README.md

@@ -788,7 +788,8 @@ subsequent runs, existing originals are skipped. If a download fails, the error
 is logged and the backup continues with the next file. The exit code is non-zero
 if any files failed. `quak backup` opens its library with the thumbnail and
 originals precache off, so the only file content it fetches is the originals the
-backup stores.
+backup stores. It also opens it with no background timer, so it asks the server
+for changes only as it starts, not again while it downloads.
 
 With `--verify`, or `lib.backup({ verify: true })`, a run also hashes each
 original already at its save path the way a download is checked (see "On-disk
@@ -869,7 +870,7 @@ background, so an unreachable server does not block opening.
 | `client`                 | required                                           | the account client (a `Client`, or any `LibraryClient`)              |
 | `cacheDirectory`         | `quak/<userID>` under the per-user cache directory | where `metadata.json` and the content cache live                     |
 | `downloadDirectory`      | `photos` in the working directory                  | root of the save paths; an original stored there counts as cached    |
-| `refreshIntervalSeconds` | `3`                                                | background refresh cadence                                           |
+| `refreshIntervalSeconds` | `3`                                                | background refresh cadence; `Infinity` for no background timer       |
 | `precacheThumbnails`     | `true`                                             | prefetch every thumbnail, newest first                               |
 | `precacheOriginals`      | `true`                                             | prefetch the favorites album and the latest-window originals         |
 | `precacheOriginalsDays`  | `7`                                                | length in days of that latest window                                 |

TODO.md

@@ -25,6 +25,13 @@ declares one.
 
 # Completed Steps
 
+- 2026-10-14: `quak backup` no longer asks the server for changes every 3
+  seconds while it runs (issue 183). It opens its library with
+  `refreshIntervalSeconds: Infinity`, which the library now takes as no
+  background timer, so the backup refreshes only as it starts and no timed
+  refresh starts another ML data pass during the run. A test holds a backup's
+  download open while two hours pass and counts its `/collections/v2` requests.
+
 - 2026-10-14: `test/cli/backup-end-to-end.test.ts` runs `quak backup` as cron
   does (issue 186): `backupCommand` and `run`, the real `loadSession` reading a
   session saved after logging in, and every request answered by a fake of the

src/cli-commands.ts

@@ -427,10 +427,13 @@ export const backupCommand = async (
     try {
         // The precache is off: the backup fetches what it needs, and must not
         // also fill the cache with every thumbnail and the recent originals.
+        // No refresh starts on a timer: the backup lists its files once, from
+        // the refresh it waits for, and can run for hours.
         const lib = await Library.open({
             client,
             downloadDirectory: dir,
             cacheDirectory: ctx.cacheDir,
+            refreshIntervalSeconds: Infinity,
             precacheThumbnails: false,
             precacheOriginals: false,
         });

src/library/index.ts

@@ -179,6 +179,9 @@ export interface LibraryOptions {
     // directory at open. The content cache treats an original already stored
     // at its save path as present.
     downloadDirectory?: string;
+    // How long after one refresh ends the background timer starts the next.
+    // `Infinity` starts none: the library then refreshes only as it opens and
+    // when `fresh()` or `backup()` asks.
     refreshIntervalSeconds?: number;
     onProgress?: RefreshProgressCallback;
     // The bounded request pools (issue #45), shared by the ML-data fetch (the
@@ -627,7 +630,8 @@ export class Library {
     }
 
     private scheduleNext(): void {
-        if (this.closed) return;
+        // `setTimeout` would turn an infinite delay into 1 ms.
+        if (this.closed || this.intervalMs === Infinity) return;
         this.timer = setTimeout(() => {
             void this.runRefresh().then(() => this.scheduleNext());
         }, this.intervalMs);

