fix(admin): reject quota_tolerance = 0 instead of silently blocking every upload

Zero is inside the documented 0–1 range and catastrophic. The per-user limit is
`free_disk * tolerance / active_uploaders`, so a tolerance of 0 makes every limit 0 and
refuses EVERY upload -- mid-event, with "Du hast dein Upload-Limit für dieses Event
erreicht", an error naming the wrong cause entirely. An admin reaching for an off-switch
wants `storage_quota_enabled`; the rejection now says so.

Rejecting the value rather than raising the floor. A floor of 0.01 was the obvious fix
and it is wrong: very small tolerances are legitimate -- they are how a large disk is
throttled down to a sensible per-guest ceiling, and how the quota specs steer it
(tolerance = target * active / free lands around 1e-5 on the 174 GB volume this suite
runs on). A floor would forbid real configurations, and would have broken the entire
storage-quota describe block, to prevent one typo. Verified: those four tests still pass.

Tests: the rejection, that the stored value is untouched (validation fully precedes any
write), and the mirror -- 0.00001 still round-trips -- so the guard can't quietly become
a floor later.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

.env.example

@@ -18,6 +18,10 @@ POSTGRES_PASSWORD=CHANGE_ME_use_a_strong_password
 POSTGRES_DB=eventsnap
 # Connection pool size. Default 10. For a busy event (~100 guests polling the feed
 # + SSE + uploads at once) raise to ~30 so requests don't queue on a pool permit.
+# PAIRED WITH THE DB CONTAINER'S MEMORY LIMIT: 30 backends plus Postgres 16's default
+# shared_buffers is already snug in the 1G that docker-compose.yml allots the `db`
+# service. If you raise this, raise `db.deploy.resources.limits.memory` with it — an
+# OOM in Postgres doesn't degrade one feature, it takes the whole event down.
 DATABASE_MAX_CONNECTIONS=30
 
 # ── Authentication ────────────────────────────────────────────────────────────
@@ -54,8 +58,26 @@ EXPORT_PATH=/exports
 #   max image size    20 MB
 #   max video size   500 MB
 #   estimated guests 100
-#   quota tolerance  0.75  (fraction of disk that triggers the low-storage warning)
+#   quota tolerance  0.75  (see below — NOT a warning threshold)
 # Adjust these in the admin UI before the event if needed.
+#
+# quota_tolerance is the MULTIPLIER IN THE PER-USER QUOTA FORMULA, not the point at
+# which anything warns you:
+#
+#     per_user_limit = floor(free_disk * quota_tolerance / active_uploaders)
+#
+# It is recomputed against LIVE free space on every upload, so it self-throttles: guests
+# converge on a fixed point at tolerance/(1+tolerance) of the free space you started
+# with — 43% at 0.75, i.e. ~30 GB of a fresh 70 GB.
+#
+# Raising it therefore AUTHORISES GUESTS TO FILL MORE OF THE DISK. Setting 0.95 in the
+# belief that it means "warn me later" moves the fixed point to ~49% and eats the
+# headroom the keepsake needs — and the keepsake needs a lot, because Gallery.zip and
+# Memories.zip are each roughly a second copy of every original (both store media
+# uncompressed). Budget for media + 2x media, or move exports to their own volume.
+#
+# 0.75 is the tested default. Lower it if the box is tight; raise it only if you have
+# provisioned export headroom separately.
 
 # ── Workers ───────────────────────────────────────────────────────────────────
 # Number of parallel image/video compression workers. Default 2. This is the main

README.md

@@ -34,7 +34,6 @@ A guest scans the QR code on their way in, types their name, and is immediately
 ### Planned (v1.x)
 
 - Individual file download button
-- Low-disk alert (< 10 GB free)
 - Event banner / cover image
 - Chunked resumable upload for large videos
 - Host-curated story highlights
@@ -231,6 +230,45 @@ so a host takedown or a ban actually revokes access to the bytes.
 
 ---
 
+## Sizing the disk
+
+`postgres_data`, `media_data` and `exports_data` are all Docker named volumes under
+`/var/lib/docker/volumes`, so **they share one filesystem**. Filling it does not
+degrade one subsystem — Postgres stops being able to write and the whole event goes
+down.
+
+Uploads are self-limiting. `per_user_limit = free_disk × quota_tolerance ÷
+active_uploaders` is recomputed against live free space on every upload, so guests
+converge on a fixed point at `tolerance / (1 + tolerance)` of the free space you
+started with — **43%** at the default 0.75. On an 80 GB box with ~70 GB free after
+the OS and images, media settles at ~30 GB and stops.
+
+**The keepsake is what the 80 GB baseline does not cover.** `Gallery.zip` and
+`Memories.zip` are built concurrently and each is roughly a second copy of every
+original: both write their media `Compression::Stored`, and `Memories.zip` streams the
+untouched original for every video and for every image at or under 5 MB. So a release
+wants room for **two more copies of the gallery** on top of the gallery itself.
+
+| Stage | Used | Free (80 GB box) |
+|---|---|---|
+| Fresh box (OS + images) | ~10 GB | ~70 GB |
+| Guests reach the quota fixed point | ~40 GB | ~40 GB |
+| Host releases → both archives | ~100 GB | **ENOSPC** |
+
+Two ways to size for it:
+
+- **Provision ~3× your expected media** on one volume (media + two archives), or
+- **give `exports_data` its own volume** so a full export cannot reach Postgres, and
+  size that one at ~2× expected media.
+
+This is no longer silent. The export refuses up front with the two numbers rather than
+hitting ENOSPC halfway through a multi-GB write, a rebuild reclaims the superseded
+generation before it starts (so peak is one generation, not two), and the host
+dashboard warns as soon as the keepsake would not fit — which is the only point at
+which anyone can still do something about it.
+
+---
+
 ## Backup
 
 There are **three** things to back up, and they live in three different places.
@@ -242,9 +280,12 @@ never exported into an operator's shell — so every command below runs through
 ```bash
 # 1. Database snapshot. Runs pg_dump inside the db container (the app image has no
 #    postgres client), reading credentials from the compose environment.
+#    --clean --if-exists makes the dump SELF-CLEANING: without it the restore below
+#    aborts on the first "already exists" against a database that has ever booted,
+#    which is every database you would actually want to restore over.
 mkdir -p ./backups
 docker compose exec -T db \
-  sh -c 'pg_dump -U "$POSTGRES_USER" "$POSTGRES_DB"' \
+  sh -c 'pg_dump --clean --if-exists -U "$POSTGRES_USER" "$POSTGRES_DB"' \
   | gzip > ./backups/db_$(date +%Y-%m-%d).sql.gz
 
 # 2. Uploaded media (originals + derivatives) out of the named volume.
@@ -261,7 +302,7 @@ docker run --rm \
   -v eventsnap_exports_data:/src:ro -v "$PWD/backups":/backup \
   alpine tar czf /backup/exports_$(date +%Y-%m-%d).tar.gz -C /src .
 
-# Weekly offsite sync of the three artefacts above.
+# Offsite sync of the three artefacts above.
 rsync -az ./backups/ user@storagebox.example.com:backup/eventsnap/
 ```
 
@@ -274,6 +315,82 @@ from a directory called `eventsnap`. Confirm yours with `docker volume ls`.
 > stops it being reachable except through the ticket-gated download handler.
 > Backing up only the media volume therefore loses every generated keepsake.
 
