diff --git a/ui/litellm-dashboard/src/components/add_model/ContextWindowEscalationConfig.tsx b/ui/litellm-dashboard/src/components/add_model/ContextWindowEscalationConfig.tsx
index 7271750aadc..c0a65076d20 100644
--- a/ui/litellm-dashboard/src/components/add_model/ContextWindowEscalationConfig.tsx
+++ b/ui/litellm-dashboard/src/components/add_model/ContextWindowEscalationConfig.tsx
@@ -8,13 +8,16 @@ const ContextWindowEscalationConfig: React.FC<{
   onChange: (value: ComplexityRouterConfigValue) => void;
 }> = ({ value, onChange }) => {
   const enabled = value.enable_context_window_escalation ?? true;
+  // A number input renders Number("0.") as "0", so a decimal cannot be typed without a local draft.
   const [bufferDraft, setBufferDraft] = React.useState<string | null>(null);
-  // min/max are inert on a text input, and a plain number input renders Number("0.") as "0" so a
-  // decimal cannot be typed. Hence the local draft plus an explicit clamp on commit.
   const commitBuffer = (raw: string) => {
     setBufferDraft(null);
+    if (raw.trim() === "") {
+      onChange({ ...value, context_window_escalation_buffer: undefined });
+      return;
+    }
     const parsed = Number(raw);
-    if (raw.trim() === "" || !Number.isFinite(parsed)) return;
+    if (!Number.isFinite(parsed)) return;
     onChange({ ...value, context_window_escalation_buffer: Math.min(1, Math.max(0.01, parsed)) });
   };
   return (
diff --git a/ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.test.tsx b/ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.test.tsx
index e08952d5889..71b454dbb06 100644
--- a/ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.test.tsx
+++ b/ui/litellm-dashboard/src/components/add_model/add_auto_router_tab.test.tsx
@@ -394,8 +394,6 @@ describe("AddAutoRouterTab", () => {
     });
   });
 
-  // A plain number input renders Number("1.5") fine but the clamp is ours: values above 1 must commit as 1,
-  // and an untouched buffer must stay out of the payload so the router tracks the backend default.
   it("clamps the context-window buffer to 1 and keeps an untouched buffer out of the payload", async () => {
     const user = userEvent.setup();
     vi.mocked(getMissingTiersError).mockReturnValue(null);
@@ -417,6 +415,29 @@ describe("AddAutoRouterTab", () => {
     expect(config).not.toHaveProperty("enable_context_window_escalation");
   });
 
+  it("clearing the buffer removes it from the payload so the router tracks the backend default", async () => {
+    const user = userEvent.setup();
+    vi.mocked(getMissingTiersError).mockReturnValue(null);
+
+    renderWithProviders(<Harness />);
+
+    await user.type(screen.getByPlaceholderText(/smart_router/i), "ctx-clear-router");
+    expandDetailedConfiguration();
+    await user.click(screen.getByText("Advanced: Context Window Escalation"));
+    const buffer = await screen.findByLabelText("Window fit buffer");
+    fireEvent.change(buffer, { target: { value: "0.8" } });
+    fireEvent.blur(buffer, { target: { value: "0.8" } });
+    fireEvent.change(buffer, { target: { value: "" } });
+    fireEvent.blur(buffer, { target: { value: "" } });
+
+    await user.click(screen.getByRole("button", { name: /add auto router/i }));
+
+    await waitFor(() => expect(handleAddAutoRouterSubmit).toHaveBeenCalled());
+    expect(vi.mocked(handleAddAutoRouterSubmit).mock.calls.at(-1)?.[0].complexity_router_config).not.toHaveProperty(
+      "context_window_escalation_buffer",
+    );
+  });
+
   // The scalar floor is the one scorer knob with no group dict behind it, so its wiring into the create
   // payload is only proven end to end. 0 is the case a truthy check would silently drop.
   it("carries a reasoning override floor of 0 through to the create payload", async () => {
diff --git a/ui/litellm-dashboard/src/components/add_model/build_complexity_router_config.test.ts b/ui/litellm-dashboard/src/components/add_model/build_complexity_router_config.test.ts
index 159fdf957e4..feddaaa0eac 100644
--- a/ui/litellm-dashboard/src/components/add_model/build_complexity_router_config.test.ts
+++ b/ui/litellm-dashboard/src/components/add_model/build_complexity_router_config.test.ts
@@ -59,8 +59,6 @@ describe("buildComplexityRouterConfig", () => {
     expect(config).toEqual(expected);
   });
 
-  // False is the value a truthy guard would silently drop, and it is the whole point of the toggle:
-  // an untouched form tracks the backend default (enabled), an explicit false is a real opt-out.
   it("carries an explicit context-window escalation opt-out and buffer, false included", () => {
     const config = buildComplexityRouterConfig({
       ...baseParams,
diff --git a/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts b/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
index 506411bb7da..f14d6279e32 100644
--- a/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
+++ b/ui/litellm-dashboard/src/lib/autorouter_presets.test.ts
@@ -573,8 +573,6 @@ describe("autorouter_presets", () => {
       expect(prefill.escalationKeywords).toEqual([]);
     });
 
-    // The prefill mapping is a hand-written field list, so a new config key is silently dropped
-    // unless mapped; false is the value a `||` default would erase (the #38453 class).
     it("carries a preset's context-window escalation opt-out and buffer through the prefill", () => {
       const prefill = buildPresetPrefill(
         {