v4: what the server and the client both state is declared once — several rules were written out in two or more files, some already drifting apart. A link's site name (its host without www.) was computed in five places, now shared/url.ts's siteHost; dumpFileVersion, which the frontend and the server had to keep equal by hand, is one function in shared/dump.ts; the Markdown flattening of the chat's reply previews and the digest's quotes is shared/markdown.ts's markdownToPlainText, so the digest also keeps an image's alt text; an attachment's URL and how to find one in a text are shared/attachment.ts, which the editor, Markdown and attachment-service read, its id pattern the new UUID_RE that the file and thumbnail routes check ids with. On the server, the Bandcamp, YouTube playlist and link preview caches use one TtlCache (api/lib/ttl-cache.ts) instead of three copies of the same expiry and eviction; the link previews' theme-color and the emails' theme tokens read colours with one parser (api/lib/css-color.ts), and a transparent theme-color now gives no tint; the WebSocket route sends through ws-service's send, the welcome included, so it is type-checked; fetch.ts strips an IPv6 literal's brackets with public-address's bareHostname; and a category's slug is checked by the same validateSlug as a dump's, with its own length. The migrations keep their frozen copies, as they document. 272 backend tests and 677 frontend tests pass, and deno check, tsc, eslint and doc:lint are clean.

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

api/remote/fetch.ts

@@ -7,7 +7,11 @@
  * @module
  */
 
-import { isPrivateHostname, resolvePublicAddress } from "./public-address.ts";
+import {
+  bareHostname,
+  isPrivateHostname,
+  resolvePublicAddress,
+} from "./public-address.ts";
 import { isSelfUrl } from "../lib/self-url.ts";
 
 const FETCH_HEADERS = {
@@ -43,7 +47,7 @@ async function fetchViaCurl(
         "--proto",
         "=http,https",
         "--resolve",
-        `${url.hostname.replace(/^\[(.*)\]$/, "$1")}:${port}:${pinned}`,
+        `${bareHostname(url)}:${port}:${pinned}`,
         "--max-time",
         String(Math.ceil(timeoutMs / 1000)),
         // curl fails on a larger file rather than stopping at a cap, so this is