Merge remote-tracking branch 'origin/main' into lento-sonata

Below 860px the layout no longer grows a second navigation surface. The
pane pill strip is gone, the tab bar stays collapsed however many tabs
exist, and opening or spawning takes over the current pane instead of
splitting beside it or opening a tab. The sidebar drawer is the only way
to move between sessions.

The tree itself is untouched, so a desktop-built layout comes back when
the window widens again.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/maestro-daemon/src/tmux.rs

@@ -273,7 +273,7 @@ impl Tmux {
                 "-t",
                 &name,
                 "-F",
-                "#{cursor_x} #{cursor_y} #{pane_height} #{alternate_on} #{cursor_flag}",
+                SCREEN_GEOMETRY_FORMAT,
                 ";",
                 "capture-pane",
                 "-p",
@@ -515,6 +515,52 @@ fn new_session_args(
 /// frame huge.
 const CAPTURE_HISTORY_LINES: usize = 300;
 
+/// `display-message -F` request behind [`parse_screen_geometry`]. tmux expands
+/// a name it does not know to the empty string rather than failing, so a field
+/// missing on an older tmux shifts everything after it — hence the parser keys
+/// the optional tail off the field count.
+const SCREEN_GEOMETRY_FORMAT: &str = concat!(
+    "#{cursor_x} #{cursor_y} #{pane_height} #{alternate_on} #{cursor_flag} ",
+    "#{mouse_standard_flag} #{mouse_button_flag} #{mouse_all_flag} ",
+    "#{mouse_utf8_flag} #{mouse_sgr_flag}",
+);
+
+/// Field count of [`SCREEN_GEOMETRY_FORMAT`]; fewer means an older tmux did not
+/// know one of the names, and the mouse tail cannot be trusted by position.
+const SCREEN_GEOMETRY_FIELDS: usize = 10;
+
+/// Mouse-reporting modes a pane has turned on. A full-screen program sets these
+/// once, at startup, so a client attaching later never sees the sequences —
+/// [`render_screen_snapshot`] replays them.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+struct MouseModes {
+    /// `?1000` — report button press and release.
+    standard: bool,
+    /// `?1002` — also report motion while a button is held.
+    button: bool,
+    /// `?1003` — report all motion.
+    all: bool,
+    /// `?1005` — UTF-8 coordinates (superseded by SGR, still replayed if on).
+    utf8: bool,
+    /// `?1006` — SGR-encoded coordinates.
+    sgr: bool,
+}
+
+impl MouseModes {
+    /// DECSET parameters to re-enable these modes, private-mode order.
+    fn decset_params(self) -> impl Iterator<Item = u16> {
+        [
+            (self.standard, 1000),
+            (self.button, 1002),
+            (self.all, 1003),
+            (self.utf8, 1005),
+            (self.sgr, 1006),
+        ]
+        .into_iter()
+        .filter_map(|(on, param)| on.then_some(param))
+    }
+}
+
 /// Cursor position and screen geometry of a pane, from `display-message`.
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 struct ScreenGeometry {
@@ -523,17 +569,31 @@ struct ScreenGeometry {
     pane_height: usize,
     alternate: bool,
     cursor_visible: bool,
+    mouse: MouseModes,
 }
 
 fn parse_screen_geometry(s: &str) -> Option<ScreenGeometry> {
     let line = s.lines().next()?;
-    let mut it = line.split_whitespace();
-    let cursor_x = it.next()?.parse().ok()?;
-    let cursor_y = it.next()?.parse().ok()?;
-    let pane_height: usize = it.next()?.parse().ok()?;
-    let alternate = it.next()? == "1";
+    let fields: Vec<&str> = line.split_whitespace().collect();
+    let cursor_x = fields.first()?.parse().ok()?;
+    let cursor_y = fields.get(1)?.parse().ok()?;
+    let pane_height: usize = fields.get(2)?.parse().ok()?;
+    let alternate = *fields.get(3)? == "1";
     // Older tmux without `cursor_flag` just means "assume visible".
-    let cursor_visible = it.next().map(|f| f == "1").unwrap_or(true);
+    let cursor_visible = fields.get(4).map(|f| *f == "1").unwrap_or(true);
+    // Only trust the mouse tail when every field expanded; a short line means
+    // some name is unknown here and the remaining ones sit at other offsets.
+    let mouse = if fields.len() >= SCREEN_GEOMETRY_FIELDS {
+        MouseModes {
+            standard: fields[5] == "1",
+            button: fields[6] == "1",
+            all: fields[7] == "1",
+            utf8: fields[8] == "1",
+            sgr: fields[9] == "1",
+        }
+    } else {
+        MouseModes::default()
+    };
     if pane_height == 0 {
         return None;
     }
@@ -543,6 +603,7 @@ fn parse_screen_geometry(s: &str) -> Option<ScreenGeometry> {
         pane_height,
         alternate,
         cursor_visible,
+        mouse,
     })
 }
 