+### When to run it
+
+**A nightly cron is the wrong shape for this app.** Every irreplaceable byte is
+created inside one eight-hour window, and nobody can retake a wedding. Run the three
+commands above:
+
+1. **The night of the event**, once uploads have stopped. This is the backup that
+   matters; everything else is a formality.
+2. **After the host releases the gallery**, so the generated keepsake is captured too.
+3. Weekly thereafter, until the event is archived and torn down.
+
+Take the DB dump and the media tarball **back to back**, without uploads in flight
+between them. Upload rows reference files by path — a database from 22:00 and a media
+volume from 23:00 gives you rows pointing at files the dump doesn't know about, and
+rows whose files aren't in the tarball. Locking uploads from the host dashboard first
+(**Uploads sperren**) makes the pair genuinely consistent.
+
+---
+
+## Restore
+
+An untested backup is not a backup. Run this once against a scratch host **before**
+the event — it is roughly ten minutes, and it is the only way to find out that your
+tarball is empty or your dump is truncated while that is still a small problem.
+
+```bash
+# 0. Stop the app FIRST. Migrations run on boot and a live pool will fight the
+#    restore — a booting app against a half-restored schema can leave the migration
+#    table and the schema disagreeing, which is its own recovery problem.
+#    Leave `db` running: the dump is restored through it.
+docker compose stop app caddy
+
+# 1. Database. The dump carries its own DROPs (step 1 of Backup), so this replaces
+#    rather than collides. A dump taken WITHOUT --clean --if-exists will abort here
+#    on the first "already exists" — restore that one into a fresh empty database
+#    instead.
+gunzip -c ./backups/db_2026-07-29.sql.gz \
+  | docker compose exec -T db \
+      sh -c 'psql -U "$POSTGRES_USER" -d "$POSTGRES_DB" --set ON_ERROR_STOP=1'
+
+# 2. Media. NOTE the `--numeric-owner` and the chown: the app runs as a
+#    NON-ROOT user (uid 100, gid 101 — `addgroup -S app && adduser -S app`), and a
+#    restore that lands root-owned files makes every upload fail with EACCES deep in
+#    the write path, surfacing to the guest as a generic 500 with nothing in the UI
+#    to suggest permissions. The explicit chown is what guarantees it — BusyBox tar
+#    (which is what `alpine` ships) has no --same-owner, and restores ownership only
+#    because it runs as root here.
+docker run --rm \
+  -v eventsnap_media_data:/dst -v "$PWD/backups":/backup:ro \
+  alpine sh -c 'tar xzf /backup/media_2026-07-29.tar.gz -C /dst \
+                    --numeric-owner && chown -R 100:101 /dst'
+
+# 3. Exports. Same volume-name caveat, same ownership rules.
+docker run --rm \
+  -v eventsnap_exports_data:/dst -v "$PWD/backups":/backup:ro \
+  alpine sh -c 'tar xzf /backup/exports_2026-07-29.tar.gz -C /dst \
+                    --numeric-owner && chown -R 100:101 /dst'
+
+# 4. Back up. Migrations run, then export recovery re-arms any keepsake whose file
+#    didn't come back with the volume.
+docker compose up -d app caddy
+docker compose logs -f app        # watch for "migrations applied"
+
+# 5. Verify — all three, not just the first.
+curl -fsS https://DOMAIN/health && echo            # → ok
+#   … then sign in as host and confirm the feed renders images (proves the media
+#   volume restored AND is readable by uid 100), and that the keepsake downloads.
+```
+
+If the media volume restored but images 404 while the feed lists them, the paths are
+there and the bytes aren't — check `docker compose exec app ls -ln /media/originals`
+and confirm both the files and the `100:101` ownership.
+
+The restore is deliberately **not** automated. It is rare, destructive, and the one
+operation where a script that half-works is worse than a checklist someone reads.
+
 ---
 
 ## Running the backend test suite
@@ -348,7 +465,7 @@ Open:
 - [ ] SSE delta-fetch on foreground reconnect (scaffolded in [sse.ts](frontend/src/lib/sse.ts), not wired)
 - [ ] Live diashow / slideshow mode — see [docs/CONCEPT_DIASHOW.md](docs/CONCEPT_DIASHOW.md)
 - [ ] Individual file download button per post
-- [ ] Low-disk alert (< 10 GB free)
+- [x] Low-disk alert — host dashboard warns below 10 GB free, or whenever the keepsake would not fit
 - [ ] Event banner / cover image
 - [ ] Chunked resumable upload for files > 100 MB
 - [ ] Shared Tailwind config between main app and export-viewer

backend/migrations/020_social_rate.down.sql

@@ -0,0 +1 @@
+DELETE FROM config WHERE key IN ('social_rate_per_min', 'social_rate_enabled');

backend/migrations/020_social_rate.up.sql

@@ -0,0 +1,16 @@
+-- Per-user rate limit for social writes (likes, comments, comment deletions).
+--
+-- These were the only writes in the app with no limit at all. Every other mutating
+-- path -- upload, join, recover, export, admin login -- carries one; social.rs
+-- carried none, so the coverage was asymmetric rather than deliberately open.
+--
+-- Severity is genuinely low for an invited-guest event, and the amplification worry
+-- turned out to be contained: a like fans an SSE broadcast to ~100 clients, but the
+-- export regeneration it could otherwise trigger is debounced (REGEN_DEBOUNCE 20s)
+-- and superseded workers are inert. So this closes the gap for symmetry, not urgency,
+-- and the ceiling is set high enough that no real guest will ever meet it -- a
+-- double-tapping enthusiast at a wedding is not the thing being defended against.
+INSERT INTO config (key, value) VALUES
+    ('social_rate_per_min',  '120'),
+    ('social_rate_enabled',  'true')
+ON CONFLICT (key) DO NOTHING;

backend/src/handlers/admin.rs

@@ -127,6 +127,9 @@ pub async fn patch_config(
         // Same shape for /recover: the per-(ip, name) bucket is the anti-guessing control,
         // this only bounds a name-cycling flood in front of a cost-12 bcrypt (migration 019).
         ("recover_ip_rate_per_min", true, 1.0, 100_000.0),
+        // Aggregate ceiling on likes + comments + comment deletions, per user per minute.
+        // These were the only mutating endpoints with no limit at all (migration 020).
+        ("social_rate_per_min", true, 1.0, 100_000.0),
         ("quota_tolerance", false, 0.0, 1.0),
         ("estimated_guest_count", true, 1.0, 1_000_000.0),
     ];
@@ -141,6 +144,7 @@ pub async fn patch_config(
         // missing from this allowlist — so the switch existed in code and could never be flipped.
         "admin_login_rate_enabled",
         "recover_rate_enabled",
+        "social_rate_enabled",
         "quota_enabled",
         "storage_quota_enabled",
         "upload_count_quota_enabled",
@@ -193,6 +197,23 @@ pub async fn patch_config(
                     "Wert für {key} liegt außerhalb des zulässigen Bereichs ({min}–{max})."
                 )));
             }
+            // Zero is in range and catastrophic. `quota_tolerance` is the multiplier in
+            // `free_disk * tolerance / active_uploaders`, so 0 makes every per-user limit 0 and
+            // refuses EVERY upload — mid-event, with "Du hast dein Upload-Limit für dieses Event
+            // erreicht", an error naming the wrong cause entirely. `storage_quota_enabled` is the
+            // intended off-switch.
+            //
+            // Rejecting the value rather than raising the floor: very small tolerances are
+            // legitimate (they are how a large disk is throttled down to a sensible per-guest
+            // ceiling, and how the e2e quota tests steer it — around 1e-5 on a 174 GB volume), so
+            // a floor of, say, 0.01 would forbid real configurations to prevent one typo.
+            if key_str == "quota_tolerance" && n == 0.0 {
+                return Err(AppError::BadRequest(
+                    "quota_tolerance = 0 würde jeden Upload blockieren. Zum Abschalten der \
+                     Speicher-Quote stattdessen „Speicher-Quote aktiv“ ausschalten."
+                        .into(),
+                ));
+            }
         } else if BOOL_KEYS.contains(&key_str) {
             match value.trim().to_ascii_lowercase().as_str() {
                 "true" | "false" | "1" | "0" | "yes" | "no" | "on" | "off" => {}

backend/src/handlers/social.rs

@@ -10,8 +10,40 @@ use crate::error::AppError;
 use crate::models::comment::{Comment, CommentDto};
 use crate::models::hashtag::{self, Hashtag};
 use crate::models::upload::Upload;
+use crate::services::config;
 use crate::state::AppState;
 
