diff --git a/packages/app/src/git/diff-document/model.ts b/packages/app/src/git/diff-document/model.ts
index 106ca9e21..75cee369e 100644
--- a/packages/app/src/git/diff-document/model.ts
+++ b/packages/app/src/git/diff-document/model.ts
@@ -24,7 +24,7 @@ import type {
 } from "./types";
 
 export const FILE_HEADER_HEIGHT = 30;
-const BODY_BORDER_HEIGHT = 1;
+export const DIFF_BODY_BORDER_HEIGHT = 1;
 const CODE_HORIZONTAL_PADDING = 16;
 
 interface CellSource {
@@ -84,7 +84,7 @@ export function buildDiffDocumentModel(input: BuildDiffDocumentModelInput): Diff
         documentTop += reusedRow.height;
       }
       maximumHorizontalOverflow = Math.max(0, reusableFile.contentWidth - input.viewportWidth);
-      documentTop += BODY_BORDER_HEIGHT;
+      documentTop += DIFF_BODY_BORDER_HEIGHT;
     } else if (!isCollapsed) {
       if (file.status === "binary" || file.status === "too_large") {
         const height = input.typography.lineHeight + 24;
@@ -139,7 +139,7 @@ export function buildDiffDocumentModel(input: BuildDiffDocumentModelInput): Diff
           documentTop += height;
         }
       }
-      documentTop += BODY_BORDER_HEIGHT;
+      documentTop += DIFF_BODY_BORDER_HEIGHT;
     }
 
     files.push({
@@ -172,6 +172,12 @@ export function buildDiffDocumentModel(input: BuildDiffDocumentModelInput): Diff
   };
 }
 
+export function finalExpandedBodyBorderTop(model: DiffDocumentModel): number | null {
+  "worklet";
+  const file = model.files[model.files.length - 1];
+  return file && !file.isCollapsed ? file.bottom - DIFF_BODY_BORDER_HEIGHT : null;
+}
+
 export function retainReusableModels(
   previous: readonly DiffDocumentModel[] | undefined,
   next: DiffDocumentModel,
diff --git a/packages/app/src/git/diff-document/paint.native.ts b/packages/app/src/git/diff-document/paint.native.ts
index fb1116041..d80902925 100644
--- a/packages/app/src/git/diff-document/paint.native.ts
+++ b/packages/app/src/git/diff-document/paint.native.ts
@@ -5,7 +5,7 @@ import {
   type SkPaint,
   type SkPicture,
 } from "@shopify/react-native-skia";
-import { visibleRowRange } from "./model";
+import { DIFF_BODY_BORDER_HEIGHT, finalExpandedBodyBorderTop, visibleRowRange } from "./model";
 import { nativeTextRuns } from "./native-text-runs";
 import { horizontalOffsetForPath, type DiffHorizontalOffsets } from "./horizontal-offsets";
 import { codeLineNumberTone } from "./palette";
@@ -257,6 +257,18 @@ function paintNativeRange(input: PaintNativeRangeInput): void {
       }
     });
   }
+  const finalBorderTop = paintsFixedContent ? finalExpandedBodyBorderTop(input.model) : null;
+  if (finalBorderTop !== null) {
+    input.canvas.drawRect(
+      Skia.XYWHRect(
+        0,
+        finalBorderTop - input.scrollTop,
+        input.viewportWidth,
+        DIFF_BODY_BORDER_HEIGHT,
+      ),
+      input.paints.border,
+    );
+  }
 }
 
 function paintsNativeContentCell(
diff --git a/packages/app/src/git/diff-document/paint.web.test.ts b/packages/app/src/git/diff-document/paint.web.test.ts
index aac7837ec..33c81833a 100644
--- a/packages/app/src/git/diff-document/paint.web.test.ts
+++ b/packages/app/src/git/diff-document/paint.web.test.ts
@@ -84,6 +84,54 @@ describe("web diff text shaping", () => {
     expect(fills).toContainEqual({ color: "border", x: 20, y: 0, width: 1, height: 58 });
   });
 
