feat(ui): drive the models page model group filter from ?model_group=

The All Models model-group filter was in-memory React state, so a
filtered view could not be linked to or bookmarked. Deriving it from a
?model_group= query param makes the filter shareable and gives other
pages (for example an organization's model list) a URL to point at

Selecting a group writes the param with history.replaceState so the
filter does not spam browser history; choosing All Model Groups removes
it

ui/litellm-dashboard/src/app/(dashboard)/models-and-endpoints/panels/AllModelsPanel.test.tsx

@@ -0,0 +1,61 @@
+/* @vitest-environment jsdom */
+import { act, render } from "@testing-library/react";
+import { beforeEach, describe, expect, it, vi } from "vitest";
+
+import AllModelsPanel from "./AllModelsPanel";
+
+interface CapturedTabProps {
+  selectedModelGroup: string | null;
+  setSelectedModelGroup: (modelGroup: string) => void;
+}
+
+const captured: { props: CapturedTabProps | null } = { props: null };
+
+vi.mock("@/app/(dashboard)/models-and-endpoints/components/AllModelsTab", () => ({
+  default: (props: CapturedTabProps) => {
+    captured.props = props;
+    return <div data-testid="all-models-tab" />;
+  },
+}));
+vi.mock("@/app/(dashboard)/models-and-endpoints/components/AllModelsTable", () => ({
+  ALL_MODEL_GROUPS_VALUE: "all",
+}));
+vi.mock("@/app/(dashboard)/models-and-endpoints/useModelDashboardData", () => ({
+  useModelDashboardData: () => ({ availableModelGroups: [], availableModelAccessGroups: [] }),
+}));
+vi.mock("next/navigation", () => ({ useSearchParams: () => new URLSearchParams(window.location.search) }));
+
+describe("AllModelsPanel ?model_group= filter", () => {
+  beforeEach(() => {
+    captured.props = null;
+    window.history.pushState(null, "", "/models-and-endpoints/");
+  });
+
+  it("seeds the model group filter from the URL", () => {
+    window.history.pushState(null, "", "/models-and-endpoints/?model_group=gpt-4o");
+    render(<AllModelsPanel />);
+    expect(captured.props?.selectedModelGroup).toBe("gpt-4o");
+  });
+
+  it("defaults to no filter when the param is absent", () => {
+    render(<AllModelsPanel />);
+    expect(captured.props?.selectedModelGroup).toBeNull();
+  });
+
+  it("writes the selected group to the URL via replaceState", () => {
+    render(<AllModelsPanel />);
+    const spy = vi.spyOn(window.history, "replaceState");
+    act(() => captured.props?.setSelectedModelGroup("claude-opus-5"));
+    expect(spy.mock.calls.at(-1)?.[2]).toContain("model_group=claude-opus-5");
+    spy.mockRestore();
+  });
+
+  it("removes the param when the filter resets to all groups", () => {
+    window.history.pushState(null, "", "/models-and-endpoints/?model_group=gpt-4o");
+    render(<AllModelsPanel />);
+    const spy = vi.spyOn(window.history, "replaceState");
+    act(() => captured.props?.setSelectedModelGroup("all"));
+    expect(spy.mock.calls.at(-1)?.[2] as string).not.toContain("model_group");
+    spy.mockRestore();
+  });
+});

ui/litellm-dashboard/src/app/(dashboard)/models-and-endpoints/panels/AllModelsPanel.tsx

@@ -1,12 +1,25 @@
 "use client";
 
-import { useState } from "react";
+import { useCallback } from "react";
+import { useSearchParams } from "next/navigation";
 import AllModelsTab from "@/app/(dashboard)/models-and-endpoints/components/AllModelsTab";
+import { ALL_MODEL_GROUPS_VALUE } from "@/app/(dashboard)/models-and-endpoints/components/AllModelsTable";
 import { useModelDashboardData } from "@/app/(dashboard)/models-and-endpoints/useModelDashboardData";
 import { useModelDetailRouting } from "@/app/(dashboard)/models-and-endpoints/detailNavigation";
+import { navigateWithParams } from "@/app/(dashboard)/navigateWithParams";
 
 export default function AllModelsPanel() {
-  const [selectedModelGroup, setSelectedModelGroup] = useState<string | null>(null);
+  const searchParams = useSearchParams();
+  const selectedModelGroup = searchParams?.get("model_group") ?? null;
+  const setSelectedModelGroup = useCallback((modelGroup: string) => {
+    navigateWithParams((params) => {
+      if (modelGroup && modelGroup !== ALL_MODEL_GROUPS_VALUE) {
+        params.set("model_group", modelGroup);
+      } else {
+        params.delete("model_group");
+      }
+    }, "replace");
+  }, []);
   const { availableModelGroups, availableModelAccessGroups } = useModelDashboardData();
   const { openModel, openTeam } = useModelDetailRouting();