+/// Throttle a social write. Keyed PER USER, like the feed and upload limits and for the same
+/// reason: at a venue every guest sits behind one NAT, so an IP key hands the whole party a
+/// single bucket and the most active guest starves everyone else.
+///
+/// These were the only mutating endpoints in the app with no limit at all — the coverage was
+/// asymmetric, not deliberately open. The ceiling is set well above anything a real guest
+/// produces; this bounds a script, not an enthusiastic double-tapper.
+async fn check_social_rate(state: &AppState, user_id: Uuid) -> Result<(), AppError> {
+    let rate_limits_on = config::get_bool(&state.config_cache, "rate_limits_enabled", true).await;
+    let social_rate_on = config::get_bool(&state.config_cache, "social_rate_enabled", true).await;
+    if !(rate_limits_on && social_rate_on) {
+        return Ok(());
+    }
+    let rate_limit = config::get_usize(&state.config_cache, "social_rate_per_min", 120).await;
+    // ONE bucket across likes, comments and comment deletions. Separate buckets would let a
+    // caller triple the aggregate write rate just by alternating between them.
+    state
+        .rate_limiter
+        .check_with_retry(
+            format!("social:{user_id}"),
+            rate_limit,
+            std::time::Duration::from_secs(60),
+        )
+        .map_err(|retry_after_secs| {
+            AppError::TooManyRequests(
+                "Zu viele Aktionen. Bitte warte kurz und versuche es erneut.".into(),
+                Some(retry_after_secs),
+            )
+        })
+}
+
 #[derive(Serialize)]
 pub struct LikeResponse {
     /// The caller's like state *after* this toggle. The client sets `liked_by_me` from
@@ -35,6 +67,7 @@ pub async fn toggle_like(
     if user.is_banned {
         return Err(AppError::Forbidden("Du bist gesperrt.".into()));
     }
+    check_social_rate(&state, auth.user_id).await?;
 
     // Event-scope: the upload must belong to the caller's event (404 otherwise),
     // matching the host handlers' find_by_id_and_event pattern.
@@ -141,6 +174,7 @@ pub async fn add_comment(
     if user.is_banned {
         return Err(AppError::Forbidden("Du bist gesperrt.".into()));
     }
+    check_social_rate(&state, auth.user_id).await?;
 
     // Event-scope: only comment on an upload that belongs to the caller's event.
     Upload::find_by_id_and_event(&state.pool, upload_id, auth.event_id)
@@ -216,6 +250,7 @@ pub async fn delete_comment(
     if auth.is_banned {
         return Err(AppError::Forbidden("Du bist gesperrt.".into()));
     }
+    check_social_rate(&state, auth.user_id).await?;
     let comment = Comment::find_by_id(&state.pool, comment_id)
         .await?
         .ok_or_else(|| AppError::NotFound("Kommentar nicht gefunden.".into()))?;

backend/src/handlers/test_admin.rs

@@ -63,6 +63,7 @@ pub async fn truncate_all(
             ('export_rate_per_day',        '3'),
             ('join_ip_rate_per_min',       '60'),
             ('recover_ip_rate_per_min',    '30'),
+            ('social_rate_per_min',        '120'),
             ('quota_tolerance',            '0.75'),
             ('estimated_guest_count',      '100'),
             ('compression_concurrency',    '2'),
@@ -71,6 +72,7 @@ pub async fn truncate_all(
             ('feed_rate_enabled',          'false'),
             ('export_rate_enabled',        'false'),
             ('join_rate_enabled',          'false'),
+            ('social_rate_enabled',        'false'),
             ('admin_login_rate_enabled',   'false'),
             ('quota_enabled',              'false'),
             ('storage_quota_enabled',      'false'),

backend/src/services/export.rs

@@ -20,6 +20,29 @@ use crate::state::SseEvent;
 
 static VIEWER_DIR: Dir<'_> = include_dir!("$CARGO_MANIFEST_DIR/static/export-viewer");
 
+// ── Shared visibility filter ─────────────────────────────────────────────────
+
+/// The predicate that decides what lands in a keepsake, as ONE definition.
+///
+/// Two queries have to agree on it: [`query_uploads`], which selects the rows the archives are
+/// built from, and [`estimate_export_bytes`], which sizes them for the disk preflight. They used
+/// to state it separately, and the direction of drift matters — an estimate that misses rows the
+/// archive writes UNDER-reserves, which is the exact ENOSPC the preflight exists to prevent.
+///
+/// A `SRC:`-marked copy in the integration tests cannot catch that: drift means production moved
+/// and the copy didn't, so both sides of such a test sit still and it keeps passing. Sharing the
+/// fragment removes the failure by construction instead, and leaves the test doing what it is
+/// actually good at — pinning the behaviour.
+///
+/// CONTRACT: callers must alias `upload` as `u` and join `"user"` as `usr`, and bind the event id
+/// as `$1`.
+macro_rules! export_visibility_where {
+    () => {
+        "WHERE u.event_id = $1 AND u.deleted_at IS NULL
+           AND usr.uploads_hidden = FALSE AND usr.is_banned = FALSE"
+    };
+}
+
 // ── DB query rows ────────────────────────────────────────────────────────────
 
 #[derive(sqlx::FromRow)]
@@ -557,7 +580,7 @@ async fn run_zip_export_inner(
             };
             let entry_name = format!("{folder}/{date}_{name_safe}_{}.{ext}", row.id);
 
-            let builder = ZipEntryBuilder::new(entry_name.into(), Compression::Stored);
+            let builder = keepsake_entry(entry_name, Compression::Stored);
 
             // Open BEFORE writing the entry header. A missing source is skipped (the media file
             // was deleted, or its processing failed) — but it must be skipped without aborting the
@@ -950,7 +973,7 @@ async fn run_html_export_inner(
 
         // Write data.json
         {
-            let builder = ZipEntryBuilder::new("data.json".into(), Compression::Deflate);
+            let builder = keepsake_entry("data.json".into(), Compression::Deflate);
             let mut entry = zip.write_entry_stream(builder).await?;
             let mut cursor = AllowStdIo::new(std::io::Cursor::new(data_json.as_bytes()));
             fcopy(&mut cursor, &mut entry).await?;
@@ -959,7 +982,7 @@ async fn run_html_export_inner(
 
