ML data that does not decrypt is recorded with its reason (closes #198)

`fetchMLDataBatch` dropped an entry that did not decrypt, gunzip or parse,
so the file looked like one with no ML data and the run exited 0. It now
returns the reason beside the payloads, also for ML data that is not a
JSON object. The library gives the reasons from its last ML data fetch
that succeeded in `status().mlDataErrors` and the `fetchMLData` "done"
event; a fetch that fails leaves them as they were. `quak backup` writes
the reason as `mlDataError` for a file with no ML data cached and records
the file in `failures.json`. `backup-metadata` writes `mlDataError` for it
and exits 1; `runMetadataBackup` returns `filesWithMLDataError`.

Judgement call: a file whose ML data is cached keeps it in its JSON when a
newer copy does not decode, as when the fetch fails.

Model: opus-5-5

README.md

@@ -159,11 +159,10 @@ After a `1`, the next run fetches each missing original again, fetches the ML
 data that is not cached, and rebuilds the album links. An album quak could not
 decrypt, or a file in `failures.json` because quak could not decrypt it, keeps
 the exit code at `1` until the server sends a copy that decrypts, or deletes it
-(see "Backup layout"). An original that a `--verify` run could not read, or
+(see "Backup layout"). An original that a `--verify` run could not read, or put
-could not replace with a download that matches, stays at its save path as it
+back with bytes that still do not match, stays at its save path. Only a later
-was. Only a later `--verify` run checks it again: a run without `--verify`
+`--verify` run checks it again: a run without `--verify` leaves it as it is and
-leaves it as it is and takes the file out of `failures.json`, so that run can
+takes the file out of `failures.json`, so that run can exit 0.
-exit 0.
 
 ## Examples
 
@@ -693,8 +692,8 @@ reads no tag from is recorded, base64, as `exifRaw`, with the reason in
 and `helper fix-missing-thumbnails` take `--json` for machine-readable output.
 
 `backup --verify` also hashes the originals already in the backup and replaces
-any that do not match the content hash Ente records; one it cannot replace stays
+any that do not match the content hash Ente records; one it cannot replace goes
-as it was and goes into `failures.json` (see "Backup layout").
+into `failures.json` (see "Backup layout").
 
 `backup-metadata` fetches ML data in requests of up to 200 files. When a request
 fails, the error is logged, each of its files is written with the reason in an
@@ -888,41 +887,33 @@ original already at its save path the way a download is checked (see "On-disk
 cache layout" below): its bytes, read in chunks, or a live photo's image and
 video, joined as `<imageHash>:<videoHash>`. An original that matches the content
 hash its metadata records is left as it is. One that does not is logged on one
-line naming the file, and replaced once a matching copy is downloaded, in the
+line naming the file, deleted (a live photo's image and video both), and put
-same run. The copy is downloaded even when the cache holds the original, because
+back in the same run like a missing one: downloaded, or copied from the cache if
-a copy from the cache is not checked as a download is. It is written to a
+the cache holds it. What is put back is hashed too, because a copy from the
-temporary file beside the original, a live photo's image and video each to its
+cache is not checked as a download is. If it still does not match, it stays at
-own, hashed the same way, and renamed over the original only when it matches; a
+its save path and the file goes into `failures.json`, as it does when the
-live photo's image and video are both hashed before either is renamed. Until
+download fails. A file whose metadata records no hash is left as it is and
-then the original stays as it was: when the download fails, or what it brings
+counted as unchecked. A stored original that cannot be read is left as it is and
-does not match either, the temporary files are deleted, the original keeps its
+counts as failed. The summary and `--json` add the counts `verified`,
-bytes and its album links, and the file goes into `failures.json`. A run that
+`mismatched` and `unchecked`, all of originals that were already stored; one
-stops between renaming a live photo's new image and its new video leaves the new
+first downloaded in this run is in none of them. A mismatch that was put back
-image beside the old video, which a later `--verify` run replaces if the video
+with matching bytes does not make the exit code non-zero. Without `--verify`
-was the part that did not match. A file whose metadata records no hash is left
+nothing is hashed, the summary is unchanged, and the three counts are 0 in
-as it is and counted as unchecked. A stored original that cannot be read is left
+`--json`.
-as it is and counts as failed. The summary and `--json` add the counts
-`verified`, `mismatched` and `unchecked`, all of originals that were already
-stored; one first downloaded in this run is in none of them. A mismatch that was
-replaced with matching bytes does not make the exit code non-zero. Without
-`--verify` nothing is hashed, the summary is unchanged, and the three counts are
-0 in `--json`.
 
