diff --git a/packages/app/src/data/providers-snapshot.test.ts b/packages/app/src/data/providers-snapshot.test.ts
index c1a8ca1ec2..56cf80653a 100644
--- a/packages/app/src/data/providers-snapshot.test.ts
+++ b/packages/app/src/data/providers-snapshot.test.ts
@@ -3,6 +3,7 @@ import { QueryClient, CancelledError } from "@tanstack/react-query";
 import type { ProviderSnapshotEntry } from "@getpaseo/protocol/agent-types";
 import type { GetProvidersSnapshotResponseMessage } from "@getpaseo/protocol/messages";
 import { compactProviderSnapshot } from "@getpaseo/protocol/provider-snapshot-codec";
+import { applyProvidersSnapshotUpdate } from "./push-router";
 import { createProviderSnapshotCache } from "./provider-snapshot-cache";
 import {
   resolveProviderIconName,
@@ -296,3 +297,41 @@ it("keeps a replacement query when the cancelled native fetch finishes late", as
     replaceProviderSnapshotIcons(serverId, []);
   }
 });
+
+describe("provider snapshot publication identity", () => {
+  it("keeps the hash cache's canonical objects across a catalog change and later announcements", async () => {
+    const cache = createProviderSnapshotCache(createStorage());
+    const queryClient = new QueryClient();
+    const serverId = "canonical-provider-snapshot";
+    const client = {
+      async getProvidersSnapshot() {
+        throw new Error("Unexpected content fetch");
+      },
+    };
+    const changed = {
+      ...snapshot,
+      snapshotHash: "next-hash",
+      compactSnapshot: compactProviderSnapshot([{ ...entries[0]!, label: "Updated provider" }]),
+    };
+    try {
+      for (const body of [snapshot, changed, changed]) {
+        await applyProvidersSnapshotUpdate({
+          serverId,
+          queryClient,
+          cache,
+          client,
+          message: { type: "providers_snapshot_update", payload: body },
+        });
+        const canonical = await cache.materialize(serverId, body);
+        const published = queryClient.getQueryData<GetProvidersSnapshotResponseMessage["payload"]>(
+          providersSnapshotQueryKey(serverId, body.cwd),
+        )!;
+        expect(published.entries).toBe(canonical.entries);
+        expect(published.compactSnapshot).toBe(canonical.compactSnapshot);
+        expect(published.entries[0]!.models).toBe(canonical.entries[0]!.models);
+      }
+    } finally {
+      queryClient.clear();
+    }
+  });
+});
diff --git a/packages/app/src/data/providers-snapshot.ts b/packages/app/src/data/providers-snapshot.ts
index 0e9cc26495..fadaf5ee77 100644
--- a/packages/app/src/data/providers-snapshot.ts
+++ b/packages/app/src/data/providers-snapshot.ts
@@ -78,6 +78,7 @@ export async function fetchProvidersSnapshot(input: {
       const body = await queryClient.fetchQuery({
         queryKey: ["providerSnapshotContent", input.serverId, hash],
         gcTime: 0,
+        structuralSharing: false,
         staleTime: 0,
         retry: false,
         queryFn: async () => {
@@ -134,6 +135,7 @@ export async function refreshAndApplyProvidersSnapshot(input: {
   await input.queryClient.fetchQuery({
     queryKey,
     staleTime: 0,
+    structuralSharing: false,
     queryFn: ({ signal }) => fetchProvidersSnapshot({ ...input, signal }),
   });
   void input.queryClient.invalidateQueries({
diff --git a/packages/app/src/data/push-router.test.ts b/packages/app/src/data/push-router.test.ts
index 7bc9ea2b51..ae99c5dfbc 100644
--- a/packages/app/src/data/push-router.test.ts
+++ b/packages/app/src/data/push-router.test.ts
@@ -146,6 +146,77 @@ function providerUpdate(generatedAt: string): ProvidersSnapshotUpdateMessage {
 }
 
 describe("server data push router", () => {
+  it("retains equal diff files without reconstructing changed file bodies", () => {
+    const queryClient = new QueryClient();
+    const fake = createFakeClient();
+    const serverId = "diff-sharing";
+    const cwd = "/repo";
+    const queryKey = checkoutDiffQueryKey(serverId, cwd, "uncommitted", undefined, false);
+    const subscriptionId = "diff-sharing";
+    queryClient.getQueryCache().build(queryClient, {
+      queryKey,
+      queryFn: skipToken,
+      meta: checkoutDiffPushRoute({
+        enabled: false,
+        serverId,
+        cwd,
+        subscriptionId,
+        compare: { mode: "uncommitted" },
+      }),
+    });
+    const unmount = mountServerDataPushRouter({ queryClient, client: fake.client, serverId });
+    type Payload = SubscribeCheckoutDiffResponseMessage["payload"];
+    const files: Payload["files"] = ["a.ts", "b.ts"].map((path) => ({
+      path,
+      isNew: true,
+      isDeleted: false,
+      additions: 2,
+      deletions: 0,
+      hunks: [
+        {
+          oldStart: 0,
+          oldCount: 0,
+          newStart: 1,
+          newCount: 2,
+          lines: [
+            {
+              type: "add",
+              content: "const answer = 42",
+              tokens: [
+                { text: "const", style: "keyword" },
+                { text: " answer = 42", style: null },
+              ],
+            },
+            { type: "add", content: "answer", tokens: [{ text: "answer", style: null }] },
+          ],
+        },
+      ],
+    }));
+    const publish = (incomingFiles: Payload["files"], requestId: string) => {
+      fake.emit({
+        type: "subscribe_checkout_diff_response",
+        payload: { subscriptionId, cwd, files: incomingFiles, requestId, error: null },
+      });
+      return queryClient.getQueryData<Payload>(queryKey)!;
+    };
+    try {
+      const first = publish(files, "first");
+      const same = publish(structuredClone(files), "reopen");
+      expect(same.files).toBe(first.files);
+      expect(same.requestId).toBe("reopen");
+      const changed = structuredClone(files);
+      changed[0]!.hunks[0]!.lines[0]!.tokens![0]!.style = "variable";
+      const next = publish(changed, "edit");
+      expect(next.files[1]).toBe(first.files[1]);
+      expect(next.files[0]).toBe(changed[0]);
+      expect(next.files[0]!.hunks[0]!.lines[0]!.tokens![0]!.style).toBe("variable");
+      expect(publish([], "deleted").files).toEqual([]);
+    } finally {
+      unmount();
+      queryClient.clear();
+    }
+  });
+
   it("routes provider snapshot and daemon config payloads until detached", async () => {
     const queryClient = new QueryClient();
     const fake = createFakeClient();
diff --git a/packages/app/src/data/push-router.ts b/packages/app/src/data/push-router.ts
index 1cdf555874..72c8ef20b2 100644
--- a/packages/app/src/data/push-router.ts
+++ b/packages/app/src/data/push-router.ts
@@ -5,6 +5,7 @@ import type {
   SessionOutboundMessage,
 } from "@getpaseo/protocol/messages";
 import { agentCommandsQueryRoot } from "@/hooks/agent-commands-query";
+import { shareCheckoutDiff } from "@/git/diff-sharing";
 import { orderCheckoutDiffFiles } from "@/git/diff-order";
 import { daemonConfigQueryKey } from "@/data/daemon-config";
 import { daemonPairingOfferQueryKey } from "@/data/daemon-pairing";
@@ -203,6 +204,7 @@ export async function applyProvidersSnapshotUpdate(input: {
   await input.queryClient.fetchQuery({
     queryKey,
     staleTime: 0,
+    structuralSharing: false,
     retry: false,
     queryFn: ({ signal }) => {
       const incoming = announcement;
@@ -510,6 +512,7 @@ function setCheckoutDiffPayload(input: {
     ) {
       continue;
     }
+    query.setOptions({ ...query.options, structuralSharing: shareCheckoutDiff });
     input.queryClient.setQueryData<CheckoutDiffCachePayload>(query.queryKey, input.payload);
   }
 }
diff --git a/packages/app/src/data/query.ts b/packages/app/src/data/query.ts
index e1e28ee3b7..2a645f8666 100644
--- a/packages/app/src/data/query.ts
+++ b/packages/app/src/data/query.ts
@@ -31,8 +31,10 @@ type FetchQueryInput<TQueryFnData, TError, TData, TQueryKey extends QueryKey> =
 > & {
   dataShape: "list" | "value";
   queryFn: QueryFnOption<TQueryFnData, TError, TData, TQueryKey>;
-  staleTimeMs: number;
-};
+} & (
+    | { staleTimeMs: number; immutableWhen?: never }
+    | { staleTimeMs?: never; immutableWhen: (data: TQueryFnData) => boolean }
+  );
 
 export function useReplicaQuery<
   TQueryFnData,
@@ -88,7 +90,7 @@ function replicaQueryOptions<
   };
 }
 