         // Write README.txt
         {
-            let builder = ZipEntryBuilder::new("README.txt".into(), Compression::Deflate);
+            let builder = keepsake_entry("README.txt".into(), Compression::Deflate);
             let mut entry = zip.write_entry_stream(builder).await?;
             let mut cursor = AllowStdIo::new(std::io::Cursor::new(README_TEXT.as_bytes()));
             fcopy(&mut cursor, &mut entry).await?;
@@ -992,7 +1015,7 @@ async fn run_html_export_inner(
             };
 
             let entry_name = format!("media/{name}");
-            let builder = ZipEntryBuilder::new(entry_name.into(), Compression::Stored);
+            let builder = keepsake_entry(entry_name, Compression::Stored);
             let mut zip_entry = zip.write_entry_stream(builder).await?;
             let mut f = src_file.compat();
             fcopy(&mut f, &mut zip_entry).await?;
@@ -1051,7 +1074,7 @@ async fn run_html_export_inner(
 // ── DB helpers ───────────────────────────────────────────────────────────────
 
 async fn query_uploads(pool: &PgPool, event_id: Uuid) -> Result<Vec<ExportUploadRow>> {
-    Ok(sqlx::query_as::<_, ExportUploadRow>(
+    Ok(sqlx::query_as::<_, ExportUploadRow>(concat!(
         "SELECT u.id, u.original_path, u.mime_type, u.caption,
                 usr.display_name AS uploader_name,
                 COUNT(DISTINCT l.user_id) AS like_count,
@@ -1059,11 +1082,12 @@ async fn query_uploads(pool: &PgPool, event_id: Uuid) -> Result<Vec<ExportUpload
          FROM upload u
          JOIN \"user\" usr ON usr.id = u.user_id
          LEFT JOIN \"like\" l ON l.upload_id = u.id
-         WHERE u.event_id = $1 AND u.deleted_at IS NULL
-           AND usr.uploads_hidden = FALSE AND usr.is_banned = FALSE
+         ",
+        export_visibility_where!(),
+        "
          GROUP BY u.id, usr.display_name
          ORDER BY u.created_at ASC",
-    )
+    ))
     .bind(event_id)
     .fetch_all(pool)
     .await?)
@@ -1267,15 +1291,16 @@ fn is_superseded_archive(
 /// downscaled to 2000px first, which only makes this estimate more conservative — the direction we
 /// want, since being wrong low means ENOSPC halfway through.
 ///
-/// Matches [`query_uploads`]' visibility filter exactly, so hidden/banned uploads aren't counted.
+/// Shares [`query_uploads`]' visibility filter via [`export_visibility_where`], so hidden/banned
+/// uploads can't be counted here but skipped there (or the reverse, which under-reserves).
 pub async fn estimate_export_bytes(pool: &PgPool, event_id: Uuid) -> Result<u64> {
-    let (bytes,): (i64,) = sqlx::query_as(
+    let (bytes,): (i64,) = sqlx::query_as(concat!(
         "SELECT COALESCE(SUM(u.original_size_bytes), 0)::bigint
            FROM upload u
            JOIN \"user\" usr ON usr.id = u.user_id
-          WHERE u.event_id = $1 AND u.deleted_at IS NULL
-            AND usr.uploads_hidden = FALSE AND usr.is_banned = FALSE",
-    )
+           ",
+        export_visibility_where!(),
+    ))
     .bind(event_id)
     .fetch_one(pool)
     .await
@@ -1527,6 +1552,36 @@ async fn maybe_broadcast_complete(
 /// double-clicking `index.html` (file://), where browsers block a cross-origin
 /// `fetch()` of a sibling `data.json` — so the data is inlined into the page.
 /// (`data.json` is still written separately for the http-served case.)
+/// Permissions stamped on every entry in both archives: `rw-r--r--`.
+///
+/// `ZipEntryBuilder::new` leaves the external file attribute at zero, and the host compatibility
+/// defaults to Unix — so every entry was written with a stored mode of **0000**. Windows Explorer
+/// ignores Unix modes and was fine, which is exactly why this survived: on Linux and macOS
+/// `unzip` faithfully applies what the archive asks for, and the guest gets a directory of files
+/// none of which they can open. `?---------` on every line of `unzip -Z`.
+///
+/// That is the keepsake — the artifact the whole event exists to produce — arriving unreadable,
+/// after distribution, with no server-side symptom at all.
+/// `S_IFREG | 0644`. The type bits are included because the mode is written whole into the high
+/// half of the external file attribute: without them extractors see a file of type "unknown"
+/// (`unzip -Z` renders `?rw-r--r--`), which works but is not what the archive means to say.
+const KEEPSAKE_ENTRY_MODE: u16 = 0o100_644;
+
+/// Build a ZIP entry for the keepsake. ALL entries in both archives go through here so the mode
+/// can't be forgotten at one of the six call sites.
+fn keepsake_entry(name: String, compression: Compression) -> ZipEntryBuilder {
+    ZipEntryBuilder::new(name.into(), compression).unix_permissions(KEEPSAKE_ENTRY_MODE)
+}
+
+/// Escape a JSON payload for inlining inside a `<script>` element.
+///
+/// See the call site in [`write_viewer_with_data`] for why this is every `<` and not just `</`.
+/// Kept separate so the property that matters — no `<` survives, and the value still decodes to
+/// the original — can be asserted without building a ZIP.
+fn escape_json_for_script(data_json: &str) -> String {
+    data_json.replace('<', "\\u003c")
+}
+
 async fn write_viewer_with_data(
     dir: &include_dir::Dir<'_>,
     zip: &mut ZipFileWriter<tokio::fs::File>,
@@ -1538,8 +1593,31 @@ async fn write_viewer_with_data(
         if path == "index.html" {
             let html = std::str::from_utf8(file.contents())
                 .context("export-viewer index.html is not valid UTF-8")?;
-            // Escape `</` so a caption containing `</script>` can't break out of the tag.
-            let safe = data_json.replace("</", "<\\/");
+            // Escape EVERY `<`, not just `</`.
+            //
+            // `</` -> `<\/` stops the obvious break-out (`</script><img onerror=…>`) and is inert
+            // against XSS. It does not stop the caption steering the HTML TOKENIZER. A caption
+            // containing `<!--<script` with no later `-->` puts the parser into
+            // script-data-double-escaped state; from there the template's own `</script>` only
+            // steps back to script-data-escaped instead of closing the element, and the rest of the
+            // document — including the viewer bundle — is swallowed as script data. Nothing
+            // executes and nothing leaks; `window.__EXPORT_DATA__` is simply never assigned and the
+            // keepsake opens blank.
+            //
+            // That failure is silent and POST-DISTRIBUTION: the export succeeds, the ZIP is
+            // well-formed, the job writes `done`, /export/status is green, and the host hands out a
+            // file that only fails when a guest double-clicks index.html — in every copy, with no
+            // way to fix it after the fact. Reachable from any guest-authored caption or comment,
+            // since both are embedded in the viewer.
+            //
+            // `<` never appears in JSON structural syntax — only inside string values — so a global
+            // replace is sound, and `<` is valid in both JSON and a JS string literal. One
+            // rule covers `</script`, `<!--` and `<script` together, which is the point: the
+            // previous escape was named for the single case it did handle.
+            //
+            // NOTE this is deliberately only for the INLINED copy. `data.json` is written
+            // separately, in no HTML context, and must stay literal.
+            let safe = escape_json_for_script(data_json);
             // Match the live app's colour theme: inject the same `:root:root{…}` override
             // the app builds at runtime so a rose/sage/custom event exports a rose/sage
             // keepsake (not the embedded default gold). The CSS is generated purely from
@@ -1553,13 +1631,13 @@ async fn write_viewer_with_data(
                 Some(idx) => format!("{}{}{}", &html[..idx], head_inject, &html[idx..]),
                 None => format!("{head_inject}{html}"),
             };
-            let builder = ZipEntryBuilder::new(path.into(), Compression::Deflate);
+            let builder = keepsake_entry(path, Compression::Deflate);
             let mut entry = zip.write_entry_stream(builder).await?;
             let mut cursor = AllowStdIo::new(std::io::Cursor::new(injected.as_bytes()));
             fcopy(&mut cursor, &mut entry).await?;
             entry.close().await?;
         } else {
-            let builder = ZipEntryBuilder::new(path.into(), Compression::Deflate);
+            let builder = keepsake_entry(path, Compression::Deflate);
             let mut entry = zip.write_entry_stream(builder).await?;
             let mut cursor = AllowStdIo::new(std::io::Cursor::new(file.contents()));
             fcopy(&mut cursor, &mut entry).await?;
@@ -1790,6 +1868,62 @@ mod tests {
         }
     }
 