@@ -572,6 +633,12 @@ fn render_screen_snapshot(lines: &[&str], geom: ScreenGeometry) -> Vec<u8> {
     if geom.alternate {
         out.extend_from_slice(b"\x1b[?1049h");
     }
+    // Mouse reporting is set up once, before this client existed. Without it
+    // the client cannot tell a mouse-driven app from a plain alternate screen,
+    // and its wheel and touch gestures have nowhere to go.
+    for param in geom.mouse.decset_params() {
+        out.extend_from_slice(format!("\x1b[?{param}h").as_bytes());
+    }
     out.extend_from_slice(b"\x1b[H\x1b[2J\x1b[m");
     for (i, line) in lines[..=last].iter().enumerate() {
         if i > 0 {
@@ -645,7 +712,7 @@ mod tests {
 
     #[test]
     fn parse_screen_geometry_reads_cursor_and_alternate_flag() {
-        let g = parse_screen_geometry("12 3 40 1 0\n").unwrap();
+        let g = parse_screen_geometry("12 3 40 1 0 0 1 0 0 1\n").unwrap();
         assert_eq!(
             g,
             ScreenGeometry {
@@ -654,6 +721,11 @@ mod tests {
                 pane_height: 40,
                 alternate: true,
                 cursor_visible: false,
+                mouse: MouseModes {
+                    button: true,
+                    sgr: true,
+                    ..MouseModes::default()
+                },
             }
         );
         let g = parse_screen_geometry("0 0 24 0").unwrap();
@@ -663,6 +735,31 @@ mod tests {
         assert!(parse_screen_geometry("garbage").is_none());
     }
 
+    /// A tmux that does not know one of the mouse names expands it to nothing,
+    /// so the tail is one field short and every flag in it has slid. Reading it
+    /// by position would claim modes the pane never set.
+    #[test]
+    fn parse_screen_geometry_drops_a_short_mouse_tail() {
+        let g = parse_screen_geometry("0 0 24 1 1 0 0 1 1").unwrap();
+        assert_eq!(g.mouse, MouseModes::default());
+    }
+
+    #[test]
+    fn mouse_modes_map_to_private_mode_parameters() {
+        let all = MouseModes {
+            standard: true,
+            button: true,
+            all: true,
+            utf8: true,
+            sgr: true,
+        };
+        assert_eq!(
+            all.decset_params().collect::<Vec<_>>(),
+            vec![1000, 1002, 1003, 1005, 1006]
+        );
+        assert_eq!(MouseModes::default().decset_params().count(), 0);
+    }
+
     #[test]
     fn snapshot_clears_prints_lines_and_parks_the_cursor() {
         // Two scrollback lines, then a 3-row screen with the cursor on row 1.
@@ -675,6 +772,7 @@ mod tests {
                 pane_height: 3,
                 alternate: false,
                 cursor_visible: true,
+                mouse: MouseModes::default(),
             },
         );
         let out = String::from_utf8(out).unwrap();
@@ -695,6 +793,7 @@ mod tests {
                 pane_height: 3,
                 alternate: true,
                 cursor_visible: false,
+                mouse: MouseModes::default(),
             },
         );
         let out = String::from_utf8(out).unwrap();
@@ -716,12 +815,40 @@ mod tests {
                 pane_height: 3,
                 alternate: false,
                 cursor_visible: true,
+                mouse: MouseModes::default(),
             },
         ))
         .unwrap();
         assert_eq!(out, "\x1b[H\x1b[2J\x1b[mtext\x1b[m\r\x1b[4C");
     }
 
