diff --git a/CLAUDE.md b/CLAUDE.md
index be0f117..0ddb169 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -42,10 +42,19 @@ JSON shapes mirror the Tauri Rust bridge exactly — don't change one side alone
   (15 min · 2^n, max 24 h) and saves fall back to the legacy per-request path.
 - `gen` is in the filename and URL (`/api/media/<id>?g=<gen>`): a URL never serves
   different bytes. A replaced gen is kept 30 min so in-flight Range playback survives.
-- **Compression lane**: niced x264 `-preset slow -crf 28 -fpsmax 30`, audio copied,
-  kept only if ≥15% smaller. Measured: YouTube's 720p avc1 is already ~0.6–0.7 Mbps, so
-  CRF 24 made files *bigger*; CRF 28 ≈ −20% video at SSIM 0.994. Lyric videos usually
-  keep the original. HEVC/AV1/10-bit are smaller but don't play in iOS `<video>`.
+- **Compression lane** (rev `OPT_REV` = 2): niced x265 8-bit `-preset medium -crf 28`,
+  `hvc1` tag, anime-style tuning (`X265_TUNING`), `-fpsmax 30`, audio copied — kept only
+  if ≥15% smaller, and the copy's `vcodec` becomes `hevc`. Benchmarked 2026-09-13 (VMAF,
+  codec-test page in Windows Docs): x264 can NOT beat YouTube's own H.264 (needs more
+  bitrate at equal quality); x265 cuts live worship video ~35–44% at ~2× realtime on the
+  homelab's 2 threads; lyric videos (~47 kbps video, mostly audio) keep the original.
+  Bumping `OPT_REV` re-queues every cached copy once at boot.
+- **HEVC gating**: an HEVC copy is served only to clients that send `?hevc=1` on
+  `/api/streams` and `/api/download` (app.js `hevcCapable()` = canPlayType hvc1, minus a
+  per-device `ytpNoHevc` flag set when an HEVC copy fails to play). Everyone else gets
+  the pre-cache behaviour (YouTube proxy / legacy H.264 save). Verified: iPhone XR, Galaxy
+  S10, Windows Chrome play HEVC; AV1 fails on the XR (no decoder), so it isn't used.
+  The validation gate requires `hvc1` (Safari refuses `hev1`) and 8-bit 4:2:0.
 - **Budget**: `MEDIA_CACHE_MAX_BYTES` (10 GiB) LRU by `last_access` (anything played in
   the last 10 min is protected) + `MEDIA_MIN_FREE_BYTES` (5 GiB) disk guard → skip, stream.
 - **Broken**: `POST /api/media/:id/redownload` (now-playing ⚠ Broken button). When a
diff --git a/docker-compose.yml b/docker-compose.yml
index 5bd3cb7..6c7144f 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -16,10 +16,12 @@ services:
       # MEDIA_CACHE_MAX_BYTES: "10737418240"          # 10 GiB, LRU eviction past this
       # MEDIA_MIN_FREE_BYTES: "5368709120"            # skip caching below 5 GiB free disk
       # MEDIA_AUTO_MAX_SECONDS: "3600"                # longest video auto-cached on play
-      # MEDIA_TRANSCODE: "1"                          # 0 disables the x264 lane
+      # MEDIA_TRANSCODE: "1"                          # 0 disables the compression lane
+      # MEDIA_CODEC: "hevc"                           # hevc | h264
       # MEDIA_CRF: "28"
-      # MEDIA_PRESET: "slow"
+      # MEDIA_PRESET: "medium"
       # MEDIA_THREADS: "2"
+      # MEDIA_OPT_MAX_SECONDS: "3600"                 # don't re-encode videos longer than this
     healthcheck:
       test: ["CMD", "curl", "-sf", "http://localhost:3000/api/version"]
       interval: 30s
diff --git a/frontend/app.js b/frontend/app.js
index 53c911d..6a09f14 100755
--- a/frontend/app.js
+++ b/frontend/app.js
@@ -68,6 +68,19 @@ function saveDataToStorage(jsonStr) {
   } catch { /* ignore parse errors */ }
 }
 
