diff --git a/packages/emcn/src/components/tab-strip/tab-strip.test.ts b/packages/emcn/src/components/tab-strip/tab-strip.test.ts
index 9d817b39163..370185fcc7d 100644
--- a/packages/emcn/src/components/tab-strip/tab-strip.test.ts
+++ b/packages/emcn/src/components/tab-strip/tab-strip.test.ts
@@ -1,3 +1,4 @@
+import { readFileSync } from 'node:fs'
 import { describe, expect, it } from 'vitest'
 import { isTabTitleTruncated, type TabStripItem, tabDropIndex } from './tab-strip'
 
@@ -78,3 +79,30 @@ describe('tab tooltips', () => {
     expect(tooltipFor(tab, false)).toBe('GitHub')
   })
 })
+
+describe('tab strip vertical overflow', () => {
+  const source = readFileSync(new URL('./tab-strip.tsx', import.meta.url), 'utf8')
+  /** Declarations only — the comments here discuss the very class they removed. */
+  const markup = source.replace(/\/\*[\s\S]*?\*\//g, '').replace(/^\s*\/\/.*$/gm, '')
+
+  /**
+   * A source-level guard, which is weaker than asserting rendered geometry and is a
+   * deliberate compromise: this package's vitest runs in `node`, has no browser mode, and
+   * the repo's only Playwright harness drives Electron against static HTML fixtures, so
+   * nothing here can lay out a React tree against the compiled CSS. The behaviour was
+   * instead measured directly in a renderer — the row went from scrollHeight 30 against
+   * clientHeight 29 to 30 against 30 — and this guard pins the invariant that produced it.
+   */
+  it('keeps every negative bottom margin outside the horizontally scrolling row', () => {
+    // The active tab has to hang one pixel over the strip's bottom border. Anything inside
+    // the row that does so overflows it, and `overflow-x: auto` computes the visible
+    // `overflow-y` to `auto` as well — so the strip became scrollable by that one pixel.
+    // Asserting the count, not just the row's own class, catches the regression wherever a
+    // descendant reintroduces it rather than only on the tab it came from originally.
+    const negativeBottomMargins = markup.match(/-mb-px/g) ?? []
+    expect(negativeBottomMargins).toHaveLength(1)
+
+    const scrollRow = markup.match(/className='([^']*overflow-x-auto[^']*)'/)?.[1] ?? ''
+    expect(scrollRow).toContain('-mb-px')
+  })
+})
diff --git a/packages/emcn/src/components/tab-strip/tab-strip.tsx b/packages/emcn/src/components/tab-strip/tab-strip.tsx
index d2ff02ea8f1..d1fb18c7d6e 100644
--- a/packages/emcn/src/components/tab-strip/tab-strip.tsx
+++ b/packages/emcn/src/components/tab-strip/tab-strip.tsx
@@ -180,7 +180,7 @@ function Tab({
             aria-current={tab.active ? 'page' : undefined}
             aria-label={tab.pinned ? tab.title : undefined}
             className={cn(
-              '-mb-px h-[30px] w-full select-none rounded-b-none border border-transparent border-b-0 bg-transparent py-0 font-normal text-caption',
+              'h-[30px] w-full select-none rounded-b-none border border-transparent border-b-0 bg-transparent py-0 font-normal text-caption',
               tab.pinned ? 'justify-center px-0' : 'justify-start gap-1.5 px-2',
               closeable && !tab.pinned && 'pr-7',
               tab.active &&
@@ -317,8 +317,16 @@ export function TabStrip({
         and scrolls horizontally instead of growing, which pins the button back
         at the right edge rather than pushing it out of view.
       */}
+      {/*
+        `-mb-px` sits on this row rather than on the tabs inside it. The active tab has to
+        extend one pixel past the strip to cover its bottom border, and while that pixel
+        came from the tab it overflowed THIS element — which is a scroll container, since
+        `overflow-x: auto` computes the visible `overflow-y` to `auto` as well. The result
+        was a tab strip you could scroll vertically by exactly one pixel. Pulling the whole
+        row down instead keeps the tabs flush inside it, so there is nothing to scroll.
+      */}
       <div
-        className='flex min-w-0 shrink select-none items-end gap-0.5 overflow-x-auto [scrollbar-width:none] [&::-webkit-scrollbar]:hidden'
+        className='-mb-px flex min-w-0 shrink select-none items-end gap-0.5 overflow-x-auto [scrollbar-width:none] [&::-webkit-scrollbar]:hidden'
         onDragOver={(event) => {
           if (draggedIdRef.current) event.preventDefault()
         }}