feat(cast): music on the TV, the music bar as its remote

A cast button in Music's toolbar and in the music bar. With a television
chosen, each decrypted track goes to the relay with its cover — found as the
album card finds it — and plays there as music with its title, artist and
album; the bar's play, pause, seek, previous and next drive the receiver, its
clock is the receiver's, and the end of a track there moves the queue on.
A film or a photo taking the television pauses the bar; stopping the cast
carries the track on locally.

Photos and tracks now share one path: a whole file sent to the relay in
pieces (binary frames on Android, written to disk there), served at /file
with byte ranges and its cover at /cover, and loaded as what the relay says
it is. cast:image is gone; cast:chromecast:seek is new.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

24 files changed, 1331 insertions, 436 deletions

diff --git a/CLAUDE.md b/CLAUDE.md
index 32ffc25..d5b66c7 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -1033,7 +1033,7 @@ here are kept only where they are a rule about *editing* the code.
 | Where the hub is | `platform.js` — `hubBase()` | **the only file allowed to decide this** (§8.3) |
 | Downloads, decrypt pipeline | `file-utils.js`, `downloads.js`, `sw.js` | §8.5 |
 | Video player | `video-player.js` — `pump()` is the only place credit is granted | §8.5 |
-| The television a session casts to, photos on it | `cast-session.js` | §11.4 |
+| The television a session casts to; photos and music on it | `cast-session.js`, `music-player.js` | §11.4 |
 | Transfers widget | `transfers.js` | §5.5 |
 | Cross-group merge | `source-merge.js`, `group-name.js` | §9.11 |
 | Node page | `node-page.js` | §6.7 |
@@ -1068,7 +1068,7 @@ when `ANDROID_HOME` is set (`test_android_shell.py`).
 | An invitation answered on the home page (accept, decline), in both engines | `packages/meshbay-hub/tests/harness/invitation_probe.py` |
 | A group owner's invited list and host approvals, in both engines | `packages/meshbay-hub/tests/harness/group_hosts_probe.py` |
 | A show's modal and the player, walked episode to episode | `packages/meshbay-hub/tests/harness/video_series_probe.py` |
-| A television chosen once, then photos and a film sent to it, in both engines | `packages/meshbay-hub/tests/harness/cast_session_probe.py` |
+| A television chosen once, then photos, a film and music sent to it, in both engines | `packages/meshbay-hub/tests/harness/cast_session_probe.py` |
 | A lazily loaded view whose module answers 404 (a tab older than the deploy) | `packages/meshbay-hub/tests/harness/lazy_failure_probe.py` |
 
 ## meshbay.org server (target state)
diff --git a/docs/MESHBAY_DESIGN.md b/docs/MESHBAY_DESIGN.md
index 64364b0..5d33f5f 100644
--- a/docs/MESHBAY_DESIGN.md
+++ b/docs/MESHBAY_DESIGN.md
@@ -3423,27 +3423,49 @@ pauses the local element too, which otherwise goes on fetching for nobody. The
 copy-URL cast has no receiver to read and keeps the ordinary player.
 
 **A television is chosen for the session, not for one film**
-(`cast-session.js`). Any cast button — Videos' toolbar, the Photos toolbar, a
-photo album's bar, the lightbox, the player — sets it, and it is held in memory
-only. A film opened
+(`cast-session.js`). Any cast button — Videos', Photos' and Music's toolbars, a
+photo album's bar, the lightbox, the video player, the music bar — sets it, and
+it is held in memory only. A film opened
 while one is set starts its cast as a restart does: pending until the first
 segment, then the relay and `connect` (or `reload`, when the receiver is already
 connected), with the player drawn as the remote from the start. *Stop casting*
 clears it, from the player's remote or from any button.
 
-**A photo is served at `/image`, one at a time** (`cast:image`). The page scales
-it to fit 1920×1080, applies its EXIF orientation and re-encodes it as JPEG
-before it leaves: a camera original is too large for a receiver to decode in good
-time, and some formats it does not decode at all. The relay starts for it if
-nothing else has, serves it behind the stream's token with a versioned address
-(a receiver handed the same URL twice shows what it already has), and accepts
-only `image/jpeg`, `image/png` or `image/webp`. **The shell, not the page, says
-what the receiver loads:** the relay's photo URL is loaded as a picture
-(`streamType: NONE`, photo metadata, no subtitles), any other relay URL as the
-stream, and on Android no URL but the relay's own is accepted at all. A photo
-does not start the foreground service, and its load answers as soon as the
-receiver accepts it: a photo never reaches PLAYING. Only the newest photo asked
-for is sent; paging quickly shows where the reader stopped.
+**A photo or a music track is served whole at `/file`, one at a time**
+(`cast:file:begin`, `:write`, `:end`), its cover at `/cover`. It crosses in
+pieces — binary frames of a megabyte on Android — because a lossless track is
+too large for one bridge message, and on Android it is written to the relay's
+spool directory rather than held. The relay starts for it if nothing else has,
+serves it behind the stream's token with a versioned address (a receiver handed
+the same URL twice shows what it already has), honours byte ranges (a receiver
+seeks in a track that way), and accepts only pictures and the audio types the
+music player plays. **The shell, not the page, says what the receiver loads:**
+the relay's file is loaded as what the relay was told it is — a photo as a
+picture (`streamType: NONE`), a track as music (`BUFFERED`, with title, artist,
+album and the relay's cover URL), at `startAt` seconds for a track picked up
+mid-song — any other relay URL as the stream, and on Android no URL but the
+relay's own is accepted at all. A file does not start the foreground service; a
+photo's load answers as soon as the receiver accepts it, since a photo never
+reaches PLAYING.
+
+**A photo is scaled before it leaves.** The page fits it to 1920×1080, applies
+its EXIF orientation and re-encodes it as JPEG: a camera original is too large
+for a receiver to decode in good time, and some formats it does not decode at
+all. Only the newest photo asked for is sent; paging quickly shows where the
+reader stopped.
+
+**With a television chosen, the music bar is its remote.** Each track, once
+decrypted, goes to the relay with its cover instead of to the `<audio>`
+element, which keeps the source for its duration only. Play, pause, seek
+(`cast:chromecast:seek`) and previous drive the receiver; the bar's clock is the
+receiver's, polled once a second; and the receiver's IDLE/FINISHED moves the
+queue on as `ended` does, once per track, because the receiver keeps reporting
+it until it is given something else. The session records which view the
+television is showing (`castSession.owner`): a film or a photo opened meanwhile
+takes it, the bar pauses and stops reading the receiver, and play gives it the
+track back from where it was. A television chosen mid-track picks the track up
+where it was; *Stop casting* carries it on locally from where the television
+was.
 
 **The interface itself is not cast.** The default media receiver plays what it
 is given and renders nothing of its own, and a rendered interface sent to it as
diff --git a/docs/USERGUIDE.md b/docs/USERGUIDE.md
index 3b2f16c..97ea679 100644
--- a/docs/USERGUIDE.md
+++ b/docs/USERGUIDE.md
@@ -394,11 +394,11 @@ resume.
 
 ### Casting to a TV
 
-**The desktop and Android applications.** Films and photos can be sent to a
-cast-capable TV or dongle on the same network. The cast button is in the
-Videos toolbar, at the top of Photos, in an album's bar and in the photo
-viewer — in a group and in Search alike — and *Cast to device* is in the
-player. Devices appear as
+**The desktop and Android applications.** Films, photos and music can be sent
+to a cast-capable TV or dongle on the same network. The cast button is in the
+Videos and Music toolbars, at the top of Photos, in an album's bar, in the photo
+viewer and in the music bar — in a group and in Search alike — and *Cast to
+device* is in the video player. Devices appear as
 they answer, usually within a couple of seconds; the search carries on for a
 few more, for a TV that is still waking up.
 
@@ -407,12 +407,19 @@ or from the player. Every film opened plays on it, and the player opens as its
 remote: the position shown is the TV's, with play/pause, 30-second jumps and a
 slider to go anywhere in the film. Every photo opened in the viewer is shown on
 it, and a slideshow pages the TV along with the screen. Choosing a TV from an
-album's bar opens its first photo. On a phone, a film goes on playing silently
-on the phone while the TV shows it, and the screen can be turned off.
+album's bar opens its first photo. Music plays on it too, with the cover, title
+and artist on the screen: the music bar becomes its remote — play, pause, the
+slider, previous and next — and the queue moves on when the TV reaches the end
+of a track. Choosing the TV in the middle of a song carries it on there; *Stop
+casting* carries it on here. On a phone, a film goes on playing silently on the
+phone while the TV shows it, and the screen can be turned off, as it can while
+music plays on the TV.
 
 Photos are sent scaled to the TV's screen, upright, as an ordinary picture.
 The menus, covers and summaries stay on your phone or computer: the TV shows
-what is playing, not the application.
+what is playing, not the application. It plays it in the TV's standard cast
+player, which shows its own name, *Default Media Receiver*, on the screen; a
+player of MeshBay's own is not built.
 
 The application decrypts the film and relays it to the TV itself, over your LAN.
 The TV is not a group member and holds no key — which is also why the relay's
@@ -993,8 +1000,8 @@ Better to know now than to go looking for it:
 - **Hubs do not talk to each other yet.** Everyone in a group needs an account
   on the same hub.
 - **Casting reaches Chromecast devices** from the desktop and Android
-  applications, for films and photos. Music is not cast yet. Support for other
-  TV protocols is designed but not built.
+  applications, for films, photos and music. Support for other TV protocols is
+  designed but not built.
 - **Some subtitle tracks cannot be shown** — the ones stored as images rather
   than text, roughly one embedded track in five. Displaying them would need
   text recognition.
diff --git a/packages/meshbay-android/app/src/main/assets/bridge/meshbay-bridge.js b/packages/meshbay-android/app/src/main/assets/bridge/meshbay-bridge.js
index 21d27df..b71b5e8 100644
--- a/packages/meshbay-android/app/src/main/assets/bridge/meshbay-bridge.js
+++ b/packages/meshbay-android/app/src/main/assets/bridge/meshbay-bridge.js
@@ -50,6 +50,10 @@
   // per 48 KB chunk). Without ArrayBuffer messages, base64 over JSON.
   const SAVE_WRITE = 1;
   const CAST_PUSH = 2;
+  const CAST_FILE = 3;
+  // A file crosses in pieces this size: big enough to be few, small enough
+  // that no one message is a burden to the WebView or the bridge.
+  const FILE_PIECE = 1024 * 1024;
   const bytesOf = (chunk) => (chunk instanceof Uint8Array ? chunk
     : ArrayBuffer.isView(chunk) ? new Uint8Array(chunk.buffer, chunk.byteOffset, chunk.byteLength)
       : new Uint8Array(chunk));
@@ -151,7 +155,19 @@
       push: (data) => pushSegment(data),
       stop: () => call('cast:stop'),
       subtitle: (sub) => call('cast:subtitle', sub),
-      image: (img) => call('cast:image', { bytes: base64Of(bytesOf(img.bytes)), type: img.type }),
+      // A whole file — a photo, a track — in pieces: one message the size of a
+      // lossless track would be the WebView's to refuse.
+      file: async (f) => {
+        const bytes = bytesOf(f.bytes);
+        const cover = f.cover ? { bytes: base64Of(bytesOf(f.cover.bytes)), type: f.cover.type } : null;
+        await call('cast:file:begin', { type: f.type, size: bytes.length, cover,
+                                        title: f.title, artist: f.artist, album: f.album });
+        for (let at = 0; at < bytes.length; at += FILE_PIECE) {
+          const piece = bytes.subarray(at, at + FILE_PIECE);
+          await (BINARY ? sendBinary(CAST_FILE, 0, piece) : call('cast:file:write', base64Of(piece)));
+        }
+        return call('cast:file:end');
+      },
       finish: () => call('cast:finish'),
       status: () => call('cast:status'),
       scan: () => call('cast:scan'),
@@ -161,6 +177,7 @@
       chromecastDisconnect: () => call('cast:chromecast:disconnect'),
       chromecastPause: () => call('cast:chromecast:pause'),
       chromecastPlay: () => call('cast:chromecast:play'),
+      chromecastSeek: (seconds) => call('cast:chromecast:seek', seconds),
     } } : {}),
 
     // Music is playing: keep the process, the Wi-Fi and the page awake with
diff --git a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/bridge/Channels.kt b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/bridge/Channels.kt
index 7542fa1..f7094a0 100644
--- a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/bridge/Channels.kt
+++ b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/bridge/Channels.kt
@@ -63,6 +63,7 @@ class Channels(
     fun binary(frame: BinaryFrame): Any? = when (frame.channel) {
         BinaryFrame.SAVE_WRITE -> saves().write(frame.handle, frame.bytes, frame.offset, frame.length)
         BinaryFrame.CAST_PUSH -> (cast ?: throw Refused("Refused: no such channel")).push(frame.bytes, frame.offset, frame.length)
+        BinaryFrame.CAST_FILE -> (cast ?: throw Refused("Refused: no such channel")).writeFile(frame.bytes, frame.offset, frame.length)
         else -> throw Refused("Refused: no such channel")
     }
 
@@ -72,7 +73,7 @@ class Channels(
      * they could overtake one another; these run on one thread, in arrival order.
      */
     fun ordered(channel: String) = cast?.ordered(channel) == true
-    fun ordered(frame: BinaryFrame) = frame.channel == BinaryFrame.CAST_PUSH
+    fun ordered(frame: BinaryFrame) = frame.channel == BinaryFrame.CAST_PUSH || frame.channel == BinaryFrame.CAST_FILE
 
     private fun setLocale(code: String): String {
         // A code, never text, and only one the package has a catalogue for.
diff --git a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastChannels.kt b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastChannels.kt
index 6be5d72..edaec67 100644
--- a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastChannels.kt
+++ b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastChannels.kt
@@ -26,8 +26,9 @@ class CastChannels(
 
     fun handles(channel: String) = channel.startsWith("cast:")
 
-    /** What must reach the relay in the order the page sent it: start, pushes, subtitle, photo, finish, stop. */
-    fun ordered(channel: String) = channel in setOf("cast:start", "cast:push", "cast:subtitle", "cast:image", "cast:finish", "cast:stop")
+    /** What must reach the relay in the order the page sent it: start, pushes, subtitle, a file's pieces, finish, stop. */
+    fun ordered(channel: String) = channel in setOf("cast:start", "cast:push", "cast:subtitle",
+        "cast:file:begin", "cast:file:write", "cast:file:end", "cast:finish", "cast:stop")
 
     fun call(channel: String, a: JSONArray): Any? = when (channel) {
         "cast:start" -> {
@@ -38,11 +39,20 @@ class CastChannels(
             started
         }
         "cast:subtitle" -> relay.setSubtitle(a.optJSONObject(0))
-        // No foreground service for a photo: the receiver has it once loaded.
-        "cast:image" -> {
+        // A whole file — a photo, a track — in pieces. No foreground service
+        // for one: a photo needs nothing once loaded, and music keeps the page
+        // alive through its own playback hold.
+        "cast:file:begin" -> {
             val o = a.optJSONObject(0) ?: JSONObject()
-            relay.showImage(Base64.getDecoder().decode(o.optString("bytes", "")), o.optString("type", ""))
+            val cover = o.optJSONObject("cover")
+            relay.beginFile(o.optString("type", ""), o.optLong("size", -1),
+                cover?.optString("bytes", "")?.takeIf { it.isNotEmpty() }?.let { Base64.getDecoder().decode(it) },
+                cover?.optString("type", ""), o)
         }
+        "cast:file:write" -> {   // the base64 path, for a WebView without ArrayBuffer messages
+            relay.writeFile(Base64.getDecoder().decode(a.optString(0, "")))
+        }
+        "cast:file:end" -> relay.endFile()
         "cast:push" -> {   // the base64 path, for a WebView without ArrayBuffer messages
             relay.push(Base64.getDecoder().decode(a.optString(0, ""))); true
         }
@@ -56,15 +66,16 @@ class CastChannels(
         "cast:chromecast:connect" -> {
             val o = a.optJSONObject(0) ?: JSONObject()
             val url = relayUrl(o)
-            reported { control.connect(o.optString("deviceId", ""), url, subtitleFor(url, o), typeOf(url)) }
+            reported { control.connect(o.optString("deviceId", ""), url, subtitleFor(url, o), fileOf(url), startOf(url, o)) }
         }
         "cast:chromecast:reload" -> {
             val o = a.optJSONObject(0) ?: JSONObject()
             val url = relayUrl(o)
-            reported { control.reload(url, subtitleFor(url, o), typeOf(url)) }
+            reported { control.reload(url, subtitleFor(url, o), fileOf(url), startOf(url, o)) }
         }
         "cast:chromecast:pause" -> control.pause()
         "cast:chromecast:play" -> control.play()
+        "cast:chromecast:seek" -> control.seek(a.optDouble(0, 0.0))
         "cast:chromecast:disconnect" -> control.disconnect()
         else -> throw Refused("Refused: no such channel")
     }
@@ -84,26 +95,37 @@ class CastChannels(
 
     fun push(bytes: ByteArray, offset: Int, length: Int): Boolean { relay.push(bytes, offset, length); return true }
 
+    fun writeFile(bytes: ByteArray, offset: Int, length: Int): Boolean = relay.writeFile(bytes, offset, length)
+
     /**
      * The receiver is only ever pointed at this relay. A URL the page names is
-     * accepted when it is the relay's own stream or photo, and refused
+     * accepted when it is the relay's own stream or file, and refused
      * otherwise — a page cannot use this application to make a television
      * fetch anything else.
      */
     private fun relayUrl(o: JSONObject): String {
         val asked = o.optString("mediaUrl", "")
         val ours = relay.url ?: throw Refused("The cast relay is not running")
-        if (asked != ours && asked != relay.imageUrl) throw Refused("Refused: not this relay's stream")
+        if (asked != ours && asked != relay.fileUrl) throw Refused("Refused: not this relay's stream")
         return asked
     }
 
-    /** The relay's photo is loaded as a picture, anything else as the stream; the page does not say which. */
-    private fun typeOf(url: String): String =
-        if (url == relay.imageUrl) relay.imageType ?: "image/jpeg" else "video/mp4"
+    /**
+     * The relay's file is loaded as what the relay says it is — its type, and
+     * the title, artist, album and cover it was given — and anything else as
+     * the stream (null here); the page does not say which.
+     */
+    private fun fileOf(url: String): JSONObject? =
+        if (url != relay.fileUrl) null
+        else JSONObject().put("contentType", relay.fileType).put("meta", relay.fileMeta() ?: JSONObject())
+
+    /** Where in a track to begin; a film starts where its relay does. */
+    private fun startOf(url: String, o: JSONObject): Double =
+        if (url == relay.fileUrl) maxOf(0.0, o.optDouble("startAt", 0.0)) else 0.0
 
-    /** As main.js: no subtitle named means the relay's current one; a photo has none. */
+    /** As main.js: no subtitle named means the relay's current one; a file has none. */
     private fun subtitleFor(url: String, o: JSONObject): JSONObject? = when {
-        url == relay.imageUrl -> null
+        url == relay.fileUrl -> null
         o.has("subtitle") && o.get("subtitle") != JSONObject.NULL -> o.optJSONObject("subtitle")
         else -> relay.subtitleInfo()
     }
diff --git a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastControl.kt b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastControl.kt
index 56a1f5e..0d18a90 100644
--- a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastControl.kt
+++ b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastControl.kt
@@ -2,6 +2,7 @@ package org.meshbay.client.cast
 
 import android.content.Context
 import android.graphics.Color
+import android.net.Uri
 import android.os.Handler
 import android.os.Looper
 import android.util.Log
@@ -11,6 +12,8 @@ import com.google.android.gms.cast.CastMediaControlIntent
 import com.google.android.gms.cast.MediaInfo
 import com.google.android.gms.cast.MediaLoadRequestData
 import com.google.android.gms.cast.MediaMetadata
+import com.google.android.gms.cast.MediaSeekOptions
+import com.google.android.gms.common.images.WebImage
 import com.google.android.gms.cast.MediaStatus
 import com.google.android.gms.cast.MediaTrack
 import com.google.android.gms.cast.TextTrackStyle
@@ -112,7 +115,7 @@ class CastControl(private val context: Context) {
     }
 
     /** Connect, launch the default receiver, load; answers once the receiver has. */
-    fun connect(deviceId: String, mediaUrl: String, subtitle: JSONObject?, contentType: String = "video/mp4"): JSONObject {
+    fun connect(deviceId: String, mediaUrl: String, subtitle: JSONObject?, file: JSONObject? = null, startAt: Double = 0.0): JSONObject {
         need()
         val session = onMain {
             val cast = CastContext.getSharedInstance(context)
@@ -168,7 +171,7 @@ class CastControl(private val context: Context) {
         // device's name included: read it there, never from this worker.
         val name = deviceName ?: onMain { session.castDevice?.friendlyName }
         Log.i(TAG, "session up on '$name', loading the relay stream")
-        val state = load(session, mediaUrl, subtitle, contentType)
+        val state = load(session, mediaUrl, subtitle, file, startAt)
         watch(session)
         return JSONObject().put("deviceName", name ?: JSONObject.NULL).put("playerState", state)
     }
@@ -201,23 +204,41 @@ class CastControl(private val context: Context) {
         watched = c
     }
 
-    fun reload(mediaUrl: String, subtitle: JSONObject?, contentType: String = "video/mp4"): JSONObject {
+    fun reload(mediaUrl: String, subtitle: JSONObject?, file: JSONObject? = null, startAt: Double = 0.0): JSONObject {
         need()
         val session = onMain { CastContext.getSharedInstance(context).sessionManager.currentCastSession }
             ?: throw Refused("Not connected")
-        val state = load(session, mediaUrl, subtitle, contentType)
+        val state = load(session, mediaUrl, subtitle, file, startAt)
         watch(session)
         return JSONObject().put("playerState", state)
     }
 
-    private fun load(session: CastSession, mediaUrl: String, subtitle: JSONObject?, contentType: String): String {
-        val photo = contentType.startsWith("image/")
+    /**
+     * `file` is the relay's description of its file (type and what to show
+     * with it), or null for the stream. A photo is not a stream at all; a
+     * music track is an ordinary buffered file the receiver seeks in itself.
+     */
+    private fun load(session: CastSession, mediaUrl: String, subtitle: JSONObject?,
+                     file: JSONObject?, startAt: Double): String {
+        val contentType = file?.optString("contentType", "") ?: "video/mp4"
+        val photo = file != null && contentType.startsWith("image/")
         val subUrl = subtitle?.optString("url", "")?.takeIf { it.isNotEmpty() }
         val info = if (photo) {
             // A picture, not a stream: nothing to seek, nothing to buffer.
             MediaInfo.Builder(mediaUrl).setContentType(contentType)
                 .setStreamType(MediaInfo.STREAM_TYPE_NONE)
                 .setMetadata(MediaMetadata(MediaMetadata.MEDIA_TYPE_PHOTO)).build()
+        } else if (file != null) {
+            val meta = file.optJSONObject("meta") ?: JSONObject()
+            MediaInfo.Builder(mediaUrl).setContentType(contentType)
+                .setStreamType(MediaInfo.STREAM_TYPE_BUFFERED)
+                .setMetadata(MediaMetadata(MediaMetadata.MEDIA_TYPE_MUSIC_TRACK).apply {
+                    putString(MediaMetadata.KEY_TITLE, meta.optString("title", ""))
+                    putString(MediaMetadata.KEY_ARTIST, meta.optString("artist", ""))
+                    putString(MediaMetadata.KEY_ALBUM_TITLE, meta.optString("album", ""))
+                    meta.optString("cover", "").takeIf { it.isNotEmpty() && it != "null" }
+                        ?.let { addImage(WebImage(Uri.parse(it))) }
+                }).build()
         } else MediaInfo.Builder(mediaUrl)
             .setContentType("video/mp4")
             // LIVE: the relay has no beginning to seek back to — the film's own
@@ -243,6 +264,7 @@ class CastControl(private val context: Context) {
                 }
             }.build()
         val request = MediaLoadRequestData.Builder().setMediaInfo(info).setAutoplay(true)
+            .apply { if (startAt > 0) setCurrentTime((startAt * 1000).toLong()) }
             .apply { if (subUrl != null) setActiveTrackIds(longArrayOf(TEXT_TRACK_ID)) }.build()
         val loaded = CountDownLatch(1)
         var ok = false
@@ -295,6 +317,10 @@ class CastControl(private val context: Context) {
     /** The player as a remote: pause and play the receiver, answered once it has. */
     fun pause(): JSONObject = command { it.pause() }
     fun play(): JSONObject = command { it.play() }
+    /** Where in a track the receiver should be; a film seeks by restarting the relay instead. */
+    fun seek(seconds: Double): JSONObject = command {
+        it.seek(MediaSeekOptions.Builder().setPosition((maxOf(0.0, seconds) * 1000).toLong()).build())
+    }
 
     private fun command(send: (com.google.android.gms.cast.framework.media.RemoteMediaClient) ->
                         com.google.android.gms.common.api.PendingResult<com.google.android.gms.cast.framework.media.RemoteMediaClient.MediaChannelResult>): JSONObject {
diff --git a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastRelay.kt b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastRelay.kt
index 41bf4bd..5b76f60 100644
--- a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastRelay.kt
+++ b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/cast/CastRelay.kt
@@ -82,7 +82,13 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
     private val spoolSeq = AtomicLong()
 
     private class Subtitle(val vtt: ByteArray, val language: String, val label: String)
-    private class Image(val bytes: ByteArray, val type: String)
+    private class Cover(val bytes: ByteArray, val type: String)
+    /** A whole file on disk, served at `/file`: a photo, or a track with its cover. */
+    private class FileSlot(val path: File, val size: Long, val type: String, val cover: Cover?, val meta: JSONObject)
+    private class Incoming(val slot: FileSlot) {
+        val out = java.io.FileOutputStream(slot.path)
+        var received = 0L
+    }
 
     @Volatile private var server: ServerSocket? = null
     @Volatile private var port = 0
@@ -93,8 +99,10 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
     @Volatile private var headerReady = false
     @Volatile private var subtitle: Subtitle? = null
     @Volatile private var subtitleVersion = 0
-    @Volatile private var image: Image? = null
-    @Volatile private var imageVersion = 0
+    @Volatile private var file: FileSlot? = null
+    @Volatile private var fileVersion = 0
+    private var incoming: Incoming? = null       // guarded by this
+    private val fileSeq = AtomicLong()
     /** How many times a receiver asked for the stream since the relay started. */
     @Volatile var streamRequests = 0
         private set
@@ -117,24 +125,74 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
         else "http://${hostPart()}:$port/subs.vtt?t=$token&v=$subtitleVersion"
 
     /** Versioned like the subtitle: a receiver handed the same address twice shows what it has. */
-    val imageUrl get() =
-        if (server == null || image == null) null
-        else "http://${hostPart()}:$port/image?t=$token&v=$imageVersion"
+    val fileUrl get() =
+        if (server == null || file == null) null
+        else "http://${hostPart()}:$port/file?t=$token&v=$fileVersion"
+
+    val fileType get() = file?.type
 
-    val imageType get() = image?.type
+    /** What the receiver is told the file is: title, artist, album, and the cover's address. */
+    fun fileMeta(): JSONObject? = file?.let { f ->
+        JSONObject(f.meta.toString()).put("cover",
+            if (f.cover == null) JSONObject.NULL else "http://${hostPart()}:$port/cover?t=$token&v=$fileVersion")
+    }
 
     /**
-     * One photo, scaled and re-encoded by the page, served at `/image` until
-     * the next one. The relay starts for it when nothing else has.
+     * A file arrives in three steps, so that a large one never crosses the
+     * bridge as one message: `beginFile` names it, `writeFile` appends, and
+     * `endFile` puts it up and answers its address. It is written to the spool
+     * directory rather than held: a long lossless track is a few hundred
+     * megabytes. The relay starts for it when nothing else has.
      */
     @Synchronized
-    fun showImage(bytes: ByteArray, type: String): JSONObject {
-        if (type !in IMAGE_TYPES) throw IllegalArgumentException("Not a picture a receiver shows: $type")
+    fun beginFile(type: String, size: Long, cover: ByteArray?, coverType: String?, meta: JSONObject): Boolean {
+        if (type !in FILE_TYPES) throw IllegalArgumentException("Not something a receiver shows: $type")
+        if (size <= 0 || size > FILE_MAX_BYTES) throw IllegalArgumentException("Bad file size: $size")
+        if (cover != null && (coverType == null || !coverType.startsWith("image/") || coverType !in FILE_TYPES)) {
+            throw IllegalArgumentException("Bad cover type: $coverType")
+        }
         if (server == null) start(null, null)
-        image = Image(bytes, type)
-        imageVersion++
-        log("image set: ${bytes.size} bytes, $type, v$imageVersion")
-        return JSONObject().put("url", imageUrl)
+        dropIncoming()
+        // At most the file being shown and the one arriving: anything older
+        // has been replaced on the television already.
+        spoolDir.listFiles()?.filter { it.name.startsWith("file-") && it != file?.path }?.forEach { it.delete() }
+        val text = { k: String -> meta.optString(k, "").take(500) }
+        val slot = FileSlot(File(spoolDir, "file-${fileSeq.incrementAndGet()}.bin"), size, type,
+            cover?.let { Cover(it, coverType!!) },
+            JSONObject().put("title", text("title")).put("artist", text("artist")).put("album", text("album")))
+        incoming = Incoming(slot)
+        return true
+    }
+
+    @Synchronized
+    fun writeFile(data: ByteArray, offset: Int = 0, length: Int = data.size - offset): Boolean {
+        val f = incoming ?: throw IllegalStateException("No file is being sent")
+        if (f.received + length > f.slot.size) { dropIncoming(); throw IllegalStateException("More bytes than announced") }
+        f.out.write(data, offset, length)
+        f.received += length
+        return true
+    }
+
+    @Synchronized
+    fun endFile(): JSONObject {
+        val f = incoming ?: throw IllegalStateException("No file is being sent")
+        incoming = null
+        f.out.close()
+        if (f.received != f.slot.size) {
+            f.slot.path.delete()
+            throw IllegalStateException("File cut short: ${f.received} of ${f.slot.size} bytes")
+        }
+        // The previous file stays on disk until the next one begins: a receiver
+        // may still be reading it.
+        file = f.slot
+        fileVersion++
+        log("file set: ${f.slot.size} bytes, ${f.slot.type}, v$fileVersion")
+        return JSONObject().put("url", fileUrl)
+    }
+
+    private fun dropIncoming() {
+        incoming?.let { try { it.out.close() } catch (e: Exception) {}; it.slot.path.delete() }
+        incoming = null
     }
 
