Say what the thread side panels show, in plain words

frontend/app/lab/agent-screen-showcase.tsx

@@ -38,7 +38,7 @@ export function AgentScreenShowcase() {
         agentName="Nova"
         status="loading"
         loading
-        loadingCaption="No active sandbox. Send a message to start one."
+        loadingCaption="Nothing is running yet. Send a message to start one."
         screen={null}
         open={false}
         onOpenChange={() => {}}

frontend/components/chat/agent-detail.tsx

@@ -218,7 +218,7 @@ export function AgentDetail({
               onClick={() => void continueAsSession()}
               className="border-border-button-default bg-background-secondary-default text-body-2-medium text-text-primary hover:bg-background-tertiary-hover mb-2 rounded-lg border px-3 py-2 disabled:cursor-wait disabled:opacity-60"
             >
-              {continuing ? "Creating session…" : "Continue as session"}
+              {continuing ? "Creating thread…" : "Continue as thread"}
             </button>
           ) : null}
           {continueError ? (

frontend/components/chat/agents-rail.test.ts

@@ -150,7 +150,7 @@ describe("agents rail rows", () => {
     expect(html).toContain("Checkout is healthy.");
     expect(html).toContain("Inspect the checkout flow");
     expect(html).toContain("Completed");
-    expect(html).toContain("Continue as session");
+    expect(html).toContain("Continue as thread");
     expect(html).not.toContain("Working");
     expect(html).toContain("cancel</span> unavailable: This child is no longer running.");
     expect(html).not.toContain("No activity recorded");

frontend/components/chat/agents-rail.tsx

@@ -478,7 +478,7 @@ export function AgentsRail({
     <div
       ref={treeRef}
       role="tree"
-      aria-label="Child sessions"
+      aria-label="Subagents"
       aria-live="polite"
       aria-relevant="additions text"
       className="h-full space-y-2 overflow-y-auto p-3"

frontend/components/chat/artifacts-rail.tsx

@@ -75,17 +75,17 @@ export function ArtifactsRail({
     <div className="absolute inset-0 overflow-y-auto p-3">
       <div className="mb-3 flex items-center justify-between gap-3">
         <div className="min-w-0">
-          <p className="text-body-2-medium text-text-primary">Session files</p>
+          <p className="text-body-2-medium text-text-primary">Files</p>
           <p className="text-caption-1-regular text-text-tertiary">
-            Durable outputs you can preview, edit, or download
+            Finished files like a report or spreadsheet. Preview, edit, or download them.
           </p>
         </div>
         <IconButton
           size="small"
           icon={refreshing ? SpinningRefreshIcon : RiRefreshLine}
           onClick={() => void load()}
           disabled={refreshing}
-          aria-label="Refresh session files"
+          aria-label="Refresh files"
           title="Refresh"
           className="shrink-0"
         />

frontend/components/chat/desktop-pane.tsx

@@ -38,12 +38,12 @@ export const DESKTOP_PROBE_MAX_DELAY = 2_000;
 /** Product copy for one readiness probe answer. A sandbox image that lacks the
  *  desktop binaries never becomes ready, so name them instead of waiting. */
 export function desktopProbeStatus(status: number, error: string | null): string {
-  if (status === 409) return "No active sandbox. Send a message to start one.";
+  if (status === 409) return "Nothing is running yet. Send a message to start one.";
   const missing = /missing desktop binaries:\s*(.+)$/i.exec(error ?? "")?.[1]?.trim();
   if (missing) {
-    return `Browser is unavailable on this sandbox image: it is missing ${missing.split(/\s+/).join(", ")}. Rebuild the image with those packages to enable it.`;
+    return `The browser is not available here: it is missing ${missing.split(/\s+/).join(", ")}. Rebuild the environment with those packages to enable it.`;
   }
-  return "Starting sandbox desktop…";
+  return "Starting the browser…";
 }
 
