fix(ui): unify Session navigation and restore uniform tab borders

frontend/e2e/database-management-layout.spec.ts

@@ -409,7 +409,7 @@ test("context panels stay inside the manager and the Tables grid sits in a sideb
 
   await page.goto(stack.publicUrl);
   await signInAsAdmin(page);
-  await expectCurrentNavigation(page, "New session");
+  await expectCurrentNavigation(page, "Session");
   await expectSelectedSessionScopeTab(page, "My sessions");
   await page.getByRole("tab", { name: "All sessions", exact: true }).click();
   await expectSelectedSessionScopeTab(page, "All sessions");
@@ -808,7 +808,7 @@ test("Workspace and Pi management share the centered work-area panel without cov
       .getByRole("button", { name: "Close Pi management" })
       .click();
     await expect(piTrigger).toBeFocused();
-    await expectCurrentNavigation(page, "New session");
+    await expectCurrentNavigation(page, "Session");
   }
 
   await page.setViewportSize({ width: 720, height: 800 });

frontend/e2e/f1.spec.ts

@@ -39,7 +39,7 @@ test("F1 loop: new question → F1 widget → respond", async ({ page }) => {
   await signInLocally(page);
 
   // Focus the composer for a new session.
-  await page.getByRole("button", { name: "New session", exact: true }).click();
+  await page.getByRole("button", { name: "Session", exact: true }).click();
 
   // Fill in the question.
   await page.getByLabel("New question").fill("quante cardioversioni nel 2024");

frontend/e2e/ui-visual-review.spec.ts

@@ -135,7 +135,7 @@ for (const width of [390, 1280]) {
       expect(Math.abs(modelBox!.y - doneBox!.y)).toBeLessThan(1);
       expect(doneBox!.x).toBeGreaterThan(modelBox!.x + modelBox!.width);
       for (const name of ["My sessions", "All sessions"]) {
-        await expect(page.getByRole("tab", { name, exact: true })).toHaveCSS("border-bottom-width", "0px");
+        await expect(page.getByRole("tab", { name, exact: true })).toHaveCSS("border-bottom-width", "1px");
       }
     }
     expect(await inspect(page)).toEqual({ overflow: 0, serif: [], tiny: [] });
@@ -162,6 +162,42 @@ for (const width of [390, 1280]) {
   });
 }
 
