Merge pull request 'next → main: Photo save path, download and EXIF; version from git; example script' (#134 ) from next into main

Reviewed-on: #134
2026-10-22 18:55:49 +02:00
27 changed files with 437 additions and 3750 deletions
@@ -2,31 +2,20 @@
 quak is a WTFPL-licensed TypeScript client library and CLI by
 [@sneak](https://sneak.berlin) for the [Ente](https://ente.io) end-to-end
-encrypted photo hosting service. It logs in, lists collections and their files,
+encrypted photo hosting service. It logs in, enumerates collections and files,
-and downloads and decrypts single files.
+and downloads individual images while decrypting them on the way to disk.
-`quak backup` downloads every file in the account into a local directory tree.
+quak also includes a resilient backup command that downloads every file in the
-It downloads and stores each file once, however many collections hold it. It
+account into a deduplicated local directory tree, skipping files that already
-skips files already on disk. It logs a failed download and moves on to the next
+exist on disk and continuing past individual download failures instead of
-file. Beside each file it writes a JSON file that holds:
+crashing. For each file it persists the basic metadata fields quak keeps (title,
-
+file type, creation and modification time, latitude, longitude, content hash),
- the file's title and file type
+its update time, the private and public magic metadata in full, Ente's ML data
- its creation and modification times
+for it when there is any, and, for an image (for a live photo, its image), its
- its latitude and longitude
+original's EXIF and XMP, with its dimensions for a JPEG only; for a video it
- its content hash
+keeps none of these three. It runs unattended from cron (see "Running the backup
- its update time
+from cron"). A helper subcommand can detect and regenerate missing thumbnails,
- its private and public magic metadata, in full
+encrypting and uploading them back to the server.
 - the ML data that Ente has for it, without the CLIP embedding
 - its keywords in place of that embedding (see "Backup layout")
 - for an image, the EXIF and XMP of its original, and its dimensions if it is a
  JPEG
 - for a live photo, the same for its image
 The backup runs unattended from cron (see "Running the backup from cron").
 `quak helper list-missing-thumbnails` finds files whose thumbnail is missing.
 `quak helper fix-missing-thumbnails` makes a new thumbnail for such a file, then
 encrypts it and uploads it to the server.
 ## Getting Started
@@ -70,11 +59,10 @@ const client = await Client.login({
    password: "your-password",
 });
-// Open a cache-backed library. On an empty cache, or one that only
+// Open a cache-backed library. On an empty cache this awaits one server
-// `lib.refreshCollection()` wrote, this awaits one server refresh. Otherwise
+// refresh; on an existing cache it returns immediately and refreshes in the
-// it returns immediately and refreshes in the background. A background timer
+// background. Later refreshes start `refreshIntervalSeconds` (default 3) after
-// then refreshes again `refreshIntervalSeconds` (default 3) after its previous
+// the previous one ends.
 // refresh ends.
 const lib = await Library.open({ client });
 // Default reads answer synchronously from the local cache — no network.
@@ -383,11 +371,6 @@ quak/
                        backup-metadata: the metadata quak keeps, as JSON
        exif.ts         EXIF read from an image's bytes with exifreader
        mldata-fetch.ts fetch + decrypt per-file ML data
        clip-keywords.ts
                        a file's keywords from its CLIP embedding
        clip-keyword-vectors.ts
                        Ente's Discover categories with their text
                        embeddings, written by bin/clip-keyword-vectors
        filename.ts     safe file names from server metadata
        errors.ts       error types shared across layers, and how an error
                        is described
@@ -404,9 +387,6 @@ quak/
        index.ts        public library exports
    bin/
        quak.ts         CLI entrypoint (commander.js)
        clip-keyword-vectors, clip-keyword-vectors.py
                        write src/clip-keyword-vectors.ts and a test
                        fixture (see Source attribution)
    examples/
        download-albums.ts
                        download every album's photos and metadata
@@ -651,17 +631,17 @@ The CLI stores the snapshot at the platform-appropriate data directory via
 `0600`. The key material is stored in cleartext in the JSON; treat this file as
 you would treat the password itself. A missing file is reported as "not logged
 in"; a file that exists but is corrupt is reported as such, naming the bad
-field. The server answers HTTP 401 when it no longer accepts the saved session's
+field. When the refresh a command starts with gets HTTP 401 from the server,
-token. A command that gets that answer prints one line,
+because it no longer accepts the saved session's token, the command prints one
-`quak: the saved session is no longer valid; run "quak login"`, with no stack
+line, `quak: the saved session is no longer valid; run "quak login"`, with no
-trace. All three exit with status 3, which means the user must run `quak login`
+stack trace. All three exit with status 3, which means the user must run
-again. `quak logout` is the exception: with no file it says there is no session
+`quak login` again. `quak logout` is the exception: with no file it says there
-and exits 0, and it handles a corrupt file or a failed server call as described
+is no session and exits 0, and it handles a corrupt file or a failed server call
-below. `quak backup` meets an expired session on the refresh that starts every
+as described below. `quak backup` meets an expired session on the refresh that
-run, before it touches any file but its lock (see "Backup layout"). A session
+starts every run, before it touches any file but its lock (see "Backup layout").
-that stops working partway through a backup instead fails each remaining file
+A session that stops working partway through a backup instead fails each
-into `failures.json`, so that run exits 1 and the next one stops at its refresh
+remaining file into `failures.json`, so that run exits 1 and the next one stops
-with status 3. No command but `quak login` ever prompts.
+at its refresh with status 3. No command but `quak login` ever prompts.
 `quak logout` ends the session on the server, so the token in `session.json`
 stops working even in a copy of the file, and then deletes the file. If the
@@ -691,40 +671,22 @@ quak helper fix-missing-thumbnails [--file ids] [--json]  generate + upload miss
 ```
 Every command except `login`, `whoami` and `logout` runs on the cache-backed
-library. Each read command makes a fresh server round-trip before it answers. It
+library. The read commands — `collections`, `files`, `get`, `get-thumb`,
-then reports the account's current state, not what the cache last held. The read
+`backup-metadata`, `helper list-missing-thumbnails` and
-commands are:
+`helper fix-missing-thumbnails` — force a fresh server round-trip before they
-
+answer, so they report current account state rather than whatever the cache last
- `collections`
+held. `collections` asks the server for the collection list alone, in one
- `files`
+request, and neither fetches any collection's files nor changes the cache. The
- `get`
+others wait for a refresh. With an empty cache, as on a first run, that refresh
- `get-thumb`
+fetches the files of every collection, one collection after another, and stores
- `backup-metadata`
+nothing until it has them all, which on a large account takes a while. Meanwhile
- `helper list-missing-thumbnails`
+the command logs a line on stderr for each collection whose files it has
- `helper fix-missing-thumbnails`
+fetched, such as `Fetched the files of 3 of 120 collections`, with `--json` too;
-
+`backup` does the same while the refresh it starts with runs. stdout holds only
-`collections` asks the server for the collection list alone, in one request. It
+the command's output. If that round-trip fails, the command prints the error on
-fetches no collection's files and leaves the cache as it is. `files` with a
+one line and exits 1, or 3 when the server no longer accepts the saved session
-collection ID asks for the collection list the same way. It then asks for the
+(see "Session handling"). An album or file quak cannot decrypt does not fail it;
-files of that collection alone, and stores them in the cache. It asks for no
+the command answers from what did decrypt (see "Default reads vs. fresh reads").
 files when the cache's copy of that collection is current. The other read
 commands, and `files` without a collection ID, wait for a refresh. So does
 `files` with the ID of a collection that is new since the last refresh.
 The first refresh fetches the files of every collection, one collection after
 another. That includes any collection that `files` with a collection ID stored
 before it. The refresh stores nothing until it has them all, and on a large
 account that takes a while. Meanwhile the command logs a line on stderr for each
 collection whose files it has fetched, such as
 `Fetched the files of 3 of 120 collections`. It logs these lines with `--json`
 too. `backup` logs them during the refresh it starts with. stdout holds only the
 command's output.
 If the server round-trip fails, the command prints the error on one line. It
 exits 1, or 3 when the server no longer accepts the saved session (see "Session
 handling"). An album or file that quak cannot decrypt does not fail the command.
 The command answers from what did decrypt (see "Default reads vs. fresh reads").
 `--cache-dir` overrides where the cache lives; without it each account gets its
 own directory under the per-user cache path.
@@ -779,10 +741,9 @@ its `Failed files:` list. Every other line is logged as it is without `--json`.
 exit status 1.
 `files <collectionID>` lists the files in that collection. `files` with no
-argument lists every file in the account once, collection by collection. The
+argument lists every file in the account, collection by collection, each file
-collections come in the order the server first sent them in a refresh. A file in
+once: a file in several collections is listed with the first of them, which is
-several collections is listed with the first of them, which is its
+its `collectionID` in `--json`.
 `collectionID` in `--json`.
 An ID given to `files`, `get`, `get-thumb` or
 `helper fix-missing-thumbnails --file` is written in decimal digits, no larger
@@ -822,11 +783,9 @@ as it was and goes into `failures.json` (see "Backup layout").
 `backup-metadata <dir>` writes `account.json` and, for each collection, a
 directory `collections/<id>-<name>/` holding `_collection.json` and a
-`<fileID>.json` for each of its files. Each `<fileID>.json` holds the file's ML
+`<fileID>.json` for each of its files. The collection's name has unsafe
-data and keywords as `quak backup` writes them (see "Backup layout"). The
+characters replaced and is cut short between two characters so that the
-collection's name has unsafe characters replaced and is cut short between two
+directory's name fits in 255 bytes; the ID keeps the directories apart.
 characters so that the directory's name fits in 255 bytes; the ID keeps the
 directories apart.
 `backup-metadata` fetches ML data in requests of up to 200 files. When a request
 fails, the error is logged, each of its files is written with the reason in an
@@ -859,11 +818,11 @@ the smallest does not.
                                    below)
        YYYY-MM-DD.<fileID>.json    the file's basic metadata fields quak
                                    keeps, its update time, its private and
-                                    public magic metadata, its ML data and
+                                    public magic metadata, its ML data, and,
-                                    keywords, and, for an image (for a live
+                                    for an image (for a live photo, its
-                                    photo, its image), its original's EXIF
+                                    image), its original's EXIF and XMP, with
-                                    and XMP, with dimensions for a JPEG
+                                    dimensions for a JPEG only; none of these
-                                    only; none of these three for a video
+                                    three for a video
        YYYY-MM-DD.<fileID>.livephoto.json
                                    which of a live photo's two files is which
    collections/
@@ -894,51 +853,20 @@ JSON holds its `id`, `collectionID`, `ownerID`, `metadata` and `updationTime`,
 and its `magicMetadata` and `pubMagicMetadata` when it has them. Update times
 are in microseconds, as Ente records them.
-A file's JSON holds Ente's ML data for it as `mlData`, such as the faces Ente
+A file's JSON holds Ente's ML data for it (its faces and its CLIP embedding) as
-found, without its CLIP embedding. It holds `keywords` in place of the
+`mlData`, the same payload `backup-metadata` writes; a file Ente has no ML data
-embedding.
+for has no `mlData`. The backup waits for the library's ML data fetch to finish
-
+before it writes the JSON files. If that fetch fails, each file whose ML data is
-The Discover section of Ente's photos app has 16 categories:
+not in the cache gets the reason in `mlDataError` instead and counts as failed,
-
+and the next run fetches it again. The same goes for a file with no ML data in
- Identity (no videos)
+the cache whose ML data the server sent but quak could not decrypt, gunzip or
- Screenshots (no videos)
+parse. Its `mlDataError` says why, and `failures.json` records it with an error
- QR Codes (no videos)
+starting `ML data: `. quak keeps that reason in memory only and caches nothing
- Receipts
+for the file, so the next run asks for its ML data again. An ML data fetch that
- Notes
+fails, such as one the library's refresh starts while the backup writes the JSON
- Memes
+files, leaves the reasons as the last fetch that succeeded left them. The JSON
- Visiting Cards (no videos)
+files are rewritten on every run, so ML data that arrived since the last run
- Babies
+appears.
 - Pets
 - Selfies
 - Wallpapers (no videos)
 - Food
 - Celebrations
 - Sunset
 - Hills
 - Greenery
 A file's keywords are the titles of the categories it falls in. A file's score
 for a category is the cosine similarity of its CLIP embedding and the text
 embedding of the category's query. As in Ente's app, the file falls in the
 category when that score is at least the category's minimum score. A video never
 falls in a category marked "no videos". The keywords are listed highest score
 first.
 A file with no ML data has neither `mlData` nor `keywords`. A file whose ML data
 holds no usable CLIP embedding has no `keywords`. `backup-metadata` writes both
 fields the same way.
 The backup waits for the library's ML data fetch to finish before it writes the
 JSON files. If that fetch fails, each file whose ML data is not in the cache
 gets the reason in `mlDataError` instead and counts as failed, and the next run
 fetches it again. The same goes for a file with no ML data in the cache whose ML
 data the server sent but quak could not decrypt, gunzip or parse. Its
 `mlDataError` says why, and `failures.json` records it with an error starting
 `ML data: `. quak keeps that reason in memory only and caches nothing for the
 file, so the next run asks for its ML data again. An ML data fetch that fails,
 such as one the library's refresh starts while the backup writes the JSON files,
 leaves the reasons as the last fetch that succeeded left them. The JSON files
 are rewritten on every run, so ML data that arrived since the last run appears.
 A file's JSON holds, as `imageMetadata`, what `backup-metadata --exif` records
 from its original, or from a live photo's image: `format`, `width` and `height`
@@ -1122,17 +1050,15 @@ against a fake of the Ente HTTP API, and `yarn test` verifies them.
 ### Opening a library
 `Library.open(options)` loads the on-disk cache, starts the background refresh
-loop, and resolves to a `Library`. On an empty cache, or one that only
+loop, and resolves to a `Library`. On an empty cache it awaits the first
-`lib.refreshCollection()` wrote, it awaits one refresh. It then opens onto the
+refresh, so it opens onto the account's data whenever the server is reachable;
-account's data whenever the server is reachable. If that refresh fails, it opens
+if that refresh fails, it opens with no data and records the error in
-onto what the cache holds, and records the error in `lib.status()`. On any other
+`lib.status()`. On an existing cache it returns immediately and refreshes in the
-cache it returns immediately and refreshes in the background. An unreachable
+background, so an unreachable server does not block opening. With
-server then does not block opening.
+`refreshOnOpen: false` it starts no refresh and returns at once onto what the
-
+cache holds, empty or not; a refresh then starts only when `fresh()` or
-With `refreshOnOpen: false`, `open()` starts no refresh. It returns at once onto
+`lib.backup()` asks, or the background timer fires. The CLI's read commands open
-what the cache holds, even when the cache is empty. A refresh then starts only
+it so (see "CLI surface").
 when `fresh()` or `lib.backup()` asks, or the background timer fires. The CLI's
 read commands open the library this way (see "CLI surface").
 `LibraryOptions`:
@@ -1159,35 +1085,22 @@ when the library opens; `lib.downloadDirectory` holds the result.
 `onProgress` receives a `RefreshEvent` with status `"started"` as a refresh, an
 ML data fetch or a precache sweep starts, and `"done"` or `"failed"` as it ends.
 In between, a refresh sends `"progress"` after each collection whose files it
-fetched. That event's `fetched` is the number of collections whose files the
+fetched, with `fetched`, how many collections it has fetched the files of so
-refresh has fetched so far. Its `total` is the number of collections whose files
+far, and `total`, how many it will. A refresh fetches the files of each
-it will fetch in all. A refresh fetches the files of each collection that is new
+collection that is new or changed since the cache's copy, so on an empty cache
-or changed since the cache's copy. On the first refresh, that is every
+it fetches those of every collection.
 collection.
 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).
-`lib.status()` returns a `LibraryStatus`, which holds:
+`lib.status()` returns a `LibraryStatus` (collection/file counts, last
-
+refresh/ML times and errors, originals usage and effective limit, precache
- the collection and file counts
+progress, and `closed`). `lib.close()` stops the background timer; it is
- the time of the last refresh that succeeded, and the error of the latest
+idempotent, and an in-flight refresh is left to finish. The promise it returns
-  refresh if it failed
+resolves once that refresh (including its cache write), the ML data fetch and
- the same two for the ML data fetch
+the precache fetches already running have all finished, so the cache directory
- the originals cache's usage and its effective limit
+can then be removed.
 - the precache progress
 - `closed`
 `lib.close()` stops the background timer, and is idempotent. A refresh or
 `lib.refreshCollection()` in flight is left to finish. `close()` returns a
 promise that resolves once all of these have finished:
 - that refresh or `lib.refreshCollection()`, with its cache write
 - the ML data fetch
 - the precache fetches already running
 The cache directory can then be removed.
 `lib.status().mlDataErrors` lists, as `{ fileID, error }`, each file whose ML
 data the last ML data fetch that succeeded got but could not decrypt, gunzip or
@@ -1201,72 +1114,39 @@ cache.
 Default reads — `lib.albums`, `lib.photos`, `lib.timeline` — answer
 synchronously from the copy held in RAM and never touch the network. A refresh
-changes that copy only once all its server requests have succeeded.
+changes that copy only once all its server requests have succeeded, and the
-`lib.refreshCollection()` changes it the same way for one collection. So a
+background timer starts the next refresh `refreshIntervalSeconds` after the
-default read is immediate, but only as current as the last refresh or
+previous one ends. So a default read is immediate, but only as current as the
-`lib.refreshCollection()` whose requests all succeeded. Right after `open()`
+last refresh whose requests all succeeded; right after opening an existing
-returns without awaiting a refresh, that copy is the one loaded from disk.
+cache, it is the copy on disk.
-The background timer takes a turn `refreshIntervalSeconds` after its last turn
+`await lib.fresh()` waits for a refresh to complete and persist, and returns the
-ends. Each turn starts a refresh, unless a refresh or `lib.refreshCollection()`
+same `{ albums, photos, timeline }` namespaces, which then reflect a completed
-is already running.