 export function nextDesktopProbeDelay(previous: number | null): number {
@@ -151,7 +151,7 @@ export function DesktopPane({
   const [frameKey, setFrameKey] = useState(0);
   const [inputCaptured, setInputCaptured] = useState(false);
   const [viewerOpen, setViewerOpen] = useState(false);
-  const [status, setStatus] = useState("No active sandbox. Send a message to start one.");
+  const [status, setStatus] = useState("Nothing is running yet. Send a message to start one.");
   // The Agent Screen stage: the frame plus, while expanded, the viewer chrome.
   // Pointer and focus activity inside it never releases captured input.
   const surfaceRef = useRef<HTMLDivElement>(null);
@@ -177,7 +177,7 @@ export function DesktopPane({
     setFrameConnected(false);
     inputCapturedRef.current = false;
     setInputCaptured(false);
-    setStatus("No active sandbox. Send a message to start one.");
+    setStatus("Nothing is running yet. Send a message to start one.");
 
     const probe = async (): Promise<void> => {
       try {
@@ -198,7 +198,7 @@ export function DesktopPane({
         );
       } catch {
         if (cancelled) return;
-        setStatus("Reconnecting to sandbox desktop…");
+        setStatus("Reconnecting…");
       }
       delay = nextDesktopProbeDelay(delay);
       retry = setTimeout(() => void probe(), delay);
@@ -349,7 +349,6 @@ export function DesktopPane({
           <Button
             variant="secondary"
             size="small"
-            aria-label="Control sandbox desktop"
             aria-pressed={inputCaptured}
             disabled={!connected}
             onClick={inputCaptured ? releaseCapture : captureInput}
@@ -364,7 +363,7 @@ export function DesktopPane({
               key={frameKey}
               ref={frameRef}
               data-testid="desktop-frame"
-              title="Sandbox desktop"
+              title="Browser"
               src={src}
               sandbox={DESKTOP_FRAME_SANDBOX}
               tabIndex={-1}

frontend/components/chat/desktop-screen-state.test.tsx

@@ -87,10 +87,10 @@ describe("agent screen card", () => {
     const html = render(false, {
       status: "loading",
       loading: true,
-      loadingCaption: "No active sandbox. Send a message to start one.",
+      loadingCaption: "Nothing is running yet. Send a message to start one.",
     });
     expect(html).toContain("Connecting to agent's screen");
-    expect(html).toContain("No active sandbox. Send a message to start one.");
+    expect(html).toContain("Nothing is running yet. Send a message to start one.");
     expect(html).toContain('data-status="loading"');
     // Nothing to open into yet: the connecting card offers no Open control.
     expect(html).not.toContain('aria-label="Open Nova's screen"');

frontend/components/chat/desktop-surface.test.ts

@@ -62,7 +62,7 @@ describe("Desktop product surface", () => {
 
     expect(desktopPane).toContain(`\`/api/desktop-proxy/${threadInterpolation}/ready\``);
     expect(desktopPane).toContain('fetch(readySrc, { cache: "no-store" })');
-    expect(desktopPane).toContain("Starting sandbox desktop…");
+    expect(desktopPane).toContain("Starting the browser…");
     // Retries on bounded exponential backoff, not a fixed one-second interval.
     expect(desktopPane).toContain("delay = nextDesktopProbeDelay(delay)");
     expect(desktopPane).toContain("setTimeout(() => void probe(), delay)");
@@ -129,7 +129,10 @@ describe("Desktop product surface", () => {
     expect(desktopPane).toContain("desktopFrameInteractive({ loaded, captured: inputCaptured })");
     expect(desktopPane).toContain('pointerEvents: frameInteractive ? "auto" : "none"');
     expect(desktopPane).toContain("interactive={frameInteractive}");
-    expect(desktopPane).toContain('aria-label="Control sandbox desktop"');
+    // The control button has no fixed aria-label: its visible text (Take
+    // control / Release control) is its accessible name.
+    expect(desktopPane).not.toContain('aria-label="Control sandbox desktop"');
+    expect(desktopPane).toContain('inputCaptured ? "Release control" : "Take control"');
     expect(desktopPane).toContain('window.addEventListener("focusin", releaseDesktopInput, true)');
     expect(desktopPane).toContain(
       'window.addEventListener("pointerdown", releaseDesktopInput, true)',
@@ -302,7 +305,7 @@ describe("Desktop probe copy", () => {
     expect(
       desktopProbeStatus(502, "desktop proxy failed: missing desktop binaries: budgie-panel"),
     ).toBe(
-      "Browser is unavailable on this sandbox image: it is missing budgie-panel. Rebuild the image with those packages to enable it.",
+      "The browser is not available here: it is missing budgie-panel. Rebuild the environment with those packages to enable it.",
     );
     expect(
       desktopProbeStatus(
@@ -314,12 +317,12 @@ describe("Desktop probe copy", () => {
 
