feat: LAN Wi-Fi casting to Chromecast via local HTTP relay

Re-serve decrypted fMP4 video over HTTP on the LAN so a Chromecast can
play the stream. The relay runs in the Electron main process — same trust
boundary as downloads and MSE playback.

- cast-relay.js: HTTP server with BoxAccumulator (reassembles WebRTC
  chunks into moof+mdat pairs), ring buffer, backpressure, finish() for
  clean end-of-stream, fixed port range 19550-19553
- cast-chromecast.js: mDNS discovery (bonjour-service) + CASTV2 protocol
  (castv2-client), connect/reload/disconnect lifecycle
- Seek-aware: relay restarts on every seek, Chromecast reloads new URL;
  generation counter prevents stale async errors from killing active
  restarts; landingPlayheadRef suppresses programmatic seeking events
- Device picker in video top bar with scan, device selection, copy-URL
  fallback, and cast status indicator
- IPC bridge (main/preload/platform) for start/push/stop/finish/status/
  discover/chromecastConnect/chromecastReload/chromecastDisconnect
- Phase 3 design doc for DLNA/Smart TV in docs/cast-smart-tv.md

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

14 files changed, 360 insertions, 11 deletions

diff --git a/packages/meshbay-hub/src/meshbay_hub/static/app.js b/packages/meshbay-hub/src/meshbay_hub/static/app.js
index 50ee9f6..7780d08 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/app.js
@@ -406,6 +406,9 @@ const ICON_PATHS = {
   server:   ['M4 6.5a2 2 0 0 1 2-2h12a2 2 0 0 1 2 2v2a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2v-2z',
              'M4 15.5a2 2 0 0 1 2-2h12a2 2 0 0 1 2 2v2a2 2 0 0 1-2 2H6a2 2 0 0 1-2-2v-2z',
              'M8 7.5h.01', 'M8 16.5h.01'],
+  cast:     ['M2 16.1A5 5 0 0 1 6.9 21', 'M2 12.05A9 9 0 0 1 12.95 21',
+             'M2 8V6a2 2 0 0 1 2-2h16a2 2 0 0 1 2 2v12a2 2 0 0 1-2 2h-6',
+             'M2 21h.01'],
 };
 
 // The M of the wordmark is a picture; the rest is text. Resolved from this
@@ -3766,6 +3769,19 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
   // live; the render needs to reach it for "start from the beginning".
   const requestSeekRef = useRef(null);
   const [resumedFrom, setResumedFrom] = useState(0);
+  const [castActive, setCastActive] = useState(false);
+  const [castUrl, setCastUrl] = useState(null);
+  const [castPickerOpen, setCastPickerOpen] = useState(false);
+  const [castDevices, setCastDevices] = useState([]);
+  const [castScanning, setCastScanning] = useState(false);
+  const [castDeviceName, setCastDeviceName] = useState(null);
+  const castActiveRef = useRef(false);
+  const castCodecRef = useRef(null);
+  const initSegmentRef = useRef(null);
+  const castRestartPendingRef = useRef(false);
+  const castDeviceRef = useRef(null);
+  const castRestartGenRef = useRef(0);
+  const landingPlayheadRef = useRef(false);
 
   /**
    * The buffered range the playhead is actually in, or null.
@@ -3872,6 +3888,7 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
    * So the clock drives this, not the data.
    */
   const pump = useCallback(() => {
+    if (awaitingInitRef.current) return;
     const transport = transportRef.current;
     evictBehind();
     flushQueue();
@@ -3984,6 +4001,7 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         seekTargetRef.current = target;
         outstandingRef.current = STREAM_WINDOW;
         setPhase('loading');
+        console.log('[seek] request', +target.toFixed(1), 'outstanding:', STREAM_WINDOW);
         t.requestStream(entry.id, STREAM_WINDOW, target);
       }, SEEK_DEBOUNCE_MS);
     };
@@ -4010,6 +4028,7 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
             // the range can begin slightly later than the target; never seek
             // behind what is actually there.
             if (Math.abs(v.currentTime - target) > 0.5) {
+              landingPlayheadRef.current = true;
               v.currentTime = Math.max(target, a);
             }
             v.play().catch(() => {});
@@ -4064,25 +4083,33 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
       quotaRef.current = 0;
       awaitingInitRef.current = false;
       seekTargetRef.current = start;
+      console.log('[seek] reinitAt done, start:', start, 'outstanding:', outstandingRef.current, 'queue:', queueRef.current.length);
       setPhase('streaming');
       pump();
     };
 