+test("session tabs have padded labels and matching one-pixel borders on every side", async ({ page }, testInfo) => {
+  await page.setViewportSize({ width: 1280, height: 1000 });
+  await fixtures(page);
+  await page.goto("/?thoth_route=administration%2Fdatabase");
+  const header = page.locator(".thot-full-header");
+  for (const locale of ["en", "it"]) {
+    await header.getByRole("combobox").selectOption(locale);
+    await expect(page.getByRole("button", { name: locale === "it" ? "Sessione" : "Session", exact: true })).toHaveCount(1);
+    await expect(page.getByRole("button", { name: /^(New session|Return to session|Nuova sessione|Torna alla sessione)$/ })).toHaveCount(0);
+    const tabs = page.locator('[role="tablist"]').getByRole("tab");
+    for (const theme of ["light", "dark"]) {
+      if (theme === "dark") await header.getByRole("button", { name: locale === "it" ? "Usa il tema scuro" : "Use dark theme", exact: true }).click();
+      for (const selected of [0, 1]) {
+        await tabs.nth(selected).click();
+        await expect(tabs.nth(selected)).toHaveAttribute("aria-selected", "true");
+        for (const tab of await tabs.all()) {
+          await expect(tab).toHaveCSS("border-bottom-width", "1px");
+          const borders = await tab.evaluate(el => {
+            const css = getComputedStyle(el);
+            return { widths: [css.borderTopWidth, css.borderRightWidth, css.borderBottomWidth, css.borderLeftWidth],
+              colors: [css.borderTopColor, css.borderRightColor, css.borderBottomColor, css.borderLeftColor],
+              paddingX: css.paddingLeft, paddingY: css.paddingTop,
+              fits: el.scrollHeight <= el.clientHeight };
+          });
+          expect(borders.widths).toEqual(["1px", "1px", "1px", "1px"]);
+          expect(new Set(borders.colors).size).toBe(1);
+          expect(borders).toMatchObject({ paddingX: "11px", paddingY: "3px", fits: true });
+        }
+      }
+      await page.mouse.move(0, 0);
+      await page.screenshot({ path: testInfo.outputPath(`session-tabs-${locale}-${theme}.png`), animations: "disabled" });
+      if (theme === "dark") await header.getByRole("button", { name: locale === "it" ? "Usa il tema chiaro" : "Use light theme", exact: true }).click();
+    }
+  }
+});
+
 for (const locale of ["en", "it"]) {
   test(`login keeps only the main title in ${locale}`, async ({ page }, testInfo) => {
     await fixtures(page);
@@ -202,7 +238,7 @@ for (const route of ["/", "/?thoth_route=administration%2Fdatabase"]) {
     await page.goto(route);
     if (route !== "/") {
       await navigation(page);
-      await page.getByRole("button", { name: "Return to session", exact: true }).click();
+      await page.getByRole("button", { name: "Session", exact: true }).click();
     }
     const prompt = page.getByRole("textbox", { name: "New question", exact: true });
     await expect(prompt).toBeVisible();
@@ -234,14 +270,14 @@ for (const route of ["/", "/?thoth_route=administration%2Fdatabase"]) {
     expect(await prompt.evaluate(el => el.scrollHeight > el.clientHeight)).toBe(true);
     await admin(page, "Database");
     await navigation(page);
-    await page.getByRole("button", { name: "Return to session", exact: true }).click();
+    await page.getByRole("button", { name: "Session", exact: true }).click();
     await expect(prompt).toHaveValue(question);
     await readable();
     await page.screenshot({ path: testInfo.outputPath("Prompt-multiline-mobile.png") });
     await prompt.fill("");
     await readable();
     await expect.poll(() => prompt.evaluate(el => el.clientHeight)).toBe(emptyHeight);
-    expect(writes).toEqual([]);
+    expect(writes).toEqual(route === "/" ? ["/runtime/prewarm"] : ["/runtime/prewarm", "/runtime/prewarm"]);
   });
 }
 
@@ -361,13 +397,13 @@ test("theme follows the app, not an unrelated OS preference; keyboard tabs and d
   await admin(page, "Memory");
   await page.getByRole("button", { name: "New card", exact: true }).click();
   await page.getByRole("textbox", { name: "Title", exact: true }).fill("Keep this draft");
-  await page.getByRole("button", { name: "Return to session", exact: true }).click();
+  await page.getByRole("button", { name: "Session", exact: true }).click();
   await expect(page.getByRole("textbox", { name: "Title", exact: true })).toHaveValue("Keep this draft");
   await page.screenshot({ path: testInfo.outputPath("Memory-dark-unsaved.png") });
   await page.getByRole("button", { name: "Cancel", exact: true }).click();
-  await page.getByRole("button", { name: "Return to session", exact: true }).click();
+  await page.getByRole("button", { name: "Session", exact: true }).click();
   await expect(page.getByRole("textbox", { name: "New question", exact: true })).toBeVisible();
-  expect(writes).toEqual([]);
+  expect(writes).toEqual(["/runtime/prewarm"]);
 });
 
 test("host header and left rail leave the application a bounded working area", async ({ page }, testInfo) => {

frontend/src/App.test.tsx

@@ -46,7 +46,7 @@ test("local authentication renders the standalone logout control", async () => {
 
   render(<App />);
 
-  expect(await screen.findByRole("button", { name: "New session" })).toBeInTheDocument();
+  expect(await screen.findByRole("button", { name: "Session" })).toBeInTheDocument();
   expect(screen.getByText("Portal user")).toBeInTheDocument();
   await userEvent.click(within(screen.getByRole("banner", { name: "Application header" })).getByRole("button", { name: "Portal user" }));
   expect(await screen.findByRole("menuitem", { name: "Log out" })).toBeInTheDocument();
@@ -113,7 +113,7 @@ test("a local login always enters the core activity", async () => {
   await userEvent.type(screen.getByLabelText(/^password$/i), "correct-password");
   await userEvent.click(screen.getByRole("button", { name: /sign in/i }));
 
