Guidance for OpenCode (and Claude Code) working under `backend/`. See root `AGENTS.md` for the project-wide architecture diagram, hard constraints, and design system.

- **Backend** (`backend/`): stdlib `net/http` (handful routes, no framework) + Postgres over `jackc/pgx/v5` (pure Go, `CGO_ENABLED=0` -> static binary -> distroless/scratch image). Reverse proxy terminates TLS; Go service listens plain `:8080`.
  Single binary, split into packages under `backend/internal/`: `store`
  (Bookmark type, Postgres persistence, migration runner), `latest` (background
  poller, site parsers, TLS fetcher), `session` (cookie signing, login
  rate limiter), `httpmw` (Auth/Gzip/CORS middleware), `api` (JSON
  bookmark handlers), `userscript` (userscript-serving handler), `web`
  (browser UI handler + `templates/` + `static/`, `go:embed`-ed).
  `backend/main.go` is the composition root — the only place that wires
  packages together into `newRouter`. Root-level `*_test.go` hold
  integration tests that exercise the full router; unit tests for a
  package live beside it under `internal/`.
- **Schema is migration-owned.** `internal/store/migrations/*.sql` is
  `go:embed`-ed and applied on every start by `store.migrate`: one numbered
  file per change, one transaction each, versions recorded in
  `schema_migrations`. Files are **append-only** — editing an applied one
  changes nothing on a database that already ran it. No column probing, no
  data-fixup migrations: both were SQLite-era machinery and are gone.
- **Tests need Docker.** `internal/pgtest` starts one `postgres:17-alpine`
  container per test binary (`TestMain` -> `pgtest.Main`) and hands each test
  its own database (`pgtest.URL(t)`). A package whose tests touch the store
  must have that `TestMain`.
- **Reader-owned store, four tables.** `readers` is keyed by Discord user ID
  and carries the SHA-256 of the Reader's userscript credential plus a
  `token_epoch` (issue #24). Credentials are derived, never stored: `token.Token(TOKEN_KEY, discord_id, epoch)` (HMAC, `internal/token`), and only its SHA-256 sits in `readers.token_sha256`, so install URLs can be rebuilt after any restart while a database leak yields nothing but hashes. The seed creates the **owner** row at startup; its epoch-0 hash is refreshed on every start **only while the row has never been rotated**, so a restart can never resurrect a rotated-away credential. Every other row is created by that Reader's own first login (`Store.EnsureReader`, idempotent on `discord_id`, and it never rewrites an existing row's hash). Rotation is `Store.RotateToken` (epoch bump + hash rewrite in one transaction), driven by the web UI.
  `series` keyed `(site, series_id)`
  (`asura`|`demonic`|`comix`|`kagane`|`novelfull`|`lightnovelworld`) owns the
  shared facts — title, cover, canonical URL, `kind` (`manga`|`novel`),
  Latest Chapter, `latest_checked_at` — and `bookmarks` holds only what
  differs between readers: progress, favourite, lifecycle bucket,
  `updated_at`. A bookmark is keyed `(reader_id, site, series_id)` — no
  surrogate id; the wire `key` is derived as `site:series_id` on read — and
  every store read/write is scoped to the reader it names. Auth resolves the
  acting Reader from the presented credential (`httpmw.Auth`) and nothing
  else — there is no unauthenticated-by-Reader route and no global token; the
  reader id travels in the request context. Sync **last-write-wins**; the wire format
  stays flat (ADR-0004). `Store.Upsert` decomposes one flat body across two
  tables and enforces the ownership rule: client `title`/`series_url`/`cover`
  are written only when the series row is new (ADR-0003).
- **Endpoints:** `GET /bookmarks`, `PUT /bookmarks/{key}` (upsert; see `updated_at` rule below), `DELETE /bookmarks/{key}`, `GET /healthz` (no auth).
- **Web UI:** same binary serve the browser UI on a second
  hostname — `GET /` (list, or login page when no session),
  `GET /auth/discord` + `GET /auth/discord/callback` (Discord OAuth,
  ADR-0002), `POST /logout`, `GET /static/*`, htmx fragment endpoints
  under `/ui/*`. Templates + assets `go:embed`-ed under
  `backend/internal/web/`, so `backend/Dockerfile` must copy the whole
  `internal/` tree, not just `*.go`. Sessions are rows in the `sessions`
  table: the cookie carries only an opaque id, looked up (and expiry-
  checked) on every request, and deleting the row revokes the session.
  Guild membership *is* registration (issue #27): `discordCallback` gates on
  membership (and `DISCORD_REQUIRED_ROLE` when set) and then calls
  `Store.EnsureReader`, so a refusal creates nothing and a returning Reader
  reuses their row. The owner is the only Reader with administrative reach:
  `POST /readers/{id}/revoke` (404 for anyone else) drops that Reader's
  sessions, and the `readers` panel renders only on the owner's page.