+server round-trip. When a refresh is already running, background or not,
-
+`fresh()` waits for that one, so its answer can come from requests made before
-`await lib.fresh()` waits for a refresh to complete and persist. It then returns
+the call; only when none is running does it start one. A refresh that fails
 the same `{ albums, photos, timeline }` namespaces, which reflect a completed
 server round-trip. If a `lib.refreshCollection()` is running, `fresh()` first
 waits for it to end. When a refresh is already running, background or not,
 `fresh()` waits for that one. Its answer can then come from requests made before
 the call. Only when none is running does it start one. A refresh that fails
 rejects the caller (default reads stay silent and keep serving the last good
-copy). Every CLI read command calls `fresh()`, except `quak collections`.
+copy). The CLI's read commands use fresh reads (issue
-`quak files` with a collection ID calls it only when `lib.refreshCollection()`
+https://git.eeqj.de/sneak/quak/issues/75).
 resolves to `false`.
-`await lib.freshCollections()` is the fresh read of the collection list alone.
+`await lib.freshCollections()` is the fresh read of the collection list alone:
-It sends one collections request. It answers with every live collection that
+one collections request, answered with every live collection that decrypts, as
-decrypts, in the server's order, as the `Collection` objects that
+the `Collection` objects `listCollections()` returns, in the server's order. It
-`listCollections()` returns. It fetches no collection's files and stores
+fetches no collection's files and stores nothing, not even the list: a refresh
-nothing, not even the list. A refresh from a cursor past 0 fetches a
+fetches a collection's files only when the collection is new or has changed
-collection's files only when the collection is new or has changed since the
+since the stored copy, so a collection stored without its files would never get
-stored copy. So does `lib.refreshCollection()`. Neither would fetch the files of
+them. `quak collections` uses it (issue
-a collection stored without them. `quak collections` uses `freshCollections()`.
+https://git.eeqj.de/sneak/quak/issues/210).
-`await lib.refreshCollection(collection)` brings one collection up to date in
+An album or file in the server's answer that quak cannot decrypt, or whose
-the cache, given its `Collection` from `freshCollections()`. It does for that
+metadata is not JSON, does not fail the refresh. The refresh leaves it out, an
-collection what a refresh does for a changed one, and fetches no other
+album with all its files, and drops any older copy the cache held, so reads
-collection's files. It fetches the collection's files changed since the cache's
+answer from what did decrypt. The library keeps a list of what it left out, with
-copy, or all of them when the cache has no copy. It then stores and saves them.
+the reason, in `metadata.json`: the next refresh asks the server only for what
-It sends no request when the cache's copy has the same `updationTime` or a later
+changed, so it would not see the record again. A record stays on that list until
-one. It resolves to `true` when the cache then holds the collection.
+a later refresh gets a copy that decrypts or learns that the server deleted it.
-
+`lib.backup()` reports each such album, and each such file in its scope that has
-`lib.refreshCollection()` adds a collection the cache does not hold only while
+no copy that decrypted (see "Backup layout").
 the refresh cursor is 0. The cursor moves past 0 once a refresh receives the
 account's collections. After that, for a collection the cache does not hold, it
 sends no request and resolves to `false`. Such a collection is new since that
 refresh, or the refresh dropped it. Only a refresh may then add it, after the
 collections the cache holds.
 A refresh from a cursor of 0 replaces everything the cache holds. It fetches the
 files of every collection, even those `lib.refreshCollection()` stored. It
 stores the collections in the server's order. The cache then holds what it would
 had `lib.refreshCollection()` never run.
 `lib.refreshCollection()` leaves the refresh cursor where it was, so the next
 refresh still fetches the files of every other collection that changed. It never
 runs at the same time as a refresh. It first waits for a running refresh or
 `lib.refreshCollection()` to end. While it runs, a `fresh()` or `lib.backup()`
 waits for it to end. `quak files` with a collection ID uses it.
 A refresh does not fail on an album or file that quak cannot decrypt, or whose
 metadata is not JSON. The refresh leaves out such a file, and such an album
 together with all its files. It also drops any older copy that the cache held,
 so reads answer from what did decrypt. The library keeps a list of what it left
 out, with the reason, in `metadata.json`. The next refresh asks the server only
 for what changed, so it would not see them again. An entry stays on that list
 until a later refresh or `lib.refreshCollection()` stores a copy that decrypts,
 or learns that the server deleted it. `lib.backup()` reports each such album,
 and each such file in its scope that has no copy that decrypted (see "Backup
 layout").
 ### Read surface
@@ -1360,17 +1240,10 @@ The GUI-facing records hold no key material and no binary, so they survive
 - `LibrarySnapshot`: `{ albums, photos, takenAt }`.
 `lib.snapshot()` returns a `LibrarySnapshot` (albums newest-updated first,
-photos newest first). `lib.subscribe({ onChange })` returns `{ unsubscribe }`.
+photos newest first). `lib.subscribe({ onChange })` delivers a `LibraryChange`
-It calls `onChange` with a `LibraryChange` whenever a refresh or
+(`albumsChanged`, `photosChanged`, `fileIDsRemoved`, `albumIDsRemoved`,
-`lib.refreshCollection()` changes these records. A refresh or
+`refreshedAt`) whenever a refresh alters the projection, and returns
-`lib.refreshCollection()` that changes nothing does not call it. A
+`{ unsubscribe }`; a refresh that changes nothing delivers nothing.
 `LibraryChange` holds:
 - `albumsChanged`
 - `photosChanged`
 - `fileIDsRemoved`
 - `albumIDsRemoved`
 - `refreshedAt`
 ### Thumbnails, ML search, and backup
@@ -1386,44 +1259,29 @@ It calls `onChange` with a `LibraryChange` whenever a refresh or
  `SimilarResult[]` (`{ fileID, score }`, cosine similarity, most similar first,
  default limit 20). quak bundles no text encoder, so `searchByEmbedding` takes
  a query vector the caller produced elsewhere.
- `await lib.backup(opts?)` → `BackupResult`. It takes the lock, `backup.lock`
+- `await lib.backup(opts?)` → `BackupResult`. It takes the lock in the download
-  in the download directory. It fails at once with an error whose `code` is
+  directory, and fails at once with an error whose `code` is `ELOCKED` while
-  `ELOCKED` while another backup of that directory runs. A caller can instead
+  another backup of it runs. A caller can instead take the lock itself, before
-  take the lock itself before it opens its library, as `quak backup` does.
+  it opens its library, as `quak backup` does: `await lockBackupDirectory(dir)`
-  `await lockBackupDirectory(dir)` takes it, failing the same way, and returns a
+  takes it, failing the same way, and returns a `BackupLock`, whose `release()`
-  `BackupLock`. Its `release()` removes the lock unless it was lost, and its
+  removes the lock unless it was lost and whose `lost` holds why it was lost.
-  `lost` holds why it was lost. The caller passes it to the backup as `lock`,
+  The caller passes it to the backup as `lock`, and releases it once the backup
-  and releases it once the backup ends.
+  ends. It waits for a refresh as `fresh()` does, puts every in-scope original
-
+  not already at its save path there as `photo.download()` does (and, with
-    The backup waits for a refresh as `fresh()` does. It then fetches each
+  `includeThumbnails`, fetches thumbnails) through the content cache, waits for
-    in-scope original that is not yet at its save path, as `photo.download()`
+  an ML data fetch, and rebuilds the on-disk backup tree with a durable failure
-    does, through the content cache. With `includeThumbnails` it also fetches
+  ledger. Each file's JSON holds its ML data and, for an image (for a live
-    thumbnails. It waits for an ML data fetch, then rebuilds the backup tree. It
+  photo, its image), its original's EXIF and XMP, with its dimensions for a JPEG
-    records each file that failed in `failures.json`.
+  only; a video's JSON holds none of these three. A fetched original is written
-
+  straight to its save path and not into the cache, which then counts it as
-    Each file's JSON holds its ML data and keywords. An image's JSON also holds
+  present; one the cache already held is copied from there. `BackupOptions`:
-    the EXIF and XMP of its original, and its dimensions if it is a JPEG. A live
+  `downloadDirectory` (falls back to the library's), `includeOriginals` (default
-    photo's JSON holds these for its image. A video's JSON holds no EXIF, XMP or
+  `true`), `includeThumbnails` (default `false`), `onlyAlbumNames`, `verify`
-    dimensions.
+  (default `false`), `onProgress`, and `lock`. See Backup layout above for the
-
+  tree it writes, and for the albums `BackupResult` lists in
-    A fetched original is written straight to its save path, not into the cache.
+  `undecryptableAlbums` and `failedAlbums`. Whether the backup took the lock or
-    The cache then counts it as present. An original that the cache already held
+  its caller did, once the lock is lost the backup rejects with
-    is copied from there.
+  `lost the lock on <dir>: <reason>` before it starts another file.
    `BackupOptions` holds:
    - `downloadDirectory`, which falls back to the library's
    - `includeOriginals`, `true` by default
    - `includeThumbnails`, `false` by default
    - `onlyAlbumNames`
    - `verify`, `false` by default
    - `onProgress`
    - `lock`
    "Backup layout" above describes the tree that the backup writes. It also
    describes the albums that `BackupResult` lists in `undecryptableAlbums` and
    `failedAlbums`. Once the lock is lost, the backup rejects with
    `lost the lock on <dir>: <reason>` before it starts another file. This holds
    whether the backup or its caller took the lock.
 ### Request pools
@@ -1506,14 +1364,6 @@ is rewritten in TypeScript in this repository. Protocol fidelity is verified
 against the upstream implementations in `web/packages/base/`,
 `mobile/apps/photos/lib/`, and `cli/`.
 The keywords come from Ente too. `src/clip-keyword-vectors.ts` holds the
 Discover categories of Ente's photos app, from
 `mobile/apps/photos/assets/discover.json`, each with its query's text embedding
 from Ente's CLIP text model. `bin/clip-keyword-vectors` writes that file and the
 CLIP embedding of a public-domain photo that the tests use. It runs Ente's
 models in Docker, with every download pinned by sha256. It is run by hand only,
 followed by `make fmt`.
 ## For LLMs
 If you are an LLM agent working on this repository, read and follow these
@@ -26,33 +26,6 @@ declares one.
 # Completed Steps
 - 2026-10-25: `quak files COLLECTION` fetches the files of that collection alone
  (https://git.eeqj.de/sneak/quak/issues/217). It used to wait for a refresh,
  which on an empty cache fetched the files of every collection first. It now
  reads the collection list through `lib.freshCollections()`, then brings that
  one collection up to date through the new `lib.refreshCollection()`. That
  stores and saves its files as a refresh would, and leaves the refresh cursor
  where it was. When the stored copy is current, it asks for none of the files.
  It never runs at the same time as a refresh. Once a refresh has received the
  account's collections, it stores no collection the cache does not hold, and
  `quak files COLLECTION` waits for a refresh instead. A refresh from a cursor
  of 0 replaces all the cache holds, so collections keep the server's order. A
  library opened on a cache that only `lib.refreshCollection()` wrote awaits its
  first refresh. `quak files` with no argument still waits for a refresh. The
  store lists what did not decrypt by collection ID and file ID.
 - 2026-10-22: The JSON `quak backup` and `quak backup-metadata` write for a file
  holds `keywords` in place of the CLIP embedding in its ML data
  (https://git.eeqj.de/sneak/quak/issues/218). The keywords are the titles of
  the Discover categories of Ente's photos app that the file falls in, by the
  app's rule: the cosine similarity of the file's CLIP embedding and the text
  embedding of a category's query is at least the category's minimum score, and
  videos stay out of the categories that leave them out. `src/clip-keywords.ts`
  applies the rule. `src/clip-keyword-vectors.ts` holds the 16 categories with
  their text embeddings. `bin/clip-keyword-vectors` writes it with Ente's CLIP
  text model, and writes the CLIP embedding of a public-domain photo of a sunset
  that the tests use.
 - 2026-10-18: `-v`/`--verbose` raises the CLI's log level once for each repeat,
  and `-q`/`--quiet` prints only fatal errors
  (https://git.eeqj.de/sneak/quak/issues/212). The levels are fatal, error,
@@ -1,31 +0,0 @@
 #!/bin/sh
 # Writes src/clip-keyword-vectors.ts and test/clip-keywords-sunset.json by
 # running bin/clip-keyword-vectors.py in a Python image pinned by digest, with
 # its packages pinned by hash. Run it by hand from a checkout, then `make fmt`;
 # no gate runs it. Besides the Python image, it downloads about 265 MB, most of
 # it Ente's two CLIP models.
 set -eu
 ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
 # python:3.13-slim (Python 3.13.17 on Debian 13.7), 2026-10-21. The wheels
 # below are the ones for this image on linux/amd64.
 IMAGE=python@sha256:57b29a7c050c4e679e4bea572e14b3965cf4b5839de2da49d55e49ffc4024f39
 main() {
    cd "$ROOT"
    docker run --rm -i --platform linux/amd64 \
        --user "$(id -u):$(id -g)" -e HOME=/tmp \
        -v "$ROOT:/repo" -w /repo "$IMAGE" sh -c '
            python -m venv /tmp/venv &&
            /tmp/venv/bin/pip install --quiet --disable-pip-version-check \
                --no-cache-dir --no-deps --require-hashes -r /dev/stdin &&
            /tmp/venv/bin/python bin/clip-keyword-vectors.py' <<'EOF'
 numpy==2.5.3 --hash=sha256:a5fa86b80fd24bcd1aff83ad23be44ea323de3f787be8f8b15d4a65621e25321
 onnxruntime==1.30.0 --hash=sha256:86f940afc801ea9681a4da8af84fbe95e1d9ea7d80903952cc1bfad54faad38f
 pillow==12.3.0 --hash=sha256:0847a763afefb695bc912d7c131e7e0632d4edc1d8698f58ddabec8e46b8b6d3
 tokenizers==0.23.2 --hash=sha256:41c2f84d172449b4dadb9cdc508e3e364076613c35b16e76ecfe47a60d1e3305
 EOF
 }
 main "$@"
@@ -1,158 +0,0 @@
 """Write src/clip-keyword-vectors.ts and test/clip-keywords-sunset.json.
 bin/clip-keyword-vectors runs this in a pinned Python image. It downloads
 Ente's Discover list, Ente's CLIP text and image models, the CLIP tokenizer
 and a public-domain photo of a sunset, checks each against its sha256, and
 writes:
 - src/clip-keyword-vectors.ts: each Discover category of Ente's photos app,
  with the text embedding Ente's CLIP text model gives its query;
 - test/clip-keywords-sunset.json: the CLIP embedding Ente's image model gives
  the photo, prepared as Ente's apps prepare a photo.
 Both embeddings are scaled to length 1, as Ente's apps scale them.
 """
 import hashlib
 import io
 import json
 import urllib.request
 import numpy as np
 import onnxruntime
 from PIL import Image, ImageOps
 from tokenizers import Tokenizer
 ENTE_COMMIT = "f5ad70a860ed25d0c8057b0efb4bd6eaefe4b0c5"
 DISCOVER_PATH = "mobile/apps/photos/assets/discover.json"
 DISCOVER_URL = (
    f"https://raw.githubusercontent.com/ente-io/ente/{ENTE_COMMIT}/{DISCOVER_PATH}"
 )
 DISCOVER_SHA256 = "cf70ac7116b592f7921ca4cf67cdbb421a8e6b287fbe44b2be678b8d198e5c24"
 TEXT_MODEL = "mobileclip_s2_text_opset18_quant.onnx"
 TEXT_MODEL_SHA256 = "d92f33dfcff83077fc2e0d3414250710efbb51795dfd89767bdbefb5fdc47322"
 IMAGE_MODEL = "mobileclip_s2_image_gelu_opset20.onnx"
 IMAGE_MODEL_SHA256 = "205a430af825e501c5138e5bb9abea942482a7a4fd4a680e98e47cf0830dce7e"
 # The CLIP tokenizer Hugging Face publishes for OpenAI's CLIP. Its vocabulary
 # and merges are those of bpe_simple_vocab_16e6.txt, the vocabulary Ente's
 # apps tokenize with.
 TOKENIZER_URL = (
    "https://huggingface.co/openai/clip-vit-base-patch32/resolve/"
    "3d74acf9a28c67741b2f4f2ea7635f0aaf6f0268/tokenizer.json"
 )
 TOKENIZER_SHA256 = "b556ac8c99757ffb677208af34bc8c6721572114111a6e0aaf5fa69ff0b8d842"
 # "Sunset off the Massachusetts coast", a NOAA photo in the public domain:
 # https://commons.wikimedia.org/wiki/File:Sunset_off_the_Massachusetts_coast_-_NOAA.jpg
 PHOTO_URL = (
    "https://upload.wikimedia.org/wikipedia/commons/d/db/"
    "Sunset_off_the_Massachusetts_coast_-_NOAA.jpg"
 )
 PHOTO_SHA256 = "be62f3289c9bf7b75af68cd6978021d54e8a531d5d4cc493f6e9fbf5e1ab74d3"
