fix(desktop): report a failed DM close instead of silently restoring the row

desktop/playwright.config.ts

@@ -20,6 +20,7 @@ export default defineConfig({
       name: "smoke",
       testMatch: [
         "**/smoke.spec.ts",
+        "**/dm-hide-failure.spec.ts",
         "**/owned-agent-discovery.spec.ts",
         "**/thread-head-stale-edit.spec.ts",
         "**/sidebar-offcanvas-rail.spec.ts",

desktop/src/app/AppShell.tsx

@@ -2,6 +2,7 @@ import * as React from "react";
 import { ProtectedGlobalOverlay } from "@protected-feature-components";
 import { useQueryClient } from "@tanstack/react-query";
 import { Outlet, useLocation } from "@tanstack/react-router";
+import { toast } from "sonner";
 import { deriveShellRoute, markAllReadSources } from "@/app/AppShell.helpers";
 import { useTerminalContext } from "@/app/useTerminalContext";
 import { AppShellProvider } from "@/app/AppShellContext";
@@ -625,7 +626,12 @@ export function AppShell() {
     async (channelId: string) => {
       try {
         await hideDmMutation.mutateAsync(channelId);
-      } catch {
+      } catch (error) {
+        toast.error(
+          error instanceof Error
+            ? error.message
+            : "Failed to close direct message",
+        );
         return;
       }
 

desktop/src/testing/e2eBridge.ts

@@ -1364,6 +1364,8 @@ declare global {
     __BUZZ_E2E_UNSUPPORTED_PROJECT_ANNOUNCEMENTS__?: boolean;
     /** Project event kinds accepted once but reported as failed to test lost acknowledgements. */
     __BUZZ_E2E_FAIL_PROJECT_EVENT_ACK_KINDS__?: number[];
+    /** Makes hiding a DM fail, to exercise the error path of the sidebar close action. */
+    __BUZZ_E2E_FAIL_HIDE_DM__?: string;
     /**
      * Extra project events appended to the mock store on first access.
      * Use to seed standalone repositories (kind 30617) or other project-scoped
@@ -7401,6 +7403,11 @@ async function handleHideDm(
   args: { channelId: string },
   config: E2eConfig | undefined,
 ) {
+  const forcedFailure = window.__BUZZ_E2E_FAIL_HIDE_DM__;
+  if (forcedFailure) {
+    throw new Error(forcedFailure);
+  }
+
   const identity = getIdentity(config);
   if (!identity) {
     const index = mockChannels.findIndex(

desktop/tests/e2e/dm-hide-failure.spec.ts

@@ -0,0 +1,30 @@
+import { expect, test } from "@playwright/test";
+
+import { installMockBridge } from "../helpers/bridge";
+
+const DM_NAME = "alice-tyler";
+const RELAY_ERROR = "relay error 400: forbidden: not a member of this DM";
+
+test("a rejected DM close reports the relay error and keeps the row", async ({
+  page,
+}) => {
+  await page.addInitScript((message) => {
+    window.__BUZZ_E2E_FAIL_HIDE_DM__ = message;
+  }, RELAY_ERROR);
+  await installMockBridge(page);
+  await page.goto("/", { waitUntil: "domcontentloaded" });
+
+  const dmRow = page.getByTestId(`channel-${DM_NAME}`);
+  await expect(dmRow).toBeVisible();
+
+  await dmRow.hover();
+  await page.getByTestId(`hide-dm-${DM_NAME}`).click();
+
+  await expect(
+    page.locator("[data-sonner-toast]").filter({ hasText: RELAY_ERROR }),
+  ).toBeVisible();
+
+  // The optimistic removal must roll back: the conversation is still there,
+  // so the sidebar must not claim it went away.
+  await expect(dmRow).toBeVisible();
+});