diff --git a/.env.example b/.env.example
index 3048acf9..0d08ce8b 100644
--- a/.env.example
+++ b/.env.example
@@ -62,9 +62,9 @@ AUTH_PASSWORD_HASH=
 POCKETBASE_ADMIN_PASSWORD=
 
 # --- Demo mode (per-IP rate limits; OFF by default) ---
-# Set DEMO_MODE=true only on a PUBLIC demo where visitors chat against your key,
+# Set DEMO=true only on a PUBLIC demo where visitors chat against your key,
 # to cap per-visitor spend. Limit overrides are optional. See README "Demo mode".
-DEMO_MODE=false
+DEMO=false
 DEMO_RATE_LIMIT_PER_MIN=15
 DEMO_RATE_LIMIT_PER_HOUR=200
 
diff --git a/README.md b/README.md
index 370a51bb..709c99b9 100644
--- a/README.md
+++ b/README.md
@@ -105,13 +105,13 @@ Each response streams live, so these all make for a quick visual demo without an
 
 ## Demo mode (per-IP rate limits)
 
-If you host a **public demo URL** where anyone can chat against *your* provider key, unbounded use means runaway spend. Demo mode caps per-visitor (per-IP) usage so the demo is safe to leave open. It is **off by default** — local and private forks are unaffected — and only takes effect when you set `DEMO_MODE=true`.
+If you host a **public demo URL** where anyone can chat against *your* provider key, unbounded use means runaway spend. Demo mode caps per-visitor (per-IP) usage so the demo is safe to leave open. It is **off by default** — local and private forks are unaffected — and only takes effect when you set `DEMO=true`.
 
 Set these under the Render **Environment** tab (or your host environment) on the demo service:
 
 | Variable | Default | Purpose |
 |---|---|---|
-| `DEMO_MODE` | `false` | Master switch. Truthy: `1`, `true`, `yes`, `on` (case-insensitive). |
+| `DEMO` | `false` | Master switch. Truthy: `1`, `true`, `yes`, `on` (case-insensitive). |
 | `DEMO_RATE_LIMIT_PER_MIN` | `15` | Max spending requests per IP per minute. |
 | `DEMO_RATE_LIMIT_PER_HOUR` | `200` | Max spending requests per IP per hour. |
 
diff --git a/deeptutor/api/main.py b/deeptutor/api/main.py
index cf4a764d..70e5f474 100644
--- a/deeptutor/api/main.py
+++ b/deeptutor/api/main.py
@@ -283,7 +283,7 @@ async def selective_access_log(request, call_next):
 )
 
 
-# Demo-mode per-IP rate limiting. No-op unless DEMO_MODE is truthy, so local and
+# Demo-mode per-IP rate limiting. No-op unless DEMO is truthy, so local and
 # private forks are unaffected. This HTTP catch-all guards REST spenders; the
 # chat WebSocket loops (/chat, /ws) enforce the same limiter per-message, since
 # a WS handshake bypasses http middleware and one socket can send many LLM
@@ -382,7 +382,7 @@ async def demo_rate_limit(request, call_next):
 )
 
 # require_auth installs the current user; bind_demo_visitor partitions the demo
-# session store per visitor (no-op unless DEMO_MODE is on). Both run on every
+# session store per visitor (no-op unless DEMO is on). Both run on every
 # authenticated router below.
 _auth = [Depends(require_auth), Depends(bind_demo_visitor)]
 # Partner data is anchored at the admin workspace (data/partners) and shared
diff --git a/deeptutor/api/routers/auth.py b/deeptutor/api/routers/auth.py
index 2e7191c5..abc5c539 100644
--- a/deeptutor/api/routers/auth.py
+++ b/deeptutor/api/routers/auth.py
@@ -268,7 +268,7 @@ async def bind_demo_visitor(
 ) -> None:
     """Bind the per-visitor demo id from the ``X-Demo-Visitor`` header.
 