+    /// Every `<` is escaped, whatever it is part of.
+    ///
+    /// PREVENTS the regression to `</` -> `<\\/`, which is named for the one case it handles.
+    /// `<!--<script` with no later `-->` drives the HTML tokenizer into
+    /// script-data-double-escaped state, where the template's own `</script>` no longer closes
+    /// the element — the viewer bundle is swallowed as script data, `__EXPORT_DATA__` is never
+    /// assigned, and the keepsake opens blank in every copy the host has already handed out.
+    #[test]
+    fn no_left_angle_bracket_survives_inlining() {
+        for payload in [
+            r#"{"caption":"<!--<script"}"#,
+            r#"{"caption":"</script><img src=x onerror=alert(1)>"}"#,
+            r#"{"caption":"<!--"}"#,
+            r#"{"caption":"<script>"}"#,
+            r#"{"caption":"a < b"}"#,
+        ] {
+            let escaped = escape_json_for_script(payload);
+            assert!(
+                !escaped.contains('<'),
+                "a surviving `<` can still steer the tokenizer: {escaped}"
+            );
+        }
+    }
+
+    /// The escape must not change what the viewer READS — it is a transport encoding, not a
+    /// sanitiser. A caption is guest-authored text that has to render back exactly.
+    #[test]
+    fn the_payload_still_decodes_to_the_original_value() {
+        // `<` appears only inside JSON string values, never in structural syntax, so a global
+        // replace is sound — this is the assertion that says so.
+        for caption in [
+            "<!--<script",
+            "</script><img src=x onerror=alert(1)>",
+            "a < b und c > d",
+            "ganz normale Bildunterschrift",
+            "Herz <3",
+        ] {
+            let json = serde_json::json!({ "posts": [{ "caption": caption }] }).to_string();
+            let escaped = escape_json_for_script(&json);
+            let back: serde_json::Value =
+                serde_json::from_str(&escaped).expect("the escaped form must still be valid JSON");
+            assert_eq!(
+                back["posts"][0]["caption"].as_str(),
+                Some(caption),
+                "the caption must survive the round trip unchanged"
+            );
+        }
+    }
+
+    /// Nothing else in the document is touched.
+    #[test]
+    fn a_payload_with_no_angle_brackets_is_unchanged() {
+        let json = r#"{"posts":[{"caption":"schönes Foto"}]}"#;
+        assert_eq!(escape_json_for_script(json), json);
+    }
+
     #[test]
     fn a_lone_armed_job_reserves_for_one_archive() {
         // A ViewerOnly regeneration re-arms only the HTML half — reserving for two would refuse

backend/tests/common/mod.rs

@@ -293,6 +293,10 @@ pub async fn set_user_moderation(pool: &PgPool, user_id: Uuid, banned: bool, hid
 
 /// SRC: `services/export.rs::query_uploads` — the visibility filter, verbatim, projected down to
 /// `(id, original_size_bytes)`. This is the row set that ACTUALLY lands in the archives.
+///
+/// Production builds this WHERE from `export_visibility_where!()`, shared with
+/// `estimate_export_bytes`. A copy here can pin the behaviour but CANNOT detect production moving
+/// away from it — that is what sharing the fragment is for, not this.
 pub async fn export_visible_uploads(pool: &PgPool, event_id: Uuid) -> Vec<(Uuid, i64)> {
     sqlx::query_as(
         "SELECT u.id, u.original_size_bytes
@@ -309,7 +313,9 @@ pub async fn export_visible_uploads(pool: &PgPool, event_id: Uuid) -> Vec<(Uuid,
     .expect("export_visible_uploads")
 }
 
-/// SRC: `services/export.rs::estimate_export_bytes` — verbatim.
+/// SRC: `services/export.rs::estimate_export_bytes` — verbatim. Same caveat as above: production
+/// shares its WHERE with `query_uploads` via `export_visibility_where!()`, so these two copies
+/// agreeing proves the behaviour, not the absence of drift.
 pub async fn estimate_export_bytes(pool: &PgPool, event_id: Uuid) -> i64 {
     let (bytes,): (i64,) = sqlx::query_as(
         "SELECT COALESCE(SUM(u.original_size_bytes), 0)::bigint

backend/tests/export_preflight.rs

@@ -16,10 +16,18 @@
 //!
 //! What these tests pin is the ESTIMATE — the part that decides. The arithmetic on top of it lives
 //! in `services/export.rs`'s unit tests; the filesystem selection lives in `is_superseded_archive`.
-//! The risk here is drift: if `query_uploads` ever gains or loses a visibility predicate and
-//! `estimate_export_bytes` doesn't, the preflight silently sizes the wrong gallery. So rather than
-//! restating the filter, these assert the estimate against the row set the archive actually
-//! contains.
+//!
+//! ON DRIFT, precisely, because it is easy to overclaim here. The hazard is that `query_uploads`
+//! (which selects the rows the archives are built from) and `estimate_export_bytes` (which sizes
+//! them) could disagree — and an estimate missing rows the archive writes UNDER-reserves, the one
+//! direction that reintroduces the ENOSPC. **These tests cannot catch that**, and neither can any
+//! test in this harness: both sides here are `SRC:`-marked hand-copies in `tests/common/mod.rs`,
+//! so if production moved and the copies didn't, they would sit still and keep passing.
+//!
+//! That is fixed where it can be — the two queries now share one `export_visibility_where!()`
+//! fragment in `services/export.rs`, so they cannot diverge by construction. What is left for
+//! these tests is what the convention is genuinely good at: pinning the BEHAVIOUR, so a change
+//! that deliberately alters the filter has to come here and say so.
 
 mod common;
 
@@ -29,9 +37,10 @@ use sqlx::PgPool;
 /// The estimate must equal the sum over EXACTLY the rows `query_uploads` returns — computed from
 /// that row set, not from a restatement of its WHERE clause.
 ///
-/// PREVENTS: the two queries drifting apart. An estimate that counts rows the archive skips is
-/// merely pessimistic; one that MISSES rows the archive writes under-reserves, which is the whole
-/// failure being guarded against.
+/// PINS: which uploads the preflight is allowed to count. Each excluded row below is excluded by a
+/// DIFFERENT predicate, so a change that drops or weakens any one of them fails here and has to be
+/// argued for. (It does not detect production drifting away from these copies — see the file
+/// header; `export_visibility_where!()` is what makes that impossible.)
 #[sqlx::test]
 async fn the_estimate_sums_exactly_the_rows_the_archive_will_contain(pool: PgPool) {
     let event_id = seed_event(&pool, "wedding").await;

docker-compose.yml

@@ -17,7 +17,15 @@ services:
     deploy:
       resources:
         limits:
-          memory: 512M
+          # 1G, not 512M. DATABASE_MAX_CONNECTIONS defaults to 30 for a ~100-guest event
+          # (feed polling + SSE + uploads at once), and 30 backends plus Postgres 16's
+          # default shared_buffers leaves very little headroom at 512M. An OOM here does
+          # not degrade one feature — it takes the event down, because every request
+          # path touches the database. Memory is the cheaper knob than shrinking the
+          # pool back and reintroducing the queueing it was raised to fix.
+          #
+          # Raising DATABASE_MAX_CONNECTIONS further means raising this too.
+          memory: 1G
 
