diff --git a/python-sdk/README.md b/python-sdk/README.md
index 4d969cf1..95d8f4ec 100644
--- a/python-sdk/README.md
+++ b/python-sdk/README.md
@@ -267,7 +267,7 @@ state_manager = StateManager(namespace="MyProject")
 
 **Parameters:**
 - `namespace` (str): The namespace for your project
-- `state_manager_uri` (str, optional): The URI of the state manager service. If not provided, reads from `EXOSPHERE_STATE_MANAGER_URI` environment variable
+- `state_manager_uri` (str, optional): The URI of the state manager service. If not provided, reads from `EXOSPHERE_STATE_MANAGER_URI` environment variable. A trailing slash is accepted and ignored (`http://localhost:8000/` and `http://localhost:8000` are equivalent)
 - `key` (str, optional): Your API key. If not provided, reads from `EXOSPHERE_API_KEY` environment variable
 - `state_manager_version` (str): The API version to use (default: "v0")
 
diff --git a/python-sdk/exospherehost/statemanager.py b/python-sdk/exospherehost/statemanager.py
index 13cf6890..5e5749e7 100644
--- a/python-sdk/exospherehost/statemanager.py
+++ b/python-sdk/exospherehost/statemanager.py
@@ -24,6 +24,12 @@ def _set_config_from_env(self):
             self._state_manager_uri = os.environ.get("EXOSPHERE_STATE_MANAGER_URI")
         if self._key is None:
             self._key = os.environ.get("EXOSPHERE_API_KEY")
+        # Normalise once, after the environment fallback, so "http://host:8000/" and
+        # "http://host:8000" build the same endpoints (issue #642). Only trailing
+        # separators go: scheme, authority, port and a deployment prefix are kept, and a
+        # missing URI stays missing.
+        if isinstance(self._state_manager_uri, str):
+            self._state_manager_uri = self._state_manager_uri.rstrip("/")
 
     def _get_trigger_state_endpoint(self, graph_name: str):
         return f"{self._state_manager_uri}/{self._state_manager_version}/namespace/{self._namespace}/graph/{graph_name}/trigger"
diff --git a/python-sdk/tests/test_statemanager_base_uri.py b/python-sdk/tests/test_statemanager_base_uri.py
new file mode 100644
index 00000000..56d96241
--- /dev/null
+++ b/python-sdk/tests/test_statemanager_base_uri.py
@@ -0,0 +1,52 @@
+"""
+Regression for https://github.com/FailproofAI/runtime/issues/642.
+
+A state manager URI configured with a trailing slash ("http://localhost:8000/") produced
+endpoints with a doubled separator ("http://localhost:8000//v0/..."), which some servers
+and proxies reject. The base must be normalised once, after the environment fallback, so
+explicit and environment configuration behave the same and every endpoint helper agrees.
+"""
+import pytest
+
+from exospherehost.statemanager import StateManager
+
+
+BASES = [
+    # (configured base, expected normalised base)
+    ("http://localhost:8000/", "http://localhost:8000"),
+    ("http://localhost:8000", "http://localhost:8000"),
+    ("https://example.test/", "https://example.test"),
+    ("https://example.test/api/", "https://example.test/api"),
+    ("https://example.test/api", "https://example.test/api"),
+    ("http://[::1]:8000/", "http://[::1]:8000"),
+    ("https://example.test///", "https://example.test"),
+]
+
+ENDPOINTS = [
+    ("_get_trigger_state_endpoint", "/v0/namespace/demo/graph/g/trigger"),
+    ("_get_upsert_graph_endpoint", "/v0/namespace/demo/graph/g"),
+    ("_get_get_graph_endpoint", "/v0/namespace/demo/graph/g"),
+]
+
+
+@pytest.mark.parametrize("configured, normalised", BASES)
+@pytest.mark.parametrize("helper, suffix", ENDPOINTS)
+def test_explicit_base_uri_has_one_separator_before_the_version(configured, normalised, helper, suffix):
+    sm = StateManager("demo", state_manager_uri=configured, key="k")
+    assert getattr(sm, helper)("g") == normalised + suffix
+
+
+@pytest.mark.parametrize("configured, normalised", BASES)
+@pytest.mark.parametrize("helper, suffix", ENDPOINTS)
+def test_environment_base_uri_is_normalised_the_same_way(monkeypatch, configured, normalised, helper, suffix):
+    monkeypatch.setenv("EXOSPHERE_STATE_MANAGER_URI", configured)
+    monkeypatch.setenv("EXOSPHERE_API_KEY", "k")
+    sm = StateManager("demo")
+    assert getattr(sm, helper)("g") == normalised + suffix
+
+
+def test_a_missing_base_uri_stays_missing(monkeypatch):
+    # Normalisation must not turn an unset URI into a valid-looking string.
+    monkeypatch.delenv("EXOSPHERE_STATE_MANAGER_URI", raising=False)
+    sm = StateManager("demo", key="k")
+    assert sm._state_manager_uri is None