diff --git a/src/agentex/lib/core/clients/temporal/auth.py b/src/agentex/lib/core/clients/temporal/auth.py
index 09886d8d4..7c757b1e4 100644
--- a/src/agentex/lib/core/clients/temporal/auth.py
+++ b/src/agentex/lib/core/clients/temporal/auth.py
@@ -17,6 +17,7 @@
 logger = logging.getLogger(__name__)
 
 _AUTH_SCOPE_ENV = "TEMPORAL_AUTH_SCOPE"
+_NAMESPACE_ENV = "TEMPORAL_NAMESPACE"
 _REFRESH_MARGIN_SECONDS = 300
 _MIN_REFRESH_DELAY_SECONDS = 30
 _RETRY_DELAY_SECONDS = 30
@@ -85,6 +86,10 @@ async def _run(self) -> None:
 
 async def connect_temporal_client(connect_options: dict[str, Any]) -> Client:
     """Connect anonymously by default, or with renewable Workload Identity."""
+    namespace = os.environ.get(_NAMESPACE_ENV)
+    if namespace and "namespace" not in connect_options:
+        connect_options = {**connect_options, "namespace": namespace}
+
     scope = os.environ.get(_AUTH_SCOPE_ENV)
     if not scope:
         return await Client.connect(**connect_options)
diff --git a/tests/lib/test_temporal_auth.py b/tests/lib/test_temporal_auth.py
index 59c7e1bd7..c04c27c52 100644
--- a/tests/lib/test_temporal_auth.py
+++ b/tests/lib/test_temporal_auth.py
@@ -47,6 +47,11 @@ async def close(self):
         self.closed = True
 
 
+@pytest.fixture(autouse=True)
+def _clear_temporal_namespace(monkeypatch):
+    monkeypatch.delenv("TEMPORAL_NAMESPACE", raising=False)
+
+
 async def test_connect_without_scope_preserves_legacy_path(monkeypatch):
     monkeypatch.delenv("TEMPORAL_AUTH_SCOPE", raising=False)
     client = MagicMock()
@@ -63,6 +68,42 @@ async def test_connect_without_scope_preserves_legacy_path(monkeypatch):
     connect.assert_awaited_once_with(target_host="temporal:7233")
 
 
+@pytest.mark.parametrize("scope", [None, _SCOPE])
+async def test_connect_uses_namespace_from_environment(monkeypatch, scope):
+    if scope is None:
+        monkeypatch.delenv("TEMPORAL_AUTH_SCOPE", raising=False)
+    else:
+        monkeypatch.setenv("TEMPORAL_AUTH_SCOPE", scope)
+    monkeypatch.setenv("TEMPORAL_NAMESPACE", "tenant-a")
+
+    with patch(
+        "agentex.lib.core.clients.temporal.auth.WorkloadIdentityCredential",
+        return_value=FakeCredential(AccessToken(_INITIAL, 2_000)),
+    ):
+        with patch(
+            "agentex.lib.core.clients.temporal.auth.Client.connect",
+            new=AsyncMock(return_value=MagicMock()),
+        ) as connect:
+            with patch("agentex.lib.core.clients.temporal.auth.time.time", return_value=1_000):
+                with patch.object(TemporalTokenSession, "start"):
+                    await connect_temporal_client({"target_host": "temporal:7233"})
+
+    assert connect.await_args.kwargs["namespace"] == "tenant-a"
+
+
+async def test_connect_keeps_explicit_namespace(monkeypatch):
+    monkeypatch.delenv("TEMPORAL_AUTH_SCOPE", raising=False)
+    monkeypatch.setenv("TEMPORAL_NAMESPACE", "tenant-a")
+
+    with patch(
+        "agentex.lib.core.clients.temporal.auth.Client.connect",
+        new=AsyncMock(return_value=MagicMock()),
+    ) as connect:
+        await connect_temporal_client({"target_host": "temporal:7233", "namespace": "tenant-b"})
+
+    connect.assert_awaited_once_with(target_host="temporal:7233", namespace="tenant-b")
+
+
 async def test_connect_initial_token_failure_blocks_startup(monkeypatch):
     monkeypatch.setenv("TEMPORAL_AUTH_SCOPE", _SCOPE)
     credential = FakeCredential(RuntimeError("identity unavailable"))