diff --git a/ui/litellm-dashboard/src/components/settings.test.tsx b/ui/litellm-dashboard/src/components/settings.test.tsx
index 9b67657dbca..280bffd8fe9 100644
--- a/ui/litellm-dashboard/src/components/settings.test.tsx
+++ b/ui/litellm-dashboard/src/components/settings.test.tsx
@@ -439,6 +439,40 @@ describe("Settings", () => {
     });
   });
 
+  it("should post the saved s3_v2 folder partitioning when unchanged", async () => {
+    mockS3Callback({ S3_LOG_PROMPTS_ONLY: null, S3_PARTITION_GRANULARITY: "hour" }, "s3_v2");
+    const user = await openS3EditModal("s3_v2");
+
+    const dialog = screen.getByRole("dialog");
+    const partitioning = await within(dialog).findByRole("combobox", { name: "Folder Partitioning" });
+    expect(partitioning).toHaveTextContent("hour");
+
+    await user.click(await within(dialog).findByRole("button", { name: "Save Changes" }));
+    await waitFor(() => {
+      expect(vi.mocked(setCallbacksCall)).toHaveBeenCalledTimes(1);
+    });
+    const [, payload] = vi.mocked(setCallbacksCall).mock.calls[0];
+    expect(payload.environment_variables.s3_partition_granularity).toBe("hour");
+  });
+
+  it("should leave an unset s3_v2 folder partitioning out of the save payload", async () => {
+    mockS3Callback({ S3_LOG_PROMPTS_ONLY: null, S3_PARTITION_GRANULARITY: null }, "s3_v2");
+    const user = await openS3EditModal("s3_v2");
+
+    const dialog = screen.getByRole("dialog");
+    const partitioning = await within(dialog).findByRole("combobox", { name: "Folder Partitioning" });
+    expect(partitioning).toHaveTextContent("Select folder partitioning");
+    expect(partitioning).not.toHaveTextContent(/day|hour/i);
+
+    await user.click(await within(dialog).findByRole("button", { name: "Save Changes" }));
+    await waitFor(() => {
+      expect(vi.mocked(setCallbacksCall)).toHaveBeenCalledTimes(1);
+    });
+    const [, payload] = vi.mocked(setCallbacksCall).mock.calls[0];
+    expect(Object.keys(payload.environment_variables)).not.toContain("s3_partition_granularity");
+    expect(payload.environment_variables.callback).toBe("s3_v2");
+  });
+
   it("should not offer folder partitioning for the legacy s3 callback, which cannot honour it", async () => {
     mockS3Callback({ S3_LOG_PROMPTS_ONLY: null, S3_PARTITION_GRANULARITY: null });
     const user = await openS3EditModal();
diff --git a/ui/litellm-dashboard/src/components/settings.tsx b/ui/litellm-dashboard/src/components/settings.tsx
index e376d858df8..7b08c53df87 100644
--- a/ui/litellm-dashboard/src/components/settings.tsx
+++ b/ui/litellm-dashboard/src/components/settings.tsx
@@ -285,7 +285,7 @@ const getDynamicParamsForCallback = (
 // Shared helper function to build callback payload
 const buildCallbackPayload = (formValues: Record<string, any>, callbackName: string) => {
   return {
-    environment_variables: formValues,
+    environment_variables: Object.fromEntries(Object.entries(formValues).filter(([, value]) => value !== undefined)),
     litellm_settings: {
       success_callback: [callbackName],
     },
@@ -348,8 +348,15 @@ const Settings: React.FC<SettingsPageProps> = ({ accessToken, userRole, userID,
       );
       const fieldNameFor = (variable: string) =>
         params.find((param) => param.toUpperCase() === variable.toUpperCase()) ?? variable;
+      const callbackConfig = findCallbackConfig(callbackConfigs, selectedEditCallback.name);
       const normalized = Object.fromEntries(
-        Object.entries(selectedEditCallback.variables || {}).map(([k, v]) => [fieldNameFor(k), v ?? ""]),
+        Object.entries(selectedEditCallback.variables || {}).flatMap(([key, value]) => {
+          const fieldName = fieldNameFor(key);
+          if (value == null && callbackConfig?.dynamic_params?.[fieldName]?.type === "select") {
+            return [];
+          }
+          return [[fieldName, value ?? ""]];
+        }),
       );
       editForm.reset({
         ...normalized,