diff --git a/libs/checkpoint-postgres/langgraph/store/postgres/aio.py b/libs/checkpoint-postgres/langgraph/store/postgres/aio.py
index d8fd53d96..2a6d5b47c 100644
--- a/libs/checkpoint-postgres/langgraph/store/postgres/aio.py
+++ b/libs/checkpoint-postgres/langgraph/store/postgres/aio.py
@@ -115,6 +115,20 @@ class AsyncPostgresStore(AsyncBatchedBaseStore, BasePostgresStore[_ainternal.Con
         If you provide a TTL configuration, you must explicitly call `start_ttl_sweeper()` to begin
         the background task that removes expired items. Call `stop_ttl_sweeper()` to properly
         clean up resources when you're done with the store.
+
+    Note:
+        The core data operations -- `put`/`aput`, `get`/`aget`, `search`/`asearch`,
+        `delete`/`adelete`, and `list_namespaces`/`alist_namespaces` -- are inherited
+        from `langgraph.store.base.BaseStore`, which is the canonical reference for
+        their arguments and behavior. (This is LangGraph's `BaseStore`, distinct from
+        `langchain_core.stores.BaseStore`.) Key semantics:
+
+        - `put`/`aput` `value` must be a `dict` of JSON-serializable data. `None` is
+            not a valid stored value: a top-level `None` is reserved as the delete
+            signal (prefer `delete`/`adelete`). To store a marker or "empty" entry,
+            use an empty dict (`{}`), not `None`.
+        - `list_namespaces`/`alist_namespaces` match `prefix`/`suffix` exactly and
+            case-sensitively; there is no case-insensitive matching option.
     """
 
     __slots__ = (
diff --git a/libs/checkpoint-postgres/langgraph/store/postgres/base.py b/libs/checkpoint-postgres/langgraph/store/postgres/base.py
index 0d1cdc8dc..a974b8ed4 100644
--- a/libs/checkpoint-postgres/langgraph/store/postgres/base.py
+++ b/libs/checkpoint-postgres/langgraph/store/postgres/base.py
@@ -713,6 +713,20 @@ class PostgresStore(BaseStore, BasePostgresStore[_pg_internal.Conn]):
         the background thread that removes expired items. Call `stop_ttl_sweeper()` to properly
         clean up resources when you're done with the store.
 
+    Note:
+        The core data operations -- `put`/`aput`, `get`/`aget`, `search`/`asearch`,
+        `delete`/`adelete`, and `list_namespaces`/`alist_namespaces` -- are inherited
+        from `langgraph.store.base.BaseStore`, which is the canonical reference for
+        their arguments and behavior. (This is LangGraph's `BaseStore`, distinct from
+        `langchain_core.stores.BaseStore`.) Key semantics:
+
+        - `put`/`aput` `value` must be a `dict` of JSON-serializable data. `None` is
+            not a valid stored value: a top-level `None` is reserved as the delete
+            signal (prefer `delete`/`adelete`). To store a marker or "empty" entry,
+            use an empty dict (`{}`), not `None`.
+        - `list_namespaces`/`alist_namespaces` match `prefix`/`suffix` exactly and
+            case-sensitively; there is no case-insensitive matching option.
+
     """
 
     __slots__ = (
diff --git a/libs/checkpoint/langgraph/store/base/__init__.py b/libs/checkpoint/langgraph/store/base/__init__.py
index 5b04fb51d..282a8e08a 100644
--- a/libs/checkpoint/langgraph/store/base/__init__.py
+++ b/libs/checkpoint/langgraph/store/base/__init__.py
@@ -861,8 +861,11 @@ class BaseStore(ABC):
                 Example: `("documents", "user123")`
             key: Unique identifier within the namespace. Together with namespace forms
                 the complete path to the item.
-            value: Dictionary containing the item's data. Must contain string keys
-                and JSON-serializable values.
+            value: Dictionary containing the item's data. Must be a `dict` with
+                string keys and JSON-serializable values. `None` is not a valid
+                stored value: a top-level `None` is reserved as the delete signal
+                (prefer `delete()`). To store a marker or "empty" entry, use an
+                empty dict (`{}`), not `None`.
             index: Controls how the item's fields are indexed for search:
 
