fix(frontend): surface session mutation failures via toast; doResume only activates on success

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/shell/AppShell.session-mgmt.test.tsx

@@ -62,3 +62,13 @@ test("Resume from the panel activates the session and closes the panel", async (
   await waitFor(() => expect(resumed).toBe("s1"));
   await waitFor(() => expect(screen.queryByText("Domanda originale")).not.toBeInTheDocument()); // panel closed
 });
+
+test("a failed resume keeps the panel open and does not activate the session", async () => {
+  server.use(http.post("http://localhost:8787/sessions/:id/resume", () => new HttpResponse(null, { status: 409 })));
+  wrap();
+  await userEvent.click(await screen.findByText("Attiva uno"));
+  await screen.findByText("Domanda originale"); // panel open
+  await userEvent.click(screen.getByRole("button", { name: /resume/i }));
+  // panel stays open (document still visible) after the failed resume
+  await waitFor(() => expect(screen.getByText("Domanda originale")).toBeInTheDocument());
+});

frontend/src/shell/AppShell.tsx

@@ -11,6 +11,7 @@ import { SteerInput, ComposerFooter } from "./SteerInput";
 import { WorkflowBar } from "./WorkflowBar";
 import { Button } from "../components/ui/button";
 import { Toaster } from "../components/ui/sonner";
+import { toast } from "sonner";
 import {
   closeSession, listSessions, resumeSession,
   renameSession, setSessionGroup, archiveSession, unarchiveSession, deleteSession,
@@ -52,19 +53,39 @@ export function AppShell() {
     if (s) setPanelSession(s);
   }
   async function doResume(id: string) {
-    await resumeSession(id);
-    setPanelSession(null);
-    setActiveSessionId(id);
+    try {
+      await resumeSession(id);
+      setPanelSession(null);
+      setActiveSessionId(id);
+    } catch {
+      toast.error("Failed to resume session.");
+    }
+  }
+  async function move(s: SessionSummary, group: string) {
+    try {
+      await setSessionGroup(s.id, group); refresh();
+    } catch {
+      toast.error("Failed to move session.");
+    }
   }
-  async function move(s: SessionSummary, group: string) { await setSessionGroup(s.id, group); refresh(); }
   async function newGroup(s: SessionSummary) {
     const name = window.prompt("New group:");
-    if (name && name.trim()) { await setSessionGroup(s.id, name.trim()); refresh(); }
+    if (name && name.trim()) {
+      try {
+        await setSessionGroup(s.id, name.trim()); refresh();
+      } catch {
+        toast.error("Failed to update group.");
+      }
+    }
   }
   async function toggleArchive(s: SessionSummary) {
-    await (s.archived ? unarchiveSession(s.id) : archiveSession(s.id));
-    if (panelSession?.id === s.id) setPanelSession(null);
-    refresh();
+    try {
+      await (s.archived ? unarchiveSession(s.id) : archiveSession(s.id));
+      if (panelSession?.id === s.id) setPanelSession(null);
+      refresh();
+    } catch {
+      toast.error(s.archived ? "Failed to restore session." : "Failed to archive session.");
+    }
   }
 
   function menuFor(s: SessionSummary) {
@@ -244,7 +265,15 @@ export function AppShell() {
           open
           initial={renameTarget.name ?? ""}
           onOpenChange={(o) => { if (!o) setRenameTarget(null); }}
-          onSubmit={async (name) => { await renameSession(renameTarget.id, name); setRenameTarget(null); refresh(); }}
+          onSubmit={async (name) => {
+            try {
+              await renameSession(renameTarget.id, name);
+              setRenameTarget(null);
+              refresh();
+            } catch {
+              toast.error("Failed to rename session.");
+            }
+          }}
         />
       )}
       {deleteTarget && (
@@ -253,10 +282,15 @@ export function AppShell() {
           label={deleteTarget.name || deleteTarget.question}
           onOpenChange={(o) => { if (!o) setDeleteTarget(null); }}
           onConfirm={async () => {
-            await deleteSession(deleteTarget.id);
-            if (panelSession?.id === deleteTarget.id) setPanelSession(null);
-            if (activeSessionId === deleteTarget.id) { resetSession(); setActiveSessionId(null); }
-            setDeleteTarget(null); refresh();
+            try {
+              await deleteSession(deleteTarget.id);
+              if (panelSession?.id === deleteTarget.id) setPanelSession(null);
+              if (activeSessionId === deleteTarget.id) { resetSession(); setActiveSessionId(null); }
+              setDeleteTarget(null);
+              refresh();
+            } catch {
+              toast.error("Failed to delete session.");
+            }
           }}
         />
       )}