-function fetchQueryOptions<
+export function fetchQueryOptions<
   TQueryFnData,
   TError = Error,
   TData = TQueryFnData,
@@ -96,11 +98,11 @@ function fetchQueryOptions<
 >(
   input: FetchQueryInput<TQueryFnData, TError, TData, TQueryKey>,
 ): UseQueryOptions<TQueryFnData, TError, TData, TQueryKey> {
-  if (!Number.isFinite(input.staleTimeMs)) {
+  if (!input.immutableWhen && !Number.isFinite(input.staleTimeMs)) {
     throw new Error("Fetch queries must declare a finite staleTimeMs.");
   }
 
-  const { dataShape, meta, staleTimeMs, ...options } = input;
+  const { dataShape, meta, staleTimeMs, immutableWhen, ...options } = input;
   return {
     ...options,
     ...(dataShape === "list" ? { placeholderData: keepPreviousData } : {}),
@@ -111,7 +113,10 @@ function fetchQueryOptions<
         dataShape,
       },
     },
-    refetchOnMount: "always",
-    staleTime: staleTimeMs,
+    refetchOnMount: immutableWhen ? true : "always",
+    staleTime: immutableWhen
+      ? (query) =>
+          query.state.data !== undefined && immutableWhen(query.state.data) ? Infinity : 0
+      : staleTimeMs,
   };
 }
diff --git a/packages/app/src/git/commit-file-diff-query.test.ts b/packages/app/src/git/commit-file-diff-query.test.ts
new file mode 100644
index 0000000000..173592639d
--- /dev/null
+++ b/packages/app/src/git/commit-file-diff-query.test.ts
@@ -0,0 +1,76 @@
+import { QueryClient, QueryObserver } from "@tanstack/react-query";
+import { describe, expect, it } from "vitest";
+import { fetchQueryOptions } from "@/data/query";
+import { commitFileDiffQueryOptions } from "./commit-file-diff-query";
+
+const file = { path: "a.ts", isNew: true, isDeleted: false, additions: 0, deletions: 0, hunks: [] };
+
+describe("commit file diff fetching", () => {
+  it("reuses a cached commit body on remount and fetches on explicit refresh", async () => {
+    const queryClient = new QueryClient();
+    let calls = 0;
+    const options = fetchQueryOptions(
+      commitFileDiffQueryOptions({
+        serverId: "host",
+        cwd: "/repo",
+        sha: "abc",
+        path: "a.ts",
+        enabled: true,
+        client: {
+          async getCommitFileDiff() {
+            calls++;
+            return { file };
+          },
+        },
+      }),
+    );
+    queryClient.setQueryData(
+      options.queryKey,
+      { file },
+      { updatedAt: Date.now() - 24 * 60 * 60 * 1000 },
+    );
+    const observer = new QueryObserver(queryClient, options);
+    const detach = observer.subscribe(() => {});
+    try {
+      await Promise.resolve();
+      expect(calls).toBe(0);
+      expect(observer.getCurrentResult().data?.file).toBe(file);
+      await observer.refetch();
+      expect(calls).toBe(1);
+    } finally {
+      detach();
+      queryClient.clear();
+    }
+  });
+
+  it("retries a cached null result when reopened", async () => {
+    const queryClient = new QueryClient();
+    const options = fetchQueryOptions(
+      commitFileDiffQueryOptions({
+        serverId: "host",
+        cwd: "/repo",
+        sha: "abc",
+        path: "a.ts",
+        enabled: true,
+        client: {
+          async getCommitFileDiff() {
+            return { file };
+          },
+        },
+      }),
+    );
+    queryClient.setQueryData(options.queryKey, { file: null });
+    const observer = new QueryObserver(queryClient, options);
+    const settled = Promise.withResolvers<void>();
+    const detach = observer.subscribe((result) => {
+      if (result.fetchStatus === "idle") settled.resolve();
+    });
+    try {
+      await settled.promise;
+      expect(observer.getCurrentResult().data?.file).toEqual(file);
+    } finally {
+      detach();
+      queryClient.clear();
+    }
+  });
+});
diff --git a/packages/app/src/git/commit-file-diff-query.ts b/packages/app/src/git/commit-file-diff-query.ts
new file mode 100644
index 0000000000..5277551234
--- /dev/null
+++ b/packages/app/src/git/commit-file-diff-query.ts
@@ -0,0 +1,28 @@
+import type { DaemonClient } from "@getpaseo/client/internal/daemon-client";
+import { checkoutCommitFileDiffQueryKey, COMMIT_FILE_DIFF_STALE_TIME } from "./query-keys";
+import { shareCommitFileDiff } from "./diff-sharing";
+
+export function commitFileDiffQueryOptions(input: {
+  serverId: string;
+  cwd: string;
+  sha: string;
+  path: string;
+  client: Pick<DaemonClient, "getCommitFileDiff"> | null;
+  enabled: boolean;
+}) {
+  return {
+    queryKey: checkoutCommitFileDiffQueryKey(input.serverId, input.cwd, input.sha, input.path),
+    queryFn: () => {
+      if (!input.client) throw new Error("Host disconnected");
+      return input.client.getCommitFileDiff(input.cwd, input.sha, input.path);
+    },
+    enabled: input.enabled,
+    gcTime: COMMIT_FILE_DIFF_STALE_TIME,
+    // Only successful file bodies are immutable. Null/error results can recover.
+    immutableWhen: (data: Awaited<ReturnType<DaemonClient["getCommitFileDiff"]>>) =>
+      data.file !== null,
+    dataShape: "value" as const,
+    refetchOnWindowFocus: false,
+    structuralSharing: shareCommitFileDiff,
+  };
+}
diff --git a/packages/app/src/git/diff-document/horizontal-scroll.native.tsx b/packages/app/src/git/diff-document/horizontal-scroll.native.tsx
index 993b2048bb..0aa42e01c6 100644
--- a/packages/app/src/git/diff-document/horizontal-scroll.native.tsx
+++ b/packages/app/src/git/diff-document/horizontal-scroll.native.tsx
@@ -26,9 +26,10 @@ export function HorizontalScroll({
   const scrollId = useId();
   const [isAtLeftEdge, setIsAtLeftEdge] = useState(true);
   const edgeRef = useRef(true);
+  const path = file.path;
   const handler = useAnimatedScrollHandler({
     onScroll(event) {
-      offsets.value = { ...offsets.value, [file.path]: event.contentOffset.x };
+      offsets.value = { ...offsets.value, [path]: event.contentOffset.x };
     },
   });
   useEffect(() => {
diff --git a/packages/app/src/git/diff-document/model.test.ts b/packages/app/src/git/diff-document/model.test.ts
index 77d6ae391d..1aa78ab3c6 100644
--- a/packages/app/src/git/diff-document/model.test.ts
+++ b/packages/app/src/git/diff-document/model.test.ts
@@ -71,6 +71,55 @@ function input(overrides: Partial<BuildDiffDocumentModelInput> = {}): BuildDiffD
 }
 