-  expect(await screen.findByRole("button", { name: "New session" }))
+  expect(await screen.findByRole("button", { name: "Session" }))
     .toHaveAttribute("aria-current", "page");
   expect(screen.queryByRole("main", { name: "Database management" })).not.toBeInTheDocument();
 });

frontend/src/i18n/locales/it-core.ts

@@ -86,6 +86,8 @@ export const itCore: Record<string, string> = {
   "Human-in-the-loop review": "revisione umana",
   "Return to session": "Torna alla sessione",
   "New session": "Nuova sessione",
+  "Session": "Sessione",
+  "Start with Session.": "Inizia con Sessione.",
   "Administration": "Amministrazione",
   "Database management permission is required": "È richiesto il permesso di gestione dei database",
   "Database": "Database",

frontend/src/shell/AppShell.administration.test.tsx

@@ -95,7 +95,7 @@ test("Back and Core navigation preserve a Memory draft until the editor cancels
   act(() => window.history.back());
   await waitFor(() => expect(new URLSearchParams(window.location.search).get("thoth_route")).toBe("administration/memory"));
   expect(within(page).getByLabelText("Title")).toHaveValue("Keep this draft");
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(page).toBeVisible();
   expect(confirm).not.toHaveBeenCalled();
   confirm.mockReturnValue(true);
@@ -138,7 +138,7 @@ test("option A has one collapsible global context and preserves the Core draft a
   await userEvent.click(screen.getByRole("button", { name: "Memory" }));
   expect(await screen.findByRole("main", { name: "Memory management" })).toBeVisible();
   expect(screen.queryByRole("textbox", { name: /new question/i })).not.toBeInTheDocument();
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(screen.getByRole("textbox", { name: /new question/i })).toBe(composer);
   expect(composer).toHaveValue("Keep my original Core question");
 });
@@ -149,7 +149,7 @@ test("invalid remembered choices do not silently fall back and gate both Core an
   window.history.replaceState(null, "", "/?thoth_route=administration/memory");
   renderShell();
   await screen.findByText(/Unavailable saved choices are not replaced/);
-  expect(screen.getByRole("button", { name: "New session" })).toBeDisabled();
+  expect(screen.getByRole("button", { name: "Session" })).toBeDisabled();
   expect(screen.queryByRole("main", { name: "Memory management" })).not.toBeInTheDocument();
   expect(screen.queryByRole("textbox", { name: /new question/i })).not.toBeInTheDocument();
   await userEvent.selectOptions(screen.getByRole("combobox", { name: "Workspace" }), "alpha");
@@ -193,7 +193,7 @@ test("dirty Memory blocks workspace and model changes, including after a failed
   await userEvent.click(within(page).getByRole("button", { name: "Save card" }));
   await waitFor(() => expect(saveAttempts).toBe(1));
   expect(await within(page).findByRole("alert")).toBeVisible();
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(page).toBeVisible();
   expect(within(page).getByLabelText("Title")).toHaveValue("Do not lose this");
 });
@@ -245,12 +245,12 @@ test("a successful Memory save releases the navigation guard and the context loc
   await userEvent.click(screen.getByRole("button", { name: /Working context/ }));
   await userEvent.click(within(page).getByRole("button", { name: "Save card" }));
   expect(screen.getByRole("combobox", { name: "Model" })).toBeDisabled();
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(page).toBeVisible();
   await act(async () => release());
   await within(page).findByText("Saved and indexed.");
   expect(screen.getByRole("combobox", { name: "Model" })).toBeEnabled();
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(await screen.findByRole("textbox", { name: /new question/i })).toBeVisible();
 });
 

frontend/src/shell/AppShell.auth.test.tsx

@@ -118,7 +118,7 @@ describe("authenticated shell permissions", () => {
   test("hides administrative navigation from a session user", async () => {
     renderShell({ subject: "user-1", isAdmin: false, roles: ["user"], permissions: ["session.use"] });
 
