Web UI: music channel, posted-to-Matrix glow, redesigned index, AVIF thumbnails

- Add music as a fourth channel (nav + theme color)
- Glowing themed border on cards that have been posted to Matrix
- Replace per-channel index sections with: "Pete just posted" strip,
  channel dashboard (last post, 24h count, totals), unified latest feed
- /img proxy: SSRF-guarded thumbnail re-encoder that resizes to 800px
  and runs avifenc -q 45, cached under data/img-cache

go.mod

@@ -33,6 +33,7 @@ require (
 	go.mau.fi/util v0.9.9 // indirect
 	golang.org/x/crypto v0.52.0 // indirect
 	golang.org/x/exp v0.0.0-20260508232706-74f9aab9d74a // indirect
+	golang.org/x/image v0.41.0 // indirect
 	golang.org/x/net v0.55.0 // indirect
 	golang.org/x/sys v0.45.0 // indirect
 	golang.org/x/text v0.37.0 // indirect

go.sum

@@ -76,6 +76,8 @@ golang.org/x/crypto v0.52.0 h1:RMs7fP2rXdep0CftQlK8Uf+kibLm7qkCcradZWYz988=
 golang.org/x/crypto v0.52.0/go.mod h1:1QgfPxDqh0T2M/elOJtp9RvuR95kVjir0e6/BvEmGbc=
 golang.org/x/exp v0.0.0-20260508232706-74f9aab9d74a h1:+3jdDGGB8NGb1Zktc737jlt3/A5f6UlwSzmvqUuufxw=
 golang.org/x/exp v0.0.0-20260508232706-74f9aab9d74a/go.mod h1:d2fgXJLVs4dYDHUk5lwMIfzRzSrWCfGZb0ZqeLa/Vcw=
+golang.org/x/image v0.41.0 h1:8wS72eGJMJaBxK6okTzd4WaXumUlTVlb753MlsSvTCo=
+golang.org/x/image v0.41.0/go.mod h1:uIc348UZMSvS5Z65CVZ7iDPaNobNFEPeJ4kbqTOszmA=
 golang.org/x/mod v0.6.0-dev.0.20220419223038-86c51ed26bb4/go.mod h1:jJ57K6gSWd91VN4djpZkiMVwK6gcyfeH4XE8wZrZaV4=
 golang.org/x/mod v0.8.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=
 golang.org/x/mod v0.12.0/go.mod h1:iBbtSCu2XBx23ZKBPSOrRkjjQPZFPuis4dIYUhu/chs=

