v3: the backend gets a test suite, and the bugs it turned up are fixed — deno task test runs 186 tests over api/ in about 18s, against a throwaway database and uploads directory (GERBEUR_DB_PATH and GERBEUR_UPLOADS_DIR now override the defaults; api/test/setup.ts sets them before any app module loads), with requests sent through the whole middleware stack in-process via app.handle, outbound fetches and DNS stubbed, and the socket tests on a real Oak listener since an upgraded request has no response for handle() to return. It covers auth (token purposes, revocation after a password change, live roles, login rate limiting, invites claimed once even under parallel registrations, password resets), dumps end to end (create, privacy, by-url matching on the canonical key, backlinks, categories, edits, file replacement, thumbnails, refresh, delete), file serving headers and ranges, attachments, avatars, comments and likes, playlists, follows and feeds, notifications and mentions, categories, search, chat cursors and read markers, link previews and the SSRF guard on every redirect hop, the Bandcamp and YouTube resolvers, migrations (a fresh schema is left untouched; the data rewrites in 0004/0005 and 0010–0013 do what they say), CORS, OG tags, static caching, and the WebSocket protocol. Fixed along the way: an unknown category id on a new dump returned 400 but kept the dump row, and for a file dump deleted the file while keeping the row; an edit or file replacement with one was half-applied before the 400 — categories are now checked before anything is written. A suffix range (bytes=-3) was read as an end offset and got a 416 instead of the last three bytes. Reordering a playlist accepted a list naming a member twice. verifyPassword threw on a stored hash without a salt instead of answering false. And a request with no Accept-Encoding, which RFC 9110 lets a server treat as accepting anything, was sent the brotli sibling; curl and bots now get the plain file.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

api/services/category-service.ts

@@ -182,13 +182,11 @@ export function deleteCategory(id: string): void {
 }
 
 /**
- * Replace the set of categories a dump belongs to. Unknown category ids are
- * rejected. An empty list clears all category assignments.
+ * Throws a 400 unless every id names an existing category. Callers that write
+ * anything else first (a dump row, an uploaded file) run this before those
+ * writes, so a bad id can't leave them half-done.
  */
-export function setDumpCategories(
-  dumpId: string,
-  categoryIds: string[],
-): void {
+export function assertCategoriesExist(categoryIds: string[]): void {
   const unique = [...new Set(categoryIds)];
 
   if (unique.length > 0) {
@@ -204,6 +202,18 @@ export function setDumpCategories(
       );
     }
   }
+}
+
+/**
+ * Replace the set of categories a dump belongs to. Unknown category ids are
+ * rejected. An empty list clears all category assignments.
+ */
+export function setDumpCategories(
+  dumpId: string,
+  categoryIds: string[],
+): void {
+  assertCategoriesExist(categoryIds);
+  const unique = [...new Set(categoryIds)];
 
   db.prepare(`DELETE FROM dump_categories WHERE dump_id = ?;`).run(dumpId);
   const insert = db.prepare(