-    expect(await screen.findByRole("button", { name: "New session" })).toBeInTheDocument();
+    expect(await screen.findByRole("button", { name: "Session" })).toBeInTheDocument();
     expect(screen.queryByRole("button", { name: "Administration" })).not.toBeInTheDocument();
     expect(screen.queryByRole("button", { name: "Database" })).not.toBeInTheDocument();
     expect(screen.queryByRole("button", { name: "Workspace" })).not.toBeInTheDocument();

frontend/src/shell/AppShell.database-management.test.tsx

@@ -105,7 +105,7 @@ test("starts on the core activity after a hard refresh even if metadata manageme
   await expandAdministration();
 
   const sessionNavigation = screen.getByRole("complementary", { name: "Session navigation" });
-  expect(within(sessionNavigation).getByRole("button", { name: "New session" }))
+  expect(within(sessionNavigation).getByRole("button", { name: "Session" }))
     .toHaveAttribute("aria-current", "page");
   expect(within(sessionNavigation).getByRole("button", { name: "Database" }))
     .not.toHaveAttribute("aria-current");
@@ -118,7 +118,7 @@ test("replaces the core conversation while keeping the session navigation", asyn
 
   const conversationColumn = screen.getByTestId("conversation-column");
   const sessionNavigation = screen.getByRole("complementary", { name: "Session navigation" });
-  const newSession = within(sessionNavigation).getByRole("button", { name: "New session" });
+  const newSession = within(sessionNavigation).getByRole("button", { name: "Session" });
   const databaseManagement = within(sessionNavigation).getByRole("button", { name: "Database" });
 
   expect(newSession).toHaveAttribute("aria-current", "page");
@@ -146,6 +146,7 @@ test("replaces the core conversation while keeping the session navigation", asyn
 });
 
 test("keeps a live core session connected while returning from database management", async () => {
+  let resumes = 0;
   server.use(
     http.get("/api/sessions", () => HttpResponse.json([{
       id: "s1",
@@ -160,10 +161,10 @@ test("keeps a live core session connected while returning from database manageme
       archived: false,
       active: true,
     }])),
-    http.post("/api/sessions/:id/resume", ({ params }) => HttpResponse.json({
+    http.post("/api/sessions/:id/resume", ({ params }) => { resumes++; return HttpResponse.json({
       id: params.id,
       alreadyActive: true,
-    })),
+    }); }),
     http.get("/api/sessions/:id", ({ params }) => HttpResponse.json({
       id: params.id,
       status: "open",
@@ -185,13 +186,19 @@ test("keeps a live core session connected while returning from database manageme
   expect(FakeEventSource.instances).toHaveLength(1);
 
   expect(session).toBeVisible();
-  await userEvent.click(session);
+  expect(screen.queryByRole("button", { name: "Return to session" })).not.toBeInTheDocument();
+  expect(screen.queryByRole("button", { name: "New session" })).not.toBeInTheDocument();
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
 
   await waitFor(() => {
     expect(screen.queryByRole("main", { name: "Database management" })).not.toBeInTheDocument();
   });
   expect(source.closed).toBe(false);
   expect(FakeEventSource.instances).toHaveLength(1);
+  expect(resumes).toBe(1);
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
+  expect(source.closed).toBe(false);
+  expect(resumes).toBe(1);
 });
 
 test("hides the complete administrative navigation from a regular user", () => {
@@ -208,7 +215,7 @@ test("hides the complete administrative navigation from a regular user", () => {
 
   renderShell();
 
-  expect(screen.getByRole("button", { name: "New session" })).toBeInTheDocument();
+  expect(screen.getByRole("button", { name: "Session" })).toBeInTheDocument();
   expect(screen.queryByRole("button", { name: "Administration" })).not.toBeInTheDocument();
   expect(screen.queryByRole("button", { name: "Workspace" })).not.toBeInTheDocument();
   expect(screen.queryByRole("button", { name: "Database" })).not.toBeInTheDocument();
@@ -256,7 +263,7 @@ test("requires saving or cancelling a dirty database form before leaving", async
   await userEvent.clear(schema);
   await userEvent.type(schema, "reporting");
 
