backend/AGENTS.md

@@ -136,12 +136,12 @@ Guidance for OpenCode (and Claude Code) working under `backend/`. See root `AGEN
   behind the same challenge as its pages and with
   `cross-origin-resource-policy: same-origin`, so no `<img>` on the web UI's
   origin can load one — not even from a browser holding the clearance cookie
-  (verified 2026-08-08). `Bookmark.CoverURL` rewrites a stored kagane
-  `og:image` to `/img/kagane/{id}`, served by `internal/web/cover.go` through
-  `latest.BrowserFetcher.Image` and memoised in-process. The templates render
-  `.CoverURL`, never `.Cover`. The id is matched against a UUID regex before it
-  reaches the browser: the stored value is client-supplied, so an unchecked one
-  is an SSRF primitive pointed at the deployment's own network.
+  `og:image` to `/img/kagane/{id}`. `internal/web/cover.go` reads the persistent
+  `covers` table first, then fetches a miss through `latest.BrowserFetcher.Image`.
+  The templates render `.CoverURL`, never `.Cover`. The id is matched against a
+  UUID regex before it reaches the browser: the stored value is client-supplied,
+  so an unchecked one is an SSRF primitive pointed at the deployment's own
+  network.
 - **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

backend/cover_test.go

@@ -2,11 +2,15 @@ package main
 
 import (
 	"context"
+	"crypto/sha256"
 	"errors"
 	"net/http"
 	"net/http/httptest"
 	"sync/atomic"
 	"testing"
+
+	"bookmarkmanager/backend/internal/pgtest"
+	"bookmarkmanager/backend/internal/store"
 )
 
 // fakeCovers stands in for the headless browser. It counts calls so the test
@@ -95,6 +99,41 @@ func TestKaganeCoverServesStoredBytesWithoutBrowser(t *testing.T) {
 	}
 }
 
+func TestKaganeCoverServesPersistedBytesAfterRestart(t *testing.T) {
+	url := pgtest.URL(t)
+	owner := store.Owner{
+		DiscordID: "cover-owner",
+		TokenHash: sha256.Sum256([]byte("cover-owner-token")),
+	}
+	first, err := store.Open(url, owner)
+	if err != nil {
+		t.Fatalf("Open: %v", err)
+	}
+	if err := first.PutKaganeCover(testCoverID, []byte("survives-restart"), "image/jpeg"); err != nil {
+		first.Close()
+		t.Fatalf("PutKaganeCover: %v", err)
+	}
+	if err := first.Close(); err != nil {
+		t.Fatalf("close first store: %v", err)
+	}
+
+	second, err := store.Open(url, owner)
+	if err != nil {
+		t.Fatalf("reopen: %v", err)
+	}
+	defer second.Close()
+	cf := &fakeCovers{err: errors.New("browser must not be called after restart")}
+	cfg := testConfig()
+	cfg.Covers = cf
+	rr := getCover(t, newRouter(second, cfg), "/img/kagane/"+testCoverID, sessionCookie(t, second))
+	if rr.Code != http.StatusOK || rr.Body.String() != "survives-restart" {
+		t.Fatalf("restarted request = (%d, %q), want (200, survives-restart)", rr.Code, rr.Body.String())
+	}
+	if got := cf.calls.Load(); got != 0 {
+		t.Fatalf("fetcher called %d times after restart, want 0", got)
+	}
+}
+
 // The proxy reaches a headless browser, so it is not open to the internet.
 func TestKaganeCoverRequiresSession(t *testing.T) {
 	cf := &fakeCovers{body: []byte("x"), contentType: "image/webp"}
@@ -147,9 +186,11 @@ func TestKaganeCoverRejectsBadInput(t *testing.T) {
 			if rr.Code != http.StatusNotFound {
 				t.Fatalf("status = %d, want 404", rr.Code)
 			}
-			if _, _, ok, err := st.GetKaganeCover(testCoverID); err != nil {
+			_, _, ok, err := st.GetKaganeCover(tc.id)
+			if err != nil {
 				t.Fatalf("GetKaganeCover after rejection: %v", err)
-			} else if ok {
+			}
+			if ok {
 				t.Fatal("rejected cover was persisted")
 			}
 		})

backend/internal/web/cover.go

@@ -9,9 +9,9 @@ import (
 )
 
 // CoverFetcher retrieves one kagane cover by image id. Satisfied by
-// latest.BrowserFetcher, and nil when BROWSER_WS_URL is unset — which leaves
-// kagane covers exactly as unavailable as they were before this endpoint
-// existed, rather than hanging a request on a fetcher that cannot run.
+// latest.BrowserFetcher. It is nil when BROWSER_WS_URL is unset; uncached
+// covers are then unavailable, while covers already stored by the backend
+// remain available without a browser.
 type CoverFetcher interface {
 	Image(ctx context.Context, imageID string) (body []byte, contentType string, err error)
 }
@@ -52,11 +52,13 @@ func (h *Handler) kaganeCover(w http.ResponseWriter, r *http.Request) {
 		http.NotFound(w, r)
 		return
 	}
-	if body, contentType, ok, err := h.store.GetKaganeCover(id); err != nil {
+	body, contentType, ok, err := h.store.GetKaganeCover(id)
+	if err != nil {
 		log.Printf("read kagane cover %s: %v", id, err)
 		http.Error(w, "internal error", http.StatusInternalServerError)
 		return
-	} else if ok {
+	}
+	if ok {
 		writeCover(w, body, contentType)
 		return
 	}
@@ -67,7 +69,7 @@ func (h *Handler) kaganeCover(w http.ResponseWriter, r *http.Request) {
 
 	ctx, cancel := context.WithTimeout(r.Context(), coverTimeout)
 	defer cancel()
-	body, contentType, err := h.covers.Image(ctx, id)
+	body, contentType, err = h.covers.Image(ctx, id)
 	if err != nil {
 		log.Printf("kagane cover %s: %v", id, err)
 		http.NotFound(w, r)