  A Reader with no bookmarks at all sees `listView.Fresh`, whose empty state
  offers both install links instead of describing a filter.
  UI mutations read-modify-write
  through `Store.Get` + `Store.Upsert` so `updated_at` rule stays one
  place. See `docs/superpowers/specs/2026-07-25-web-ui-design.md`.
  **Design-tool caveat:** templates link `/static/style.css` root-absolutely
  (correct — served from `/`), but impeccable detector resolves
  stylesheet href with `path.resolve(fileDir, href)`, drops directory
  on leading `/` and silently skip file. Relative href don't help
  either: template's directory isn't its served path. So
  `detect.mjs backend/internal/web/templates` reports **false clean** —
  always pass `backend/internal/web/static` too. One finding there,
  `overused-font` on "Instrument Serif", deliberate identity choice, not debt.
- **Every action that moves series out of list is confirm-gated.**
  Archive, finish, remove each open own `.confirm-row` disclosure
  (`toggleConfirmRow(key, kind)` in `filter.js`, `kind` ∈
  `archive|finish|remove`); restore fire instantly since it's the reversal.
  Remove's row wear ember wash, two reversible ones wear `.calm` grey.
  `--ember` stay reserved for new-chapter signal: busy bar and inline
  error use `--mute`.
- **Latest-chapter poller:** ticker goroutine in same binary re-check
  each bookmarked series' newest published chapter from backend's own
  network access, so `latest_chapter` stay fresh when user not
  browsing. Second, parallel signal — userscript keep own
  `maybeCaptureLatestOnSeriesPage`/`backgroundRefreshLatest` logic unchanged.
  Two independent clocks: per-series cooldown (`series.latest_checked_at`,
  enforced by `Store.DueForLatestCheck`'s WHERE clause) and wake interval.
  The poller walks **Series, not Bookmarks** — a series referenced by several
  bookmarks is fetched once per cycle, and the due queue orders
  `reader_count DESC, latest_checked_at ASC` (ADR-0003). Series row stamped
  *before* fetch so broken series wait out full cooldown instead of retrying
  every tick; found chapter written straight to the series row via
  `Store.SetLatestChapter`, so a bookmark's `updated_at` — and the list
  order — is never touched.
  Fetches use `bogdanfinn/tls-client` with Chrome profile as defence in depth
  against fingerprint-based blocking; any failure log and skip. kagane and
  novelfull sit behind Cloudflare JavaScript challenges the TLS client can't
  clear, so they are fetched over CDP via `BROWSER_WS_URL`; kagane is simply
  not polled when that's unset, while novelfull falls back to a plain-TLS
  attempt — its challenge is a live time-varying fact, and its cover bytes
  never need the browser. See
  `docs/superpowers/specs/2026-07-26-server-latest-chapter-polling-design.md`.
  The poller's series write is a single-column UPDATE
  (`Store.SetLatestChapter`), not a read-modify-write of the whole bookmark:
  it cannot revert read progress or move `updated_at`, so the old
  stale-re-read race is gone with the Get+Upsert flow.
- **Covers are acquired at creation, then served from our own origin
  (ADR-0007):** the first Bookmark of a Series fires `Store.OnSeriesCreated`,
  which `latest.Acquirer` turns into one series-page fetch yielding both the
  Latest Chapter and the cover URL; the bytes then go through
  `latest.CoverBytesFetcher` into `Store.SetSeriesCover`. It runs in a
  goroutine — the Reader's PUT must neither block on a Site nor fail with one
  — and every failure is logged and dropped, leaving the Bookmark intact. The
  wire's `cover` is the absolute `PUBLIC_BASE_URL + /covers/{sha256}` once
  bytes exist and `""` before, never an address that 404s. `GET /covers/{addr}`
  is public and uncredentialed: the userscript renders it on a Site's origin,
  where no cookie or token of ours travels. A client-sent `cover` is decoded
  and discarded, permanently (ADR-0004 compatibility).
  Browser-backed Sites join the same pipeline (issue #62): kagane pages *and*
  cover bytes go through the browser sidecar (nothing falls back to a plain
  fetch, which would only retrieve a challenge page), while novelfull needs
  the browser only for its HTML — the cover URL comes out of the
  browser-fetched page and the bytes go over plain TLS. With no browser
  configured, kagane Covers are simply absent; novelfull still gets one — at
  creation and on the poll — when its page body happens to answer a plain
  request (the challenge is a live time-varying fact). The old kagane-only
  serving path (`/img/kagane/{id}`, template rewrite, `CoverFetcher`) is gone
  (issue #63): the one public route serves every Site.
- **`updated_at` drives list order, so moves only on real reading progress:** server apply its timestamp when row new or `last_chapter_num` changes, else keep stored value — favouriting series or recording newly published chapter must not reorder list. `PUT` therefore returns row **as stored**, clients must adopt that response rather than own payload. See `plans/2026-07-25-bookmark-list-favorites-design.md` §4.
