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>

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

@@ -2202,8 +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;
 }
@@ -2482,8 +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;
@@ -2503,32 +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;