-    A no-op unless ``DEMO_MODE`` is on, so private deployments are unaffected.
+    A no-op unless ``DEMO`` is on, so private deployments are unaffected.
     In demo mode this partitions the shared in-memory session store per visitor
     (see ``get_sqlite_session_store``) so concurrent visitors don't see each
     other's chat history.
diff --git a/deeptutor/api/routers/chat.py b/deeptutor/api/routers/chat.py
index ec854b6e..ab55aaf9 100644
--- a/deeptutor/api/routers/chat.py
+++ b/deeptutor/api/routers/chat.py
@@ -90,7 +90,7 @@ async def websocket_chat(websocket: WebSocket):
                 await websocket.send_json({"type": "error", "message": "Message is required"})
                 continue
 
-            # Demo mode: cap per-IP LLM turns. No-op unless DEMO_MODE is set.
+            # Demo mode: cap per-IP LLM turns. No-op unless DEMO is set.
             # Reject just this message and keep the socket open.
             limiter = get_demo_limiter()
             if limiter.enabled:
diff --git a/deeptutor/api/routers/unified_ws.py b/deeptutor/api/routers/unified_ws.py
index d298a897..ff7d823d 100644
--- a/deeptutor/api/routers/unified_ws.py
+++ b/deeptutor/api/routers/unified_ws.py
@@ -55,7 +55,7 @@ async def unified_websocket(ws: WebSocket) -> None:
     subscription_tasks: dict[str, asyncio.Task[None]] = {}
 
     async def demo_rate_limited() -> bool:
-        """Demo mode: cap per-IP LLM turns. No-op unless DEMO_MODE is set.
+        """Demo mode: cap per-IP LLM turns. No-op unless DEMO is set.
 
         On deny, sends this file's error frame convention and returns True so
         the caller skips starting the turn (the socket stays open).
diff --git a/deeptutor/services/demo/rate_limiter.py b/deeptutor/services/demo/rate_limiter.py
index c7168915..b2bf65c7 100644
--- a/deeptutor/services/demo/rate_limiter.py
+++ b/deeptutor/services/demo/rate_limiter.py
@@ -17,9 +17,9 @@
 
 Configuration (read once from the environment)
 -----------------------------------------------
-* ``DEMO_MODE`` — bool, default ``false``. Truthy values (case-insensitive):
+* ``DEMO`` — bool, default ``false``. Truthy values (case-insensitive):
   ``1``, ``true``, ``yes``, ``on``. **Off by default**, so local and private
-  forks are unaffected; only the public demo service sets ``DEMO_MODE=true``.
+  forks are unaffected; only the public demo service sets ``DEMO=true``.
 * ``DEMO_RATE_LIMIT_PER_MIN`` — int, default ``15``.
 * ``DEMO_RATE_LIMIT_PER_HOUR`` — int, default ``200``.
 
@@ -132,7 +132,7 @@ def __init__(
         per_hour: int | None = None,
         time_fn: Callable[[], float] = time.monotonic,
     ) -> None:
-        self._enabled = _env_bool("DEMO_MODE") if enabled is None else enabled
+        self._enabled = _env_bool("DEMO") if enabled is None else enabled
         self._per_min = _env_int("DEMO_RATE_LIMIT_PER_MIN", 15) if per_min is None else per_min
         self._per_hour = _env_int("DEMO_RATE_LIMIT_PER_HOUR", 200) if per_hour is None else per_hour
         self._time_fn = time_fn
@@ -213,7 +213,7 @@ def get_demo_limiter() -> DemoRateLimiter:
 
 
 def is_demo_mode() -> bool:
-    """True when ``DEMO_MODE`` is enabled.
+    """True when ``DEMO`` is enabled.
 
     Shared guard for the demo's "history stays ephemeral" contract: any code
     path that would otherwise write conversation-derived state to disk checks
diff --git a/render.yaml b/render.yaml
index d7f2ca1f..8760ee96 100644
--- a/render.yaml
+++ b/render.yaml
@@ -49,11 +49,11 @@ services:
         value: UTC
 
       # --- Demo mode (per-IP rate limits) -----------------------------------
-      # OFF by default. Set DEMO_MODE=true only on a PUBLIC demo service where
+      # OFF by default. Set DEMO=true only on a PUBLIC demo service where
       # anyone can chat against your key, to cap per-visitor spend. See the
       # README "Demo mode" section. The two limit overrides are optional
       # (defaults: 15/min, 200/hour per IP).
-      # - key: DEMO_MODE
+      # - key: DEMO
       #   value: "true"
       # - key: DEMO_RATE_LIMIT_PER_MIN
       #   value: "15"
diff --git a/tests/api/test_demo_visitor_isolation.py b/tests/api/test_demo_visitor_isolation.py
index 03ff070c..3be9289a 100644
--- a/tests/api/test_demo_visitor_isolation.py
+++ b/tests/api/test_demo_visitor_isolation.py
@@ -29,7 +29,7 @@
 