   app:
     build:

e2e/specs/03-feed/social-rate-limit.spec.ts

@@ -0,0 +1,136 @@
+/**
+ * Regression guard — likes, comments and comment deletions are rate limited.
+ *
+ * These were the only mutating endpoints in the app with no limit at all. Every other write path
+ * -- upload, join, recover, export, admin login -- carried one; `social.rs` carried none, so the
+ * coverage was asymmetric rather than deliberately open.
+ *
+ * Severity is genuinely low for an invited-guest event, and the amplification worry is contained:
+ * a like does fan an SSE broadcast to every connected client, but the export regeneration a
+ * comment deletion triggers is debounced (REGEN_DEBOUNCE 20s) and superseded workers are inert. So
+ * this closes the gap for symmetry, and the ceiling is set well above anything a real guest
+ * produces -- it bounds a script, not an enthusiastic double-tapper.
+ *
+ * The bucket is shared across all three actions on purpose: separate buckets would let a caller
+ * triple the aggregate write rate just by alternating between them. That is what the second test
+ * pins, and it is the part most likely to be lost in a refactor.
+ *
+ * Keyed per USER, not per IP — at a venue every guest is behind one NAT, so an IP key would hand
+ * the whole party one bucket. Third test.
+ */
+import { test, expect } from '../../fixtures/test';
+import { seedUpload } from '../../helpers/seed';
+import { BASE } from '../../helpers/env';
+
+const like = (jwt: string, uploadId: string) =>
+  fetch(`${BASE}/api/v1/upload/${uploadId}/like`, {
+    method: 'POST',
+    headers: { Authorization: `Bearer ${jwt}` },
+  });
+
+const comment = (jwt: string, uploadId: string, body: string) =>
+  fetch(`${BASE}/api/v1/upload/${uploadId}/comments`, {
+    method: 'POST',
+    headers: { Authorization: `Bearer ${jwt}`, 'Content-Type': 'application/json' },
+    body: JSON.stringify({ body }),
+  });
+
+test.describe('Social — rate limit', () => {
+  test('a burst of likes past the ceiling returns 429 with Retry-After', async ({
+    api,
+    adminToken,
+    guest,
+  }) => {
+    await api.patchConfig(adminToken, {
+      rate_limits_enabled: 'true',
+      social_rate_enabled: 'true',
+      social_rate_per_min: '3',
+    });
+
+    const g = await guest('Tapper');
+    const uploadId = await seedUpload(g.jwt);
+
+    // Sequential, not parallel: a toggle flips state, so ordering matters for the assertion.
+    const statuses: number[] = [];
+    for (let i = 0; i < 5; i++) statuses.push((await like(g.jwt, uploadId)).status);
+
+    expect(statuses.slice(0, 3), 'the first three are within the ceiling').toEqual([200, 200, 200]);
+    expect(statuses.slice(3), 'everything past it is refused').toEqual([429, 429]);
+
+    const limited = await like(g.jwt, uploadId);
+    expect(limited.status).toBe(429);
+    expect(
+      limited.headers.get('retry-after'),
+      'a 429 without Retry-After tells the client nothing about when to come back'
+    ).toBeTruthy();
+  });
+
+  test('likes and comments share one bucket', async ({ api, adminToken, guest }) => {
+    // THE assertion. Per-action buckets would let a caller triple the aggregate write rate by
+    // alternating, which defeats the point of having a ceiling at all.
+    await api.patchConfig(adminToken, {
+      rate_limits_enabled: 'true',
+      social_rate_enabled: 'true',
+      social_rate_per_min: '2',
+    });
+
+    const g = await guest('Mixer');
+    const uploadId = await seedUpload(g.jwt);
+
+    expect((await like(g.jwt, uploadId)).status).toBe(200);
+    expect((await comment(g.jwt, uploadId, 'schön!')).status).toBe(201);
+    // Two writes spent, whichever endpoints they went to.
+    expect(
+      (await comment(g.jwt, uploadId, 'noch eins')).status,
+      'a comment must consume the same budget a like does'
+    ).toBe(429);
+    expect((await like(g.jwt, uploadId)).status).toBe(429);
+  });
+
+  test('one guest hitting the ceiling does not block another', async ({
+    api,
+    adminToken,
+    guest,
+  }) => {
+    // Keyed per user, not per IP. Every request in this suite comes from one address, which is
+    // exactly the venue-NAT shape that made the /join and /feed limits turn guests away.
+    await api.patchConfig(adminToken, {
+      rate_limits_enabled: 'true',
+      social_rate_enabled: 'true',
+      social_rate_per_min: '2',
+    });
+
+    const noisy = await guest('Noisy');
+    const quiet = await guest('Quiet');
+    const uploadId = await seedUpload(noisy.jwt);
+
+    for (let i = 0; i < 3; i++) await like(noisy.jwt, uploadId);
+    expect((await like(noisy.jwt, uploadId)).status).toBe(429);
+
+    expect(
+      (await like(quiet.jwt, uploadId)).status,
+      'a second guest behind the same IP must have their own budget'
+    ).toBe(200);
+  });
+
+  test('flipping social_rate_enabled off bypasses the limit', async ({
+    api,
+    adminToken,
+    guest,
+  }) => {
+    // The toggle has to actually be honoured, or the admin switch is decorative — the failure
+    // mode two other per-area toggles already shipped with.
+    await api.patchConfig(adminToken, {
+      rate_limits_enabled: 'true',
+      social_rate_enabled: 'false',
+      social_rate_per_min: '2',
+    });
+
+    const g = await guest('Unlimited');
+    const uploadId = await seedUpload(g.jwt);
+
+    const statuses: number[] = [];
+    for (let i = 0; i < 6; i++) statuses.push((await like(g.jwt, uploadId)).status);
+    expect(statuses.every((s) => s === 200)).toBe(true);
+  });
+});

e2e/specs/03-feed/video-playback.spec.ts

@@ -40,10 +40,19 @@ test.describe('Video — the lightbox plays it', () => {
     page,
     guest,
     signIn,
+    db,
   }) => {
     const g = await guest('VideoWatcher');
     const id = await seedVideo(g.jwt);
 
+    // The poster assertion below needs the ffmpeg thumbnail to EXIST — the lightbox binds
+    // `poster={upload.thumbnail_url ?? undefined}`, so the attribute is simply absent until
+    // compression finishes. Without this wait the test races the worker and fails against a
+    // cold stack (first run after `stack:down -v`, cold ffmpeg), which is exactly when a suite
+    // is least likely to be believed. The `src` assertion is unconditional; only the poster
+    // needs the wait.
+    await expect.poll(() => db.compressionStatus(id), { timeout: 60_000 }).toBe('done');
+
     await signIn(page, g);
     await page.goto('/feed');
 