   test("keeps the waiting and no-sandbox states for every other answer", () => {
     expect(desktopProbeStatus(409, "no live sandbox for this conversation yet")).toBe(
-      "No active sandbox. Send a message to start one.",
+      "Nothing is running yet. Send a message to start one.",
     );
     expect(desktopProbeStatus(502, "desktop proxy failed: connect ECONNREFUSED")).toBe(
-      "Starting sandbox desktop…",
+      "Starting the browser…",
     );
-    expect(desktopProbeStatus(500, null)).toBe("Starting sandbox desktop…");
+    expect(desktopProbeStatus(500, null)).toBe("Starting the browser…");
   });
 
   test("the pane reads the probe body so the copy can be honest", () => {

frontend/components/chat/editor-pane.tsx

@@ -112,7 +112,7 @@ function FileDetail({ entry }: { entry: FileEntry }) {
           filename={entry.base}
           language={langForFile(entry.base)}
           code={entry.content ?? ""}
-          emptyLabel="Content capture lands with the engine event mirror."
+          emptyLabel="This file's contents will show here once the agent saves it."
         />
       </div>
     </div>

frontend/components/chat/interactive-terminal.tsx

@@ -211,8 +211,8 @@ export function InteractiveTerminal({ runId }: { runId: string }) {
             waitingShown = true;
             term?.write(
               idleNoticeSeen
-                ? "\r\n\x1b[2m• no active sandbox - send a message to start one…\x1b[0m\r\n"
-                : "\r\n\x1b[2m• reconnecting to sandbox…\x1b[0m\r\n",
+                ? "\r\n\x1b[2m• nothing is running - send a message to start one…\x1b[0m\r\n"
+                : "\r\n\x1b[2m• reconnecting…\x1b[0m\r\n",
             );
           }
           reconnectTimer = setTimeout(connect, reconnectDelay);

frontend/components/chat/session-rail-tabs.tsx

@@ -48,7 +48,7 @@ export function SessionRailTabs({
   );
   return (
     <PillTabList
-      aria-label="Surface"
+      aria-label="Panels"
       className="min-w-0 flex-1 overflow-x-auto [scrollbar-width:none] [&::-webkit-scrollbar]:hidden"
     >
       {hasSubagents && tab("agents", RiRobot2Line, "Agents")}

frontend/components/chat/session-thread-actions.tsx

@@ -87,8 +87,8 @@ export function SessionThreadActions({
           iconOnly
           leadingIcon={RiLayoutRightLine}
           onClick={onOpenSurfaces}
-          title="Open surfaces panel"
-          aria-label="Open surfaces panel"
+          title="Open side panel"
+          aria-label="Open side panel"
           className={cx(RAIL_ICON_BUTTON, !splitTooNarrow && "md:hidden")}
         />
       )}

frontend/components/chat/session-thread-breadcrumb.test.tsx

@@ -52,8 +52,8 @@ test("a bot thread's own crumb is the bot's name", () => {
   expect(html).not.toContain(">Nova: @bot/Nova compare the EU tiers<");
 });
 