     const onSeeking = () => {
+      if (landingPlayheadRef.current) {
+        landingPlayheadRef.current = false;
+        return;
+      }
       const v = videoRef.current;
       if (!v || cancelled) return;
       const target = v.currentTime;
       // Inside what is buffered, the browser handles it and the node need not
-      // hear about it at all.
-      const sb = sbRef.current;
-      if (sb) {
-        try {
-          for (let i = 0; i < sb.buffered.length; i++) {
-            if (target >= sb.buffered.start(i) && target <= sb.buffered.end(i) - 0.5) {
-              return;
+      // hear about it at all — unless a cast is active, because the relay
+      // cannot seek within its HTTP stream and must be restarted.
+      if (!castActiveRef.current) {
+        const sb = sbRef.current;
+        if (sb) {
+          try {
+            for (let i = 0; i < sb.buffered.length; i++) {
+              if (target >= sb.buffered.start(i) && target <= sb.buffered.end(i) - 0.5) {
+                return;
+              }
             }
-          }
-        } catch { /* fall through and ask the node */ }
+          } catch { /* fall through and ask the node */ }
+        }
       }
       requestSeek(target);
     };
@@ -4100,6 +4127,7 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         if (cancelled) return;
         if (msg.file_id && msg.file_id !== entry.id) return;
         const mime = `video/mp4; codecs="${msg.codec}"`;
+        castCodecRef.current = msg.codec;
 
         if (!window.MediaSource || !MediaSource.isTypeSupported(mime)) {
           setError(t('video.err_mse', { codec: msg.codec }));
@@ -4115,6 +4143,12 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         // scrubber is drawn from.
         if (sbRef.current && msRef.current
             && msRef.current.readyState === 'open') {
+          console.log('[seek] stream_init landed, start:', msg.start, 'awaitingInit:', awaitingInitRef.current);
+          initSegmentRef.current = null;
+          if (castActiveRef.current && platform.cast.available) {
+            platform.cast.stop().catch(() => {});
+            castRestartPendingRef.current = true;
+          }
           reinitAt(msg.start || 0).catch(() => {
             setError(t('video.err_transport'));
             setPhase('error');
@@ -4122,8 +4156,24 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
           return;
         }
 
+        // If we reach here during a seek (readyState was 'ended' after the
+        // previous stream finished), the seek-landing path above could not run.
+        // A fresh MediaSource is needed, but the seek state must still be reset
+        // or awaitingInit stays true and every segment is dropped forever.
+        awaitingInitRef.current = false;
+        endedRef.current = false;
+        appendingRef.current = false;
+        queueRef.current = [];
+        sbRef.current = null;
+        initSegmentRef.current = null;
+        if (castActiveRef.current && platform.cast.available) {
+          platform.cast.stop().catch(() => {});
+          castRestartPendingRef.current = true;
+        }
+
         const ms = new MediaSource();
         msRef.current = ms;
+        if (blobUrlRef.current) URL.revokeObjectURL(blobUrlRef.current);
         const url = URL.createObjectURL(ms);
         blobUrlRef.current = url;
 