 Each original is written to a temporary file in the same directory, synced to
 disk, and renamed into place, so an original is either complete or absent, even
 after a power cut. A downloaded original's temporary file is named
 `.quak-<pid>-<random>.tmp`, one copied from the cache
-`.quak-backup-YYYY-MM-DD.<fileID>.<ext>-<pid>-<random>.tmp`. A copy that
+`.quak-backup-YYYY-MM-DD.<fileID>.<ext>-<pid>-<random>.tmp`. A run that is
-`--verify` downloads to replace an original is written to such a
+killed can leave one of these temporary files behind; the next backup deletes
-`.quak-<pid>-<random>.tmp` too, a live photo's image and video to
+those whose process is no longer running. The content cache uses the same
-`.quak-<pid>-<random>.<ext>`, each with its own extension. A run that is killed
+scheme, and opening a library deletes the temporary files in the cache whose
-can leave one of these temporary files behind; the next backup deletes those
+process is no longer running, so a download another process has in progress in
-whose process is no longer running. The content cache uses the same scheme, and
+the same cache is left alone. The rename replaces whatever was at the
-opening a library deletes the temporary files in the cache whose process is no
+destination rather than writing through it: a symlink there is replaced, not
-longer running, so a download another process has in progress in the same cache
+followed, and the new file has the temporary file's permissions, not those of
-is left alone. The rename replaces whatever was at the destination rather than
+the file it replaced.
-writing through it: a symlink there is replaced, not followed, and the new file
-has the temporary file's permissions, not those of the file it replaced.
 
 ## TODO
 

TODO.md

@@ -17,9 +17,10 @@ pre-1.0
 
 # Next Step
 
-One bug is open: https://git.eeqj.de/sneak/quak/issues/205. The check of quak
+Two bugs are open: https://git.eeqj.de/sneak/quak/issues/199 and
-against a live Ente account, https://git.eeqj.de/sneak/quak/issues/187, needs an
+https://git.eeqj.de/sneak/quak/issues/205. The check of quak against a live Ente
-account only sneak has, so it waits on him.
+account, https://git.eeqj.de/sneak/quak/issues/187, needs an account only sneak
+has, so it waits on him.
 
 Tagging and releases are decided by sneak alone, and happen only when he
 declares one.
@@ -39,16 +40,6 @@ declares one.
   too. Both exit 1. Tests serve ML data encrypted under a key that is not the
   file's.
 
-- 2026-10-16: With `--verify`, an original whose hash does not match is no
-  longer removed before its replacement is downloaded (issue 199).
-  `replaceOriginal` in `src/library/content.ts` downloads the replacement to a
-  temporary file beside it, a live photo's image and video each to its own,
-  hashes it and renames it over the original only when it matches. When the
-  download fails or does not match either, the original keeps its bytes and
-  links, and the file goes into `failures.json`. The replacement is always
-  downloaded, through the new `fetchOriginal` of the content cache, never copied
-  from the cache.
-
 - 2026-10-16: The `~/bin/quak` that `make install` builds retries a refused
   connection and a name that does not resolve, and the backup records either as
   transient (issue 206). Bun's `fetch` reports them with codes of its own,

src/backup.ts

@@ -41,9 +41,8 @@
 //
 // With `verify`, each original already at its save path is hashed as the
 // download check hashes it, and one that does not match the content hash its
-// metadata records is replaced once a matching copy is downloaded, in the same
+// metadata records is removed and fetched again in the same run. What is put
-// run. Until then it stays as it is: a download that fails, or that does not
+// back is hashed too, and recorded as failed if it still does not match.
-// match either, leaves it in place and is recorded as failed.
 //
 // Resilience (issue #8): no per-file condition aborts the run. A failed
 // download, a failed symlink, or ML data missing because the ML data fetch
@@ -62,6 +61,7 @@
 // code.
 