-  const newSession = screen.getByRole("button", { name: "New session" });
+  const newSession = screen.getByRole("button", { name: "Session" });
   await userEvent.click(newSession);
 
   expect(confirm).not.toHaveBeenCalled();

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

@@ -47,9 +47,11 @@ beforeEach(() => {
   );
 });
 
-test("New session starts prewarm without delaying composer focus", async () => {
+test("Session prepares a new question without creating a session before submission", async () => {
   let prewarmStarted = false;
+  const create = vi.fn(() => HttpResponse.json({ id: "unexpected" }));
   server.use(
+    http.post("/api/sessions", create),
     http.post("/api/runtime/prewarm", async () => {
       prewarmStarted = true;
       await delay(100);
@@ -58,16 +60,18 @@ test("New session starts prewarm without delaying composer focus", async () => {
   );
   renderShell();
 
-  await userEvent.click(screen.getByRole("button", { name: /^new session$/i }));
+  await userEvent.click(screen.getByRole("button", { name: /^Session$/i }));
 
   const composer = await screen.findByRole("textbox", { name: /new question/i });
   await waitFor(() => expect(prewarmStarted).toBe(true));
   await waitFor(() => expect(composer).toHaveFocus());
   expect(composer).toHaveAttribute("data-awaiting-input", "true");
   expect(composer).toHaveClass("thot-awaiting-input");
+  expect(create).not.toHaveBeenCalled();
+  expect(screen.getAllByRole("button", { name: "Session" })).toHaveLength(1);
 });
 
-test("a known preprocessing requirement disables New session", async () => {
+test("a known preprocessing requirement disables Session when no session is open", async () => {
   server.use(
     http.get("/api/workspaces/default/preprocessing", () => HttpResponse.json({
       schemaVersion: 1,
@@ -81,7 +85,7 @@ test("a known preprocessing requirement disables New session", async () => {
   );
   renderShell();
 
-  const newSession = screen.getByRole("button", { name: "New session" });
+  const newSession = screen.getByRole("button", { name: "Session" });
   await waitFor(() => expect(newSession).toBeDisabled());
   expect(newSession).toHaveAttribute("data-navigation-state", "unavailable");
   await waitFor(() => expect(newSession).toHaveAttribute("title", "Catalog revision 18 is not indexed."));
@@ -110,6 +114,10 @@ test("records the prompt without central duplication, then opens the live log",
     phase: "F1",
     text: "How many patients?",
   });
+  // Clicking the unified navigation while creation is pending must not discard
+  // its operation token or the provisional transcript.
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
+  expect(useSessionStore.getState().activityLog[0]?.text).toBe("How many patients?");
   releaseCreate();
   await waitFor(() => expect(FakeEventSource.instances).toHaveLength(1));
   act(() => FakeEventSource.instances[0].emit({ type: "text_delta", text: "Inspecting cohort" }));
@@ -211,7 +219,7 @@ test("opens Workspace management from the right sidebar without interrupting the
   const workArea = screen.getByTestId("conversation-column");
   const sessionNavigation = screen.getByRole("complementary", { name: "Session navigation" });
   const workspaceManagement = within(sessionNavigation).getByRole("button", { name: "Workspace" });
-  const newSession = within(sessionNavigation).getByRole("button", { name: "New session" });
+  const newSession = within(sessionNavigation).getByRole("button", { name: "Session" });
   expect(workArea).toContainElement(dialog);
   expect(sessionNavigation).not.toContainElement(dialog);
   expect(screen.getByTestId("app-shell")).toHaveAttribute("data-activity-layout", "closed");
@@ -222,7 +230,7 @@ test("opens Workspace management from the right sidebar without interrupting the
   expect(newSession).toHaveAttribute("data-navigation-state", "available");
   expect(newSession).not.toHaveAttribute("aria-current");
 
-  await userEvent.click(screen.getByRole("button", { name: "Return to session" }));
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   await waitFor(() => expect(screen.queryByRole("main", { name: "Workspace management" })).not.toBeInTheDocument());
   expect(newSession).toHaveAttribute("aria-current", "page");
   expect(newSession).toHaveAttribute("data-navigation-state", "current");
@@ -240,7 +248,7 @@ test("does not block the shell when the DWH is unavailable at startup", async ()
   );
   renderShell();
 