+// Can this device decode the server's HEVC copies? The compression lane
+// re-encodes cached videos to HEVC (8-bit, hvc1) when that is much smaller;
+// the server hands those out only to clients that send hevc=1. canPlayType
+// is the browser's own claim; if a copy still fails to play here, the device
+// is remembered (NO_HEVC_KEY) and stops asking — it gets H.264 as before.
+const NO_HEVC_KEY = 'ytpNoHevc';
+function hevcCapable() {
+  try { if (localStorage.getItem(NO_HEVC_KEY) === '1') return false; } catch { /* storage blocked */ }
+  try {
+    return document.createElement('video').canPlayType('video/mp4; codecs="hvc1.1.6.L93.B0"') !== '';
+  } catch { return false; }
+}
+
 // OPFS bridge wrappers — return the same shape as the Tauri cache_* commands
 // so the rest of app.js works without changes.
 
@@ -82,6 +95,7 @@ async function opfsDownload(videoId, { mux = false } = {}) {
   // (used by "Save before playing"); default saves keep the progressive
   // stream exactly as before.
   if (mux) params.set('mux', '1');
+  if (hevcCapable()) params.set('hevc', '1');
   const qs = params.toString();
   const url = `/api/download/${encodeURIComponent(videoId)}${qs ? '?' + qs : ''}`;
 
@@ -199,7 +213,7 @@ const API = {
   // nocache=1 skips the server's cached copy and resolves fresh YouTube
   // streams (used when the cached copy won't play on this device).
   getStreams: (videoId, { nocache = false } = {}) => WEB
-    ? webFetch(`/api/streams?v=${encodeURIComponent(videoId)}${nocache ? '&nocache=1' : ''}`)
+    ? webFetch(`/api/streams?v=${encodeURIComponent(videoId)}${nocache ? '&nocache=1' : ''}${!nocache && hevcCapable() ? '&hevc=1' : ''}`)
     : call('yt.streams', 'yt_streams', { videoId }),
   loadData: () => WEB
     ? Promise.resolve(loadDataFromStorage())
@@ -1581,6 +1595,11 @@ const Player = {
     // device, so the ⚠ Broken button is how a user flags a bad server copy.
     if (current && current.serverCached) {
       const meta = current.meta;
+      // An HEVC copy that won't play means canPlayType over-promised on this
+      // device: stop asking for HEVC here (the server re-checks its copy).
+      if ((current.qualities || []).some((q) => q.codec === 'hevc')) {
+        try { localStorage.setItem(NO_HEVC_KEY, '1'); } catch { /* storage blocked */ }
+      }
       current.serverCached = false;
       toast('Server copy failed — streaming from YouTube. Tap ⚠ Broken to re-download it.', { duration: 5000 });
       this.loadVideo(meta, { preferStream: true, nocache: true, resume: this._resumeOnLoad, reveal: this._revealOnLoad });
diff --git a/server/db.js b/server/db.js
index 8fde576..809c8f1 100644
--- a/server/db.js
+++ b/server/db.js
@@ -176,13 +176,14 @@ export async function mediaStats() {
        SUM(CASE WHEN status = 'ready' THEN size ELSE 0 END) AS bytes,
        SUM(CASE WHEN status IN ('queued','downloading','validating') THEN 1 ELSE 0 END) AS pending,
        SUM(CASE WHEN status = 'failed' THEN 1 ELSE 0 END)   AS failed,
-       SUM(CASE WHEN status = 'ready' AND optimized = 1 THEN 1 ELSE 0 END) AS optimized
+       SUM(CASE WHEN status = 'ready' AND optimized > 0 THEN 1 ELSE 0 END) AS optimized,
+       SUM(CASE WHEN status = 'ready' AND vcodec = 'hevc' THEN 1 ELSE 0 END) AS hevc
      FROM media_cache`,
   );
   const o = r.rows[0] ? rowToObj(r, r.rows[0]) : {};
   return {
     count: o.count || 0, bytes: o.bytes || 0, pending: o.pending || 0,
-    failed: o.failed || 0, optimized: o.optimized || 0,
+    failed: o.failed || 0, optimized: o.optimized || 0, hevc: o.hevc || 0,
   };
 }
 
diff --git a/server/media-cache.js b/server/media-cache.js
index 00b8cc8..4583de8 100644
--- a/server/media-cache.js
+++ b/server/media-cache.js
@@ -28,6 +28,11 @@ import { join } from 'node:path';
 export const HIGH = 0; // explicit save / Broken re-download
 export const LOW  = 1; // auto-cache after a play
 