test/cli/commands.test.ts

@@ -25,6 +25,7 @@ import { join } from "node:path";
 import { tmpdir } from "node:os";
 import { PassThrough } from "node:stream";
 import * as jpegJs from "jpeg-js";
+import sodium from "libsodium-wrappers-sumo";
 import {
     describe,
     it,
@@ -55,7 +56,7 @@ import { loadSession } from "../../src/cli-session.js";
 import type { Client, ClientSnapshot, LoginOptions } from "../../src/client.js";
 import { savePath, type ContentSource } from "../../src/library/content.js";
 import type { Collection, EnteFile } from "../../src/model/types.js";
-import { init, toBase64 } from "../../src/crypto/index.js";
+import { encryptBlob, init, toBase64 } from "../../src/crypto/index.js";
 import { defaultCacheDirectory } from "../../src/library/index.js";
 import { HEIC_WITH_EXIF } from "../exif-heic.js";
 import {
@@ -903,6 +904,146 @@ describe("backup", () => {
         // Opening the library would have made its cache directory.
         expect(existsSync(join(root, "cache"))).toBe(false);
     });
+
+    // A backup runs for as long as its downloads take, hours on a large
+    // account. It lists its files from the refresh it waits for as it starts,
+    // so it must not ask the server for changes again on a timer while it
+    // runs: each refresh is a request, and each also starts a pass that asks
+    // again for the ML data of every file Ente holds none for.
+    //
+    // A saved session is read back by `loadSession`, its `fetch` a fake of the
+    // Ente HTTP API serving one album with one photo, encrypted as the server
+    // serves them. The fake holds the photo's download open while the clock
+    // moves on by two hours, then serves it. Only `setTimeout` and
+    // `clearTimeout` are faked: the library's refresh timer runs on them.
+    it("asks the server for changes only as it starts, however long it runs", async () => {
+        const masterKey = new Uint8Array(32).fill(1);
+        const albumKey = new Uint8Array(32).fill(2);
+        const photoKey = new Uint8Array(32).fill(3);
+        saveSession(join(root, "session"), {
+            email: "cli@example.com",
+            userID: USER_ID,
+            token: "token",
+            masterKey: toBase64(masterKey),
+            secretKey: toBase64(new Uint8Array(32)),
+            publicKey: toBase64(new Uint8Array(32)),
+        });
+        // A secretbox as the server sends one: ciphertext and nonce, base64.
+        const box = (plaintext: Uint8Array, key: Uint8Array) => {
+            const nonce = sodium.randombytes_buf(
+                sodium.crypto_secretbox_NONCEBYTES,
+            );
+            return {
+                ciphertext: toBase64(
+                    sodium.crypto_secretbox_easy(plaintext, nonce, key),
+                ),
+                nonce: toBase64(nonce),
+            };
+        };
+        const albumKeyBox = box(albumKey, masterKey);
+        const albumName = box(new TextEncoder().encode("Vacation"), albumKey);
+        const photoKeyBox = box(photoKey, albumKey);
+        const metadata = encryptBlob(
+            new TextEncoder().encode(
+                JSON.stringify({
+                    title: "beach.jpg",
+                    fileType: 0,
+                    creationTime: 1_700_000_000_000_000,
+                    modificationTime: 1_700_000_000_000_000,
+                }),
+            ),
+            photoKey,
+        );
+        const content = encryptBlob(
+            new TextEncoder().encode("the photo's bytes"),
+            photoKey,
+        );
+        const album = {
+            id: 1,
+            owner: { id: USER_ID },
+            encryptedKey: albumKeyBox.ciphertext,
+            keyDecryptionNonce: albumKeyBox.nonce,
+            encryptedName: albumName.ciphertext,
+            nameDecryptionNonce: albumName.nonce,
+            type: "album",
+            updationTime: 1,
+        };
+        const photo = {
+            id: 100,
+            collectionID: 1,
+            ownerID: USER_ID,
+            encryptedKey: photoKeyBox.ciphertext,
+            keyDecryptionNonce: photoKeyBox.nonce,
+            metadata: {
+                encryptedData: toBase64(metadata.ciphertext),
+                decryptionHeader: toBase64(metadata.header),
+            },
+            file: { decryptionHeader: toBase64(content.header) },
+            // The backup fetches no thumbnail.
+            thumbnail: { decryptionHeader: "" },
+            updationTime: 1,
+        };
+
+        // Each refresh starts with `collectionsSince`, which sends one
+        // `/collections/v2` request.
+        let refreshes = 0;
+        let downloadRequested!: () => void;
+        const requested = new Promise<void>((resolve) => {
+            downloadRequested = resolve;
+        });
+        let releaseDownload!: () => void;
+        const released = new Promise<void>((resolve) => {
+            releaseDownload = resolve;
+        });
+        const json = (body: unknown): Response =>
+            new Response(JSON.stringify(body), {
+                headers: { "content-type": "application/json" },
+            });
+        const fetch = async (url: string | URL): Promise<Response> => {
+            const { hostname, pathname } = new URL(String(url));
+            if (hostname === "files.ente.io") {
+                downloadRequested();
+                await released;
+                return new Response(content.ciphertext);
+            }
+            if (pathname === "/collections/v2") {
+                refreshes++;
+                return json({ collections: [album] });
+            }
+            if (pathname === "/collections/v2/diff") {
+                return json({ diff: [photo], hasMore: false });
+            }
+            // Ente holds no ML data for the photo.
+            if (pathname === "/files/data/fetch") return json({ data: [] });
+            return new Response("not found", { status: 404 });
+        };
+        const ctx = {
+            ...context(),
+            // The download's idle deadline is set past the two hours, or quak
+            // would give up the held download as stalled.
+            loadSession: (path: string) =>
+                loadSession(path, {
+                    fetch: fetch as typeof globalThis.fetch,
+                    downloadTimeoutMs: 3 * 3_600_000,
+                }),
+        };
+
+        vi.useFakeTimers({ toFake: ["setTimeout", "clearTimeout"] });
+        try {
+            const backup = backupCommand(ctx, join(root, "backup"), {});
+            await requested;
+            vi.advanceTimersByTime(2 * 3_600_000);
+            releaseDownload();
+            expect(await backup).toBe(0);
+        } finally {
+            vi.useRealTimers();
+        }
+
+        // Two refreshes, both before the download: the library opens onto the
+        // empty cache with one, and the backup waits for the other before it
+        // lists its files.
+        expect(refreshes).toBe(2);
+    });
 });
 
 describe("helper list-missing-thumbnails", () => {