 describe("diff document model", () => {
+  it("materializes only visible rows of a large file while preserving full horizontal extent", () => {
+    const source = file("large.ts");
+    source.hunks[0]!.lines = Array.from({ length: 1000 }, (_, index) => ({
+      type: "add",
+      content: index === 900 ? "a very wide offscreen line ".repeat(20) : `line ${index}`,
+      tokens: [{ text: `line ${index}`, style: null }],
+    }));
+    let advancedCharacters = 0;
+    const measureText: TextMeasurer = {
+      measure: (text) => text.length * 10,
+      measureAdvances(graphemes) {
+        advancedCharacters += graphemes.join("").length;
+        return graphemes.map((_, index) => (index + 1) * 10);
+      },
+    };
+    const base = input({ files: [source], wrapLines: false, viewportWidth: 300, measureText });
+    const eager = buildDiffDocumentModel(base);
+    advancedCharacters = 0;
+    const first = buildDiffDocumentModel({
+      ...base,
+      materializationWindow: { top: FILE_HEADER_HEIGHT, height: 54 },
+    });
+    expect(measuredFragments(first, source.path)).toBe(3);
+    expect(advancedCharacters).toBeLessThan(100);
+    expect(first.height).toBe(eager.height);
+    expect(first.files[0]!.contentWidth).toBe(eager.files[0]!.contentWidth);
+    const priorCells = firstLineCells(first, source.path);
+    advancedCharacters = 0;
+    const next = buildDiffDocumentModel({
+      ...base,
+      reuseFrom: [first],
+      materializationWindow: { top: FILE_HEADER_HEIGHT + 900 * 18, height: 54 },
+    });
+    expect(firstLineCells(next, source.path)).toBe(priorCells);
+    expect(next.rows[900]).toMatchObject({
+      kind: "line",
+      cells: [{ fragments: [{ text: source.hunks[0]!.lines[900]!.content }] }],
+    });
+    expect(advancedCharacters).toBeLessThan(600);
+    expect(next.height).toBe(eager.height);
+    advancedCharacters = 0;
+    buildDiffDocumentModel({
+      ...base,
+      reuseFrom: [next],
+      materializationWindow: { top: FILE_HEADER_HEIGHT, height: 54 },
+    });
+    expect(advancedCharacters).toBe(0);
+  });
+
   it("does not imperatively scroll for a no-op relayout", () => {
     expect(shouldApplyRelayoutScroll(320, 320)).toBe(false);
     expect(shouldApplyRelayoutScroll(320, 320.4)).toBe(false);
diff --git a/packages/app/src/git/diff-document/model.ts b/packages/app/src/git/diff-document/model.ts
index 6267519796..a8b2baed90 100644
--- a/packages/app/src/git/diff-document/model.ts
+++ b/packages/app/src/git/diff-document/model.ts
@@ -157,21 +157,26 @@ function appendReusableFileRows(candidate: {
     !candidate.input.wrapLines &&
     candidate.model.reviewGeometryKey === candidate.reviewGeometryKey &&
     candidate.file.top === candidate.fileTop &&
+    candidate.file.fileIndex === candidate.fileIndex &&
     candidate.file.rowStart === candidate.rows.length;
-  if (retainsRowGeometry) {
-    candidate.rows.push(...reusedRows);
-    return {
-      bottom: candidate.bodyTop + candidate.file.bodyHeight,
-      maximumHorizontalOverflow: Math.max(
-        0,
-        candidate.file.contentWidth - candidate.input.viewportWidth,
-      ),
-    };
-  }
-
   let top = candidate.bodyTop;
   for (const reusedRow of reusedRows) {
-    const nextRow = repositionReusedRow(reusedRow, candidate, top);
+    let nextRow = retainsRowGeometry ? reusedRow : repositionReusedRow(reusedRow, candidate, top);
+    if (
+      nextRow.kind === "line" &&
+      intersectsMaterializationWindow(candidate.input, top, top + nextRow.height) &&
+      nextRow.cells.some((cell) => cell && cell.fragments.length === 0)
+    ) {
+      nextRow = {
+        ...nextRow,
+        cells: materializeCells(
+          nextRow.cells,
+          candidate.file.file,
+          candidate.file.gutterWidth,
+          candidate.input,
+        ),
+      };
+    }
     candidate.rows.push(nextRow);
     top += nextRow.height;
   }
@@ -232,71 +237,45 @@ function appendNewFileRows(candidate: {
     };
   }
 
-  const deferredLines =
-    candidate.input.materializationWindow && !candidate.input.wrapLines
-      ? geometryLines(lineSources(candidate.file, candidate.input.layout, false), candidate.input)
-      : null;
-  const deferredBodyHeight = deferredLines?.reduce((height, line) => height + line.height, 0) ?? 0;
-  const shouldMaterialize =
-    deferredLines === null ||
-    intersectsMaterializationWindow(
-      candidate.input,
-      candidate.fileTop,
-      candidate.bodyTop + deferredBodyHeight + DIFF_BODY_BORDER_HEIGHT,
-    );
-  return shouldMaterialize
-    ? appendMeasuredFileRows(candidate)
-    : appendGeometryFileRows(candidate, deferredLines);
-}
-
-function appendGeometryFileRows(
-  candidate: Parameters<typeof appendNewFileRows>[0],
-  lines: readonly GeometryLine[],
-): FileRowsResult {
-  let top = candidate.bodyTop;
-  for (const line of lines) {
-    candidate.rows.push({
-      kind: "line",
-      index: candidate.rows.length,
-      fileIndex: candidate.fileIndex,
-      path: candidate.file.path,
-      top,
-      height: line.height,
-      cells: line.cells,
-      reviewHeight: line.reviewHeight,
-    });
-    top += line.height;
-  }
-  return { bottom: top + DIFF_BODY_BORDER_HEIGHT, maximumHorizontalOverflow: 0 };
-}
-
-function appendMeasuredFileRows(
-  candidate: Parameters<typeof appendNewFileRows>[0],
-): FileRowsResult {
+  const lines = geometryLines(
+    lineSources(candidate.file, candidate.input.layout, false),
+    candidate.input,
+  );
+  const fileBottom =
+    candidate.bodyTop +
+    lines.reduce((height, line) => height + line.height, 0) +
+    DIFF_BODY_BORDER_HEIGHT;
+  const measureWidth =
+    !candidate.input.wrapLines &&
+    intersectsMaterializationWindow(candidate.input, candidate.fileTop, fileBottom);
   let top = candidate.bodyTop;
   let maximumHorizontalOverflow = 0;
-  for (const sourceCells of lineSources(candidate.file, candidate.input.layout, true)) {
-    const columnCount = sourceCells.length;
-    const columnWidth = candidate.input.viewportWidth / columnCount;
-    const availableWidth = Math.max(
-      candidate.input.measureText.measure("M"),
-      columnWidth - candidate.gutterWidth - CODE_HORIZONTAL_PADDING,
-    );
-    const cells = sourceCells.map((source) => {
-      if (!source) return null;
-      const cell = measureCell({ source, availableWidth, input: candidate.input });
-      maximumHorizontalOverflow = Math.max(
-        maximumHorizontalOverflow,
-        candidate.gutterWidth + CODE_HORIZONTAL_PADDING + measureCellWidth(cell) - columnWidth,
-      );
-      return cell;
-    }) as DiffLineRow["cells"];
+  for (const line of lines) {
+    const shouldMaterialize =
+      candidate.input.wrapLines ||
+      intersectsMaterializationWindow(candidate.input, top, top + line.height);
+    const cells = shouldMaterialize
+      ? materializeCells(line.cells, candidate.file, candidate.gutterWidth, candidate.input)
+      : line.cells;
+    const columnWidth = candidate.input.viewportWidth / cells.length;
+    if (measureWidth) {
+      for (const cell of cells) {
+        if (!cell) continue;
+        const width =
+          cell.fragments.length > 0
+            ? measureCellWidth(cell)
+            : candidate.input.measureText.measure(displayLineText(cell.content));
+        maximumHorizontalOverflow = Math.max(
+          maximumHorizontalOverflow,
+          candidate.gutterWidth + CODE_HORIZONTAL_PADDING + width - columnWidth,
+        );
+      }
+    }
     const textHeight = Math.max(
       candidate.input.typography.lineHeight,
       ...cells.map((cell) => (cell?.fragments.length ?? 1) * candidate.input.typography.lineHeight),
     );
-    const reviewHeight = reviewHeightForCells(cells, candidate.input);
-    const height = textHeight + reviewHeight;
+    const height = textHeight + line.reviewHeight;
     candidate.rows.push({
       kind: "line",
       index: candidate.rows.length,
@@ -305,13 +284,46 @@ function appendMeasuredFileRows(
       top,
       height,
       cells,
-      reviewHeight,
+      reviewHeight: line.reviewHeight,
     });
     top += height;
   }
   return { bottom: top + DIFF_BODY_BORDER_HEIGHT, maximumHorizontalOverflow };
 }
 