+// Compression-lane revision. `optimized` stores the revision a copy was last
+// evaluated with; bumping this re-queues every cached copy once (rev 1 was
+// x264, which never beat YouTube's own encode; rev 2 is HEVC).
+export const OPT_REV = 2;
+
 const ID_RE = /^[A-Za-z0-9_-]{6,64}$/;
 export const isMediaId = (id) => typeof id === 'string' && ID_RE.test(id);
 
@@ -36,7 +41,11 @@ const OLD_GEN_GRACE_MS  = 30 * 60_000;   // keep superseded files for in-flight
 const EVICT_PROTECT_MS  = 10 * 60_000;   // never evict something played this recently
 const TOUCH_DEBOUNCE_MS = 60_000;
 const EST_BYTES_PER_SEC = 250 * 1024;    // ~2 Mbps: pre-compression 720p + 128k AAC
-const MIN_SAVING        = 0.15;          // keep an x264 re-encode only if ≥15% smaller
+const MIN_SAVING        = 0.15;          // keep a re-encode only if ≥15% smaller
+// x265 tuning from the codec benchmark: stronger adaptive quantisation and
+// psy settings, no SAO blur, lighter deblock, longer lookahead.
+const X265_TUNING = 'aq-mode=3:aq-strength=0.8:psy-rd=1.5:psy-rdoq=1.0:no-sao=1:deblock=-1,-1:'
+  + 'bframes=8:rc-lookahead=60:ref=6:no-strong-intra-smoothing=1';
 const DAY_MS            = 24 * 3600_000;
 
 // A condition that means "don't cache this right now, just stream it" — not a
@@ -69,20 +78,22 @@ function run(cmd, args) {
 // ----------------------------------------------------------------------------
 // Validation gate. Throws with a reason; resolves to probe facts on success.
 //   1. file exists and is not tiny
-//   2. exactly one H.264 8-bit 4:2:0 video stream + an AAC audio stream
-//      (AV1/VP9/10-bit play on almost nothing Apple — see SAVE_MUX_FORMAT)
+//   2. exactly one 8-bit 4:2:0 video stream in an allowed codec + an AAC
+//      audio stream. Downloads must be H.264 (AV1/VP9 play on almost nothing
+//      Apple — see SAVE_MUX_FORMAT); the compression lane may produce HEVC,
+//      which must carry the `hvc1` tag or Safari refuses it.
 //   3. container AND per-stream durations cover the expected length
 //   4. full demux pass reports no errors (catches corrupt/truncated boxes)
 //   5. the first and last seconds actually decode
 // ----------------------------------------------------------------------------
-export async function validateMedia(path, expected, { ffmpeg = 'ffmpeg', ffprobe = 'ffprobe' } = {}) {
+export async function validateMedia(path, expected, { ffmpeg = 'ffmpeg', ffprobe = 'ffprobe', codecs = ['h264', 'hevc'] } = {}) {
   const size = sizeOf(path);
   if (!size) throw new Error('validation: output file missing');
   if (size < MIN_BYTES) throw new Error(`validation: file too small (${size} bytes)`);
 
