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..e413c9abfc 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
@@ -4,14 +4,32 @@ import { nextTick } from 'vue';
 import SdTooltip from './SdTooltip.vue';
 
 describe('SdTooltip', () => {
+  let mountedWrappers = [];
+
+  // mount() wrapper so afterEach can unmount every instance: SdTooltip registers
+  // window/document listeners while open, and clearing document.body does not
+  // unmount Vue components, so onBeforeUnmount cleanup would never run.
+  const trackedMount = (...args) => {
+    const wrapper = mount(...args);
+    mountedWrappers.push(wrapper);
+    return wrapper;
+  };
+
+  const unmountAll = () => {
+    mountedWrappers.forEach((wrapper) => wrapper.unmount());
+    mountedWrappers = [];
+  };
+
   afterEach(() => {
+    unmountAll();
     vi.useRealTimers();
+    vi.restoreAllMocks();
     document.body.innerHTML = '';
   });
 
   it('auto-hides after the configured visible duration', async () => {
     vi.useFakeTimers();
-    const wrapper = mount(SdTooltip, {
+    const wrapper = trackedMount(SdTooltip, {
       attachTo: document.body,
       props: {
         delay: 0,
@@ -36,4 +54,90 @@ describe('SdTooltip', () => {
     await nextTick();
     expect(document.body.querySelector('.sd-tooltip-content')).toBeNull();
   });
+
+  describe('positioning', () => {
+    const TOOLTIP_WIDTH = 120;
+    const TOOLTIP_HEIGHT = 34;
+
+    const makeRect = ({ top, left, width, height }) => ({
+      top,
+      left,
+      width,
+      height,
+      right: left + width,
+      bottom: top + height,
+      x: left,
+      y: top,
+    });
+
+    // happy-dom does not compute layout: every measurement API returns 0. Geometry is
+    // injected through all of them (offset* and getBoundingClientRect) so the tests do
+    // not depend on which one the component reads.
+    const stubLayout = (triggerRect) => {
+      const isTooltipContent = (el) => el.classList?.contains('sd-tooltip-content');
+      const contentRect = makeRect({ top: 0, left: 0, width: TOOLTIP_WIDTH, height: TOOLTIP_HEIGHT });
+
+      vi.spyOn(HTMLElement.prototype, 'offsetWidth', 'get').mockImplementation(function () {
+        return isTooltipContent(this) ? TOOLTIP_WIDTH : triggerRect.width;
+      });
+      vi.spyOn(HTMLElement.prototype, 'offsetHeight', 'get').mockImplementation(function () {
+        return isTooltipContent(this) ? TOOLTIP_HEIGHT : triggerRect.height;
+      });
+      vi.spyOn(Element.prototype, 'getBoundingClientRect').mockImplementation(function () {
+        return isTooltipContent(this) ? contentRect : triggerRect;
+      });
+    };
+
+    const mountAndOpen = async (triggerRect) => {
+      stubLayout(triggerRect);
+
+      const wrapper = trackedMount(SdTooltip, {
+        attachTo: document.body,
+        props: {
+          delay: 0,
+          duration: 0,
+        },
+        slots: {
+          trigger: '<button type="button">Undo</button>',
+          default: 'Undo',
+        },
+      });
+
+      await wrapper.find('.sd-tooltip-trigger').trigger('mouseenter');
+      await nextTick();
+      await nextTick();
+      return document.body.querySelector('.sd-tooltip-content');
+    };
+
+    const renderedTop = (content) => parseFloat(content.style.top);
+
+    it('renders fully above the trigger when there is room', async () => {
+      const triggerRect = makeRect({ top: 200, left: 300, width: 32, height: 32 });
+      const content = await mountAndOpen(triggerRect);
+
+      expect(renderedTop(content)).toBeGreaterThanOrEqual(0);
+      expect(renderedTop(content) + TOOLTIP_HEIGHT).toBeLessThanOrEqual(triggerRect.top);
+    });
+
+    it('stays inside the viewport and clear of the trigger when the trigger is flush with the top', async () => {
+      const triggerRect = makeRect({ top: 0, left: 100, width: 32, height: 32 });
+      const content = await mountAndOpen(triggerRect);
+
+      expect(renderedTop(content)).toBeGreaterThanOrEqual(0);
+      expect(renderedTop(content)).toBeGreaterThanOrEqual(triggerRect.bottom);
+    });
+
+    // data-placement is the styling contract the component's own CSS uses to orient
+    // the arrow and the transition origin toward the trigger.
+    it('marks the placement so the arrow points at the trigger from either side', async () => {
+      const flushTopRect = makeRect({ top: 0, left: 100, width: 32, height: 32 });
+      expect((await mountAndOpen(flushTopRect)).dataset.placement).toBe('bottom');
+
+      unmountAll();
+      vi.restoreAllMocks();
+
+      const roomyRect = makeRect({ top: 200, left: 300, width: 32, height: 32 });
+      expect((await mountAndOpen(roomyRect)).dataset.placement).toBe('top');
+    });
+  });
 });
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..b84483f559 100644
--- a/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue
+++ b/packages/super-editor/src/editors/v1/components/toolbar/SdTooltip.vue
@@ -38,6 +38,7 @@ 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;
@@ -91,12 +92,16 @@ const updatePosition = () => {
   const contentHeight = contentRef.value.offsetHeight;
   const viewportWidth = window.innerWidth || document.documentElement.clientWidth || 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));
 
+  const topAbove = triggerRect.top - contentHeight - offset;
+  placement.value = topAbove < gutter ? 'bottom' : 'top';
+
   position.value = {
-    top: `${triggerRect.top - contentHeight - 10}px`,
+    top: placement.value === 'top' ? `${topAbove}px` : `${triggerRect.bottom + offset}px`,
     left: `${left}px`,
   };
 };
@@ -218,6 +223,7 @@ onBeforeUnmount(() => {
         ref="contentRef"
         :class="mergedContentClass"
         :style="contentStyle"
+        :data-placement="placement"
         @mouseenter="handleContentMouseEnter"
         @mouseleave="handleContentMouseLeave"
       >
@@ -255,11 +261,21 @@ onBeforeUnmount(() => {
   transform: translateX(-50%) rotate(45deg);
 }
 
+.sd-tooltip-content[data-placement='bottom'] .sd-tooltip-arrow {
+  bottom: auto;
+  top: -5px;
+}
+
 .fade-in-scale-up-transition-enter-active,
 .fade-in-scale-up-transition-leave-active {
   transform-origin: bottom center;
 }
 
+.sd-tooltip-content[data-placement='bottom'].fade-in-scale-up-transition-enter-active,
+.sd-tooltip-content[data-placement='bottom'].fade-in-scale-up-transition-leave-active {
+  transform-origin: top center;
+}
+
 .fade-in-scale-up-transition-enter-active {
   transition:
     opacity 0.2s cubic-bezier(0, 0, 0.2, 1),