 import {
+    createReadStream,
     lstatSync,
     mkdirSync,
     readdirSync,
@@ -77,6 +77,12 @@ import { readFile } from "node:fs/promises";
 import { dirname, extname, join, relative, resolve } from "node:path";
 import lockfile from "proper-lockfile";
 
+import {
+    chunkHashFinal,
+    chunkHashInit,
+    chunkHashUpdate,
+    init,
+} from "./crypto/index.js";
 import { removeLeftoverTempFiles } from "./download/index.js";
 import { describeError } from "./errors.js";
 import {
@@ -88,10 +94,8 @@ import {
 import {
     copyAtomic,
     placeOriginal,
-    replaceOriginal,
     savePath,
     storedAtSavePath,
-    storedHash,
 } from "./library/content.js";
 import { representative } from "./library/records.js";
 import type { Undecryptable } from "./library/store.js";
@@ -148,9 +152,9 @@ export interface BackupResult {
     // Originals already at their save path and left untouched.
     skipped: number;
     // With `verify`, the originals already at their save path whose hash
-    // matched, those whose hash did not (each replaced once a matching copy is
+    // matched, those whose hash did not (each removed and fetched again), and
-    // downloaded), and those whose metadata records no hash (left as they
+    // those whose metadata records no hash (left as they are). All three are
-    // are). All three are zero without `verify`.
+    // zero without `verify`.
     verified: number;
     mismatched: number;
     unchecked: number;
@@ -188,15 +192,6 @@ export interface BackupLibrary {
         fileID: number,
         destination: string,
     ): Promise<{ path: string; videoPath?: string }>;
-    // Fetch an original's bytes to `destination` through the content pool,
-    // a live photo as its image and its video beside it, even when the cache
-    // or the library's save path already holds it, and return where they
-    // landed. With `verify`, an original whose hash does not match is replaced
-    // with what this fetches.
-    fetchOriginal(
-        fileID: number,
-        destination: string,
-    ): Promise<{ path: string; videoPath?: string }>;
     thumbnail(fileID: number): Promise<{ path: string }>;
     // How many originals the backup works on at once: the limit of the
     // library's content pool.
@@ -454,6 +449,26 @@ const saveLedger = (path: string, ledger: Map<number, FailureEntry>): void => {
     );
 };
 
+// The content hash of the original stored at `stored`, computed as the download
+// check computes it: over each file's bytes, read in chunks, and for a live
+// photo `<imageHash>:<videoHash>`.
+const storedHash = async (stored: {
+    path: string;
+    videoPath?: string;
+}): Promise<string> => {
+    await init();
+    const hashFile = async (path: string): Promise<string> => {
+        const state = chunkHashInit();
+        for await (const chunk of createReadStream(path)) {
+            chunkHashUpdate(state, chunk as Buffer);
+        }
+        return chunkHashFinal(state);
+    };
+    const hash = await hashFile(stored.path);
+    if (stored.videoPath === undefined) return hash;
+    return `${hash}:${await hashFile(stored.videoPath)}`;
+};
+
 // A file's EXIF, XMP and dimensions as its JSON holds them: what
 // `extractImageMetadata` found in its original, or why the original could not
 // be read.
@@ -675,13 +690,11 @@ const runLockedBackup = async (
     // through the content cache/pools, as `Photo.download()` does, and fetch
     // the optional thumbnails; a present file is left as is. With `verify`, a
     // present original is hashed first, and one that does not match the hash
-    // its metadata records is downloaded again and replaced by
+    // its metadata records is removed and fetched like a missing one. One
-    // `replaceOriginal`, which leaves it as it was when that download fails
+    // that cannot be read is recorded as failed and left where it is.
-    // or does not match either. One that cannot be read is recorded as failed
+    // `storeOriginal` does this for one original, and records its failure.
-    // and left where it is. `storeOriginal` does this for one original, and
-    // records its failure.
     const storeOriginal = async (file: EnteFile): Promise<void> => {
-        const stored = storedAtSavePath(downloadDirectory, file);
+        let stored = storedAtSavePath(downloadDirectory, file);
         let mismatch = false;
         if (stored !== undefined && verify) {
             try {
@@ -695,6 +708,11 @@ const runLockedBackup = async (
                     );
                     mismatched++;
                     mismatch = true;
+                    rmSync(stored.path);
+                    if (stored.videoPath !== undefined) {
+                        rmSync(stored.videoPath);
+                    }
+                    stored = undefined;
                 }
             } catch (err) {
                 log(
@@ -709,25 +727,29 @@ const runLockedBackup = async (
                 return;
             }
         }
-        if (stored !== undefined && !mismatch) {
+        if (stored !== undefined) {
             skipped++;
             return;
         }
         try {
             log(`Fetching original ${file.metadata.title} (${file.id})...`);
-            if (mismatch) {
+            // A fetched original is written straight to its save path (a
-                await replaceOriginal(downloadDirectory, file, (dest) =>
+            // live photo beside it); only one that was already cached
-                    lib.fetchOriginal(file.id, dest),
+            // elsewhere is copied.
-                );
+            const placed = await placeOriginal(
-            } else {
+                downloadDirectory,
-                // A fetched original is written straight to its save path (a
+                file,
-                // live photo beside it); only one that was already cached
+                (dest) => lib.original(file.id, dest),
-                // elsewhere is copied.
+            );
-                await placeOriginal(downloadDirectory, file, (dest) =>
+            storedThisRun.add(file.id);
-                    lib.original(file.id, dest),
+            // A copy from the cache is not checked as a download is and can
+            // hold the same bad bytes, so what is put back after a mismatch
+            // is hashed too. A bad copy stays where it is and the file fails.
+            if (mismatch && (await storedHash(placed)) !== file.metadata.hash) {
+                throw new Error(
+                    "the original put back does not match its content hash either",
                 );
             }
-            storedThisRun.add(file.id);
             downloaded++;
         } catch (err) {
             log(

src/download/index.ts

@@ -199,13 +199,11 @@ const isRunning = (pid: number): boolean => {
 };
 
 // Delete the temp files a killed process left in `dir`: the writer's
-// `.quak-<pid>-<random>.tmp`, the backup copy's
+// `.quak-<pid>-<random>.tmp` and the backup copy's
-// `.quak-backup-<name>-<pid>-<random>.tmp`, and the image and video of a live
+// `.quak-backup-<name>-<pid>-<random>.tmp`. Only files whose process is no
-// photo downloaded to replace a stored one, `.quak-<pid>-<random>.<ext>` (see
+// longer running are removed, so another process writing into the same
-// `replaceOriginal`). Only files whose process is no longer running are
+// directory keeps its own. A reused process ID can only keep a leftover a while
-// removed, so another process writing into the same directory keeps its own. A
+// longer, never remove a live one.
-// reused process ID can only keep a leftover a while longer, never remove a
-// live one.
 export const removeLeftoverTempFiles = (dir: string): void => {
     let names: string[];
     try {
@@ -214,9 +212,7 @@ export const removeLeftoverTempFiles = (dir: string): void => {
         return;
     }
     for (const name of names) {
-        const match = /^\.quak-(?:.*-)?(\d+)-[0-9a-z]*\.[0-9A-Za-z]+$/.exec(
+        const match = /^\.quak-(?:.*-)?(\d+)-[0-9a-z]*\.tmp$/.exec(name);
-            name,
-        );
         if (match && !isRunning(Number(match[1]))) {
             rmSync(join(dir, name), { force: true });
         }

src/library/content.ts

@@ -13,8 +13,6 @@
 // originals, the thumbnail pool for thumbnails. The pool limits concurrency,
 // orders on-demand work ahead of background, and dedups by key so a fileID
 // requested twice while the first is still in flight downloads once.
-// `fetchOriginal` passes no key, so it is not shared with a fetch of the same
-// file already in flight.
 //
 // Integrity. The reused streaming decrypt is the enforced guarantee: every
 // chunk is authenticated and the writer renames the file into place only once
@@ -29,10 +27,9 @@
 // It also names each original's save path under the download directory
 // (`savePath`), where `Photo.download()` and `lib.backup()` put it. A copy in
 // the cache does not count as saved there, but is copied there rather than
-// fetched again. An original stored there whose bytes do not match its content
+// fetched again.
-// hash is replaced only by a download that does (`replaceOriginal`).
 
-import { createReadStream, existsSync, readFileSync, statSync } from "node:fs";
+import { existsSync, readFileSync, statSync } from "node:fs";
 import {
     chmod,
     copyFile,
@@ -47,12 +44,6 @@ import {
 import { basename, dirname, extname, join } from "node:path";
 
 import type { ApiClient } from "../api/client.js";
-import {
-    chunkHashFinal,
-    chunkHashInit,
-    chunkHashUpdate,
-    init,
-} from "../crypto/index.js";
 import {
     downloadFile,
     downloadThumbnail,
@@ -358,26 +349,6 @@ export const storedAtSavePath = (
     return storedOriginal(dirname(path), basename(path, extname(path)), file);
 };
 
-// The content hash of the original stored at `stored`, computed as the download
-// check computes it: over each file's bytes, read in chunks, and for a live
-// photo `<imageHash>:<videoHash>`.
-export const storedHash = async (stored: {
-    path: string;
-    videoPath?: string;
-}): Promise<string> => {
-    await init();
-    const hashFile = async (path: string): Promise<string> => {
-        const state = chunkHashInit();
-        for await (const chunk of createReadStream(path)) {
-            chunkHashUpdate(state, chunk as Buffer);
-        }
-        return chunkHashFinal(state);
-    };
-    const hash = await hashFile(stored.path);
-    if (stored.videoPath === undefined) return hash;
-    return `${hash}:${await hashFile(stored.videoPath)}`;
-};
-
 // Copy bytes into `dest` via a temp file in the same directory plus rename, so
 // `dest` appears only once it is whole ("present means complete"). As in the
 // download writer, the temp file is fsynced before the rename and the directory
@@ -434,62 +405,6 @@ export const placeOriginal = async (
     return { path, videoPath };
 };
 
-// Replace the original of `file` stored at its save path under `root` with a
-// new copy, keeping the stored one until the copy is complete and its hash,
-// computed as `storedHash` computes it, is the content hash the file's metadata
-// records. `get` is given a temporary file beside the save path and writes the
-// copy there, a live photo as its image and its video beside that file, each
-// with its own extension. Only a copy that matches is renamed over the stored
-// one, and a live photo's image and video are both hashed before either is
-// renamed. The image is renamed first: should the run stop, or the video's
-// rename fail, before the video is renamed, the new image is left beside the
-// old video, and a later backup with `verify` replaces the video if the video
-// was the part that did not match. When `get` fails or the copy does not match,
-// the temporary files are removed and the stored original stays as it was.
-export const replaceOriginal = async (
-    root: string,
-    file: EnteFile,
-    get: (dest: string) => Promise<{ path: string; videoPath?: string }>,
-): Promise<{ path: string; videoPath?: string }> => {
-    const dest = savePath(root, file);
-    const dir = dirname(dest);
-    // Named as the download writer names its temporary files; a live photo's
-    // image and video get this name with their own extensions. The next
-    // backup removes any that a killed run leaves (`removeLeftoverTempFiles`).
-    const tmp = join(
-        dir,
-        `.quak-${process.pid}-${Math.random().toString(36).slice(2)}.tmp`,
-    );
-    let got: { path: string; videoPath?: string } | undefined;
-    try {
-        got = await get(tmp);
-        if ((await storedHash(got)) !== file.metadata.hash) {
-            throw new Error(
-                "the downloaded original does not match its content hash either",
-            );
-        }
-        if (got.videoPath === undefined) {
-            await rename(got.path, dest);
-            await fsyncPath(dir);
-            return { path: dest };
-        }
-        const path = withExtension(dest, extname(got.path));
-        const videoPath = withExtension(dest, extname(got.videoPath));
-        await rename(got.path, path);
-        await rename(got.videoPath, videoPath);
-        const name = basename(dest, extname(dest));
-        await writeLivePhotoJSON(dir, name, { path, videoPath });
-        return { path, videoPath };
-    } finally {
-        // Whatever was not renamed into place. A failure to remove it must
-        // not replace the error that explains what went wrong.
-        for (const path of [tmp, got?.path, got?.videoPath]) {
-            if (path === undefined) continue;
-            await rm(path, { force: true }).catch(() => undefined);
-        }
-    }
-};
-
 export class ContentCache implements PhotoContent, ThumbnailsAPI {
     private readonly pools: RequestPools;
     private readonly source: ContentSource;
@@ -628,35 +543,6 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
         };
     }
 
-    // Fetch an original through the content pool to `destination`, a live
-    // photo as its image and its video beside it, and return where it landed.
-    // Unlike `backupOriginal`, it fetches even when the cache or the save path
-    // already holds the original, and it records nothing: what it writes is
-    // the caller's. It is not shared with a fetch of the same file already
-    // under way, which writes somewhere else.
-    async fetchOriginal(
-        fileID: number,
-        destination: string,
-    ): Promise<{ path: string; videoPath?: string }> {
-        const file = this.getFile(fileID);
-        if (!file) throw new Error(`content cache: unknown file ${fileID}`);
-        return this.pools.content.run(
-            async () => {
-                const fetched = await this.fetchInto(
-                    file,
-                    destination,
-                    "original",
-                    undefined,
-                );
-                for (const path of [fetched.path, fetched.videoPath]) {
-                    if (path !== undefined) await chmod(path, FILE_MODE);
-                }
-                return fetched;
-            },
-            { priority: "on-demand" },
-        );
-    }
-
     async ensure(args: EnsureOptions): Promise<EnsureResult[]> {
         return this.ensureThumbnails(args);
     }

src/library/index.ts

@@ -626,8 +626,6 @@ export class Library {
                 undecryptable: () => this.store.listUndecryptable(),
                 original: (fileID, destination) =>
                     cache!.backupOriginal(fileID, destination),
-                fetchOriginal: (fileID, destination) =>
-                    cache!.fetchOriginal(fileID, destination),
                 thumbnail: (fileID) => cache!.thumbnail(fileID),
                 contentConcurrency: this.pools.content.concurrency,
                 fetchMLData: () => this.fetchMLDataNow(),

test/cli/backup.test.ts

@@ -191,12 +191,9 @@ class HostileClient extends MockClient {
 }
 
 // A content source that writes byte buffers of the expected length and can be
-// told to fail one fileID's original, as a server error or as a 404, or to
+// told to fail one fileID's original, to exercise per-file resilience.
-// write other bytes for it, to exercise per-file resilience.
 interface StubSource extends ContentSource {
     failID?: number;
-    notFoundID?: number;
-    otherBytesID?: number;
     failThumbID?: number;
     originalCalls: number;
 }
@@ -207,10 +204,8 @@ const stubSource = (): StubSource => {
         original: async ({ file: f, destination }) => {
             s.originalCalls++;
             if (s.failID === f.id) throw new Error("HTTP 500 from server");
-            if (s.notFoundID === f.id) throw new Error("HTTP 404 from server");
             const size = SIZE_BY_ID[f.id] ?? 10;
-            const fill = s.otherBytesID === f.id ? 2 : 0;
+            writeFileSync(destination, Buffer.alloc(size));
-            writeFileSync(destination, Buffer.alloc(size, fill));
             return { bytesWritten: size };
         },
         thumbnail: async ({ file: f, destination }) => {
@@ -701,26 +696,17 @@ describe("lib.backup", () => {
         // A child that has already exited: its process ID is not running.
         const exitedPID = spawnSync(process.execPath, ["-e", ""]).pid;
         const leftover = `.quak-backup-2026-03-01.100.jpg-${exitedPID}-abc123.tmp`;
-        // A live photo's image and video downloaded to replace a stored one,
-        // before they were renamed into place.
-        const replacement = [
-            `.quak-${exitedPID}-abc789.heic`,
-            `.quak-${exitedPID}-abc789.mov`,
-        ];
         // This test's own process stands in for a backup running at the same
         // time.
         const inProgress = `.quak-backup-2026-03-01.101.jpg-${process.pid}-def456.tmp`;
-        for (const name of [leftover, ...replacement, inProgress]) {
+        writeFileSync(join(day, leftover), "partial");
-            writeFileSync(join(day, name), "partial");
+        writeFileSync(join(day, inProgress), "partial");
-        }
         const lib = await openLibrary(stubSource());
 