   const pr = await run(ffprobe, [
     '-v', 'error',
-    '-show_entries', 'format=duration:stream=codec_type,codec_name,height,pix_fmt,duration:stream_disposition=attached_pic',
+    '-show_entries', 'format=duration:stream=codec_type,codec_name,codec_tag_string,height,pix_fmt,duration:stream_disposition=attached_pic',
     '-of', 'json', path,
   ]);
   if (pr.code !== 0) throw new Error('validation: ffprobe failed: ' + tail(pr.stderr));
@@ -93,7 +104,10 @@ export async function validateMedia(path, expected, { ffmpeg = 'ffmpeg', ffprobe
   const audio = streams.filter((s) => s.codec_type === 'audio');
   if (video.length !== 1) throw new Error(`validation: expected 1 video stream, found ${video.length}`);
   const v = video[0];
-  if (v.codec_name !== 'h264') throw new Error(`validation: video codec ${v.codec_name} is not h264`);
+  if (!codecs.includes(v.codec_name)) throw new Error(`validation: video codec ${v.codec_name} is not ${codecs.join('/')}`);
+  if (v.codec_name === 'hevc' && v.codec_tag_string !== 'hvc1') {
+    throw new Error(`validation: HEVC tagged ${v.codec_tag_string} (Safari needs hvc1)`);
+  }
   if (v.pix_fmt && !/^yuvj?420p$/.test(v.pix_fmt)) throw new Error(`validation: pixel format ${v.pix_fmt} is not 8-bit 4:2:0`);
   const a = audio.find((s) => s.codec_name === 'aac');
   if (!a) throw new Error('validation: no AAC audio stream');
@@ -147,7 +161,7 @@ export function createMediaCache({
   minFreeBytes = 5 * 1024 ** 3,
   autoMaxSeconds = 3600,
   saveMaxSeconds = 3 * 3600,
-  transcode = { enabled: true, crf: 28, preset: 'slow', threads: 2 },
+  transcode = { enabled: true, codec: 'hevc', crf: 28, preset: 'medium', threads: 2, maxSeconds: 3600 },
   freeBytes = () => { const s = statfsSync(dir); return s.bavail * s.bsize; },
   now = () => Date.now(),
   log = console,
@@ -285,7 +299,7 @@ export function createMediaCache({
       const rm = await run(ffmpeg, ['-v', 'error', '-nostdin', '-y', '-i', raw,
         '-map', '0:v:0', '-map', '0:a:0', '-c', 'copy', '-movflags', '+faststart', '-f', 'mp4', norm]);
       if (rm.code !== 0) throw new Error('remux failed: ' + tail(rm.stderr));
-      const probe = await validateMedia(norm, expected, { ffmpeg, ffprobe });
+      const probe = await validateMedia(norm, expected, { ffmpeg, ffprobe, codecs: ['h264'] });
 
       const m4a = `${base}.norm.m4a`;
       const ex = await run(ffmpeg, ['-v', 'error', '-nostdin', '-y', '-i', norm,
@@ -332,11 +346,15 @@ export function createMediaCache({
   }
 
   // ---- Compression lane ----------------------------------------------------
-  // CRF (quality-targeted, not a fixed bitrate) at a slow preset is where
-  // small files come from — static lyric/slide videos collapse to a fraction
-  // of YouTube's bitrate. 60 fps is capped to 30. Audio is copied untouched.
-  // Output stays 8-bit H.264: 10-bit / HEVC / AV1 are smaller but do not
-  // play in iOS Safari's <video>.
+  // Re-encodes a ready copy with CRF (quality-targeted) and keeps the result
+  // only when it is ≥15% smaller. Measured 2026-09-13: x264 can't beat
+  // YouTube's own H.264 (it needed MORE bitrate for the same VMAF), while
+  // x265 8-bit medium CRF 28 cut live worship video ~44% (VMAF ~93) at ~2x
+  // realtime on the homelab's 2 niced threads. HEVC plays on iPhone Safari,
+  // Android and Chrome/Edge with hardware decode; the server only serves an
+  // HEVC copy to clients that ask for it (?hevc=1), everyone else streams.
+  // 8-bit on purpose — the widest hardware-decode support. 60 fps is capped
+  // to 30; audio is copied untouched.
   function enqueueOptimize(id) {
     if (!transcode || !transcode.enabled || optPending.has(id)) return;
     optPending.add(id);
@@ -355,33 +373,41 @@ export function createMediaCache({
 