-test("an ordinary root keeps the compact session label", () => {
+test("an ordinary root keeps the compact thread label", () => {
   expect(renderToStaticMarkup(
     <SessionThreadBreadcrumb relationship={relationship("root", null, "Calendar app")} parent={null} />,
-  )).toContain("Session");
+  )).toContain("Thread");
 });

frontend/components/chat/session-thread-breadcrumb.tsx

@@ -10,7 +10,7 @@ export function SessionThreadBreadcrumb({
   readonly parent: ThreadRelationship | null;
 }) {
   if (!relationship?.parentThreadId) {
-    return <span className="text-mono-label text-text-tertiary">Session</span>;
+    return <span className="text-mono-label text-text-tertiary">Thread</span>;
   }
   // Two truncated titles read as near-duplicates ("@bot/Nova compare..." /
   // "Nova: @bot/Nova compare..."), so the parent crumb is a fixed word carrying

frontend/components/chat/session-view.tsx

@@ -730,7 +730,7 @@ export function SessionView({ initialThread, initialOutline = null, initialRelat
             )}
             resourceMentions={!isProductChild}
             composerLocked={composerRelationshipBlocked || readOnlyMessage !== undefined}
-            composerLockedMessage={readOnlyMessage ?? "Verifying child session…"}
+            composerLockedMessage={readOnlyMessage ?? "Verifying this thread…"}
             onTurnsNeeded={initialOutline ? handleTurnsNeeded : undefined}
             productChildren={productChildren}
             onOpenProductChild={openProductChild}
@@ -773,7 +773,7 @@ export function SessionView({ initialThread, initialOutline = null, initialRelat
         {railOpen && sheetSurfacesOpen && (
           <button
             type="button"
-            aria-label="Close surfaces panel"
+            aria-label="Close side panel"
             onClick={() => setRailOverride(false)}
             className={cx(
               "fixed inset-0 z-40 bg-black/50 backdrop-blur-sm",
@@ -873,7 +873,7 @@ export function SessionView({ initialThread, initialOutline = null, initialRelat
               {/* On the sheet a single Close X replaces Expand/Collapse. */}
               <CloseButton
                 size="md"
-                aria-label="Close surfaces panel"
+                aria-label="Close side panel"
                 onClick={() => setRailOverride(false)}
                 className={cx(RAIL_ICON_BUTTON, !splitTooNarrow && "md:hidden")}
               />

frontend/components/chat/subagent-pane-body.test.tsx

@@ -46,7 +46,7 @@ describe("run peek body", () => {
   ])("renders a %s as a session without child controls", (_name, initialRun) => {
     const html = renderToStaticMarkup(<LoadedPane initialRun={initialRun} />);
 
-    expect(html).toContain(">Session<");
+    expect(html).toContain(">Thread<");
     expect(html).toContain('href="/session/root"');
     expect(html).toContain("Open thread");
     expect(html).not.toContain(">Subagent<");
@@ -64,7 +64,7 @@ describe("run peek body", () => {
   });
 
   test("loading and error shells are neutral unless the caller knows it is a child", () => {
-    expect(renderToStaticMarkup(<PaneStub>Loading</PaneStub>)).toContain(">Session<");
+    expect(renderToStaticMarkup(<PaneStub>Loading</PaneStub>)).toContain(">Thread<");
     expect(renderToStaticMarkup(<PaneStub label="Run">Loading</PaneStub>)).toContain(">Run<");
     expect(renderToStaticMarkup(<PaneStub childSession>Loading</PaneStub>)).toContain(
       ">Subagent<",

frontend/components/chat/subagent-pane-body.tsx

@@ -143,7 +143,7 @@ export function LoadedPane({ initialRun }: { initialRun: ApiRun }) {
         <div className="min-w-0 flex-1">
           <div className="flex items-center gap-1.5">
             <span className="text-mono-label text-text-tertiary">
-              {childSession ? "Subagent" : "Session"}
+              {childSession ? "Subagent" : "Thread"}
             </span>
             <span className="text-text-tertiary">·</span>
             <span className="text-mono-label text-text-tertiary">

