diff --git a/web/src/multiview.test.ts b/web/src/multiview.test.ts
index 012693e..4e9a8de 100644
--- a/web/src/multiview.test.ts
+++ b/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);
+  });
+});
diff --git a/web/src/multiview.ts b/web/src/multiview.ts
index 3da26a8..1408a05 100644
--- a/web/src/multiview.ts
+++ b/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);
diff --git a/web/src/styles.css b/web/src/styles.css
index 9663809..d73701f 100644
--- a/web/src/styles.css
+++ b/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;