fix(config): reject demo+base_url split REST/WS environment

kalshi/async_client.py

@@ -82,6 +82,20 @@ def __init__(
         if config is not None:
             self._config = config
         else:
+            # #239: reject demo=True combined with an explicit non-demo
+            # base_url. The old setdefault logic silently honored base_url
+            # while still pinning ws_base_url to DEMO_WS_URL, producing a
+            # split REST/WS environment (real-money REST + demo WS feed).
+            if demo and base_url is not None and base_url.rstrip("/") != DEMO_BASE_URL:
+                raise ValueError(
+                    "Conflicting environment: demo=True together with explicit "
+                    f"base_url={base_url!r}. demo=True implies base_url="
+                    f"{DEMO_BASE_URL!r}; passing a different REST endpoint would "
+                    "leave ws_base_url pinned to the demo WS feed, producing a "
+                    "split REST/WS environment. Drop demo=True and pass both "
+                    "base_url and ws_base_url via a KalshiConfig, or use "
+                    "KalshiConfig.demo() / KalshiConfig.production()."
+                )
             config_kwargs: dict[str, object] = {}
             if base_url:
                 config_kwargs["base_url"] = base_url

kalshi/client.py

@@ -84,6 +84,20 @@ def __init__(
         if config is not None:
             self._config = config
         else:
+            # #239: reject demo=True combined with an explicit non-demo
+            # base_url. The old setdefault logic silently honored base_url
+            # while still pinning ws_base_url to DEMO_WS_URL, producing a
+            # split REST/WS environment (real-money REST + demo WS feed).
+            if demo and base_url is not None and base_url.rstrip("/") != DEMO_BASE_URL:
+                raise ValueError(
+                    "Conflicting environment: demo=True together with explicit "
+                    f"base_url={base_url!r}. demo=True implies base_url="
+                    f"{DEMO_BASE_URL!r}; passing a different REST endpoint would "
+                    "leave ws_base_url pinned to the demo WS feed, producing a "
+                    "split REST/WS environment. Drop demo=True and pass both "
+                    "base_url and ws_base_url via a KalshiConfig, or use "
+                    "KalshiConfig.demo() / KalshiConfig.production()."
+                )
             config_kwargs: dict[str, object] = {}
             if base_url:
                 config_kwargs["base_url"] = base_url

kalshi/config.py

@@ -88,6 +88,27 @@ def __post_init__(self) -> None:
                 f"KalshiConfig.base_url must include the /trade-api/v2 path "
                 f"component, got base_url={self.base_url!r}"
             )
+        # #239: reject split REST/WS environment. If base_url and ws_base_url
+        # resolve to *different* known Kalshi environments (prod vs demo), a
+        # caller who set demo=True alongside an explicit prod base_url would
+        # otherwise place live orders against signals from a demo book.
+        # Localhost on either side is fine (mock servers).
+        base_host = (urlparse(self.base_url).hostname or "").lower()
+        ws_host = (urlparse(self.ws_base_url).hostname or "").lower()
+        _prod_host = "api.elections.kalshi.com"
+        _demo_host = "demo-api.kalshi.co"
+        if (base_host == _prod_host and ws_host == _demo_host) or (
+            base_host == _demo_host and ws_host == _prod_host
+        ):
+            raise ValueError(
+                "KalshiConfig: split REST/WS environment is not allowed. "
+                f"base_url={self.base_url!r} and ws_base_url={self.ws_base_url!r} "
+                "resolve to different Kalshi environments (production vs demo). "
+                "REST and WS must point at the same environment to avoid placing "
+                "live orders against demo-derived signals (or vice versa). Use "
+                "KalshiConfig.production() / KalshiConfig.demo(), or pass both "
+                "base_url and ws_base_url explicitly."
+            )
         if self.http2:
             import importlib.util
 

tests/test_async_orders.py

@@ -56,9 +56,9 @@ def unauth_orders_async(config: KalshiConfig) -> AsyncOrdersResource:
 @pytest.fixture
 def client(test_auth: KalshiAuth) -> AsyncKalshiClient:
     """AsyncKalshiClient wired to the demo base URL (matches wire-shape test mocks)."""
-    from kalshi.config import DEMO_BASE_URL
+    from kalshi.config import DEMO_BASE_URL, DEMO_WS_URL
 
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return AsyncKalshiClient(auth=test_auth, config=cfg)
 
 

tests/test_client.py

@@ -522,11 +522,12 @@ def test_base_url_override(self, test_auth: KalshiAuth) -> None:
         assert client._config.base_url == custom
         client.close()
 