 @pytest.fixture
 def demo_client(monkeypatch: pytest.MonkeyPatch, tmp_path: Path):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
     monkeypatch.setattr(rate_limiter, "_limiter", None)
     monkeypatch.setattr(sqlite_store, "_instances", {})
 
@@ -81,7 +81,7 @@ def test_missing_header_does_not_inherit_previous_visitor(demo_client):
 async def test_ws_require_auth_binds_visitor_from_query_param(monkeypatch):
     """The chat WebSocket carries the visitor id as a query param (WS upgrades
     can't set custom headers), and ``ws_require_auth`` must bind it."""
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
     monkeypatch.setattr(rate_limiter, "_limiter", None)
 
     from deeptutor.api.routers.auth import ws_require_auth
diff --git a/tests/services/demo/test_demo_ephemeral_persistence.py b/tests/services/demo/test_demo_ephemeral_persistence.py
index 44347199..08b7563f 100644
--- a/tests/services/demo/test_demo_ephemeral_persistence.py
+++ b/tests/services/demo/test_demo_ephemeral_persistence.py
@@ -4,7 +4,7 @@
 chat-history DB in-memory, but the turn runtime and the memory subsystem write
 conversation-derived state to disk through other paths. In demo mode those must
 be skipped too, otherwise history is still persisted on disk. Each test below
-pins the culprit write path and asserts it is a no-op when ``DEMO_MODE`` is on
+pins the culprit write path and asserts it is a no-op when ``DEMO`` is on
 and still writes when it is off.
 """
 
@@ -49,7 +49,7 @@ def _execution() -> _TurnExecution:
 
 
 def test_workspace_event_mirror_skipped_in_demo(tmp_paths, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     TurnRuntimeManager._mirror_event_to_workspace(
         _execution(), {"type": "assistant", "content": "secret history"}
@@ -60,7 +60,7 @@ def test_workspace_event_mirror_skipped_in_demo(tmp_paths, monkeypatch):
 
 
 def test_workspace_event_mirror_written_when_demo_off(tmp_paths, monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
+    monkeypatch.delenv("DEMO", raising=False)
 
     TurnRuntimeManager._mirror_event_to_workspace(
         _execution(), {"type": "assistant", "content": "kept history"}
@@ -73,7 +73,7 @@ def test_workspace_event_mirror_written_when_demo_off(tmp_paths, monkeypatch):
 
 @pytest.mark.asyncio
 async def test_memory_trace_append_skipped_in_demo(tmp_paths, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     await memory_trace.append(
         memory_trace.TraceEvent.new("chat", "preference_stated", {"text": "likes X"})
@@ -85,7 +85,7 @@ async def test_memory_trace_append_skipped_in_demo(tmp_paths, monkeypatch):
 
 @pytest.mark.asyncio
 async def test_memory_trace_append_written_when_demo_off(tmp_paths, monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
+    monkeypatch.delenv("DEMO", raising=False)
 
     await memory_trace.append(
         memory_trace.TraceEvent.new("chat", "preference_stated", {"text": "likes X"})
@@ -97,7 +97,7 @@ async def test_memory_trace_append_written_when_demo_off(tmp_paths, monkeypatch)
 
 @pytest.mark.asyncio
 async def test_write_preference_skipped_in_demo(tmp_paths, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     store = memory_store.MemoryStore()
     report = await store.write_preference(
@@ -112,7 +112,7 @@ async def test_write_preference_skipped_in_demo(tmp_paths, monkeypatch):
 
 @pytest.mark.asyncio
 async def test_write_preference_written_when_demo_off(tmp_paths, monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
+    monkeypatch.delenv("DEMO", raising=False)
 
     store = memory_store.MemoryStore()
     report = await store.write_preference(
diff --git a/tests/services/demo/test_demo_visitor_isolation.py b/tests/services/demo/test_demo_visitor_isolation.py
index 57ba8f30..7539f13f 100644
--- a/tests/services/demo/test_demo_visitor_isolation.py
+++ b/tests/services/demo/test_demo_visitor_isolation.py
@@ -40,7 +40,7 @@ def demo_env(monkeypatch: pytest.MonkeyPatch, tmp_path: Path):
 
