fix: reject oversized checkout diffs (#2488)

* fix: reject oversized checkout diffs

* fix(diff): keep large previews from disconnecting clients

The physical socket limit is an OOM backstop, not a frame-size contract. Bound structured diff construction incrementally and report oversized previews without closing the client's socket.

* fix(app): preserve oversized diff state

* fix(diff): stay within relay frame limit

---------

Co-authored-by: Mohamed Boudra <boudra.moha@gmail.com>

packages/app/src/git/diff-pane.tsx

@@ -119,6 +119,7 @@ import {
   type InlineReviewActions,
 } from "@/review";
 import { usePublishWorkingDiffAttachment, useWorkingDiff } from "@/git/use-working-diff";
+import { DiffTooLargeState } from "@/git/diff-too-large-state";
 
 export type { GitActionId, GitAction, GitActions } from "@/git/policy";
 
@@ -1755,6 +1756,7 @@ interface DiffBodyContentProps {
   notGit: boolean;
   isDiffLoading: boolean;
   diffErrorMessage: string | null;
+  diffTooLarge: boolean;
   hasChanges: boolean;
   emptyMessage: string;
   children: ReactElement;
@@ -1768,6 +1770,7 @@ function DiffBodyContent({
   notGit,
   isDiffLoading,
   diffErrorMessage,
+  diffTooLarge,
   hasChanges,
   emptyMessage,
   children,
@@ -1803,6 +1806,9 @@ function DiffBodyContent({
       </View>
     );
   }
+  if (diffTooLarge) {
+    return <DiffTooLargeState />;
+  }
   if (diffErrorMessage) {
     return (
       <View style={styles.errorContainer}>
@@ -2693,6 +2699,7 @@ export function GitDiffPane({
     selectBase: handleSelectBase,
     files,
     diffPayloadError,
+    diffTooLarge,
     isDiffLoading,
     reviewActions,
     reviewAttachment,
@@ -2855,6 +2862,7 @@ export function GitDiffPane({
       notGit={notGit}
       isDiffLoading={isDiffLoading}
       diffErrorMessage={diffErrorMessage}
+      diffTooLarge={diffTooLarge}
       hasChanges={hasChanges}
       emptyMessage={emptyMessage}
       checkingRepositoryLabel={t("workspace.git.diff.checkingRepository")}

packages/app/src/git/diff-too-large-state.tsx

@@ -0,0 +1,49 @@
+import { useTranslation } from "react-i18next";
+import { Text, View } from "react-native";
+import { FileWarning } from "lucide-react-native";
+import { StyleSheet, withUnistyles } from "react-native-unistyles";
+import { ICON_SIZE, type Theme } from "@/styles/theme";
+
+const ThemedFileWarning = withUnistyles(FileWarning);
+const foregroundMutedIconColorMapping = (theme: Theme) => ({ color: theme.colors.foregroundMuted });
+
+export function DiffTooLargeState() {
+  const { t } = useTranslation();
+
+  return (
+    <View style={styles.container} testID="diff-too-large">
+      <ThemedFileWarning size={ICON_SIZE.lg} uniProps={foregroundMutedIconColorMapping} />
+      <View style={styles.copy}>
+        <Text style={styles.title}>{t("workspace.git.diff.previewTooLargeTitle")}</Text>
+        <Text style={styles.description}>{t("workspace.git.diff.previewTooLargeDescription")}</Text>
+      </View>
+    </View>
+  );
+}
+
+const styles = StyleSheet.create((theme) => ({
+  container: {
+    flex: 1,
+    alignItems: "center",
+    justifyContent: "center",
+    gap: theme.spacing[3],
+    paddingHorizontal: theme.spacing[6],
+    paddingTop: theme.spacing[16],
+  },
+  copy: {
+    alignItems: "center",
+    gap: theme.spacing[1],
+    maxWidth: 360,
+  },
+  title: {
+    color: theme.colors.foreground,
+    fontSize: theme.fontSize.base,
+    fontWeight: theme.fontWeight.normal,
+    textAlign: "center",
+  },
+  description: {
+    color: theme.colors.foregroundMuted,
+    fontSize: theme.fontSize.xs,
+    textAlign: "center",
+  },
+}));

packages/app/src/git/use-diff-query.ts

@@ -92,6 +92,7 @@ export function useCheckoutDiffQuery({
   return {
     files: payload?.files ?? [],
     payloadError,
+    diffTooLarge: payload?.diffTooLarge === true,
     isLoading: payload === null && enabled && isConnected,
     isFetching: false,
     isError: Boolean(payloadError),

packages/app/src/git/use-working-diff.ts

@@ -79,6 +79,7 @@ export function useWorkingDiff({
   const {
     files,
     payloadError: diffPayloadError,
+    diffTooLarge,
     isLoading: isDiffLoading,
   } = useCheckoutDiffQuery({
     serverId,
@@ -123,6 +124,7 @@ export function useWorkingDiff({
     selectBase,
     files,
     diffPayloadError,
+    diffTooLarge,
     isDiffLoading,
     reviewActions,
     reviewAttachment,