-  expect(await screen.findByRole("button", { name: "New session" })).toBeVisible();
+  expect(await screen.findByRole("button", { name: "Session" })).toBeVisible();
   expect(screen.queryByRole("button", { name: "Administration" })).not.toBeInTheDocument();
   expect(screen.queryByRole("heading", { name: "Connection unavailable" })).not.toBeInTheDocument();
   expect(healthChecks).toBe(0);

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

@@ -136,7 +136,7 @@ test("Pi management preserves the open session summary and the model activity ti
   const workArea = screen.getByTestId("conversation-column");
   const sessionNavigation = screen.getByRole("complementary", { name: "Session navigation" });
   const piManagement = within(sessionNavigation).getByRole("button", { name: "Pi configuration" });
-  const newSession = within(sessionNavigation).getByRole("button", { name: "New session" });
+  const newSession = within(sessionNavigation).getByRole("button", { name: "Session" });
   expect(workArea).toContainElement(dialog);
   expect(sessionNavigation).not.toContainElement(dialog);
   expect(piManagement).toHaveAttribute("aria-current", "page");
@@ -147,7 +147,9 @@ test("Pi management preserves the open session summary and the model activity ti
   const preservedSummary = document.querySelector('[aria-label="Session summary"]');
   expect(preservedSummary).toHaveAttribute("aria-hidden", "true");
   expect(preservedSummary).toHaveTextContent("Attiva uno");
-  await user.click(screen.getByRole("button", { name: "Return to session" }));
+  // A cold document panel is not a running session. Reopen it from its row;
+  // the unified Session action would prepare a new question instead.
+  await user.click(screen.getByTestId("session-item-s1"));
   await waitFor(() => {
     expect(screen.getByRole("complementary", { name: "Session summary" })).toHaveTextContent("Domanda originale");
   });
@@ -160,7 +162,7 @@ test("Pi management preserves the open session summary and the model activity ti
   await screen.findByRole("button", { name: "Show model activity" });
   act(() => useSessionStore.getState().setLastUserEntry({ kind: "input", text: "Preserved activity" }));
   await user.click(screen.getByRole("button", { name: "Pi configuration" }));
-  await user.click(await screen.findByRole("button", { name: "Return to session" }));
+  await user.click(await screen.findByRole("button", { name: "Session" }));
   await waitFor(() => expect(screen.queryByRole("heading", { name: "Pi management" })).not.toBeInTheDocument());
   await user.click(screen.getByRole("button", { name: "Show model activity" }));
   expect(await screen.findByRole("heading", { name: "Model activity" })).toBeVisible();
@@ -190,8 +192,10 @@ test("administrators can explicitly switch to all sessions and see owners", asyn
   expect(mySessions).toHaveAttribute("tabindex", "0");
   expect(mySessions).toHaveAttribute("data-tab-state", "active");
   expect(mySessions).toHaveClass("bg-[oklch(var(--nav-active))]");
-  expect(mySessions).toHaveClass("border-b-0");
-  expect(allSessions).toHaveClass("border-b-0");
+  expect(mySessions).toHaveClass("border", "px-[11px]", "py-[3px]");
+  expect(allSessions).toHaveClass("border", "px-[11px]", "py-[3px]");
+  expect(mySessions).not.toHaveClass("border-b-0", "border-b-2", "-mb-px");
+  expect(tablist).not.toHaveClass("border-b");
   expect(allSessions).toHaveAttribute("aria-selected", "false");
   expect(allSessions).toHaveAttribute("aria-controls", "session-scope-panel");
   expect(allSessions).toHaveAttribute("tabindex", "-1");
@@ -403,7 +407,7 @@ test("New session closes an open session detail panel", async () => {
   wrap();
   await userEvent.click(await screen.findByText("Attiva uno")); // cold session → panel opens
   await screen.findByText("Domanda originale");
-  await userEvent.click(screen.getByRole("button", { name: /^new session$/i }));
+  await userEvent.click(screen.getByRole("button", { name: /^Session$/i }));
   await waitFor(() => expect(screen.queryByText("Domanda originale")).not.toBeInTheDocument());
   expect(screen.getByText(/type your question/i)).toBeInTheDocument();
 });
@@ -822,7 +826,7 @@ test("starting a new question invalidates a pending Resume intent", async () =>
   await userEvent.click(await screen.findByText("Attiva uno"));
   await userEvent.click(await screen.findByRole("button", { name: /resume/i }));
   await resumeStarted.promise;
-  await userEvent.click(screen.getByRole("button", { name: /^new session$/i }));
+  await userEvent.click(screen.getByRole("button", { name: /^Session$/i }));
   expect(await screen.findByText(/type your question/i)).toBeInTheDocument();
 