+function materializeCells(
+  cells: DiffLineRow["cells"],
+  file: BuildDiffDocumentModelInput["files"][number],
+  gutterWidth: number,
+  input: BuildDiffDocumentModelInput,
+): DiffLineRow["cells"] {
+  const availableWidth = Math.max(
+    input.measureText.measure("M"),
+    input.viewportWidth / cells.length - gutterWidth - CODE_HORIZONTAL_PADDING,
+  );
+  return cells.map((cell) => {
+    if (!cell || cell.fragments.length > 0) return cell;
+    const sourceLine =
+      file.hunks[cell.sourceIdentity.hunkIndex]!.lines[cell.sourceIdentity.lineIndex]!;
+    return measureCell({
+      source: {
+        ...cell,
+        tokenText: cell.type === "header" ? [] : compactHighlightTokens(sourceLine.tokens ?? []),
+      },
+      availableWidth,
+      input,
+    });
+  }) as DiffLineRow["cells"];
+}
+
+function displayLineText(text: string): string {
+  return text.includes("\t")
+    ? segmentGraphemes(text)
+        .map((segment) => segment.text)
+        .join("")
+    : text;
+}
+
 export function reviewGeometryKey(
   reviewActions: BuildDiffDocumentModelInput["reviewActions"],
 ): string {
@@ -334,7 +346,11 @@ export function retainReusableModels(
   previous: readonly DiffDocumentModel[] | undefined,
   next: DiffDocumentModel,
 ): DiffDocumentModel[] {
-  const fullest = [...(previous ?? []), next].reduce((best, candidate) =>
+  const sources = new Set(next.files.map((file) => file.file));
+  const compatible = previous?.filter((model) =>
+    model.files.every((file) => sources.has(file.file)),
+  );
+  const fullest = [...(compatible ?? []), next].reduce((best, candidate) =>
     measuredFileCount(candidate) > measuredFileCount(best) ? candidate : best,
   );
   return fullest === next ? [next] : [fullest, next];
@@ -437,16 +453,17 @@ function intersectsMaterializationWindow(
 
 function hasMeasuredFileRows(model: DiffDocumentModel, file: DiffFileSection): boolean {
   if (file.isCollapsed) return false;
-  return model.rows.slice(file.rowStart, file.rowEnd).every((row) => {
+  return model.rows.slice(file.rowStart, file.rowEnd).some((row) => {
     if (row.kind !== "line") return true;
-    return row.cells.every((cell) => !cell || cell.fragments.length > 0);
+    return row.cells.some((cell) => cell && cell.fragments.length > 0);
   });
 }
 
 function indexReusableModels(
   models: readonly DiffDocumentModel[] | undefined,
 ): ReusableModelIndex[] {
-  return (models ?? []).map((model) => {
+  // The latest model includes text prepared by later scroll windows.
+  return (models ?? []).toReversed().map((model) => {
     const filesBySource = new Map<BuildDiffDocumentModelInput["files"][number], DiffFileSection>();
     const measuredFiles = new Set<DiffFileSection>();
     for (const file of model.files) {
diff --git a/packages/app/src/git/diff-document/surface.native.tsx b/packages/app/src/git/diff-document/surface.native.tsx
index 49c2697169..a6813685e9 100644
--- a/packages/app/src/git/diff-document/surface.native.tsx
+++ b/packages/app/src/git/diff-document/surface.native.tsx
@@ -110,7 +110,6 @@ export function DiffSurface(props: DiffSurfaceProps) {
   const reviewActions = props.mode.kind === "working" ? props.mode.reviewActions : undefined;
   const model = useMemo(() => {
     const dependencies = [
-      props.files,
       props.displayPreferences.layout,
       props.displayPreferences.wrapLines,
       viewport.width,
@@ -172,8 +171,13 @@ export function DiffSurface(props: DiffSurfaceProps) {
     [family, props.palette, typography.lineHeight, typography.size],
   );
   const textLayout = useMemo(
-    () => prepareNativeTextLayout(textLayoutStore, model),
-    [model, textLayoutStore],
+    () =>
+      prepareNativeTextLayout(
+        textLayoutStore,
+        model,
+        diffMaterializationWindow(fileWindowTop, viewport.height),
+      ),
+    [model, textLayoutStore, fileWindowTop, viewport.height],
   );
   useEffect(() => () => disposeNativeTextLayout(textLayoutStore), [textLayoutStore]);
   const headerTextLayout = useMemo(
@@ -386,11 +390,12 @@ function NativeCanvasFileHeader({
     () => recordNativeHeaderPicture({ file, viewportWidth, textLayout, paints }),
     [file, paints, textLayout, viewportWidth],
   );
+  const { top, bottom, headerHeight } = file;
   const stickyStyle = useAnimatedStyle(() => {
-    const pinOffset = Math.max(0, scrollTop.value - file.top);
-    const maximumPinOffset = Math.max(0, file.bottom - file.headerHeight - file.top);
+    const pinOffset = Math.max(0, scrollTop.value - top);
+    const maximumPinOffset = Math.max(0, bottom - headerHeight - top);
     return { transform: [{ translateY: Math.min(pinOffset, maximumPinOffset) }] };
-  }, [file.bottom, file.headerHeight, file.top, scrollTop]);
+  }, [bottom, headerHeight, top, scrollTop]);
   const style = useMemo<ViewStyle>(
     () => ({
       position: "absolute",
diff --git a/packages/app/src/git/diff-document/text-measurement.test.ts b/packages/app/src/git/diff-document/text-measurement.test.ts
index 476ef3e45d..144676e550 100644
--- a/packages/app/src/git/diff-document/text-measurement.test.ts
+++ b/packages/app/src/git/diff-document/text-measurement.test.ts
@@ -55,6 +55,7 @@ describe("cached ASCII text metrics", () => {
 
     expect(metrics.measureAdvances(["a", "b", "a"])).toEqual([10, 20, 30]);
     expect(metrics.measureAdvances(["b", "a"])).toEqual([10, 20]);
+    expect(metrics.measure("abba")).toBe(40);
     expect(measured).toEqual(["a", "b"]);
   });
 