internal/storage/queries.go

@@ -220,22 +220,76 @@ func GetNewestPostableStoryByChannel(channel string) (*Story, error) {
 // channels (_discarded, _duplicate) are excluded.
 func ListClassifiedByChannel(channel string, limit, offset int) ([]Story, error) {
 	rows, err := Get().Query(
-		`SELECT guid, headline, lede, image_url, article_url, source, platforms, channel, seen_at
+		`SELECT s.guid, s.headline, s.lede, s.image_url, s.article_url, s.source, s.platforms, s.channel, s.seen_at,
-		 FROM stories
+		        EXISTS(SELECT 1 FROM post_log p WHERE p.guid = s.guid) AS posted
-		 WHERE classified = 1
+		 FROM stories s
-		   AND channel = ?
+		 WHERE s.classified = 1
-		 ORDER BY seen_at DESC
+		   AND s.channel = ?
+		 ORDER BY s.seen_at DESC
 		 LIMIT ? OFFSET ?`, channel, limit, offset)
 	if err != nil {
 		return nil, err
 	}
 	defer rows.Close()
 	var out []Story
+	for rows.Next() {
+		var s Story
+		if err := rows.Scan(&s.GUID, &s.Headline, &s.Lede, &s.ImageURL, &s.ArticleURL, &s.Source, &s.Platforms, &s.Channel, &s.SeenAt, &s.Posted); err != nil {
+			return nil, err
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// ListAllClassified returns up to `limit` classified stories across all real
+// channels, newest first. Sentinel channels are excluded.
+func ListAllClassified(limit, offset int) ([]Story, error) {
+	rows, err := Get().Query(
+		`SELECT s.guid, s.headline, s.lede, s.image_url, s.article_url, s.source, s.platforms, s.channel, s.seen_at,
+		        EXISTS(SELECT 1 FROM post_log p WHERE p.guid = s.guid) AS posted
+		 FROM stories s
+		 WHERE s.classified = 1
+		   AND s.channel IS NOT NULL
+		   AND s.channel NOT IN ('_discarded', '_duplicate')
+		 ORDER BY s.seen_at DESC
+		 LIMIT ? OFFSET ?`, limit, offset)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Story
+	for rows.Next() {
+		var s Story
+		if err := rows.Scan(&s.GUID, &s.Headline, &s.Lede, &s.ImageURL, &s.ArticleURL, &s.Source, &s.Platforms, &s.Channel, &s.SeenAt, &s.Posted); err != nil {
+			return nil, err
+		}
+		out = append(out, s)
+	}
+	return out, rows.Err()
+}
+
+// ListRecentlyPosted returns up to `limit` stories that have been posted to
+// Matrix, ordered by post time (newest first). Posted is always true.
+func ListRecentlyPosted(limit int) ([]Story, error) {
+	rows, err := Get().Query(
+		`SELECT s.guid, s.headline, s.lede, s.image_url, s.article_url, s.source, s.platforms, s.channel, s.seen_at
+		 FROM stories s
+		 JOIN post_log p ON p.guid = s.guid
+		 GROUP BY s.guid
+		 ORDER BY MAX(p.posted_at) DESC
+		 LIMIT ?`, limit)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []Story
 	for rows.Next() {
 		var s Story
 		if err := rows.Scan(&s.GUID, &s.Headline, &s.Lede, &s.ImageURL, &s.ArticleURL, &s.Source, &s.Platforms, &s.Channel, &s.SeenAt); err != nil {
 			return nil, err
 		}
+		s.Posted = true
 		out = append(out, s)
 	}
 	return out, rows.Err()
@@ -250,6 +304,20 @@ func CountClassifiedByChannel(channel string) (int, error) {
 	return n, err
 }
 
+// IsKnownImageURL reports whether any story has this exact image_url. Used
+// by the thumbnail proxy to guard against arbitrary URL fetches.
+func IsKnownImageURL(url string) bool {
+	if url == "" {
+		return false
+	}
+	var n int
+	if err := Get().QueryRow(`SELECT COUNT(*) FROM stories WHERE image_url = ? LIMIT 1`, url).Scan(&n); err != nil {
+		slog.Error("IsKnownImageURL query failed", "err", err)
+		return false
+	}
+	return n > 0
+}
+
 // GetRoundRobinState returns the last channel posted by the round-robin
 // scheduler and the timestamp of that tick. Empty string + 0 if no state yet.
 func GetRoundRobinState() (lastChannel string, lastTickAt int64, err error) {

internal/storage/types.go

@@ -15,4 +15,5 @@ type Story struct {
 	Channel      string
 	Classified   bool
 	SeenAt       int64
+	Posted       bool // true if this story has been posted to Matrix (joined from post_log)
 }

internal/web/handlers.go

@@ -21,6 +21,8 @@ type StoryView struct {
 	ArticleURL string
 	Source     string
 	SeenAt     time.Time
+	Posted     bool
+	Channel    string // channel slug; also the theme key
 }
 
 func toView(s storage.Story) StoryView {
@@ -31,6 +33,8 @@ func toView(s storage.Story) StoryView {
 		ArticleURL: s.ArticleURL,
 		Source:     s.Source,
 		SeenAt:     time.Unix(s.SeenAt, 0),
+		Posted:     s.Posted,
+		Channel:    s.Channel,
 	}
 }
 
@@ -54,12 +58,17 @@ type channelPage struct {
 
 type indexPage struct {
 	pageData
-	Sections []indexSection
+	JustPosted []StoryView
+	Stats      []channelStat
+	Latest     []StoryView
 }
 