   resumeGate.resolve();

frontend/src/shell/AppShell.tsx

@@ -61,7 +61,7 @@ interface AppShellProps {
 const SESSION_SCOPES: readonly SessionScope[] = ["mine", "all"];
 
 function sessionScopeTabClass(selected: boolean): string {
-  const base = "relative -mb-px flex h-8 w-full cursor-pointer items-center justify-center rounded-t-md border border-b-0 px-2 text-xs font-semibold tracking-[0.005em] outline-none focus-visible:z-10 focus-visible:ring-3 focus-visible:ring-[oklch(var(--nav-active-border)/0.28)]";
+  const base = "relative flex min-h-[38px] w-full cursor-pointer items-center justify-center rounded-md border px-[11px] py-[3px] text-xs font-semibold tracking-[0.005em] outline-none focus-visible:z-10 focus-visible:ring-3 focus-visible:ring-[oklch(var(--nav-active-border)/0.28)]";
   return selected
     ? `${base} border-[oklch(var(--nav-active-border))] bg-[oklch(var(--nav-active))] text-[oklch(var(--nav-active-foreground))] hover:bg-[oklch(var(--nav-active-hover))]`
     : `${base} border-border bg-card text-muted-foreground hover:border-muted-foreground/45 hover:bg-muted/55 hover:text-foreground`;
@@ -638,6 +638,8 @@ export function AppShell({ canLogout }: AppShellProps) {
     deliveredToastCountRef.current = sessionToasts.length;
   }, [sessionToasts]);
   const sessionViewOpen = Boolean(activeSessionId) || creatingSession;
+  const canReturnToCurrentSession = creatingSession || (Boolean(activeSessionId) && !finalized && !activeSession?.archived);
+  const sessionActionUnavailable = !canReturnToCurrentSession && (preprocessingBlocksNewSession || !workingContext.ready || administrationBusy);
   const working = sessionViewOpen && !pendingWidget && agentActive;
   // The workflow bar runs only while the harness works, not while a finalized
   // session sits idle or a gate awaits the reviewer (pendingWidget).
@@ -965,19 +967,21 @@ export function AppShell({ canLogout }: AppShellProps) {
         </div>
 
         <div className="thot-session-navigation__primary-controls">
-          {activeSurface !== "core" && <Button variant="outline" size="sm" className="w-full" onClick={() => navigate({ surface: "core" })}>{t("Return to session")}</Button>}
           <Button
             variant={currentNavigation === "core" ? "navigationActive" : "outline"}
             size="sm"
             className="w-full min-w-0 max-w-full gap-[0.25rem] px-[0.75rem]"
             aria-current={currentNavigation === "core" ? "page" : undefined}
-            data-navigation-state={preprocessingBlocksNewSession || !workingContext.ready || administrationBusy
+            data-navigation-state={sessionActionUnavailable
               ? "unavailable"
               : currentNavigation === "core" ? "current" : "available"}
-            disabled={preprocessingBlocksNewSession || !workingContext.ready || administrationBusy}
-            title={preprocessingBlocksNewSession ? preprocessingQuery.data?.detail : undefined}
-            onClick={startNewSession}
-          >{t("New session")}</Button>
+            disabled={sessionActionUnavailable}
+            title={sessionActionUnavailable && preprocessingBlocksNewSession ? preprocessingQuery.data?.detail : undefined}
+            onClick={() => {
+              if (canReturnToCurrentSession) navigate({ surface: "core" });
+              else startNewSession();
+            }}
+          >{t("Session")}</Button>
           {isAdmin && (
             <Accordion.Root
               value={adminNavigationValue}
@@ -1075,7 +1079,7 @@ export function AppShell({ canLogout }: AppShellProps) {
               role="tablist"
               aria-label={t("Session scope")}
               aria-orientation="horizontal"
-              className="grid grid-cols-2 border-b border-border"
+              className="grid grid-cols-2 gap-1"
             >
               <button
                 ref={(node) => { sessionScopeTabRefs.current.mine = node; }}

