diff --git a/apps/desktop/src/components/grid/DataGridConditionEditor.vue b/apps/desktop/src/components/grid/DataGridConditionEditor.vue
index 080e67ae81..dacdb5967d 100644
--- a/apps/desktop/src/components/grid/DataGridConditionEditor.vue
+++ b/apps/desktop/src/components/grid/DataGridConditionEditor.vue
@@ -84,8 +84,18 @@ const highlightTokens = computed(() => tokenizeDataGridCondition(modelValue.valu
 const collapsedHighlightScrollLeft = ref(0);
 const expandedHighlightScrollLeft = ref(0);
 const expandedHighlightScrollTop = ref(0);
+// The highlight layer is a plain div and never gives up content width to a
+// scrollbar, while the transparent-text textarea above it does. Both wrap with
+// `white-space: pre-wrap` + `overflow-wrap: anywhere`, so an uncompensated
+// scrollbar makes the two layers break at different characters and the visible
+// text drifts away from the caret. Compensate with the measured width instead
+// of assuming one.
+const expandedHighlightScrollbarWidth = ref(0);
 const collapsedHighlightStyle = computed<CSSProperties>(() => ({ transform: `translateX(${-collapsedHighlightScrollLeft.value}px)` }));
-const expandedHighlightStyle = computed<CSSProperties>(() => ({ transform: `translate(${-expandedHighlightScrollLeft.value}px, ${-expandedHighlightScrollTop.value}px)` }));
+const expandedHighlightStyle = computed<CSSProperties>(() => ({
+  transform: `translate(${-expandedHighlightScrollLeft.value}px, ${-expandedHighlightScrollTop.value}px)`,
+  "--data-grid-condition-highlight-scrollbar": `${expandedHighlightScrollbarWidth.value}px`,
+}));
 
 function highlightTokenClass(type: DataGridConditionTokenType): string | undefined {
   if (type === "plain") return undefined;
@@ -177,6 +187,21 @@ function fitExpandedHeightToOverlay() {
   }
 }
 
+function syncExpandedHighlightScrollbar() {
+  const overlay = overlayRef.value;
+  if (!overlay) return;
+  const scrollbar = Math.max(0, overlay.offsetWidth - overlay.clientWidth);
+  if (scrollbar !== expandedHighlightScrollbarWidth.value) expandedHighlightScrollbarWidth.value = scrollbar;
+}
+
+function syncExpandedLayout() {
+  syncExpandedHighlightScrollbar();
+  // Re-fit once the compensation has been applied: the highlight layer now
+  // wraps exactly like the textarea, so the pane can size itself to the real
+  // content height instead of leaving a scrollbar that only the textarea sees.
+  void nextTick(fitExpandedHeightToOverlay);
+}
+
 function measureExpandedRect(input: HTMLTextAreaElement) {
   const inputRect = input.getBoundingClientRect();
   const control = controlRef.value;
@@ -238,7 +263,7 @@ function resizeEditor(forceExpand = false) {
       const nextRect = measureExpandedRect(input);
       expandedRect.value = nextRect;
       expandedHeight.value = measureExpandedHeight(input, nextRect);
-      void nextTick(fitExpandedHeightToOverlay);
+      void nextTick(syncExpandedLayout);
     }
     expanded.value = nextExpanded;
     updateSuggestionPosition();
@@ -923,7 +948,7 @@ defineExpose({ focus, dismiss: editor.dismiss, rememberHistory: editor.rememberH
   min-width: 0;
   height: auto;
   margin-right: calc(-1 * var(--data-grid-expanded-scrollbar-offset));
-  padding: 0 calc(var(--data-grid-condition-suffix-width) + 0.5rem) 0.0625rem calc(var(--data-grid-condition-prefix-indent) + 0.125rem);
+  padding: 0 calc(var(--data-grid-condition-suffix-width) + 0.5rem + var(--data-grid-condition-highlight-scrollbar, 0px)) 0.0625rem calc(var(--data-grid-condition-prefix-indent) + 0.125rem);
   white-space: pre-wrap;
   overflow-wrap: anywhere;
 }
diff --git a/apps/desktop/src/components/grid/__tests__/DataGridConditionEditor.spec.ts b/apps/desktop/src/components/grid/__tests__/DataGridConditionEditor.spec.ts
index 8e35053e31..516650bfc5 100644
--- a/apps/desktop/src/components/grid/__tests__/DataGridConditionEditor.spec.ts
+++ b/apps/desktop/src/components/grid/__tests__/DataGridConditionEditor.spec.ts
@@ -379,6 +379,49 @@ describe("DataGridConditionEditor quote completion", () => {
     expect(expandedHighlight?.style.transform).toBe("translate(0px, 0px)");
     vi.unstubAllGlobals();
   });
+
+  it("compensates the expanded highlight layer for the textarea scrollbar", async () => {
+    vi.spyOn(HTMLElement.prototype, "getBoundingClientRect").mockImplementation(function (this: HTMLElement) {
+      const textWidth = (this.textContent?.length ?? 0) * 8;
+      const width = this.classList.contains("data-grid-topbar-condition-pane--expanded") ? 160 : textWidth;
+      return { x: 0, y: 0, left: 0, top: 0, right: width, bottom: 24, width, height: 24, toJSON: () => ({}) } as DOMRect;
+    });
+    vi.spyOn(HTMLCanvasElement.prototype, "getContext").mockReturnValue(null);
+    vi.stubGlobal("requestAnimationFrame", (callback: FrameRequestCallback) => {
+      callback(0);
+      return 1;
+    });
+    const { input } = mountEditor("where", "test_item_id=12 and test_item_name=''");
+    mockTextareaMetrics(input, { clientWidth: 80, scrollWidth: 320 });
+    input.focus();
+    input.setSelectionRange(input.value.length, input.value.length);
+    input.dispatchEvent(new Event("focus", { bubbles: true }));
+
+    await nextTick();
+    await nextTick();
+
+    const overlay = document.body.querySelector(".data-grid-topbar-condition-input--expanded") as HTMLTextAreaElement | null;
+    const expandedHighlight = document.body.querySelector(".data-grid-condition-highlight--expanded") as HTMLElement | null;
+    expect(overlay).toBeTruthy();
+    expect(expandedHighlight).toBeTruthy();
+
+    // A vertical scrollbar takes content width away from the textarea but not
+    // from the plain-div highlight layer. Both wrap with `pre-wrap` +
+    // `overflow-wrap: anywhere`, so unless the layer gives up the same width the
+    // two break at different characters and the caret drifts off the visible text.
+    Object.defineProperties(overlay as HTMLTextAreaElement, {
+      offsetWidth: { configurable: true, value: 178 },
+      clientWidth: { configurable: true, value: 168 },
+    });
+    overlay?.dispatchEvent(new Event("input", { bubbles: true }));
+
+    await nextTick();
+    await nextTick();
+    await nextTick();
+
+    expect(expandedHighlight?.style.getPropertyValue("--data-grid-condition-highlight-scrollbar")).toBe("10px");
+    vi.unstubAllGlobals();
+  });
 });
 
 describe("DataGridConditionEditor Chinese column matching", () => {