diff --git a/packages/app/src/git/diff-document/text-measurement.ts b/packages/app/src/git/diff-document/text-measurement.ts
index 92b245ad73..a141d170a7 100644
--- a/packages/app/src/git/diff-document/text-measurement.ts
+++ b/packages/app/src/git/diff-document/text-measurement.ts
@@ -6,6 +6,8 @@ export interface PrimaryTextFace {
 }
 
 export interface CachedAsciiTextMetrics {
+  /** Whole-line width after checking glyph coverage and excluding shaping. */
+  measure(text: string): number;
   hasEveryGlyph(text: string): boolean;
   measureAdvances(graphemes: readonly string[]): number[];
 }
@@ -97,24 +99,39 @@ export function advancesFor(measurer: TextMeasurer): (graphemes: readonly string
 export function createAdditiveAdvances(
   measure: (text: string) => number,
 ): (graphemes: readonly string[]) => number[] {
+  return additiveAdvances(cachedWidths(measure));
+}
+
+function cachedWidths(measure: (text: string) => number): (text: string) => number {
   const widths = new Map<string, number>();
+  return (text) => {
+    let width = widths.get(text);
+    if (width === undefined) {
+      width = measure(text);
+      widths.set(text, width);
+    }
+    return width;
+  };
+}
+
+function additiveAdvances(
+  measure: (text: string) => number,
+): (graphemes: readonly string[]) => number[] {
   return (graphemes) => {
     let advance = 0;
-    return graphemes.map((grapheme) => {
-      let width = widths.get(grapheme);
-      if (width === undefined) {
-        width = measure(grapheme);
-        widths.set(grapheme, width);
-      }
-      advance += width;
-      return advance;
-    });
+    return graphemes.map((grapheme) => (advance += measure(grapheme)));
   };
 }
 
 export function createCachedAsciiTextMetrics(primary: PrimaryTextFace): CachedAsciiTextMetrics {
   const glyphCoverage = new Map<string, boolean>();
+  const measure = cachedWidths((text) => primary.measure(text));
   return {
+    measure(text) {
+      let width = 0;
+      for (const character of text) width += measure(character);
+      return width;
+    },
     hasEveryGlyph(text) {
       for (const character of text) {
         let hasGlyph = glyphCoverage.get(character);
@@ -126,7 +143,7 @@ export function createCachedAsciiTextMetrics(primary: PrimaryTextFace): CachedAs
       }
       return true;
     },
-    measureAdvances: createAdditiveAdvances((text) => primary.measure(text)),
+    measureAdvances: additiveAdvances(measure),
   };
 }
 
diff --git a/packages/app/src/git/diff-document/text.native.ts b/packages/app/src/git/diff-document/text.native.ts
index 2f0252b384..0c6f16bb5d 100644
--- a/packages/app/src/git/diff-document/text.native.ts
+++ b/packages/app/src/git/diff-document/text.native.ts
@@ -5,12 +5,11 @@ import {
   type SkFont,
   type SkParagraph,
 } from "@shopify/react-native-skia";
-import { fragmentTextForRange } from "./model";
+import { fragmentTextForRange, visibleRowRange } from "./model";
 import { codeTextColor } from "./palette";
 import {
   createCachedAsciiTextMetrics,
   createChunkedAdvanceMeasurer,
-  createFallbackAwareTextMeasurer,
   requiresShaping,
   type CachedAsciiTextMetrics,
 } from "./text-measurement";
@@ -86,7 +85,8 @@ export function shapeNativeHeaderText(input: {
 export interface NativeTextLayoutStore {
   font: SkFont;
   asciiMetrics: CachedAsciiTextMetrics;
-  paragraphsByCell: WeakMap<DiffCell, Array<SkParagraph | null>>;
+  paragraphsByCell: Map<DiffCell, Array<SkParagraph | null>>;
+  textStyles: Map<string, ReturnType<typeof textStyle>>;
   ownedParagraphs: Set<SkParagraph>;
   families: string[];
   fontSize: number;
@@ -97,6 +97,8 @@ export interface NativeTextLayoutStore {
 export function disposeNativeTextLayout(layout: NativeTextLayoutStore): void {
   for (const paragraph of layout.ownedParagraphs) paragraph.dispose();
   layout.ownedParagraphs.clear();
+  layout.paragraphsByCell.clear();
+  layout.textStyles.clear();
   layout.font.dispose();
 }
 
@@ -114,7 +116,8 @@ export function createNativeTextLayoutStore(input: {
       glyphIds: (text) => font.getGlyphIDs(text),
       measure: (text) => font.getTextWidth(text),
     }),
-    paragraphsByCell: new WeakMap(),
+    paragraphsByCell: new Map(),
+    textStyles: new Map(),
     ownedParagraphs: new Set(),
     families,
     fontSize: input.fontSize,
@@ -126,30 +129,64 @@ export function createNativeTextLayoutStore(input: {
 export function prepareNativeTextLayout(
   store: NativeTextLayoutStore,
   model: DiffDocumentModel,
+  window?: { top: number; height: number },
 ): NativeTextLayout {
-  const paragraphs = model.rows.map((row) => {
-    if (row.kind !== "line") return [];
-    return row.cells.map((cell) => {
+  const range = window
+    ? visibleRowRange(model.rows, window.top, window.height)
+    : { start: 0, end: model.rows.length };
+  const retainedCells = new Set<DiffCell>();
+  const retainedParagraphs = new Set<SkParagraph>();
+  const paragraphs: NativeTextLayout["paragraphs"] = [];
+  paragraphs.length = model.rows.length;
+  for (let index = range.start; index < range.end; index++) {
+    const row = model.rows[index]!;
+    if (row.kind !== "line") continue;
+    paragraphs[index] = row.cells.map((cell) => {
       if (!cell) return [];
+      retainedCells.add(cell);
       const cached = store.paragraphsByCell.get(cell);
-      if (cached) return cached;
-      const cellParagraphs = cell.fragments.map((fragment) => {
-        if (!requiresRetainedParagraph(fragment.text, store.asciiMetrics)) return null;
-        const paragraph = createFragmentParagraph({
-          cell,
-          fragment,
-          families: store.families,
-          fontSize: store.fontSize,
-          lineHeight: store.lineHeight,
-          palette: store.palette,
-        });
+      const start = window ? Math.max(0, Math.floor((window.top - row.top) / model.lineHeight)) : 0;
+      const end = window
+        ? Math.min(
+            cell.fragments.length,
+            Math.ceil((window.top + window.height - row.top) / model.lineHeight),
+          )
+        : cell.fragments.length;
+      const cellParagraphs: Array<SkParagraph | null> = [];
+      cellParagraphs.length = cell.fragments.length;
+      for (let fragmentIndex = start; fragmentIndex < end; fragmentIndex++) {
+        const fragment = cell.fragments[fragmentIndex]!;
+        if (!requiresRetainedParagraph(fragment.text, store.asciiMetrics)) {
+          cellParagraphs[fragmentIndex] = null;
+          continue;
+        }
+        const paragraph =
+          cached?.[fragmentIndex] ??
+          createFragmentParagraph({
+            cell,
+            fragment,
+            families: store.families,
+            fontSize: store.fontSize,
+            lineHeight: store.lineHeight,
+            palette: store.palette,
+            textStyles: store.textStyles,
+          });
         store.ownedParagraphs.add(paragraph);
-        return paragraph;
-      });
+        retainedParagraphs.add(paragraph);
+        cellParagraphs[fragmentIndex] = paragraph;
+      }
       store.paragraphsByCell.set(cell, cellParagraphs);
       return cellParagraphs;
     });
-  });
+  }
+  for (const paragraph of store.ownedParagraphs) {
+    if (retainedParagraphs.has(paragraph)) continue;
+    paragraph.dispose();
+    store.ownedParagraphs.delete(paragraph);
+  }
+  for (const cell of store.paragraphsByCell.keys()) {
+    if (!retainedCells.has(cell)) store.paragraphsByCell.delete(cell);
+  }
   return { font: store.font, paragraphs };
 }
 