e2e/specs/05-admin/config.spec.ts

@@ -68,6 +68,40 @@ test.describe('Admin — config API', () => {
     expect(cfg.privacy_note).toBe(note);
     await api.patchConfig(adminToken, { privacy_note: '' });
   });
+  test('quota_tolerance = 0 is rejected, with a pointer to the real off-switch', async ({
+    api,
+    adminToken,
+  }) => {
+    // Zero is inside the documented 0–1 range and catastrophic: the per-user limit is
+    // `free_disk * tolerance / active_uploaders`, so 0 refuses EVERY upload — mid-event, with
+    // "Du hast dein Upload-Limit für dieses Event erreicht", which names the wrong cause
+    // entirely. `storage_quota_enabled` is what an admin reaching for an off-switch wants.
+    const res = await fetch(
+      (process.env.E2E_FRONTEND_URL ?? 'http://localhost:3101') + '/api/v1/admin/config',
+      {
+        method: 'PATCH',
+        headers: { Authorization: `Bearer ${adminToken}`, 'Content-Type': 'application/json' },
+        body: JSON.stringify({ quota_tolerance: '0' }),
+      }
+    );
+    expect(res.status).toBe(400);
+    expect(
+      (await res.text()).toLowerCase(),
+      'the error must name the switch the admin actually wanted'
+    ).toContain('speicher-quote');
+
+    // The value is untouched — validation fully precedes any write.
+    expect((await api.getConfig(adminToken)).quota_tolerance).toBe('0.75');
+  });
+
+  test('a very small quota_tolerance is still accepted', async ({ api, adminToken }) => {
+    // The mirror. Rejecting 0 must not become a floor: small tolerances are how a large disk is
+    // throttled to a sensible per-guest ceiling, and how the quota specs steer it (~1e-5 on a
+    // 174 GB volume). A floor of 0.01 would forbid real configurations to prevent one typo.
+    await api.patchConfig(adminToken, { quota_tolerance: '0.00001' });
+    expect((await api.getConfig(adminToken)).quota_tolerance).toBe('0.00001');
+    await api.patchConfig(adminToken, { quota_tolerance: '0.75' });
+  });
 });
 
 test.describe('Admin — stats', () => {

e2e/specs/06-export/archive-permissions.spec.ts

@@ -0,0 +1,103 @@
+/**
+ * Regression guard — the keepsake extracts to files a guest can actually open.
+ *
+ * `ZipEntryBuilder::new` leaves the external file attribute at zero, and async_zip's host
+ * compatibility defaults to Unix — so every entry in BOTH archives was written with a stored mode
+ * of 0000. `unzip -Z` showed `?---------` on every line.
+ *
+ * Windows Explorer ignores Unix modes, which is exactly why this survived. On Linux and macOS,
+ * `unzip` faithfully applies what the archive asks for, and the guest gets a folder of photos none
+ * of which they can open — plus an index.html the browser refuses with ERR_ACCESS_DENIED.
+ *
+ * Unconditional: it affected every keepsake ever produced, no hostile input required. And it is
+ * invisible server-side — the export succeeds, the ZIP is well-formed, the job writes `done`,
+ * /export/status is green. The only way to see it is to extract the real artifact and try to read
+ * it, which is what this does.
+ *
+ * Found while chasing an unrelated ERR_ACCESS_DENIED that looked like a Playwright quirk.
+ */
+import { test, expect } from '../../fixtures/test';
+import { execFileSync } from 'node:child_process';
+import { mkdtempSync, writeFileSync, rmSync, readFileSync, statSync, readdirSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { seedUpload } from '../../helpers/seed';
+import { BASE } from '../../helpers/env';
+
+/** Walk every file under `dir`, ignoring the archives we dropped there ourselves. */
+function walk(dir: string, skip: string[] = []): string[] {
+  return readdirSync(dir, { withFileTypes: true }).flatMap((e) => {
+    const p = join(dir, e.name);
+    if (e.isDirectory()) return walk(p, skip);
+    return skip.includes(e.name) ? [] : [p];
+  });
+}
+
+test.describe('Export — the archives extract to readable files', () => {
+  test('every entry in both keepsake archives is owner-readable', async ({ host, guest, db }) => {
+    test.setTimeout(120_000);
+    const bearer = { Authorization: `Bearer ${host.jwt}` };
+
+    const g = await guest('Archivist');
+    const id = await seedUpload(g.jwt, { caption: 'ein Foto' });
+    await expect.poll(() => db.compressionStatus(id), { timeout: 30_000 }).toBe('done');
+
+    expect(
+      (await fetch(`${BASE}/api/v1/host/gallery/release`, { method: 'POST', headers: bearer }))
+        .status
+    ).toBe(204);
+
+    await expect
+      .poll(
+        async () => {
+          const res = await fetch(`${BASE}/api/v1/export/status`, { headers: bearer });
+          const s = await res.json();
+          return s.zip?.status === 'done' && s.html?.status === 'done';
+        },
+        { timeout: 90_000, intervals: [500] }
+      )
+      .toBe(true);
+
+    for (const kind of ['zip', 'html'] as const) {
+      const ticketRes = await fetch(`${BASE}/api/v1/export/ticket`, {
+        method: 'POST',
+        headers: bearer,
+      });
+      const { ticket } = (await ticketRes.json()) as { ticket: string };
+      const dl = await fetch(`${BASE}/api/v1/export/${kind}?ticket=${encodeURIComponent(ticket)}`);
+      expect(dl.status, `downloading the ${kind} archive`).toBe(200);
+
+      const dir = mkdtempSync(join(tmpdir(), `eventsnap-perms-${kind}-`));
+      try {
+        const zipPath = join(dir, 'archive.zip');
+        writeFileSync(zipPath, Buffer.from(await dl.arrayBuffer()));
+
+        // The mode as STORED in the archive — this is what a guest's unzip will apply. Reading it
+        // from the central directory catches the defect even on a filesystem that would mask it.
+        const listing = execFileSync('unzip', ['-Z', zipPath], { encoding: 'utf8' });
+        const modes = listing
+          .split('\n')
+          .filter((l) => /^[?d-][rwx-]{9}\s/.test(l))
+          .map((l) => l.slice(0, 10));
+        expect(modes.length, `${kind}: no entries listed`).toBeGreaterThan(0);
+        for (const m of modes) {
+          expect(m, `${kind}: an entry is stored mode ${m} — the guest cannot open it`).toMatch(
+            /^.r[w-]-/
+          );
+        }
+
+        // And extraction really does produce readable files.
+        execFileSync('unzip', ['-qo', zipPath, '-d', dir]);
+        const files = walk(dir, ['archive.zip']);
+        expect(files.length, `${kind}: nothing extracted`).toBeGreaterThan(0);
+        for (const f of files) {
+          expect(statSync(f).mode & 0o400, `${f} is not owner-readable`).toBeTruthy();
+          // The assertion that matters to a guest: the bytes actually come out.
+          expect(() => readFileSync(f)).not.toThrow();
+        }
+      } finally {
+        rmSync(dir, { recursive: true, force: true });
+      }
+    }
+  });
+});