+    /// A client attaching to a running full-screen app never saw it turn mouse
+    /// reporting on, so the snapshot has to. Without this the client reads the
+    /// pane as a plain alternate screen and its scroll gestures go nowhere.
+    #[test]
+    fn snapshot_replays_the_panes_mouse_modes() {
+        let out = String::from_utf8(render_screen_snapshot(
+            &["app"],
+            ScreenGeometry {
+                cursor_x: 0,
+                cursor_y: 0,
+                pane_height: 1,
+                alternate: true,
+                cursor_visible: true,
+                mouse: MouseModes {
+                    button: true,
+                    sgr: true,
+                    ..MouseModes::default()
+                },
+            },
+        ))
+        .unwrap();
+        assert!(
+            out.starts_with("\x1b[?1049h\x1b[?1002h\x1b[?1006h\x1b[H\x1b[2J"),
+            "{out:?}"
+        );
+    }
+
     /// Every phrasing must be recognised: an unmatched one makes
     /// `list_sessions` fail, and a failed pass reaps nothing.
     #[test]

crates/maestro-daemon/tests/session_manager.rs

@@ -246,6 +246,59 @@ async fn attach_replay_is_the_current_screen_not_the_byte_tail() {
     fx.manager.kill(s.id, false).await.unwrap();
 }
 
+/// A full-screen app turns mouse reporting on once, at startup. A client that
+/// attaches later never sees those sequences, so it reads the pane as a plain
+/// alternate screen and its wheel and touch gestures have nowhere to go. The
+/// snapshot must carry the pane's mouse modes with it.
+#[tokio::test]
+async fn attach_replay_carries_the_panes_mouse_modes() {
+    let fx = DaemonFixture::new();
+    let cwd = TempDir::new().unwrap();
+
+    let s = fx
+        .manager
+        .create(CreateSessionRequest {
+            cwd: cwd.path().to_path_buf(),
+            // Alternate screen, then button-event tracking (?1002) with SGR
+            // coordinates (?1006) — what tmux and agent TUIs actually request.
+            command: "sh -c 'printf \"\\\\033[?1049h\\\\033[?1002h\\\\033[?1006h\\\\033[2J\\\\033[HMOUSE_MARKER\"; exec sleep 30'"
+                .into(),
+            env: HashMap::new(),
+            metadata: HashMap::new(),
+            worktree: None,
+        })
+        .await
+        .expect("create");
+
+    let want = b"MOUSE_MARKER";
+    let deadline = std::time::Instant::now() + Duration::from_secs(5);
+    let mut replay = Vec::new();
+    while std::time::Instant::now() < deadline {
+        let (bytes, _rx) = fx
+            .manager
+            .subscribe_pty_with_replay(s.id)
+            .await
+            .expect("subscribe");
+        replay = bytes;
+        if replay.windows(want.len()).any(|w| w == want) {
+            break;
+        }
+        tokio::time::sleep(Duration::from_millis(50)).await;
+    }
+
+    let text = String::from_utf8_lossy(&replay).into_owned();
+    assert!(
+        text.contains("MOUSE_MARKER"),
+        "replay never reached the live screen: {text:?}"
+    );
+    assert!(
+        replay.starts_with(b"\x1b[?1049h\x1b[?1002h\x1b[?1006h\x1b[H\x1b[2J"),
+        "replay dropped the pane's mouse modes: {text:?}"
+    );
+
+    fx.manager.kill(s.id, false).await.unwrap();
+}
+
 /// Regression for NAP-228: after `recover`, PTY output must reach new
 /// subscribers. Before the fix tmux's stale `pipe-pane` (with `-o`) silently
 /// kept feeding the old FIFO and the revived manager's subscribers saw

flake.nix

@@ -125,7 +125,7 @@
             pnpmDeps = (pkgs.fetchPnpmDeps.override { pnpm = pkgs.pnpm_10; }) {
               inherit (finalAttrs) pname version src;
               fetcherVersion = 3;
-              hash = "sha256-D9JdgI92vzAY8en2zGEEPd4hwOLVi3sr1joT4b17Be4=";
+              hash = "sha256-AvIrpXipbcp7hRujh/L4UAc6tAJOxe67P/iji6L/oL0=";
             };
 
             buildPhase = ''

web/src/attach.ts

@@ -6,6 +6,7 @@ import { attachWsUrl } from "./routes.js";
 import { escapeHtml } from "./html.js";
 import { INITIAL_RECONNECT_MS, MAX_RECONNECT_MS } from "./reconnect.js";
 import { applyModsToChar, cursorSeq } from "./keys.js";
+import { splitCommand, toolIconSvg } from "./toolIcon.js";
 import type { ClientControl, Uuid } from "./types.js";
 
