fix(latest): parse Kagane series cover IDs

backend/internal/latest/sites.go

@@ -165,16 +165,24 @@ var singleQuotedMetaAttrRe = regexp.MustCompile(`(?is)([a-z][a-z0-9:_-]*)\s*=\s*
 // the target detail entry avoids matching posters from recommended results.
 var comixInitialDataRe = regexp.MustCompile(`(?is)<script\b[^>]*\bid\s*=\s*["']initial-data["'][^>]*>(.*?)</script>`)
 
-// kagane's browser-fetched series response carries this published cover URL.
-// Decode the top-level field, not merely an image-shaped URL elsewhere in JSON.
+// kagane's browser-fetched series response publishes cover image IDs under
+// series_covers. The API's canonical compressed image route is the only URL
+// form accepted by the store and browser fetcher; no rendition is guessed.
 func kaganeCoverURL(body string) string {
 	var response struct {
-		Cover string `json:"cover"`
+		SeriesCovers []struct {
+			ImageID string `json:"image_id"`
+		} `json:"series_covers"`
 	}
 	if err := json.Unmarshal([]byte(body), &response); err != nil {
 		return ""
 	}
-	return publishedCoverURL(response.Cover)
+	for _, cover := range response.SeriesCovers {
+		if kaganeImageIDRe.MatchString(cover.ImageID) {
+			return "https://kagane.to/api/v2/image/" + cover.ImageID + "/compressed"
+		}
+	}
+	return ""
 }
 
 func comixCoverURL(seriesURL, body string) string {

backend/internal/latest/sites_test.go

@@ -92,8 +92,8 @@ const demonicCoverFixture = `<meta property="og:image" content="https://readermc
 // nested IDs inside that object; no og:image is present.
 const comixCoverFixture = `<script type="application/json" id="initial-data">{"queries":{"[\"manga\",\"recommended\",\"n8we\",1]":{"poster":{"medium":"https://static.comix.to/recommended@280.jpg","large":"https://static.comix.to/recommended.jpg"}},"[\"manga\",\"detail\",\"n8we\"]":{"chapters":[{"hid":"nested"}],"poster":{"medium":"https://static.comix.to/039d/i/1/34/6a6742bf15736@280.jpg","large":"https://static.comix.to/039d/i/1/34/6a6742bf15736.jpg"}}}}</script>`
 
-// Trimmed from GET https://kagane.to/api/v2/series/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b on 2026-08-09.
-const kaganeCoverFixture = `{"books":[{"cover":"https://kagane.to/api/v2/image/00000000-0000-0000-0000-000000000000/compressed"}],"cover":"https://kagane.to/api/v2/image/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b/compressed"}`
+// Trimmed from GET https://kagane.to/api/v2/series/019fe11a-8670-7cf3-8343-0b02057d3787 on 2026-08-10.
+const kaganeCoverFixture = `{"series_covers":[{"cover_id":"019fe11a-84d1-714b-9cf4-2827f277f3c0","language":"en","volume_number":"1","chapter_number":null,"note":null,"image_id":"019fe11a-84c3-7fc3-a84b-88787374b617"}]}`
 
 // Trimmed from https://novelfull.com/reverend-insanity.html on 2026-08-10.
 const novelfullCoverFixture = `<meta name="image" content="https://novelfull.com/uploads/webp/novel/reverend-insanity-82661d911a.webp">`
@@ -127,9 +127,9 @@ func TestCoverFrom(t *testing.T) {
 			wantCover: "https://static.comix.to/039d/i/1/34/6a6742bf15736@280.jpg",
 		},
 		{
-			name: "kagane reads API cover field",
+			name: "kagane reads API cover image ID",
 			site: "kagane", body: kaganeCoverFixture, wantOK: true,
-			wantCover: "https://kagane.to/api/v2/image/019f84bc-9ba0-7ed9-86f5-8b905ec7c28b/compressed",
+			wantCover: "https://kagane.to/api/v2/image/019fe11a-84c3-7fc3-a84b-88787374b617/compressed",
 		},
 		{
 			name: "novelfull reads image metadata",