-type indexSection struct {
+type channelStat struct {
-	Channel Channel
+	Channel       Channel
-	Stories []StoryView // top 3 per channel
+	LastPostedAt  time.Time // zero if never posted
+	HasLastPosted bool
+	PostsToday    int
+	Total         int
 }
 
 func (s *Server) base() pageData {
@@ -70,21 +79,56 @@ func (s *Server) base() pageData {
 }
 
 func (s *Server) handleIndex(w http.ResponseWriter, _ *http.Request) {
-	sections := make([]indexSection, 0, len(channels))
+	const (
-	for _, ch := range channels {
+		justPostedLimit = 6
-		rows, err := storage.ListClassifiedByChannel(ch.Slug, 4, 0)
+		latestLimit     = 16
-		if err != nil {
+	)
-			slog.Error("web: list failed", "channel", ch.Slug, "err", err)
+
-			http.Error(w, "internal error", http.StatusInternalServerError)
+	postedRows, err := storage.ListRecentlyPosted(justPostedLimit)
-			return
+	if err != nil {
-		}
+		slog.Error("web: list recently posted failed", "err", err)
-		views := make([]StoryView, 0, len(rows))
+		http.Error(w, "internal error", http.StatusInternalServerError)
-		for _, r := range rows {
+		return
-			views = append(views, toView(r))
+	}
-		}
+	justPosted := make([]StoryView, 0, len(postedRows))
-		sections = append(sections, indexSection{Channel: ch, Stories: views})
+	for _, r := range postedRows {
+		justPosted = append(justPosted, toView(r))
+	}
+
+	latestRows, err := storage.ListAllClassified(latestLimit, 0)
+	if err != nil {
+		slog.Error("web: list all classified failed", "err", err)
+		http.Error(w, "internal error", http.StatusInternalServerError)
+		return
+	}
+	latest := make([]StoryView, 0, len(latestRows))
+	for _, r := range latestRows {
+		latest = append(latest, toView(r))
+	}
+
+	dayStart := time.Now().Add(-24 * time.Hour).Unix()
+	stats := make([]channelStat, 0, len(channels))
+	for _, ch := range channels {
+		total, _ := storage.CountClassifiedByChannel(ch.Slug)
+		lastTs := storage.GetLastPostTime(ch.Slug)
+		stat := channelStat{
+			Channel:    ch,
+			PostsToday: storage.CountPostsInWindow(ch.Slug, dayStart),
+			Total:      total,
+		}
+		if lastTs > 0 {
+			stat.LastPostedAt = time.Unix(lastTs, 0)
+			stat.HasLastPosted = true
+		}
+		stats = append(stats, stat)
+	}
+
+	data := indexPage{
+		pageData:   s.base(),
+		JustPosted: justPosted,
+		Stats:      stats,
+		Latest:     latest,
 	}
-	data := indexPage{pageData: s.base(), Sections: sections}
 	s.render(w, "index", data)
 }
 
@@ -141,6 +185,15 @@ func (s *Server) render(w http.ResponseWriter, page string, data any) {
 }
 
 var funcs = template.FuncMap{
+	"thumb": thumbURL,
+	"channel": func(slug string) Channel {
+		for _, ch := range channels {
+			if ch.Slug == slug {
+				return ch
+			}
+		}
+		return Channel{Slug: slug, Title: slug, Theme: slug}
+	},
 	"dict": func(pairs ...any) map[string]any {
 		m := make(map[string]any, len(pairs)/2)
 		for i := 0; i+1 < len(pairs); i += 2 {

internal/web/server.go

@@ -34,6 +34,7 @@ var channels = []Channel{
 	{Slug: "gaming", Title: "Gaming", Theme: "gaming", Emoji: "🎮", Blurb: "Releases, platforms, and the people making the games."},
 	{Slug: "tech", Title: "Tech", Theme: "tech", Emoji: "💻", Blurb: "Industry, products, and the wires that hold it all together."},
 	{Slug: "politics", Title: "Politics", Theme: "politics", Emoji: "🏛️", Blurb: "Policy, power, and the news of the day."},
+	{Slug: "music", Title: "Music", Theme: "music", Emoji: "🎵", Blurb: "Records, scenes, and the artists shaping the sound."},
 }
 