-    def test_base_url_takes_precedence_over_demo(self, test_auth: KalshiAuth) -> None:
+    def test_demo_with_non_demo_base_url_rejected(self, test_auth: KalshiAuth) -> None:
+        # #239: demo=True + an explicit non-demo base_url used to silently produce
+        # a split REST/WS env (real-money REST + demo WS feed). Now rejected.
         custom = "https://custom.api.com/trade-api/v2"
-        client = KalshiClient(auth=test_auth, base_url=custom, demo=True)
-        assert client._config.base_url == custom
-        client.close()
+        with pytest.raises(ValueError, match="demo=True"):
+            KalshiClient(auth=test_auth, base_url=custom, demo=True)
 
     def test_default_production_url(self, test_auth: KalshiAuth) -> None:
         client = KalshiClient(auth=test_auth)

tests/test_communications.py

@@ -14,7 +14,7 @@
 from kalshi.async_client import AsyncKalshiClient
 from kalshi.auth import KalshiAuth
 from kalshi.client import KalshiClient
-from kalshi.config import DEMO_BASE_URL, KalshiConfig
+from kalshi.config import DEMO_BASE_URL, DEMO_WS_URL, KalshiConfig
 from kalshi.errors import (
     AuthRequiredError,
     KalshiNotFoundError,
@@ -61,13 +61,13 @@ def async_comms(
 
 @pytest.fixture
 def client(test_auth: KalshiAuth) -> KalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return KalshiClient(auth=test_auth, config=cfg)
 
 
 @pytest.fixture
 def async_client(test_auth: KalshiAuth) -> AsyncKalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return AsyncKalshiClient(auth=test_auth, config=cfg)
 
 

tests/test_config.py

@@ -29,11 +29,18 @@ class TestTrailingSlashStripping:
     """F-Q-05: __post_init__ rstrips trailing slashes on base_url and ws_base_url."""
 
     def test_trailing_slash_stripped_on_base_url(self) -> None:
-        config = KalshiConfig(base_url="https://demo-api.kalshi.co/trade-api/v2/")
+        # Pair with matching demo ws_base_url to satisfy #239 split-env check.
+        config = KalshiConfig(
+            base_url="https://demo-api.kalshi.co/trade-api/v2/",
+            ws_base_url=DEMO_WS_URL,
+        )
         assert config.base_url == "https://demo-api.kalshi.co/trade-api/v2"
 
     def test_trailing_slash_stripped_on_ws_base_url(self) -> None:
-        config = KalshiConfig(ws_base_url="wss://demo-api.kalshi.co/trade-api/ws/v2/")
+        config = KalshiConfig(
+            base_url=DEMO_BASE_URL,
+            ws_base_url="wss://demo-api.kalshi.co/trade-api/ws/v2/",
+        )
         assert config.ws_base_url == "wss://demo-api.kalshi.co/trade-api/ws/v2"
 
     def test_multiple_trailing_slashes_all_stripped(self) -> None:
@@ -63,7 +70,10 @@ def test_demo_classmethod_url_has_no_trailing_slash(self) -> None:
     def test_trailing_slash_base_url_still_passes_validation(self) -> None:
         # Regression: stripping happens before _validate_url, so a known-host URL
         # with a trailing slash must not trip the validator.
-        config = KalshiConfig(base_url="https://demo-api.kalshi.co/trade-api/v2/")
+        config = KalshiConfig(
+            base_url="https://demo-api.kalshi.co/trade-api/v2/",
+            ws_base_url=DEMO_WS_URL,
+        )
         assert config.base_url == DEMO_BASE_URL
 
 
@@ -76,6 +86,7 @@ def test_signed_get_with_trailing_slash_base_no_double_slash(
     ) -> None:
         config = KalshiConfig(
             base_url="https://demo-api.kalshi.co/trade-api/v2/",
+            ws_base_url=DEMO_WS_URL,
             timeout=5.0,
             max_retries=0,
         )
@@ -103,6 +114,7 @@ class TestExtraHeadersForwarding:
     def test_extra_headers_forwarded_to_request(self, test_auth: KalshiAuth) -> None:
         config = KalshiConfig(
             base_url="https://demo-api.kalshi.co/trade-api/v2",
+            ws_base_url=DEMO_WS_URL,
             timeout=5.0,
             max_retries=0,
             extra_headers={
@@ -136,6 +148,7 @@ def test_extra_headers_persist_across_multiple_requests(
         # carries them — not just the first one.
         config = KalshiConfig(
             base_url="https://demo-api.kalshi.co/trade-api/v2",
+            ws_base_url=DEMO_WS_URL,
             timeout=5.0,
             max_retries=0,
             extra_headers={"X-Trace-Id": "trace-1"},
@@ -211,12 +224,18 @@ def test_base_url_without_trade_api_v2_raises(self) -> None:
             KalshiConfig(base_url="https://demo-api.kalshi.co/trade-api")
 
