diff --git a/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.test.js b/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.test.js
index 395c2669cf..8d085c0483 100644
--- a/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.test.js
+++ b/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.test.js
@@ -1,14 +1,96 @@
 import { afterEach, describe, expect, it, vi } from 'vitest';
-import { mount } from '@vue/test-utils';
+import { flushPromises, mount } from '@vue/test-utils';
 import { nextTick } from 'vue';
 import SdTooltip from './SdTooltip.vue';
 
+// jsdom reports 0 for offset/client sizes; mock the accessor so positioning math is actually exercised.
+const metricRestores = [];
+function mockAccessor(target, prop, value) {
+  const prev = Object.getOwnPropertyDescriptor(target, prop);
+  Object.defineProperty(target, prop, { configurable: true, get: () => value });
+  metricRestores.push(() => (prev ? Object.defineProperty(target, prop, prev) : delete target[prop]));
+}
+
+async function openTooltipWithTriggerRect(rect) {
+  const wrapper = mount(SdTooltip, {
+    attachTo: document.body,
+    props: { delay: 0, duration: 0 },
+    slots: { trigger: '<button type="button">Bold</button>', default: 'Bold' },
+  });
+  const trigger = wrapper.find('.sd-tooltip-trigger').element;
+  trigger.getBoundingClientRect = () => ({ ...rect, x: rect.left, y: rect.top, toJSON() {} });
+  await wrapper.find('.sd-tooltip-trigger').trigger('mouseenter');
+  await flushPromises();
+  await nextTick();
+  return document.body.querySelector('.sd-tooltip-content');
+}
+
 describe('SdTooltip', () => {
   afterEach(() => {
+    metricRestores.splice(0).forEach((restore) => restore());
     vi.useRealTimers();
     document.body.innerHTML = '';
   });
 
+  it('flips below based on the tooltip height, not only when the trigger touches the top', async () => {
+    mockAccessor(HTMLElement.prototype, 'offsetHeight', 40);
+    // above = 30 - 40 - 10 = -20 < gutter → flips below (bottom + 10 = 60).
+    const content = await openTooltipWithTriggerRect({
+      top: 30,
+      bottom: 50,
+      left: 100,
+      right: 140,
+      width: 40,
+      height: 20,
+    });
+    expect(content.style.top).toBe('60px');
+    expect(content.classList.contains('sd-tooltip-content--bottom')).toBe(true);
+  });
+
+  it('clamps horizontally to clientWidth, excluding the window scrollbar', async () => {
+    mockAccessor(HTMLElement.prototype, 'offsetWidth', 100);
+    mockAccessor(document.documentElement, 'clientWidth', 500);
+    // left 450 clamps to clientWidth - width - gutter = 500 - 100 - 8 = 392 (innerWidth stays 1024).
+    const content = await openTooltipWithTriggerRect({
+      top: 500,
+      bottom: 520,
+      left: 480,
+      right: 520,
+      width: 40,
+      height: 20,
+    });
+    expect(content.style.left).toBe('392px');
+  });
+
+  it('flips below the trigger when there is no room above the viewport top', async () => {
+    const content = await openTooltipWithTriggerRect({
+      top: 5,
+      bottom: 25,
+      left: 100,
+      right: 140,
+      width: 40,
+      height: 20,
+    });
+    expect(content).not.toBeNull();
+    expect(content.style.top).toBe('35px');
+    expect(content.classList.contains('sd-tooltip-content--bottom')).toBe(true);
+  });
+
+  it('stays above the trigger when there is room', async () => {
+    const content = await openTooltipWithTriggerRect({
+      top: 500,
+      bottom: 520,
+      left: 100,
+      right: 140,
+      width: 40,
+      height: 20,
+    });
+    expect(content).not.toBeNull();
+    // contentHeight is 0 in jsdom, so above = top - 0 - 10 = 490.
+    expect(content.style.top).toBe('490px');
+    expect(content.classList.contains('sd-tooltip-content--bottom')).toBe(false);
+  });
+
   it('auto-hides after the configured visible duration', async () => {
     vi.useFakeTimers();
     const wrapper = mount(SdTooltip, {
diff --git a/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue b/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue
index af44e677b4..7fb6ffe6ac 100644
--- a/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue
+++ b/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue
@@ -38,12 +38,17 @@ const isOpen = ref(false);
 const triggerRef = ref(null);
 const contentRef = ref(null);
 const position = ref({ top: '0px', left: '0px' });
+const placement = ref('top');
 
 let closeTimeout = null;
 let openTimeout = null;
 let autoHideTimeout = null;
 
-const mergedContentClass = computed(() => ['sd-tooltip-content', attrs.class]);
+const mergedContentClass = computed(() => [
+  'sd-tooltip-content',
+  `sd-tooltip-content--${placement.value}`,
+  attrs.class,
+]);
 const contentStyle = computed(() => ({
   ...props.contentStyle,
   ...(attrs.style || {}),
@@ -89,14 +94,26 @@ const updatePosition = () => {
   const triggerRect = triggerRef.value.getBoundingClientRect();
   const contentWidth = contentRef.value.offsetWidth;
   const contentHeight = contentRef.value.offsetHeight;
-  const viewportWidth = window.innerWidth || document.documentElement.clientWidth || 0;
+  // clientWidth excludes a window scrollbar, so the tooltip never clamps under it.
+  const viewportWidth = document.documentElement.clientWidth || window.innerWidth || 0;
   const gutter = 8;
+  const offset = 10;
 
   let left = triggerRect.left + triggerRect.width / 2 - contentWidth / 2;
   left = Math.max(gutter, Math.min(left, viewportWidth - contentWidth - gutter));
 
+  // Flip below the trigger when placing above would clip the viewport top.
+  const topAbove = triggerRect.top - contentHeight - offset;
+  let top = topAbove;
+  if (topAbove < gutter) {
+    placement.value = 'bottom';
+    top = triggerRect.bottom + offset;
+  } else {
+    placement.value = 'top';
+  }
+
   position.value = {
-    top: `${triggerRect.top - contentHeight - 10}px`,
+    top: `${top}px`,
     left: `${left}px`,
   };
 };
@@ -255,6 +272,16 @@ onBeforeUnmount(() => {
   transform: translateX(-50%) rotate(45deg);
 }
 
+.sd-tooltip-content--bottom .sd-tooltip-arrow {
+  bottom: auto;
+  top: -5px;
+}
+
+.sd-tooltip-content--bottom.fade-in-scale-up-transition-enter-active,
+.sd-tooltip-content--bottom.fade-in-scale-up-transition-leave-active {
+  transform-origin: top center;
+}
+
 .fade-in-scale-up-transition-enter-active,
 .fade-in-scale-up-transition-leave-active {
   transform-origin: bottom center;