     fun subtitleInfo(): JSONObject? = subtitle?.let {
@@ -169,7 +227,8 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
         spoolDir.mkdirs()
         spoolDir.listFiles()?.forEach { it.delete() }
         subtitle = null
-        image = null
+        dropIncoming()
+        file = null
         setSubtitle(sub)
 
         var bound: ServerSocket? = null
@@ -276,7 +335,10 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
         clients.clear()
         server?.let { try { it.close() } catch (e: Exception) {} }
         server = null
-        port = 0; token = null; initSegment = null; subtitle = null; image = null
+        port = 0; token = null; initSegment = null; subtitle = null
+        dropIncoming()
+        file = null
+        spoolDir.listFiles()?.filter { it.name.startsWith("file-") }?.forEach { it.delete() }
         synchronized(ring) { ring.clear(); ringBytes = 0 }
         accum.reset()
     }
@@ -295,7 +357,12 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
             socket.soTimeout = 15000
             val reader = BufferedReader(InputStreamReader(socket.getInputStream(), Charsets.ISO_8859_1))
             val requestLine = reader.readLine() ?: return socket.close()
-            while (true) { val line = reader.readLine() ?: break; if (line.isEmpty()) break }
+            var range: String? = null
+            while (true) {
+                val line = reader.readLine() ?: break
+                if (line.isEmpty()) break
+                if (line.startsWith("range:", ignoreCase = true)) range = line.substringAfter(':').trim()
+            }
             socket.soTimeout = 0
             val parts = requestLine.split(' ')
             val method = parts.getOrElse(0) { "" }
@@ -316,7 +383,8 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
             if (token == null || query["t"] != token) return respond(out, socket, 403, emptyMap())
             when (path) {
                 "/subs.vtt" -> serveSubtitle(out, socket)
-                "/image" -> serveImage(out, socket)
+                "/file" -> serveFile(out, socket, range)
+                "/cover" -> serveCover(out, socket)
                 "/stream.mp4" -> { streamRequests++; serveStream(out, socket) }
                 else -> respond(out, socket, 404, emptyMap())
             }
@@ -334,13 +402,52 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
         ), sub.vtt)
     }
 
-    private fun serveImage(out: OutputStream, socket: Socket) {
-        val img = image ?: return respond(out, socket, 404, CORS_HEADERS)
+    /** The whole file, or the one range asked for: a receiver seeks in a track that way. */
+    private fun serveFile(out: OutputStream, socket: Socket, range: String?) {
+        val f = file ?: return respond(out, socket, 404, CORS_HEADERS)
+        val total = f.size
+        val base = CORS_HEADERS + mapOf("Content-Type" to f.type, "Cache-Control" to "no-store",
+                                        "Accept-Ranges" to "bytes", "Connection" to "close")
+        var from = 0L
+        var to = total - 1
+        var status = 200
+        val m = range?.let { Regex("^bytes=(\\d*)-(\\d*)$").matchEntire(it) }
+        if (m != null && (m.groupValues[1].isNotEmpty() || m.groupValues[2].isNotEmpty())) {
+            val a = m.groupValues[1]; val b = m.groupValues[2]
+            from = if (a.isEmpty()) total - b.toLong() else a.toLong()
+            to = if (a.isEmpty() || b.isEmpty()) total - 1 else minOf(b.toLong(), total - 1)
+            from = maxOf(0L, from)
+            if (from > to || from >= total) {
+                head(out, 416, base + ("Content-Range" to "bytes */$total") + ("Content-Length" to "0"))
+                out.flush(); socket.close(); return
+            }
+            status = 206
+        }
+        val length = to - from + 1
+        head(out, status, base + ("Content-Length" to length.toString()) +
+            (if (status == 206) mapOf("Content-Range" to "bytes $from-$to/$total") else emptyMap()))
+        RandomAccessFile(f.path, "r").use { raf ->
+            raf.seek(from)
+            val block = ByteArray(BLOCK)
+            var left = length
+            while (left > 0) {
+                val n = raf.read(block, 0, minOf(BLOCK.toLong(), left).toInt())
+                if (n <= 0) break
+                out.write(block, 0, n)
+                left -= n
+            }
+        }
+        out.flush()
+        socket.close()
+    }
+
+    private fun serveCover(out: OutputStream, socket: Socket) {
+        val c = file?.cover ?: return respond(out, socket, 404, CORS_HEADERS)
         respond(out, socket, 200, CORS_HEADERS + mapOf(
-            "Content-Type" to img.type,
-            "Content-Length" to img.bytes.size.toString(),
+            "Content-Type" to c.type,
+            "Content-Length" to c.bytes.size.toString(),
             "Cache-Control" to "no-store",
-        ), img.bytes)
+        ), c.bytes)
     }
 
