diff --git a/e2e/overviewLane.spec.ts b/e2e/overviewLane.spec.ts
new file mode 100644
index 00000000..6c51df7c
--- /dev/null
+++ b/e2e/overviewLane.spec.ts
@@ -0,0 +1,30 @@
+import { expect, openFromTree, test } from "./fixtures";
+
+// Headless Chromium hides scrollbars by default; this test drags one.
+test.use({ launchOptions: { ignoreDefaultArgs: ["--hide-scrollbars"] } });
+
+test("the scrollbar thumb drags even where overview marks cover it (#752)", async ({ workbench: page }) => {
+  const editor = await openFromTree(page, "build.gradle.kts");
+  await editor.locator(".cm-content").click();
+  await page.keyboard.press("Meta+a");
+  await page.keyboard.insertText(Array.from({ length: 400 }, (_, i) => `val mark${i} = ${i}`).join("\n"));
+  // A match on every line covers the overview lane, as a new file's change mark does.
+  await page.keyboard.press("Meta+f");
+  await page.getByRole("textbox", { name: "Find" }).fill("mark");
+  await expect(editor.locator(".cm-openidea-overviewMark").first()).toBeVisible();
+  const scroller = editor.locator(".cm-scroller");
+  await scroller.evaluate((s) => (s.scrollTop = 0));
+  const box = (await scroller.boundingBox())!;
+  // Over a mark and inside the thumb, which is at the top of the track.
+  const x = box.x + box.width - 5;
+  const y = box.y + 12;
+  await page.mouse.move(x - 40, y);
+  await page.mouse.move(x, y);
+  await page.mouse.down();
+  await page.mouse.move(x, y + 150, { steps: 10 });
+  await page.mouse.up();
+  expect(await scroller.evaluate((s) => s.scrollTop)).toBeGreaterThan(0);
+  // Away from the thumb the marks take the pointer again.
+  await page.mouse.move(x, box.y + box.height - 20);
+  await expect(editor.locator(".cm-openidea-overview")).not.toHaveClass(/cm-openidea-overview-onThumb/);
+});
diff --git a/src/editor/core/cm/ideaParity.test.ts b/src/editor/core/cm/ideaParity.test.ts
index 38640f8f..bad82ca4 100644
--- a/src/editor/core/cm/ideaParity.test.ts
+++ b/src/editor/core/cm/ideaParity.test.ts
@@ -23,7 +23,7 @@ import {
   foldSelectionEffects,
 } from "./folding";
 import { columnModeExtension, extendBlock, toggleColumnMode } from "./columnMode";
-import { nearestMark, unfoldAround } from "./lanes";
+import { nearestMark, scrollbarThumb, unfoldAround } from "./lanes";
 import { lineRangeSelection } from "./gutterDrag";
 import { matchBraceTarget } from "./caretCommands";
 import { overwriteField, toggleOverwrite } from "./overwrite";
@@ -291,6 +291,16 @@ describe("error stripe", () => {
     expect(nearestMark(marks, 21)).toBeNull();
   });
 
+  it("finds the scrollbar thumb the marks must let through", () => {
+    // Nothing to scroll: no thumb.
+    expect(scrollbarThumb(0, 400, 400)).toBeNull();
+    // A quarter of the document visible: a 100px thumb, at the top, then at the bottom.
+    expect(scrollbarThumb(0, 1600, 400)).toEqual({ top: 0, bottom: 100 });
+    expect(scrollbarThumb(1200, 1600, 400)).toEqual({ top: 300, bottom: 400 });
+    // A long document keeps the 32px minimum thumb; halfway down it sits mid-track.
+    expect(scrollbarThumb(49800, 100000, 400)).toEqual({ top: 184, bottom: 216 });
+  });
+
   it("unfolds what hides the target line", () => {
     const s = EditorState.create({ doc: "f {\n  x\n}", extensions: [codeFolding()] }).update({
       effects: foldEffect.of({ from: 3, to: 8 }),
diff --git a/src/editor/core/cm/lanes.ts b/src/editor/core/cm/lanes.ts
index cb876831..9e6ac7c6 100644
--- a/src/editor/core/cm/lanes.ts
+++ b/src/editor/core/cm/lanes.ts
@@ -27,6 +27,27 @@ export function nearestMark<M extends { top: number; bottom: number }>(marks: re
   return best;
 }
 