@@ -4187,6 +4237,9 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         // for credit that cannot come. A race, which is why the same seek
         // worked twice and hung on the third.
         outstandingRef.current = Math.max(0, outstandingRef.current - 1);
+        if (awaitingInitRef.current) {
+          console.log('[seek] dropping segment (awaitingInit), outstanding:', outstandingRef.current);
+        }
         // Between asking for a seek and its `stream_init`, everything on the
         // channel is the film we just left. Same file, so `file_id` cannot
         // tell them apart — ordering can.
@@ -4199,6 +4252,44 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         try {
           const plaintext = await window.MeshBayCrypto.decryptChunkBin(
             gekRef.current, entry.id, msg.segment_index, msg.nonce, msg.ct);
+          if (initSegmentRef.current === null) {
+            initSegmentRef.current = plaintext;
+            if (castRestartPendingRef.current && castActiveRef.current
+                && platform.cast.available) {
+              castRestartPendingRef.current = false;
+              const gen = ++castRestartGenRef.current;
+              const device = castDeviceRef.current;
+              platform.cast.start({
+                codec: castCodecRef.current,
+                initSegment: plaintext,
+              }).then(async (result) => {
+                if (castRestartGenRef.current !== gen) return;
+                if (!result) return;
+                setCastUrl(result.url);
+                const status = await platform.cast.status();
+                if (status && status.chromecast && status.chromecast.connected) {
+                  await platform.cast.chromecastReload({ mediaUrl: result.url });
+                } else if (device) {
+                  await platform.cast.chromecastConnect({
+                    deviceId: device.id, mediaUrl: result.url,
+                  });
+                  setCastDeviceName(device.name);
+                } else {
+                  navigator.clipboard.writeText(result.url).catch(() => {});
+                }
+              }).catch((err) => {
+                if (castRestartGenRef.current !== gen) return;
+                console.error('[cast] restart failed:', err);
+                platform.cast.stop().catch(() => {});
+                setCastActive(false); castActiveRef.current = false;
+                setCastUrl(null); setCastDeviceName(null);
+              });
+            }
+          }
+          if (castActiveRef.current && !castRestartPendingRef.current
+              && platform.cast.available) {
+            platform.cast.push(plaintext).catch(() => {});
+          }
           queueRef.current.push(plaintext);
           // pump(), not flushQueue(): arriving data is the moment to top the
           // window back up, and that is what keeps the stream continuous.
@@ -4216,6 +4307,9 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         // would call endOfStream() and truncate the film at the seek point.
         if (awaitingInitRef.current) return;
         endedRef.current = true;
+        if (castActiveRef.current && platform.cast.available) {
+          platform.cast.finish().catch(() => {});
+        }
         flushQueue();
       };
 
