feat(webui): switch model presets from the composer (#5077)

webui/src/tests/thread-display-compat.test.ts

@@ -1,6 +1,10 @@
 import { describe, expect, it } from "vitest";
 
-import { normalizeLegacyLongTaskMessages } from "@/lib/thread-display-compat";
+import { deriveTitle, isModelCommandText, visibleSessionPreview } from "@/lib/format";
+import {
+  normalizeLegacyLongTaskMessages,
+  projectWebuiThreadMessages,
+} from "@/lib/thread-display-compat";
 import type { UIMessage } from "@/lib/types";
 
 describe("normalizeLegacyLongTaskMessages", () => {
@@ -17,4 +21,29 @@ describe("normalizeLegacyLongTaskMessages", () => {
     expect(out[0]!.role).toBe("tool");
     expect(out[0]!.traces).toEqual(["long_task · done"]);
   });
+
+  it("removes model and silent-command turns without hiding concurrent replies", () => {
+    const message = (
+      id: string,
+      role: UIMessage["role"],
+      content: string,
+      turnId?: string,
+    ): UIMessage => ({ id, role, content, createdAt: 1, turnId });
+    const visible = projectWebuiThreadMessages([
+      message("model", "user", "/model fast", "model-turn"),
+      message("model-reply", "assistant", "Switched model preset to fast.", "model-turn"),
+      message("silent", "user", "/restart", "webui-system:restart"),
+      message("reply", "assistant", "This unrelated reply stays visible.", "other-turn"),
+    ]);
+
+    expect(visible.map(({ content }) => content)).toEqual([
+      "This unrelated reply stays visible.",
+    ]);
+    expect([
+      isModelCommandText("/MODEL@nanobot fast"),
+      isModelCommandText("/modelish"),
+    ]).toEqual([true, false]);
+    expect(visibleSessionPreview("Switched model preset to `fast`.")).toBe("");
+    expect(deriveTitle("## Model\n- Current model: `gpt-5.5`", "New chat")).toBe("New chat");
+  });
 });