@@ -164,23 +201,25 @@ export function createNativeTextMeasurer(input: {
     measure: (text: string) => font.getTextWidth(text),
   };
   const asciiMetrics = createCachedAsciiTextMetrics(primary);
-  const fallbackAware = createFallbackAwareTextMeasurer({
-    primary,
-    measureWithSystemFallback(text) {
-      const paragraph = createParagraph({
-        text,
-        families,
-        fontSize: input.fontSize,
-        lineHeight: Math.round(input.fontSize * 1.5),
-        color: Skia.Color("black"),
-      });
-      const width = paragraph.getLongestLine();
-      paragraph.dispose();
-      return width;
-    },
-  });
+  const black = Skia.Color("black");
+  const measureParagraph = (text: string) => {
+    const paragraph = createParagraph({
+      text,
+      families,
+      fontSize: input.fontSize,
+      lineHeight: Math.round(input.fontSize * 1.5),
+      color: black,
+    });
+    const width = paragraph.getLongestLine();
+    paragraph.dispose();
+    return width;
+  };
   return {
-    ...fallbackAware,
+    measure(text) {
+      return requiresRetainedParagraph(text, asciiMetrics)
+        ? measureParagraph(text)
+        : asciiMetrics.measure(text);
+    },
     measureAdvances: createChunkedAdvanceMeasurer({
       requiresShaping: (text) => requiresRetainedParagraph(text, asciiMetrics),
       measureAdditive: (graphemes) => asciiMetrics.measureAdvances(graphemes),
@@ -190,7 +229,7 @@ export function createNativeTextMeasurer(input: {
           families,
           fontSize: input.fontSize,
           lineHeight: Math.round(input.fontSize * 1.5),
-          color: Skia.Color("black"),
+          color: black,
         });
         let end = 0;
         const advances = graphemes.map((grapheme) => {
@@ -219,23 +258,21 @@ function createFragmentParagraph(input: {
   fontSize: number;
   lineHeight: number;
   palette: DiffPalette;
+  textStyles: NativeTextLayoutStore["textStyles"];
 }): SkParagraph {
   const builder = Skia.ParagraphBuilder.Make(
     paragraphStyle(input.families, input.fontSize, input.lineHeight),
   );
   if (input.cell.tokens.length === 0 || input.cell.type === "header") {
     const color = codeTextColor(input.cell, input.palette);
-    builder
-      .pushStyle(textStyle(input.families, input.fontSize, color))
-      .addText(input.fragment.text)
-      .pop();
+    builder.pushStyle(retainedTextStyle(input, color)).addText(input.fragment.text).pop();
   } else {
     for (const run of input.cell.tokens) {
       const start = Math.max(input.fragment.start, run.start);
       const end = Math.min(input.fragment.end, run.end);
       if (end <= start) continue;
       builder
-        .pushStyle(textStyle(input.families, input.fontSize, run.color))
+        .pushStyle(retainedTextStyle(input, run.color))
         .addText(fragmentTextForRange(input.fragment, start, end))
         .pop();
     }
@@ -281,6 +318,18 @@ function paragraphStyle(families: string[], fontSize: number, lineHeight: number
   };
 }
 
+function retainedTextStyle(
+  input: { families: string[]; fontSize: number; textStyles: NativeTextLayoutStore["textStyles"] },
+  color: string,
+) {
+  let style = input.textStyles.get(color);
+  if (!style) {
+    style = textStyle(input.families, input.fontSize, color);
+    input.textStyles.set(color, style);
+  }
+  return style;
+}
+
 function textStyle(families: string[], fontSize: number, color: string) {
   return { fontFamilies: families, fontSize, color: Skia.Color(color) };
 }
diff --git a/packages/app/src/git/diff-document/workspace-cache.test.ts b/packages/app/src/git/diff-document/workspace-cache.test.ts
index 4a27cc3d44..ddf9972a46 100644
--- a/packages/app/src/git/diff-document/workspace-cache.test.ts
+++ b/packages/app/src/git/diff-document/workspace-cache.test.ts
@@ -78,6 +78,40 @@ function modelInput(
 }
 
 describe("diff document workspace cache", () => {
+  it("keeps text prepared in each visited window of the same file", () => {
+    const cache = createDiffDocumentWorkspaceCache();
+    const source = diffFile();
+    source.hunks[0]!.lines = Array.from({ length: 100 }, (_, index) => ({
+      type: "add",
+      content: `const value${index} = ${index};`,
+    }));
+    const { measureText, stats } = countingMeasurer();
+    const input = modelInput([source], measureText);
+    for (const top of [30, 300, 600]) {
+      cache.buildModel({ ...input, materializationWindow: { top, height: 54 } });
+    }
+    stats.calls = 0;
+    cache.buildModel({ ...input, materializationWindow: { top: 300, height: 54 } });
+    expect(stats.calls).toBe(0);
+  });
+
+  it("retains text cells for unchanged files when another file changes", () => {
+    const cache = createDiffDocumentWorkspaceCache();
+    const { measureText } = countingMeasurer();
+    const files = [diffFile(), { ...diffFile(), path: "b.ts" }];
+    const first = cache.buildModel(modelInput(files, measureText));
+    const replacement = structuredClone(files[0]!);
+    replacement.hunks[0]!.lines[0]!.content = "changed text";
+    const next = cache.buildModel(modelInput([replacement, files[1]!], measureText));
+    const oldRow = first.rows[first.files[1]!.rowStart]!;
+    const nextRow = next.rows[next.files[1]!.rowStart]!;
+    expect(oldRow.kind).toBe("line");
+    expect(nextRow.kind).toBe("line");
+    if (oldRow.kind !== "line" || nextRow.kind !== "line") throw new Error("Missing file text");
+    expect(nextRow.cells).toBe(oldRow.cells);
+    expect(next.files[0]!.file).toBe(replacement);
+  });
+
   it("reuses measured rows until a model-building input changes", () => {
     const cache = createDiffDocumentWorkspaceCache();
     const files = [diffFile()];
@@ -115,7 +149,7 @@ describe("diff document workspace cache", () => {
 
     stats.calls = 0;
     cache.buildModel({ ...input, files: [...files] });
-    expect(stats.calls).toBeGreaterThan(0);
+    expect(stats.calls).toBe(0);
   });
 
   it("bounds retained geometry variants for one diff payload", () => {
@@ -152,7 +186,7 @@ describe("diff document workspace cache", () => {
     const files = [diffFile(), { ...diffFile(), path: "src/b.ts" }];
     const { measureText, stats } = countingMeasurer();
     const first = cache.buildModel(
-      modelInput(files, measureText, { materializationWindow: { top: 0, height: 20 } }),
+      modelInput(files, measureText, { materializationWindow: { top: 30, height: 20 } }),
     );
     const firstCalls = stats.calls;
     const secondFile = first.files[1]!;
diff --git a/packages/app/src/git/diff-document/workspace-cache.tsx b/packages/app/src/git/diff-document/workspace-cache.tsx
index 270c7392ca..bd52000af3 100644
--- a/packages/app/src/git/diff-document/workspace-cache.tsx
+++ b/packages/app/src/git/diff-document/workspace-cache.tsx
@@ -13,6 +13,7 @@ const MAX_MODEL_VARIANTS = 4;
 const MAX_TYPOGRAPHY_RESOURCES = 4;
 
 interface ModelVariant {
+  measureText: TextMeasurer;
   key: string;
   exactKey: string;
   model: DiffDocumentModel;
@@ -38,23 +39,29 @@ export interface DiffDocumentWorkspaceCache {
 }
 