@@ -4305,6 +4399,11 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
         writeResumePosition(entry.id, videoRef.current.currentTime,
                             durationRef.current);
       }
+      if (castActiveRef.current && platform.cast.available) {
+        platform.cast.chromecastDisconnect().catch(() => {});
+        platform.cast.stop().catch(() => {});
+        castActiveRef.current = false;
+      }
       window.removeEventListener('pagehide', onPageHide);
       document.removeEventListener('visibilitychange', onVisibility);
       if (videoRef.current) {
@@ -4366,6 +4465,88 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
     }}>
       <div class="video-top-bar">
         <span class="video-title">${entry.name} (${formatSize(entry.size)})</span>
+        ${platform.capabilities.lanCast && html`
+          <div class="cast-wrapper" style="position:relative">
+            <button class="video-close ${castActive ? 'cast-active' : ''}"
+              onClick=${async () => {
+                if (castActive) {
+                  await platform.cast.chromecastDisconnect().catch(() => {});
+                  await platform.cast.stop();
+                  setCastActive(false); castActiveRef.current = false;
+                  setCastUrl(null);
+                  setCastDeviceName(null);
+                  castDeviceRef.current = null;
+                } else if (castCodecRef.current && initSegmentRef.current) {
+                  if (castPickerOpen) {
+                    setCastPickerOpen(false);
+                  } else {
+                    setCastPickerOpen(true);
+                    setCastScanning(true);
+                    setCastDevices([]);
+                    platform.cast.discover().then((devices) => {
+                      setCastDevices(devices || []);
+                      setCastScanning(false);
+                    }).catch(() => setCastScanning(false));
+                  }
+                }
+              }}
+              title="${castActive ? t('cast.stop') : t('cast.start')}">
+              <${Icon} name="cast" /></button>
+            ${castPickerOpen && html`
+              <div class="cast-picker">
+                ${castScanning && html`
+                  <div class="cast-picker-item cast-picker-scanning">
+                    <span class="spinner" style="width:14px;height:14px"></span>
+                    ${t('cast.scanning')}
+                  </div>
+                `}
+                ${castDevices.map(d => html`
+                  <button class="cast-picker-item" onClick=${() => {
+                    setCastPickerOpen(false);
+                    setCastDeviceName(d.name);
+                    setCastActive(true); castActiveRef.current = true;
+                    castRestartPendingRef.current = true;
+                    castDeviceRef.current = d;
+                    if (videoRef.current && requestSeekRef.current) {
+                      requestSeekRef.current(videoRef.current.currentTime);
+                    }
+                  }}>
+                    <${Icon} name="cast" /> ${d.name}
+                  </button>
+                `)}
+                ${!castScanning && castDevices.length === 0 && html`
+                  <div class="cast-picker-item cast-picker-empty">
+                    ${t('cast.no_devices')}
+                  </div>
+                `}
+                <div class="cast-picker-sep"></div>
+                <button class="cast-picker-item" onClick=${async () => {
+                  setCastPickerOpen(false);
+                  setCastActive(true); castActiveRef.current = true;
+                  castRestartPendingRef.current = true;
+                  if (videoRef.current && requestSeekRef.current) {
+                    requestSeekRef.current(videoRef.current.currentTime);
+                  }
+                }}>
+                  <${Icon} name="clip" /> ${t('cast.copy_url')}
+                </button>
+              </div>
+            `}
+          </div>
+        `}
+        ${castUrl && html`
+          <span class="cast-status-label">
+            ${castDeviceName
+              ? castDeviceName
+              : html`<input class="cast-url-input" readOnly value=${castUrl}
+                  onClick=${(e) => {
+                    e.target.select();
+                    navigator.clipboard.writeText(castUrl).catch(() => {});
+                  }}
+                  title="${t('cast.copy_url')}" />`
+            }
+          </span>
+        `}
         ${onDownload && html`
           <button class="video-close ${dlBusy ? 'dl-active' : ''}" disabled=${dlBusy}
             onClick=${() => {
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
index ec56f03..e309834 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/de.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transport nicht verbunden',
   'video.err_mse': 'Codec wird für das Streaming nicht unterstützt: {codec}',
 
+  // LAN-Cast
+  'cast.start': 'Auf Gerät übertragen',
+  'cast.stop': 'Übertragung beenden',
+  'cast.copy_url': 'Stream-URL kopieren',
+  'cast.copied': 'URL kopiert',
+  'cast.scanning': 'Suche nach Geräten…',
+  'cast.no_devices': 'Keine Geräte gefunden',
+
   // Settings
   'settings.title': 'Einstellungen',
   'settings.coming_soon': 'Demnächst verfügbar.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
index a8392c7..9a5058e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/en.js
@@ -152,6 +152,14 @@ export default {
   'video.err_transport': 'Transport not connected',
   'video.err_mse': 'Codec not supported for streaming: {codec}',
 
+  // LAN cast
+  'cast.start': 'Cast to device',
+  'cast.stop': 'Stop casting',
+  'cast.copy_url': 'Copy stream URL',
+  'cast.copied': 'URL copied',
+  'cast.scanning': 'Scanning for devices…',
+  'cast.no_devices': 'No devices found',
+
   // Settings
   'settings.title': 'Settings',
   'settings.coming_soon': 'Coming soon.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
index 5afb3c3..5a95347 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/es.js
@@ -152,6 +152,14 @@ export default {
   'video.err_transport': 'Transporte no conectado',
   'video.err_mse': 'Códec no compatible con la reproducción en continuo: {codec}',
 
+  // LAN cast
+  'cast.start': 'Enviar a dispositivo',
+  'cast.stop': 'Detener envío',
+  'cast.copy_url': 'Copiar URL del stream',
+  'cast.copied': 'URL copiada',
+  'cast.scanning': 'Buscando dispositivos…',
+  'cast.no_devices': 'No se encontraron dispositivos',
+
   // Settings
   'settings.title': 'Ajustes',
   'settings.coming_soon': 'Próximamente.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
index 9eb2f30..4139fc9 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/fr.js
@@ -153,6 +153,14 @@ export default {
   'video.err_transport': 'Transport non connecté',
   'video.err_mse': 'Codec non pris en charge pour la diffusion : {codec}',
 