 # Ente's text model takes 77 token ids, padded with 0; its image model takes
 # a 256x256 RGB image.
 TOKEN_COUNT = 77
 IMAGE_SIZE = 256
 def download(url, sha256):
    # Wikimedia refuses requests without a User-Agent.
    request = urllib.request.Request(url, headers={"User-Agent": "quak"})
    with urllib.request.urlopen(request) as response:
        data = response.read()
    digest = hashlib.sha256(data).hexdigest()
    if digest != sha256:
        raise SystemExit(f"{url} has sha256 {digest}, not {sha256}")
    return data
 def ente_model(name, sha256):
    return onnxruntime.InferenceSession(
        download(f"https://models.ente.com/{name}", sha256),
        providers=["CPUExecutionProvider"],
    )
 def run(session, tensor):
    (output,) = session.run(None, {session.get_inputs()[0].name: tensor})
    embedding = output[0]
    return embedding / np.linalg.norm(embedding)
 def text_embedding(session, tokenizer, query):
    ids = tokenizer.encode(query).ids
    ids += [0] * (TOKEN_COUNT - len(ids))
    return run(session, np.array([ids], dtype=np.int32))
 def image_embedding(session, photo):
    image = ImageOps.exif_transpose(Image.open(io.BytesIO(photo))).convert("RGB")
    # Scale to cover IMAGE_SIZE x IMAGE_SIZE and crop the centre.
    square = ImageOps.fit(image, (IMAGE_SIZE, IMAGE_SIZE), Image.Resampling.BILINEAR)
    pixels = np.asarray(square, dtype=np.float32) / 255
    return run(session, pixels.transpose(2, 0, 1)[np.newaxis])
 def numbers(embedding):
    return ", ".join(str(value) for value in embedding)
 def write_categories(prompts, embeddings):
    lines = [
        "// Written by bin/clip-keyword-vectors; do not edit by hand.",
        "//",
        "// The Discover categories of Ente's photos app, in their order, from",
        f"// {DISCOVER_PATH} in https://github.com/ente-io/ente",
        f"// at commit {ENTE_COMMIT}. Each has the text",
        f"// embedding Ente's CLIP text model ({TEXT_MODEL})",
        "// gives its query, scaled to length 1. `showVideo` is false for a category",
        "// that leaves out videos.",
        "",
        "export const DISCOVER_CATEGORIES = [",
    ]
    for prompt, embedding in zip(prompts, embeddings):
        lines += [
            "    {",
            f"        title: {json.dumps(prompt['title'])},",
            f"        query: {json.dumps(prompt['query'])},",
            f"        minScore: {json.dumps(prompt['minScore'])},",
            f"        showVideo: {json.dumps(prompt.get('showVideo', True))},",
            f"        textEmbedding: [{numbers(embedding)}],",
            "    },",
        ]
    lines.append("];")
    with open("src/clip-keyword-vectors.ts", "w", encoding="utf-8") as file:
        file.write("\n".join(lines) + "\n")
 def write_fixture(embedding):
    with open("test/clip-keywords-sunset.json", "w", encoding="utf-8") as file:
        file.write(
            "{\n"
            f'    "photo": {json.dumps(PHOTO_URL)},\n'
            f'    "sha256": {json.dumps(PHOTO_SHA256)},\n'
            f'    "embedding": [{numbers(embedding)}]\n'
            "}\n"
        )
 def main():
    prompts = json.loads(download(DISCOVER_URL, DISCOVER_SHA256))["prompts"]
    tokenizer = Tokenizer.from_str(
        download(TOKENIZER_URL, TOKENIZER_SHA256).decode("utf-8")
    )
    text_model = ente_model(TEXT_MODEL, TEXT_MODEL_SHA256)
    embeddings = [
        text_embedding(text_model, tokenizer, prompt["query"]) for prompt in prompts
    ]
    write_categories(prompts, embeddings)
    image_model = ente_model(IMAGE_MODEL, IMAGE_MODEL_SHA256)
    write_fixture(image_embedding(image_model, download(PHOTO_URL, PHOTO_SHA256)))
 if __name__ == "__main__":
    main()
@@ -14,9 +14,9 @@
 //         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, with
-//                                          the file's ML data, its
+//                                          the file's ML data and its
-//                                          keywords, and its original's
+//                                          original's EXIF, XMP and
-//                                          EXIF, XMP and dimensions
+//                                          dimensions
 //         collections/<name>/<title>       symlink to the original
 //         collections/<name>.json          per-collection metadata
 //         account.json                     the account's email and user ID
@@ -77,7 +77,6 @@ import { readFile } from "node:fs/promises";
 import { dirname, extname, join, relative, resolve } from "node:path";
 import lockfile from "proper-lockfile";
 import { clipKeywords } from "./clip-keywords.js";
 import { removeLeftoverTempFiles } from "./download/index.js";
 import { describeError } from "./errors.js";
 import {
@@ -498,9 +497,8 @@ const imageMetadataFor = async (
    }
 };
-// The file's JSON: its basic fields, its magic metadata, its ML data without
+// The file's JSON: its basic fields, its magic metadata, its ML data or the
-// the CLIP embedding and the keywords that embedding gives, or the reason the
+// reason the ML data is missing, and its image metadata.
 // ML data is missing, and its image metadata.
 const writeSidecar = (
    path: string,
    file: EnteFile,
@@ -516,13 +514,7 @@ const writeSidecar = (
    };
    if (file.magicMetadata) meta.magicMetadata = file.magicMetadata;
    if (file.pubMagicMetadata) meta.pubMagicMetadata = file.pubMagicMetadata;
-    if (ml.mlData) {
+    if (ml.mlData) meta.mlData = ml.mlData;
        const { clip: _clip, ...mlDataWithoutClip } = ml.mlData;
        meta.mlData = mlDataWithoutClip;
        const isVideo = file.metadata.fileType === "video";
        const keywords = clipKeywords(ml.mlData, isVideo);
        if (keywords) meta.keywords = keywords;
    }
    if (ml.mlDataError) meta.mlDataError = ml.mlDataError;
    if (image.imageMetadata) meta.imageMetadata = image.imageMetadata;
    if (image.imageMetadataError) {
@@ -128,14 +128,12 @@ const readLibraryClient = (client: Client): LibraryClient => ({
    contentSource: () => client.contentSource(),
 });
-// Open a library for a single point command. The aggressive background
+// Open a library for a single point command: the aggressive background precache
-// precache (issue #48) is off, because a one-shot `collections` or `get` must
+// (issue #48) is off — a one-shot `collections` or `get` must not start
-// not start downloading the whole account. No refresh starts as it opens or on
+// downloading the whole account — and no refresh starts as it opens or on a
-// a timer. Each command asks for the refresh it needs. `collections` needs none
+// timer: each command asks for the one it needs, and `collections` needs none
-// (issue #210). `files COLLECTION` needs one only when `refreshCollection()`
+// (issue #210). While a refresh runs, each collection whose files it has
-// resolves to `false` (issue #217). While a refresh runs,
+// fetched is logged, so a large account shows progress rather than nothing.
 // each collection whose files it has fetched is logged, so a large account
 // shows progress rather than nothing.
 const openReadLibrary = (ctx: CliContext, client: Client): Promise<Library> =>
    Library.open({
        client: readLibraryClient(client),
@@ -2,42 +2,33 @@
 //
 // `collections`, `files`, `get`, and `get-thumb` must answer for
 // the account's state at the moment the command runs, not for whatever the
-// local cache last happened to hold (owner amendment, issue #36). `files`
+// local cache last happened to hold (owner amendment, issue #36). `files`,
-// without a collection ID, `get` and `get-thumb` therefore force a server
+// `get` and `get-thumb` therefore force a server round-trip through
-// round-trip through `Library.fresh()`, and only then read. A collection, file,
+// `Library.fresh()` and only then read — so a collection, file, or metadata
-// or metadata change made elsewhere is then visible. `collections` asks the
+// change made elsewhere is visible. `collections` asks the library for the
-// library for the collection list alone through `Library.freshCollections()`
+// collection list alone through `Library.freshCollections()` (issue #210): a
-// (issue #210). A refresh would also fetch the files of every collection, which
+// refresh would also fetch the files of every collection, which on a large
-// `collections` does not print, and on a large account that takes long.
+// account takes long and which `collections` does not print.
 // `files COLLECTION` reads the collection list the same way, for the same
 // reason. It then brings that one collection up to date through
 // `Library.refreshCollection()` (issue #217), and fetches no other collection's
 // files. Once a refresh has received the account's collections,
 // `refreshCollection()` stores no collection the library does not hold.
 // `files COLLECTION` then forces a refresh instead.
 //
-// `collections` lists in the server's order. `files` lists in the library's
+// `collections` lists in the server's order and `files` in the library's own
-// own enumeration order: `listCollections()`, then `listFiles()` for each.
+// enumeration order (`listFiles()`), the orders the pre-library CLI printed,
-// Those are the orders the pre-library CLI printed. The `albums`/`photos`
+// rather than the `albums`/`photos` projection's newest-first order, which
-// projection would re-sort the rows newest first. After a refresh, the
+// re-sorts the rows. The field values still come from each record's raw
-// library holds collections in the order the server first sent them. The
+// metadata via `cli-output.ts`. `files` without a collection ID lists every
-// field values still come from each record's raw metadata via
+// file in the account once (issue #211): the library keeps a record of a file
-// `cli-output.ts`. `files` without a collection ID lists every file in the
+// for each collection that holds it, and only the first collection's record is
-// account once (issue #211).
+// listed.
 // The library keeps a record of a file for each collection that holds it, and
 // only the first collection's record is listed.
 import type { Collection, EnteFile } from "./model/types.js";
 import type { Photo, PhotosAPI } from "./library/index.js";
 // The slice of `Library` these helpers read. `Library` satisfies it
-// structurally. A test can drive them with a stand-in that records the
+// structurally; a test can drive them with a stand-in that records the
-// `fresh()`, `freshCollections()` and `refreshCollection()` calls. The
+// `fresh()` and `freshCollections()` calls and serves records in a known
-// stand-in serves records in a known enumeration order.
+// enumeration order.
 export interface FreshReadLibrary {
    fresh(): Promise<unknown>;
    freshCollections(): Promise<Collection[]>;
    refreshCollection(collection: Collection): Promise<boolean>;
    getCollection(id: number): Collection | undefined;
    listCollections(): Collection[];
    listFiles(collectionID: number): EnteFile[];
@@ -51,29 +42,21 @@ export const freshCollections = (
    lib: FreshReadLibrary,
 ): Promise<Collection[]> => lib.freshCollections();
-// The files of one collection, in enumeration order. `undefined` (not an empty
+// The files of one collection, current as of a forced refresh, in enumeration
-// list) when the collection does not exist, so the caller can tell "no such
+// order. `undefined` (not an empty list) when the collection does not exist, so
-// collection" from "an empty collection". They are current as of one
+// the caller can tell "no such collection" from "an empty collection". Without
-// collections request and the requests that bring that collection alone up to
+// a collection ID, every file in the account, each once, as held by the first
-// date. When `refreshCollection()` resolves to `false`, they are current as of
+// collection that holds it.
 // a forced refresh instead. Without a collection ID, every file in the account,
 // current as of a forced refresh. Each file is listed once, as held by the
 // first collection that holds it.
 export const freshFiles = async (
    lib: FreshReadLibrary,
    collectionID?: number,
 ): Promise<EnteFile[] | undefined> => {
    if (collectionID !== undefined) {
        const collections = await lib.freshCollections();
        const collection = collections.find((c) => c.id === collectionID);
        if (!collection) return undefined;
        if (!(await lib.refreshCollection(collection))) {
            await lib.fresh();
            if (!lib.getCollection(collectionID)) return undefined;
        }
        return lib.listFiles(collectionID);
    }
    await lib.fresh();
    if (collectionID !== undefined) {
        return lib.getCollection(collectionID)
            ? lib.listFiles(collectionID)
            : undefined;
    }
    const listed = new Set<number>();
    const files: EnteFile[] = [];
    for (const collection of lib.listCollections()) {
@@ -1,57 +0,0 @@
 // Keywords for a file from its CLIP embedding.
 //
 // Ente stores no keywords. A file's ML data holds a CLIP embedding, the 512
 // numbers Ente's image model gave the photo, and Ente's photos app sorts files
 // into the categories of its Discover section with it: a file falls in a
 // category when the cosine similarity of its CLIP embedding and the text
 // embedding of the category's query is at least the category's `minScore`,
 // unless the file is a video and the category leaves out videos. A file's
 // keywords are the titles of the categories it falls in. The categories and
 // their text embeddings are in `clip-keyword-vectors.ts`.
 import { DISCOVER_CATEGORIES } from "./clip-keyword-vectors.js";
 import { clipEmbedding } from "./library/mldata.js";
 import type { MLData } from "./mldata-fetch.js";
 // How many numbers a CLIP embedding from Ente's image model has.
 const EMBEDDING_LENGTH = 512;
 const norm = (vector: number[]): number => Math.hypot(...vector);
 const cosineSimilarity = (a: number[], b: number[]): number => {
    let dot = 0;
    a.forEach((value, i) => {
        dot += value * (b[i] ?? 0);
    });
    return dot / (norm(a) * norm(b));
 };
 // The titles of the Discover categories a file falls in, highest score first,
 // or undefined when its ML data has no CLIP embedding of 512 finite numbers
 // that are not all zero. Tests pass their own `categories`.
 export const clipKeywords = (
    mlData: MLData,
    isVideo: boolean,
    categories = DISCOVER_CATEGORIES,
 ): string[] | undefined => {
    const embedding = clipEmbedding(mlData);
    if (
        !embedding ||
        embedding.length !== EMBEDDING_LENGTH ||
        norm(embedding) === 0
    ) {
        return undefined;
    }
    const matches: { title: string; score: number }[] = [];
    for (const category of categories) {
        if (isVideo && !category.showVideo) continue;
        const score = cosineSimilarity(embedding, category.textEmbedding);
        if (score >= category.minScore) {
            matches.push({ title: category.title, score });
        }
    }
    return matches
        .sort((a, b) => b.score - a.score)
        .map((match) => match.title);
 };
@@ -1,37 +1,28 @@
 // The library surface over the local cache.
 //
 // `Library.open()` loads the on-disk metadata store (issue #41), then starts
-// the refresh loop. When the stored cursor is 0, `open()` awaits the first
+// the refresh loop. When the cache loaded empty it awaits the first refresh,
-// refresh. No refresh has then stored any collection: the cache is empty, or
+// so the library never opens onto an empty store it could have filled; when an
-// holds only what `refreshCollection()` stored. The library must not serve
+// existing copy loaded, that first refresh runs in the background and `open()`
-// that as the whole account. Otherwise that first refresh runs in the
+// returns as soon as the cached data is ready to serve — a slow or unreachable
-// background. `open()` returns as soon as the cached data is ready to serve,
+// server no longer stalls opening. A background timer then refreshes every
-// so a slow or unreachable server does not stall opening. A background timer
+// `refreshIntervalSeconds`. Every default read is answered from RAM — no
-// then takes a turn `refreshIntervalSeconds` after its last turn ends. Each
+// default read touches the network. There is deliberately no `sync()`, no
-// turn starts a refresh, unless a refresh or `refreshCollection()` is already
+// `refresh()`, no `serverReachable` flag, and no "before each read" mode
-// running. Every default read is answered from RAM — no default read touches
+// (design #36).
 // the network. There is deliberately no `sync()`, no `refresh()`, no
 // `serverReachable` flag, and no "before each read" mode (design #36).
 //
-// `fresh()` is an exception (issue #75, an owner amendment to #36). It awaits
+// `fresh()` is the one exception (issue #75, an owner amendment to #36): it
-// a refresh, and only then hands back the read namespaces. A caller that needs
+// forces a refresh, awaits it, and only then hands back the read namespaces, so
-// server-current data uses it. Concurrent `fresh()` calls coalesce onto one
+// a caller that needs server-current data can ask for it. Concurrent `fresh()`
-// in-flight refresh. A refresh that fails rejects the caller. The default
+// calls coalesce onto one in-flight refresh, and a refresh that fails rejects
-// reads stay silent and serve the last good copy. The default methods and the
+// the caller (the default reads stay silent and serve the last good copy). The
-// background loop are unchanged.
+// default methods and the background loop are unchanged.
 //
 // `freshCollections()` is the fresh read of the collection list alone (issue
-// #210). It sends one collections request and stores nothing.
+// #210): one collections request, no collection's files, and nothing stored,
-// `quak collections` uses it. `refreshCollection()` brings one collection
+// for a caller such as `quak collections` that needs no more. A caller that
-// from that list up to date in the store (issue #217). It fetches that
+// asks for each refresh it needs can also open the library with
-// collection's files alone, as a refresh would. `quak files COLLECTION` uses
+// `refreshOnOpen: false`, so that `open()` starts none.
 // it. It never runs at the same time as a refresh. Once the stored cursor is
 // past 0, it only updates a collection the store holds, and only a refresh
 // adds one. A refresh from a stored cursor of 0 replaces all the store holds.
 // So after a refresh, the store holds collections in the order the server
 // first sent them. A caller that asks for
 // each refresh it needs can also open the library with `refreshOnOpen: false`,
 // so that `open()` starts none.
 //
 // A refresh reports through `onProgress` each collection whose files it has
 // fetched, so a large account, whose first refresh fetches the files of every
@@ -40,12 +31,10 @@
 // A refresh stages all of its network work first and only mutates the store
 // once every fetch has succeeded. A refresh that fails partway therefore never
 // becomes visible to reads: the last good snapshot stays in place, and the
-// failure surfaces through `onProgress` and `status()` instead. A save can
+// failure surfaces through `onProgress` and `status()` instead. A commit that
-// still fail after the store has changed in RAM. The store then stays marked
+// mutates RAM but then fails to persist keeps `status().lastError` set and the
-// unsaved until a later save lands. Until then, every `commit()` retries the
+// store marked unsaved until a later save actually lands, so a stuck disk is
-// save. A refresh whose save fails sets `status().lastError`, which stays set
+// never masked by a subsequent empty refresh.
 // until a later refresh succeeds. `refreshCollection()` never sets or clears
 // it. So a stuck disk is never hidden by a later refresh that changes nothing.
 import { rm } from "node:fs/promises";
 import { join, resolve } from "node:path";
@@ -170,23 +159,21 @@ export interface LibraryClient {
        payloads: Map<number, MLData>;
        errors: Map<number, unknown>;
    }>;
-    // The byte source for the on-disk content cache. Optional, so a mock
+    // The byte source for the on-disk content cache. Optional so a mock client
-    // client that only serves metadata still satisfies the interface. Without
+    // that only serves metadata still satisfies the interface; when absent (and
-    // it, and with no `contentSource` passed to `open`, the content cache is
+    // no explicit `contentSource` is passed to `open`) the content cache is
-    // disabled. `Photo.original`/`thumbnail` and `thumbnails.ensure` then
+    // disabled and `Photo.original`/`thumbnail` and `thumbnails.ensure` throw.
    // throw.
    contentSource?(): ContentSource;
 }
-// A progress event for one unit of background work. A metadata "refresh" and
+// A progress event for one unit of background work. A metadata "refresh" or an
-// an ML "fetchMLData" pass each fire "started" before their network work. Each
+// ML "fetchMLData" pass each fire "started" before their network work and then
-// then fires exactly one of "done" or "failed". A "failed" event carries the
+// exactly one of "done" or "failed"; "failed" carries the error message and
-// error message. An ML "done" reports in `fetched` how many payloads it
+// an ML "done" reports how many payloads it stored and, in `mlDataErrors`,
-// stored. Its `mlDataErrors` lists each file whose ML data did not decrypt,
+// each file whose ML data did not decrypt, gunzip or parse, with the reason.