 export function createDiffDocumentWorkspaceCache(): DiffDocumentWorkspaceCache {
-  const variantsByFiles = new WeakMap<BuildDiffDocumentModelInput["files"], ModelVariant[]>();
+  let variants: ModelVariant[] = [];
   const typographyResources = new Map<string, DiffTypographyResource>();
 
   return {
     buildModel(input) {
       const key = modelVariantKey(input);
       const exactKey = exactModelKey(input);
-      const variants = variantsByFiles.get(input.files) ?? [];
-      const variantIndex = variants.findIndex((candidate) => candidate.key === key);
+      const variantIndex = variants.findIndex(
+        (candidate) => candidate.key === key && candidate.measureText === input.measureText,
+      );
       const variant = variantIndex === -1 ? undefined : variants[variantIndex];
-      if (variant?.exactKey === exactKey) {
+      if (
+        variant?.exactKey === exactKey &&
+        variant.model.files.length === input.files.length &&
+        variant.model.files.every((file, index) => file.file === input.files[index])
+      ) {
         variants.splice(variantIndex, 1);
         variants.unshift(variant);
         return variant.model;
       }
       const model = buildDiffDocumentModel({ ...input, reuseFrom: variant?.models });
       const nextVariant = {
+        measureText: input.measureText,
         key,
         exactKey,
         model,
@@ -62,7 +69,7 @@ export function createDiffDocumentWorkspaceCache(): DiffDocumentWorkspaceCache {
       };
       if (variantIndex !== -1) variants.splice(variantIndex, 1);
       variants.unshift(nextVariant);
-      variantsByFiles.set(input.files, variants.slice(0, MAX_MODEL_VARIANTS));
+      variants = variants.slice(0, MAX_MODEL_VARIANTS);
       return model;
     },
     typography(input) {
diff --git a/packages/app/src/git/diff-sharing.test.ts b/packages/app/src/git/diff-sharing.test.ts
new file mode 100644
index 0000000000..210c0f1a4b
--- /dev/null
+++ b/packages/app/src/git/diff-sharing.test.ts
@@ -0,0 +1,148 @@
+import type { ParsedDiffFile } from "@getpaseo/protocol/messages";
+import { describe, expect, it } from "vitest";
+import { retainDiffFiles, shareCheckoutDiff, shareCommitFileDiff } from "./diff-sharing";
+
+const file: ParsedDiffFile = {
+  path: "a.ts",
+  oldPath: "old-a.ts",
+  status: "ok",
+  isNew: false,
+  isDeleted: false,
+  additions: 1,
+  deletions: 1,
+  hunks: [
+    {
+      oldStart: 1,
+      oldCount: 1,
+      newStart: 1,
+      newCount: 1,
+      lines: [
+        {
+          type: "add",
+          content: "const a",
+          tokens: [
+            { text: "const", style: "keyword" },
+            { text: " a", style: null },
+          ],
+        },
+      ],
+    },
+  ],
+};
+
+// Exhaustive keys make a protocol-field addition require a sharing-policy test.
+const fileChanges = {
+  path: (value) => {
+    value.path = "b.ts";
+  },
+  oldPath: (value) => {
+    delete value.oldPath;
+  },
+  status: (value) => {
+    value.status = "binary";
+  },
+  isNew: (value) => {
+    value.isNew = true;
+  },
+  isDeleted: (value) => {
+    value.isDeleted = true;
+  },
+  additions: (value) => {
+    value.additions = 2;
+  },
+  deletions: (value) => {
+    value.deletions = 2;
+  },
+  hunks: (value) => {
+    value.hunks = [];
+  },
+} satisfies Record<keyof ParsedDiffFile, (value: ParsedDiffFile) => void>;
+type Hunk = ParsedDiffFile["hunks"][number];
+const hunkChanges = {
+  oldStart: (value) => {
+    value.oldStart = 2;
+  },
+  oldCount: (value) => {
+    value.oldCount = 2;
+  },
+  newStart: (value) => {
+    value.newStart = 2;
+  },
+  newCount: (value) => {
+    value.newCount = 2;
+  },
+  lines: (value) => {
+    value.lines = [];
+  },
+} satisfies Record<keyof Hunk, (value: Hunk) => void>;
+type Line = Hunk["lines"][number];
+const lineChanges = {
+  type: (value) => {
+    value.type = "remove";
+  },
+  content: (value) => {
+    value.content = "const b";
+  },
+  tokens: (value) => {
+    delete value.tokens;
+  },
+} satisfies Record<keyof Line, (value: Line) => void>;
+type Token = NonNullable<Line["tokens"]>[number];
+const tokenChanges = {
+  text: (value) => {
+    value.text = "class";
+  },
+  style: (value) => {
+    value.style = null;
+  },
+} satisfies Record<keyof Token, (value: Token) => void>;
+
+describe("diff sharing", () => {
+  it.each(Object.entries(fileChanges))("replaces a file when %s changes", (_, change) => {
+    const next = structuredClone(file);
+    change(next);
+    expect(retainDiffFiles([file], [next])[0]).toBe(next);
+  });
+  it.each(Object.entries(hunkChanges))("replaces a file when hunk %s changes", (_, change) => {
+    const next = structuredClone(file);
+    change(next.hunks[0]!);
+    expect(retainDiffFiles([file], [next])[0]).toBe(next);
+  });
+  it.each(Object.entries(lineChanges))("replaces a file when line %s changes", (_, change) => {
+    const next = structuredClone(file);
+    change(next.hunks[0]!.lines[0]!);
+    expect(retainDiffFiles([file], [next])[0]).toBe(next);
+  });
+  it.each(Object.entries(tokenChanges))("replaces a file when token %s changes", (_, change) => {
+    const next = structuredClone(file);
+    change(next.hunks[0]!.lines[0]!.tokens![0]!);
+    expect(retainDiffFiles([file], [next])[0]).toBe(next);
+  });
+  it("retains moved files and removes missing files", () => {
+    const second = { ...file, path: "b.ts" };
+    const reordered = retainDiffFiles([file, second], structuredClone([second, file]));
+    expect(reordered[0]).toBe(second);
+    expect(reordered[1]).toBe(file);
+    expect(retainDiffFiles(reordered, [structuredClone(file)])[0]).toBe(file);
+  });
+  it("updates response metadata without invalidating unchanged text", () => {
+    const previous = { cwd: "/repo", files: [file], error: null, requestId: "a" };
+    expect(shareCheckoutDiff(previous, structuredClone(previous))).toBe(previous);
+    const next = shareCheckoutDiff(previous, { ...structuredClone(previous), requestId: "b" });
+    expect(next.requestId).toBe("b");
+    expect(next.files).toBe(previous.files);
+    const rejected = {
+      ...previous,
+      files: [],
+      error: { code: "UNKNOWN", message: "Too large" },
+      diffTooLarge: true,
+    };
+    expect(shareCheckoutDiff(next, rejected)).toEqual(rejected);
+  });
+  it("preserves cached commit bodies and publishes null transitions", () => {
+    const previous = { file };
+    expect(shareCommitFileDiff(previous, structuredClone(previous))).toBe(previous);
+    expect(shareCommitFileDiff(previous, { file: null })).toEqual({ file: null });
+    expect(shareCommitFileDiff({ file: null }, previous)).toBe(previous);
+  });
+});
diff --git a/packages/app/src/git/diff-sharing.ts b/packages/app/src/git/diff-sharing.ts
new file mode 100644
index 0000000000..6bdac10ddf
--- /dev/null
+++ b/packages/app/src/git/diff-sharing.ts
@@ -0,0 +1,98 @@
+import { replaceEqualDeep } from "@tanstack/react-query";
+import type { ParsedDiffFile, SubscribeCheckoutDiffResponse } from "@getpaseo/protocol/messages";
+
+type DiffPayload = Omit<SubscribeCheckoutDiffResponse["payload"], "subscriptionId">;
+
+/** File identity owns text-model reuse. Never reconstruct the hunk/token graph. */
+export function retainDiffFiles(
+  previous: ParsedDiffFile[],
+  incoming: ParsedDiffFile[],
+): ParsedDiffFile[] {
+  if (previous === incoming) return previous;
+  const byPath = new Map(previous.map((file) => [file.path, file]));
+  let unchanged = previous.length === incoming.length;
+  const files = incoming.map((file, index) => {
+    const old = byPath.get(file.path);
+    const retained = old && equalFile(old, file) ? old : file;
+    unchanged &&= retained === previous[index];
+    return retained;
+  });
+  return unchanged ? previous : files;
+}
+
+export function shareCheckoutDiff(previous: unknown, incoming: unknown): DiffPayload {
+  const next = incoming as DiffPayload;
+  const old = previous as DiffPayload | undefined;
+  if (!old || old === next) return next;
+  const files = retainDiffFiles(old.files, next.files);
+  const error = replaceEqualDeep(old.error, next.error);
+  return files === old.files &&
+    error === old.error &&
+    old.cwd === next.cwd &&
+    old.requestId === next.requestId &&
+    old.diffTooLarge === next.diffTooLarge
+    ? old
+    : { ...next, files, error };
+}
+
+export function shareCommitFileDiff(
+  previous: unknown,
+  incoming: unknown,
+): { file: ParsedDiffFile | null } {
+  const next = incoming as { file: ParsedDiffFile | null };
+  const old = previous as typeof next | undefined;
+  return old &&
+    (old.file === next.file || (old.file && next.file && equalFile(old.file, next.file)))
+    ? old
+    : next;
+}
+
+function equalFile(left: ParsedDiffFile, right: ParsedDiffFile): boolean {
+  if (left === right) return true;
+  if (
+    left.path !== right.path ||
+    left.oldPath !== right.oldPath ||
+    left.status !== right.status ||
+    left.isNew !== right.isNew ||
+    left.isDeleted !== right.isDeleted ||
+    left.additions !== right.additions ||
+    left.deletions !== right.deletions ||
+    left.hunks.length !== right.hunks.length
+  )
+    return false;
+  for (let h = 0; h < left.hunks.length; h++) {
+    const a = left.hunks[h]!;
+    const b = right.hunks[h]!;
+    if (a === b) continue;
+    if (
+      a.oldStart !== b.oldStart ||
+      a.oldCount !== b.oldCount ||
+      a.newStart !== b.newStart ||
+      a.newCount !== b.newCount ||
+      a.lines.length !== b.lines.length
+    )
+      return false;
+    if (!equalLines(a.lines, b.lines)) return false;
+  }
+  return true;
+}
+
+function equalLines(
+  left: ParsedDiffFile["hunks"][number]["lines"],
+  right: ParsedDiffFile["hunks"][number]["lines"],
+): boolean {
+  for (let l = 0; l < left.length; l++) {
+    const x = left[l]!;
+    const y = right[l]!;
+    if (x === y) continue;
+    if (x.type !== y.type || x.content !== y.content) return false;
+    if (x.tokens === y.tokens) continue;
+    if (!x.tokens || !y.tokens || x.tokens.length !== y.tokens.length) return false;
+    for (let t = 0; t < x.tokens.length; t++) {
+      const p = x.tokens[t]!;
+      const q = y.tokens[t]!;
+      if (p.text !== q.text || p.style !== q.style) return false;
+    }
+  }
+  return true;
+}
diff --git a/packages/app/src/git/use-diff-files.ts b/packages/app/src/git/use-diff-files.ts
index 14a17edcb1..9623a31171 100644
--- a/packages/app/src/git/use-diff-files.ts
+++ b/packages/app/src/git/use-diff-files.ts
@@ -2,7 +2,7 @@ import { useMemo } from "react";
 import type { CheckoutCommitFile, ParsedDiffFile } from "@getpaseo/protocol/messages";
 import { useRetainedPanelActive } from "@/components/retained-panel";
 import { useFetchQueries } from "@/data/query";
-import { checkoutCommitFileDiffQueryKey, COMMIT_FILE_DIFF_STALE_TIME } from "@/git/query-keys";
+import { commitFileDiffQueryOptions } from "./commit-file-diff-query";
 import { useCheckoutCommitsQuery } from "@/git/use-commits-query";
 import { useHostRuntimeClient, useHostRuntimeIsConnected } from "@/runtime/host-runtime";
 