+  // LAN cast
+  'cast.start': 'Diffuser sur un appareil',
+  'cast.stop': 'Arrêter la diffusion',
+  'cast.copy_url': "Copier l'URL du flux",
+  'cast.copied': 'URL copiée',
+  'cast.scanning': "Recherche d'appareils…",
+  'cast.no_devices': 'Aucun appareil trouvé',
+
   // Settings
   'settings.title': 'Paramètres',
   'settings.coming_soon': 'Bientôt disponible.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
index 5653ec0..531c8f7 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/it.js
@@ -153,6 +153,14 @@ export default {
   'video.err_transport': 'Trasporto non connesso',
   'video.err_mse': 'Codec non supportato per lo streaming: {codec}',
 
+  // LAN cast
+  'cast.start': 'Trasmetti al dispositivo',
+  'cast.stop': 'Interrompi trasmissione',
+  'cast.copy_url': 'Copia URL dello stream',
+  'cast.copied': 'URL copiato',
+  'cast.scanning': 'Ricerca dispositivi…',
+  'cast.no_devices': 'Nessun dispositivo trovato',
+
   // Settings
   'settings.title': 'Impostazioni',
   'settings.coming_soon': 'Prossimamente.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
index aa3899d..1a68827 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/ja.js
@@ -150,6 +150,14 @@ export default {
   'video.err_transport': 'トランスポートが接続されていません',
   'video.err_mse': 'ストリーミング再生に対応していないコーデックです：{codec}',
 
+  // LAN cast
+  'cast.start': 'デバイスにキャスト',
+  'cast.stop': 'キャストを停止',
+  'cast.copy_url': 'ストリームURLをコピー',
+  'cast.copied': 'URLをコピーしました',
+  'cast.scanning': 'デバイスを検索中…',
+  'cast.no_devices': 'デバイスが見つかりません',
+
   // Settings
   'settings.title': '設定',
   'settings.coming_soon': '近日公開。',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
index c5841dd..d0c9649 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/nl.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transport niet verbonden',
   'video.err_mse': 'Codec wordt niet ondersteund voor streamen: {codec}',
 
+  // LAN cast
+  'cast.start': 'Naar apparaat casten',
+  'cast.stop': 'Casten stoppen',
+  'cast.copy_url': 'Stream-URL kopiëren',
+  'cast.copied': 'URL gekopieerd',
+  'cast.scanning': 'Apparaten zoeken…',
+  'cast.no_devices': 'Geen apparaten gevonden',
+
   // Settings
   'settings.title': 'Instellingen',
   'settings.coming_soon': 'Binnenkort beschikbaar.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
index eec144b..630548b 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/pl.js
@@ -159,6 +159,14 @@ export default {
   'video.err_transport': 'Transport nie jest połączony',
   'video.err_mse': 'Kodek nieobsługiwany przy odtwarzaniu strumieniowym: {codec}',
 
+  // LAN cast
+  'cast.start': 'Przesyłaj na urządzenie',
+  'cast.stop': 'Zatrzymaj przesyłanie',
+  'cast.copy_url': 'Kopiuj URL strumienia',
+  'cast.copied': 'URL skopiowany',
+  'cast.scanning': 'Wyszukiwanie urządzeń…',
+  'cast.no_devices': 'Nie znaleziono urządzeń',
+
   // Settings
   'settings.title': 'Ustawienia',
   'settings.coming_soon': 'Wkrótce.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
index ce2adf2..9a6809a 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/pt-BR.js
@@ -154,6 +154,14 @@ export default {
   'video.err_transport': 'Transporte não conectado',
   'video.err_mse': 'Codec sem suporte para transmissão: {codec}',
 