 /**
@@ -54,6 +55,15 @@ export interface AttachInfo {
   command: string;
 }
 
+/** Header echoes the sidebar: the command's leading program becomes its tool
+ * icon when we have a mark for it, remaining words stay as text. */
+function commandFragment(command: string): string {
+  const { tool, rest } = splitCommand(command);
+  const icon = tool ? toolIconSvg(tool) : null;
+  const text = icon ? rest : command;
+  return `<span class="at-cmd">${icon ?? ""}${text ? escapeHtml(text) : ""}</span>`;
+}
+
 export function createAttachConnection(
   sessionId: Uuid,
   opts: AttachOptions = {},
@@ -65,9 +75,7 @@ export function createAttachConnection(
   // tooltip for when you really need it.
   const titleHtml = info
     ? `<span class="at-name">${escapeHtml(info.name)}</span>` +
-      (info.command && info.command !== info.name
-        ? `<span class="at-cmd">${escapeHtml(info.command)}</span>`
-        : "")
+      (info.command && info.command !== info.name ? commandFragment(info.command) : "")
     : `session <span class="sid">${escapeHtml(sessionId.slice(0, 8))}</span>`;
   const titleAttr = info ? `${info.name} · ${info.command}  (${sessionId})` : sessionId;
   el.innerHTML = `

web/src/multiview.test.ts

@@ -432,3 +432,94 @@ describe("multiview closeSession tab cleanup (#137)", () => {
     expect(layout.activeTabId).toBe(tab.id);
   });
 });
+
+describe("multiview mobile single pane", () => {
+  /** Force the mobile media query on, whatever happy-dom's viewport says. */
+  function forceMobile(): void {
+    vi.spyOn(window, "matchMedia").mockImplementation(
+      (query: string) =>
+        ({
+          matches: query.includes("859"),
+          media: query,
+          onchange: null,
+          addEventListener() {},
+          removeEventListener() {},
+          addListener() {},
+          removeListener() {},
+          dispatchEvent: () => false,
+        }) as unknown as MediaQueryList,
+    );
+  }
+
+  beforeEach(() => {
+    stubFetch();
+    forceMobile();
+    document.body.replaceChildren();
+  });
+
+  afterEach(() => {
+    vi.unstubAllGlobals();
+    vi.restoreAllMocks();
+  });
+
+  it("replaces the focused pane instead of splitting beside it", () => {
+    const layout = emptyLayout();
+    const tab = layout.tabs[0];
+    tab.focusedLeafId = splitLeaf(tab, "", "s1", "row", true);
+    const mv = makeMv(layout);
+    document.body.appendChild(mv.el);
+    mv.render();
+
+    mv.openSessionBeside("s2");
+
+    const ls = leaves(tab.root);
+    expect(ls).toHaveLength(1);
+    expect(ls[0].sessionId).toBe("s2");
+    expect(layout.tabs).toHaveLength(1);
+  });
+
+  it("keeps a spawn draft in the current pane rather than a new tab", async () => {
+    const layout = emptyLayout();
+    const tab = layout.tabs[0];
+    tab.focusedLeafId = splitLeaf(tab, "", "s1", "row", true);
+    const mv = makeMv(layout);
+    document.body.appendChild(mv.el);
+    mv.render();
+
+    mv.openDraft(undefined, { newTab: true });
+    await flush();
+
+    expect(layout.tabs).toHaveLength(1);
+    const ls = leaves(tab.root);
+    expect(ls).toHaveLength(1);
+    expect(ls[0].sessionId).toBeNull();
+    expect(ls[0].draft).not.toBeNull();
+  });
+
+  it("renders one pane and no pane pills for a multi-leaf tab", () => {
+    const layout = emptyLayout();
+    const tab = layout.tabs[0];
+    const first = splitLeaf(tab, "", "s1", "row", true);
+    tab.focusedLeafId = splitLeaf(tab, first, "s2", "row", true);
+    const mv = makeMv(layout);
+    document.body.appendChild(mv.el);
+    mv.render();
+
+    expect(mv.el.querySelectorAll(".mv-pane")).toHaveLength(1);
+    expect(mv.el.querySelector(".mv-panebar")).toBeNull();
+    expect(mv.el.querySelector(".mv-pill")).toBeNull();
+  });
+
+  it("collapses the tab bar even with several tabs", () => {
+    const layout = emptyLayout();
+    const first = layout.tabs[0];
+    first.focusedLeafId = splitLeaf(first, "", "s1", "row", true);
+    const second = addTab(layout);
+    second.focusedLeafId = splitLeaf(second, "", "s2", "row", true);
+    const mv = makeMv(layout);
+    document.body.appendChild(mv.el);
+    mv.render();
+
+    expect(mv.el.classList.contains("mv-mobile-solo")).toBe(true);
+  });
+});

web/src/multiview.ts

@@ -84,9 +84,11 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
   canvas.className = "mv-canvas";
   el.append(tabBar, canvas);
 