- **Lifecycle buckets:** `status` on each bookmark is `reading` | `archived` |
  `finished`, orthogonal to `favorite`. Archived and finished appear only in
  own tab — not in All, Updated, Favourites, or recent strip. Poller keeps
  checking archived series and skip finished ones. `finished` settable
  only from web UI; `PUT /bookmarks/{key}` reject it with 400.
  **Empty incoming status means "keep stored one"** — resolved on the
  `VALUES` side of `Store.Upsert`, not conflict clause, since
  `excluded.*` is post-evaluation row and default applied there would
  wipe bucket on every PUT from client that predates column. See
  `docs/superpowers/specs/2026-07-27-status-buckets-design.md`.
- **Config via env:** `TOKEN_KEY` (derives every Reader's userscript credential;
  required), `OWNER_DISCORD_ID` (seeds the owner Reader — the administrator and
  the owner of every pre-registration bookmark; required),
  `ALLOWED_ORIGINS` (comma list),
  `DATABASE_URL` (Postgres connection URL, required — no default),
  `COVER_DIR` (required filesystem volume for content-addressed Cover bytes),
  `PUBLIC_BASE_URL` (required origin this deployment answers on, trailing
  slash trimmed; every Cover URL on the wire is built from it, absolute
  because the userscript renders on a Site's origin — ADR-0007),
  `PORT` (default `8080`), `DISCORD_CLIENT_ID`/`_CLIENT_SECRET`/`_GUILD_ID`/
  `_REDIRECT_URI` (required; Discord OAuth for the browser UI),
  `DISCORD_REQUIRED_ROLE` (optional role gate, empty by default),
  `DISCORD_API_BASE` (default `https://discord.com/api/v10`),
  `LATEST_CHAPTER_POLL_ENABLED`/`_COOLDOWN`/`_BROWSER_COOLDOWN`/`_INTERVAL`/
  `_BATCH`/`_STAGGER` (background latest-chapter poller; defaults on,
  `1h` plain-TLS cooldown, `6h` browser cooldown, `10m`/`14`/`20s`; both
  cooldowns have a `15m` floor). The browser cooldown is longer for cost, not
  for safety: a challenged page costs seconds of a serialized single-tab
  browser, while a plain read costs one request. It buys no documented
  reduction in challenge risk — free-plan zones have no bot score and no
  published per-IP rate input, and `cf_clearance` expires in 30 minutes so
  every cadence at or above 1h re-solves anyway —
  `docs/research/cloudflare-bot-scoring-and-poll-cadence.md`.
  `USERSCRIPT_PATH` and `NOVEL_USERSCRIPT_PATH` (files served at
  `/u/{token}/manga-bookmark.user.js` and `/u/{token}/novel-bookmark.user.js`,
  defaults `/userscript/manga-bookmark.user.js` and
  `/userscript/novel-bookmark.user.js`, both supplied by bindmount; the
  `__API_TOKEN__` placeholder inside them is substituted with the requesting
  Reader's credential at serve time).
  `BROWSER_WS_URL` (CDP endpoint of the browser, which runs on a **separate
  machine** and is reached over the tailnet — ADR-0006, `chrome/docker-compose.yml`.
  Used by the poller for kagane and novelfull page fetches and by the cover
  pipeline for kagane's image bytes (the browser is the only route that clears
  the challenge kagane serves its covers behind); unset — the default —
  disables browser polling and leaves kagane Covers blank until stored bytes
  exist. Must be a tailnet IP, never a hostname: Chrome's DevTools handler 500s
  `/json/version` for any Host that isn't an IP or `localhost`).
- **No per-Site cover path (issue #63):** every Cover — all six Sites — is
  served by the one public `GET /covers/{addr}` route from content-addressed
  bytes. There is no proxy, no per-Site rewrite, no second place that decides
  a Cover's renderable address: the wire `cover` is it. The only place a Site
  name still appears in cover code is the extraction module (`latest`), where
  kagane's image URLs are claimed by `browserOnlyCoverURL` — they answer a
  plain fetch with a challenge and `cross-origin-resource-policy: same-origin`;
  every other Site's CDN answers plain TLS. Templates render `.Cover` — the
  wire value — never anything else.
- **Web UI also owns:** session-gated `GET /install/{manga,novel}-bookmark.user.js`
  (renders the bindmounted script with the acting Reader's derived credential
  substituted in — the credential never appears in page markup, the address
  bar, or a redirect; `?download=1` adds `Content-Disposition: attachment` for
  mobile Violentmonkey, which ignores a `.user.js` navigation) and
  `POST /rotate-token` (atomic epoch bump + hash
  rewrite; invalidates every installed copy, so the panel warns to reinstall
  on all devices).
  Owner-only `POST /readers/{id}/revoke` (drops one Reader's session rows and
  re-renders the `readers` panel; 404 for any non-owner) is the only route that
  reaches across Readers.