diff --git a/packages/shell/src/dom/islands.test.ts b/packages/shell/src/dom/islands.test.ts
index 7e907efa..1fb9f6d0 100644
--- a/packages/shell/src/dom/islands.test.ts
+++ b/packages/shell/src/dom/islands.test.ts
@@ -341,7 +341,10 @@ describe("palette registration", () => {
     const second = fakePalette();
     const unregisterFirst = shell.registerPalette(first);
     shell.registerPalette(second);
-    const observer = FakeResizeObserver.instances[0]!;
+    const observer = FakeResizeObserver.instances.find((candidate) =>
+      candidate.observed.has(second.element),
+    )!;
+    expect(observer).toBeDefined();
     expect(observer.observed.has(first.element)).toBe(false);
     expect(observer.observed.has(second.element)).toBe(true);
     unregisterFirst();
diff --git a/packages/shell/src/dom/mount.test.ts b/packages/shell/src/dom/mount.test.ts
index 17d2a407..cca3c110 100644
--- a/packages/shell/src/dom/mount.test.ts
+++ b/packages/shell/src/dom/mount.test.ts
@@ -190,7 +190,7 @@ describe("destroy", () => {
     shell.inspector?.open();
     shell.setStatus({ severity: "danger", text: "Invalid" }, { delayMs: 800 });
     shell.menu.open();
-    const observer = FakeResizeObserver.instances[0];
+    const observers = [...FakeResizeObserver.instances];
 
     shell.destroy();
     shell.destroy();
@@ -200,7 +200,8 @@ describe("destroy", () => {
     expect(root.getAttributeNames()).toEqual(["id"]);
     expect(root.className).toBe("");
     expect(document.documentElement.className).toBe("");
-    expect(observer?.disconnected).toBe(true);
+    expect(observers.length).toBeGreaterThan(1);
+    expect(observers.every((observer) => observer.disconnected)).toBe(true);
     expect(target.listeners.size).toBe(0);
 
     vi.advanceTimersByTime(2000);
diff --git a/packages/shell/src/dom/tooltip.test.ts b/packages/shell/src/dom/tooltip.test.ts
index 4813a5bc..1fdcb382 100644
--- a/packages/shell/src/dom/tooltip.test.ts
+++ b/packages/shell/src/dom/tooltip.test.ts
@@ -2,6 +2,7 @@ import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 import { TOOLTIP_DELAY_MS } from "../core/index.js";
 import {
+  FakeResizeObserver,
   chrome,
   cleanup,
   fakePalette,
@@ -149,6 +150,22 @@ describe("chrome tooltip (guide §5.6)", () => {
     expect(tooltip.style.top).toBe(`${748 - 8 - 28}px`);
   });
 
+  it("is placed again when it grows after showing, for example once a web font arrives", () => {
+    const { root } = mount({}, { width: 1000, height: 800 });
+    const zoom = chrome(root, "zoom");
+    setBox(zoom, { left: 815, top: 748, width: 173, height: 40 });
+    const zoomIn = zoomButton(root, "in");
+    setBox(zoomIn, { left: 950, top: 752, width: 32, height: 32 });
+    const tooltip = tooltipOf(root);
+    Object.defineProperty(tooltip, "offsetWidth", { configurable: true, value: 80 });
+    Object.defineProperty(tooltip, "offsetHeight", { configurable: true, value: 28 });
+    zoomIn.focus();
+    expect(tooltip.style.left).toBe(`${1000 - 12 - 80}px`);
+    Object.defineProperty(tooltip, "offsetWidth", { configurable: true, value: 82 });
+    FakeResizeObserver.resize(tooltip);
+    expect(tooltip.style.left).toBe(`${1000 - 12 - 82}px`);
+  });
+
   it("describes a control only when it says more than the control's name", () => {
     const { shell, root } = mount({ problems: { onActivate() {} } });
     shell.setProblems({ count: 2, errors: 1 });
diff --git a/packages/shell/src/dom/tooltip.ts b/packages/shell/src/dom/tooltip.ts
index 8514aa72..39492661 100644
--- a/packages/shell/src/dom/tooltip.ts
+++ b/packages/shell/src/dom/tooltip.ts
@@ -43,6 +43,15 @@ export function createTooltip({ root, layer, id }: TooltipContext): TooltipContr
   // A clicked control keeps its tooltip hidden until the pointer leaves it.
   let pressed: HTMLElement | undefined;
   const detachers = new Set<() => void>();
+  // The tooltip grows when a web font arrives after it was placed; place it again so it keeps
+  // its edge distance instead of running past the container.
+  const resizeObserver =
+    typeof ResizeObserver === "function"
+      ? new ResizeObserver(() => {
+          if (shown) place(shown.control);
+        })
+      : undefined;
+  resizeObserver?.observe(element);
 
   function cancelPending(): void {
     if (pending) clearTimeout(pending.timer);
@@ -231,6 +240,7 @@ export function createTooltip({ root, layer, id }: TooltipContext): TooltipContr
     destroy() {
       hide();
       for (const detach of [...detachers]) detach();
+      resizeObserver?.disconnect();
       element.remove();
     },
   };