 // Server is the HTTP server for Pete's web UI.
@@ -68,6 +69,7 @@ func New(cfg config.WebConfig) (*Server, error) {
 		return nil, err
 	}
 	mux.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.FS(staticSub))))
+	mux.HandleFunc("GET /img/{hash}.avif", s.handleImg)
 
 	mux.HandleFunc("GET /{$}", s.handleIndex)
 	for _, ch := range channels {

internal/web/static/css/input.css

@@ -58,18 +58,33 @@ html[data-phase="night"] {
   .bg-theme-gaming    { background-color: #4caf7d; }
   .bg-theme-tech      { background-color: #5aa9e6; }
   .bg-theme-politics  { background-color: #e07a5f; }
+  .bg-theme-music     { background-color: #b079d6; }
 
   .text-theme-gaming    { color: #2d8a5a; }
   .text-theme-tech      { color: #2f7fb8; }
   .text-theme-politics  { color: #b8523a; }
+  .text-theme-music     { color: #8a4fb8; }
 
   .decoration-theme-gaming    { text-decoration-color: #4caf7d; }
   .decoration-theme-tech      { text-decoration-color: #5aa9e6; }
   .decoration-theme-politics  { text-decoration-color: #e07a5f; }
+  .decoration-theme-music     { text-decoration-color: #b079d6; }
 
   .border-theme-gaming    { border-color: #4caf7d; }
   .border-theme-tech      { border-color: #5aa9e6; }
   .border-theme-politics  { border-color: #e07a5f; }
+  .border-theme-music     { border-color: #b079d6; }
+
+  /* "Posted to Matrix" glow — soft pulsing aura in the channel's theme color. */
+  .glow-theme-gaming   { box-shadow: 0 0 0 2px rgba(76,175,125,0.35), 0 0 24px 4px rgba(76,175,125,0.45); animation: pete-glow-pulse 2.4s ease-in-out infinite; }
+  .glow-theme-tech     { box-shadow: 0 0 0 2px rgba(90,169,230,0.35), 0 0 24px 4px rgba(90,169,230,0.45); animation: pete-glow-pulse 2.4s ease-in-out infinite; }
+  .glow-theme-politics { box-shadow: 0 0 0 2px rgba(224,122,95,0.35), 0 0 24px 4px rgba(224,122,95,0.45); animation: pete-glow-pulse 2.4s ease-in-out infinite; }
+  .glow-theme-music    { box-shadow: 0 0 0 2px rgba(176,121,214,0.35), 0 0 24px 4px rgba(176,121,214,0.45); animation: pete-glow-pulse 2.4s ease-in-out infinite; }
+
+  @keyframes pete-glow-pulse {
+    0%, 100% { filter: brightness(1); }
+    50%      { filter: brightness(1.08); }
+  }
 
   .line-clamp-3 {
     display: -webkit-box;

internal/web/templates/_card.html

@@ -1,17 +1,24 @@
 {{define "card"}}
 <a href="{{.Story.ArticleURL}}" target="_blank" rel="noopener noreferrer"
-   class="group block rounded-3xl bg-[color:var(--card)] border-2 border-[color:var(--ink)]/10 shadow-pete overflow-hidden hover:-translate-y-1 hover:shadow-pete-lg transition">
+   class="group block rounded-3xl bg-[color:var(--card)] border-2 {{if .Story.Posted}}border-theme-{{.Theme}} glow-theme-{{.Theme}}{{else}}border-[color:var(--ink)]/10{{end}} shadow-pete overflow-hidden hover:-translate-y-1 hover:shadow-pete-lg transition">
   {{if .Story.ImageURL}}
   <div class="aspect-[16/10] w-full overflow-hidden bg-[color:var(--ink)]/5">
-    <img src="{{.Story.ImageURL}}" alt="" loading="lazy"
+    <img src="{{thumb .Story.ImageURL}}" alt="" loading="lazy" decoding="async"
          class="h-full w-full object-cover group-hover:scale-105 transition duration-500">
   </div>
   {{end}}
   <div class="p-4 space-y-2">
-    <div class="flex items-center gap-2 text-xs">
+    <div class="flex items-center gap-2 text-xs flex-wrap">
+      {{if .ShowChannel}}{{$ch := channel .Story.Channel}}
+      <span class="inline-flex items-center rounded-full bg-theme-{{$ch.Theme}} text-white px-2.5 py-0.5 font-semibold uppercase tracking-wider">
+        <span aria-hidden="true" class="mr-1">{{$ch.Emoji}}</span>{{$ch.Title}}
+      </span>
+      <span class="text-[color:var(--ink)]/60 font-semibold">{{.Story.Source}}</span>
+      {{else}}
       <span class="inline-flex items-center rounded-full bg-theme-{{.Theme}} text-white px-2.5 py-0.5 font-semibold uppercase tracking-wider">
         {{.Story.Source}}
       </span>
+      {{end}}
       <span class="text-[color:var(--ink)]/50">{{timeAgo .Story.SeenAt}}</span>
     </div>
     <h3 class="font-display text-lg font-semibold leading-snug group-hover:underline underline-offset-2 decoration-theme-{{.Theme}}">

