diff --git a/sdk/python/src/memoria/_http.py b/sdk/python/src/memoria/_http.py
index 5cb590af..a460791d 100644
--- a/sdk/python/src/memoria/_http.py
+++ b/sdk/python/src/memoria/_http.py
@@ -115,7 +115,7 @@ def _map_error(resp: httpx.Response) -> MemoriaAPIError:
 
 def _backoff(attempt: int) -> float:
     """Exponential backoff: 0.5s, 1s, 2s, …"""
-    return 0.5 * (2 ** attempt)
+    return 0.5 * float(2**attempt)
 
 
 class _HttpTransport:
diff --git a/sdk/python/src/memoria/resources/branches.py b/sdk/python/src/memoria/resources/branches.py
index 1d1a81cc..87d95839 100644
--- a/sdk/python/src/memoria/resources/branches.py
+++ b/sdk/python/src/memoria/resources/branches.py
@@ -2,7 +2,8 @@
 
 from __future__ import annotations
 
-from typing import TYPE_CHECKING, Any
+import builtins
+from typing import TYPE_CHECKING, Any, cast
 
 from ..models import ApplyResult, Branch
 
@@ -39,7 +40,7 @@ def checkout(self, name: str) -> None:
 
     def diff(self, name: str) -> dict[str, Any]:
         """Return high-level diff statistics (no pagination)."""
-        return self._client._request("GET", f"/v1/branches/{name}/diff")  # type: ignore[return-value]
+        return cast(dict[str, Any], self._client._request("GET", f"/v1/branches/{name}/diff"))
 
     def diff_items(
         self,
@@ -50,8 +51,9 @@ def diff_items(
     ) -> dict[str, Any]:
         """Return per-entry diff with optional pagination."""
         params = _strip_none({"limit": limit, "cursor": cursor})
-        return self._client._request(  # type: ignore[return-value]
-            "GET", f"/v1/branches/{name}/diff-items", params=params
+        return cast(
+            dict[str, Any],
+            self._client._request("GET", f"/v1/branches/{name}/diff-items", params=params),
         )
 
     def merge(self, name: str, *, strategy: str = "accept") -> None:
@@ -64,10 +66,10 @@ def apply(
         self,
         name: str,
         *,
-        adds: list[str] | None = None,
-        removes: list[str] | None = None,
-        updates: list[dict[str, str]] | None = None,
-        accept_branch_conflicts: list[str] | None = None,
+        adds: builtins.list[str] | None = None,
+        removes: builtins.list[str] | None = None,
+        updates: builtins.list[dict[str, str]] | None = None,
+        accept_branch_conflicts: builtins.list[str] | None = None,
     ) -> ApplyResult:
         body = _strip_none(
             {
@@ -97,8 +99,9 @@ def pick(
                 "dry_run": dry_run,
             }
         )
-        return self._client._request(  # type: ignore[return-value]
-            "POST", f"/v1/branches/{name}/pick", json=body
+        return cast(
+            dict[str, Any],
+            self._client._request("POST", f"/v1/branches/{name}/pick", json=body),
         )
 
 
@@ -125,7 +128,9 @@ async def checkout(self, name: str) -> None:
         await self._client._arequest("POST", f"/v1/branches/{name}/checkout", json={})
 
     async def diff(self, name: str) -> dict[str, Any]:
-        return await self._client._arequest("GET", f"/v1/branches/{name}/diff")  # type: ignore[return-value]
+        return cast(
+            dict[str, Any], await self._client._arequest("GET", f"/v1/branches/{name}/diff")
+        )
 
     async def diff_items(
         self,
@@ -135,8 +140,9 @@ async def diff_items(
         cursor: str | None = None,
     ) -> dict[str, Any]:
         params = _strip_none({"limit": limit, "cursor": cursor})
-        return await self._client._arequest(  # type: ignore[return-value]
-            "GET", f"/v1/branches/{name}/diff-items", params=params
+        return cast(
+            dict[str, Any],
+            await self._client._arequest("GET", f"/v1/branches/{name}/diff-items", params=params),
         )
 