                 - None (default): Use `fields` you configured when creating the store (if any)
@@ -895,6 +898,13 @@ class BaseStore(ABC):
             store.put(("docs",), "report", {"memory": "Will likes ai"})
             ```
 
+            Store a set/list-like marker entry. Use an empty dict, not `None`
+            (which would delete the item):
+
+            ```python
+            store.put(("seen",), "user123", {})
+            ```
+
             Do not index item for semantic search. Still accessible through `get()`
             and `search()` operations but won't have a vector representation.
 
@@ -950,8 +960,10 @@ class BaseStore(ABC):
         find specific collections, or navigate the namespace hierarchy.
 
         Args:
-            prefix: Filter namespaces that start with this path.
-            suffix: Filter namespaces that end with this path.
+            prefix: Filter namespaces that start with this path. Matched exactly and
+                case-sensitively.
+            suffix: Filter namespaces that end with this path. Matched exactly and
+                case-sensitively.
             max_depth: Return namespaces up to this depth in the hierarchy.
                 Namespaces deeper than this level will be truncated.
             limit: Maximum number of namespaces to return.
@@ -961,6 +973,11 @@ class BaseStore(ABC):
             A list of namespace tuples that match the criteria. Each tuple represents a
                 full namespace path up to `max_depth`.
 
+        Note:
+            Namespace matching is case-sensitive. There is no case-insensitive
+            matching option. If you need case-insensitive lookups, normalize the
+            namespace casing when you write items (e.g. lowercase each label).
+
         ???+ example "Examples":
 
             Setting `max_depth=3`. Given the namespaces:
@@ -1114,8 +1131,11 @@ class BaseStore(ABC):
                 Example: `("documents", "user123")`
             key: Unique identifier within the namespace. Together with namespace forms
                 the complete path to the item.
-            value: Dictionary containing the item's data. Must contain string keys
-                and JSON-serializable values.
+            value: Dictionary containing the item's data. Must be a `dict` with
+                string keys and JSON-serializable values. `None` is not a valid
+                stored value: a top-level `None` is reserved as the delete signal
+                (prefer `adelete()`). To store a marker or "empty" entry, use an
+                empty dict (`{}`), not `None`.
             index: Controls how the item's fields are indexed for search:
 
                 - None (default): Use `fields` you configured when creating the store (if any)
@@ -1211,8 +1231,10 @@ class BaseStore(ABC):
         find specific collections, or navigate the namespace hierarchy.
 
         Args:
-            prefix: Filter namespaces that start with this path.
-            suffix: Filter namespaces that end with this path.
+            prefix: Filter namespaces that start with this path. Matched exactly and
+                case-sensitively.
+            suffix: Filter namespaces that end with this path. Matched exactly and
+                case-sensitively.
             max_depth: Return namespaces up to this depth in the hierarchy.
                 Namespaces deeper than this level will be truncated to this depth.
             limit: Maximum number of namespaces to return.
@@ -1222,6 +1244,11 @@ class BaseStore(ABC):
             A list of namespace tuples that match the criteria. Each tuple represents a
                 full namespace path up to `max_depth`.
 
+        Note:
+            Namespace matching is case-sensitive. There is no case-insensitive
+            matching option. If you need case-insensitive lookups, normalize the
+            namespace casing when you write items (e.g. lowercase each label).
+
         ???+ example "Examples"
 
             Setting `max_depth=3` with existing namespaces:
diff --git a/libs/checkpoint/langgraph/store/base/batch.py b/libs/checkpoint/langgraph/store/base/batch.py
index 64019d68f..1aed8d466 100644
--- a/libs/checkpoint/langgraph/store/base/batch.py
+++ b/libs/checkpoint/langgraph/store/base/batch.py
@@ -86,6 +86,10 @@ class AsyncBatchedBaseStore(BaseStore):
         *,
         refresh_ttl: bool | None = None,
     ) -> Item | None:
+        """Asynchronously retrieve a single item.
+
+        See `BaseStore.aget` for the full description of arguments and behavior.
+        """
         self._ensure_task()
         fut = self._loop.create_future()
         self._aqueue.put_nowait(
@@ -111,6 +115,10 @@ class AsyncBatchedBaseStore(BaseStore):
         offset: int = 0,
         refresh_ttl: bool | None = None,
     ) -> list[SearchItem]:
+        """Asynchronously search for items within a namespace prefix.
+
+        See `BaseStore.asearch` for the full description of arguments and behavior.
+        """
         self._ensure_task()
         fut = self._loop.create_future()
         self._aqueue.put_nowait(
@@ -137,6 +145,12 @@ class AsyncBatchedBaseStore(BaseStore):
         *,
         ttl: float | None | NotProvided = NOT_PROVIDED,
     ) -> None:
+        """Asynchronously store or update an item.
+
+        `value` must be a `dict`; a top-level `None` is reserved as the delete
+        signal (prefer `adelete`). See `BaseStore.aput` for the full description
+        of arguments and behavior.
+        """
         self._ensure_task()
         _validate_namespace(namespace)
         fut = self._loop.create_future()
@@ -155,6 +169,10 @@ class AsyncBatchedBaseStore(BaseStore):
         namespace: tuple[str, ...],
         key: str,
     ) -> None:
+        """Asynchronously delete an item.
+
+        See `BaseStore.adelete` for the full description of arguments and behavior.
+        """
         self._ensure_task()
         fut = self._loop.create_future()
         self._aqueue.put_nowait((fut, PutOp(namespace, key, None)))
@@ -169,6 +187,11 @@ class AsyncBatchedBaseStore(BaseStore):
         limit: int = 100,
         offset: int = 0,
     ) -> list[tuple[str, ...]]:
+        """Asynchronously list and filter namespaces in the store.
+
+        Namespace matching is case-sensitive. See `BaseStore.alist_namespaces`
+        for the full description of arguments and behavior.
+        """
         self._ensure_task()
         fut = self._loop.create_future()
         match_conditions = []
@@ -188,6 +211,10 @@ class AsyncBatchedBaseStore(BaseStore):
 
     @_check_loop
     def batch(self, ops: Iterable[Op]) -> list[Result]:
+        """Execute multiple operations synchronously in a single batch.
+
+        See `BaseStore.batch` for the full description of arguments and behavior.
+        """
         return asyncio.run_coroutine_threadsafe(self.abatch(ops), self._loop).result()
 
     @_check_loop
@@ -198,6 +225,10 @@ class AsyncBatchedBaseStore(BaseStore):
         *,
         refresh_ttl: bool | None = None,
     ) -> Item | None:
+        """Retrieve a single item.
+
+        See `BaseStore.get` for the full description of arguments and behavior.
+        """
         return asyncio.run_coroutine_threadsafe(
             self.aget(namespace, key=key, refresh_ttl=refresh_ttl), self._loop
         ).result()
@@ -214,6 +245,10 @@ class AsyncBatchedBaseStore(BaseStore):
         offset: int = 0,
         refresh_ttl: bool | None = None,
     ) -> list[SearchItem]:
+        """Search for items within a namespace prefix.
+
+        See `BaseStore.search` for the full description of arguments and behavior.
+        """
         return asyncio.run_coroutine_threadsafe(
             self.asearch(
                 namespace_prefix,
@@ -236,6 +271,12 @@ class AsyncBatchedBaseStore(BaseStore):
         *,
         ttl: float | None | NotProvided = NOT_PROVIDED,
     ) -> None:
+        """Store or update an item.
+
+        `value` must be a `dict`; a top-level `None` is reserved as the delete
+        signal (prefer `delete`). See `BaseStore.put` for the full description of
+        arguments and behavior.
+        """
         _validate_namespace(namespace)
         asyncio.run_coroutine_threadsafe(
             self.aput(