internal/web/templates/index.html

@@ -1,37 +1,81 @@
 {{define "title"}}{{.SiteTitle}} — your news feed{{end}}
 
 {{define "main"}}
-<section class="mt-2 mb-10 sm:mb-14 text-center">
+<section class="mt-2 mb-8 text-center">
   <h1 class="font-display text-4xl sm:text-6xl font-bold leading-tight">
     a friendlier news feed.
   </h1>
   <p class="mx-auto mt-3 max-w-xl text-base sm:text-lg text-[color:var(--ink)]/70">
     Pete reads RSS, sorts stories, and posts them to Matrix.
-    Here's what he's been reading lately.
+    Glowing cards are the ones he's posted.
   </p>
 </section>
 
-{{range .Sections}}
+{{if .JustPosted}}
+<section class="mb-10">
+  <div class="flex items-end justify-between gap-3 mb-4">
+    <h2 class="font-display text-xl sm:text-2xl font-bold">
+      <span aria-hidden="true">📡</span> Pete just posted
+    </h2>
+    <span class="text-xs text-[color:var(--ink)]/50">most recent posts to Matrix</span>
+  </div>
+  <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-3 gap-4">
+    {{range .JustPosted}}
+      {{template "card" dict "Story" . "Theme" .Channel "ShowChannel" true}}
+    {{end}}
+  </div>
+</section>
+{{end}}
+
+<section class="mb-10">
+  <div class="flex items-end justify-between gap-3 mb-4">
+    <h2 class="font-display text-xl sm:text-2xl font-bold">
+      <span aria-hidden="true">📊</span> Channels
+    </h2>
+    <span class="text-xs text-[color:var(--ink)]/50">last 24 hours</span>
+  </div>
+  <div class="grid grid-cols-2 lg:grid-cols-4 gap-3 sm:gap-4">
+    {{range .Stats}}
+    <a href="/{{.Channel.Slug}}"
+       class="block rounded-3xl bg-[color:var(--card)] border-2 border-[color:var(--ink)]/10 shadow-pete p-4 hover:-translate-y-1 hover:shadow-pete-lg transition">
+      <div class="flex items-center gap-2">
+        <span class="inline-flex items-center justify-center h-9 w-9 rounded-2xl bg-theme-{{.Channel.Theme}} text-white text-lg">
+          {{.Channel.Emoji}}
+        </span>
+        <span class="font-display text-lg font-semibold">{{.Channel.Title}}</span>
+      </div>
+      <dl class="mt-3 space-y-1 text-xs text-[color:var(--ink)]/70">
+        <div class="flex justify-between gap-2">
+          <dt>last post</dt>
+          <dd class="font-semibold text-[color:var(--ink)]">
+            {{if .HasLastPosted}}{{timeAgo .LastPostedAt}}{{else}}—{{end}}
+          </dd>
+        </div>
+        <div class="flex justify-between gap-2">
+          <dt>posted 24h</dt>
+          <dd class="font-semibold text-[color:var(--ink)]">{{.PostsToday}}</dd>
+        </div>
+        <div class="flex justify-between gap-2">
+          <dt>stories</dt>
+          <dd class="font-semibold text-[color:var(--ink)]">{{.Total}}</dd>
+        </div>
+      </dl>
+    </a>
+    {{end}}
+  </div>
+</section>
+
 <section class="mb-12">
   <div class="flex items-end justify-between gap-3 mb-4">
-    <div>
+    <h2 class="font-display text-xl sm:text-2xl font-bold">
-      <h2 class="font-display text-2xl sm:text-3xl font-bold">
+      <span aria-hidden="true">🗞️</span> Latest across the feed
-        <span aria-hidden="true">{{.Channel.Emoji}}</span>
+    </h2>
-        <a href="/{{.Channel.Slug}}" class="hover:underline underline-offset-4 decoration-theme-{{.Channel.Theme}} decoration-4">
+    <span class="text-xs text-[color:var(--ink)]/50">newest first, all channels</span>
-          {{.Channel.Title}}
-        </a>
-      </h2>
-      <p class="text-sm text-[color:var(--ink)]/60 mt-1">{{.Channel.Blurb}}</p>
-    </div>
-    <a href="/{{.Channel.Slug}}" class="hidden sm:inline-flex items-center gap-1 text-sm font-semibold rounded-full bg-theme-{{.Channel.Theme}} text-white px-4 py-2 shadow-pete hover:-translate-y-0.5 transition">
-      more →
-    </a>
   </div>
-
+  {{if .Latest}}
-  {{if .Stories}}
   <div class="grid grid-cols-1 sm:grid-cols-2 lg:grid-cols-4 gap-4">
-    {{range .Stories}}
+    {{range .Latest}}
-      {{template "card" dict "Story" . "Theme" $.Channel.Theme}}
+      {{template "card" dict "Story" . "Theme" .Channel "ShowChannel" true}}
     {{end}}
   </div>
   {{else}}
@@ -41,4 +85,3 @@
   {{end}}
 </section>
 {{end}}
-{{end}}