-// gunzip or parse, with the reason. In between, a refresh fires "progress"
+// In between, a refresh fires "progress" after each collection whose files it
-// after each collection whose files it fetched. Its `fetched` is how many
+// fetched: `fetched` is how many collections it has fetched the files of so
-// collections it has fetched the files of so far, and `total` how many it
+// far, `total` how many it will. The precache fills
 // will. The precache fills
 // ("precacheThumbnails"/"precacheOriginals", #48) fire "started"/"done" around
 // each sweep that has work, "done" reporting the count newly cached.
 export interface RefreshEvent {
@@ -214,10 +201,9 @@ export interface LibraryOptions {
    // directory at open. The content cache treats an original already stored
    // at its save path as present.
    downloadDirectory?: string;
-    // How long after its last turn ends the background timer takes the next.
+    // How long after one refresh ends the background timer starts the next.
-    // A turn starts a refresh unless a refresh or `refreshCollection()` is
+    // `Infinity` starts none: the library then refreshes only as it opens and
-    // running. With `Infinity` the timer takes no turn: the library then
+    // when `fresh()` or `backup()` asks.
    // refreshes only as it opens and when `fresh()` or `backup()` asks.
    refreshIntervalSeconds?: number;
    // Whether `open()` starts a refresh. Defaults to true. With false, `open()`
    // returns at once onto what the cache holds, empty or not, and a refresh
@@ -256,9 +242,8 @@ export interface LibraryStatus {
    // Wall-clock ms of the last refresh that succeeded, or undefined if none
    // has yet.
    lastRefreshAt?: number;
-    // The error of the most recent refresh, set only when it failed. The next
+    // The message from the most recent refresh, set only while that refresh
-    // refresh that succeeds clears it. `refreshCollection()` never sets or
+    // failed; cleared by the next success.
    // clears it.
    lastError?: string;
    // Wall-clock ms of the last ML fetch pass that succeeded, or undefined if
    // none has yet (or ML fetching is disabled).
@@ -321,17 +306,12 @@ export class Library {
    private readonly precache?: Precache;
    private timer?: ReturnType<typeof setTimeout>;
-    // The in-flight refresh cycle or `refreshCollection()`, or undefined when
+    // The in-flight refresh cycle, or undefined when none runs. One slot serves
-    // neither runs. One slot holds both, so they never run at the same time.
+    // both paths: the background loop skips when it is set, and a fresh read
-    // The background loop skips while it is set. A fresh read (issue #75)
+    // (issue #75) coalesces onto it or starts one. The promise carries the
-    // coalesces onto a running refresh. It waits for a running
+    // cycle's real outcome (it rejects on failure); the background loop ignores
-    // `refreshCollection()` to end, and then joins or starts a refresh. The
+    // that, a fresh read propagates it.
    // promise carries the real outcome: it rejects on failure. The background
    // loop ignores a failure. A fresh read passes on the failure of the
    // refresh it joins or starts, and `refreshCollection()` passes on its own.
    private cycle?: Promise<void>;
    // Whether `cycle` is a refresh cycle rather than a `refreshCollection()`.
    private cycleIsRefresh = false;
    // Guards the ML fetch pass so a slow backfill never runs twice at once; a
    // refresh whose pass is still running kicks nothing new. Holds the running
    // pass, so `close()` and `backup()` can wait for it. It rejects when the
@@ -344,20 +324,19 @@ export class Library {
    private lastMLError?: string;
    // For each file whose ML data the last ML fetch pass that succeeded got
    // but could not decrypt, gunzip or parse, why not, by fileID. A pass
-    // gathers its own and puts them here only when it ends without failing.
+    // gathers its own and puts them here when it ends without failing, so
-    // So `status()` and `backup()` never see the list of a pass still running
+    // `status()` and `backup()` never see the list of a pass that is still
-    // or one that failed. Kept in RAM only, never in the cache.
+    // running or that failed. Kept in RAM only, never in the cache.
    private mlDataErrors = new Map<number, unknown>();
-    // The plain-record projection as of the last store change, and the GUI
+    // The plain-record projection as of the last refresh, and the GUI change
-    // change subscribers. A refresh or `refreshCollection()` that alters the
+    // subscribers. A refresh that alters the projection notifies each with the
-    // projection notifies each subscriber with the delta. `lastRecords`
+    // delta; `lastRecords` is kept current every refresh so a subscriber that
-    // advances on each `commit()` that changes the store. A subscriber that
+    // joins later diffs against the state its own `snapshot()` already returned.
    // joins later then diffs against the state its own `snapshot()` returned.
    private readonly subscribers = new Set<(change: LibraryChange) => void>();
    private lastRecords: DerivedRecords;
    // RAM holds changes disk has not yet accepted (an earlier save failed).
-    // Cleared only when a save succeeds. Until then, every `commit()` retries
+    // Cleared only when a save actually succeeds; keeps the store trying to
-    // the save.
+    // persist and the failure visible in `status()` until then.
    private unsaved = false;
    private constructor(args: {
@@ -387,7 +366,7 @@ export class Library {
        this.lastRecords = this.deriveNow();
        // The read namespaces derive fresh from the store on each call, so they
-        // always reflect what it holds now.
+        // always reflect the latest refresh.
        const derive = (): DerivedRecords => this.deriveNow();
        const root = this.downloadDirectory;
        const saves: SavePathLookup = {
@@ -414,16 +393,14 @@ export class Library {
        this.mldata = makeMLDataAPI(() => this.mlStore);
    }
-    // Load the cache and start the refresh loop. When the stored cursor is 0,
+    // Load the cache and start the refresh loop. With an empty cache the first
-    // the first refresh is awaited. Such a cache is empty, or holds only what
+    // refresh is awaited, so `open()` resolves onto populated data whenever the
-    // `refreshCollection()` stored. `open()` then resolves onto the whole
+    // server is reachable; that awaited refresh may still fail, and the library
-    // account whenever the server is reachable. If that refresh fails, the
+    // then opens empty with the failure recorded in `status()`. With an
-    // library opens onto what the cache holds, with the failure recorded in
+    // existing cache the first refresh runs in the background and `open()`
-    // `status()`. With any other cache the first refresh runs in the
+    // returns as soon as the cached data is ready — an unreachable server does
-    // background, and `open()` returns as soon as the cached data is ready.
+    // not block opening. With `refreshOnOpen: false` there is no first
-    // An unreachable server then does not block opening. With
+    // refresh: `open()` returns onto the cache as it is.
    // `refreshOnOpen: false` there is no first refresh: `open()` returns onto
    // the cache as it is.
    static async open(opts: LibraryOptions): Promise<Library> {
        const { userID } = opts.client.whoami();
        const cacheDirectory =
@@ -439,8 +416,8 @@ export class Library {
        let store = await MetadataStore.load(metadataPath);
        // A cache directory given explicitly can hold another account's cache.
        // Its records and cursor are not this account's, so delete it and the
-        // ML data beside it and start empty. A user ID of 0 means nothing was
+        // ML data beside it and start empty. A user ID of 0 means the cache
-        // ever stored there, so there is nothing to discard.
+        // was never refreshed and so holds nothing to discard.
        if (store.userID !== 0 && store.userID !== userID) {
            await rm(metadataPath, { force: true });
            await rm(join(cacheDirectory, "mldata"), {
@@ -463,11 +440,10 @@ export class Library {
            ? await MLDataStore.open(join(cacheDirectory, "mldata"))
            : undefined;
-        // Build the content cache from an explicit source or the client's own.
+        // Build the content cache from an explicit source or the client's own,
-        // Take its record of what is already cached, and reap orphan temp
+        // and take its record of what is already cached (and reap orphan temp
-        // files, before the first projection. Cached paths are then present
+        // files) before the first projection, so cached paths are present from
-        // from the start, and the first `commit()` raises no spurious
+        // the start and the first refresh raises no spurious path-change diff.
        // path-change diff.
        const source = opts.contentSource ?? opts.client.contentSource?.();
        let cache: ContentCache | undefined;
        let precache: Precache | undefined;
@@ -521,26 +497,22 @@ export class Library {
            precache,
        });
-        // Start filling from whatever the loaded store already holds. Each
+        // Start filling from whatever the loaded store already holds; each
-        // later `commit()` re-kicks the fills with its new files, and retries
+        // refresh below re-kicks with the new files (and retries any that
-        // any that failed. An empty store starts empty here, and fills once a
+        // failed). An empty store starts empty here and fills after its first
-        // `commit()` stores files.
+        // refresh.
        precache?.start();
        if (opts.refreshOnOpen === false) {
            // The caller asks for each refresh it needs.
            lib.scheduleNext();
-        } else if (store.collectionsSinceTime > 0) {
+        } else if (store.loadedFromDisk) {
-            // The stored cursor has moved, so a refresh has stored the
+            // An existing copy already answers reads; refresh in the background
-            // account's collections and the cache's copy answers reads.
+            // and start the interval once that first cycle settles.
            // Refresh in the background, and start the interval once that
            // first cycle settles.
            void lib.runRefresh().then(() => lib.scheduleNext());
        } else {
-            // The stored cursor is still 0, so no refresh has stored any
+            // Nothing was cached: wait for the first refresh to fill the store
-            // collection: the cache is empty, or holds only what
+            // (or fail) rather than resolve onto an empty library.
            // `refreshCollection()` stored. Wait for the first refresh to fill
            // the store (or fail) rather than resolve onto part of the account.
            await lib.runRefresh();
            lib.scheduleNext();
        }
@@ -578,9 +550,9 @@ export class Library {
        return snapshotFrom(this.deriveNow(), Date.now());
    }
-    // Deliver a `LibraryChange` whenever a refresh or `refreshCollection()`
+    // Deliver a `LibraryChange` whenever a refresh alters the projection. A
-    // alters the projection. One that changes nothing delivers nothing. The
+    // refresh that changes nothing delivers nothing. The returned handle's
-    // returned handle's `unsubscribe` stops delivery.
+    // `unsubscribe` stops delivery.
    subscribe(args: { onChange: (change: LibraryChange) => void }): {
        unsubscribe: () => void;
    } {
@@ -623,13 +595,12 @@ export class Library {
        };
    }
-    // Fresh reads (issue #75, owner amendment to design #36). Wait for a
+    // Fresh reads (issue #75, owner amendment to design #36). Force a refresh,
-    // refresh to complete and persist, then hand back the same
+    // wait for it to complete and persist, then hand back the same
-    // `albums`/`photos`/`timeline` namespaces. They then reflect a completed
+    // `albums`/`photos`/`timeline` namespaces — now guaranteed to reflect a
-    // server round-trip. A running `refreshCollection()` is waited for first.
+    // completed server round-trip. Concurrent calls coalesce onto one refresh;
-    // Concurrent calls coalesce onto one refresh. A refresh that fails rejects
+    // a refresh that fails rejects here, where the default namespaces would
-    // here, where the default namespaces would stay silent and serve the last
+    // instead stay silent and serve the last good copy.
    // good copy.
    async fresh(): Promise<FreshReads> {
        await this.refreshNow();
        return {
@@ -642,10 +613,10 @@ export class Library {
    // The fresh read of the collection list alone (issue #210): every live
    // collection that decrypts, in the server's order, from one collections
    // request. Unlike a refresh, it fetches no collection's files, which on a
-    // large account take long. It stores nothing. A refresh from a stored
+    // large account take long. Nothing is stored: a refresh fetches a
-    // cursor past 0 fetches a collection's files only when the collection is
+    // collection's files only when the collection is new or has changed since
-    // new or has changed since the stored copy. So does `refreshCollection()`.
+    // the stored copy, so a collection stored here without its files would
-    // Neither would fetch the files of a collection stored here without them.
+    // never have them fetched.
    async freshCollections(): Promise<Collection[]> {
        if (this.closed) throw new Error("the library is closed");
        const { collections } = await this.client.collectionsSince({
@@ -654,44 +625,19 @@ export class Library {
        return collections;
    }
    // Bring one collection up to date in the store (issue #217), given its
    // record from `freshCollections()`. It does for that collection what a
    // refresh does for a changed one. It fetches no other collection's files.
    // It resolves to whether the store then holds the collection.
    //
    // It adds a collection the store does not hold only while the stored
    // cursor is 0, before any refresh has received a collection. After that,
    // it stores nothing for such a collection and resolves to false. Only a
    // refresh may then add it, after the collections the store holds.
    //
    // It runs in the same slot as a refresh, so the two never run at the same
    // time. It first waits for a running refresh or `refreshCollection()` to
    // end. While its own work runs, a fresh read or `backup()` waits for it,
    // and the background loop skips its turn.
    async refreshCollection(collection: Collection): Promise<boolean> {
        while (this.cycle) await this.cycle.catch(() => {});
        if (this.closed) throw new Error("the library is closed");
        let held = false;
        await this.startCycle(false, async () => {
            held = await this.refreshCollectionOnce(collection);
        });
        return held;
    }
    // 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). It first takes the lock in that directory, unless
+    // ledger (issue #51). Takes the lock in that directory first, unless the
-    // the caller passes the lock it took as `opts.lock`. Taking it fails at
+    // caller passes the lock it took as `opts.lock`, failing at once while
-    // once while another backup of that directory runs. Once the lock is lost,
+    // another backup of it runs, and before it starts another file once the
-    // the backup fails before it starts another file (see
+    // lock is lost (see `lockBackupDirectory`). Waits for a
-    // `lockBackupDirectory`). It waits for a completed refresh as `fresh()`
+    // completed refresh, as `fresh()` does, joining one already running, and
-    // does, joining one already running. When that refresh fails, it rejects
+    // rejects before touching any file but the lock when it fails. Then puts
-    // before touching any file but the lock. It then puts pending originals
+    // pending originals at their save paths as `Photo.download()` does (and
-    // at their save paths as `Photo.download()` does, through the content
+    // optional thumbnails) through the content cache and pools, waits for an
-    // cache and pools. With `includeThumbnails` it also fetches thumbnails. It
+    // ML data fetch, and rebuilds the derived symlink/JSON views from the
-    // waits for an ML data fetch. It rebuilds the derived symlink/JSON views
+    // model, each file's JSON with its ML data, beside an `account.json` with
-    // from the model, each file's JSON with its ML data. An `account.json`
+    // the account's email and user ID.
    // beside them holds the account's email and user ID.
    // Throws before any network work when no content cache backs the
    // originals it must fetch.
    backup(opts?: BackupOptions): Promise<BackupResult> {
@@ -728,15 +674,12 @@ export class Library {
        );
    }
-    // Stop the background timer. Idempotent. A refresh or `refreshCollection()`
+    // Stop the background timer. Idempotent. An in-flight refresh is left to
-    // in flight is left to finish, and nothing starts after it. The returned
+    // finish; it will not schedule another cycle once closed. The returned
-    // promise resolves once all of these have finished:
+    // promise resolves once that refresh (including its cache write), the ML
-    //  - that refresh or `refreshCollection()`, with its cache write;
+    // fetch pass and the precache fetches already running have all finished,
-    //  - the ML fetch pass;
+    // so a caller can then remove the cache directory. A refresh failure is
-    //  - the precache fetches already running.
+    // reported through `status()`, not thrown here.
    // A caller can then remove the cache directory. A refresh failure is
    // reported through `status()`, and a `refreshCollection()` failure to its
    // own caller. Neither is thrown here.
    async close(): Promise<void> {
        this.closed = true;
        const precacheClosed = this.precache?.close();
@@ -759,41 +702,33 @@ export class Library {
        this.timer.unref?.();
    }
-    // The background loop's refresh: run a cycle unless a refresh or
+    // The background loop's refresh: run a cycle unless one is already in flight
-    // `refreshCollection()` is in flight (or the library is closed), and never
+    // (or the library is closed), and never let a failure escape — the
-    // let a failure escape. The background path reports errors through
+    // background path reports errors through `status()`/`onProgress`, it does
-    // `status()`/`onProgress`; it does not throw. It resolves once the cycle
+    // not throw. Resolves once the cycle it started (or skipped past) settles.
    // it started settles, or at once when it starts none.
    private runRefresh(): Promise<void> {
        if (this.closed || this.cycle) return Promise.resolve();
-        return this.startCycle(true, () => this.refreshCycle()).catch(() => {});
+        return this.startCycle().catch(() => {});
    }
-    // A fresh read's refresh (issue #75): join the running refresh or start
+    // A fresh read's refresh (issue #75): force a cycle and await it, rejecting
-    // one, and await it, rejecting if it fails. Concurrent fresh reads
+    // if it fails. Concurrent fresh reads coalesce onto the one in-flight cycle
-    // coalesce onto the one in-flight cycle — the background loop's included —
+    // — the background loop's included — so they never fan out into redundant
-    // so they never fan out into redundant server round-trips. A running
+    // server round-trips.
-    // `refreshCollection()` is waited for first.
+    private refreshNow(): Promise<void> {
-    private async refreshNow(): Promise<void> {
+        if (this.closed) {
-        while (this.cycle && !this.cycleIsRefresh) {
+            return Promise.reject(new Error("the library is closed"));
            await this.cycle.catch(() => {});
        }
-        if (this.closed) throw new Error("the library is closed");
+        return this.cycle ?? this.startCycle();
        return this.cycle ?? this.startCycle(true, () => this.refreshCycle());
    }
-    // Start `work` and record it in the in-flight slot, so every other caller
+    // Start one refresh cycle and record it as the in-flight cycle so every
-    // sees it. `isRefresh` says whether it is a refresh cycle, which a fresh
+    // caller coalesces onto it. The returned promise carries the cycle's real
-    // read can coalesce onto. The returned promise carries the real outcome.
+    // outcome; each caller attaches the handling its own path needs, and the
-    // Each caller attaches the handling its own path needs, and the slot is
+    // slot is cleared once the cycle settles.
-    // cleared once the work settles.
+    private startCycle(): Promise<void> {
-    private startCycle(
+        const cycle = this.refreshCycle();
        isRefresh: boolean,
        work: () => Promise<void>,
    ): Promise<void> {
        const cycle = work();
        this.cycle = cycle;
        this.cycleIsRefresh = isRefresh;
        void cycle.then(
            () => {
                if (this.cycle === cycle) this.cycle = undefined;
@@ -816,9 +751,9 @@ export class Library {
            this.lastError = undefined;
            this.emit({ operation: "refresh", status: "done" });
            // Backfill ML data for the files this refresh knows about. It runs
-            // outside the refresh's success or failure, so a fetch or disk
+            // outside the refresh's success/failure so a fetch or disk problem
-            // problem there never marks the metadata refresh failed. It is not
+            // there never marks the metadata refresh failed, and it is not
-            // awaited, so it never stalls the refresh interval. Its failure is
+            // awaited so it never stalls the refresh interval. Its failure is
            // reported through `status()` and `onProgress`.
            void this.fetchMLDataNow().catch(() => {});
        } catch (err) {
@@ -831,14 +766,11 @@ export class Library {
    // Fetch every change since the stored cursor, then commit. All network
    // reads happen before any store mutation, so a fetch that throws leaves the
-    // store untouched and the previous snapshot intact.