     async def merge(self, name: str, *, strategy: str = "accept") -> None:
@@ -151,10 +157,10 @@ async def apply(
         self,
         name: str,
         *,
-        adds: list[str] | None = None,
-        removes: list[str] | None = None,
-        updates: list[dict[str, str]] | None = None,
-        accept_branch_conflicts: list[str] | None = None,
+        adds: builtins.list[str] | None = None,
+        removes: builtins.list[str] | None = None,
+        updates: builtins.list[dict[str, str]] | None = None,
+        accept_branch_conflicts: builtins.list[str] | None = None,
     ) -> ApplyResult:
         body = _strip_none(
             {
@@ -184,6 +190,7 @@ async def pick(
                 "dry_run": dry_run,
             }
         )
-        return await self._client._arequest(  # type: ignore[return-value]
-            "POST", f"/v1/branches/{name}/pick", json=body
+        return cast(
+            dict[str, Any],
+            await self._client._arequest("POST", f"/v1/branches/{name}/pick", json=body),
         )
diff --git a/sdk/python/src/memoria/resources/memories.py b/sdk/python/src/memoria/resources/memories.py
index 0c1052b5..f6cfb21c 100644
--- a/sdk/python/src/memoria/resources/memories.py
+++ b/sdk/python/src/memoria/resources/memories.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import builtins
 import json
 import math
 from typing import TYPE_CHECKING, Any
@@ -451,7 +452,7 @@ def query(
         *,
         extra_metadata_filter: dict[str, Any] | None = None,
         subject_id: str | None = None,
-        memory_types: list[str] | None = None,
+        memory_types: builtins.list[str] | None = None,
         session_id: str | None = None,
         trust_tier: str | None = None,
         branch: str | None = None,
@@ -533,10 +534,10 @@ def delete(
     def purge(
         self,
         *,
-        memory_ids: list[str] | None = None,
+        memory_ids: builtins.list[str] | None = None,
         topic: str | None = None,
         session_id: str | None = None,
-        memory_types: list[str] | None = None,
+        memory_types: builtins.list[str] | None = None,
         reason: str | None = None,
         branch: str | None = None,
     ) -> PurgeResult:
@@ -746,7 +747,7 @@ async def query(
         *,
         extra_metadata_filter: dict[str, Any] | None = None,
         subject_id: str | None = None,
-        memory_types: list[str] | None = None,
+        memory_types: builtins.list[str] | None = None,
         session_id: str | None = None,
         trust_tier: str | None = None,
         branch: str | None = None,
@@ -828,10 +829,10 @@ async def delete(
     async def purge(
         self,
         *,
-        memory_ids: list[str] | None = None,
+        memory_ids: builtins.list[str] | None = None,
         topic: str | None = None,
         session_id: str | None = None,
-        memory_types: list[str] | None = None,
+        memory_types: builtins.list[str] | None = None,
         reason: str | None = None,
         branch: str | None = None,
     ) -> PurgeResult:
diff --git a/sdk/python/src/memoria/resources/snapshots.py b/sdk/python/src/memoria/resources/snapshots.py
index 7bf2a892..b3cfd292 100644
--- a/sdk/python/src/memoria/resources/snapshots.py
+++ b/sdk/python/src/memoria/resources/snapshots.py
@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import builtins
 from typing import TYPE_CHECKING, Any
 
 from ..exceptions import MemoriaValidationError
@@ -28,10 +29,14 @@ def list(self, *, limit: int = 20, offset: int = 0) -> list[Snapshot]:
         params = {"limit": limit, "offset": offset}
         data = self._client._request("GET", "/v1/snapshots", params=params)
         # Server may return {"snapshots": [...], "has_more": bool} or a plain list
+        # An empty body (204) or a null field would otherwise be iterated as None.
+        items: builtins.list[Any]
         if isinstance(data, dict):
-            items = data.get("snapshots", data.get("items", []))
-        else:
+            items = data.get("snapshots") or data.get("items") or []
+        elif isinstance(data, builtins.list):
             items = data
+        else:
+            items = []
         return [Snapshot.from_dict(s) for s in items]
 
     def rollback(self, name: str) -> None:
@@ -41,7 +46,7 @@ def delete(
         self,
         name: str | None = None,
         *,
-        names: list[str] | None = None,
+        names: builtins.list[str] | None = None,
         prefix: str | None = None,
         older_than: str | None = None,
     ) -> None:
@@ -85,10 +90,14 @@ async def create(self, name: str, *, description: str | None = None) -> Snapshot
     async def list(self, *, limit: int = 20, offset: int = 0) -> list[Snapshot]:
         params = {"limit": limit, "offset": offset}
         data = await self._client._arequest("GET", "/v1/snapshots", params=params)
+        # An empty body (204) or a null field would otherwise be iterated as None.
+        items: builtins.list[Any]
         if isinstance(data, dict):
-            items = data.get("snapshots", data.get("items", []))
-        else:
+            items = data.get("snapshots") or data.get("items") or []
+        elif isinstance(data, builtins.list):
             items = data
+        else:
+            items = []
         return [Snapshot.from_dict(s) for s in items]
 
     async def rollback(self, name: str) -> None:
@@ -98,7 +107,7 @@ async def delete(
         self,
         name: str | None = None,
         *,
-        names: list[str] | None = None,
+        names: builtins.list[str] | None = None,
         prefix: str | None = None,
         older_than: str | None = None,
     ) -> None: