Photo implements one method per PhotoExif field

Photo now implements a mapped type with one method per PhotoExif field,
each taking exif()'s options and giving that field's type, so the
build's type check fails when PhotoExif has a field Photo has no method
for, whatever the test fixtures hold. The test comment and TODO.md say
so.

Model: opus-5-5

README.md

@@ -528,25 +528,36 @@ the smallest does not.
 
 ```
 <dir>/
-    originals/
-        <fileID>.<ext>          actual file content (one per unique file,
-                                two for a live photo: see below)
-        <fileID>.json           the file's basic metadata fields quak
+    YYYY/YYYY-MM/YYYY-MM-DD/
+        YYYY-MM-DD.<fileID>.<ext>   actual file content, at its save path (one
+                                    per unique file, two for a live photo: see
+                                    below)
+        YYYY-MM-DD.<fileID>.json    the file's basic metadata fields quak
                                     keeps, and its private and public magic
                                     metadata
-        <fileID>.livephoto.json which of a live photo's two files is which
+        YYYY-MM-DD.<fileID>.livephoto.json
+                                    which of a live photo's two files is which
     collections/
         <name>/
-            <title> -> ../../originals/<fileID>.<ext>   (symlink)
+            <title> -> ../../YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID>.<ext>
+                                    (symlink)
         <name>.json                 collection metadata + file list
     failures.json                   files that failed and have not yet succeeded
 ```
 
+Each original is saved at its save path, the same path `photo.savePath` gives
+and `photo.download()` writes (see Read surface below). The date is the photo's
+`takenAt` (the date set in Ente if it was edited, else its creation time) in the
+time zone of the machine running quak. The extension is the one in the file's
+name as uploaded, case kept, or `.bin` when it has none or it holds anything but
+letters and digits. When the date or the time zone changes, the next run saves
+the original at its new path and leaves the old copy where it is.
+
 `failures.json` records each failed file with the kind of failure, how many
 times it has been tried and when it was last tried. A file leaves it once it
 succeeds, or once it is no longer in the library or in the backup's scope. The
 library's `lib.backup({ includeThumbnails: true })` also writes
-`thumbnails/<fileID>.jpg` beside `originals/`; `quak backup` does not.
+`thumbnails/<fileID>.jpg` beside `collections/`; `quak backup` does not.
 
 A collection's directory and JSON are named after the collection, and a symlink
 after the file's title, both with unsafe characters replaced. When two
@@ -558,22 +569,21 @@ name stays the same from run to run until such a clash appears or goes away.
 
 A live photo, which Ente stores as one ZIP of its image and its video, is stored
 as those two files, which a photo viewer can open: each is
-`originals/<fileID>.<ext>` with the extension it has inside the ZIP (for example
-`12345.heic` and `12345.mov`), and `<fileID>.livephoto.json` names the two. The
-live photo counts as stored only when both files are present and not empty. Its
-album folder links both, each named after the title with that file's extension
-(`IMG_0001.heic` and `IMG_0001.mov`). A live photo that an earlier version of
-quak stored as the ZIP, under the image's name, is replaced by its two files on
-the next run, and the ZIP and its link are removed.
+`YYYY-MM-DD.<fileID>.<ext>` with the extension it has inside the ZIP (for
+example `2026-03-01.12345.heic` and `2026-03-01.12345.mov`), and
+`YYYY-MM-DD.<fileID>.livephoto.json` names the two. The live photo counts as
+stored only when both files are present and not empty. Its album folder links
+both, each named after the title with that file's extension (`IMG_0001.heic` and
+`IMG_0001.mov`).
 
-Each run removes the symlinks into `originals/` that no longer belong in their
-collection's directory, and the directories (and JSON) of collections that were
-deleted or renamed. Nothing else in `collections/` is touched: a file or a
+Each run removes the symlinks into the date folders that no longer belong in
+their collection's directory, and the directories (and JSON) of collections that
+were deleted or renamed. Nothing else in `collections/` is touched: a file or a
 symlink you put there stays, and a directory that still holds one after its
 symlinks are removed stays too, with its JSON.
 
 Each file is downloaded exactly once regardless of how many collections it
-appears in, and written once: straight into `originals/`, with no copy left in
+appears in, and written once: straight to its save path, with no copy left in
 the cache. An original the cache already held is copied from there instead. On
 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
@@ -586,14 +596,15 @@ 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-<fileID>.<ext>-<pid>-<random>.tmp`. A run that is killed can leave
-one of these temporary files behind; the next backup deletes those whose process
-is no longer running. The content cache uses the same scheme, and opening a
-library deletes the temporary files in the cache whose process is no longer
-running, so a download another process has in progress in the same cache is left
-alone. The rename replaces whatever was at the destination rather than 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.
+`.quak-backup-YYYY-MM-DD.<fileID>.<ext>-<pid>-<random>.tmp`. A run that is
+killed can leave one of these temporary files behind; the next backup deletes
+those whose process is no longer running. The content cache uses the same
+scheme, and opening a library deletes the temporary files in the cache whose
+process is no longer running, so a download another process has in progress in
+the same cache is left alone. The rename replaces whatever was at the
+destination rather than 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
 
@@ -636,10 +647,10 @@ background, so an unreachable server does not block opening.
 `LibraryOptions`:
 
 | Option                   | Default                                            | Meaning                                                              |
-| ------------------------ | -------------------------------------------------- | --------------------------------------------------------------------- |
+| ------------------------ | -------------------------------------------------- | -------------------------------------------------------------------- |
 | `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`      | none                                               | backup destination; an original already stored there counts as cached |
+| `downloadDirectory`      | `photos` in the working directory                  | root of the save paths; an original stored there counts as cached    |
 | `refreshIntervalSeconds` | `3`                                                | background refresh cadence                                           |
 | `precacheThumbnails`     | `true`                                             | prefetch every thumbnail, newest first                               |
 | `precacheOriginals`      | `true`                                             | prefetch the favorites album and the latest-window originals         |
@@ -651,6 +662,9 @@ background, so an unreachable server does not block opening.
 | `onProgress`             | none                                               | refresh/ML/precache progress callback (`RefreshEvent`)               |
 | `contentSource`          | the client's own                                   | override the byte source (mainly for tests)                          |
 
+The default `downloadDirectory` is resolved against the working directory once,
+when the library opens; `lib.downloadDirectory` holds the result.
+
 Concurrency is set through `pools`: construct
 `new RequestPools({ metadataConcurrency, contentConcurrency, thumbnailConcurrency })`
 and pass it. The three pools default to 10 / 5 / 25 (see Request pools below).
@@ -702,20 +716,26 @@ and `originalPath`, and `photo.year`, the local-time year of `takenAt`, all as
 synchronous getters read from RAM; `photo.record()` → `PhotoRecord`. Two more
 synchronous getters look at the disk and never touch the network:
 
-- `photo.savePath` → `string | undefined` — where `lib.backup()` writes the
-  original, `originals/<fileID>.<ext>` under the `downloadDirectory` the library
-  was opened with, whether or not it is there yet: for a live photo already
-  stored, its image. For a live photo not yet stored, it carries the title's
-  extension, and the backup may store the image under a different one, found
-  inside the live photo. `undefined` when the library has no `downloadDirectory`
-  or no content source.
-- `photo.isLocal` → `boolean` — whether the whole original is at `savePath`.
+- `photo.savePath` → `string` — where `photo.download()` and `lib.backup()` put
+  the original, whether or not it is there yet:
+  `YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID>.<ext>` under the library's
+  `downloadDirectory` (see Backup layout above for the date and the extension).
+  For a live photo already stored, its image. For a live photo not yet stored,
+  it carries the title's extension, and the image may be stored under a
+  different one, found inside the live photo. It needs no content source.
+- `photo.isLocal` → `boolean` — whether the whole original is at `savePath`. A
+  copy only in the cache does not count.
 
-Four async methods may download:
+These async methods may download:
 
 - `await photo.original(opts?)` → `{ path, bytes, videoPath? }` — the
   full-resolution file. For a live photo, `path` and `bytes` are its image's and
   `videoPath` is its video.
+- `await photo.download()` → `{ path, bytes, videoPath? }`, as `original()` —
+  puts the original at `savePath`, creating its folders. When it is already
+  there, nothing is written. When the cache holds it, it is copied from the
+  cache; otherwise it is fetched straight to `savePath`, with no copy left in
+  the cache. Afterwards `isLocal` is true.
 - `await photo.thumbnail(opts?)` → `{ path, bytes }`.
 - `await photo.content(opts?)` → `Uint8Array` — the original's bytes, read
   through `original()`; for a live photo, its image's.
@@ -728,13 +748,20 @@ Four async methods may download:
   UTC. EXIF is read from any image format exifreader reads (such as JPEG,
   HEIC/HEIF, AVIF, PNG, WebP and TIFF), a live photo's image included. Any other
   original gives `{}`, and a video gives `{}` without being downloaded.
+- `await photo.make(opts?)`, and likewise `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` → one field of `exif()` each, typed as in `PhotoExif`, or
+  `undefined` when the file lacks it. Each calls `exif()` with its `opts`, so
+  each call reads the original again.
 
 They serve from the on-disk content cache when the bytes are present and
 otherwise fetch through the pools; `original()`, `content()` and `exif()` also
-serve an original the backup has already stored. `opts.onProgress` reports
+serve an original already stored at its save path. `opts.onProgress` reports
 per-file progress. They throw when the library was opened without a content
-source. An original that `content()` or `exif()` downloads lands in the cache,
-which does not make `isLocal` true; only `lib.backup()` does.
+source. An original that `original()`, `content()` or `exif()` downloads lands
+in the cache, which does not make `isLocal` true; only `download()` and
+`lib.backup()` do.
 
 Lower-level accessors that return decrypted model objects (which hold key
 material) are also available: `listCollections()`, `getCollection(id)`,
@@ -777,15 +804,15 @@ photos newest first). `lib.subscribe({ onChange })` delivers a `LibraryChange`
   default limit 20). quak bundles no text encoder, so `searchByEmbedding` takes
   a query vector the caller produced elsewhere.
 - `await lib.backup(opts?)` → `BackupResult`. It waits for a refresh as
-  `fresh()` does, fetches every in-scope original not already in the backup
-  (and, with `includeThumbnails`, thumbnails) through the content cache, and
-  rebuilds the on-disk backup tree with a durable failure ledger. A fetched
-  original is written straight into the backup's `originals/` and not into the
-  cache, which then counts it as present; one the cache already held is copied
-  from there. `BackupOptions`: `downloadDirectory` (falls back to the one
-  `open()` was given), `includeOriginals` (default `true`), `includeThumbnails`
-  (default `false`), `onlyAlbumNames`, and `onProgress`. See Backup layout above
-  for the tree it writes.
+  `fresh()` does, puts every in-scope original not already at its save path
+  there as `photo.download()` does (and, with `includeThumbnails`, fetches
+  thumbnails) through the content cache, and rebuilds the on-disk backup tree
+  with a durable failure ledger. A fetched original is written straight to its
+  save path and not into the cache, which then counts it as present; one the
+  cache already held is copied from there. `BackupOptions`: `downloadDirectory`
+  (falls back to the library's), `includeOriginals` (default `true`),
+  `includeThumbnails` (default `false`), `onlyAlbumNames`, and `onProgress`. See
+  Backup layout above for the tree it writes.
 
 ### Request pools
 
@@ -816,7 +843,7 @@ When `metadata.json` belongs to a different account than the client's,
 originals and thumbnails are kept; they are reached only through the files the
 current account's records name.
 
-A live photo's original is cached as in the backup: its image and its video,
+A live photo's original is cached as at its save path: its image and its video,
 each `originals/<fileID>.<ext>` with its own extension, and
 `originals/<fileID>.livephoto.json` naming them; the two are evicted together. A
 live photo that an earlier version cached as its ZIP is not served: the library
@@ -840,7 +867,7 @@ from a very old client, is stored unchecked.
 - `src/library/index.ts`: `Library`, `LibraryOptions`, `LibraryStatus`,
   `LibraryClient`, `RefreshEvent`
 - `src/library/read.ts`: `Album`, `Photo`, `AlbumsAPI`, `PhotosAPI`,
-  `TimelineAPI`, `PhotoFilter`, `TimelineGroup`, `GroupBy`
+  `TimelineAPI`, `PhotoFilter`, `TimelineGroup`, `GroupBy`, `SavePathLookup`
 - `src/library/content.ts`: `ContentResult`, `ContentOptions`, `ThumbnailsAPI`,
   `EnsureOptions`, `EnsureResult`, `ContentSource`
 - `src/library/records.ts`: `PhotoRecord`, `AlbumRecord`, `LibrarySnapshot`,

TODO.md

@@ -25,6 +25,27 @@ declares one.
 
 # Completed Steps
 
+- 2026-10-01: A `Photo` has one async method for each field of `exif()`, named
+  and typed as in `PhotoExif`: `make()`, `model()`, `lensModel()`,
+  `dateTimeOriginal()`, `offsetTimeOriginal()`, `exposureTime()`, `fNumber()`,
+  `iso()`, `focalLength()`, `orientation()`, `gpsLatitude()`, `gpsLongitude()`
+  and `gpsAltitude()` (issue 148). Each calls `exif()` and returns its one
+  field, or undefined when the file lacks it. `Photo` implements a type with one
+  method per `PhotoExif` field, so the build's type check fails when a field has
+  no method. A test checks, on the JPEG and the HEIC, that each method gives the
+  same value as `exif()`.
+
+- 2026-10-01: Each original's save path is
+  `YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID>.<ext>` under the library's
+  download directory, which defaults to `photos` in the working directory (issue
+  143). The date is the photo's `takenAt` in the machine's time zone.
+  `photo.savePath` is always a string, with or without a content cache, and
+  `isLocal` is true only when the original is at its save path.
+  `photo.download()` puts the original there, copied from the cache when the
+  cache holds it and fetched otherwise. `lib.backup()` does the same for each
+  file, writes each file's JSON beside its original, and links `collections/` to
+  the save paths.
+
 - 2026-10-01: `photo.exif()` and `backup-metadata --exif` read EXIF from
   HEIC/HEIF originals, a live photo's HEIC image included, as well as JPEG and
   the other image formats `exifreader` reads (issue 145). `exifreader` replaces

src/backup.ts

@@ -2,29 +2,30 @@
 //
 // `lib.backup()` waits for a completed refresh of the library (a failed one
 // fails the backup before any file is touched), then, for every file in scope,
-// gets its original bytes onto disk under `downloadDirectory` and rebuilds the
-// derived views (per-file sidecars, per-collection symlink trees,
-// per-collection JSON) from the model. The on-disk layout is the historical
-// one:
+// puts its original at its save path under `downloadDirectory`, as
+// `Photo.download()` does, and rebuilds the derived views (per-file sidecars,
+// per-collection symlink trees, per-collection JSON) from the model. The
+// on-disk layout:
 //
 //     <downloadDirectory>/
-//         originals/<fileID>.<ext>     the decrypted bytes
-//         originals/<fileID>.json      per-file metadata sidecar
-//         collections/<name>/<title>   symlink into ../../originals
+//         YYYY/YYYY-MM/YYYY-MM-DD/
+//             YYYY-MM-DD.<fileID>.<ext>    the decrypted bytes (the save path)
+//             YYYY-MM-DD.<fileID>.json     per-file metadata sidecar
+//         collections/<name>/<title>       symlink to the original
 //         collections/<name>.json          per-collection metadata
 //         failures.json                    durable ledger of unresolved failures
 //
-// A live photo's original is its image and its video, `<fileID>.<ext>` each
-// with its own extension, and `originals/<fileID>.livephoto.json` naming them;
-// its album folders link both.
+// A live photo's original is its image and its video, each with its own
+// extension, beside `YYYY-MM-DD.<fileID>.livephoto.json` naming them; its album
+// folders link both.
 //
 // Crash-safety rests on two properties. Bytes are present-means-complete: an
-// original appears under `originals/` only via the content layer's atomic
+// original appears at its save path only via the content layer's atomic
 // temp-then-rename, so a file that exists is whole and is never re-fetched — an
-// interrupted run resumes by listing the directory. The derived views hold no
-// unique state, so they are rebuilt every run; that repairs stale sidecars and
-// missing or broken symlinks left by an earlier crash. A rebuild also removes
-// the symlinks into originals/ that no longer belong to an album, and the
+// interrupted run resumes by looking at the save paths. The derived views hold
+// no unique state, so they are rebuilt every run; that repairs stale sidecars
+// and missing or broken symlinks left by an earlier crash. A rebuild also
+// removes the symlinks to originals that no longer belong to an album, and the
 // directories of albums that no longer exist.
 //
 // Resilience (issue #8): no per-file condition aborts the run. A failed
@@ -48,24 +49,25 @@ import {
     symlinkSync,
     writeFileSync,
 } from "node:fs";
-import { copyFile, rename, rm } from "node:fs/promises";
-import { basename, dirname, extname, join, relative } from "node:path";
+import { dirname, extname, join, relative, resolve } from "node:path";
 
-import { fsyncPath, removeLeftoverTempFiles } from "./download/index.js";
+import { removeLeftoverTempFiles } from "./download/index.js";
 import { sanitizeFileName, withExtension } from "./filename.js";
 import {
-    nameInOriginals,
-    storedOriginal,
-    writeLivePhotoJSON,
+    copyAtomic,
+    placeOriginal,
+    savePath,
+    storedAtSavePath,
 } from "./library/content.js";
+import { representative } from "./library/records.js";
 import type { Collection, EnteFile } from "./model/types.js";
 
 export type ProgressCallback = (message: string) => void;
 
 export interface BackupOptions {
-    // Where the backup tree lives. Required: with none, `backup()` throws
-    // before any network traffic. A library opened with a `downloadDirectory`
-    // supplies the default.
+    // Where the backup tree lives. `lib.backup()` defaults it to the library's
+    // download directory; `runBackup` with none throws before any network
+    // traffic.
     downloadDirectory?: string;
     // Fetch and store full-resolution originals. Default true.
     includeOriginals?: boolean;
@@ -89,7 +91,7 @@ export interface BackupResult {
     totalFiles: number;
     // Originals fetched (or copied from the cache) this run.
     downloaded: number;
-    // Originals already present and left untouched.
+    // Originals already at their save path and left untouched.
     skipped: number;
     // Files with an unresolved failure after this run (the ledger size); the
     // CLI exits non-zero while this is above zero. A file can be both
@@ -107,8 +109,8 @@ export interface BackupLibrary {
     listFiles(collectionID: number): EnteFile[];
     // Get an original's bytes onto disk through the content cache/pools,
     // returning where they landed: `destination` when they were fetched now,
-    // otherwise wherever they already were (the cache, or a prior backup). A
-    // live photo lands as its image and its video, fetched now beside
+    // otherwise wherever they already were (the cache, or the library's save
+    // path). A live photo lands as its image and its video, fetched now beside
     // `destination`.
     original(
         fileID: number,
@@ -168,58 +170,6 @@ const classify = (err: unknown): FailureClass => {
 const errorMessage = (err: unknown): string =>
     err instanceof Error ? err.message : String(err);
 
-// 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
-// after it, so a power cut cannot leave a correctly named but short original.
-// The temp name carries this process's ID so a later run can tell a leftover
-// from a copy still in progress (see `removeLeftoverTempFiles`).
-const copyAtomic = async (src: string, dest: string): Promise<void> => {
-    if (src === dest) return;
-    const tmp = join(
-        dirname(dest),
-        `.quak-backup-${basename(dest)}-${process.pid}-${Math.random()
-            .toString(36)
-            .slice(2)}.tmp`,
-    );
-    try {
-        await copyFile(src, tmp);
-        await fsyncPath(tmp);
-        // `rename` replaces the destination's directory entry: an existing
-        // symlink at `dest` is replaced, not followed, and the new file has
-        // the temp file's permissions (copied from `src`).
-        await rename(tmp, dest);
-        await fsyncPath(dirname(dest));
-    } finally {
-        await rm(tmp, { force: true });
-    }
-};
-
-// Put an original the library returned at `dest` in originals/, where a fresh
-// fetch already wrote it. A live photo's image and video go beside `dest`: when
-// they came from the cache they are copied, after removing whatever was at
-// `dest` (an earlier version's ZIP of the two). Then the JSON file naming them
-// is written, which is what makes the live photo count as stored.
-const placeOriginal = async (
-    file: EnteFile,
-    dest: string,
-    got: { path: string; videoPath?: string },
-): Promise<void> => {
-    if (got.videoPath === undefined) {
-        await copyAtomic(got.path, dest);
-        return;
-    }
-    const originalsDir = dirname(dest);
-    const path = join(originalsDir, basename(got.path));
-    const videoPath = join(originalsDir, basename(got.videoPath));
-    if (got.path !== path) {
-        await rm(dest, { force: true });
-        await copyAtomic(got.path, path);
-        await copyAtomic(got.videoPath, videoPath);
-    }
-    await writeLivePhotoJSON(originalsDir, file.id, { path, videoPath });
-};
-
 // Ensure `linkPath` is a symlink to `target`, rebuilding a missing, wrong, or
 // non-symlink entry. Throws on failure (a directory in the way, no permission)
 // so the caller records it and moves on rather than aborting the run.
@@ -291,36 +241,55 @@ const linksFor = (
     }));
 };
 
-// Remove the symlinks in the album directory `dir` that point into
-// `originalsDir` and are not named in `keep`. Nothing else in the directory
-// is touched: anything else there was put there by the user.
+// Every date folder (`YYYY/YYYY-MM/YYYY-MM-DD/`) under `root`, whether or not a
+// file in this backup is saved there. A folder that cannot be read is skipped.
+const dateFolders = (root: string): string[] => {
+    const subfolders = (dir: string, name: RegExp): string[] => {
+        try {
+            return readdirSync(dir, { withFileTypes: true })
+                .filter((e) => e.isDirectory() && name.test(e.name))
+                .map((e) => join(dir, e.name));
+        } catch {
+            return [];
+        }
+    };
+    return subfolders(root, /^\d{4}$/)
+        .flatMap((year) => subfolders(year, /^\d{4}-\d\d$/))
+        .flatMap((month) => subfolders(month, /^\d{4}-\d\d-\d\d$/));
+};
+
+// Whether the entry at `path` is a symlink a backup to `root` made: one to an
+// original in a `YYYY/YYYY-MM/YYYY-MM-DD/` folder of `root`.
+const linksToOriginal = (path: string, root: string): boolean => {
+    if (!lstatSync(path).isSymbolicLink()) return false;
+    const target = relative(root, resolve(dirname(path), readlinkSync(path)));
+    return /^\d{4}\/\d{4}-\d\d\/\d{4}-\d\d-\d\d\/[^/]+$/.test(target);
+};
+
+// Remove the symlinks in the album directory `dir` that point to an original
+// in `root` and are not named in `keep`. Nothing else in the directory is
+// touched: anything else there was put there by the user.
 const removeStaleLinks = (
     dir: string,
     keep: Set<string>,
-    originalsDir: string,
+    root: string,
 ): void => {
-    const target = relative(dir, originalsDir);
     for (const name of readdirSync(dir)) {
         if (keep.has(name)) continue;
         const path = join(dir, name);
-        if (
-            lstatSync(path).isSymbolicLink() &&
-            dirname(readlinkSync(path)) === target
-        ) {
-            rmSync(path);
-        }
+        if (linksToOriginal(path, root)) rmSync(path);
     }
 };
 
 // Remove the directories under `collectionsDir` that an earlier run wrote for
 // an album that is gone or renamed: a directory not named in `current` with a
 // `<name>.json` beside it holding an album ID, which is what a run writes. Its
-// symlinks into originals/ are removed; if that leaves it empty, it and its
-// JSON are deleted, otherwise both stay for what the user put there.
+// symlinks to originals in `root` are removed; if that leaves it empty, it and
+// its JSON are deleted, otherwise both stay for what the user put there.
 const removeStaleAlbumDirs = (
     collectionsDir: string,
     current: Set<string>,
-    originalsDir: string,
+    root: string,
 ): void => {
     for (const entry of readdirSync(collectionsDir, { withFileTypes: true })) {
         if (!entry.isDirectory() || current.has(entry.name)) continue;
@@ -334,7 +303,7 @@ const removeStaleAlbumDirs = (
             continue;
         }
         const dir = join(collectionsDir, entry.name);
-        removeStaleLinks(dir, new Set(), originalsDir);
+        removeStaleLinks(dir, new Set(), root);
         if (readdirSync(dir).length > 0) continue;
         rmdirSync(dir);
         rmSync(jsonPath);
@@ -402,34 +371,48 @@ export const runBackup = async (
     log("Refreshing library...");
     await lib.refresh();
 
-    const originalsDir = join(downloadDirectory, "originals");
     const collectionsDir = join(downloadDirectory, "collections");
     const thumbnailsDir = join(downloadDirectory, "thumbnails");
-    mkdirSync(originalsDir, { recursive: true });
     mkdirSync(collectionsDir, { recursive: true });
     if (includeThumbnails) mkdirSync(thumbnailsDir, { recursive: true });
-    removeLeftoverTempFiles(originalsDir);
     removeLeftoverTempFiles(thumbnailsDir);
+    for (const dir of dateFolders(downloadDirectory)) {
+        removeLeftoverTempFiles(dir);
+    }
 
     const ledgerPath = join(downloadDirectory, "failures.json");
     const ledger = loadLedger(ledgerPath);
     const now = Date.now();
 
     // Collections in scope, and the distinct files across them (a file shared
-    // by two albums is one original).
+    // by two albums is one original). Each file is the membership
+    // `representative` picks from all of its albums, in scope or not, so it is
+    // saved at the path `photo.savePath` names.
     const allCollections = lib.listCollections();
     const collections = allCollections.filter((c) =>
         only ? only.has(c.name) : true,
     );
     const collectionName = new Map<number, string>();
-    for (const c of collections) collectionName.set(c.id, c.name);
+    for (const c of allCollections) collectionName.set(c.id, c.name);
 
-    const distinct = new Map<number, EnteFile>();
+    const memberships = new Map<number, EnteFile[]>();
     const filesByCollection = new Map<number, EnteFile[]>();
-    for (const c of collections) {
+    for (const c of allCollections) {
         const files = lib.listFiles(c.id);
         filesByCollection.set(c.id, files);
-        for (const f of files) if (!distinct.has(f.id)) distinct.set(f.id, f);
+        for (const f of files) {
+            const arr = memberships.get(f.id);
+            if (arr) arr.push(f);
+            else memberships.set(f.id, [f]);
+        }
+    }
+    const distinct = new Map<number, EnteFile>();
+    for (const c of collections) {
+        for (const f of filesByCollection.get(c.id)!) {
+            if (!distinct.has(f.id)) {
+                distinct.set(f.id, representative(memberships.get(f.id)!));
+            }
+        }
     }
 
     const errors: BackupError[] = [];
@@ -465,25 +448,22 @@ export const runBackup = async (
         failedThisRun.add(file.id);
     };
 
-    // Phase 1: get the bytes. Fetch each pending original (and optional
-    // thumbnail) through the content cache/pools and place it under the backup
-    // tree; a present file is left as is.
+    // Phase 1: get the bytes. Put each pending original at its save path
+    // through the content cache/pools, as `Photo.download()` does, and fetch
+    // the optional thumbnails; a present file is left as is.
     if (includeOriginals) {
         for (const [fileID, file] of distinct) {
-            if (storedOriginal(originalsDir, file) !== undefined) {
+            if (storedAtSavePath(downloadDirectory, file) !== undefined) {
                 skipped++;
                 continue;
             }
-            const dest = join(originalsDir, nameInOriginals(file));
             try {
                 log(`Fetching original ${file.metadata.title} (${fileID})...`);
-                // A fetched original is written straight to `dest` (a live
-                // photo beside it); only one that was already cached elsewhere
-                // is copied.
-                await placeOriginal(
-                    file,
-                    dest,
-                    await lib.original(fileID, dest),
+                // A fetched original is written straight to its save path (a
+                // live photo beside it); only one that was already cached
+                // elsewhere is copied.
+                await placeOriginal(downloadDirectory, file, (dest) =>
+                    lib.original(fileID, dest),
                 );
                 downloaded++;
             } catch (err) {
@@ -519,9 +499,10 @@ export const runBackup = async (
     // Phase 2: rebuild the derived views from the model. Sidecars first, for
     // every present original (this repairs stale ones).
     if (includeOriginals) {
-        for (const [fileID, file] of distinct) {
-            if (storedOriginal(originalsDir, file) !== undefined) {
-                writeSidecar(join(originalsDir, `${fileID}.json`), file);
+        for (const file of distinct.values()) {
+            if (storedAtSavePath(downloadDirectory, file) !== undefined) {
+                const path = savePath(downloadDirectory, file);
+                writeSidecar(withExtension(path, ".json"), file);
             }
         }
     }
@@ -543,7 +524,11 @@ export const runBackup = async (
         allCollections.map((c, i) => [c.id, dirNames[i]!]),
     );
     try {
-        removeStaleAlbumDirs(collectionsDir, new Set(dirNames), originalsDir);
+        removeStaleAlbumDirs(
+            collectionsDir,
+            new Set(dirNames),
+            downloadDirectory,
+        );
     } catch (err) {
         log(`FAILED removing old album directories: ${errorMessage(err)}`);
     }
@@ -553,13 +538,18 @@ export const runBackup = async (
         const colDir = join(collectionsDir, colDirName);
         mkdirSync(colDir, { recursive: true });
 
+        // Every album links the one original, saved from the file's entry in
+        // `distinct`.
         const files = filesByCollection.get(c.id) ?? [];
         const links = files.flatMap((f) =>
-            linksFor(f, storedOriginal(originalsDir, f)),
+            linksFor(
+                f,
+                storedAtSavePath(downloadDirectory, distinct.get(f.id)!),
+            ),
         );
         const linkNames = uniqueNames(links, true);
         try {
-            removeStaleLinks(colDir, new Set(linkNames), originalsDir);
+            removeStaleLinks(colDir, new Set(linkNames), downloadDirectory);
         } catch (err) {
             log(`FAILED removing old links in ${c.name}: ${errorMessage(err)}`);
         }

src/index.ts

@@ -53,6 +53,7 @@ export {
     type PhotoFilter,
     type TimelineGroup,
     type GroupBy,
+    type SavePathLookup,
     type ContentSource,
     type ContentResult,
     type ContentEvent,

src/library/content.ts

@@ -23,6 +23,11 @@
 // original with no recorded hash is stored unchecked, as the upstream client
 // does; thumbnails have none. On top of that this module refuses to record a
 // stored file that came out empty.
+//
+// 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.
 
 import {
     closeSync,
@@ -34,8 +39,10 @@ import {
 } from "node:fs";
 import {
     chmod,
+    copyFile,
     mkdir,
     readdir,
+    rename,
     rm,
     stat,
     statfs,
@@ -47,13 +54,15 @@ import type { ApiClient } from "../api/client.js";
 import {
     downloadFile,
     downloadThumbnail,
+    fsyncPath,
     type ProgressCallback,
     removeLeftoverTempFiles,
     writeAtomic,
 } from "../download/index.js";
-import { safeExtension } from "../filename.js";
+import { safeExtension, withExtension } from "../filename.js";
 import type { EnteFile } from "../model/types.js";
 import type { Priority, RequestPools } from "./pools.js";
+import { takenAtOf } from "./records.js";
 
 const DIR_MODE = 0o700;
 const FILE_MODE = 0o600;
@@ -108,11 +117,9 @@ export interface ContentOptions {
 export interface PhotoContent {
     original(fileID: number, opts?: ContentOptions): Promise<ContentResult>;
     thumbnail(fileID: number, opts?: ContentOptions): Promise<ContentResult>;
-    // Where a backup stores the original, whether or not it is there yet. For
-    // a live photo not yet stored, it carries the title's extension, and the
-    // backup may store the image under a different one.
-    savePath(fileID: number): string | undefined;
-    isLocal(fileID: number): boolean;
+    // Put the original at the save path of `file`, the copy the `Photo` holds,
+    // and return it there.
+    download(file: EnteFile): Promise<ContentResult>;
 }
 
 export interface EnsureResult {
@@ -199,10 +206,10 @@ export interface ContentCacheOptions {
     pools: RequestPools;
     source: ContentSource;
     cacheDirectory: string;
-    // The backup destination (issue-level `downloadDirectory`). An original
-    // already stored there by a backup counts as present, so the cache serves
-    // it rather than fetching a second copy.
-    downloadDirectory?: string;
+    // The root of the save paths. An original already stored at its save path
+    // counts as present, so the cache serves it rather than fetching a second
+    // copy.
+    downloadDirectory: string;
     // Resolve any membership of a file; every membership shares the underlying
     // content key, so any one decrypts the same bytes.
     getFile: (fileID: number) => EnteFile | undefined;
@@ -229,11 +236,27 @@ class AbortDrop extends Error {
     }
 }
 
-// The name of a file's original in originals/: `<fileID><ext>`, the extension
-// taken from the title (or `.bin`). A backup names its originals the same way.
+// The name of a file's original in the cache's originals/: `<fileID><ext>`, the
+// extension taken from the title (or `.bin`).
 export const nameInOriginals = (file: EnteFile): string =>
     `${file.id}${safeExtension(file.metadata.title)}`;
 
+const pad = (n: number): string => String(n).padStart(2, "0");
+
+// Where the original of `file` is saved under `root`:
+// `YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID><ext>`, dated by the photo's
+// `takenAt` in this machine's time zone, with the extension taken from the
+// title (or `.bin`). A live photo is stored as its image and its video beside
+// this path, each with the extension found inside the live photo.
+export const savePath = (root: string, file: EnteFile): string => {
+    const taken = new Date(takenAtOf(file));
+    const year = String(taken.getFullYear());
+    const month = `${year}-${pad(taken.getMonth() + 1)}`;
+    const day = `${month}-${pad(taken.getDate())}`;
+    const ext = safeExtension(file.metadata.title);
+    return join(root, year, month, day, `${day}.${file.id}${ext}`);
+};
+
 // The fileID a cache filename encodes, or undefined when the name is not one
 // the cache writes (`<digits><ext>`).
 const fileIDFromName = (name: string): number | undefined => {
@@ -279,28 +302,29 @@ const isZip = (path: string): boolean => {
 
 // A live photo's image and video are named with the extensions from inside its
 // ZIP, so their names alone do not say which is which. Wherever the cache or a
-// backup stores one, a JSON file of this name beside them names both.
-const livePhotoJSONName = (fileID: number): string =>
-    `${fileID}.livephoto.json`;
+// save path stores one, a JSON file of this name beside them names both.
+// `name` is the original's name without its extension: `<fileID>` in the
+// cache, `YYYY-MM-DD.<fileID>` at the save path.
+const livePhotoJSONName = (name: string): string => `${name}.livephoto.json`;
 
 // The image and video that the live photo's JSON file in `dir` names, or
-// undefined when there is none. Only names of the form the cache writes are
-// taken, so the file cannot point outside `dir`.
+// undefined when there is none. Only `name` with an extension is taken, so the
+// file cannot point outside `dir`.
 const readLivePhotoJSON = (
     dir: string,
-    fileID: number,
+    name: string,
 ): { path: string; videoPath: string } | undefined => {
-    const valid = (name: unknown): name is string =>
-        typeof name === "string" && name === `${fileID}${safeExtension(name)}`;
+    const valid = (part: unknown): part is string =>
+        typeof part === "string" && part === `${name}${safeExtension(part)}`;
     try {
         const { image, video } = JSON.parse(
-            readFileSync(join(dir, livePhotoJSONName(fileID)), "utf-8"),
+            readFileSync(join(dir, livePhotoJSONName(name)), "utf-8"),
         );
         if (valid(image) && valid(video)) {
             return { path: join(dir, image), videoPath: join(dir, video) };
         }
     } catch {
-        // No such file, or not one the cache wrote.
+        // No such file, or not one quak wrote.
     }
     return undefined;
 };
@@ -308,11 +332,11 @@ const readLivePhotoJSON = (
 // Write the JSON file naming a live photo's image and video, both in `dir`.
 export const writeLivePhotoJSON = (
     dir: string,
-    fileID: number,
+    name: string,
     stored: { path: string; videoPath: string },
 ): Promise<void> =>
     writeAtomic(
-        join(dir, livePhotoJSONName(fileID)),
+        join(dir, livePhotoJSONName(name)),
         new TextEncoder().encode(
             JSON.stringify({
                 image: basename(stored.path),
@@ -321,17 +345,19 @@ export const writeLivePhotoJSON = (
         ),
     );
 
-// The original of `file` as the cache or a backup stored it in `dir`, when all
-// of it is there: `<fileID><ext>`, or a live photo's image and video.
+// The original of `file` as stored in `dir` under `name` (without its
+// extension), when all of it is there: `<name><ext>`, or a live photo's image
+// and video.
 export const storedOriginal = (
     dir: string,
+    name: string,
     file: EnteFile,
 ): { path: string; videoPath?: string } | undefined => {
     if (file.metadata.fileType !== "livePhoto") {
-        const path = join(dir, nameInOriginals(file));
+        const path = join(dir, `${name}${safeExtension(file.metadata.title)}`);
         return hasContent(path) ? { path } : undefined;
     }
-    const stored = readLivePhotoJSON(dir, file.id);
+    const stored = readLivePhotoJSON(dir, name);
     return stored !== undefined &&
         hasContent(stored.path) &&
         hasContent(stored.videoPath)
@@ -339,10 +365,76 @@ export const storedOriginal = (
         : undefined;
 };
 
+// The original of `file` as stored at its save path under `root`, when all of
+// it is there.
+export const storedAtSavePath = (
+    root: string,
+    file: EnteFile,
+): { path: string; videoPath?: string } | undefined => {
+    const path = savePath(root, file);
+    return storedOriginal(dirname(path), basename(path, extname(path)), file);
+};
+
+// 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
+// after it, so a power cut cannot leave a correctly named but short original.
+// The temp name carries this process's ID so a later run can tell a leftover
+// from a copy still in progress (see `removeLeftoverTempFiles`).
+export const copyAtomic = async (src: string, dest: string): Promise<void> => {
+    if (src === dest) return;
+    const tmp = join(
+        dirname(dest),
+        `.quak-backup-${basename(dest)}-${process.pid}-${Math.random()
+            .toString(36)
+            .slice(2)}.tmp`,
+    );
+    try {
+        await copyFile(src, tmp);
+        await fsyncPath(tmp);
+        // `rename` replaces the destination's directory entry: an existing
+        // symlink at `dest` is replaced, not followed, and the new file has
+        // the temp file's permissions (copied from `src`).
+        await rename(tmp, dest);
+        await fsyncPath(dirname(dest));
+    } finally {
+        await rm(tmp, { force: true });
+    }
+};
+
+// Put the original of `file` at its save path under `root`, creating its
+// folders. `get` is given the save path and returns where the original is: a
+// fetch writes it there, and a copy the cache holds is copied there. A live
+// photo's image and video go beside the save path, each with its own
+// extension: when they came from the cache they are copied. Then the JSON file
+// naming them is written, which is what makes the live photo count as stored.
+export const placeOriginal = async (
+    root: string,
+    file: EnteFile,
+    get: (dest: string) => Promise<{ path: string; videoPath?: string }>,
+): Promise<{ path: string; videoPath?: string }> => {
+    const dest = savePath(root, file);
+    await mkdir(dirname(dest), { recursive: true });
+    const got = await get(dest);
+    if (got.videoPath === undefined) {
+        await copyAtomic(got.path, dest);
+        return { path: dest };
+    }
+    const path = withExtension(dest, extname(got.path));
+    const videoPath = withExtension(dest, extname(got.videoPath));
+    if (got.path !== path) {
+        await copyAtomic(got.path, path);
+        await copyAtomic(got.videoPath, videoPath);
+    }
+    const name = basename(dest, extname(dest));
+    await writeLivePhotoJSON(dirname(dest), name, { path, videoPath });
+    return { path, videoPath };
+};
+
 export class ContentCache implements PhotoContent, ThumbnailsAPI {
     private readonly pools: RequestPools;
     private readonly source: ContentSource;
-    private readonly downloadDirectory?: string;
+    private readonly downloadDirectory: string;
     private readonly getFile: (fileID: number) => EnteFile | undefined;
     private readonly originalsDir: string;
     private readonly thumbnailsDir: string;
@@ -440,32 +532,23 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
         return this.get(fileID, "thumbnail", "on-demand", opts?.onProgress);
     }
 
-    // Where a backup to the download directory stores the file's original,
-    // whether or not it is there yet: for a live photo already stored, its
-    // image. For a live photo not yet stored, it carries the title's
-    // extension, and the backup may store the image under a different one.
-    // Undefined with no download directory.
-    savePath(fileID: number): string | undefined {
-        const file = this.getFile(fileID);
-        if (this.downloadDirectory === undefined || file === undefined)
-            return undefined;
-        const dir = join(this.downloadDirectory, "originals");
-        return (
-            storedOriginal(dir, file)?.path ?? join(dir, nameInOriginals(file))
-        );
+    // Put the original at the save path of `file` under the download directory
+    // and return it there. `file` is the copy the `Photo` holds, so the path is
+    // the one its `savePath` names, even after a refresh changed the date. One
+    // already stored there is returned as it is; one the cache holds is copied
+    // from it; any other is fetched straight to the save path, with no copy
+    // left in the cache.
+    async download(file: EnteFile): Promise<ContentResult> {
+        const root = this.downloadDirectory;
+        const saved =
+            storedAtSavePath(root, file) ??
+            (await placeOriginal(root, file, (dest) =>
+                this.backupOriginal(file.id, dest),
+            ));
+        return { ...saved, bytes: fileSize(saved.path) ?? 0 };
     }
 
-    // Whether the whole original is in the download directory, as a backup
-    // stores it. A copy only in the cache does not count.
-    isLocal(fileID: number): boolean {
-        const file = this.getFile(fileID);
-        if (this.downloadDirectory === undefined || file === undefined)
-            return false;
-        const dir = join(this.downloadDirectory, "originals");
-        return storedOriginal(dir, file) !== undefined;
-    }
-
-    // Get an original for a backup. One not present anywhere is written
+    // Get an original for a save path. One not present anywhere is written
     // straight to `destination` and recorded there, so no second copy lands
     // in the cache; one already present is returned where it is.
     async backupOriginal(
@@ -635,12 +718,9 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
             known.delete(fileID);
         }
 
-        // An original a backup already stored counts as present.
-        if (kind === "original" && this.downloadDirectory !== undefined) {
-            const stored = storedOriginal(
-                join(this.downloadDirectory, "originals"),
-                file,
-            );
+        // An original already stored at its save path counts as present.
+        if (kind === "original") {
+            const stored = storedAtSavePath(this.downloadDirectory, file);
             if (stored !== undefined) {
                 this.originals.set(fileID, stored);
                 return {
@@ -676,7 +756,7 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
                         ? this.beginOriginalWrite(fileID)
                         : null;
                 try {
-                    const stored = await this.download(
+                    const stored = await this.fetchInto(
                         file,
                         dest,
                         kind,
@@ -691,12 +771,12 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
                             );
                         }
                     }
-                    // A backup records its own live photos.
+                    // `placeOriginal` records a live photo it saves.
                     if (
                         stored.videoPath !== undefined &&
                         opts?.destination === undefined
                     ) {
-                        await writeLivePhotoJSON(dir, fileID, {
+                        await writeLivePhotoJSON(dir, String(fileID), {
                             path: stored.path,
                             videoPath: stored.videoPath,
                         });
@@ -719,7 +799,7 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
 
     // Fetch into `destination`, returning where the bytes landed: there, or
     // for a live photo, its image and video beside it.
-    private async download(
+    private async fetchInto(
         file: EnteFile,
         destination: string,
         kind: Kind,
@@ -744,10 +824,10 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
         await utimes(path, now, now).catch(() => undefined);
     }
 
-    // Every stored original that lives under `originalsDir` (a backup-directory
-    // hit recorded in the map is excluded), with its size and mtime; a live
+    // Every stored original that lives under `originalsDir` (a save-path hit
+    // recorded in the map is excluded), with its size and mtime; a live
     // photo's size includes its video. Entries whose file has vanished are
-    // dropped from the map. Backups and thumbnails are never counted.
+    // dropped from the map. Save paths and thumbnails are never counted.
     private async measureOriginals(): Promise<{
         entries: {
             fileID: number;
@@ -853,7 +933,7 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
                         await rm(
                             join(
                                 this.originalsDir,
-                                livePhotoJSONName(e.fileID),
+                                livePhotoJSONName(String(e.fileID)),
                             ),
                             { force: true },
                         );
@@ -907,8 +987,8 @@ export class ContentCache implements PhotoContent, ThumbnailsAPI {
             // earlier version stored under the image's name, and is removed.
             // Any other is left alone: another process may have just stored
             // it and not yet written the JSON file.
-            const livePhoto = names.has(livePhotoJSONName(id))
-                ? readLivePhotoJSON(dir, id)
+            const livePhoto = names.has(livePhotoJSONName(String(id)))
+                ? readLivePhotoJSON(dir, String(id))
                 : undefined;
             if (livePhoto !== undefined) {
                 into.set(id, livePhoto);

src/library/index.ts

@@ -27,7 +27,7 @@
 // never masked by a subsequent empty refresh.
 
 import { rm } from "node:fs/promises";
-import { join } from "node:path";
+import { join, resolve } from "node:path";
 import envPaths from "env-paths";
 
 import { MetadataStore } from "./store.js";
@@ -49,9 +49,12 @@ import {
     type PhotosAPI,
     type TimelineAPI,
     type FreshReads,
+    type SavePathLookup,
 } from "./read.js";
 import {
     ContentCache,
+    savePath,
+    storedAtSavePath,
     type ContentSource,
     type ThumbnailsAPI,
     type EnsureOptions,
@@ -70,6 +73,7 @@ export {
     type PhotoFilter,
     type TimelineGroup,
     type GroupBy,
+    type SavePathLookup,
 } from "./read.js";
 export {
     type ContentSource,
@@ -169,8 +173,10 @@ export interface LibraryOptions {
     // Where `metadata.json` lives. Defaults to the env-paths cache directory
     // plus the user id, so each account has its own cache.
     cacheDirectory?: string;
-    // Persistent backup destination. The refresh loop does not use it; the
-    // content cache treats an original already stored there as present.
+    // The root of every photo's save path, where `Photo.download()` and
+    // `lib.backup()` put originals. Defaults to `photos` in the working
+    // directory at open. The content cache treats an original already stored
+    // at its save path as present.
     downloadDirectory?: string;
     refreshIntervalSeconds?: number;
     onProgress?: RefreshProgressCallback;
@@ -234,7 +240,7 @@ export interface LibraryStatus {
 
 export class Library {
     readonly cacheDirectory: string;
-    readonly downloadDirectory?: string;
+    readonly downloadDirectory: string;
 
     // The in-process read surface (issue #44). Each namespace answers
     // synchronously from the live record projection; no read touches the
@@ -296,7 +302,7 @@ export class Library {
         store: MetadataStore;
         userID: number;
         cacheDirectory: string;
-        downloadDirectory?: string;
+        downloadDirectory: string;
         intervalMs: number;
         onProgress?: RefreshProgressCallback;
         pools: RequestPools;
@@ -320,8 +326,14 @@ export class Library {
         // The read namespaces derive fresh from the store on each call, so they
         // always reflect the latest refresh.
         const derive = (): DerivedRecords => this.deriveNow();
-        this.albums = makeAlbumsAPI(derive, this.cache);
-        this.photos = makePhotosAPI(derive, this.cache);
+        const root = this.downloadDirectory;
+        const saves: SavePathLookup = {
+            savePath: (file) =>
+                storedAtSavePath(root, file)?.path ?? savePath(root, file),
+            isLocal: (file) => storedAtSavePath(root, file) !== undefined,
+        };
+        this.albums = makeAlbumsAPI(derive, saves, this.cache);
+        this.photos = makePhotosAPI(derive, saves, this.cache);
         this.timeline = makeTimelineAPI(derive);
         this.thumbnails = {
             ensure: (opts: EnsureOptions): Promise<EnsureResult[]> => {
@@ -350,6 +362,13 @@ export class Library {
         const { userID } = opts.client.whoami();
         const cacheDirectory =
             opts.cacheDirectory ?? defaultCacheDirectory(userID);
+        if (opts.downloadDirectory === "") {
+            throw new Error(
+                "library: downloadDirectory is empty (leave it out to save " +
+                    "under photos/ in the working directory)",
+            );
+        }
+        const downloadDirectory = opts.downloadDirectory ?? resolve("photos");
         const metadataPath = join(cacheDirectory, "metadata.json");
         let store = await MetadataStore.load(metadataPath);
         // A cache directory given explicitly can hold another account's cache.
@@ -404,7 +423,7 @@ export class Library {
                 pools,
                 source,
                 cacheDirectory,
-                downloadDirectory: opts.downloadDirectory,
+                downloadDirectory,
                 getFile: (fileID) => store.getFileByID(fileID),
                 cacheOriginalsMaxBytes: opts.cacheOriginalsMaxBytes,
                 freeBelowBytes: opts.freeBelowBytes,
@@ -426,7 +445,7 @@ export class Library {
             store,
             userID,
             cacheDirectory,
-            downloadDirectory: opts.downloadDirectory,
+            downloadDirectory,
             intervalMs,
             onProgress: opts.onProgress,
             pools,
@@ -470,9 +489,10 @@ export class Library {
         return this.store.getFile(collectionID, fileID);
     }
 
-    // Any membership of a file, addressed by file id alone. A file's own
-    // metadata (title, creationTime) is identical across the collections it
-    // belongs to, so this serves the point commands that hold only a fileID.
+    // The membership of a file its record is read from, addressed by file id
+    // alone. A file's own metadata (title, creationTime) is identical across
+    // the collections it belongs to, so this serves the point commands that
+    // hold only a fileID.
     getFileByID(fileID: number): EnteFile | undefined {
         return this.store.getFileByID(fileID);
     }
@@ -543,27 +563,20 @@ export class Library {
         };
     }
 
-    // Back up every in-scope file to `downloadDirectory` in the historical
-    // on-disk layout, with a durable failure ledger (issue #51). Waits for a
-    // completed refresh first, as `fresh()` does, joining one already running,
-    // and rejects before touching any file when it fails. Then fetches pending
-    // originals (and optional thumbnails) through the content cache and pools,
-    // and rebuilds the derived symlink/JSON views from the model. Throws before
-    // any network work when no download directory is available or no content
-    // cache backs the originals it must fetch.
+    // Back up every in-scope file to `opts.downloadDirectory`, or else the
+    // library's, each original at its save path, with a durable failure
+    // ledger (issue #51). Waits for a completed refresh first, as `fresh()`
+    // does, joining one already running, and rejects before touching any file
+    // when it fails. Then puts pending originals at their save paths as
+    // `Photo.download()` does (and optional thumbnails) through the content
+    // cache and pools, and rebuilds the derived symlink/JSON views from the
+    // model. Throws before any network work when no content cache backs the
+    // originals it must fetch.
     backup(opts?: BackupOptions): Promise<BackupResult> {
         const downloadDirectory =
             opts?.downloadDirectory ?? this.downloadDirectory;
         const includeOriginals = opts?.includeOriginals ?? true;
         const includeThumbnails = opts?.includeThumbnails ?? false;
-        if (!downloadDirectory) {
-            return Promise.reject(
-                new Error(
-                    "backup requires a downloadDirectory (pass one to " +
-                        "backup() or open the library with one)",
-                ),
-            );
-        }
         if ((includeOriginals || includeThumbnails) && !this.cache) {
             return Promise.reject(
                 new Error(

src/library/read.ts

@@ -12,18 +12,26 @@
 // plain records are the serializable surface, and `record()` returns one.
 //
 // A `Photo` also fetches its own bytes: `original()`, `thumbnail()`,
-// `content()` and `exif()` go through the on-disk content cache (issue #46),
-// and are the one place in this module that may touch the network. A library
-// opened without a content source leaves that cache absent, and those methods
-// then throw. `savePath` and `isLocal` look only at the disk.
+// `download()`, `content()`, `exif()` and the methods that each return one
+// field of `exif()` go through the on-disk content cache (issue #46), and are
+// the one place in this module that may touch the network. A library opened
+// without a content source leaves that cache absent, and those methods then
+// throw. `savePath` and `isLocal` look only at the disk and need no cache.
 
 import { readFile } from "node:fs/promises";
 
 import { readPhotoExif, type PhotoExif } from "../exif.js";
-import type { CollectionType, FileType } from "../model/types.js";
+import type { CollectionType, EnteFile, FileType } from "../model/types.js";
 import type { ContentOptions, ContentResult, PhotoContent } from "./content.js";
 import type { AlbumRecord, PhotoRecord, DerivedRecords } from "./records.js";
 
+// Where a photo's original is saved, and whether all of it is there. The
+// library answers both from the disk, with or without a content cache.
+export interface SavePathLookup {
+    savePath(file: EnteFile): string;
+    isLocal(file: EnteFile): boolean;
+}
+
 // Newest first, with fileID as a stable tiebreak so equal-timed files order
 // deterministically — the same order the record projection uses.
 const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
@@ -34,11 +42,22 @@ const byNewest = (a: PhotoRecord, b: PhotoRecord): number =>
 const byNewestAlbum = (a: AlbumRecord, b: AlbumRecord): number =>
     b.updationTime - a.updationTime || b.collectionID - a.collectionID;
 
+// A method for each `PhotoExif` field, named after it, taking the options
+// `exif()` takes and giving that field. `Photo` implements it, so the build's
+// type check fails when `PhotoExif` has a field `Photo` has no method for.
+type PhotoExifMethods = {
+    [K in keyof PhotoExif]-?: (opts?: ContentOptions) => Promise<PhotoExif[K]>;
+};
+
 // A single photo. Field access mirrors `PhotoRecord`; `record()` returns the
-// underlying plain record for callers that need the IPC-safe value.
-export class Photo {
+// underlying plain record for callers that need the IPC-safe value. `file` is
+// the membership the record is read from, so the save path carries the date of
+// `takenAt` and stays known after a refresh removes the file from the library.
+export class Photo implements PhotoExifMethods {
     constructor(
         private readonly rec: PhotoRecord,
+        private readonly file: EnteFile,
+        private readonly saves: SavePathLookup,
         private readonly cache?: PhotoContent,
     ) {}
 
@@ -89,20 +108,20 @@ export class Photo {
         return this.rec.isHidden;
     }
 
-    // Where `lib.backup()` stores the original in the library's download
-    // directory, whether or not it is there yet: for a live photo already
-    // stored, its image. For a live photo not yet stored, it carries the
-    // title's extension, and the backup may store the image under a different
-    // one. Undefined when the library has no download directory or no content
-    // cache.
-    get savePath(): string | undefined {
-        return this.cache?.savePath(this.rec.fileID);
+    // Where `download()` and `lib.backup()` put the original under the
+    // library's download directory, whether or not it is there yet:
+    // `YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID><ext>`. For a live photo
+    // already stored, its image. For a live photo not yet stored, it carries
+    // the title's extension, and the image may be stored under a different
+    // one.
+    get savePath(): string {
+        return this.saves.savePath(this.file);
     }
 
     // Whether the whole original is at `savePath`. A copy only in the cache
     // does not count.
     get isLocal(): boolean {
-        return this.cache?.isLocal(this.rec.fileID) ?? false;
+        return this.saves.isLocal(this.file);
     }
 
     record(): PhotoRecord {
@@ -111,12 +130,20 @@ export class Photo {
 
     // Fetch and cache the full-resolution original, returning its on-disk path
     // and byte length; for a live photo, its image's, and its video's path as
-    // `videoPath`. Served from the cache (or the backup download directory)
-    // when already present, otherwise fetched through the content pool.
+    // `videoPath`. Served from the cache (or the save path) when already
+    // present, otherwise fetched through the content pool.
     async original(opts?: ContentOptions): Promise<ContentResult> {
         return this.cacheOrThrow().original(this.rec.fileID, opts);
     }
 
+    // Put the original at `savePath` and return it there, as `original()`
+    // does. When it is already there, nothing is written. When the cache holds
+    // it, it is copied from there; otherwise it is fetched straight to
+    // `savePath`.
+    async download(): Promise<ContentResult> {
+        return this.cacheOrThrow().download(this.file);
+    }
+
     // As `original`, for the thumbnail, through the thumbnail pool.
     async thumbnail(opts?: ContentOptions): Promise<ContentResult> {
         return this.cacheOrThrow().thumbnail(this.rec.fileID, opts);
@@ -140,6 +167,65 @@ export class Photo {
         return readPhotoExif(await this.content(opts));
     }
 
+    // One field of `exif()` each, named and typed as in `PhotoExif`, and
+    // undefined when the file lacks it. Each call runs `exif()`, which reads
+    // the original again.
+    async make(opts?: ContentOptions): Promise<PhotoExif["make"]> {
+        return (await this.exif(opts)).make;
+    }
+    async model(opts?: ContentOptions): Promise<PhotoExif["model"]> {
+        return (await this.exif(opts)).model;
+    }
+    async lensModel(opts?: ContentOptions): Promise<PhotoExif["lensModel"]> {
+        return (await this.exif(opts)).lensModel;
+    }
+    async dateTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["dateTimeOriginal"]> {
+        return (await this.exif(opts)).dateTimeOriginal;
+    }
+    async offsetTimeOriginal(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["offsetTimeOriginal"]> {
+        return (await this.exif(opts)).offsetTimeOriginal;
+    }
+    async exposureTime(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["exposureTime"]> {
+        return (await this.exif(opts)).exposureTime;
+    }
+    async fNumber(opts?: ContentOptions): Promise<PhotoExif["fNumber"]> {
+        return (await this.exif(opts)).fNumber;
+    }
+    async iso(opts?: ContentOptions): Promise<PhotoExif["iso"]> {
+        return (await this.exif(opts)).iso;
+    }
+    async focalLength(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["focalLength"]> {
+        return (await this.exif(opts)).focalLength;
+    }
+    async orientation(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["orientation"]> {
+        return (await this.exif(opts)).orientation;
+    }
+    async gpsLatitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLatitude"]> {
+        return (await this.exif(opts)).gpsLatitude;
+    }
+    async gpsLongitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsLongitude"]> {
+        return (await this.exif(opts)).gpsLongitude;
+    }
+    async gpsAltitude(
+        opts?: ContentOptions,
+    ): Promise<PhotoExif["gpsAltitude"]> {
+        return (await this.exif(opts)).gpsAltitude;
+    }
+
     private cacheOrThrow(): PhotoContent {
         if (!this.cache) {
             throw new Error(
@@ -156,6 +242,7 @@ export class Album {
     constructor(
         private readonly rec: AlbumRecord,
         private readonly records: DerivedRecords,
+        private readonly saves: SavePathLookup,
         private readonly content?: PhotoContent,
     ) {}
 
@@ -190,7 +277,10 @@ export class Album {
         const out: Photo[] = [];
         for (const id of this.rec.fileIDs) {
             const p = this.records.photos.get(id);
-            if (p) out.push(new Photo(p, this.content));
+            const file = this.records.files.get(id);
+            if (p && file) {
+                out.push(new Photo(p, file, this.saves, this.content));
+            }
         }
         return out;
     }
@@ -253,18 +343,19 @@ export interface FreshReads {
 
 export const makeAlbumsAPI = (
     derive: () => DerivedRecords,
+    saves: SavePathLookup,
     content?: PhotoContent,
 ): AlbumsAPI => ({
     list: (): Album[] => {
         const records = derive();
         return [...records.albums.values()]
             .sort(byNewestAlbum)
-            .map((rec) => new Album(rec, records, content));
+            .map((rec) => new Album(rec, records, saves, content));
     },
     byID: ({ collectionID }): Album | undefined => {
         const records = derive();
         const rec = records.albums.get(collectionID);
-        return rec ? new Album(rec, records, content) : undefined;
+        return rec ? new Album(rec, records, saves, content) : undefined;
     },
     byName: ({ albumName }): Album | undefined => {
         const records = derive();
@@ -273,17 +364,20 @@ export const makeAlbumsAPI = (
         const match = [...records.albums.values()]
             .sort(byNewestAlbum)
             .find((rec) => rec.name === albumName);
-        return match ? new Album(match, records, content) : undefined;
+        return match ? new Album(match, records, saves, content) : undefined;
     },
 });
 
 export const makePhotosAPI = (
     derive: () => DerivedRecords,
+    saves: SavePathLookup,
     content?: PhotoContent,
 ): PhotosAPI => ({
     byID: ({ fileID }): Photo | undefined => {
-        const rec = derive().photos.get(fileID);
-        return rec ? new Photo(rec, content) : undefined;
+        const records = derive();
+        const rec = records.photos.get(fileID);
+        const file = records.files.get(fileID);
+        return rec && file ? new Photo(rec, file, saves, content) : undefined;
     },
     records: ({ fileIDs }): PhotoRecord[] => {
         const { photos } = derive();

src/library/records.ts

@@ -86,6 +86,10 @@ export interface LibraryChange {
 export interface DerivedRecords {
     albums: Map<number, AlbumRecord>;
     photos: Map<number, PhotoRecord>;
+    // The membership each photo's record is read from, for its `Photo`'s save
+    // path. It holds the file's key, so it stays in this process: no snapshot
+    // or change carries it.
+    files: Map<number, EnteFile>;
 }
 
 const asString = (v: unknown): string | undefined =>
@@ -101,18 +105,19 @@ const microsToMillis = (micros: number): number => Math.floor(micros / 1000);
 const byNewestPhoto = (a: PhotoRecord, b: PhotoRecord): number =>
     b.takenAt - a.takenAt || b.fileID - a.fileID;
 
-// Build one PhotoRecord from every membership of a file. The memberships share
-// the same underlying file, so metadata is read from a single representative
-// (the most recently synced, lowest collection id to break ties); `albumIDs`
-// gathers them all.
-const toPhotoRecord = (
-    fileID: number,
-    memberships: EnteFile[],
-): PhotoRecord => {
-    const albumIDs = memberships
-        .map((m) => m.collectionID)
-        .sort((a, b) => a - b);
-    const rep = memberships.reduce((best, m) =>
+// A photo's `takenAt` in milliseconds: `pubMagicMetadata.editedTime` when the
+// user edited the date, else basic-metadata `creationTime`.
+export const takenAtOf = (file: EnteFile): number =>
+    microsToMillis(
+        asNumber(file.pubMagicMetadata?.editedTime) ??
+            file.metadata.creationTime,
+    );
+
+// The membership a file's record is read from: the most recently synced, lowest
+// collection id to break ties. Whatever dates a file's save path takes this
+// membership too, so the path always carries the record's `takenAt`.
+export const representative = (memberships: EnteFile[]): EnteFile =>
+    memberships.reduce((best, m) =>
         m.updationTime > best.updationTime ||
         (m.updationTime === best.updationTime &&
             m.collectionID < best.collectionID)
@@ -120,17 +125,28 @@ const toPhotoRecord = (
             : best,
     );
 
+// Build one PhotoRecord from every membership of a file. The memberships share
+// the same underlying file, so metadata is read from a single representative;
+// `albumIDs` gathers them all.
+const toPhotoRecord = (
+    fileID: number,
+    memberships: EnteFile[],
+): PhotoRecord => {
+    const albumIDs = memberships
+        .map((m) => m.collectionID)
+        .sort((a, b) => a - b);
+    const rep = representative(memberships);
+
     const pub = rep.pubMagicMetadata ?? {};
     const priv = rep.magicMetadata ?? {};
 
-    const takenAtMicros = asNumber(pub.editedTime) ?? rep.metadata.creationTime;
     const visibility = asNumber(priv.visibility);
 
     const record: PhotoRecord = {
         fileID,
         albumIDs,
         title: asString(pub.editedName) ?? rep.metadata.title,
-        takenAt: microsToMillis(takenAtMicros),
+        takenAt: takenAtOf(rep),
         modifiedAt: microsToMillis(rep.metadata.modificationTime),
         fileType: rep.metadata.fileType,
         isArchived: visibility === VISIBILITY_ARCHIVED,
@@ -198,6 +214,7 @@ export const deriveRecords = (
     }
 
     const photos = new Map<number, PhotoRecord>();
+    const photoFiles = new Map<number, EnteFile>();
     const takenAtByFile = new Map<number, number>();
     for (const [fileID, memberships] of byFileID) {
         const record = toPhotoRecord(fileID, memberships);
@@ -209,6 +226,7 @@ export const deriveRecords = (
                 record.thumbnailPath = paths.thumbnailPath;
         }
         photos.set(fileID, record);
+        photoFiles.set(fileID, representative(memberships));
         takenAtByFile.set(fileID, record.takenAt);
     }
 
@@ -217,7 +235,7 @@ export const deriveRecords = (
         albums.set(c.id, toAlbumRecord(c, files, takenAtByFile));
     }
 
-    return { albums, photos };
+    return { albums, photos, files: photoFiles };
 };
 
 // Sorted, GUI-ready arrays: albums newest updated first, photos newest first.

src/library/store.ts

@@ -16,6 +16,7 @@ import { dirname } from "node:path";
 
 import { writeAtomic } from "../download/index.js";
 import type { Collection, EnteFile, Microseconds } from "../model/types.js";
+import { representative } from "./records.js";
 
 // Bumped only when the on-disk shape changes incompatibly. A file written
 // under a different version is discarded on load (see `load`): re-fetching
@@ -179,14 +180,16 @@ export class MetadataStore {
         return this.files.get(fileKey(collectionID, fileID));
     }
 
-    // Any membership of a file, or undefined. Every membership re-wraps the
-    // same underlying content key, so any one is enough to fetch the bytes;
-    // the content cache resolves a fileID to a file this way.
+    // The membership of a file its record is read from (`representative`), or
+    // undefined. Any membership could fetch the bytes, but the content cache
+    // resolves a fileID to a file this way so that it dates the save path
+    // from the same membership as `photo.savePath`.
     getFileByID(fileID: number): EnteFile | undefined {
+        const memberships: EnteFile[] = [];
         for (const file of this.files.values()) {
-            if (file.id === fileID) return file;
+            if (file.id === fileID) memberships.push(file);
         }
-        return undefined;
+        return memberships.length > 0 ? representative(memberships) : undefined;
     }
 
     listFiles(collectionID: number): EnteFile[] {

test/cli/backup.test.ts

@@ -1,16 +1,16 @@
 /**
  * Tests for the `quak backup` logic, now built on the library API (issue #51).
  *
- * `lib.backup({ downloadDirectory })` refreshes the library, fetches each
- * pending file's original through the content cache/pools, and materialises the
- * unchanged on-disk layout:
+ * `lib.backup({ downloadDirectory })` refreshes the library, puts each pending
+ * file's original at its save path through the content cache/pools, and
+ * materialises the on-disk layout:
  *
  *     <downloadDirectory>/
- *         originals/
- *             <fileID>.<ext>          the decrypted bytes ("present means complete")
- *             <fileID>.json           per-file metadata sidecar (rebuilt each run)
+ *         YYYY/YYYY-MM/YYYY-MM-DD/
+ *             YYYY-MM-DD.<fileID>.<ext>   the decrypted bytes ("present means complete")
+ *             YYYY-MM-DD.<fileID>.json    per-file metadata sidecar (rebuilt each run)
  *         collections/
- *             <name>/<title>          symlink into ../originals (rebuilt each run)
+ *             <name>/<title>          symlink to the original (rebuilt each run)
  *             <name>.json             per-collection metadata (rebuilt each run)
  *         failures.json               durable ledger of unresolved failures
  *
@@ -94,6 +94,18 @@ const USER_ID = 42;
 // Decrypted-byte length each stub original writes, keyed by fileID.
 const SIZE_BY_ID: Record<number, number> = { 100: 3000, 101: 2000, 200: 1500 };
 
+// Every file is taken at noon local time on 2026-03-01, in microseconds as Ente
+// stores times, so the machine's time zone cannot move it to another day. Its
+// original is saved in the folder `DAY`, named `2026-03-01.<fileID>.<ext>`.
+const TAKEN = new Date(2026, 2, 1, 12).getTime() * 1000;
+const DAY = join("2026", "2026-03", "2026-03-01");
+
+// Where the backup in `outDir` saves `name` (`<fileID>.<ext>`), and the target
+// of an album folder's symlink to it.
+const saved = (outDir: string, name: string): string =>
+    join(outDir, DAY, `2026-03-01.${name}`);
+const linkTo = (name: string): string => `../../${DAY}/2026-03-01.${name}`;
+
 const collection = (id: number, name: string): Collection => ({
     id,
     ownerID: USER_ID,
@@ -112,7 +124,7 @@ const file = (id: number, collectionID: number, title: string): EnteFile => ({
     metadata: {
         title,
         fileType: "image",
-        creationTime: 1,
+        creationTime: TAKEN,
         modificationTime: 1,
     },
     file: { decryptionHeader: "aGVhZGVy" },
@@ -253,7 +265,11 @@ describe("lib.backup", () => {
     it("throws before any network when no downloadDirectory is given", async () => {
         const source = stubSource();
         const lib = await openLibrary(source);
-        await expect(lib.backup()).rejects.toThrow(/downloadDirectory/i);
+        // The library always has a download directory, so only an empty one
+        // given to backup() reaches runBackup as none.
+        await expect(lib.backup({ downloadDirectory: "" })).rejects.toThrow(
+            /downloadDirectory/i,
+        );
         expect(source.originalCalls).toBe(0);
         lib.close();
     });
@@ -271,28 +287,22 @@ describe("lib.backup", () => {
         expect(result.failed).toBe(0);
         expect(result.errors).toEqual([]);
 
-        // Originals under originals/<fileID>.<ext>.
-        expect(readFileSync(join(outDir, "originals", "100.jpg")).length).toBe(
-            3000,
-        );
-        expect(readFileSync(join(outDir, "originals", "101.jpg")).length).toBe(
-            2000,
-        );
-        expect(readFileSync(join(outDir, "originals", "200.png")).length).toBe(
-            1500,
-        );
+        // Originals at YYYY/YYYY-MM/YYYY-MM-DD/YYYY-MM-DD.<fileID>.<ext>.
+        expect(readFileSync(saved(outDir, "100.jpg")).length).toBe(3000);
+        expect(readFileSync(saved(outDir, "101.jpg")).length).toBe(2000);
+        expect(readFileSync(saved(outDir, "200.png")).length).toBe(1500);
 
         // Per-file metadata sidecar.
         const sidecar = JSON.parse(
-            readFileSync(join(outDir, "originals", "100.json"), "utf-8"),
+            readFileSync(saved(outDir, "100.json"), "utf-8"),
         );
         expect(sidecar.id).toBe(100);
         expect(sidecar.metadata.title).toBe("beach.jpg");
 
-        // Collection dirs contain symlinks into ../originals.
+        // Collection dirs contain symlinks into the date folders.
         const beach = join(outDir, "collections", "Vacation", "beach.jpg");
         expect(lstatSync(beach).isSymbolicLink()).toBe(true);
-        expect(readlinkSync(beach)).toContain("originals");
+        expect(readlinkSync(beach)).toContain(DAY);
         expect(readFileSync(beach).length).toBe(3000);
 
         // Per-collection metadata JSON.
@@ -316,7 +326,7 @@ describe("lib.backup", () => {
 
         expect(result.failed).toBe(0);
         // The title has no usable extension, so the original is `.bin`.
-        expect(existsSync(join(outDir, "originals", "300.bin"))).toBe(true);
+        expect(existsSync(saved(outDir, "300.bin"))).toBe(true);
         const link = join(
             outDir,
             "collections",
@@ -366,9 +376,9 @@ describe("lib.backup", () => {
         expect(result.errors[0]!.title).toBe("sunset.jpg");
 
         // The two good files are on disk; the failed one is not.
-        expect(existsSync(join(outDir, "originals", "100.jpg"))).toBe(true);
-        expect(existsSync(join(outDir, "originals", "200.png"))).toBe(true);
-        expect(existsSync(join(outDir, "originals", "101.jpg"))).toBe(false);
+        expect(existsSync(saved(outDir, "100.jpg"))).toBe(true);
+        expect(existsSync(saved(outDir, "200.png"))).toBe(true);
+        expect(existsSync(saved(outDir, "101.jpg"))).toBe(false);
         expect(
             existsSync(join(outDir, "collections", "Vacation", "sunset.jpg")),
         ).toBe(false);
@@ -403,7 +413,7 @@ describe("lib.backup", () => {
         const r3 = await lib.backup({ downloadDirectory: outDir });
         expect(r3.failed).toBe(0);
         expect(r3.skipped).toBe(2);
-        expect(existsSync(join(outDir, "originals", "101.jpg"))).toBe(true);
+        expect(existsSync(saved(outDir, "101.jpg"))).toBe(true);
         // A ledger with no remaining failures is removed.
         expect(existsSync(join(outDir, "failures.json"))).toBe(false);
         lib.close();
@@ -423,8 +433,8 @@ describe("lib.backup", () => {
         const result = await lib.backup({ downloadDirectory: outDir });
 
         // Every original still downloads despite the symlink failure.
-        expect(existsSync(join(outDir, "originals", "100.jpg"))).toBe(true);
-        expect(existsSync(join(outDir, "originals", "200.png"))).toBe(true);
+        expect(existsSync(saved(outDir, "100.jpg"))).toBe(true);
+        expect(existsSync(saved(outDir, "200.png"))).toBe(true);
         // The other symlinks are still built.
         expect(
             lstatSync(
@@ -454,7 +464,7 @@ describe("lib.backup", () => {
         await lib.backup({ downloadDirectory: outDir });
 
         // Corrupt a sidecar and delete a symlink between runs.
-        writeFileSync(join(outDir, "originals", "100.json"), "not json");
+        writeFileSync(saved(outDir, "100.json"), "not json");
         rmSync(join(outDir, "collections", "Vacation", "beach.jpg"));
 
         const result = await lib.backup({ downloadDirectory: outDir });
@@ -462,7 +472,7 @@ describe("lib.backup", () => {
 
         // The derived views are repaired from the model.
         const sidecar = JSON.parse(
-            readFileSync(join(outDir, "originals", "100.json"), "utf-8"),
+            readFileSync(saved(outDir, "100.json"), "utf-8"),
         );
         expect(sidecar.metadata.title).toBe("beach.jpg");
         expect(
@@ -485,8 +495,8 @@ describe("lib.backup", () => {
 
         expect(result.totalFiles).toBe(1);
         expect(result.downloaded).toBe(1);
-        expect(existsSync(join(outDir, "originals", "200.png"))).toBe(true);
-        expect(existsSync(join(outDir, "originals", "100.jpg"))).toBe(false);
+        expect(existsSync(saved(outDir, "200.png"))).toBe(true);
+        expect(existsSync(saved(outDir, "100.jpg"))).toBe(false);
         expect(existsSync(join(outDir, "collections", "Work.json"))).toBe(true);
         expect(existsSync(join(outDir, "collections", "Vacation.json"))).toBe(
             false,
@@ -530,7 +540,7 @@ describe("lib.backup", () => {
 
         expect(result.totalFiles).toBe(1);
         expect(result.failed).toBe(0);
-        expect(existsSync(join(outDir, "originals", "200.png"))).toBe(true);
+        expect(existsSync(saved(outDir, "200.png"))).toBe(true);
         expect(existsSync(join(outDir, "failures.json"))).toBe(false);
         lib.close();
     });
@@ -572,7 +582,7 @@ describe("lib.backup", () => {
     it("fetches each original once and writes it only into the backup", async () => {
         // A backup of a 500 GB account must write 500 GB, not a copy in the
         // cache as well: an original fetched for the backup goes straight
-        // into its originals/, and the cache records it there.
+        // to its save path, and the cache records it there.
         const source = stubSource();
         const lib = await openLibrary(source);
         const outDir = join(root, "backup");
@@ -582,23 +592,78 @@ describe("lib.backup", () => {
         expect(result.downloaded).toBe(3);
         expect(source.originalCalls).toBe(3);
         expect(readdirSync(join(root, "cache", "originals"))).toEqual([]);
-        const stored = readdirSync(join(outDir, "originals")).filter(
+        const stored = readdirSync(join(outDir, DAY)).filter(
             (name) => !name.endsWith(".json"),
         );
-        expect(stored.sort()).toEqual(["100.jpg", "101.jpg", "200.png"]);
+        expect(stored.sort()).toEqual([
+            "2026-03-01.100.jpg",
+            "2026-03-01.101.jpg",
+            "2026-03-01.200.png",
+        ]);
         // The cache counts the backup's copy as present: reading the
         // original afterwards fetches nothing and answers with that copy.
         const read = await lib.photos.byID({ fileID: 100 })!.original();
-        expect(read.path).toBe(join(outDir, "originals", "100.jpg"));
+        expect(read.path).toBe(saved(outDir, "100.jpg"));
         expect(source.originalCalls).toBe(3);
         await lib.close();
     });
 
+    it("saves a file in two albums at its photo's save path and links it from both", async () => {
+        // The date edited in Ente has reached Work's copy, synced later, but
+        // Vacation's copy still has an earlier edit.
+        const older = file(100, 1, "beach.jpg");
+        older.pubMagicMetadata = {
+            editedTime: new Date(2026, 1, 1, 12).getTime() * 1000,
+        };
+        const newer = file(100, 2, "beach.jpg");
+        newer.updationTime = 2;
+        newer.pubMagicMetadata = {
+            editedTime: new Date(2026, 3, 15, 12).getTime() * 1000,
+        };
+        class SharedFileClient extends MockClient {
+            override async filesSince(args: {
+                collectionID: number;
+            }): Promise<FilesPage> {
+                const files = [args.collectionID === 1 ? older : newer];
+                return { files, deleted: [], cursor: 1 };
+            }
+        }
+        const outDir = join(root, "backup");
+        const lib = await Library.open({
+            client: new SharedFileClient(),
+            cacheDirectory: join(root, "cache"),
+            downloadDirectory: outDir,
+            contentSource: stubSource(),
+            refreshIntervalSeconds: 3600,
+            precacheThumbnails: false,
+            precacheOriginals: false,
+        });
+        const photo = lib.photos.byID({ fileID: 100 })!;
+
+        const result = await lib.backup();
+
+        expect(result.totalFiles).toBe(1);
+        expect(result.downloaded).toBe(1);
+        expect(result.failed).toBe(0);
+        expect(photo.savePath).toBe(
+            join(outDir, "2026", "2026-04", "2026-04-15", "2026-04-15.100.jpg"),
+        );
+        expect(photo.isLocal).toBe(true);
+        expect(existsSync(join(outDir, "2026", "2026-02"))).toBe(false);
+        const target = "../../2026/2026-04/2026-04-15/2026-04-15.100.jpg";
+        for (const album of ["Vacation", "Work"]) {
+            expect(
+                readlinkSync(join(outDir, "collections", album, "beach.jpg")),
+            ).toBe(target);
+        }
+        await lib.close();
+    });
+
     it("fsyncs an original copied from the cache before the rename and its directory after", async () => {
         const lib = await openLibrary(stubSource());
         const outDir = join(root, "backup");
-        const originals = join(outDir, "originals");
-        const dest = join(originals, "100.jpg");
+        const day = join(outDir, DAY);
+        const dest = saved(outDir, "100.jpg");
         // Only an original already in the cache is copied into the backup;
         // one fetched for the backup is written there by the download writer.
         await lib.photos.byID({ fileID: 100 })!.original();
@@ -609,34 +674,50 @@ describe("lib.backup", () => {
         const at = fsEvents.indexOf(`rename:${dest}`);
         expect(at).toBeGreaterThan(0);
         expect(fsEvents[at - 1]).toMatch(
-            /^sync:.*\/\.quak-backup-100\.jpg-\d+-[0-9a-z]*\.tmp$/,
+            /^sync:.*\/\.quak-backup-2026-03-01\.100\.jpg-\d+-[0-9a-z]*\.tmp$/,
         );
-        expect(fsEvents[at + 1]).toBe(`sync:${originals}`);
+        expect(fsEvents[at + 1]).toBe(`sync:${day}`);
         lib.close();
     });
 
     it("removes temp files left by a killed backup but not those of one still running", async () => {
         const outDir = join(root, "backup");
-        const originals = join(outDir, "originals");
-        mkdirSync(originals, { recursive: true });
+        const day = join(outDir, DAY);
+        mkdirSync(day, { recursive: true });
         // A child that has already exited: its process ID is not running.
         const exitedPID = spawnSync(process.execPath, ["-e", ""]).pid;
-        const leftover = `.quak-backup-100.jpg-${exitedPID}-abc123.tmp`;
+        const leftover = `.quak-backup-2026-03-01.100.jpg-${exitedPID}-abc123.tmp`;
         // This test's own process stands in for a backup running at the same
         // time.
-        const inProgress = `.quak-backup-101.jpg-${process.pid}-def456.tmp`;
-        writeFileSync(join(originals, leftover), "partial");
-        writeFileSync(join(originals, inProgress), "partial");
+        const inProgress = `.quak-backup-2026-03-01.101.jpg-${process.pid}-def456.tmp`;
+        writeFileSync(join(day, leftover), "partial");
+        writeFileSync(join(day, inProgress), "partial");
         const lib = await openLibrary(stubSource());
 
         await lib.backup({ downloadDirectory: outDir });
 
-        const names = readdirSync(originals);
+        const names = readdirSync(day);
         expect(names).not.toContain(leftover);
         expect(names).toContain(inProgress);
         lib.close();
     });
 
+    it("removes temp files left in a date folder no file in the backup is saved in", async () => {
+        const outDir = join(root, "backup");
+        // As for a file since deleted, or given another date, after a run was
+        // killed while writing it.
+        const otherDay = join(outDir, "2025", "2025-01", "2025-01-02");
+        mkdirSync(otherDay, { recursive: true });
+        const exitedPID = spawnSync(process.execPath, ["-e", ""]).pid;
+        writeFileSync(join(otherDay, `.quak-${exitedPID}-abc123.tmp`), "x");
+        const lib = await openLibrary(stubSource());
+
+        await lib.backup({ downloadDirectory: outDir });
+
+        expect(readdirSync(otherDay)).toEqual([]);
+        lib.close();
+    });
+
     it("removes leftover temp files in thumbnails/ but not those of a backup still running", async () => {
         const outDir = join(root, "backup");
         const thumbnails = join(outDir, "thumbnails");
@@ -709,7 +790,7 @@ describe("the refresh before a backup", () => {
         const result = await backup;
 
         expect(result.totalFiles).toBe(4);
-        expect(existsSync(join(outDir, "originals", "300.jpg"))).toBe(true);
+        expect(existsSync(saved(outDir, "300.jpg"))).toBe(true);
         await lib.close();
     });
 
@@ -728,7 +809,7 @@ describe("the refresh before a backup", () => {
 
         expect(source.originalCalls).toBe(0);
         expect(readFileSync(ledgerPath, "utf-8")).toBe(ledgerBefore);
-        expect(existsSync(join(outDir, "originals"))).toBe(false);
+        expect(existsSync(join(outDir, DAY))).toBe(false);
         await lib.close();
     });
 
@@ -819,13 +900,13 @@ describe("backup album folders", () => {
         expect(result.failed).toBe(0);
         expect(tree(outDir)).toEqual([
             "Trip (10)/",
-            "Trip (10)/IMG_0001 (1).JPG -> ../../originals/1.JPG",
-            "Trip (10)/IMG_0001 (2).JPG -> ../../originals/2.JPG",
-            "Trip (10)/img_0001 (4).jpg -> ../../originals/4.jpg",
-            "Trip (10)/other.jpg -> ../../originals/3.jpg",
+            `Trip (10)/IMG_0001 (1).JPG -> ${linkTo("1.JPG")}`,
+            `Trip (10)/IMG_0001 (2).JPG -> ${linkTo("2.JPG")}`,
+            `Trip (10)/img_0001 (4).jpg -> ${linkTo("4.jpg")}`,
+            `Trip (10)/other.jpg -> ${linkTo("3.jpg")}`,
             "Trip (10).json",
             "Trip (11)/",
-            "Trip (11)/other.jpg -> ../../originals/3.jpg",
+            `Trip (11)/other.jpg -> ${linkTo("3.jpg")}`,
             "Trip (11).json",
         ]);
         expect(albumID(outDir, "Trip (10).json")).toBe(10);
@@ -858,14 +939,14 @@ describe("backup album folders", () => {
         expect(result.failed).toBe(0);
         expect(tree(outDir)).toEqual([
             "Trip (10)/",
-            "Trip (10)/IMG (6) (5).JPG -> ../../originals/5.JPG",
-            "Trip (10)/IMG (6).JPG -> ../../originals/6.JPG",
-            "Trip (10)/IMG (7).JPG -> ../../originals/7.JPG",
+            `Trip (10)/IMG (6) (5).JPG -> ${linkTo("5.JPG")}`,
+            `Trip (10)/IMG (6).JPG -> ${linkTo("6.JPG")}`,
+            `Trip (10)/IMG (7).JPG -> ${linkTo("7.JPG")}`,
             "Trip (10).json",
             "Trip (11)/",
-            "Trip (11)/a.jpg -> ../../originals/8.jpg",
+            `Trip (11)/a.jpg -> ${linkTo("8.jpg")}`,
             "Trip (11) (12)/",
-            "Trip (11) (12)/b.jpg -> ../../originals/9.jpg",
+            `Trip (11) (12)/b.jpg -> ${linkTo("9.jpg")}`,
             "Trip (11) (12).json",
             "Trip (11).json",
         ]);
@@ -931,13 +1012,13 @@ describe("backup album folders", () => {
         expect(scoped.failed).toBe(0);
         expect(before).toEqual([
             "Trip (10)/",
-            "Trip (10)/a.jpg -> ../../originals/1.jpg",
+            `Trip (10)/a.jpg -> ${linkTo("1.jpg")}`,
             "Trip (10).json",
             "Work/",
-            "Work/c.jpg -> ../../originals/3.jpg",
+            `Work/c.jpg -> ${linkTo("3.jpg")}`,
             "Work.json",
             "trip (11)/",
-            "trip (11)/b.jpg -> ../../originals/2.jpg",
+            `trip (11)/b.jpg -> ${linkTo("2.jpg")}`,
             "trip (11).json",
         ]);
         expect(tree(outDir)).toEqual(before);
@@ -990,13 +1071,13 @@ describe("backup album folders", () => {
             "Mine/",
             "Mine/keep.txt",
             "Office/",
-            "Office/a.jpg -> ../../originals/5.jpg",
+            `Office/a.jpg -> ${linkTo("5.jpg")}`,
             "Office.json",
             "Trip/",
-            "Trip/IMG_0001.JPG -> ../../originals/1.JPG",
+            `Trip/IMG_0001.JPG -> ${linkTo("1.JPG")}`,
             "Trip/mine -> ../elsewhere",
             "Trip/notes.txt",
-            "Trip/other.jpg -> ../../originals/3.jpg",
+            `Trip/other.jpg -> ${linkTo("3.jpg")}`,
             "Trip.json",
             "Work/",
             "Work/keep.txt",
@@ -1005,7 +1086,7 @@ describe("backup album folders", () => {
     });
 
     // One album backed up, then a folder the user made beside it holding a
-    // symlink into originals/, with `json` (if given) as its sibling JSON.
+    // symlink to an original, with `json` (if given) as its sibling JSON.
     const backupWithUserFolder = async (
         json: string | undefined,
     ): Promise<{ outDir: string; failed: number }> => {
@@ -1019,10 +1100,7 @@ describe("backup album folders", () => {
         await runBackup(lib, { downloadDirectory: outDir });
         const collectionsDir = join(outDir, "collections");
         mkdirSync(join(collectionsDir, "Mine"));
-        symlinkSync(
-            "../../originals/1.jpg",
-            join(collectionsDir, "Mine", "a.jpg"),
-        );
+        symlinkSync(linkTo("1.jpg"), join(collectionsDir, "Mine", "a.jpg"));
         if (json !== undefined) {
             writeFileSync(join(collectionsDir, "Mine.json"), json);
         }
@@ -1036,9 +1114,9 @@ describe("backup album folders", () => {
         expect(failed).toBe(0);
         expect(tree(outDir)).toEqual([
             "Mine/",
-            "Mine/a.jpg -> ../../originals/1.jpg",
+            `Mine/a.jpg -> ${linkTo("1.jpg")}`,
             "Trip/",
-            "Trip/a.jpg -> ../../originals/1.jpg",
+            `Trip/a.jpg -> ${linkTo("1.jpg")}`,
             "Trip.json",
         ]);
     });
@@ -1050,10 +1128,10 @@ describe("backup album folders", () => {
         expect(failed).toBe(0);
         expect(tree(outDir)).toEqual([
             "Mine/",
-            "Mine/a.jpg -> ../../originals/1.jpg",
+            `Mine/a.jpg -> ${linkTo("1.jpg")}`,
             "Mine.json",
             "Trip/",
-            "Trip/a.jpg -> ../../originals/1.jpg",
+            `Trip/a.jpg -> ${linkTo("1.jpg")}`,
             "Trip.json",
         ]);
         expect(
@@ -1087,23 +1165,16 @@ describe("backup of live photos", () => {
     const open = (files: EnteFile[], bodies: Map<number, Uint8Array>) =>
         openLibrary(cdnSource(bodies), new TripClient(files));
 
-    // What an earlier version stored for live photo 500: the ZIP under the
-    // image's name, and its link.
-    const earlierZIP = (outDir: string): void => {
-        mkdirSync(join(outDir, "originals"), { recursive: true });
-        mkdirSync(join(outDir, "collections", "Trip"), { recursive: true });
-        writeFileSync(join(outDir, "originals", "500.HEIC"), livePhotoZip());
-        symlinkSync(
-            "../../originals/500.HEIC",
-            join(outDir, "collections", "Trip", "IMG_0500.HEIC"),
-        );
-    };
-
-    const stored = ["500.heic", "500.json", "500.livephoto.json", "500.mov"];
+    const stored = [
+        "2026-03-01.500.heic",
+        "2026-03-01.500.json",
+        "2026-03-01.500.livephoto.json",
+        "2026-03-01.500.mov",
+    ];
     const linked = [
         "Trip/",
-        "Trip/IMG_0500.heic -> ../../originals/500.heic",
-        "Trip/IMG_0500.mov -> ../../originals/500.mov",
+        `Trip/IMG_0500.heic -> ${linkTo("500.heic")}`,
+        `Trip/IMG_0500.mov -> ${linkTo("500.mov")}`,
         "Trip.json",
     ];
 
@@ -1113,16 +1184,15 @@ describe("backup of live photos", () => {
         );
         const lib = await open([live], new Map([[500, body]]));
         const outDir = join(root, "backup");
-        const originals = join(outDir, "originals");
 
         const result = await lib.backup({ downloadDirectory: outDir });
 
         expect(result).toMatchObject({ downloaded: 1, failed: 0 });
-        expect(readdirSync(originals).sort()).toEqual(stored);
-        expect(readFileSync(join(originals, "500.heic"))).toEqual(
+        expect(readdirSync(join(outDir, DAY)).sort()).toEqual(stored);
+        expect(readFileSync(saved(outDir, "500.heic"))).toEqual(
             Buffer.from(IMAGE),
         );
-        expect(readFileSync(join(originals, "500.mov"))).toEqual(
+        expect(readFileSync(saved(outDir, "500.mov"))).toEqual(
             Buffer.from(VIDEO),
         );
         expect(tree(outDir)).toEqual(linked);
@@ -1149,39 +1219,22 @@ describe("backup of live photos", () => {
 
         expect(tree(outDir)).toEqual([
             "Trip/",
-            "Trip/IMG_0001 (500).heic -> ../../originals/500.heic",
-            "Trip/IMG_0001 (500).mov -> ../../originals/500.mov",
-            "Trip/IMG_0001 (501).heic -> ../../originals/501.heic",
-            "Trip/IMG_0001 (501).mov -> ../../originals/501.mov",
+            `Trip/IMG_0001 (500).heic -> ${linkTo("500.heic")}`,
+            `Trip/IMG_0001 (500).mov -> ${linkTo("500.mov")}`,
+            `Trip/IMG_0001 (501).heic -> ${linkTo("501.heic")}`,
+            `Trip/IMG_0001 (501).mov -> ${linkTo("501.mov")}`,
             "Trip.json",
         ]);
         await lib.close();
     });
 
-    it("replaces the ZIP an earlier version stored, and its link", async () => {
-        const { file: live, body } = await asLivePhoto(
-            file(500, 10, "IMG_0500.HEIC"),
-        );
-        const outDir = join(root, "backup");
-        earlierZIP(outDir);
-        const lib = await open([live], new Map([[500, body]]));
-
-        const result = await lib.backup({ downloadDirectory: outDir });
-
-        expect(result).toMatchObject({ downloaded: 1, failed: 0 });
-        expect(readdirSync(join(outDir, "originals")).sort()).toEqual(stored);
-        expect(tree(outDir)).toEqual(linked);
-        await lib.close();
-    });
-
-    it("stores nothing for a live photo that fails its hash, and keeps what was there", async () => {
+    it("stores nothing for a live photo that fails its hash", async () => {
         const { file: live, body } = await asLivePhoto(
             file(500, 10, "IMG_0500.HEIC"),
             livePhotoZip(),
             "not:the recorded hash",
         );
         const outDir = join(root, "backup");
-        earlierZIP(outDir);
         const lib = await open([live], new Map([[500, body]]));
 
         const result = await lib.backup({ downloadDirectory: outDir });
@@ -1189,12 +1242,8 @@ describe("backup of live photos", () => {
         expect(result).toMatchObject({ downloaded: 0, failed: 1 });
         expect(result.errors.map((e) => e.fileID)).toEqual([500]);
         expect(Object.keys(readLedger(outDir).files)).toEqual(["500"]);
-        expect(readdirSync(join(outDir, "originals"))).toEqual(["500.HEIC"]);
-        expect(tree(outDir)).toEqual([
-            "Trip/",
-            "Trip/IMG_0500.HEIC -> ../../originals/500.HEIC",
-            "Trip.json",
-        ]);
+        expect(readdirSync(join(outDir, DAY))).toEqual([]);
+        expect(tree(outDir)).toEqual(["Trip/", "Trip.json"]);
         await lib.close();
     });
 
@@ -1209,8 +1258,8 @@ describe("backup of live photos", () => {
         const result = await lib.backup({ downloadDirectory: outDir });
 
         expect(result).toMatchObject({ downloaded: 1, failed: 0 });
-        expect(readdirSync(join(outDir, "originals")).sort()).toEqual(stored);
-        expect(readFileSync(join(outDir, "originals", "500.mov"))).toEqual(
+        expect(readdirSync(join(outDir, DAY)).sort()).toEqual(stored);
+        expect(readFileSync(saved(outDir, "500.mov"))).toEqual(
             Buffer.from(VIDEO),
         );
         expect(tree(outDir)).toEqual(linked);
@@ -1219,23 +1268,6 @@ describe("backup of live photos", () => {
         await lib.close();
     });
 
-    it("replaces an earlier ZIP and its link with the image and video the cache holds", async () => {
-        const { file: live, body } = await asLivePhoto(
-            file(500, 10, "IMG_0500.HEIC"),
-        );
-        const lib = await open([live], new Map([[500, body]]));
-        await lib.photos.byID({ fileID: 500 })!.original();
-        const outDir = join(root, "backup");
-        earlierZIP(outDir);
-
-        const result = await lib.backup({ downloadDirectory: outDir });
-
-        expect(result).toMatchObject({ downloaded: 1, failed: 0 });
-        expect(readdirSync(join(outDir, "originals")).sort()).toEqual(stored);
-        expect(tree(outDir)).toEqual(linked);
-        await lib.close();
-    });
-
     it.each(["missing", "empty"])(
         "fetches a live photo again when the video its JSON file names is %s",
         async (state) => {
@@ -1245,7 +1277,7 @@ describe("backup of live photos", () => {
             const lib = await open([live], new Map([[500, body]]));
             const outDir = join(root, "backup");
             await lib.backup({ downloadDirectory: outDir });
-            const video = join(outDir, "originals", "500.mov");
+            const video = saved(outDir, "500.mov");
             if (state === "missing") rmSync(video);
             else writeFileSync(video, "");
 
@@ -1271,7 +1303,7 @@ describe("backup of live photos", () => {
             const lib = await open([live], new Map([[500, body]]));
             const outDir = join(root, "backup");
             await lib.backup({ downloadDirectory: outDir });
-            const image = join(outDir, "originals", "500.heic");
+            const image = saved(outDir, "500.heic");
             if (state === "missing") rmSync(image);
             else writeFileSync(image, "");
 
@@ -1310,8 +1342,8 @@ describe("backup of live photos", () => {
         const read = await reader.photos.byID({ fileID: 500 })!.original();
 
         expect(read).toEqual({
-            path: join(outDir, "originals", "500.heic"),
-            videoPath: join(outDir, "originals", "500.mov"),
+            path: saved(outDir, "500.heic"),
+            videoPath: saved(outDir, "500.mov"),
             bytes: IMAGE.length,
         });
         await reader.close();

test/cli/commands.test.ts

@@ -757,7 +757,7 @@ describe("backup", () => {
         expect(code).toBe(1);
         expect(runText).toBe("quak: HTTP 401 from server\n");
         expect(stderr.text).toBe("Starting backup...\nRefreshing library...\n");
-        expect(existsSync(join(dir, "originals"))).toBe(false);
+        expect(existsSync(dir)).toBe(false);
     });
 });
 

test/library/content-eviction.test.ts

@@ -142,6 +142,7 @@ const buildCache = (args: {
         pools: new RequestPools(),
         source,
         cacheDirectory: cacheDir,
+        downloadDirectory: join(root, "photos"),
         getFile: (id) => byID.get(id),
         statfs: args.statfs,
         cacheOriginalsMaxBytes: args.cacheOriginalsMaxBytes,

test/library/content-library.test.ts

@@ -6,16 +6,18 @@
  * `Photo` objects that fetch through it, `lib.thumbnails.ensure` drives it, and
  * a cached path shows up on the projected record. A library opened without a
  * content source leaves those methods throwing rather than silently doing
- * nothing. It also covers a `Photo`'s `savePath`, `isLocal`, `content()` and
- * `exif()`.
+ * nothing. It also covers a `Photo`'s `savePath`, `isLocal`, `download()`,
+ * `content()`, `exif()` and the methods that each return one field of `exif()`.
  */
 
-import { describe, it, expect, beforeEach, afterEach } from "vitest";
+import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 import {
     mkdtempSync,
     readdirSync,
+    readFileSync,
     rmSync,
     existsSync,
+    statSync,
     writeFileSync,
 } from "node:fs";
 import { tmpdir } from "node:os";
@@ -38,6 +40,12 @@ import {
 
 const USER_ID = 7;
 
+// Every file is taken at noon local time on 2026-03-01, in microseconds as Ente
+// stores times, so the machine's time zone cannot move it to another day; it
+// is saved in the folder `DAY`.
+const TAKEN = new Date(2026, 2, 1, 12).getTime() * 1000;
+const DAY = join("2026", "2026-03", "2026-03-01");
+
 const collection = (id: number): Collection => ({
     id,
     ownerID: USER_ID,
@@ -56,7 +64,7 @@ const file = (id: number, collectionID: number): EnteFile => ({
     metadata: {
         title: `file-${id}.jpg`,
         fileType: "image",
-        creationTime: 1,
+        creationTime: TAKEN,
         modificationTime: 1,
     },
     file: { decryptionHeader: "aGVhZGVy" },
@@ -224,6 +232,9 @@ describe("Library content wiring", () => {
         await expect(
             lib.photos.byID({ fileID: 1 })!.thumbnail(),
         ).rejects.toThrow(/content cache/i);
+        await expect(
+            lib.photos.byID({ fileID: 1 })!.download(),
+        ).rejects.toThrow(/content cache/i);
         await expect(
             lib.thumbnails.ensure({ fileIDs: [1], priority: "visible" }),
         ).rejects.toThrow(/content cache/i);
@@ -341,7 +352,7 @@ describe("Photo save path, local copy, content and EXIF", () => {
     it("names where a backup writes the original, which is local once the backup has written it", async () => {
         const lib = await open();
         const photo = lib.photos.byID({ fileID: 1 })!;
-        const savePath = join(root, "backup", "originals", "1.jpg");
+        const savePath = join(root, "backup", DAY, "2026-03-01.1.jpg");
         expect(photo.savePath).toBe(savePath);
         expect(photo.isLocal).toBe(false);
 
@@ -359,23 +370,150 @@ describe("Photo save path, local copy, content and EXIF", () => {
         expect(existsSync(join(root, "cache", "originals", "1.jpg"))).toBe(
             true,
         );
-        expect(existsSync(photo.savePath!)).toBe(false);
+        expect(existsSync(photo.savePath)).toBe(false);
         expect(photo.isLocal).toBe(false);
         await lib.close();
     });
 
-    it("has no save path and is not local without a download directory", async () => {
+    it("saves under photos/ in the working directory at open without a download directory", async () => {
+        const cwd = vi.spyOn(process, "cwd").mockReturnValue(root);
         const lib = await open({ downloadDirectory: undefined });
+        cwd.mockRestore();
         const photo = lib.photos.byID({ fileID: 1 })!;
-        expect(photo.savePath).toBeUndefined();
+        expect(lib.downloadDirectory).toBe(join(root, "photos"));
+        expect(photo.savePath).toBe(
+            join(root, "photos", DAY, "2026-03-01.1.jpg"),
+        );
         expect(photo.isLocal).toBe(false);
         await lib.close();
     });
 
-    it("has no save path and is not local without a content source", async () => {
+    it("refuses an empty download directory", async () => {
+        await expect(open({ downloadDirectory: "" })).rejects.toThrow(
+            /downloadDirectory is empty/,
+        );
+    });
+
+    it("keeps a photo's save path after a refresh removes its file", async () => {
+        // The same account, whose album is deleted on the second refresh.
+        class AlbumDeletedClient extends MockClient {
+            override async collectionsSince(): Promise<CollectionsPage> {
+                if (!this.served) return super.collectionsSince();
+                return { collections: [], deleted: [1], cursor: 2 };
+            }
+        }
+        const lib = await open({ client: new AlbumDeletedClient() });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        await photo.download();
+
+        await lib.fresh();
+
+        expect(lib.photos.byID({ fileID: 1 })).toBeUndefined();
+        expect(photo.savePath).toBe(
+            join(root, "backup", DAY, "2026-03-01.1.jpg"),
+        );
+        expect(photo.isLocal).toBe(true);
+        await lib.close();
+    });
+
+    it("dates the save path and download() by the membership its takenAt comes from", async () => {
+        // One file in two albums. The date edited in Ente has reached album 2's
+        // copy, synced later, but album 1 still has an earlier edit.
+        const older = file(1, 1);
+        older.pubMagicMetadata = {
+            editedTime: new Date(2026, 1, 1, 12).getTime() * 1000,
+        };
+        const newer = file(1, 2);
+        newer.updationTime = 2;
+        newer.pubMagicMetadata = {
+            editedTime: new Date(2026, 3, 15, 12).getTime() * 1000,
+        };
+        const client = {
+            whoami: () => ({ email: "u@example.com", userID: USER_ID }),
+            collectionsSince: async (): Promise<CollectionsPage> => ({
+                collections: [collection(1), collection(2)],
+                deleted: [],
+                cursor: 1,
+            }),
+            filesSince: async (args: {
+                collectionID: number;
+            }): Promise<FilesPage> => ({
+                files: [args.collectionID === 1 ? older : newer],
+                deleted: [],
+                cursor: 1,
+            }),
+        };
+        const lib = await open({ client });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+
+        expect(photo.takenAt).toBe(new Date(2026, 3, 15, 12).getTime());
+        expect(photo.savePath).toBe(
+            join(
+                root,
+                "backup",
+                "2026",
+                "2026-04",
+                "2026-04-15",
+                "2026-04-15.1.jpg",
+            ),
+        );
+
+        // download() writes to that same path, so the photo is then local.
+        const saved = await photo.download();
+        expect(saved.path).toBe(photo.savePath);
+        expect(photo.isLocal).toBe(true);
+        expect(existsSync(join(root, "backup", "2026", "2026-02"))).toBe(false);
+        await lib.close();
+    });
+
+    it("downloads a photo held across a refresh that edits its date to the save path it names", async () => {
+        // The same account, whose second refresh brings a date edited in Ente.
+        const edited = file(1, 1);
+        edited.updationTime = 2;
+        edited.pubMagicMetadata = {
+            editedTime: new Date(2026, 3, 15, 12).getTime() * 1000,
+        };
+        class DateEditedClient extends MockClient {
+            refreshes = 0;
+            override async collectionsSince(): Promise<CollectionsPage> {
+                this.refreshes++;
+                return {
+                    collections: [
+                        { ...collection(1), updationTime: this.refreshes },
+                    ],
+                    deleted: [],
+                    cursor: this.refreshes,
+                };
+            }
+            override async filesSince(): Promise<FilesPage> {
+                return {
+                    files: [this.refreshes === 1 ? file(1, 1) : edited],
+                    deleted: [],
+                    cursor: this.refreshes,
+                };
+            }
+        }
+        const lib = await open({ client: new DateEditedClient() });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+
+        await lib.fresh();
+        expect(lib.photos.byID({ fileID: 1 })!.takenAt).toBe(
+            new Date(2026, 3, 15, 12).getTime(),
+        );
+
+        const saved = await photo.download();
+        expect(saved.path).toBe(photo.savePath);
+        expect(saved.path).toBe(join(root, "backup", DAY, "2026-03-01.1.jpg"));
+        expect(photo.isLocal).toBe(true);
+        await lib.close();
+    });
+
+    it("has a save path, and is not local, without a content source", async () => {
         const lib = await open({ contentSource: undefined });
         const photo = lib.photos.byID({ fileID: 1 })!;
-        expect(photo.savePath).toBeUndefined();
+        expect(photo.savePath).toBe(
+            join(root, "backup", DAY, "2026-03-01.1.jpg"),
+        );
         expect(photo.isLocal).toBe(false);
         await lib.close();
     });
@@ -387,18 +525,104 @@ describe("Photo save path, local copy, content and EXIF", () => {
             contentSource: cdnSource(new Map([[1, body]])),
         });
         const photo = lib.photos.byID({ fileID: 1 })!;
-        const originals = join(root, "backup", "originals");
+        const day = join(root, "backup", DAY);
         // Until then the name comes from the title, file-1.jpg; the backup
         // stores the image with the extension found inside the live photo.
-        expect(photo.savePath).toBe(join(originals, "1.jpg"));
+        expect(photo.savePath).toBe(join(day, "2026-03-01.1.jpg"));
 
         await lib.backup();
-        expect(photo.savePath).toBe(join(originals, "1.heic"));
+        expect(photo.savePath).toBe(join(day, "2026-03-01.1.heic"));
         expect(photo.isLocal).toBe(true);
         expect(await photo.content()).toEqual(Buffer.from(IMAGE));
         await lib.close();
     });
 
+    it("downloads an original the cache holds by copying it, without fetching it again", async () => {
+        const source = stubSource();
+        const lib = await open({ contentSource: source });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        await photo.original();
+        expect(source.originalCalls()).toBe(1);
+        expect(photo.isLocal).toBe(false);
+
+        const saved = await photo.download();
+
+        expect(source.originalCalls()).toBe(1);
+        expect(saved).toEqual({
+            path: photo.savePath,
+            bytes: "orig-bytes".length,
+        });
+        expect(readFileSync(photo.savePath, "utf-8")).toBe("orig-bytes");
+        expect(photo.isLocal).toBe(true);
+        // The cache keeps its own copy.
+        expect(existsSync(join(root, "cache", "originals", "1.jpg"))).toBe(
+            true,
+        );
+        await lib.close();
+    });
+
+    it("downloads an original the cache does not hold straight to its save path", async () => {
+        const source = stubSource();
+        const lib = await open({ contentSource: source });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+
+        const saved = await photo.download();
+
+        expect(source.originalCalls()).toBe(1);
+        expect(saved.path).toBe(join(root, "backup", DAY, "2026-03-01.1.jpg"));
+        expect(readFileSync(saved.path, "utf-8")).toBe("orig-bytes");
+        expect(photo.isLocal).toBe(true);
+        expect(readdirSync(join(root, "cache", "originals"))).toEqual([]);
+        await lib.close();
+    });
+
+    it("does nothing when download() finds the original already at its save path", async () => {
+        const source = stubSource();
+        const lib = await open({ contentSource: source });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        const first = await photo.download();
+        const written = statSync(first.path).ino;
+
+        const second = await photo.download();
+
+        expect(second).toEqual(first);
+        expect(source.originalCalls()).toBe(1);
+        expect(statSync(second.path).ino).toBe(written);
+        await lib.close();
+    });
+
+    it("downloads a live photo the cache holds as its image, its video and the JSON file naming them", async () => {
+        const { file: live, body } = await asLivePhoto(file(1, 1));
+        const lib = await open({
+            client: new FilesClient([live]),
+            contentSource: cdnSource(new Map([[1, body]])),
+        });
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        await photo.original();
+        const day = join(root, "backup", DAY);
+
+        const saved = await photo.download();
+
+        expect(saved).toEqual({
+            path: join(day, "2026-03-01.1.heic"),
+            videoPath: join(day, "2026-03-01.1.mov"),
+            bytes: IMAGE.length,
+        });
+        expect(readdirSync(day).sort()).toEqual([
+            "2026-03-01.1.heic",
+            "2026-03-01.1.livephoto.json",
+            "2026-03-01.1.mov",
+        ]);
+        expect(
+            JSON.parse(
+                readFileSync(join(day, "2026-03-01.1.livephoto.json"), "utf-8"),
+            ),
+        ).toEqual({ image: "2026-03-01.1.heic", video: "2026-03-01.1.mov" });
+        expect(photo.savePath).toBe(saved.path);
+        expect(photo.isLocal).toBe(true);
+        await lib.close();
+    });
+
     it("reads the common EXIF fields of a JPEG original", async () => {
         const lib = await open({ contentSource: stubSource(JPEG_WITH_EXIF) });
         expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({
@@ -420,8 +644,8 @@ describe("Photo save path, local copy, content and EXIF", () => {
         await lib.close();
     });
 
-    // What exif() returns for HEIC_WITH_EXIF, which holds the same values as
-    // JPEG_WITH_EXIF.
+    // What exif() returns for HEIC_WITH_EXIF, and for JPEG_WITH_EXIF, which
+    // holds the same values.
     const heicFields: PhotoExif = {
         make: "Canon",
         model: "EOS R5",
@@ -462,9 +686,35 @@ describe("Photo save path, local copy, content and EXIF", () => {
         await lib.close();
     });
 
+    // The build's type check, not this test, makes sure `Photo` has a method
+    // for every `PhotoExif` field, whatever the fixtures hold: `Photo`
+    // implements a type with one method per field. This test checks that each
+    // method gives the same value as exif().
+    it.each([
+        ["JPEG", JPEG_WITH_EXIF],
+        ["HEIC", HEIC_WITH_EXIF],
+    ])(
+        "has a method for each field exif() returns, giving the same value, for a %s",
+        async (_, bytes) => {
+            const lib = await open({ contentSource: stubSource(bytes) });
+            const photo = lib.photos.byID({ fileID: 1 })!;
+            const exif = await photo.exif();
+            // The file holds every field, so every method is checked.
+            expect(exif).toStrictEqual(heicFields);
+            for (const [field, value] of Object.entries(exif)) {
+                expect(await photo[field as keyof PhotoExif]()).toStrictEqual(
+                    value,
+                );
+            }
+            await lib.close();
+        },
+    );
+
     it("returns no EXIF fields for an original that is not an image", async () => {
         const lib = await open();
-        expect(await lib.photos.byID({ fileID: 1 })!.exif()).toStrictEqual({});
+        const photo = lib.photos.byID({ fileID: 1 })!;
+        expect(await photo.exif()).toStrictEqual({});
+        expect(await photo.dateTimeOriginal()).toBeUndefined();
         await lib.close();
     });
 

test/library/content.test.ts

@@ -7,8 +7,8 @@
  * 1. **Fetch once, then serve from disk.** The first `original`/`thumbnail`
  *    fetches through the request pool and stores the bytes; the next finds the
  *    file present and returns its path with a single `skipped` event and no
- *    network. A file already sitting in the backup `downloadDirectory` counts
- *    as present too.
+ *    network. A file already stored at its save path under the
+ *    `downloadDirectory` counts as present too.
  * 2. **Present-means-complete.** Content appears only by the streaming atomic
  *    writer's rename, so a file that exists is whole. The directory listing
  *    taken at `open()` is the record of what is cached, and the orphan temp
@@ -41,6 +41,7 @@ import { join } from "node:path";
 
 import {
     ContentCache,
+    savePath,
     type ContentSource,
     type EnsureEvent,
 } from "../../src/library/content.js";
@@ -152,12 +153,48 @@ const buildCache = (
         pools: args.pools ?? new RequestPools(),
         source,
         cacheDirectory: cacheDir,
-        downloadDirectory: args.downloadDirectory,
+        downloadDirectory: args.downloadDirectory ?? join(root, "photos"),
         getFile: (id) => byID.get(id),
     });
     return { cache, source };
 };
 
+// Microseconds, as Ente stores times, for noon local time on a day, so the
+// machine's time zone cannot move the photo to another day.
+const noon = (year: number, month: number, day: number): number =>
+    new Date(year, month - 1, day, 12).getTime() * 1000;
+
+describe("savePath", () => {
+    it("files an original by year, month and day under the root", () => {
+        const f = file(12345, "IMG_0001.HEIC");
+        f.metadata.creationTime = noon(2026, 3, 1);
+
+        expect(savePath("/photos", f)).toBe(
+            "/photos/2026/2026-03/2026-03-01/2026-03-01.12345.HEIC",
+        );
+    });
+
+    it("dates an original by the date the user set, when there is one", () => {
+        const f = file(7, "a.jpg");
+        f.metadata.creationTime = noon(2026, 3, 1);
+        f.pubMagicMetadata = { editedTime: noon(1999, 12, 31) };
+
+        expect(savePath("/photos", f)).toBe(
+            "/photos/1999/1999-12/1999-12-31/1999-12-31.7.jpg",
+        );
+    });
+
+    it("takes the extension from the title it was uploaded with, not a new name", () => {
+        const f = file(8, "upload");
+        f.metadata.creationTime = noon(2026, 3, 1);
+        f.pubMagicMetadata = { editedName: "renamed.png" };
+
+        expect(savePath("/photos", f)).toBe(
+            "/photos/2026/2026-03/2026-03-01/2026-03-01.8.bin",
+        );
+    });
+});
+
 describe("ContentCache.open", () => {
     it("creates the cache directories with 0700 permissions", async () => {
         const { cache } = buildCache();
@@ -274,11 +311,17 @@ describe("ContentCache.original / thumbnail", () => {
 
     it("serves a file already present in the download directory without fetching", async () => {
         const downloadDirectory = join(root, "backup");
-        mkdirSync(join(downloadDirectory, "originals"), { recursive: true });
-        const backupPath = join(downloadDirectory, "originals", "1.jpg");
+        const day = join(downloadDirectory, "2026", "2026-03", "2026-03-01");
+        mkdirSync(day, { recursive: true });
+        const backupPath = join(day, "2026-03-01.1.jpg");
         writeFileSync(backupPath, "from-backup");
+        const f = file(1);
+        f.metadata.creationTime = noon(2026, 3, 1);
 
-        const { cache, source } = buildCache({ downloadDirectory });
+        const { cache, source } = buildCache({
+            downloadDirectory,
+            files: [f],
+        });
         await cache.open();
 
         const events: EnsureEvent["status"][] = [];
@@ -649,6 +692,7 @@ describe("ContentCache live photos", () => {
                 ]),
             ),
             cacheDirectory: cacheDir,
+            downloadDirectory: join(root, "photos"),
             getFile: (id) => [a.file, b.file].find((f) => f.id === id),
             // Room for one live photo, on a disk with plenty free.
             cacheOriginalsMaxBytes: size,

test/library/precache.test.ts

@@ -280,6 +280,7 @@ describe("Precache eviction integration", () => {
             pools: new RequestPools(),
             source,
             cacheDirectory: cacheDir,
+            downloadDirectory: join(root, "photos"),
             getFile: (id) => byID.get(id),
             statfs,
             cacheOriginalsMaxBytes: 25, // holds two 10-byte originals
@@ -348,6 +349,7 @@ describe("Precache preemption", () => {
             pools: new RequestPools({ contentConcurrency: 1 }),
             source,
             cacheDirectory: join(root, "cache"),
+            downloadDirectory: join(root, "photos"),
             getFile: (id) => byID.get(id),
             statfs: async () => ({ bsize: 1, bavail: 1_000_000_000 }),
             freeBelowBytes: 0,

test/library/read.test.ts

@@ -36,6 +36,7 @@ import {
     makeAlbumsAPI,
     makePhotosAPI,
     makeTimelineAPI,
+    type SavePathLookup,
     type TimelineGroup,
 } from "../../src/library/read.js";
 import { Library } from "../../src/library/index.js";
@@ -101,12 +102,19 @@ const file = (
 };
 
 // Build the three API objects over one fixed projection, the way `Library`
-// wires them over its live store.
+// wires them over its live store. Save paths are covered in
+// content-library.test.ts; these tests never ask for one.
 const apis = (records: DerivedRecords) => {
     const derive = () => records;
+    const saves: SavePathLookup = {
+        savePath: () => {
+            throw new Error("no save paths in these tests");
+        },
+        isLocal: () => false,
+    };
     return {
-        albums: makeAlbumsAPI(derive),
-        photos: makePhotosAPI(derive),
+        albums: makeAlbumsAPI(derive, saves),
+        photos: makePhotosAPI(derive, saves),
         timeline: makeTimelineAPI(derive),
     };
 };