         await lib.backup({ downloadDirectory: outDir });
 
         const names = readdirSync(day);
         expect(names).not.toContain(leftover);
-        expect(names).not.toContain(replacement[0]);
-        expect(names).not.toContain(replacement[1]);
         expect(names).toContain(inProgress);
         lib.close();
     });
@@ -1309,8 +1295,7 @@ describe("image metadata in each file's JSON", () => {
 });
 
 // With `verify`, each original already stored is hashed, and one that does not
-// match the content hash its metadata records is downloaded again, and replaced
+// match the content hash its metadata records is downloaded again.
-// only by a download that matches.
 describe("backup with verify", () => {
     // MockClient's files, each recording the hash of what `stubSource` writes
     // for it, except diagram.png (200), which records none.
@@ -1353,12 +1338,6 @@ describe("backup with verify", () => {
     const good = Buffer.alloc(SIZE_BY_ID[100]!);
     const corrupt = Buffer.alloc(SIZE_BY_ID[100]!, 1);
 
-    // The temporary files left in the date folder of the backup in `outDir`.
-    const tempFiles = (outDir: string): string[] =>
-        readdirSync(join(outDir, DAY)).filter((name) =>
-            name.startsWith(".quak-"),
-        );
-
     it("leaves an original that matches its hash, and one with no hash, as they are", async () => {
         const { lib, source, outDir } = await backedUp();
         const calls = source.originalCalls;
@@ -1403,16 +1382,13 @@ describe("backup with verify", () => {
         expect(log.filter((msg) => msg.startsWith("MISMATCH"))).toEqual([
             "MISMATCH original beach.jpg (100): its bytes do not match its content hash",
         ]);
-        expect(tempFiles(outDir)).toEqual([]);
         await lib.close();
     });
 
-    // A copy whose hash does not match is still mostly the photo, so the
+    it("records a failed download in failures.json, with the original removed", async () => {
-    // backup keeps it until it holds a better one.
-    it("keeps an original that does not match its hash when its download answers 404", async () => {
         const { lib, source, outDir } = await backedUp();
         writeFileSync(saved(outDir, "100.jpg"), corrupt);
-        source.notFoundID = 100;
+        source.failID = 100;
 
         const result = await lib.backup({
             downloadDirectory: outDir,
@@ -1425,18 +1401,18 @@ describe("backup with verify", () => {
             failed: 1,
         });
         expect(Object.keys(readLedger(outDir).files)).toEqual(["100"]);
-        expect(readFileSync(saved(outDir, "100.jpg"))).toEqual(corrupt);
+        expect(existsSync(saved(outDir, "100.jpg"))).toBe(false);
-        expect(
-            readlinkSync(join(outDir, "collections", "Vacation", "beach.jpg")),
-        ).toBe(linkTo("100.jpg"));
-        expect(tempFiles(outDir)).toEqual([]);
         await lib.close();
     });
 