internal/web/thumbs.go

@@ -0,0 +1,199 @@
+package web
+
+import (
+	"bytes"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"image"
+	_ "image/gif"
+	_ "image/jpeg"
+	"image/png"
+	"io"
+	"log/slog"
+	"net/http"
+	"net/url"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"sync"
+	"time"
+
+	"golang.org/x/image/draw"
+	_ "golang.org/x/image/webp"
+
+	"pete/internal/storage"
+)
+
+const (
+	thumbWidth        = 800
+	thumbMaxBytes     = 12 << 20 // 12 MiB cap on source download
+	thumbFetchTimeout = 12 * time.Second
+	thumbCacheDir     = "./data/img-cache"
+	thumbQuality      = "45"
+	thumbSpeed        = "8"
+)
+
+var (
+	thumbClient = &http.Client{Timeout: thumbFetchTimeout}
+
+	thumbMu       sync.Mutex
+	thumbInFlight = map[string]*sync.WaitGroup{}
+)
+
+func thumbKey(u string) string {
+	sum := sha256.Sum256([]byte(u))
+	return hex.EncodeToString(sum[:16])
+}
+
+// thumbURL maps a source image URL to the /img proxy path. Empty input → "".
+func thumbURL(src string) string {
+	if src == "" {
+		return ""
+	}
+	return "/img/" + thumbKey(src) + ".avif?u=" + url.QueryEscape(src)
+}
+
+func (s *Server) handleImg(w http.ResponseWriter, r *http.Request) {
+	hash := r.PathValue("hash")
+	src := r.URL.Query().Get("u")
+	if src == "" || thumbKey(src) != hash {
+		http.NotFound(w, r)
+		return
+	}
+	if !(strings.HasPrefix(src, "http://") || strings.HasPrefix(src, "https://")) {
+		http.NotFound(w, r)
+		return
+	}
+	if !storage.IsKnownImageURL(src) {
+		http.NotFound(w, r)
+		return
+	}
+
+	if err := os.MkdirAll(thumbCacheDir, 0o755); err != nil {
+		http.Error(w, "cache dir", http.StatusInternalServerError)
+		return
+	}
+	cachePath := filepath.Join(thumbCacheDir, hash+".avif")
+	if fi, err := os.Stat(cachePath); err == nil && fi.Size() > 0 {
+		serveAvif(w, r, cachePath)
+		return
+	}
+
+	// Single-flight: collapse concurrent requests for the same image.
+	thumbMu.Lock()
+	wg, busy := thumbInFlight[hash]
+	if !busy {
+		wg = &sync.WaitGroup{}
+		wg.Add(1)
+		thumbInFlight[hash] = wg
+	}
+	thumbMu.Unlock()
+
+	if busy {
+		wg.Wait()
+		if fi, err := os.Stat(cachePath); err == nil && fi.Size() > 0 {
+			serveAvif(w, r, cachePath)
+			return
+		}
+		http.Redirect(w, r, src, http.StatusFound)
+		return
+	}
+	defer func() {
+		thumbMu.Lock()
+		delete(thumbInFlight, hash)
+		thumbMu.Unlock()
+		wg.Done()
+	}()
+
+	if err := buildAvifThumb(src, cachePath); err != nil {
+		slog.Warn("thumb build failed", "url", src, "err", err)
