\/threads\/[^/]+\/runs(?:\?|$)/,
+      (route) => {
+        if (
+          route.request().method() === "GET" &&
+          route
+            .request()
+            .url()
+            .includes(`/api/langgraph/threads/${DEMO_THREAD_ID}/runs`)
+        ) {
+          backendRunHistoryUrls.push(route.request().url());
+          return route.fulfill({
+            status: 500,
+            contentType: "application/json",
+            body: JSON.stringify({
+              error: "mock=true must not load real runs",
+            }),
+          });
+        }
+        return route.fallback();
+      },
+    );
+    await page.route(
+      /\/api\/threads\/[^/]+\/runs\/[^/]+\/messages(?:\?|$)/,
+      (route) => {
+        if (
+          route.request().method() === "GET" &&
+          route.request().url().includes(`/api/threads/${DEMO_THREAD_ID}/runs/`)
+        ) {
+          backendRunHistoryUrls.push(route.request().url());
+          return route.fulfill({
+            status: 500,
+            contentType: "application/json",
+            body: JSON.stringify({
+              error: "mock=true must not load real run messages",
+            }),
+          });
+        }
+        return route.fallback();
+      },
+    );
+
+    await page.goto(`/workspace/chats/${DEMO_THREAD_ID}?mock=true`);
+
+    await expect(
+      page.getByText("What might be the trends and opportunities in 2026?"),
+    ).toBeVisible({ timeout: 15_000 });
+    await expect(
+      page.getByText("I've created a modern, minimalist website"),
+    ).toBeVisible();
+    expect(backendRunHistoryUrls).toEqual([]);
+  });
+
   test("chats list page shows all threads", async ({ page }) => {
     mockLangGraphAPI(page, { threads: THREADS });
 
diff --git a/frontend/tests/unit/core/auth/server.test.ts b/frontend/tests/unit/core/auth/server.test.ts
index fea6ef830..1dd02da33 100644
--- a/frontend/tests/unit/core/auth/server.test.ts
+++ b/frontend/tests/unit/core/auth/server.test.ts
@@ -1,5 +1,6 @@
 import { afterEach, beforeEach, describe, expect, test, vi } from "vitest";
 
+import { AUTH_DISABLED_USER } from "@/core/auth/auth-disabled-user";
 import { STATIC_WEBSITE_USER } from "@/core/auth/static-user";
 
 vi.mock("next/headers", () => ({
@@ -10,6 +11,8 @@ vi.mock("next/headers", () => ({
 
 const ENV_KEYS = [
   "DEER_FLOW_AUTH_DISABLED",
+  "DEER_FLOW_ENV",
+  "ENVIRONMENT",
   "NEXT_PUBLIC_STATIC_WEBSITE_ONLY",
 ] as const;
 
@@ -51,6 +54,8 @@ describe("getServerSideUser", () => {
   beforeEach(() => {
     saved = snapshotEnv();
     setEnv("DEER_FLOW_AUTH_DISABLED", undefined);
+    setEnv("DEER_FLOW_ENV", undefined);
+    setEnv("ENVIRONMENT", undefined);
     setEnv("NEXT_PUBLIC_STATIC_WEBSITE_ONLY", undefined);
   });
 
@@ -74,4 +79,30 @@ describe("getServerSideUser", () => {
     });
     expect(fetchSpy).not.toHaveBeenCalled();
   });
+
+  test("bypasses gateway auth in auth-disabled mode", async () => {
+    setEnv("DEER_FLOW_AUTH_DISABLED", "1");
+    const fetchSpy = vi.fn(() => {
+      throw new Error("fetch should not be called in auth-disabled mode");
+    });
+    vi.stubGlobal("fetch", fetchSpy);
+
+    const { getServerSideUser } = await loadFreshServerAuth();
+
+    await expect(getServerSideUser()).resolves.toEqual({
+      tag: "authenticated",
+      user: AUTH_DISABLED_USER,
+    });
+    expect(fetchSpy).not.toHaveBeenCalled();
+  });
+
+  test("does not enable auth-disabled mode in explicit production environments", async () => {
+    setEnv("DEER_FLOW_AUTH_DISABLED", "1");
+    setEnv("DEER_FLOW_ENV", "production");
+
+    const { isAuthDisabledMode } =
+      await import("@/core/auth/auth-disabled-user");
+
+    expect(isAuthDisabledMode()).toBe(false);
+  });
 });