+  // LAN cast
+  'cast.start': 'Transmitir para dispositivo',
+  'cast.stop': 'Parar transmissão',
+  'cast.copy_url': 'Copiar URL do stream',
+  'cast.copied': 'URL copiada',
+  'cast.scanning': 'Procurando dispositivos…',
+  'cast.no_devices': 'Nenhum dispositivo encontrado',
+
   // Settings
   'settings.title': 'Configurações',
   'settings.coming_soon': 'Em breve.',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
index f249835..549b77e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/locales/zh-CN.js
@@ -147,6 +147,14 @@ export default {
   'video.err_transport': '传输未连接',
   'video.err_mse': '该编解码器不支持流式播放：{codec}',
 
+  // LAN cast
+  'cast.start': '投射到设备',
+  'cast.stop': '停止投射',
+  'cast.copy_url': '复制流媒体链接',
+  'cast.copied': '链接已复制',
+  'cast.scanning': '正在搜索设备…',
+  'cast.no_devices': '未找到设备',
+
   // Settings
   'settings.title': '设置',
   'settings.coming_soon': '即将推出。',
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/platform.js b/packages/meshbay-hub/src/meshbay_hub/static/platform.js
index 02107f5..d400b4e 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/platform.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/platform.js
@@ -46,6 +46,8 @@ export const capabilities = {
   localFolders: Boolean(bridge && bridge.capabilities && bridge.capabilities.localFolders),
   // A real save dialog and a write that does not pass through the page.
   nativeSave: Boolean(bridge && bridge.capabilities && bridge.capabilities.nativeSave),
+  // Cast decrypted video to a device on the same LAN via a local HTTP relay.
+  lanCast: Boolean(bridge && bridge.capabilities && bridge.capabilities.lanCast),
 };
 
 /**
@@ -234,8 +236,56 @@ export const node = {
   },
 };
 
+/**
+ * LAN cast relay — re-serve decrypted video segments over HTTP so a
+ * Chromecast or Smart TV on the same Wi-Fi can play the stream.
+ *
+ * Absent in a browser, where the relay cannot run: there is no main process
+ * to bind a server socket in, and a page cannot open one.
+ */
+export const cast = {
+  available: Boolean(bridge && bridge.cast),
+  async start(opts) {
+    if (!bridge || !bridge.cast) return null;
+    return bridge.cast.start(opts);
+  },
+  async push(data) {
+    if (!bridge || !bridge.cast) return false;
+    return bridge.cast.push(data);
+  },
+  async stop() {
+    if (!bridge || !bridge.cast) return false;
+    return bridge.cast.stop();
+  },
+  async finish() {
+    if (!bridge || !bridge.cast) return false;
+    return bridge.cast.finish();
+  },
+  async status() {
+    if (!bridge || !bridge.cast) return null;
+    return bridge.cast.status();
+  },
+  async discover() {
+    if (!bridge || !bridge.cast) return [];
+    return bridge.cast.discover();
+  },
+  async chromecastConnect(opts) {
+    if (!bridge || !bridge.cast) return null;
+    return bridge.cast.chromecastConnect(opts);
+  },
+  async chromecastReload(opts) {
+    if (!bridge || !bridge.cast) return null;
+    return bridge.cast.chromecastReload(opts);
+  },
+  async chromecastDisconnect() {
+    if (!bridge || !bridge.cast) return false;
+    return bridge.cast.chromecastDisconnect();
+  },
+};
+
 export default { isNative, hubBase, capabilities, secrets, nativeSave,
-                 apiFetch, device, bridgeMessage, folder, rootPicker, node };
+                 apiFetch, device, bridgeMessage, folder, rootPicker, node,
+                 cast };
 