 @pytest.mark.asyncio
 async def test_history_isolated_between_visitors(demo_env, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     # Visitor A starts a chat.
     token_a = set_visitor_id("visitor-a")
@@ -64,7 +64,7 @@ async def test_history_isolated_between_visitors(demo_env, monkeypatch):
 
 
 def test_same_visitor_reuses_one_store(demo_env, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     token = set_visitor_id("visitor-a")
     try:
@@ -74,7 +74,7 @@ def test_same_visitor_reuses_one_store(demo_env, monkeypatch):
 
 
 def test_non_demo_ignores_visitor_id(demo_env, monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
+    monkeypatch.delenv("DEMO", raising=False)
 
     token_a = set_visitor_id("visitor-a")
     store_a = get_sqlite_session_store()
diff --git a/tests/services/demo/test_rate_limiter.py b/tests/services/demo/test_rate_limiter.py
index aacd7a7d..4c401d3c 100644
--- a/tests/services/demo/test_rate_limiter.py
+++ b/tests/services/demo/test_rate_limiter.py
@@ -99,26 +99,26 @@ def test_disabled_always_allows():
 
 
 def test_disabled_by_default_when_env_unset(monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
-    limiter = DemoRateLimiter()  # reads env: DEMO_MODE unset -> disabled
+    monkeypatch.delenv("DEMO", raising=False)
+    limiter = DemoRateLimiter()  # reads env: DEMO unset -> disabled
     assert limiter.enabled is False
     assert limiter.hit("ip").allowed
 
 
 @pytest.mark.parametrize("value", ["1", "true", "TRUE", "yes", "on", "On"])
 def test_env_truthy_enables(monkeypatch, value):
-    monkeypatch.setenv("DEMO_MODE", value)
+    monkeypatch.setenv("DEMO", value)
     assert DemoRateLimiter().enabled is True
 
 
 @pytest.mark.parametrize("value", ["0", "false", "no", "off", "", "maybe"])
 def test_env_falsy_disables(monkeypatch, value):
-    monkeypatch.setenv("DEMO_MODE", value)
+    monkeypatch.setenv("DEMO", value)
     assert DemoRateLimiter().enabled is False
 
 
 def test_env_limits_parsed(monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
     monkeypatch.setenv("DEMO_RATE_LIMIT_PER_MIN", "2")
     monkeypatch.setenv("DEMO_RATE_LIMIT_PER_HOUR", "9")
     clock = _FakeClock()
@@ -129,7 +129,7 @@ def test_env_limits_parsed(monkeypatch):
 
 
 def test_env_bad_limits_fall_back_to_defaults(monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
     monkeypatch.setenv("DEMO_RATE_LIMIT_PER_MIN", "not-an-int")
     monkeypatch.setenv("DEMO_RATE_LIMIT_PER_HOUR", "-5")
     limiter = DemoRateLimiter(time_fn=_FakeClock())
diff --git a/tests/services/demo/test_session_store_demo.py b/tests/services/demo/test_session_store_demo.py
index 96c31144..f6dfe3f1 100644
--- a/tests/services/demo/test_session_store_demo.py
+++ b/tests/services/demo/test_session_store_demo.py
@@ -38,7 +38,7 @@ def reset_singletons(monkeypatch: pytest.MonkeyPatch, tmp_path: Path):
 
 
 def test_demo_mode_returns_in_memory_store(reset_singletons, monkeypatch):
-    monkeypatch.setenv("DEMO_MODE", "true")
+    monkeypatch.setenv("DEMO", "true")
 
     store = get_sqlite_session_store()
 
@@ -49,7 +49,7 @@ def test_demo_mode_returns_in_memory_store(reset_singletons, monkeypatch):
 
 
 def test_demo_mode_off_returns_on_disk_store(reset_singletons, monkeypatch):
-    monkeypatch.delenv("DEMO_MODE", raising=False)
+    monkeypatch.delenv("DEMO", raising=False)
 
     store = get_sqlite_session_store()
 
diff --git a/web/lib/demo-visitor.ts b/web/lib/demo-visitor.ts
index 888eaed5..420c8cea 100644
--- a/web/lib/demo-visitor.ts
+++ b/web/lib/demo-visitor.ts
@@ -1,6 +1,6 @@
 // Per-visitor id for the public demo.
 //
-// DeepTutor is single-user by design, so in DEMO_MODE the backend serves one
+// DeepTutor is single-user by design, so in DEMO the backend serves one
 // shared in-memory session store to every anonymous visitor. To keep each
 // visitor's chat history private, the browser mints a random id once, persists
 // it in localStorage, and sends it on every request (the `X-Demo-Visitor`