+    // store untouched and the previous snapshot intact. A collection or file
-    //
+    // that does not decrypt is left out instead, as if deleted, with the reason
-    // From a stored cursor of 0, the server lists every live collection. The
+    // kept in the store: the cursor moves past it, so no later refresh sees it
-    // refresh then replaces all the store holds, and counts every collection
+    // again until the server's copy changes.
    // as new. Only `refreshCollection()` can have stored anything before it.
    // So the store ends as it would had `refreshCollection()` never run.
    private async refreshOnce(): Promise<void> {
        const replace = this.store.collectionsSinceTime === 0;
        const page = await this.client.collectionsSince({
            sinceTime: this.store.collectionsSinceTime,
        });
@@ -846,19 +778,16 @@ export class Library {
        // Stage per-collection file diffs. A collection's files are
        // re-enumerated only when its updationTime has advanced past the cached
        // copy; an unchanged album's file list cannot have changed. New
-        // collections enumerate from the beginning of time. When the refresh
+        // collections enumerate from the beginning of time. Each collection
        // replaces the store, every collection counts as new. Each collection
        // whose files are fetched is reported, with how many there are to
        // fetch.
        const storedCopy = (id: number): Collection | undefined =>
            replace ? undefined : this.store.getCollection(id);
        const changedCollections = page.collections.filter((collection) => {
-            const known = storedCopy(collection.id);
+            const known = this.store.getCollection(collection.id);
            return !known || collection.updationTime > known.updationTime;
        });
        const filePages: { collectionID: number; page: FilesPage }[] = [];
        for (const collection of changedCollections) {
-            const known = storedCopy(collection.id);
+            const known = this.store.getCollection(collection.id);
            const filePage = await this.client.filesSince({
                collectionID: collection.id,
                collectionKey: collection.key,
@@ -873,56 +802,8 @@ export class Library {
            });
        }
-        await this.commit(page, filePages, replace);
+        // Network work done; commit to the store and persist only if something
-    }
+        // actually changed.
    // `refreshCollection()`'s work, run in the slot: fetch the files of one
    // collection changed since the stored copy, then commit. It resolves to
    // whether the store then holds the collection.
    private async refreshCollectionOnce(
        collection: Collection,
    ): Promise<boolean> {
        const known = this.store.getCollection(collection.id);
        // A refresh has received the account's collections, and this one is
        // not stored. It is new since then, or a refresh dropped it. Leave it
        // to the next refresh, which adds new collections after the stored
        // ones, in the server's order.
        if (!known && this.store.collectionsSinceTime > 0) return false;
        // The stored copy is as new or newer, so there is nothing to fetch.
        if (known && collection.updationTime <= known.updationTime) return true;
        const filePage = await this.client.filesSince({
            collectionID: collection.id,
            collectionKey: collection.key,
            sinceTime: known ? known.updationTime : 0,
        });
        // The stored cursor stays where it is, so the next refresh still
        // fetches the files of every other collection that changed.
        await this.commit(
            {
                collections: [collection],
                deleted: [],
                cursor: this.store.collectionsSinceTime,
            },
            [{ collectionID: collection.id, page: filePage }],
            false,
        );
        return true;
    }
    // Commit a collections page and the file pages fetched for its collections
    // to the store. With `replace`, the page lists every live collection, so
    // the commit first deletes every stored collection. A collection or file
    // that does not decrypt is left out, as if deleted. The reason is kept in
    // the store. Until the server's copy changes, only a refresh from a stored
    // cursor of 0 fetches it again. Last, save the store when it holds changes
    // not yet saved.
    private async commit(
        page: CollectionsPage,
        filePages: { collectionID: number; page: FilesPage }[],
        replace: boolean,
    ): Promise<void> {
        // The network work is done, so change the store now. `changed` says
        // whether this commit changed anything.
        let changed = false;
        if (this.store.userID !== this.userID) {
@@ -930,13 +811,6 @@ export class Library {
            changed = true;
        }
        if (replace) {
            for (const { id } of this.store.listCollections()) {
                this.store.deleteCollection(id);
                changed = true;
            }
        }
        for (const id of page.deleted) {
            if (this.store.getCollection(id)) {
                this.store.deleteCollection(id);
@@ -990,10 +864,10 @@ export class Library {
        if (changed) this.unsaved = true;
        // Reproject and notify subscribers of the delta. This tracks RAM (what
-        // reads see), so it fires whether or not the save below succeeds. A
+        // reads see), so it fires whether or not the save below succeeds; a
-        // failed save rejects the caller, and a refresh also records it in
+        // save failure surfaces separately through `status().lastError`.
-        // `status().lastError`. `lastRecords` advances on every commit that
+        // `lastRecords` advances every changed refresh so the next diff is
-        // changes something, so the next diff is against current state.
+        // against current state.
        if (changed) {
            const next = this.deriveNow();
            if (this.subscribers.size > 0) {
@@ -1004,16 +878,16 @@ export class Library {
            // Recompute the fill orders and pinned set against the new library.
            this.precache?.update(next);
        }
-        // Re-kick the fills on every commit. A finished sweep starts afresh to
+        // Re-kick the fills every cycle: a finished sweep starts afresh to pick
-        // pick up new files and retry any that failed. A running one is left
+        // up new files and retry any that failed, and a running one is left be.
        // be.
        this.precache?.start();
        // Persist whenever RAM holds changes disk has not accepted — including
        // changes an earlier cycle staged whose save failed. `unsaved` clears
-        // only once a save lands, so a later commit retries a failed save even
+        // only once a save lands, so a save failure both stays visible through
-        // when it changes nothing. A failed save rejects the caller, and a
+        // `status().lastError` (the throw below records it) and keeps being
-        // refresh also records it in `status().lastError`.
+        // retried, instead of a later empty refresh silently clearing it while
        // the on-disk cache is still behind RAM.
        if (this.unsaved) {
            await this.store.save();
            this.unsaved = false;
@@ -1029,14 +903,13 @@ export class Library {
        return this.mlFetch;
    }
-    // One ML fetch pass. It fetches, decrypts and stores the ML data of every
+    // One ML fetch pass: fetch, decrypt and store the ML data for every file
-    // file the store knows about that is not cached, or whose `updationTime`
+    // the store knows about that is not cached (or whose `updationTime` has
-    // has advanced. It fetches through the metadata pool, and updates the CLIP
+    // advanced), through the metadata pool, and update the CLIP index. For a
-    // index. For a file whose ML data does not decrypt, gunzip or parse, it
+    // file whose ML data does not decrypt, gunzip or parse, it gathers the
-    // gathers the reason instead. It puts the reasons it gathered in
+    // reason instead, and puts the reasons it gathered in `mlDataErrors` when
-    // `mlDataErrors` when it ends without failing. A failure leaves
+    // it ends without failing. A failure leaves `mlDataErrors` as it was and
-    // `mlDataErrors` as it was and is reported through `status()` and
+    // is reported through `status()` and `onProgress`, then thrown.
    // `onProgress`, then thrown.
    private async runMLFetch(): Promise<void> {
        const mldata = this.mlStore;
        // Bind so the call keeps the client as its receiver when invoked
@@ -1104,9 +977,9 @@ export class Library {
        }));
    }
-    // The distinct files the store holds, one entry per fileID, since a file
+    // The distinct files the store holds, one entry per fileID (a file in
-    // in several collections shares its ML data. Each entry carries the key
+    // several collections shares its ML data), each carrying the key and the
-    // and the newest `updationTime` seen across the file's memberships.
+    // newest `updationTime` seen across its memberships.
    private uniqueFiles(): {
        id: number;
        key: Uint8Array;
@@ -61,7 +61,7 @@ export interface MLIndex {
 // Pull the CLIP embedding out of a payload, or undefined when it is absent or
 // misshapen. Kept strict so a bad payload is skipped rather than corrupting the
 // packed index.
-export const clipEmbedding = (payload: MLData): number[] | undefined => {
+const clipEmbedding = (payload: MLData): number[] | undefined => {
    const clip = payload.clip;
    if (typeof clip !== "object" || clip === null) return undefined;
    const embedding = (clip as { embedding?: unknown }).embedding;
@@ -122,7 +122,7 @@ export class Precache {
    }
    // Recompute the fill orders and the pinned set from the current projection.
-    // Called at open and after every change to the store.
+    // Called at open and after every refresh that changes the library.
    update(records: DerivedRecords): void {
        const photos = [...records.photos.values()].sort(
            (a, b) => b.takenAt - a.takenAt || b.fileID - a.fileID,
@@ -71,14 +71,13 @@ export interface LibrarySnapshot {
    takenAt: number;
 }
 // What one refresh or `refreshCollection()` changed in the records.
 export interface LibraryChange {
-    // Full records for albums/photos added or changed.
+    // Full records for albums/photos added or changed by the refresh.
    albumsChanged: AlbumRecord[];
    photosChanged: PhotoRecord[];
    fileIDsRemoved: number[];
    albumIDsRemoved: number[];
-    // Wall-clock milliseconds when the store changed.
+    // Wall-clock milliseconds of the refresh that produced this change.
    refreshedAt: number;
 }
@@ -3,7 +3,7 @@
 // The store keeps one `metadata.json` file holding the account's server
 // state: the user id, a schema version, the cursor for the incremental
 // collections listing, the decrypted collection and file records, and the
-// collections and files that did not decrypt. The whole file is read
+// collections and files the refresh could not decrypt. The whole file is read
 // into RAM on load and rewritten as a whole on save; there is no partial
 // update and no lock file. A separate refresh unit populates the store from
 // the server — this module only stores what it is given.
@@ -34,11 +34,9 @@ const FILE_MODE = 0o600;
 type StoredCollection = Omit<Collection, "key"> & { key: string };
 type StoredFile = Omit<EnteFile, "key"> & { key: string };
-// A collection, or with `fileID` a file in it, that did not decrypt or parse,
+// A collection, or with `fileID` a file in it, that the last refresh to fetch
-// and why. A refresh or `refreshCollection()` records it on fetching such a
+// it could not decrypt or parse, and why. It is kept until a later refresh
-// copy. A later fetch drops it on getting a copy that decrypts, or on learning
+// fetches it again, because a refresh fetches only what changed.
 // that the server deleted it. Each fetch asks only for what changed, so the
 // store keeps the record between fetches.
 export interface Undecryptable {
    collectionID: number;
    fileID?: number;
@@ -72,6 +70,12 @@ export class MetadataStore {
    userID = 0;
    collectionsSinceTime: Microseconds = 0;
    // True when `load` populated this store from a valid existing file; false
    // on a first run or a missing/corrupt/wrong-version file that loaded empty.
    // `Library.open` reads it to decide whether the first refresh may run in
    // the background (an existing copy already serves reads) or must be awaited.
    loadedFromDisk = false;
    private readonly collections = new Map<number, Collection>();
    private readonly files = new Map<string, EnteFile>();
    private undecryptable: Undecryptable[] = [];
@@ -98,6 +102,7 @@ export class MetadataStore {
            if (parsed.schemaVersion !== METADATA_SCHEMA_VERSION) {
                return store;
            }
            store.loadedFromDisk = true;
            store.userID = parsed.userID ?? 0;
            store.collectionsSinceTime = parsed.collectionsSinceTime ?? 0;
            for (const stored of parsed.collections ?? []) {
@@ -224,14 +229,8 @@ export class MetadataStore {
        this.files.delete(fileKey(collectionID, fileID));
    }
    // Sorted by collection ID, then file ID, so the order does not depend on
    // when each record was fetched.
    listUndecryptable(): Undecryptable[] {
-        return [...this.undecryptable].sort(
+        return [...this.undecryptable];
            (a, b) =>
                a.collectionID - b.collectionID ||
                (a.fileID ?? 0) - (b.fileID ?? 0),
        );
    }
    // Replaces any earlier record of the same collection or file.
@@ -1,7 +1,6 @@
 import { mkdirSync, readFileSync, writeFileSync } from "node:fs";
 import { join } from "node:path";
 import * as jpeg from "jpeg-js";
 import { clipKeywords } from "./clip-keywords.js";
 import type { Client } from "./client.js";
 import { describeError } from "./errors.js";
 import { readExifTags } from "./exif.js";
@@ -98,8 +97,7 @@ const extractExif = async (
 // Dump every decrypted metadata layer the account holds into a directory tree
 // of plain JSON: account, per-collection, and per-file records including the
-// private and public magic metadata and the ML data, with the keywords of its
+// private and public magic metadata and (by default) the ML data. Collections
 // CLIP embedding in place of the embedding (see clip-keywords.ts). Collections
 // and files are enumerated from the library's cache, which the caller refreshes
 // first. Returns how many files have no ML data because their ML data request
 // failed or their ML data did not decrypt, gunzip or parse; they are still
@@ -232,16 +230,8 @@ export const runMetadataBackup = async (
        if (file.pubMagicMetadata)
            fileMeta.pubMagicMetadata = file.pubMagicMetadata;
        // The ML data without the CLIP embedding, and the keywords that
        // embedding gives.
        const ml = mlDataMap.get(file.id);
-        if (ml) {
+        if (ml) fileMeta.mlData = ml;
            const { clip: _clip, ...mlDataWithoutClip } = ml;
            fileMeta.mlData = mlDataWithoutClip;
            const isVideo = file.metadata.fileType === "video";
            const keywords = clipKeywords(ml, isVideo);
            if (keywords) fileMeta.keywords = keywords;
        }
        const mlError = mlDataErrors.get(file.id);
        if (mlError) fileMeta.mlDataError = mlError;
@@ -86,17 +86,10 @@ const DAY = "2024/2024-03/2024-03-01";
 const TOAST = new TextEncoder().encode("a few seconds of the wedding toast");
 // Ente's ML data for beach.jpg: a face it found, and the photo's CLIP
-// embedding, here that of a photo of a sunset (see clip-keywords.test.ts).
+// embedding.
 const ML_DATA = {
    face: { faces: [{ faceID: "100_1", score: 0.98 }] },
-    clip: {
+    clip: { embedding: [0.5, 0.6, 0.7] },
        embedding: JSON.parse(
            readFileSync(
                new URL("../clip-keywords-sunset.json", import.meta.url),
                "utf-8",
            ),
        ).embedding,
    },
 };
 // Each file's ID, its owner, its original as uploaded, and the metadata its
@@ -493,10 +486,7 @@ describe("the first backup of the account", () => {
            },
            updationTime: TAKEN,
        });
-        // The JSON holds the ML data without its CLIP embedding, and the
+        expect(beach.mlData).toEqual(ML_DATA);
        // keywords the embedding gives in its place.
        expect(beach.mlData).toEqual({ face: ML_DATA.face });
        expect(beach.keywords).toEqual(["Sunset"]);
        expect(beach.imageMetadata.exif.Make.description).toBe("Canon");
        expect(beach.imageMetadata.exif.Model.description).toBe("EOS R5");
@@ -507,7 +497,6 @@ describe("the first backup of the account", () => {
            metadata: { title: "toast.mp4", fileType: "video" },
        });
        expect(toast).not.toHaveProperty("mlData");
        expect(toast).not.toHaveProperty("keywords");
        expect(toast).not.toHaveProperty("imageMetadata");
        expect(toast).not.toHaveProperty("imageMetadataError");
@@ -52,7 +52,6 @@ import { tmpdir } from "node:os";
 import { describe, it, expect, beforeEach, afterEach, vi } from "vitest";
 import { runBackup, type BackupLibrary } from "../../src/backup.js";
 import { DISCOVER_CATEGORIES } from "../../src/clip-keyword-vectors.js";
 import { Library } from "../../src/library/index.js";
 import type { ContentSource } from "../../src/library/content.js";
 import type { CollectionsPage, FilesPage } from "../../src/client.js";
@@ -947,19 +946,9 @@ describe("the backup lock", () => {
    });
 });
-// Also serves ML data: file 100 has `ML_PAYLOAD`, whose CLIP embedding is that
+// Also serves ML data: file 100 has `ML_PAYLOAD`, the other two have none.
-// of a photo of a sunset (see clip-keywords.test.ts), and the other two have
+// While `mlError` is set, every ML data request fails with it.
-// none. While `mlError` is set, every ML data request fails with it.