   async function runOptimize(id) {
     const row = await db.getMedia(id);
-    if (!row || row.status !== 'ready' || row.optimized) return;
+    if (!row || row.status !== 'ready' || (row.optimized || 0) >= OPT_REV) return;
     const src = fileFor(id, row.gen);
     if (!existsSync(src)) return;
-    const prefix = `${id}-${now()}-x264`;
-    const out = join(tmpDir, `${prefix}.mp4`);
     const markDone = async () => {
       const cur = await db.getMedia(id);
-      if (cur && cur.status === 'ready' && cur.gen === row.gen) await db.upsertMedia(id, { optimized: 1 });
+      if (cur && cur.status === 'ready' && cur.gen === row.gen) await db.upsertMedia(id, { optimized: OPT_REV });
     };
+    // Very long videos would tie the lane up for hours on 2 niced threads.
+    if (transcode.maxSeconds && row.duration > transcode.maxSeconds) { await markDone(); return; }
+    const hevc = transcode.codec !== 'h264';
+    const prefix = `${id}-${now()}-${hevc ? 'x265' : 'x264'}`;
+    const out = join(tmpDir, `${prefix}.mp4`);
     try {
+      const threads = String(transcode.threads);
+      const video = hevc
+        ? ['-c:v', 'libx265', '-preset', String(transcode.preset), '-crf', String(transcode.crf),
+           '-pix_fmt', 'yuv420p', '-tag:v', 'hvc1',
+           '-x265-params', `log-level=error:pools=${threads}:${X265_TUNING}`]
+        : ['-c:v', 'libx264', '-preset', String(transcode.preset), '-crf', String(transcode.crf),
+           '-profile:v', 'high', '-level:v', '4.0', '-pix_fmt', 'yuv420p', '-threads', threads];
       const args = ['-v', 'error', '-nostdin', '-y', '-i', src,
         '-map', '0:v:0', '-map', '0:a:0',
         '-vf', 'scale=-2:min(720\\,ih)',
-        '-c:v', 'libx264', '-preset', String(transcode.preset), '-crf', String(transcode.crf),
-        '-profile:v', 'high', '-level:v', '4.0', '-pix_fmt', 'yuv420p',
-        '-threads', String(transcode.threads), '-fpsmax', '30',
+        ...video, '-fpsmax', '30',
         '-c:a', 'copy', '-movflags', '+faststart', '-f', 'mp4', out];
       const r = nice ? await run(nice, ['-n', '19', ffmpeg, ...args]) : await run(ffmpeg, args);
-      if (r.code !== 0) throw new Error('x264 encode failed: ' + tail(r.stderr));
-      const probe = await validateMedia(out, row.duration, { ffmpeg, ffprobe });
+      if (r.code !== 0) throw new Error(`${hevc ? 'x265' : 'x264'} encode failed: ` + tail(r.stderr));
+      const probe = await validateMedia(out, row.duration, { ffmpeg, ffprobe, codecs: [hevc ? 'hevc' : 'h264'] });
 