+		http.Redirect(w, r, src, http.StatusFound)
+		return
+	}
+	serveAvif(w, r, cachePath)
+}
+
+func serveAvif(w http.ResponseWriter, r *http.Request, path string) {
+	w.Header().Set("Content-Type", "image/avif")
+	w.Header().Set("Cache-Control", "public, max-age=2592000, immutable")
+	http.ServeFile(w, r, path)
+}
+
+// buildAvifThumb downloads src, decodes + resizes in Go, then shells out to
+// avifenc to produce a compact AVIF at outPath.
+func buildAvifThumb(src, outPath string) error {
+	req, err := http.NewRequest(http.MethodGet, src, nil)
+	if err != nil {
+		return err
+	}
+	req.Header.Set("User-Agent", "Pete-Thumb/1.0 (+https://pete.example)")
+	resp, err := thumbClient.Do(req)
+	if err != nil {
+		return err
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != http.StatusOK {
+		return fmt.Errorf("upstream %d", resp.StatusCode)
+	}
+	body, err := io.ReadAll(io.LimitReader(resp.Body, thumbMaxBytes+1))
+	if err != nil {
+		return err
+	}
+	if len(body) > thumbMaxBytes {
+		return fmt.Errorf("image too big (>%d bytes)", thumbMaxBytes)
+	}
+
+	src2, _, err := image.Decode(bytes.NewReader(body))
+	if err != nil {
+		return fmt.Errorf("decode: %w", err)
+	}
+	b := src2.Bounds()
+	srcW, srcH := b.Dx(), b.Dy()
+	if srcW <= 0 || srcH <= 0 {
+		return fmt.Errorf("empty image")
+	}
+	dstW, dstH := srcW, srcH
+	if srcW > thumbWidth {
+		dstW = thumbWidth
+		dstH = int(float64(srcH) * float64(thumbWidth) / float64(srcW))
+		if dstH < 1 {
+			dstH = 1
+		}
+	}
+	var resized image.Image = src2
+	if dstW != srcW || dstH != srcH {
+		dst := image.NewRGBA(image.Rect(0, 0, dstW, dstH))
+		draw.CatmullRom.Scale(dst, dst.Bounds(), src2, b, draw.Over, nil)
+		resized = dst
+	}
+
+	tmp, err := os.CreateTemp("", "pete-thumb-*.png")
+	if err != nil {
+		return err
+	}
+	tmpPath := tmp.Name()
+	defer os.Remove(tmpPath)
+	if err := png.Encode(tmp, resized); err != nil {
+		tmp.Close()
+		return err
+	}
+	if err := tmp.Close(); err != nil {
+		return err
+	}
+
+	// Encode to a sibling temp file then atomically rename so partial outputs
+	// never appear in the cache.
+	stagedOut := outPath + ".tmp"
+	cmd := exec.Command("avifenc",
+		"-q", thumbQuality,
+		"-s", thumbSpeed,
+		tmpPath, stagedOut,
+	)
+	if out, err := cmd.CombinedOutput(); err != nil {
+		os.Remove(stagedOut)
+		return fmt.Errorf("avifenc: %w: %s", err, strings.TrimSpace(string(out)))
+	}
+	return os.Rename(stagedOut, outPath)
+}