feat(diff-panel): show total line additions and deletions

apps/web/src/components/DiffPanel.tsx

@@ -30,6 +30,7 @@ import { useTheme } from "../hooks/useTheme";
 import {
   buildFileDiffRenderKey,
   getDiffCollapseIconClassName,
+  getDiffLineStat,
   getRenderablePatch,
   resolveDiffThemeName,
   resolveFileDiffPath,
@@ -41,6 +42,7 @@ import { resolveThreadRouteRef } from "../threadRoutes";
 import { useClientSettings } from "../hooks/useSettings";
 import { formatShortTimestamp } from "../timestampFormat";
 import { DiffPanelLoadingState, DiffPanelShell, type DiffPanelMode } from "./DiffPanelShell";
+import { DiffStatLabel } from "./chat/DiffStatLabel";
 import { AnnotatableCodeView, type AnnotatableCodeViewHandle } from "./diffs/AnnotatableCodeView";
 import { Button } from "./ui/button";
 import { ToggleGroup, Toggle } from "./ui/toggle-group";
@@ -452,6 +454,7 @@ export default function DiffPanel({
   );
   const diffFileKeys = useMemo(() => codeViewFiles.map((file) => file.fileKey), [codeViewFiles]);
   const allDiffFilesCollapsed = areAllDiffFilesCollapsed(diffFileKeys, collapsedDiffFileKeys);
+  const diffLineStat = useMemo(() => getDiffLineStat(renderableFiles), [renderableFiles]);
 
   useEffect(() => {
     if (!selectedFilePath) return;
@@ -713,6 +716,14 @@ export default function DiffPanel({
         )}
       </div>
       <div className="flex shrink-0 items-center gap-1 [-webkit-app-region:no-drag]">
+        {codeViewFiles.length > 0 && (
+          <DiffStatLabel
+            additions={diffLineStat.additions}
+            deletions={diffLineStat.deletions}
+            className="mr-1 text-[11px]"
+            layout="inline"
+          />
+        )}
         {codeViewFiles.length > 0 && (
           <Tooltip>
             <TooltipTrigger

apps/web/src/lib/diffRendering.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from "vite-plus/test";
-import { buildPatchCacheKey, getRenderablePatch } from "./diffRendering";
+import { buildPatchCacheKey, getDiffLineStat, getRenderablePatch } from "./diffRendering";
 
 describe("buildPatchCacheKey", () => {
   it("returns a stable cache key for identical content", () => {
@@ -82,3 +82,33 @@ describe("getRenderablePatch", () => {
     expect(parsed.files[0]?.hunks[0]?.unifiedLineStart).toBe(47);
   });
 });
+
+describe("getDiffLineStat", () => {
+  it("totals additions and deletions across every file and hunk", () => {
+    const patch = [
+      "diff --git a/example.ts b/example.ts",
+      "--- a/example.ts",
+      "+++ b/example.ts",
+      "@@ -1,2 +1,3 @@",
+      "-before",
+      "+after",
+      "+added",
+      " context",
+      "@@ -10,2 +11,1 @@",
+      "-removed",
+      " context",
+      "diff --git a/README.md b/README.md",
+      "--- a/README.md",
+      "+++ b/README.md",
+      "@@ -1 +1,2 @@",
+      " title",
+      "+description",
+    ].join("\n");
+
+    const parsed = getRenderablePatch(patch);
+    expect(parsed?.kind).toBe("files");
+    if (parsed?.kind !== "files") return;
+
+    expect(getDiffLineStat(parsed.files)).toEqual({ additions: 3, deletions: 2 });
+  });
+});

apps/web/src/lib/diffRendering.ts

@@ -52,6 +52,25 @@ export type RenderablePatch =
       reason: string;
     };
 
+export interface DiffLineStat {
+  additions: number;
+  deletions: number;
+}
+
+export function getDiffLineStat(files: ReadonlyArray<FileDiffMetadata>): DiffLineStat {
+  return files.reduce<DiffLineStat>(
+    (total, file) => {
+      for (const hunk of file.hunks) {
+        total.additions += hunk.additionLines;
+        total.deletions += hunk.deletionLines;
+      }
+
+      return total;
+    },
+    { additions: 0, deletions: 0 },
+  );
+}
+
 interface RenderablePatchOptions {
   /**
    * Pierre's partial-patch parser keeps hunk render starts in source-file