       const cur = await db.getMedia(id);
       if (!cur || cur.status !== 'ready' || cur.gen !== row.gen) return; // replaced or evicted meanwhile
       const oldSize = sizeOf(src);
       if (probe.size > oldSize * (1 - MIN_SAVING)) {
-        await db.upsertMedia(id, { optimized: 1 });
-        log.info?.(`[media] kept original ${id}: x264 ${fmtMB(probe.size)} vs ${fmtMB(oldSize)}`);
+        await db.upsertMedia(id, { optimized: OPT_REV });
+        log.info?.(`[media] kept original ${id}: ${probe.vcodec} ${fmtMB(probe.size)} vs ${fmtMB(oldSize)}`);
         return;
       }
       const gen = row.gen + 1;
@@ -390,13 +416,13 @@ export function createMediaCache({
       const newAudio = fileFor(id, gen, 'm4a');
       try { linkSync(oldAudio, newAudio); } catch { copyFileSync(oldAudio, newAudio); }
       await db.upsertMedia(id, {
-        gen, size: probe.size + sizeOf(newAudio), height: probe.height,
-        duration: probe.duration, optimized: 1, updated_at: now(),
+        gen, size: probe.size + sizeOf(newAudio), height: probe.height, vcodec: probe.vcodec,
+        duration: probe.duration, optimized: OPT_REV, updated_at: now(),
       });
       removeFiles(id, gen, OLD_GEN_GRACE_MS);
-      log.info?.(`[media] optimized ${id}: ${fmtMB(oldSize)} → ${fmtMB(probe.size)}`);
+      log.info?.(`[media] optimized ${id}: ${fmtMB(oldSize)} → ${fmtMB(probe.size)} (${probe.vcodec})`);
     } catch (err) {
-      await markDone().catch(() => {}); // don't retry a source x264 can't improve
+      await markDone().catch(() => {}); // don't retry a source the encoder can't improve
       throw err;
     } finally {
       sweepTmp(prefix);
@@ -505,7 +531,8 @@ export function createMediaCache({
       status:     job ? job.status : row ? row.status : 'none',
       size:       row ? row.size : 0,
       height:     row ? row.height : 0,
-      optimized:  !!(row && row.optimized),
+      vcodec:     row ? row.vcodec : null,
+      optimized:  !!(row && (row.optimized || 0) >= OPT_REV),
       optimizing: optActive === id,
       error:      row && row.status === 'failed' ? row.error : null,
       retryAt:    row && row.status === 'failed' ? row.retry_at : 0,
@@ -542,7 +569,7 @@ export function createMediaCache({
     for (const r of rows) {
       if (r.status === 'ready') {
         if (!readyFilesExist(r)) { await db.deleteMedia(r.video_id); removeFiles(r.video_id); continue; }
-        if (!r.optimized) enqueueOptimize(r.video_id);
+        if ((r.optimized || 0) < OPT_REV) enqueueOptimize(r.video_id);
       } else if (r.status === 'queued' || r.status === 'downloading' || r.status === 'validating') {
         startJob(r.video_id, r.priority === HIGH ? HIGH : LOW, !!r.auto, r);
         resumed++;
diff --git a/server/media-cache.test.js b/server/media-cache.test.js
index 68db7f3..998e5fa 100644
--- a/server/media-cache.test.js
+++ b/server/media-cache.test.js
@@ -9,7 +9,7 @@ import { join } from 'node:path';
 const root = mkdtempSync(join(tmpdir(), 'ytp-media-test-'));
 process.env.DB_PATH = join(root, 'test.db');
 const dbmod = await import('./db.js');
-const { createMediaCache, validateMedia, MediaSkip, HIGH, LOW } = await import('./media-cache.js');
+const { createMediaCache, validateMedia, MediaSkip, HIGH, LOW, OPT_REV } = await import('./media-cache.js');
 