@@ -79,18 +79,16 @@ export function useCommitDiffFiles(ctx: CommitDiffFilesContext): CommitDiffFiles
     Boolean(client) &&
     isConnected;
   const fileDiffResults = useFetchQueries(
-    commitFiles.map((file) => ({
-      queryKey: checkoutCommitFileDiffQueryKey(serverId, cwd, sha, file.path),
-      queryFn: async (): Promise<{ file: ParsedDiffFile | null }> => {
-        if (!client) {
-          throw new Error("Host disconnected");
-        }
-        return client.getCommitFileDiff(cwd, sha, file.path);
-      },
-      enabled: fileDiffsEnabled,
-      staleTimeMs: COMMIT_FILE_DIFF_STALE_TIME,
-      dataShape: "value" as const,
-    })),
+    commitFiles.map((file) =>
+      commitFileDiffQueryOptions({
+        serverId,
+        cwd,
+        sha,
+        path: file.path,
+        client,
+        enabled: fileDiffsEnabled,
+      }),
+    ),
   );
   const commitsLoading = commitsQuery.status === "connecting" || commitsQuery.status === "loading";
   const commitsError = commitsQuery.status === "error" ? commitsQuery.error : null;
diff --git a/packages/app/src/git/use-diff-query.ts b/packages/app/src/git/use-diff-query.ts
index 7002bbfc55..35ef268dac 100644
--- a/packages/app/src/git/use-diff-query.ts
+++ b/packages/app/src/git/use-diff-query.ts
@@ -1,3 +1,4 @@
+import { shareCheckoutDiff } from "./diff-sharing";
 import { useMemo } from "react";
 import { useRetainedPanelActive } from "@/components/retained-panel";
 import { useReplicaQuery } from "@/data/query";
@@ -74,6 +75,7 @@ export function useCheckoutDiffQuery({
 
   const query = useReplicaQuery<CheckoutDiffQueryPayload>({
     queryKey,
+    structuralSharing: shareCheckoutDiff,
     enabled: routeEnabled,
     pushEvent: "checkout_diff_update",
     meta: checkoutDiffPushRoute({
diff --git a/packages/app/src/hooks/use-providers-snapshot.ts b/packages/app/src/hooks/use-providers-snapshot.ts
index f79bcbc065..dc90c18f06 100644
--- a/packages/app/src/hooks/use-providers-snapshot.ts
+++ b/packages/app/src/hooks/use-providers-snapshot.ts
@@ -79,6 +79,8 @@ export function useProvidersSnapshot(
 
   const snapshotQuery = useReplicaQuery({
     queryKey,
+    // The content-hash cache already owns catalog and model identity.
+    structuralSharing: false,
     enabled: Boolean(enabled && supportsSnapshot && serverId && client && isConnected),
     pushEvent: "providers_snapshot_update",
     queryFn: async ({ signal }) => {
@@ -149,6 +151,7 @@ export function prefetchProvidersSnapshot(
   void singletonQueryClient.prefetchQuery({
     queryKey,
     staleTime: Infinity,
+    structuralSharing: false,
     queryFn: ({ signal }) =>
       fetchProvidersSnapshot({ client, serverId, cwd, queryClient: singletonQueryClient, signal }),
   });