-  // Mobile (issue #35): below 860px the tree projects to a one-pane-at-a-time
-  // strip of pills — splits/drag/resize are desktop-only. The tree is untouched,
-  // so widening restores the splits.
+  // Mobile (issue #35): below 860px the layout collapses to exactly one visible
+  // pane and no tab bar — splits/drag/resize are desktop-only, and opening or
+  // spawning replaces the pane rather than adding a second thing to navigate.
+  // The sidebar drawer is the only navigation. The tree is untouched, so
+  // widening restores whatever splits and tabs a desktop session built.
   const mq = window.matchMedia("(max-width: 859px)");
   let isMobile = mq.matches;
   mq.addEventListener("change", (e) => {
@@ -391,7 +393,9 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
       return;
     }
     const target = findLeaf(tab.root, tab.focusedLeafId)!;
-    if (!target.sessionId) {
+    // Mobile shows one pane, so there is no "beside": take over the pane. The
+    // evicted session keeps running and stays a tap away in the sidebar.
+    if (!target.sessionId || isMobile) {
       target.sessionId = sessionId;
       target.draft = null;
     } else {
@@ -403,7 +407,9 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
 
   function openDraft(seed?: Partial<Draft>, opts?: { newTab?: boolean }): void {
     const draft = (): Draft => ({ command: "", cwd: "", name: "", ...seed });
-    if (opts?.newTab) {
+    // Mobile keeps a single tab and a single pane: the spawn form takes over the
+    // current pane instead of opening a tab or a split.
+    if (opts?.newTab && !isMobile) {
       // Spawn opens its own tab rather than halving whatever you were reading
       // (#100). The empty-pane reuse below still applies within a tab.
       const fresh = addTab(layout);
@@ -421,9 +427,10 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
       return;
     }
     const target = findLeaf(tab.root, tab.focusedLeafId)!;
-    if (!target.sessionId) {
+    if (!target.sessionId || isMobile) {
       // Empty = no session, not `!draft` (#72): the mounted form auto-syncs
       // picked defaults into `draft` once ready, so that's never reliably null.
+      target.sessionId = null;
       target.draft = draft();
       const stale = draftForms.get(target.id);
       if (stale) {
@@ -462,9 +469,9 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
     renderTabs();
     canvas.replaceChildren();
     const tab = activeTab(layout);
-    // Mobile single-tab: the tab bar carries no information (one tab, one pane),
-    // so CSS collapses it and we float a ☰ instead (rendered in renderMobile).
-    el.classList.toggle("mv-mobile-solo", isMobile && layout.tabs.length === 1);
+    // Mobile: the tab bar is a second navigation surface we don't want, so CSS
+    // collapses it; the header ☰ keeps the sidebar drawer reachable.
+    el.classList.toggle("mv-mobile-solo", isMobile);
 
     if (!tab.root) {
       pruneForms(tab);
@@ -496,7 +503,9 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
     persist();
   }
 
-  // Mobile: a pill strip of the active tab's leaves + one full-screen pane.
+  // Mobile: the focused leaf, full screen, alone. Panes a desktop session left
+  // behind stay in the tree but are reached only by tapping the session in the
+  // sidebar drawer — mobile shows no pane switcher of its own.
   function renderMobile(tab: { root: Node | null; focusedLeafId: string | null }): void {
     const ls = leaves(tab.root);
     const focused = (tab.focusedLeafId && findLeaf(tab.root, tab.focusedLeafId)) || ls[0];
@@ -504,23 +513,6 @@ export function createMultiView(opts: MultiViewOptions): MultiView {
     const wrap = document.createElement("div");
     wrap.className = "mv-mobile";
 