+const ML_PAYLOAD = { face: { faces: [] }, clip: { embedding: [0.5, 0.25] } };
 const SUNSET_EMBEDDING: number[] = JSON.parse(
    readFileSync(
        new URL("../clip-keywords-sunset.json", import.meta.url),
        "utf-8",
    ),
 ).embedding;
 const ML_PAYLOAD = {
    face: { faces: [] },
    clip: { embedding: SUNSET_EMBEDDING },
 };
 class MLClient extends MockClient {
    mlError?: string;
@@ -979,99 +968,16 @@ const fileJSON = (outDir: string, fileID: number): Record<string, unknown> =>
    JSON.parse(readFileSync(saved(outDir, `${fileID}.json`), "utf-8"));
 describe("ML data in each file's JSON", () => {
-    // The JSON holds the ML data without its CLIP embedding, and in its place
+    it("writes a file's ML data, and no ML field for a file that has none", async () => {
    // the keywords the embedding gives.
    it("writes a file's ML data and keywords, and no ML field for a file that has none", async () => {
        const lib = await openLibrary(stubSource(), new MLClient());
        const outDir = join(root, "backup");
        const result = await lib.backup({ downloadDirectory: outDir });
        expect(result.failed).toBe(0);
-        expect(fileJSON(outDir, 100).mlData).toEqual({ face: { faces: [] } });
+        expect(fileJSON(outDir, 100).mlData).toEqual(ML_PAYLOAD);
        expect(fileJSON(outDir, 100).keywords).toEqual(["Sunset"]);
        expect(fileJSON(outDir, 101)).not.toHaveProperty("mlData");
        expect(fileJSON(outDir, 101)).not.toHaveProperty("mlDataError");
        expect(fileJSON(outDir, 101)).not.toHaveProperty("keywords");
        await lib.close();
    });
    // A file's ML data can hold faces and no CLIP embedding. Its JSON then has
    // the ML data and no keywords.
    it("writes no keywords for ML data without a CLIP embedding", async () => {
        const faces = { face: { faces: [{ faceID: "101_1", score: 0.9 }] } };
        // Gives file 101 ML data holding only faces.
        class FacesClient extends MockClient {
            async fetchMLData(args: { fileIDs: number[] }): Promise<{
                payloads: Map<number, MLData>;
                errors: Map<number, unknown>;
            }> {
                const payloads = new Map<number, MLData>();
                if (args.fileIDs.includes(101)) payloads.set(101, faces);
                return { payloads, errors: new Map() };
            }
        }
        const lib = await openLibrary(stubSource(), new FacesClient());
        const outDir = join(root, "backup");
        const result = await lib.backup({ downloadDirectory: outDir });
        expect(result.failed).toBe(0);
        expect(fileJSON(outDir, 101).mlData).toEqual(faces);
        expect(fileJSON(outDir, 101)).not.toHaveProperty("keywords");
        await lib.close();
    });
    // Ente's photos app keeps videos out of some Discover categories, Identity
    // among them. Here a photo and a video share one CLIP embedding, Identity's
    // own text embedding, so the photo gets the keyword Identity and the video
    // does not.
    it("keeps a video out of a category that leaves out videos", async () => {
        const identity = DISCOVER_CATEGORIES.find(
            (c) => c.title === "Identity",
        )!;
        expect(identity.showVideo).toBe(false);
        const toast = file(102, 1, "toast.mp4");
        const video = {
            ...toast,
            metadata: { ...toast.metadata, fileType: "video" as const },
        };
        // Serves beach.jpg and the video in the Vacation album, and gives
        // each ML data holding only that embedding.
        class VideoClient extends MockClient {
            override async filesSince(args: {
                collectionID: number;
            }): Promise<FilesPage> {
                const files =
                    args.collectionID === 1
                        ? [file(100, 1, "beach.jpg"), video]
                        : [];
                return { files, deleted: [], cursor: 1 };
            }
            async fetchMLData(args: { fileIDs: number[] }): Promise<{
                payloads: Map<number, MLData>;
                errors: Map<number, unknown>;
            }> {
                const payloads = new Map<number, MLData>();
                for (const id of args.fileIDs) {
                    payloads.set(id, {
                        clip: { embedding: identity.textEmbedding },
                    });
                }
                return { payloads, errors: new Map() };
            }
        }
        const lib = await openLibrary(stubSource(), new VideoClient());
        const outDir = join(root, "backup");
        const result = await lib.backup({ downloadDirectory: outDir });
        expect(result.failed).toBe(0);
        expect(fileJSON(outDir, 100).keywords).toContain("Identity");
        expect(fileJSON(outDir, 102)).toHaveProperty("keywords");
        expect(fileJSON(outDir, 102).keywords).not.toContain("Identity");
        await lib.close();
    });
@@ -1087,7 +993,7 @@ describe("ML data in each file's JSON", () => {
        const result = await lib.backup({ downloadDirectory: outDir });
        // File 100's ML data was cached by the first run and is kept.
-        expect(fileJSON(outDir, 100).mlData).toEqual({ face: { faces: [] } });
+        expect(fileJSON(outDir, 100).mlData).toEqual(ML_PAYLOAD);
        expect(fileJSON(outDir, 100)).not.toHaveProperty("mlDataError");
        for (const fileID of [101, 200]) {
            expect(fileJSON(outDir, fileID).mlDataError).toBe(
@@ -1120,7 +1026,7 @@ describe("ML data in each file's JSON", () => {
        expect(result.failed).toBe(0);
        expect(result.skipped).toBe(3);
-        expect(fileJSON(outDir, 100).mlData).toEqual({ face: { faces: [] } });
+        expect(fileJSON(outDir, 100).mlData).toEqual(ML_PAYLOAD);
        for (const fileID of [100, 101, 200]) {
            expect(fileJSON(outDir, fileID)).not.toHaveProperty("mlDataError");
        }
@@ -124,35 +124,20 @@ const FILES: Record<number, EnteFile[]> = {
 // thumbnail as empty. `withNewFile` adds new.jpg (102) to Vacation, advancing
 // the collection's updationTime as the server does. `beachInWork` adds
 // beach.jpg (100) to Work as well, so that one file is in both albums.
-// `newAlbums` adds the albums A (3) and B (4), in that order, which both hold
+// `refreshError` makes listing collections fail with that message.
 // shared.jpg (300). `refreshError` makes listing collections fail with that
 // message.
 const fakeClient = (
    opts: {
        failID?: number;
        emptyThumbID?: number;
        withNewFile?: boolean;
        beachInWork?: boolean;
        newAlbums?: boolean;
        refreshError?: string;
    } = {},
 ) => {
-    let collections = opts.withNewFile
+    const collections = opts.withNewFile
        ? [{ ...COLLECTIONS[0], updationTime: 2 }, COLLECTIONS[1]]
        : COLLECTIONS;
    let files = FILES;
    if (opts.newAlbums) {
        collections = [
            ...collections,
            { ...collection(3, "A"), updationTime: 2 },
            { ...collection(4, "B"), updationTime: 2 },
        ];
        files = {
            ...files,
            3: [file(300, 3, "shared.jpg")],
            4: [file(300, 4, "shared.jpg")],
        };
    }
    if (opts.withNewFile) {
        files = {
            ...files,
@@ -550,7 +535,9 @@ describe("files", () => {
    it("exits 1 for an unknown collection", async () => {
        expect(await filesCommand(context(), "9", {})).toBe(1);
-        expect(stderr.text).toBe("Collection 9 not found\n");
+        expect(stderr.text).toBe(
            FETCHED_BOTH_ALBUMS + "Collection 9 not found\n",
        );
    });
    // Without a collection ID it lists every file in the account once (issue
@@ -584,57 +571,6 @@ describe("files", () => {
        ]);
        expect(stderr.text).toBe(FETCHED_BOTH_ALBUMS);
    });
    // `files 2` on an empty cache stores Work alone. The refresh that `files`
    // then waits for must still store Vacation first, as the server lists it.
    it("without a collection ID lists in the server's order after files 2 on an empty cache", async () => {
        const ctx = context(fakeClient({ beachInWork: true }));
        expect(await filesCommand(ctx, "2", {})).toBe(0);
        stdout.text = "";
        stderr.text = "";
        expect(await filesCommand(ctx, undefined, { json: true })).toBe(0);
        expect(
            JSON.parse(stdout.text).map(
                (row: { id: number; collectionID: number }) => [
                    row.id,
                    row.collectionID,
                ],
            ),
        ).toEqual([
            [100, 1],
            [101, 1],
            [200, 2],
        ]);
        expect(stderr.text).toBe(FETCHED_BOTH_ALBUMS);
    });
    // After a refresh, the server adds A and then B. `files 4` must not store B
    // ahead of A, so it waits for a refresh, which stores both in that order.
    it("without a collection ID lists new albums in the server's order after files with the second one's ID", async () => {
        expect(await filesCommand(context(), undefined, {})).toBe(0);
        const ctx = context(fakeClient({ newAlbums: true }));
        stdout.text = "";
        expect(await filesCommand(ctx, "4", {})).toBe(0);
        expect(stdout.text).toBe("300\timage\tshared.jpg\n");
        stdout.text = "";
        expect(await filesCommand(ctx, undefined, { json: true })).toBe(0);
        expect(
            JSON.parse(stdout.text).map(
                (row: { id: number; collectionID: number }) => [
                    row.id,
                    row.collectionID,
                ],
            ),
        ).toEqual([
            [100, 1],
            [101, 1],
            [200, 2],
            [300, 3],
        ]);
    });
 });
 describe("get and get-thumb", () => {
@@ -1458,7 +1394,7 @@ describe("backup-metadata --exif", () => {
 // collection list alone and stores nothing.)
 describe("backup-metadata and the thumbnail helpers refresh first", () => {
    beforeEach(async () => {
-        expect(await filesCommand(context(), undefined, {})).toBe(0);
+        expect(await filesCommand(context(), "1", {})).toBe(0);
        stdout.text = "";
        stderr.text = "";
    });
@@ -1643,13 +1579,11 @@ describe("an ID given on the command line", () => {
 // An account with many albums (issue #210). On an empty cache `collections`
 // used to wait for a refresh that fetched and decrypted the files of every
-// album, one album after another. It printed nothing until then, so on such an
+// album, one album after another, before it printed anything, so on such an
-// account it seemed to hang. `files` with an album's ID did the same before it
+// account it seemed to hang. The account here has 40 albums of one photo each,
-// listed that album (issue #217). The account here has 40 albums of one photo
+// encrypted as Ente's clients encrypt them, on the fake Ente server of
-// each, encrypted as Ente's clients encrypt them. The fake Ente server of
+// `test/ente-server.ts`, which also records the path of each request quak
-// `test/ente-server.ts` serves them. A wrapper around it records the path and
+// sends. The session is the one logging in to that server saves.
 // query of each request quak sends. The session is the one logging in to that
 // server saves.
 describe("an account with many albums", () => {
    const ALBUMS = 40;
    const PASSWORD = "many-albums";
@@ -1730,8 +1664,7 @@ describe("an account with many albums", () => {
                    : input instanceof URL
                      ? input.href
                      : input.url;
-            const { pathname, search } = new URL(url);
+            paths.push(new URL(url).pathname);
            paths.push(pathname + search);
            return ente(input, init);
        }) as typeof globalThis.fetch;
        const client = await Client.login({
@@ -1765,68 +1698,42 @@ describe("an account with many albums", () => {
            albums += `${id}\talbum\tAlbum ${id}\n`;
        expect(stdout.text).toBe(albums);
        expect(stderr.text).toBe("");
-        expect(paths).toEqual(["/collections/v2?sinceTime=0"]);
+        expect(paths).toEqual(["/collections/v2"]);
-        // It stored nothing that would make `refreshCollection()` skip an
+        // It stored nothing that would make a refresh skip an album's files:
-        // album's files: `files` after it still finds the album's photo.
+        // `files` after it still finds the album's photo.
        stdout.text = "";
        expect(await filesCommand(ctx, "7", {})).toBe(0);
        expect(stdout.text).toBe("700\timage\tphoto-7.jpg\n");
    });
-    it("files fetches the files of the album it lists and of no other", async () => {
+    it("files counts on stderr each album whose files its refresh fetched", async () => {
        expect(await filesCommand(accountContext(), "7", {})).toBe(0);
        expect(stdout.text).toBe("700\timage\tphoto-7.jpg\n");
        expect(stderr.text).toBe("");
        expect(paths).toEqual([
            "/collections/v2?sinceTime=0",
            "/collections/v2/diff?collectionID=7&sinceTime=0",
        ]);
    });
    // The first listing stored the album, so the second finds its stored copy
    // current and asks for no album's files.
    it("files run again for the same album sends no request for its files", async () => {
        const ctx = accountContext();
        expect(await filesCommand(ctx, "7", {})).toBe(0);
        stdout.text = "";
        paths.length = 0;
        expect(await filesCommand(ctx, "7", {})).toBe(0);
        expect(stdout.text).toBe("700\timage\tphoto-7.jpg\n");
        expect(paths).toEqual(["/collections/v2?sinceTime=0"]);
    });
    it("files with no album's ID counts on stderr each album whose files its refresh fetched", async () => {
        expect(await filesCommand(accountContext(), undefined, {})).toBe(0);
        let photos = "";
        let progress = "";
        for (let n = 1; n <= ALBUMS; n++) {
            photos += `${n * 100}\timage\tphoto-${n}.jpg\n`;
            progress += `Fetched the files of ${n} of ${ALBUMS} collections\n`;
        }
        expect(stdout.text).toBe(photos);
        expect(stderr.text).toBe(progress);
    });
    // `--json` shapes stdout only, so the refresh's progress is still counted
    // on stderr.
-    it("files --json with no album's ID counts on stderr each album whose files its refresh fetched", async () => {
+    it("files --json counts on stderr each album whose files its refresh fetched", async () => {
-        expect(
+        expect(await filesCommand(accountContext(), "7", { json: true })).toBe(
-            await filesCommand(accountContext(), undefined, { json: true }),
+            0,
-        ).toBe(0);
+        );
-        const rows = JSON.parse(stdout.text);
+        expect(JSON.parse(stdout.text)).toEqual([
-        expect(rows).toHaveLength(ALBUMS);
+            {
-        expect(rows[6]).toEqual({
+                id: 700,
-            id: 700,
+                title: "photo-7.jpg",
-            title: "photo-7.jpg",
+                fileType: "image",
-            fileType: "image",
+                creationTime: 1000,
-            creationTime: 1000,
+                collectionID: 7,
-            collectionID: 7,
+            },
-        });
+        ]);
        let progress = "";
        for (let n = 1; n <= ALBUMS; n++) {
            progress += `Fetched the files of ${n} of ${ALBUMS} collections\n`;
@@ -234,8 +234,8 @@ describe("-q", () => {
        });
    });
-    // The line saying why the command failed is the fatal one, and it is
+    // The refresh's progress is left out; the line saying why the command
-    // printed.
+    // failed is the fatal one, and it is printed.
    it("prints only the line a failing command exits with", async () => {
        expect(await quak("-q", "files", "9")).toEqual({
            code: 1,
@@ -41,7 +41,6 @@ import { beforeAll, afterAll, describe, expect, it, vi } from "vitest";
 import { init, toBase64, encryptBlob } from "../../src/crypto/index.js";
 import * as jpegJs from "jpeg-js";
 import { Client } from "../../src/client.js";
 import { DISCOVER_CATEGORIES } from "../../src/clip-keyword-vectors.js";
 import { Library } from "../../src/library/index.js";
 import {
    runMetadataBackup,
@@ -57,8 +56,8 @@ import {
    type MetaMockState,
 } from "../ente-server.js";
-// One file per ML data request, so each file of the mock account is fetched in
+// One file per ML data request, so the two files of the mock account are
-// a request of its own and one of them can fail on its own.
+// fetched in two requests and one of them can fail on its own.
 vi.mock("../../src/mldata-fetch.js", async (importOriginal) => ({
    ...(await importOriginal<typeof import("../../src/mldata-fetch.js")>()),
    MLDATA_BATCH_SIZE: 1,
@@ -67,21 +66,6 @@ vi.mock("../../src/mldata-fetch.js", async (importOriginal) => ({
 const TEST_EMAIL = "metabackup@example.com";
 const TEST_PASSWORD = "metapass";
 // The CLIP embedding of a photo of a sunset (see clip-keywords.test.ts), which
 // the ML data of beach.jpg holds.
 const SUNSET_EMBEDDING: number[] = JSON.parse(
    readFileSync(
        new URL("../clip-keywords-sunset.json", import.meta.url),
        "utf-8",
    ),
 ).embedding;
 // Identity, a Discover category of Ente's photos app that leaves out videos.
 const IDENTITY = DISCOVER_CATEGORIES.find((c) => c.title === "Identity")!;
 // ML data holding faces and no CLIP embedding, which file 302 has.
 const FACES_ONLY = { face: { faces: [{ faceID: "face-def", score: 0.9 }] } };
 let mock: MetaMockState;
 let testDir: string;
@@ -220,65 +204,6 @@ const buildMetaMock = async (): Promise<MetaMockState> => {
        updationTime: 1710000000000000,
    };
    // A file in coll 10 with the ML data given. `fileType` is Ente's number: 0
    // an image, 1 a video.
    const vacationFile = (
        id: number,
        title: string,
        fileType: number,
        mlData: object,
    ) => {
        const fileKey = sodium.crypto_secretstream_xchacha20poly1305_keygen();
        const { ciphertext: encKey, nonce } = encryptSecretbox(fileKey, ck1);
        const meta = encryptStreamBlob(
            new TextEncoder().encode(
                JSON.stringify({
                    title,
                    fileType,
                    creationTime: 1700000000000000,
                    modificationTime: 1700000000000000,
                }),
            ),
            fileKey,
        );
        const ml = encryptBlob(
            new Uint8Array(gzipSync(Buffer.from(JSON.stringify(mlData)))),
            fileKey,
        );
        return {
            raw: {
                id,
                collectionID: 10,
                ownerID: 42,
                encryptedKey: toBase64(encKey),
                keyDecryptionNonce: toBase64(nonce),
                metadata: {
                    encryptedData: toBase64(meta.ciphertext),
                    decryptionHeader: toBase64(meta.header),
                },
                file: {
                    decryptionHeader: toBase64(sodium.randombytes_buf(24)),
                },
                thumbnail: {
                    decryptionHeader: toBase64(sodium.randombytes_buf(24)),
                },
                updationTime: 1700000000000000,
            },
            mlData: {
                encryptedData: toBase64(ml.ciphertext),
                decryptionHeader: toBase64(ml.header),
            },
        };
    };
    // Files 300 and 301 in coll 10: a photo and a video whose ML data holds
    // only a CLIP embedding, Identity's own text embedding.
    const identityML = { clip: { embedding: IDENTITY.textEmbedding } };
    const identityPhoto = vacationFile(300, "passport.jpg", 0, identityML);
    const identityVideo = vacationFile(301, "passport.mp4", 1, identityML);
    // File 302 in coll 10: a photo whose ML data holds faces and no CLIP
    // embedding.
    const facesPhoto = vacationFile(302, "party.jpg", 0, FACES_ONLY);
    // Encrypt ML data for file 100 (gzipped JSON, encrypted with file key)
    const mlPayload = JSON.stringify({
        face: {
@@ -305,7 +230,7 @@ const buildMetaMock = async (): Promise<MetaMockState> => {
        clip: {
            version: 1,
            client: "test",
-            embedding: SUNSET_EMBEDDING,
+            embedding: [0.5, 0.6, 0.7],
        },
    });
    const gzipped = gzipSync(Buffer.from(mlPayload));
@@ -345,23 +270,12 @@ const buildMetaMock = async (): Promise<MetaMockState> => {
        keyAttributes: account.keyAttributes,
        encryptedToken: account.encryptedToken,
        collections: [rawColl1, rawColl2],
-        filesByCollection: {
+        filesByCollection: { 10: [rawFile1], 20: [rawFile2] },
            10: [
                rawFile1,
                identityPhoto.raw,
                identityVideo.raw,
                facesPhoto.raw,
            ],
            20: [rawFile2],
        },
        encryptedMLData: {
            100: {
                encryptedData: toBase64(mlCiphertext),
                decryptionHeader: toBase64(mlHeader),
            },
            300: identityPhoto.mlData,
            301: identityVideo.mlData,
            302: facesPhoto.mlData,
        },
        fileCiphertexts: { 100: encFileBody1 },
    };
@@ -518,9 +432,7 @@ describe("quak backup-metadata", () => {
        expect(account.email).toBe(TEST_EMAIL);
    });
-    // The CLIP embedding is left out of the ML data, and the keywords it gives
+    it("fetches and decrypts ML data by default", async () => {
    // are written in its place.