+/** The smallest scrollbar thumb (`::-webkit-scrollbar-thumb` min-height in global.css). */
+const MIN_THUMB = 32;
+
+/**
+ * Where the vertical scrollbar thumb of a scroller is, in px from the top of its track, or null
+ * when nothing scrolls. The overview lane lies over the scrollbar, so its marks must not take
+ * the pointer where the thumb is (#752).
+ */
+export function scrollbarThumb(
+  scrollTop: number,
+  scrollHeight: number,
+  clientHeight: number,
+  minThumb = MIN_THUMB,
+): { top: number; bottom: number } | null {
+  const max = scrollHeight - clientHeight;
+  if (max <= 0 || clientHeight <= 0) return null;
+  const length = Math.min(clientHeight, Math.max(minThumb, (clientHeight * clientHeight) / scrollHeight));
+  const top = (Math.min(Math.max(scrollTop, 0), max) / max) * (clientHeight - length);
+  return { top, bottom: top + length };
+}
+
 /** Unfolds the folds hiding `pos` or the rest of its line (navigating to a mark shows it). */
 export function unfoldAround(state: EditorState, pos: number): StateEffect<unknown>[] {
   const lineEnd = state.doc.lineAt(pos).to;
@@ -41,12 +62,17 @@ class OverviewLane {
   dom: HTMLElement;
   private scheduled = false;
   private lastKey = "";
+  /** The last pointer position over the editor, to re-check the thumb when it scrolls. */
+  private pointer: { x: number; y: number } | null = null;
 
   constructor(private view: EditorView) {
     this.dom = document.createElement("div");
     this.dom.className = "cm-openidea-overview";
     this.dom.setAttribute("aria-hidden", "true");
     this.dom.addEventListener("mousedown", this.onMouseDown);
+    view.dom.addEventListener("mousemove", this.onPointerMove);
+    view.dom.addEventListener("mouseleave", this.onPointerLeave);
+    view.scrollDOM.addEventListener("scroll", this.onScroll, { passive: true });
     view.dom.appendChild(this.dom);
     this.schedule();
   }
@@ -132,6 +158,38 @@ class OverviewLane {
     });
   }
 
+  /**
+   * Over the scrollbar thumb the marks let the pointer through, so the thumb can be dragged
+   * even where a mark covers it (a new file is one mark the height of the lane, #752).
+   */
+  private updateThumbPassThrough() {
+    const p = this.pointer;
+    let over = false;
+    if (p) {
+      const lane = this.dom.getBoundingClientRect();
+      const s = this.view.scrollDOM;
+      const thumb = scrollbarThumb(s.scrollTop, s.scrollHeight, s.clientHeight);
+      const y = p.y - s.getBoundingClientRect().top;
+      over = !!thumb && p.x >= lane.left && p.x <= lane.right && y >= thumb.top && y <= thumb.bottom;
+    }
+    this.dom.classList.toggle("cm-openidea-overview-onThumb", over);
+  }
+
+  private onPointerMove = (e: MouseEvent) => {
+    this.pointer = { x: e.clientX, y: e.clientY };
+    // A thumb drag in progress keeps the marks out of the way until the button is released.
+    if (e.buttons === 0) this.updateThumbPassThrough();
+  };
+
+  private onPointerLeave = () => {
+    this.pointer = null;
+    this.updateThumbPassThrough();
+  };
+
+  private onScroll = () => {
+    if (this.pointer) this.updateThumbPassThrough();
+  };
+
   private onMouseDown = (e: MouseEvent) => {
     if (e.button !== 0) return;
     const marks = [...this.dom.querySelectorAll<HTMLElement>(".cm-openidea-overviewMark")].map((el) => {
@@ -153,6 +211,9 @@ class OverviewLane {
 
   destroy() {
     this.dom.removeEventListener("mousedown", this.onMouseDown);
+    this.view.dom.removeEventListener("mousemove", this.onPointerMove);
+    this.view.dom.removeEventListener("mouseleave", this.onPointerLeave);
+    this.view.scrollDOM.removeEventListener("scroll", this.onScroll);
     this.dom.remove();
   }
 }
diff --git a/src/editor/core/cm/theme.ts b/src/editor/core/cm/theme.ts
index 0a95f917..0390d1f1 100644
--- a/src/editor/core/cm/theme.ts
+++ b/src/editor/core/cm/theme.ts
@@ -283,6 +283,8 @@ export const openideaTheme = EditorView.theme({
     cursor: "pointer",
   },
   ".cm-openidea-overviewMark-thin": { left: "4px", width: "4px", minHeight: "2px" },
+  // The scrollbar thumb wins over the marks under it (cm/lanes.ts, #752).
+  ".cm-openidea-overview-onThumb .cm-openidea-overviewMark": { pointerEvents: "none" },
   ".cm-openidea-overviewCaret": {
     position: "absolute",
     left: "2px",