 // Also a global, because `transport.js` is loaded as a classic script — it
 // predates the module graph and exposes `MeshBayTransport` the same way. The
@@ -244,5 +294,6 @@ export default { isNative, hubBase, capabilities, secrets, nativeSave,
 if (typeof window !== 'undefined') {
   window.MeshBayPlatform = { isNative, hubBase, capabilities, secrets,
                              nativeSave, apiFetch, device,
-                             bridgeMessage, folder, rootPicker, node };
+                             bridgeMessage, folder, rootPicker, node,
+                             cast };
 }
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/style.css b/packages/meshbay-hub/src/meshbay_hub/static/style.css
index 7ce073a..ee51a8a 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/style.css
+++ b/packages/meshbay-hub/src/meshbay_hub/static/style.css
@@ -1060,6 +1060,39 @@ button:disabled { opacity: 0.5; cursor: not-allowed; }
 }
 .video-close:hover { background: rgba(255, 255, 255, 0.25); }
 .video-close.dl-active { background: rgba(34, 197, 94, 0.25); pointer-events: none; }
+.video-close.cast-active { background: rgba(59, 130, 246, 0.35); }
+.video-close.cast-active:hover { background: rgba(59, 130, 246, 0.5); }
+.cast-url-input {
+  background: rgba(255, 255, 255, 0.08); border: 1px solid rgba(255, 255, 255, 0.15);
+  border-radius: 4px; color: #e2e8f0; font-size: 0.75em; font-family: inherit;
+  padding: 4px 8px; min-width: 0; flex: 1; max-width: 420px;
+  cursor: text; outline: none;
+}
+.cast-url-input:focus { border-color: rgba(59, 130, 246, 0.6); }
+.cast-wrapper { display: inline-block; }
+.cast-picker {
+  position: absolute; top: calc(100% + 4px); right: 0; z-index: 100;
+  background: rgba(28, 28, 32, 0.97); border: 1px solid rgba(255, 255, 255, 0.14);
+  border-radius: 8px; padding: 4px 0; min-width: 230px;
+  box-shadow: 0 6px 20px rgba(0, 0, 0, 0.45);
+}
+.cast-picker-item {
+  display: flex; align-items: center; gap: 8px; width: 100%;
+  padding: 9px 14px; background: none; border: none;
+  color: #e2e8f0; font-size: 0.82em; cursor: pointer; text-align: left;
+  font-family: inherit;
+}
+.cast-picker-item:hover { background: rgba(255, 255, 255, 0.09); }
+.cast-picker-item svg { width: 16px; height: 16px; flex-shrink: 0; }
+.cast-picker-scanning { color: #94a3b8; cursor: default; }
+.cast-picker-scanning:hover { background: none; }
+.cast-picker-empty { color: #64748b; cursor: default; font-style: italic; }
+.cast-picker-empty:hover { background: none; }
+.cast-picker-sep { height: 1px; margin: 4px 10px; background: rgba(255,255,255,0.1); }
+.cast-status-label {
+  color: #94a3b8; font-size: 0.78em; display: flex; align-items: center;
+  max-width: 420px; overflow: hidden; white-space: nowrap;
+}
 
 .video-container {
   width: 100%;
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/transport.js b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
index 17886f4..2cdf15d 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/transport.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/transport.js
@@ -742,12 +742,14 @@ class MeshBayTransport {
     // `start` is a seek: the node retires whatever this session was streaming
     // and spawns ffmpeg again from there. Omitted or zero is the film's
     // beginning, which is what an 0.1 node understands.
+    console.log('[stream] sending stream_req start:', start, 'credits:', credits);
     this._send({ type: 'stream_req', v: '0.1', file_id: fileId, credits, start });
   }
 
   /** Room for `n` more segments. */
   grantStreamCredit(n = 1) {
     if (!this._connected) return;
+    console.log('[stream] grant credit:', n);
     this._send({ type: 'stream_more', v: '0.1', n });
   }
 
@@ -1200,6 +1202,7 @@ class MeshBayTransport {
       return;
     }
     if (msg.type === 'stream_init') {
+      console.log('[stream] recv stream_init, start:', msg.start, 'codec:', msg.codec, 'handler:', !!this._onStreamInit);
       if (this._onStreamInit) this._onStreamInit(msg);
       return;
     }
@@ -1208,6 +1211,7 @@ class MeshBayTransport {
       return;
     }
     if (msg.type === 'stream_end') {
+      console.log('[stream] recv stream_end');
       if (this._onStreamEnd) this._onStreamEnd(msg);
       return;
     }