frontend/src/shell/NavSessions.tsx

@@ -29,7 +29,7 @@ export function NavSessions({
   if (sessions.length === 0) {
     return (
       <p className="px-1 py-6 text-center text-xs text-muted-foreground">
-        {translate("No sessions yet.")} <span className="font-medium text-foreground">{translate("Start with New session.")}</span>
+        {translate("No sessions yet.")} <span className="font-medium text-foreground">{translate("Start with Session.")}</span>
       </p>
     );
   }

frontend/src/shell/host/AppShell.host.test.tsx

@@ -66,7 +66,7 @@ test("full controls change locale/theme and follow fullscreen entry, exit, Esc,
   expect(within(header).getByRole("button", { name: "Analyst" })).toBeInTheDocument();
   expect(within(header).queryByRole("button", { name: /admin|settings/i })).not.toBeInTheDocument();
   await userEvent.selectOptions(within(header).getByRole("combobox", { name: "Interface language" }), "it");
-  expect(await screen.findByRole("button", { name: "Nuova sessione" })).toBeInTheDocument();
+  expect(await screen.findByRole("button", { name: "Sessione" })).toBeInTheDocument();
   await userEvent.selectOptions(within(header).getByRole("combobox", { name: "Lingua dell’interfaccia" }), "en");
   await userEvent.click(within(header).getByRole("button", { name: "Use dark theme" }));
   expect(document.documentElement).toHaveAttribute("data-bs-theme", "dark");
@@ -130,7 +130,7 @@ test("legacy embedded consumes the portal state and supplies no duplicate contro
   select.dataset.lang = "it";
   document.body.append(select);
   render(<App />);
-  expect(await screen.findByRole("button", { name: "Nuova sessione" })).toBeInTheDocument();
+  expect(await screen.findByRole("button", { name: "Sessione" })).toBeInTheDocument();
   expect(screen.queryByRole("banner", { name: /application|intestazione/i })).not.toBeInTheDocument();
   expect(screen.queryByRole("button", { name: /fullscreen|tema|Log out/i })).not.toBeInTheDocument();
   act(() => { document.documentElement.setAttribute("data-bs-theme", "light"); });
@@ -160,8 +160,8 @@ test("reload restores only an authorized session document panel without resuming
   expect(resume).not.toHaveBeenCalled();
   expect(FakeEventSource.instances).toHaveLength(0);
   expect(readRememberedSession(user)).toBe("saved");
-  await waitFor(() => expect(screen.getByRole("button", { name: "New session" })).toBeEnabled());
-  await userEvent.click(screen.getByRole("button", { name: "New session" }));
+  await waitFor(() => expect(screen.getByRole("button", { name: "Session" })).toBeEnabled());
+  await userEvent.click(screen.getByRole("button", { name: "Session" }));
   expect(readRememberedSession(user)).toBeNull();
 });
 
@@ -172,7 +172,7 @@ test("reload ignores a session absent from the authorized list and isolates prin
   expect(readRememberedSession(user)).toBeNull();
   window.history.replaceState(null, "", "/");
   render(<App />);
-  await screen.findByRole("button", { name: "New session" });
+  await screen.findByRole("button", { name: "Session" });
   await waitFor(() => expect(readRememberedSession(user)).toBeNull());
   expect(screen.queryByRole("button", { name: "Resume" })).not.toBeInTheDocument();
   expect(FakeEventSource.instances).toHaveLength(0);