diff --git a/src/editor/core/cm/setup.ts b/src/editor/core/cm/setup.ts
index 3197fb1f1..87e6df7d8 100644
--- a/src/editor/core/cm/setup.ts
+++ b/src/editor/core/cm/setup.ts
@@ -319,15 +319,23 @@ export interface SetupOptions {
 }
 
 /**
- * Tooltips (hints, docs, completion) stay below the editor's top edge: one
- * above the first lines flips below them instead of hiding under the tabs.
+ * Tooltips (hints, docs, completion) stay inside the editor horizontally and
+ * below its top edge. WebKit positions them `absolute` within `.cm-editor`, so
+ * a window-wide right bound makes CodeMirror skip the shift left and the
+ * browser squeezes the box into the space left of the editor's edge.
  */
-const tooltipSpace = tooltips({
-  tooltipSpace: (view) => {
-    const top = view.scrollDOM.getBoundingClientRect().top;
-    return { top, left: 0, right: window.innerWidth, bottom: window.innerHeight };
-  },
-});
+export function tooltipBounds(view: { scrollDOM: Element; dom: Element }) {
+  const { top } = view.scrollDOM.getBoundingClientRect();
+  const { left, right } = view.dom.getBoundingClientRect();
+  return {
+    top,
+    left: Math.max(0, left),
+    right: Math.min(window.innerWidth, right),
+    bottom: window.innerHeight,
+  };
+}
+
+const tooltipSpace = tooltips({ tooltipSpace: tooltipBounds });
 
 export function baseExtensions(o: SetupOptions): Extension {
   return [
diff --git a/src/editor/core/cm/theme.ts b/src/editor/core/cm/theme.ts
index bc4ad7dbe..49641a972 100644
--- a/src/editor/core/cm/theme.ts
+++ b/src/editor/core/cm/theme.ts
@@ -248,6 +248,9 @@ export const openideaTheme = EditorView.theme({
 
   // Overlays
   ".cm-tooltip": {
+    // Natural width, so a measurement taken while squeezed is not fed back (#1188).
+    width: "max-content",
+    maxWidth: "100%",
     backgroundColor: "var(--bg-popup)",
     color: "var(--fg)",
     border: "1px solid var(--border-popup)",
diff --git a/src/editor/core/cm/tooltipBounds.test.ts b/src/editor/core/cm/tooltipBounds.test.ts
new file mode 100644
index 000000000..b24cf170b
--- /dev/null
+++ b/src/editor/core/cm/tooltipBounds.test.ts
@@ -0,0 +1,24 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { tooltipBounds } from "./setup";
+
+const el = (r: Partial<DOMRect>) => ({ getBoundingClientRect: () => r as DOMRect }) as Element;
+const original = window.innerWidth;
+
+beforeEach(() => {
+  Object.defineProperty(window, "innerWidth", { value: 1200, configurable: true });
+});
+afterEach(() => {
+  Object.defineProperty(window, "innerWidth", { value: original, configurable: true });
+});
+
+describe("tooltipBounds", () => {
+  it.each([
+    ["editor flush with the right edge", { left: 300, right: 1200 }, 300, 1200],
+    ["narrow split pane", { left: 0, right: 400 }, 0, 400],
+    ["editor in the middle", { left: 250, right: 750 }, 250, 750],
+    ["editor spilling outside the window", { left: -20, right: 1500 }, 0, 1200],
+  ])("%s", (_, rect, left, right) => {
+    const b = tooltipBounds({ scrollDOM: el({ top: 80 }), dom: el(rect) });
+    expect(b).toMatchObject({ top: 80, left, right });
+  });
+});