     def test_base_url_with_trade_api_v2_accepted(self) -> None:
-        config = KalshiConfig(base_url="https://demo-api.kalshi.co/trade-api/v2")
+        config = KalshiConfig(
+            base_url="https://demo-api.kalshi.co/trade-api/v2",
+            ws_base_url=DEMO_WS_URL,
+        )
         assert config.base_url == "https://demo-api.kalshi.co/trade-api/v2"
 
     def test_base_url_with_trailing_slash_accepted(self) -> None:
         # Trailing slash is stripped before path validation.
-        config = KalshiConfig(base_url="https://demo-api.kalshi.co/trade-api/v2/")
+        config = KalshiConfig(
+            base_url="https://demo-api.kalshi.co/trade-api/v2/",
+            ws_base_url=DEMO_WS_URL,
+        )
         assert config.base_url == "https://demo-api.kalshi.co/trade-api/v2"
 
 

tests/test_order_groups.py

@@ -14,7 +14,7 @@
 from kalshi.async_client import AsyncKalshiClient
 from kalshi.auth import KalshiAuth
 from kalshi.client import KalshiClient
-from kalshi.config import DEMO_BASE_URL, KalshiConfig
+from kalshi.config import DEMO_BASE_URL, DEMO_WS_URL, KalshiConfig
 from kalshi.errors import (
     AuthRequiredError,
     KalshiNotFoundError,
@@ -60,13 +60,13 @@ def async_order_groups(
 
 @pytest.fixture
 def client(test_auth: KalshiAuth) -> KalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return KalshiClient(auth=test_auth, config=cfg)
 
 
 @pytest.fixture
 def async_client(test_auth: KalshiAuth) -> AsyncKalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return AsyncKalshiClient(auth=test_auth, config=cfg)
 
 

tests/test_orders.py

@@ -50,9 +50,9 @@ def orders(test_auth: KalshiAuth, config: KalshiConfig) -> OrdersResource:
 @pytest.fixture
 def client(test_auth: KalshiAuth) -> KalshiClient:
     """KalshiClient wired to the demo base URL (matches wire-shape test mocks)."""
-    from kalshi.config import DEMO_BASE_URL
+    from kalshi.config import DEMO_BASE_URL, DEMO_WS_URL
 
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return KalshiClient(auth=test_auth, config=cfg)
 
 