    it("fetches and decrypts ML data by default, with keywords for the CLIP embedding", async () => {
        const outDir = join(testDir, "ml-data");
        await runBackup(outDir);
@@ -540,41 +452,8 @@ describe("quak backup-metadata", () => {
        expect(fileMeta.mlData.face.faces[0].faceID).toBe("face-abc");
        expect(fileMeta.mlData.face.faces[0].score).toBeCloseTo(0.98);
        expect(fileMeta.mlData.face.faces[0].detection.box.x).toBeCloseTo(0.1);
-        expect(fileMeta.mlData).not.toHaveProperty("clip");
+        expect(fileMeta.mlData.clip).toBeDefined();
-        expect(fileMeta.keywords).toEqual(["Sunset"]);
+        expect(fileMeta.mlData.clip.embedding).toEqual([0.5, 0.6, 0.7]);
    });
    // Ente's photos app keeps videos out of some Discover categories, Identity
    // among them. Files 300 and 301, a photo and a video, share one CLIP
    // embedding, Identity's own text embedding, so the photo gets the keyword
    // Identity and the video does not.
    it("keeps a video out of a category that leaves out videos", async () => {
        expect(IDENTITY.showVideo).toBe(false);
        const outDir = join(testDir, "video-keywords");
        await runBackup(outDir);
        const vacation = join(outDir, "collections", "10-Vacation");
        const fileJSON = (fileID: number) =>
            JSON.parse(readFileSync(join(vacation, `${fileID}.json`), "utf-8"));
        expect(fileJSON(300).keywords).toContain("Identity");
        expect(fileJSON(301)).toHaveProperty("keywords");
        expect(fileJSON(301).keywords).not.toContain("Identity");
    });
    // A file's ML data can hold faces and no CLIP embedding. File 302's JSON
    // then has the ML data and no keywords.
    it("writes no keywords for ML data without a CLIP embedding", async () => {
        const outDir = join(testDir, "no-clip");
        await runBackup(outDir);
        const fileMeta = JSON.parse(
            readFileSync(
                join(outDir, "collections", "10-Vacation", "302.json"),
                "utf-8",
            ),
        );
        expect(fileMeta.mlData).toEqual(FACES_ONLY);
        expect(fileMeta).not.toHaveProperty("keywords");
    });
    it("extracts EXIF from downloaded files when --exif is set", async () => {
@@ -662,7 +541,7 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
                "utf-8",
            ),
        );
-        expect(ok.keywords).toEqual(["Sunset"]);
+        expect(ok.mlData.clip.embedding).toEqual([0.5, 0.6, 0.7]);
        expect(ok.mlDataError).toBeUndefined();
        const failed = JSON.parse(
@@ -720,7 +599,7 @@ describe("quak backup-metadata when a file's ML data cannot be read", () => {
                "utf-8",
            ),
        );
-        expect(ok.keywords).toEqual(["Sunset"]);
+        expect(ok.mlData.clip.embedding).toEqual([0.5, 0.6, 0.7]);
    });
    it("exits 0 when every ML data request succeeds", async () => {
@@ -3,18 +3,13 @@
 * issue #36, issue #52).
 *
 * The `collections`, `files`, `get`, and `get-thumb` commands must answer for
- * current server state, not the local cache. `files` without a collection ID,
+ * current server state, not the local cache. `files`, `get` and `get-thumb`
- * `get` and `get-thumb` force a `Library.fresh()` round-trip before they read.
+ * force a `Library.fresh()` round-trip before they read; the stand-in library
- * The stand-in library below serves nothing until `fresh()` has been awaited.
+ * below serves nothing until `fresh()` has been awaited, so a helper that read
- * A helper that read without refreshing would come back empty and fail here.
+ * without refreshing would come back empty and fail here. `collections` asks
- * `collections` asks the library for the collection list alone
+ * the library for the collection list alone (`freshCollections()`, issue
- * (`freshCollections()`, issue #210). It must not wait for a refresh, which
+ * #210), and must not wait for a refresh, which would fetch the files of every
- * would fetch the files of every collection. `files COLLECTION` reads that list
+ * collection.
 * too, then brings that one collection up to date (`refreshCollection()`,
 * issue #217). The stand-in serves a collection's files once `fresh()` has run,
 * or once `refreshCollection()` has resolved to `true` for that collection.
 * When `refreshCollection()` resolves to `false`, `files COLLECTION` forces a
 * refresh instead.
 *
 * `collections` and `files` also list in the library's enumeration order
 * (`listCollections`/`listFiles`) — the order the pre-library CLI printed — not
@@ -69,18 +64,12 @@ const file = (
 // A library that reveals its records only after `fresh()` has been awaited, and
 // serves them in the enumeration order it was given. `freshCollections()`
-// answers the collection list in that order without a refresh. When
+// answers the collection list in that order without a refresh. `photos.byID`
-// `refreshCollection()` resolves to true, it reveals the files of that one
+// returns a stand-in `Photo` carrying just the fileID the helper passes
-// collection.
+// through.
 // `photos.byID` returns a stand-in `Photo` carrying just the fileID the helper
 // passes through.
 class FakeLibrary implements FreshReadLibrary {
    freshCalls = 0;
    freshCollectionsCalls = 0;
    refreshCollectionIDs: number[] = [];
    // What `refreshCollection()` resolves to. With false it reveals nothing,
    // as a library that has had a refresh does for a collection it lacks.
    refreshCollectionHolds = true;
    private refreshed = false;
    constructor(
@@ -99,11 +88,6 @@ class FakeLibrary implements FreshReadLibrary {
        return this.collections;
    }
    async refreshCollection(collection: Collection): Promise<boolean> {
        this.refreshCollectionIDs.push(collection.id);
        return this.refreshCollectionHolds;
    }
    getCollection(id: number): Collection | undefined {
        if (!this.refreshed) return undefined;
        return this.collections.find((c) => c.id === id);
@@ -114,11 +98,7 @@ class FakeLibrary implements FreshReadLibrary {
    }
    listFiles(collectionID: number): EnteFile[] {
-        const current =
+        return this.refreshed
            this.refreshed ||
            (this.refreshCollectionHolds &&
                this.refreshCollectionIDs.includes(collectionID));
        return current
            ? this.files.filter((f) => f.collectionID === collectionID)
            : [];
    }
@@ -158,25 +138,18 @@ describe("CLI read helpers (issue #36 amendment, issue #52)", () => {
        expect(rows.map((c) => c.id)).not.toEqual(newestFirst);
    });
-    it("freshFiles brings the collection alone up to date, lists in enumeration order, keeps raw fields", async () => {
+    it("freshFiles refreshes first, lists in enumeration order, keeps raw fields", async () => {
        // Enumeration order by id 10, 11, 12; creationTimes ascending, so a
-        // newest-first sort would reverse them. Collection 2's file is not
+        // newest-first sort would reverse them.
        // listed.
        const files = [
            file(10, 1, 1_700_000_000_000_000),
            file(11, 1, 1_700_000_000_000_001),
            file(12, 1, 1_700_000_000_000_002),
            file(20, 2, 1_700_000_000_000_003),
        ];
-        const lib = new FakeLibrary(
+        const lib = new FakeLibrary([collection(1, 100)], files);
            [collection(1, 100), collection(2, 100)],
            files,
        );
        const rows = await freshFiles(lib, 1);
-        expect(lib.freshCollectionsCalls).toBe(1);
+        expect(lib.freshCalls).toBe(1);
        expect(lib.refreshCollectionIDs).toEqual([1]);
        expect(lib.freshCalls).toBe(0);
        expect(rows?.map((f) => f.id)).toEqual([10, 11, 12]);
        // Field values come from raw metadata: microsecond creationTime and the
@@ -230,25 +203,10 @@ describe("CLI read helpers (issue #36 amendment, issue #52)", () => {
        ]);
    });
    it("freshFiles forces a refresh when refreshCollection resolves to false", async () => {
        const lib = new FakeLibrary(
            [collection(1, 100)],
            [file(10, 1, 1_700_000_000_000_000)],
        );
        lib.refreshCollectionHolds = false;
        const rows = await freshFiles(lib, 1);
        expect(lib.refreshCollectionIDs).toEqual([1]);
        expect(lib.freshCalls).toBe(1);
        expect(rows?.map((f) => f.id)).toEqual([10]);
    });
    it("freshFiles returns undefined for an unknown collection", async () => {
        const lib = new FakeLibrary([collection(1, 100)], []);
        const rows = await freshFiles(lib, 999);
-        expect(lib.freshCollectionsCalls).toBe(1);
+        expect(lib.freshCalls).toBe(1);
        expect(lib.refreshCollectionIDs).toEqual([]);
        expect(lib.freshCalls).toBe(0);
        expect(rows).toBeUndefined();
    });
@@ -1,109 +0,0 @@
 {
    "photo": "https://upload.wikimedia.org/wikipedia/commons/d/db/Sunset_off_the_Massachusetts_coast_-_NOAA.jpg",
    "sha256": "be62f3289c9bf7b75af68cd6978021d54e8a531d5d4cc493f6e9fbf5e1ab74d3",
    "embedding": [
        -0.0021123015, -0.04437615, -0.062354308, 0.006249992, 0.022141185,
        0.011159019, 0.01227392, -0.00030532264, 0.03186437, 0.09196922,
        0.039111234, -0.037084445, -0.032962628, -0.019820206, -0.013141825,
        0.0047183544, 0.017137334, 0.046581306, 0.0047622235, 0.04982521,
        0.023128154, 0.032080866, 0.037709303, 0.019241406, 0.0032100384,
        -0.014275843, 0.049337693, 0.025953151, 0.014263995, -0.0062328726,
        -0.040504098, -0.015083303, -0.008123875, -0.006233639, -0.05352683,
        -0.0048083956, 0.0763486, -0.013155067, 0.025114346, 0.022016674,
        0.0001588023, -0.010341572, -0.0037518279, -0.019181008, 0.04549337,
        -0.0010725886, 0.004636866, 0.017177915, -0.0117317885, 0.0026097358,
        0.030738998, 0.013158572, -0.08856403, -0.0121391015, 0.011477229,
        -0.0033104012, 0.035524756, -0.018607879, -0.0071739843, -0.031906743,
        0.0056713386, -0.0044195866, 0.00292471, 0.00061686034, -0.043075223,
        0.09040427, 0.001522537, -0.011445652, 0.009609886, -0.0053201183,
        -0.0057452377, 0.00972853, -0.0024397348, -0.021255083, 0.015893811,
        -0.006020548, -0.09428023, 0.014277583, -0.017975299, -0.011878315,
        0.011825521, 0.00014203975, -0.0020437292, -0.05305343, -0.024840152,
        -0.011336872, -0.002796541, -0.00036171873, 0.004530499, 0.044486605,
        0.021602718, -0.01292857, 0.024530916, 0.019559948, -0.039928272,
        -0.0681174, 0.049101, 0.02461532, 0.0365531, -0.04070358, -0.011011939,
        -0.0027188526, -0.020370876, 0.012904856, 0.043157287, -0.051658224,
        -0.3726012, 0.019549074, -0.0499252, -0.04800559, -0.011493859,
        0.02893256, 0.060341954, 0.0013929688, -0.051283866, -0.024286803,
        0.044124287, -0.005995806, -0.062817656, 0.007369614, -0.021470634,
        -0.028147545, 0.00411659, 0.04234773, 0.03787647, 0.008579682,
        -0.038568925, -0.027498025, -0.028416378, 0.0022012168, 0.010906191,
        -0.013745787, 0.018267838, 0.013531097, -0.061559845, 0.004682517,
        -0.005993303, 0.0028113858, -0.0028286583, 0.0026029332, -0.06693403,
        -0.0072381413, -0.02419584, 0.0037009937, -0.0011296495, -0.030310456,
        0.0005999609, 0.009945354, 0.024915686, 0.038672045, 0.023009432,
        -0.05093051, -0.09101409, -0.06686167, -0.06211481, -0.022600474,
        0.0024902367, -0.0067171026, -0.016769778, -0.0032803628, 0.008623083,
        -0.0016110836, 0.014925073, 0.033811048, 0.012829449, -0.052575592,
        0.03728281, -0.0051201633, 0.021238064, -0.031086605, -0.0043402985,
        0.25054494, -0.028396713, -0.010725523, -0.023445267, 0.021751683,
        0.003130971, 0.012270548, -0.014836475, 0.014466885, 0.0021478906,
        -0.088153616, 0.015356315, 0.039639276, -0.040283255, 0.014923924,
        -0.029303031, -0.004475201, 0.047299225, -0.06726505, -0.012491676,
        -0.002080582, 0.03506341, 0.04146718, 0.0074114986, -0.009582633,
        0.006623749, -0.05454898, -0.0034387247, -0.014780821, 0.03698328,
        -0.034441486, 0.22032379, -0.021792699, 0.008001907, 0.0341019,
        0.0025784625, -0.0071689896, -0.014151225, -0.050547987, -0.030372301,
        -0.03288388, -0.042987447, -0.0033656165, 0.021502906, -0.0030374376,
        -0.024413, -0.03506603, 0.030891743, 0.0069994032, 0.004887366,
        0.030707076, 0.0065348223, 0.0008240555, 0.016809713, -0.024151647,
        -0.0040458064, 0.044567548, 0.03908212, -0.061782435, 0.0026002831,
        0.02003242, -0.0115451, -0.045135964, -0.0663542, 0.005240975,
        0.0010777109, -0.009276002, -0.011919081, 0.027654119, -0.013634551,
        0.0129154315, -0.013195512, 0.040571272, -0.099290505, -0.04656693,
        -0.20979854, 0.04181004, -0.06769166, -0.04121946, 0.018260444,
        0.005617506, -0.15694222, 0.032472793, 0.014189598, 0.008345103,
        -0.041118417, 0.0074527003, -0.011494104, 0.004906474, -0.0027100458,
        0.0009994594, -0.041061398, -0.045274835, 0.015187793, 0.034275036,
        -0.02813289, 0.02098019, -0.015043198, 0.03716667, 0.013542642,
        -0.008104835, 0.014965486, -0.027978558, 0.021163663, -0.006942737,
        -0.034969814, -0.038961593, 0.016802894, -0.012318175, -0.047821593,
        -0.01933216, 0.0064432374, 0.0322358, -0.020437784, 0.02659447,
        -0.03022022, -0.019443465, -0.094178624, -0.017009107, 0.03860671,
        -0.00023695534, -0.033089854, -0.014677462, 0.012356399, 0.018040499,
        -0.19360113, 0.011710817, -0.019871691, 0.020124774, 0.024948105,
        -0.024573864, -0.028349072, -0.041731454, 0.032646254, 0.015098165,
        0.0018447012, -0.01129152, -0.02481687, 0.036048, 0.20797811,
        0.04317757, -0.017239755, 0.033431605, -0.011384422, 0.0099174455,
        -0.19739223, -0.008901062, -0.056426458, 0.014591864, 0.0044474266,
        0.008209326, -0.012241819, 0.042553645, -0.021552453, 0.008611734,
        0.048944127, -0.013872049, 0.019179989, 0.008183264, -0.053223096,
        -0.027327595, -0.0033542586, -0.012353858, -0.010941209, 0.010212546,
        0.029714134, -0.011385593, -0.0013529479, 0.014505385, 0.01148663,
        0.012613636, -0.0074430504, -0.014008101, -0.028146038, -0.042778917,
        0.02143165, 0.016812252, -0.06286215, 0.02085532, -0.035128277,
        0.0241282, 0.01397908, -0.034992814, 0.013153766, 0.0068236147,
        0.013594184, -0.06859393, 0.051849406, 0.029675119, -0.0037699796,
        -0.00013216575, 0.02916647, 0.031859048, -0.015006051, 0.0001439966,
        0.0026584554, -0.0046948595, 0.039754897, 0.034873154, 0.0012870439,
        -0.011516082, -0.074089095, 0.019241294, 0.00076195505, 0.0027334464,
        -0.036206458, -0.0011109262, -0.048838835, -0.00204685, 0.01179991,
        0.0068136845, 0.009852495, 0.017308988, 0.03159545, 0.058803353,
        0.038116634, 0.008836143, -0.010460637, -0.010994099, -0.0012926942,
        -0.048370842, 0.037696566, -0.08093239, -0.0041242186, -0.005866373,
        0.02048607, -0.12549639, 0.011705739, -0.0021425558, 0.018078592,
        -0.038228087, 0.004245971, -0.11560507, 0.01381203, -0.02734893,
        0.029595908, 0.101082794, -0.042842254, -0.08397301, -0.1546237,
        -0.037624564, 0.0069606556, -0.008020479, 0.0043268185, 0.016504597,
        0.044554908, -0.05240209, 0.020519335, -0.050994243, -0.019861093,
        0.022066997, -0.0188911, 0.012919696, -0.022872692, -0.012961374,
        -0.020071112, 0.0074553066, 0.06402014, 0.04065211, 0.014139608,
        0.06221546, -0.02574805, 0.010114545, 0.020619567, 0.032264773,
        -0.009148828, 0.022849955, -0.016593235, -0.032456633, -0.006737303,
        -0.0037493357, -0.065912865, -0.0024181998, -0.0037048983, -0.019304488,
        0.009085037, 0.057529982, -0.0378338, 0.01792042, 0.01885012,
        -0.0043600523, 0.017382368, -0.027792772, 0.006749118, -0.0053297766,
        -0.011628587, 0.015736576, 0.024801968, 0.011543913, -0.01159873,
        -0.000759976, 0.042183932, 0.05764386, -0.06422416, 0.010577374,
        -0.02261249, 0.02282793, -0.05141075, -0.11287078, -0.020670144,
        -0.020953743, 0.030885734, -0.012597732, -0.121472664, 0.028447151,
        -0.0415664, -0.010061708, 0.06441338, 0.0271207, -0.0016693748,
        -0.0045694243, 0.020342957, 0.030528478, 0.007129517, -0.0029600926,
        -0.007061397, 0.06036486, -0.004736018, -0.0090786135, -0.07601116,
        -0.039556272, -0.051269546, -0.019473685, 0.029858151, 0.028464556,
        0.012424476, 0.013742254, 0.008742927, 0.006065751, -0.009892663,
        0.07699999, -0.003443197, 0.0027863425, 0.029197995, 0.0211013,
        0.01098379, 0.016684106, -0.028917195, 0.008122037, 0.0265241,
        -0.04461223
    ]
 }
@@ -1,129 +0,0 @@
 // `clipKeywords`: the keywords quak writes for a file in place of its CLIP
 // embedding.