+  it("paints the final expanded file body's bottom border", () => {
+    const fills: Array<{ color: string; x: number; y: number; width: number; height: number }> = [];
+    let fillStyle = "";
+    const context = {
+      setTransform() {},
+      clearRect() {},
+      fillRect(x: number, y: number, width: number, height: number) {
+        fills.push({ color: fillStyle, x, y, width, height });
+      },
+      save() {},
+      restore() {},
+      beginPath() {},
+      rect() {},
+      clip() {},
+      fillText() {},
+      get fillStyle() {
+        return fillStyle;
+      },
+      set fillStyle(value: string | CanvasGradient | CanvasPattern) {
+        fillStyle = String(value);
+      },
+      globalAlpha: 1,
+      font: "",
+      textBaseline: "alphabetic",
+    } as unknown as CanvasRenderingContext2D;
+    const borderedModel: DiffDocumentModel = {
+      ...model,
+      height: 19,
+      files: [{ ...model.files[0]!, bodyHeight: 19, bottom: 19 }],
+    };
+
+    paintWebViewport({
+      context,
+      model: borderedModel,
+      palette,
+      typography: { family: "monospace", size: 12, lineHeight: 18 },
+      measureText: { measure: () => 0 },
+      scrollTop: 0,
+      viewportWidth: 200,
+      viewportHeight: 100,
+      horizontalOffsets: new Map(),
+      selection: null,
+      devicePixelRatio: 1,
+    });
+
+    expect(fills).toContainEqual({ color: "border", x: 0, y: 18, width: 200, height: 1 });
+  });
+
   it("clips a horizontally scrolled unified selection to the code viewport", () => {
     const selectionModel = createSelectionModel("unified");
     const paints = paintSelection(selectionModel, selectionForCell(0));
diff --git a/packages/app/src/git/diff-document/paint.web.ts b/packages/app/src/git/diff-document/paint.web.ts
index 09610ddf3..776fd8aee 100644
--- a/packages/app/src/git/diff-document/paint.web.ts
+++ b/packages/app/src/git/diff-document/paint.web.ts
@@ -1,5 +1,10 @@
 import { selectionRectangles } from "./hit-testing";
-import { fragmentWidthForRange, visibleRowRange } from "./model";
+import {
+  DIFF_BODY_BORDER_HEIGHT,
+  finalExpandedBodyBorderTop,
+  fragmentWidthForRange,
+  visibleRowRange,
+} from "./model";
 import { codeLineNumberTone, codeTextColor } from "./palette";
 import { reviewBackgroundPaint, reviewDividerHeight, reviewGapTop } from "./review-paint";
 import type {
@@ -64,6 +69,17 @@ export function paintWebViewport(input: PaintWebViewportInput): void {
     });
   }
 
+  const finalBorderTop = finalExpandedBodyBorderTop(input.model);
+  if (finalBorderTop !== null) {
+    context.fillStyle = input.palette.border;
+    context.fillRect(
+      0,
+      finalBorderTop - input.scrollTop,
+      input.viewportWidth,
+      DIFF_BODY_BORDER_HEIGHT,
+    );
+  }
+
   if (input.selection) paintSelection(input, input.selection);
   context.restore();
 }
diff --git a/packages/app/src/git/diff-document/surface.web.tsx b/packages/app/src/git/diff-document/surface.web.tsx
index 60a160fab..ae1ad9e51 100644
--- a/packages/app/src/git/diff-document/surface.web.tsx
+++ b/packages/app/src/git/diff-document/surface.web.tsx
@@ -209,15 +209,7 @@ export function DiffSurface(props: DiffSurfaceProps) {
   }, [loadedTypography, measurement, props.palette, viewport.height, viewport.width]);
   const schedulePaint = useCallback(
     (force = true) => {
-      if (force) {
-        forcePaintRef.current = true;
-        // Fast Refresh preserves refs. A request owned by the previous module can leave a stale
-        // id behind, which would otherwise prevent every subsequent canvas repaint.
-        if (frameRef.current !== null) {
-          cancelAnimationFrame(frameRef.current);
-          frameRef.current = null;
-        }
-      }
+      if (force) forcePaintRef.current = true;
       if (frameRef.current === null) frameRef.current = requestAnimationFrame(paint);
     },
     [paint],
@@ -267,6 +259,8 @@ export function DiffSurface(props: DiffSurfaceProps) {
   useEffect(
     () => () => {
       if (frameRef.current !== null) cancelAnimationFrame(frameRef.current);
+      // Fast Refresh preserves refs while rerunning effects. Release ownership of the canceled
+      // request so the refreshed renderer can schedule its first paint.
       frameRef.current = null;
     },
     [],