tests/test_split_env.py

@@ -0,0 +1,125 @@
+"""Regression tests for #239: split REST/WS environment rejection.
+
+If ``demo=True`` was combined with an explicit production ``base_url`` (or
+``KALSHI_DEMO=true`` with ``KALSHI_API_BASE_URL=<prod>``), the old
+``setdefault`` logic in the client constructors silently honored ``base_url``
+while still pinning ``ws_base_url`` to the demo WS feed — REST hit production
+(real money) while a WS-driven strategy made decisions against a demo book.
+``KalshiConfig`` itself never cross-checked that REST and WS resolved to the
+same Kalshi environment.
+
+These tests pin down the new contract:
+
+* ``KalshiConfig.__post_init__`` rejects a base_url/ws_base_url pair whose
+  hosts resolve to different known Kalshi environments (prod vs demo).
+* ``KalshiClient`` / ``AsyncKalshiClient`` constructors reject
+  ``demo=True`` combined with an explicit non-demo ``base_url`` (and the
+  ``from_env`` env-var equivalent) before building the config.
+* Localhost on either side is fine (mock servers); both-prod and both-demo
+  remain valid.
+"""
+
+from __future__ import annotations
+
+import pytest
+
+from kalshi.async_client import AsyncKalshiClient
+from kalshi.client import KalshiClient
+from kalshi.config import (
+    DEMO_BASE_URL,
+    DEMO_WS_URL,
+    PRODUCTION_BASE_URL,
+    PRODUCTION_WS_URL,
+    KalshiConfig,
+)
+
+
+class TestKalshiConfigSplitEnv:
+    """KalshiConfig cross-check of base_url vs ws_base_url environment."""
+
+    def test_prod_base_demo_ws_rejected(self) -> None:
+        with pytest.raises(ValueError, match="split REST/WS environment"):
+            KalshiConfig(base_url=PRODUCTION_BASE_URL, ws_base_url=DEMO_WS_URL)
+
+    def test_demo_base_prod_ws_rejected(self) -> None:
+        with pytest.raises(ValueError, match="split REST/WS environment"):
+            KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=PRODUCTION_WS_URL)
+
+    def test_both_production_ok(self) -> None:
+        config = KalshiConfig(
+            base_url=PRODUCTION_BASE_URL, ws_base_url=PRODUCTION_WS_URL
+        )
+        assert config.base_url == PRODUCTION_BASE_URL
+        assert config.ws_base_url == PRODUCTION_WS_URL
+
+    def test_both_demo_ok(self) -> None:
+        config = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL)
+        assert config.base_url == DEMO_BASE_URL
+        assert config.ws_base_url == DEMO_WS_URL
+
+    def test_localhost_base_demo_ws_ok(self) -> None:
+        # Mock REST server + real demo WS: legitimate dev setup, not a split env.
+        config = KalshiConfig(
+            base_url="http://localhost:8080/trade-api/v2",
+            ws_base_url=DEMO_WS_URL,
+        )
+        assert config.ws_base_url == DEMO_WS_URL
+
+    def test_prod_base_localhost_ws_ok(self) -> None:
+        # Real REST + mock WS server: also legitimate; not a known-env mismatch.
+        config = KalshiConfig(
+            base_url=PRODUCTION_BASE_URL,
+            ws_base_url="ws://localhost:8080/trade-api/ws/v2",
+        )
+        assert config.base_url == PRODUCTION_BASE_URL
+
+
+class TestKalshiClientSplitEnv:
+    """Sync client rejects demo=True paired with a non-demo base_url."""
+
+    def test_demo_true_with_prod_base_url_raises(self) -> None:
+        with pytest.raises(ValueError, match="demo=True"):
+            KalshiClient(demo=True, base_url=PRODUCTION_BASE_URL)
+
+    def test_demo_true_with_demo_base_url_ok(self) -> None:
+        # Redundant but consistent — must not raise.
+        client = KalshiClient(demo=True, base_url=DEMO_BASE_URL)
+        assert client._config.base_url == DEMO_BASE_URL
+        assert client._config.ws_base_url == DEMO_WS_URL
+        client.close()
+
+    def test_demo_false_with_demo_base_url_raises_via_config(self) -> None:
+        # demo=False (default) + demo REST URL leaves ws_base_url pointing at
+        # production. The config-level cross-check catches the resulting split.
+        with pytest.raises(ValueError, match="split REST/WS environment"):
+            KalshiClient(base_url=DEMO_BASE_URL)
+
+    def test_from_env_demo_plus_prod_base_url_raises(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        monkeypatch.delenv("KALSHI_KEY_ID", raising=False)
+        monkeypatch.delenv("KALSHI_PRIVATE_KEY", raising=False)
+        monkeypatch.delenv("KALSHI_PRIVATE_KEY_PATH", raising=False)
+        monkeypatch.setenv("KALSHI_DEMO", "true")
+        monkeypatch.setenv("KALSHI_API_BASE_URL", PRODUCTION_BASE_URL)
+        with pytest.raises(ValueError, match="demo=True"):
+            KalshiClient.from_env()
+
+
+class TestAsyncKalshiClientSplitEnv:
+    """Async client mirrors the sync rejection."""
+
+    def test_demo_true_with_prod_base_url_raises(self) -> None:
+        with pytest.raises(ValueError, match="demo=True"):
+            AsyncKalshiClient(demo=True, base_url=PRODUCTION_BASE_URL)
+
+    def test_from_env_demo_plus_prod_base_url_raises(
+        self, monkeypatch: pytest.MonkeyPatch
+    ) -> None:
+        monkeypatch.delenv("KALSHI_KEY_ID", raising=False)
+        monkeypatch.delenv("KALSHI_PRIVATE_KEY", raising=False)
+        monkeypatch.delenv("KALSHI_PRIVATE_KEY_PATH", raising=False)
+        monkeypatch.setenv("KALSHI_DEMO", "true")
+        monkeypatch.setenv("KALSHI_API_BASE_URL", PRODUCTION_BASE_URL)
+        with pytest.raises(ValueError, match="demo=True"):
+            AsyncKalshiClient.from_env()

tests/test_subaccounts.py

@@ -14,7 +14,7 @@
 from kalshi.async_client import AsyncKalshiClient
 from kalshi.auth import KalshiAuth
 from kalshi.client import KalshiClient
-from kalshi.config import DEMO_BASE_URL, KalshiConfig
+from kalshi.config import DEMO_BASE_URL, DEMO_WS_URL, KalshiConfig
 from kalshi.errors import (
     AuthRequiredError,
     KalshiServerError,
@@ -59,13 +59,13 @@ def async_subaccounts(
 
 @pytest.fixture
 def client(test_auth: KalshiAuth) -> KalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return KalshiClient(auth=test_auth, config=cfg)
 
 
 @pytest.fixture
 def async_client(test_auth: KalshiAuth) -> AsyncKalshiClient:
-    cfg = KalshiConfig(base_url=DEMO_BASE_URL, timeout=5.0, max_retries=0)
+    cfg = KalshiConfig(base_url=DEMO_BASE_URL, ws_base_url=DEMO_WS_URL, timeout=5.0, max_retries=0)
     return AsyncKalshiClient(auth=test_auth, config=cfg)