 const fx = (name) => join(root, name);
 const ff = (...args) => {
@@ -33,6 +33,11 @@ beforeAll(async () => {
      '-c:v', 'libx264', '-preset', 'ultrafast', '-pix_fmt', 'yuv420p', fx('noaudio.mp4'));
   ff('-f', 'lavfi', '-i', 'testsrc=size=640x360:rate=30:duration=10', '-f', 'lavfi', '-i', 'sine=frequency=440:duration=10',
      '-c:v', 'mpeg4', '-c:a', 'aac', '-shortest', fx('mpeg4.mp4'));
+  // HEVC as the compression lane writes it (hvc1) and as Safari rejects it (hev1).
+  ff('-f', 'lavfi', '-i', 'testsrc=size=640x360:rate=30:duration=10', '-f', 'lavfi', '-i', 'sine=frequency=440:duration=10',
+     '-c:v', 'libx265', '-preset', 'ultrafast', '-pix_fmt', 'yuv420p', '-tag:v', 'hvc1', '-x265-params', 'log-level=error',
+     '-c:a', 'aac', '-shortest', fx('hevc.mp4'));
+  ff('-i', fx('hevc.mp4'), '-c', 'copy', '-tag:v', 'hev1', fx('hevc-hev1.mp4'));
   const buf = readFileSync(fx('good.mp4'));
   writeFileSync(fx('truncated.mp4'), buf.subarray(0, Math.floor(buf.length * 0.6)));
   // The nasty case: moov up front (index says 10 s) but the media data is cut.
@@ -61,6 +66,14 @@ describe('validateMedia', () => {
   test('rejects a non-h264 file', async () => {
     await expect(validateMedia(fx('mpeg4.mp4'), 10)).rejects.toThrow(/not h264/);
   });
+  test('accepts hvc1-tagged HEVC for the compression lane, but not as a download', async () => {
+    const p = await validateMedia(fx('hevc.mp4'), 10);
+    expect(p.vcodec).toBe('hevc');
+    await expect(validateMedia(fx('hevc.mp4'), 10, { codecs: ['h264'] })).rejects.toThrow(/not h264/);
+  });
+  test('rejects hev1-tagged HEVC (Safari refuses it)', async () => {
+    await expect(validateMedia(fx('hevc-hev1.mp4'), 10)).rejects.toThrow(/hvc1/);
+  });
   test('rejects a file shorter than the source video', async () => {
     await expect(validateMedia(fx('good.mp4'), 60)).rejects.toThrow(/truncated/);
   });
@@ -210,19 +223,39 @@ describe('media cache jobs', () => {
     expect(calls).toEqual(['bootAAAAAA1']);
   });
 
-  test('x264 compression lane swaps in a smaller copy under a new gen', async () => {
+  test('HEVC compression lane swaps in a smaller copy under a new gen', async () => {
     await clearDb();
-    const { cache } = makeCache({ transcode: { enabled: true, crf: 35, preset: 'ultrafast', threads: 2 } });
+    const { cache } = makeCache({ transcode: { enabled: true, codec: 'hevc', crf: 34, preset: 'ultrafast', threads: 2 } });
     await cache.init();
     const first = await cache.ensureCached('optAAAAAAA1', { priority: HIGH });
-    expect(await until(async () => (await dbmod.getMedia('optAAAAAAA1')).optimized === 1)).toBe(true);
+    expect(first.vcodec).toBe('h264');
+    expect(await until(async () => (await dbmod.getMedia('optAAAAAAA1')).optimized === OPT_REV)).toBe(true);
     const after = await dbmod.getMedia('optAAAAAAA1');
-    if (after.gen !== first.gen) {
-      expect(after.size).toBeLessThan(first.size);
-      // old generation is kept for in-flight playback (grace period)
-      expect(await cache.filePath('optAAAAAAA1', first.gen)).not.toBeNull();
-    }
+    expect(after.gen).toBeGreaterThan(first.gen);
+    expect(after.vcodec).toBe('hevc');
+    expect(after.size).toBeLessThan(first.size);
+    // old generation is kept for in-flight playback (grace period)
+    expect(await cache.filePath('optAAAAAAA1', first.gen)).not.toBeNull();
     expect(await cache.filePath('optAAAAAAA1', after.gen, 'm4a')).not.toBeNull();
+    // and the HEVC copy still passes the gate verify() uses
+    expect(await cache.verify('optAAAAAAA1')).toBe(true);
+  });
+
+  test('copies evaluated by an older lane revision are re-queued at boot', async () => {
+    await clearDb();
+    const seed = makeCache();
+    await seed.cache.init();
+    await seed.cache.ensureCached('revAAAAAAA1', { priority: HIGH });
+    await dbmod.upsertMedia('revAAAAAAA1', { optimized: 1 }); // the old x264 revision
+    // A fresh instance over the same dir + DB, as after a deploy.
+    const same = createMediaCache({
+      dir: seed.dir, db: { getMedia: dbmod.getMedia, upsertMedia: dbmod.upsertMedia, deleteMedia: dbmod.deleteMedia,
+        listMedia: dbmod.listMedia, listMediaLru: dbmod.listMediaLru, touchMedia: dbmod.touchMedia, mediaStats: dbmod.mediaStats },
+      log: silentLog, getInfo: async () => ({ duration: 10 }), download: async () => { throw new Error('no download expected'); },
+      transcode: { enabled: true, codec: 'hevc', crf: 34, preset: 'ultrafast', threads: 2 }, freeBytes: () => 100 * 1024 ** 3,
+    });
+    await same.init();
+    expect(await until(async () => (await dbmod.getMedia('revAAAAAAA1')).optimized === OPT_REV)).toBe(true);
   });
 