-    if (ls.length > 1) {
-      const bar = document.createElement("div");
-      bar.className = "mv-panebar";
-      for (const l of ls) {
-        const pill = document.createElement("button");
-        pill.type = "button";
-        pill.className = "mv-pill" + (l.id === focused.id ? " is-active" : "");
-        pill.textContent = l.sessionId ? (infoFor(l.sessionId)?.name ?? l.sessionId.slice(0, 8)) : "empty";
-        pill.addEventListener("click", () => {
-          tab.focusedLeafId = l.id;
-          render();
-        });
-        bar.appendChild(pill);
-      }
-      wrap.appendChild(bar);
-    }
-
     const pane = buildPane(focused);
     pane.el.classList.add("is-focused"); // the only pane — never dimmed
     wrap.appendChild(pane.el);

web/src/styles.css

@@ -1292,6 +1292,9 @@ input.leaf-rename:focus {
 
 .attach-title .at-cmd {
   color: var(--muted);
+  display: inline-flex;
+  align-items: center;
+  gap: 4px;
 }
 
 .attach-title .at-cmd::before {
@@ -2199,8 +2202,8 @@ input.leaf-rename:focus {
   display: flex;
   flex-direction: column;
 }
-/* Mobile, single tab: the tab bar is pure chrome — collapse it (a floating ☰
-   inside the pane keeps the sidebar drawer reachable). */
+/* Mobile: the tab bar is a second navigation surface — collapse it (a floating
+   ☰ inside the pane keeps the sidebar drawer reachable). */
 .mv-mobile-solo > .mv-tabs {
   display: none;
 }
@@ -2479,8 +2482,8 @@ input.leaf-rename:focus {
 }
 
 /* =========================================================================
-   multi-view mobile (#35): below 860px the split tree projects to a pill strip
-   with one pane visible; the sidebar becomes an off-canvas drawer (☰).
+   multi-view mobile (#35): below 860px only the focused pane is shown — no tab
+   bar, no pane switcher; the sidebar drawer (☰) is the navigation.
    ========================================================================= */
 .mv-backdrop {
   display: none;
@@ -2500,32 +2503,6 @@ input.leaf-rename:focus {
   border-radius: 0;
   box-shadow: none;
 }
-.mv-panebar {
-  display: flex;
-  gap: 4px;
-  padding: var(--sp-1) var(--sp-2);
-  overflow-x: auto;
-  scrollbar-width: none;
-  flex: none;
-}
-.mv-pill {
-  display: inline-flex;
-  align-items: center;
-  gap: var(--sp-2);
-  padding: 7px var(--sp-3);
-  border-radius: var(--r-1);
-  background: var(--surface-2);
-  color: var(--muted);
-  font: 600 var(--fs-12) / 1 var(--font-mono);
-  white-space: nowrap;
-  cursor: pointer;
-  border: 1px solid transparent;
-}
-.mv-pill.is-active {
-  background: var(--accent-tint);
-  color: var(--accent-strong);
-  border-color: var(--accent-ring);
-}
 .mv-mobile > .mv-pane {
   flex: 1;
   min-height: 0;

web/src/tree.test.ts

@@ -39,6 +39,16 @@ describe("buildTree", () => {
     expect(names(root)).toEqual(["~/git/naps62/maestro"]);
   });
 
+  it("folds the sole root folder into each of its own children when it branches", () => {
+    const root = buildTree(
+      [session("a", "/home/n/subvisual/bullish"), session("b", "/home/n/tea/maestro")],
+      "/home/n",
+      "",
+    ) as TreeFolder;
+
+    expect(names(root).sort()).toEqual(["~/subvisual/bullish", "~/tea/maestro"]);
+  });
+
   it("stops collapsing where a directory branches", () => {
     const root = buildTree(
       [session("a", "/home/n/git/one"), session("b", "/home/n/git/two")],

web/src/tree.ts

@@ -59,6 +59,15 @@ export function buildTree(sessions: Session[], home: string | undefined, filter:
     for (const c of n.children) if (c.kind === "folder") sortRec(c);
   };
   sortRec(root);
+  // The root's sole child (usually `~`) has no sibling to distinguish it
+  // from, so it folds into every one of its own children, not just a lone
+  // one — unlike the chain merge below, and only here at the very top.
+  if (root.children.length === 1 && root.children[0].kind === "folder") {
+    const only = root.children[0];
+    root.children = only.children.map((c) =>
+      c.kind === "folder" ? { ...c, name: `${only.name}/${c.name}` } : c,
+    );
+  }
   // Collapse linear directory chains so `~/git.naps.pt/naps62/maestro` reads as
   // one compact folder rather than four nested ones.
   root.children = root.children.map((c) => (c.kind === "folder" ? mergeLinear(c) : c));