 //
 // Ente's ML data for a file holds a CLIP embedding, 512 numbers its image
 // model gave the photo. Ente's photos app puts a file in a category of its
 // Discover section when the cosine similarity of that embedding and the text
 // embedding of the category's query is at least the category's minimum score,
 // and keeps videos out of some categories. `clipKeywords` applies that rule
 // and returns the titles of the categories a file falls in, highest score
 // first; `quak backup` and `quak backup-metadata` write them as `keywords`.
 import { readFileSync } from "node:fs";
 import { describe, expect, it } from "vitest";
 import { DISCOVER_CATEGORIES } from "../src/clip-keyword-vectors.js";
 import { clipKeywords } from "../src/clip-keywords.js";
 // 512 numbers: the ones given, then zeros.
 const vector = (...start: number[]): number[] => [
    ...start,
    ...new Array<number>(512 - start.length).fill(0),
 ];
 const withEmbedding = (embedding: unknown) => ({
    face: { faces: [] },
    clip: { embedding },
 });
 // Two made-up categories, each with a text embedding along one axis. The
 // embedding [3, 4] has a cosine similarity of 3/5 with "Across" and 4/5 with
 // "Up". Videos are kept out of "Across".
 const ACROSS = {
    title: "Across",
    query: "across",
    minScore: 0.6,
    showVideo: false,
    textEmbedding: vector(1),
 };
 const UP = {
    title: "Up",
    query: "up",
    minScore: 0.5,
    showVideo: true,
    textEmbedding: vector(0, 1),
 };
 describe("clipKeywords", () => {
    it("gives each category whose minimum score the similarity reaches, highest score first", () => {
        expect(
            clipKeywords(withEmbedding(vector(3, 4)), false, [ACROSS, UP]),
        ).toEqual(["Up", "Across"]);
    });
    it("leaves out a category when the similarity is just below its minimum score", () => {
        const stricter = { ...ACROSS, minScore: 0.6 + 1e-9 };
        expect(
            clipKeywords(withEmbedding(vector(3, 4)), false, [stricter, UP]),
        ).toEqual(["Up"]);
    });
    it("keeps a video out of a category that leaves out videos", () => {
        expect(
            clipKeywords(withEmbedding(vector(3, 4)), true, [ACROSS, UP]),
        ).toEqual(["Up"]);
    });
    it("gives an empty list for an embedding that falls in no category", () => {
        expect(
            clipKeywords(withEmbedding(vector(0, 0, 1)), false, [ACROSS, UP]),
        ).toEqual([]);
    });
    it.each([
        ["no CLIP embedding", { face: { faces: [] } }],
        ["a CLIP part that is not an object", { clip: null }],
        ["a CLIP part without an embedding", { clip: {} }],
        ["an embedding of 511 numbers", withEmbedding(vector(3, 4).slice(1))],
        ["an embedding with NaN in it", withEmbedding(vector(3, NaN))],
        ["an embedding with Infinity in it", withEmbedding(vector(Infinity))],
        ["an embedding of strings", withEmbedding(vector(3, 4).map(String))],
        ["an embedding of zeros", withEmbedding(vector())],
    ])("gives no keywords for ML data with %s", (_, mlData) => {
        expect(clipKeywords(mlData, false, [ACROSS, UP])).toBeUndefined();
    });
 });
 // The CLIP embedding Ente's image model gives a public-domain NOAA photo of a
 // sunset, made by bin/clip-keyword-vectors from the photo at `photo`.
 const SUNSET: { photo: string; sha256: string; embedding: number[] } =
    JSON.parse(
        readFileSync(
            new URL("clip-keywords-sunset.json", import.meta.url),
            "utf-8",
        ),
    );
 describe("Ente's Discover categories", () => {
    it("are the 16 of Ente's photos app, each with a text embedding of norm 1", () => {
        expect(DISCOVER_CATEGORIES.map((c) => c.title)).toEqual([
            "Identity",
            "Screenshots",
            "QR Codes",
            "Receipts",
            "Notes",
            "Memes",
            "Visiting Cards",
            "Babies",
            "Pets",
            "Selfies",
            "Wallpapers",
            "Food",
            "Celebrations",
            "Sunset",
            "Hills",
            "Greenery",
        ]);
        for (const category of DISCOVER_CATEGORIES) {
            expect(category.textEmbedding).toHaveLength(512);
            expect(Math.hypot(...category.textEmbedding)).toBeCloseTo(1, 5);
        }
    });
    it("give a photo of a sunset the keyword Sunset and no other", () => {
        expect(
            clipKeywords({ clip: { embedding: SUNSET.embedding } }, false),
        ).toEqual(["Sunset"]);
    });
 });
@@ -17,14 +17,6 @@
 *  4. `freshCollections()` reads the collection list alone, with one request
 *     and no collection's files, and stores nothing, so the next refresh still
 *     fetches the files of every collection (issue #210).
 *  5. `refreshCollection()` brings one collection up to date in the store
 *     (issue #217). It leaves the stored cursor where it was, so the next
 *     refresh still fetches the files of every other collection that changed.
 *     It never runs at the same time as a refresh. After a refresh, it stores
 *     no collection the store does not hold: not a new one, and not one a
 *     refresh deleted. `close()` waits for it. A library opened on a cache that
 *     only it wrote awaits its first refresh. That refresh replaces what it
 *     stored, in the server's order.
 *
 * The client is the same metadata-only mock the background-refresh tests use:
 * no crypto, no network, scripted pages, and a record of each call. A long
@@ -38,7 +30,6 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import { Library } from "../../src/library/index.js";
 import { MetadataStore } from "../../src/library/store.js";
 import type { CollectionsPage, FilesPage } from "../../src/client.js";
 import type { Collection, EnteFile } from "../../src/model/types.js";
@@ -153,26 +144,6 @@ const openSeeded = async (
    return { client, lib };
 };
 // Hold the client's next files request until `release()` is called. `started`
 // resolves once that request has been sent.
 const holdNextFilesRequest = (
    client: MockClient,
 ): { started: Promise<void>; release: () => void } => {
    let release!: () => void;
    const held = new Promise<void>((r) => (release = r));
    let sent!: () => void;
    const started = new Promise<void>((r) => (sent = r));
    const realFilesSince = client.filesSince.bind(client);
    client.filesSince = async (args) => {
        client.filesSince = realFilesSince;
        const page = await realFilesSince(args);
        sent();
        await held;
        return page;
    };
    return { started, release };
 };
 describe("Library.fresh", () => {
    let dir: string;
    let cacheDirectory: string;
@@ -316,10 +287,10 @@ describe("Library.freshCollections", () => {
        rmSync(dir, { recursive: true, force: true });
    });
-    // A refresh from a stored cursor past 0 fetches a collection's files only
+    // A refresh fetches a collection's files only when the collection is new
-    // when the collection is new or its updationTime has advanced past the
+    // or its updationTime has advanced past the stored copy's. Had the
-    // stored copy's. So does `refreshCollection()`. Neither would fetch the
+    // collection list been stored, the next refresh would take every
-    // files of a collection stored here without them.
+    // collection for one it already holds the files of, and fetch none.
    it("asks for the collection list alone and stores nothing", async () => {
        const client = new MockClient();
        const page = {
@@ -369,243 +340,3 @@ describe("Library.freshCollections", () => {
        }
    });
 });
 describe("Library.refreshCollection", () => {
    let dir: string;
    let cacheDirectory: string;
    beforeEach(() => {
        dir = mkdtempSync(join(tmpdir(), "quak-refresh-collection-"));
        cacheDirectory = join(dir, "cache");
    });
    afterEach(() => {
        rmSync(dir, { recursive: true, force: true });
    });
    // Collections 1 and 2 are stored at updationTime 100, with a stored cursor
    // of 100, and then both change on the server.
    it("fetches the files of one changed collection and leaves the others to the next refresh", async () => {
        const client = new MockClient();
        client.collectionsQueue.push({
            collections: [collection(1, 100), collection(2, 100)],
            deleted: [],
            cursor: 100,
        });
        client.filesFor(1, {
            files: [file(1001, 1, 90)],
            deleted: [],
            cursor: 90,
        });
        client.filesFor(2, {
            files: [file(2001, 2, 90)],
            deleted: [],
            cursor: 90,
        });
        const lib = await Library.open({
            client,
            cacheDirectory,
            refreshIntervalSeconds: SLOW_INTERVAL,
        });
        try {
            client.filesCalls.length = 0;
            client.filesFor(1, {
                files: [file(1002, 1, 110)],
                deleted: [],
                cursor: 110,
            });
            client.filesFor(2, {
                files: [file(2002, 2, 120)],
                deleted: [],
                cursor: 120,
            });
            // Collection 1's files alone, since the stored copy.
            expect(await lib.refreshCollection(collection(1, 110))).toBe(true);
            expect(client.filesCalls).toEqual([
                { collectionID: 1, sinceTime: 100 },
            ]);
            expect(lib.listFiles(1).map((f) => f.id)).toEqual([1001, 1002]);
            expect(lib.listFiles(2).map((f) => f.id)).toEqual([2001]);
            // The stored copy is now current, so no request.
            await lib.refreshCollection(collection(1, 110));
            expect(client.filesCalls).toHaveLength(1);
            // The next refresh asks from the stored cursor, 100, so it still
            // sees collection 2 changed and fetches its files.
            client.collectionsQueue.push({
                collections: [collection(1, 110), collection(2, 120)],
                deleted: [],
                cursor: 120,
            });
            await lib.fresh();
            expect(client.collectionsSinceTimes).toEqual([0, 100]);
            expect(client.filesCalls).toEqual([
                { collectionID: 1, sinceTime: 100 },
                { collectionID: 2, sinceTime: 100 },
            ]);
            expect(lib.listFiles(2).map((f) => f.id)).toEqual([2001, 2002]);
        } finally {
            await lib.close();
        }
    });
    // Collection 1 is stored at 100. `refreshCollection()` asks for it at 110,
    // which adds file 1002. While that files request waits, a fresh read
    // starts a refresh. The server tells that refresh that collection 1 was
    // deleted at 130.
    it("holds off a refresh that starts during the files request, which then deletes the collection", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        const files = holdNextFilesRequest(client);
        try {
            client.filesFor(1, {
                files: [file(1002, 1, 110)],
                deleted: [],
                cursor: 110,
            });
            client.collectionsQueue.push({
                collections: [],
                deleted: [1],
                cursor: 130,
            });
            const refreshing = lib.refreshCollection(collection(1, 110));
            await files.started;
            const reading = lib.fresh();
            // The refresh has not sent its collections request yet.
            await new Promise((r) => setImmediate(r));
            expect(client.collectionsSinceTimes).toEqual([0]);
            files.release();
            await refreshing;
            await reading;
            expect(client.collectionsSinceTimes).toEqual([0, 100]);
            expect(lib.getCollection(1)).toBeUndefined();
            expect(lib.listFiles(1)).toEqual([]);
        } finally {
            files.release();
            await lib.close();
        }
    });
    // `freshCollections()` lists collection 1 at 110. Before
    // `refreshCollection()` is called, a refresh learns that it was deleted at
    // 130.
    it("stores nothing for a collection that a refresh deleted before the call", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        try {
            client.collectionsQueue.push(
                { collections: [collection(1, 110)], deleted: [], cursor: 110 },
                { collections: [], deleted: [1], cursor: 130 },
            );
            const [listed] = await lib.freshCollections();
            await lib.fresh();
            client.filesCalls.length = 0;
            expect(await lib.refreshCollection(listed)).toBe(false);
            expect(client.filesCalls).toEqual([]);
            expect(lib.getCollection(1)).toBeUndefined();
        } finally {
            await lib.close();
        }
    });
    // A refresh has stored collection 1. Collection 2 is new on the server
    // since then. Only the next refresh may add it, after collection 1.
    it("stores nothing for a collection that is new since the last refresh", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        try {
            client.filesCalls.length = 0;
            expect(await lib.refreshCollection(collection(2, 110))).toBe(false);
            expect(client.filesCalls).toEqual([]);
            expect(lib.getCollection(2)).toBeUndefined();
        } finally {
            await lib.close();
        }
    });
    // The caller may remove the cache directory once `close()` resolves, so
    // the cache write must have landed by then.
    it("close() waits for a refreshCollection() in flight", async () => {
        const { client, lib } = await openSeeded(cacheDirectory);
        const files = holdNextFilesRequest(client);
        client.filesFor(1, {
            files: [file(1002, 1, 110)],
            deleted: [],
            cursor: 110,
        });
        const refreshing = lib.refreshCollection(collection(1, 110));
        await files.started;
        let closed = false;
        const closing = lib.close().then(() => {
            closed = true;
        });
        await new Promise((r) => setImmediate(r));
        expect(closed).toBe(false);
        files.release();
        await closing;
        const saved = await MetadataStore.load(
            join(cacheDirectory, "metadata.json"),
        );
        expect(saved.listFiles(1).map((f) => f.id)).toEqual([1001, 1002]);
        await refreshing;
    });
    // `quak files 2` on an empty cache stores collection 2 alone. A library
    // opened later on that cache must not serve it as the whole account. Its
    // first refresh replaces what the cache holds, in the server's order.
    it("open() awaits the first refresh on a cache that only refreshCollection() wrote", async () => {
        const client = new MockClient();
        client.filesFor(2, {
            files: [file(2001, 2, 90)],
            deleted: [],
            cursor: 90,
        });
        const first = await Library.open({
            client,
            cacheDirectory,
            refreshOnOpen: false,
            refreshIntervalSeconds: SLOW_INTERVAL,
        });
        expect(await first.refreshCollection(collection(2, 100))).toBe(true);
        await first.close();
        client.collectionsQueue.push({
            collections: [collection(1, 100), collection(2, 100)],
            deleted: [],
            cursor: 100,
        });
        client.filesFor(1, {
            files: [file(1001, 1, 90)],
            deleted: [],
            cursor: 90,
        });
        client.filesFor(2, {
            files: [file(2001, 2, 90)],
            deleted: [],
            cursor: 90,
        });
        client.filesCalls.length = 0;
        const lib = await Library.open({
            client,
            cacheDirectory,
            refreshIntervalSeconds: SLOW_INTERVAL,
        });
        try {
            expect(lib.status().lastRefreshAt).toBeDefined();
            expect(lib.listCollections().map((c) => c.id)).toEqual([1, 2]);
            // It fetches collection 2's files again, from the beginning.
            expect(client.filesCalls).toEqual([
                { collectionID: 1, sinceTime: 0 },
                { collectionID: 2, sinceTime: 0 },
            ]);
            expect(lib.listFiles(2).map((f) => f.id)).toEqual([2001]);
        } finally {
            await lib.close();
        }
    });
 });
@@ -20,9 +20,9 @@
 * 5. `close()` stops the timer and is idempotent, and its promise resolves
 *    only once an in-flight refresh has written the cache file.
 * 6. `cacheDirectory` defaults to the env-paths cache dir plus the user id.
- * 7. `open()` branches on the stored cursor. At 0, as on an empty cache, it
+ * 7. `open()` branches on the cache: an empty cache awaits the first refresh
- *    awaits the first refresh. Past 0 it serves the cache's copy at once and
+ *    (it has nothing to serve yet); an existing cache serves its copy at once
- *    refreshes in the background, so a slow or dead server never stalls
+ *    and refreshes in the background, so a slow or dead server never stalls
 *    opening.
 * 8. A save failure that leaves RAM ahead of disk keeps `status().lastError`
 *    set and keeps retrying the write; a later empty refresh does not clear it.
@@ -4,8 +4,7 @@
 * These are the surface the GUI consumes across Electron IPC. `snapshot()` is
 * synchronous — it reads the in-RAM store and projects it into plain records
 * (no keys) — and `subscribe({ onChange })` delivers a `LibraryChange` whenever
- * a refresh or `refreshCollection()` changes the derived records. The
+ * a background refresh actually changes the derived records. The contracts:
 * contracts:
 *
 *  1. `snapshot()` deduplicates a file across memberships into one record with
 *     every album id, orders photos newest first, and carries no key material.
@@ -172,7 +172,7 @@ describe("MetadataStore", () => {
        expect(store.listCollections()).toEqual([]);
    });
-    it("loads an empty store when the list of what did not decrypt is damaged", async () => {
+    it("loads an empty store when the list of what the refresh could not decrypt is damaged", async () => {
        // A backup reads that list on every run, so a damaged one that loaded
        // would fail every backup until the cache was deleted. A string is
        // damaged too, though JavaScript can loop over its characters.
@@ -266,23 +266,4 @@ describe("MetadataStore", () => {
        expect(store.getFile(12345, 67890)).toBeUndefined();
        expect(store.getFile(55555, 67890)?.key).toEqual(inB.key);
    });
    // A backup reports these in this order. It must not depend on whether a
    // refresh or `Library.refreshCollection()` fetched each one first.
    it("lists what did not decrypt by collection ID, then file ID", async () => {
        const store = await MetadataStore.load(path);
        store.putUndecryptable({ collectionID: 2, fileID: 7, error: "a" });
        store.putUndecryptable({ collectionID: 3, error: "b" });
        store.putUndecryptable({ collectionID: 1, fileID: 9, error: "c" });
        store.putUndecryptable({ collectionID: 2, fileID: 5, error: "d" });
        expect(
            store.listUndecryptable().map((r) => [r.collectionID, r.fileID]),
        ).toEqual([
            [1, 9],
            [2, 5],
            [2, 7],
            [3, undefined],
        ]);
    });
 });