   test('verify() drops and refetches a copy that went bad on disk, keeps a good one', async () => {
diff --git a/server/server.js b/server/server.js
index 9404d29..8af12f5 100644
--- a/server/server.js
+++ b/server/server.js
@@ -506,7 +506,7 @@ app.get('/api/streams', async (c) => {
   if (c.req.query('nocache') !== '1') {
     try {
       const row = await media.getReady(videoId);
-      if (row) {
+      if (servableTo(row, c.req.query('hevc') === '1')) {
         media.touch(videoId);
         return c.json({ ok: true, data: cachedStreamsPayload(videoId, row) });
       }
@@ -962,16 +962,25 @@ const media = createMediaCache({
   autoMaxSeconds: envNum('MEDIA_AUTO_MAX_SECONDS', 3600),
   saveMaxSeconds: MAX_SAVE_SECONDS,
   transcode: {
-    enabled: process.env.MEDIA_TRANSCODE !== '0',
-    crf:     envNum('MEDIA_CRF', 28),
-    preset:  process.env.MEDIA_PRESET || 'slow',
-    threads: envNum('MEDIA_THREADS', 2),
+    enabled:    process.env.MEDIA_TRANSCODE !== '0',
+    codec:      process.env.MEDIA_CODEC || 'hevc',         // hevc | h264
+    crf:        envNum('MEDIA_CRF', 28),
+    preset:     process.env.MEDIA_PRESET || 'medium',
+    threads:    envNum('MEDIA_THREADS', 2),
+    maxSeconds: envNum('MEDIA_OPT_MAX_SECONDS', 3600),
   },
 });
 
+// A cached copy the compression lane turned into HEVC is only handed to
+// clients that said they can decode it (?hevc=1 — the page checks
+// canPlayType for hvc1). Everyone else keeps the pre-cache behaviour.
+function servableTo(row, hevcOk) {
+  return !!row && (row.vcodec !== 'hevc' || hevcOk);
+}
+
 // /api/streams response for a server-cached video: one progressive quality
 // (the mp4 carries its own audio) plus the m4a sidecar for audio-only mode.
-// Same shape as the YouTube path; `serverCached` is additive.
+// Same shape as the YouTube path; `serverCached` and `codec` are additive.
 function cachedStreamsPayload(videoId, row) {
   let meta = {};
   try { meta = JSON.parse(row.meta || '{}'); } catch { /* corrupt — use defaults */ }
@@ -993,6 +1002,7 @@ function cachedStreamsPayload(videoId, row) {
       hasAudio: true,
       url,
       ext:      'mp4',
+      codec:    row.vcodec || 'h264',
     }],
     serverCached: true,
   };
@@ -1117,7 +1127,10 @@ app.get('/api/download/:videoId', async (c) => {
   let cacheErr = null;
   try {
     const row = await media.ensureCached(videoId, { priority: HIGH });
-    return cachedDownloadResponse(videoId, fp, row);
+    // A device that can't decode HEVC must not save the HEVC copy — give it
+    // the legacy H.264 save instead (the ?mux=1 path included).
+    if (servableTo(row, c.req.query('hevc') === '1')) return cachedDownloadResponse(videoId, fp, row);
+    cacheErr = Object.assign(new Error('cached copy is HEVC; client did not ask for it'), { code: 'SKIPPED' });
   } catch (err) {
     cacheErr = err;
     console.warn(`[ytplayer] cache save unavailable for ${videoId} (${err.code || 'error'}): ${err.message}`);