frontend/components/chat/subagent-pane.tsx

@@ -107,7 +107,7 @@ export function PaneStub({
     <>
       <header className="border-border-button-default flex shrink-0 items-center gap-2 border-b px-4 py-3">
         <span className="text-mono-label text-text-tertiary">
-          {label ?? (childSession ? "Subagent" : "Session")}
+          {label ?? (childSession ? "Subagent" : "Thread")}
         </span>
         <span className="ml-auto" />
         <CloseButton />
@@ -155,7 +155,7 @@ export function SubagentPane() {
   return createPortal(
     <aside
       aria-hidden={!open}
-      aria-label={`${target?.childSession ? "Subagent" : "Session"} pane`}
+      aria-label={`${target?.childSession ? "Subagent" : "Thread"} pane`}
       className={cn(
         "border-border-button-default bg-background-primary-default shadow-sidebar fixed inset-y-0 right-0 z-40 flex h-dvh w-[440px] max-w-[92vw] flex-col border-l",
         "transition-transform duration-300 ease-out",

frontend/components/chat/surface-chooser.tsx

@@ -78,7 +78,7 @@ const SURFACES: readonly SurfaceOption[] = [
 export function railTabLabelFor(
   railTab: SurfaceChoice | "editor" | "workspace" | null,
 ): string {
-  if (railTab === null) return "Surface";
+  if (railTab === null) return "Panels";
   const labels = {
     agents: "Agents",
     artifacts: "Files",
@@ -114,7 +114,7 @@ export function SurfaceChooser({
   return (
     <div className="flex h-full justify-center overflow-y-auto px-6 py-10">
       <div className="w-full max-w-md">
-        <h2 className="sr-only">Open a surface</h2>
+        <h2 className="sr-only">Open a panel</h2>
         {facts.length > 0 && (
           <ul className="mb-6 flex flex-wrap gap-1.5" aria-label="This thread">
             {facts.map((fact) => (

frontend/components/chat/terminal-pane.test.tsx

@@ -100,8 +100,8 @@ describe("TerminalPane log", () => {
     expect(html).not.toContain("terminal-log-working");
   });
 
-  test("empty log reads as booting while live, idle when settled", () => {
-    expect(render([], true)).toContain("Booting session");
+  test("empty log reads as starting while live, idle when settled", () => {
+    expect(render([], true)).toContain("Starting up");
     expect(render([], false)).toContain("No commands were run.");
     // A boot-phase live run with zero commands does not also show the footer.
     expect(render([], true)).not.toContain("terminal-log-working");

frontend/components/chat/terminal-pane.tsx

@@ -114,7 +114,7 @@ export const TerminalPane = memo(function TerminalPane({
       >
         {entries.length === 0 ? (
           <p className="text-static-white/50" data-testid="terminal-log-empty">
-            {live ? "Booting session…" : "No commands were run."}
+            {live ? "Starting up…" : "No commands were run."}
           </p>
         ) : (
           <>

frontend/components/shell/unified-shell-contract.test.ts

@@ -293,12 +293,12 @@ describe("unified shell contract", () => {
     expect(sidebarFrame).toContain("<UserMenu");
   });
 
-  test("provides a direct Open a surface chooser for the right inspector", () => {
+  test("provides a direct Open a panel chooser for the right inspector", () => {
     const sessionView = readFromFrontend("components/chat/session-view.tsx");
     const chooser = readFromFrontend("components/chat/surface-chooser.tsx");
 
     expect(sessionView).toContain("<SurfaceChooser");
-    expect(chooser).toContain("Open a surface");
+    expect(chooser).toContain("Open a panel");
     for (const label of ["Browser", "Terminal", "Files", "Diff", "Agents"]) {
       expect(chooser).toContain(label);
     }