e2e/specs/06-export/viewer-caption-injection.spec.ts

@@ -0,0 +1,125 @@
+/**
+ * Regression guard — a guest-authored caption cannot brick the offline keepsake.
+ *
+ * The viewer's data is inlined as `<script>window.__EXPORT_DATA__={…};</script>` (it must be:
+ * guests open index.html over file://, where a cross-origin fetch of a sibling data.json is
+ * blocked). Captions and comments are guest text and land in that payload.
+ *
+ * The escape used to be `</` → `<\/`. Against XSS that holds — `</script><img src=x onerror=…>`
+ * round-trips inert. It does NOT stop the caption steering the HTML TOKENIZER: `<!--<script` with
+ * no later `-->` drives the parser into script-data-double-escaped state, where the template's own
+ * `</script>` steps back to script-data-escaped instead of closing the element. Everything after —
+ * including the viewer bundle — is swallowed as script data. Nothing executes and nothing leaks;
+ * `__EXPORT_DATA__` is never assigned and the keepsake renders blank.
+ *
+ * What makes it worth a browser-level test rather than a unit test alone: the failure is SILENT and
+ * POST-DISTRIBUTION. The export succeeds, the ZIP is well-formed, the job writes `done`,
+ * /export/status is green, and the host hands out a file that only fails when a guest
+ * double-clicks it — in every copy, unfixably. It is not visible by reading the escape. It is only
+ * visible by running a real parser over the real artifact, which is what this does: release, pull
+ * the actual Memories.zip, extract index.html, open it over file:// in Chromium, and assert the
+ * viewer actually booted.
+ *
+ * The near-miss worth recording: `<!--<script>alert(1)</script>-->` comes back CLEAN, because the
+ * trailing `-->` returns the parser to script-data state. A probe using the terminated form
+ * quietly repairs the very thing it is testing for. Only the unterminated variant exposes it.
+ */
+import { test, expect } from '../../fixtures/test';
+import { execFileSync } from 'node:child_process';
+import { mkdtempSync, writeFileSync, rmSync } from 'node:fs';
+import { tmpdir } from 'node:os';
+import { join } from 'node:path';
+import { seedUpload } from '../../helpers/seed';
+import { BASE } from '../../helpers/env';
+
+/** Unterminated on purpose — see the header. The terminated form self-repairs. */
+const TOKENIZER_PAYLOAD = '<!--<script';
+/** The classic break-out. Already handled, kept so the fix can never regress on it. */
+const BREAKOUT_PAYLOAD = '</script><img src=x onerror=window.__XSS__=1>';
+
+test.describe('Export — a caption cannot brick the keepsake viewer', () => {
+  test('the exported viewer boots with a tokenizer-hostile caption in it', async ({
+    page,
+    host,
+    guest,
+    db,
+  }) => {
+    test.setTimeout(120_000);
+    const bearer = { Authorization: `Bearer ${host.jwt}` };
+
+    const g = await guest('Trickster');
+    const a = await seedUpload(g.jwt, { caption: TOKENIZER_PAYLOAD });
+    const b = await seedUpload(g.jwt, { caption: BREAKOUT_PAYLOAD });
+    for (const id of [a, b]) {
+      await expect.poll(() => db.compressionStatus(id), { timeout: 30_000 }).toBe('done');
+    }
+
+    expect(
+      (await fetch(`${BASE}/api/v1/host/gallery/release`, { method: 'POST', headers: bearer }))
+        .status
+    ).toBe(204);
+
+    await expect
+      .poll(
+        async () => {
+          const res = await fetch(`${BASE}/api/v1/export/status`, { headers: bearer });
+          return (await res.json()).html?.status;
+        },
+        { timeout: 90_000, intervals: [500] }
+      )
+      .toBe('done');
+
+    const ticketRes = await fetch(`${BASE}/api/v1/export/ticket`, {
+      method: 'POST',
+      headers: bearer,
+    });
+    const { ticket } = (await ticketRes.json()) as { ticket: string };
+    const dl = await fetch(`${BASE}/api/v1/export/html?ticket=${encodeURIComponent(ticket)}`);
+    expect(dl.status).toBe(200);
+
+    const dir = mkdtempSync(join(tmpdir(), 'eventsnap-viewer-'));
+    try {
+      const zipPath = join(dir, 'Memories.zip');
+      writeFileSync(zipPath, Buffer.from(await dl.arrayBuffer()));
+      // Extract the WHOLE archive: index.html pulls in the viewer's own JS/CSS, and the point of
+      // this test is that those later resources are still reachable by the parser.
+      execFileSync('unzip', ['-qo', zipPath, '-d', dir]);
+
+      // file://, not http://. That is how a guest actually opens the keepsake, and it is the
+      // whole reason the data is inlined rather than fetched from a sibling data.json.
+      let xss = false;
+      page.on('dialog', (d) => {
+        xss = true;
+        void d.dismiss();
+      });
+      await page.goto('file://' + join(dir, 'index.html'));
+
+      // 1. The payload was assigned at all. This is the assertion that fails on the old escape —
+      //    the second script block is never reached, so the global stays undefined.
+      const captions = await page.evaluate(() => {
+        const d = (window as unknown as { __EXPORT_DATA__?: { posts?: { caption?: string }[] } })
+          .__EXPORT_DATA__;
+        return d?.posts?.map((p) => p.caption ?? '') ?? null;
+      });
+      expect(captions, '__EXPORT_DATA__ was never assigned — the viewer is bricked').not.toBeNull();
+
+      // 2. The captions survived verbatim. The escape is a transport encoding, not a sanitiser:
+      //    a guest's text has to come back exactly, or we have silently rewritten their words.
+      expect(captions).toContain(TOKENIZER_PAYLOAD);
+      expect(captions).toContain(BREAKOUT_PAYLOAD);
+
+      // 3. And nothing executed.
+      expect(
+        await page.evaluate(() => (window as unknown as { __XSS__?: number }).__XSS__ === 1),
+        'the caption must be inert, not merely non-fatal'
+      ).toBe(false);
+      expect(xss).toBe(false);
+
+      // 4. The viewer actually rendered — the whole document parsed, not just the head. If the
+      //    tokenizer had swallowed the bundle, the body would be empty of viewer output.
+      await expect(page.locator('body')).not.toBeEmpty();
+    } finally {
+      rmSync(dir, { recursive: true, force: true });
+    }
+  });
+});

frontend/src/routes/admin/+page.svelte

@@ -84,9 +84,16 @@
 				{ key: 'feed_rate_enabled', label: 'Feed-Limit aktiv', kind: 'bool' },
 				{ key: 'export_rate_enabled', label: 'Export-Limit aktiv', kind: 'bool' },
 				{ key: 'join_rate_enabled', label: 'Join-Limit aktiv', kind: 'bool' },
+				{ key: 'social_rate_enabled', label: 'Interaktions-Limit aktiv', kind: 'bool' },
 				{ key: 'upload_rate_per_hour', label: 'Upload-Limit pro Stunde', kind: 'number' },
 				{ key: 'feed_rate_per_min', label: 'Feed-Anfragen pro Minute', kind: 'number' },
-				{ key: 'export_rate_per_day', label: 'Export-Downloads pro Tag', kind: 'number' }
+				{ key: 'export_rate_per_day', label: 'Export-Downloads pro Tag', kind: 'number' },
+				{
+					key: 'social_rate_per_min',
+					label: 'Interaktionen pro Minute',
+					kind: 'number',
+					hint: 'Likes, Kommentare und Kommentar-Löschungen zusammen, pro Gast. Bewusst hoch angesetzt — soll ein Skript bremsen, keinen begeisterten Gast.'
+				}
 			]
 		},
 		{
@@ -105,7 +112,20 @@
 					kind: 'bool',
 					hint: 'Reserviert für künftige Anzahl-Limits.'
 				},
-				{ key: 'quota_tolerance', label: 'Toleranz (0–1)', kind: 'number' },
+				{
+					key: 'quota_tolerance',
+					label: 'Speicher-Anteil für Gäste (0–1)',
+					kind: 'number',
+					// "Toleranz (0–1)" with no hint invited exactly the wrong reading — that a higher
+					// number means "warn me later". It is the multiplier in
+					// `floor(freier Speicher × Anteil / aktive Uploader)`, so raising it authorises
+					// guests to fill MORE of the disk, not less.
+					hint:
+						'Anteil des freien Speichers, den alle Gäste zusammen belegen dürfen: ' +
+						'Limit = freier Speicher × Anteil ÷ aktive Uploader. Kein Warnschwellenwert — ' +
+						'ein höherer Wert gibt MEHR Speicher frei. Das Keepsake braucht zusätzlich ' +
+						'etwa das Doppelte der Mediengröße; 0,75 ist der getestete Standard.'
+				},
 				{ key: 'estimated_guest_count', label: 'Geschätzte Gästezahl', kind: 'number' }
 			]
 		},