-    it("keeps an original that does not match its hash when its download does not match either", async () => {
+    it("records in failures.json an original the cache puts back with the same bad bytes", async () => {
-        const { lib, source, outDir } = await backedUp();
+        const lib = await openLibrary(stubSource(), new HashedClient());
-        writeFileSync(saved(outDir, "100.jpg"), corrupt);
+        const outDir = join(root, "backup");
-        source.otherBytesID = 100;
+        // The cache holds a bad copy, and a backup copies an original the
+        // cache holds to its save path.
+        const cached = await lib.photos.byID({ fileID: 100 })!.original();
+        writeFileSync(cached.path, corrupt);
+        await lib.backup({ downloadDirectory: outDir });
 
         const result = await lib.backup({
             downloadDirectory: outDir,
@@ -1449,39 +1425,10 @@ describe("backup with verify", () => {
             failed: 1,
         });
         expect(result.errors.map((e) => e.error)).toEqual([
-            "the downloaded original does not match its content hash either",
+            "the original put back does not match its content hash either",
         ]);
         expect(Object.keys(readLedger(outDir).files)).toEqual(["100"]);
         expect(readFileSync(saved(outDir, "100.jpg"))).toEqual(corrupt);
-        expect(tempFiles(outDir)).toEqual([]);
-        await lib.close();
-    });
-
-    // The cache can hold the same bad bytes, as a copy from it is not checked
-    // as a download is, so the replacement is always downloaded.
-    it("downloads the replacement even when the cache holds the original", async () => {
-        const source = stubSource();
-        const lib = await openLibrary(source, new HashedClient());
-        const outDir = join(root, "backup");
-        // The cache holds a bad copy, and a backup copies an original the
-        // cache holds to its save path.
-        const cached = await lib.photos.byID({ fileID: 100 })!.original();
-        writeFileSync(cached.path, corrupt);
-        await lib.backup({ downloadDirectory: outDir });
-        const calls = source.originalCalls;
-
-        const result = await lib.backup({
-            downloadDirectory: outDir,
-            verify: true,
-        });
-
-        expect(result).toMatchObject({
-            downloaded: 1,
-            mismatched: 1,
-            failed: 0,
-        });
-        expect(source.originalCalls).toBe(calls + 1);
-        expect(readFileSync(saved(outDir, "100.jpg"))).toEqual(good);
         await lib.close();
     });
 
@@ -1565,9 +1512,6 @@ describe("backup album folders", () => {
             writeFileSync(path, `original ${fileID}`);
             return { path };
         },
-        fetchOriginal: async () => {
-            throw new Error("no verify in this stand-in");
-        },
         thumbnail: async () => {
             throw new Error("no thumbnails in this stand-in");
         },
@@ -2302,12 +2246,11 @@ describe("backup of live photos", () => {
             Buffer.from(IMAGE),
         );
         expect(readFileSync(video)).toEqual(Buffer.from(VIDEO));
-        expect(readdirSync(join(outDir, DAY)).sort()).toEqual(stored);
         expect(tree(outDir)).toEqual(linked);
         await lib.close();
     });
 
-    it("keeps both files of a live photo that does not match its hash when downloading it again fails", async () => {
+    it("removes both files of a live photo that does not match its hash when downloading it again fails", async () => {
         const { file: live, body } = await asLivePhoto(
             file(500, 10, "IMG_0500.HEIC"),
         );
@@ -2325,14 +2268,8 @@ describe("backup of live photos", () => {
 
         expect(result).toMatchObject({ mismatched: 1, failed: 1 });
         expect(Object.keys(readLedger(outDir).files)).toEqual(["500"]);
-        expect(readFileSync(saved(outDir, "500.heic"))).toEqual(
+        expect(existsSync(saved(outDir, "500.heic"))).toBe(false);
-            Buffer.from(IMAGE),
+        expect(existsSync(saved(outDir, "500.mov"))).toBe(false);
-        );
-        expect(readFileSync(saved(outDir, "500.mov"), "utf-8")).toBe(
-            "another few seconds of video",
-        );
-        expect(readdirSync(join(outDir, DAY)).sort()).toEqual(stored);
-        expect(tree(outDir)).toEqual(linked);
         await lib.close();
     });