     private fun serveStream(out: OutputStream, socket: Socket) {
@@ -428,8 +535,13 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
         }
 
         const val RING_CAP = 64
-        // The page re-encodes every photo to JPEG: a guard, not a menu.
-        val IMAGE_TYPES = setOf("image/jpeg", "image/png", "image/webp")
+        // What a receiver is ever handed as a file: the page re-encodes every
+        // photo to JPEG, and plays a track in the format it is stored in.
+        val FILE_TYPES = setOf("image/jpeg", "image/png", "image/webp",
+            "audio/mpeg", "audio/mp4", "audio/aac", "audio/flac", "audio/ogg", "audio/opus",
+            "audio/wav", "audio/webm")
+        // Only stops a page from filling the phone: a long lossless track is a few hundred MB.
+        const val FILE_MAX_BYTES = 1024L * 1024 * 1024
         const val RING_MAX_BYTES = 32L * 1024 * 1024
         const val SPOOL_MAX_BYTES = 2L * 1024 * 1024 * 1024
         private const val HEADER_WAIT_MS = 10_000L
@@ -450,8 +562,9 @@ class CastRelay(private val lanAddress: () -> InetAddress?, private val spoolDir
             "Access-Control-Expose-Headers" to "Content-Length, Content-Range",
         )
 
-        private val REASONS = mapOf(200 to "OK", 204 to "No Content", 403 to "Forbidden",
-                                    404 to "Not Found", 405 to "Method Not Allowed")
+        private val REASONS = mapOf(200 to "OK", 204 to "No Content", 206 to "Partial Content",
+                                    403 to "Forbidden", 404 to "Not Found", 405 to "Method Not Allowed",
+                                    416 to "Range Not Satisfiable")
 
         private fun randomToken(): String {
             val b = ByteArray(16).also { SecureRandom().nextBytes(it) }
diff --git a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/save/SaveNames.kt b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/save/SaveNames.kt
index 2414730..40250c7 100644
--- a/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/save/SaveNames.kt
+++ b/packages/meshbay-android/app/src/main/kotlin/org/meshbay/client/save/SaveNames.kt
@@ -59,6 +59,7 @@ class BinaryFrame(val id: Long, val channel: Int, val handle: Long, val bytes: B
         const val HEADER = 16
         const val SAVE_WRITE = 1
         const val CAST_PUSH = 2
+        const val CAST_FILE = 3
         private val MAGIC = byteArrayOf('M'.code.toByte(), 'B'.code.toByte(), 'B'.code.toByte(), '1'.code.toByte())
 
         private fun u32(b: ByteArray, at: Int) =
diff --git a/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
index 8013e29..14f49cf 100644
--- a/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
+++ b/packages/meshbay-android/app/src/test/kotlin/org/meshbay/client/CastRelayTest.kt
@@ -158,9 +158,38 @@ class CastRelayTest {
         assertEquals(200, get(r.getString("url"), readBytes = 0).status)
     }
 
-    @Test fun `a photo starts the relay and is served behind the token, re-addressed when it changes`() {
+    private fun send(bytes: ByteArray, type: String, meta: JSONObject = JSONObject(),
+                     cover: ByteArray? = null): String {
+        relay.beginFile(type, bytes.size.toLong(), cover, cover?.let { "image/jpeg" }, meta)
+        var at = 0
+        while (at < bytes.size) { val n = minOf(3, bytes.size - at); relay.writeFile(bytes, at, n); at += n }
+        return relay.endFile().getString("url")
+    }
+
+    private fun getRange(url: String, range: String): Reply {
+        val u = java.net.URI(url)
+        Socket(u.host, u.port).use { s ->
+            s.soTimeout = 5000
+            s.getOutputStream().write("GET ${u.rawPath}?${u.rawQuery} HTTP/1.1\r\nHost: x\r\nRange: $range\r\n\r\n".toByteArray())
+            val input = DataInputStream(s.getInputStream())
+            val lines = ArrayList<String>()
+            val line = StringBuilder()
+            while (true) {
+                val c = input.read()
+                if (c == -1) break
+                if (c == '\n'.code) { val l = line.toString().trimEnd('\r'); if (l.isEmpty()) break; lines.add(l); line.clear() }
+                else line.append(c.toChar())
+            }
+            val headers = lines.drop(1).associate { it.substringBefore(':').lowercase() to it.substringAfter(':').trim() }
+            val body = ByteArray(headers["content-length"]?.toInt() ?: 0)
+            input.readFully(body)
+            return Reply(lines[0].split(' ')[1].toInt(), headers, body)
+        }
+    }
+
+    @Test fun `a file starts the relay and is served behind the token, re-addressed when it changes`() {
         val jpeg = byteArrayOf(0xFF.toByte(), 0xD8.toByte(), 1, 2, 3, 0xFF.toByte(), 0xD9.toByte())
-        val first = relay.showImage(jpeg, "image/jpeg").getString("url")
+        val first = send(jpeg, "image/jpeg")
         assertTrue(relay.active)
         val reply = get(first)
         assertEquals(200, reply.status)
@@ -169,21 +198,42 @@ class CastRelayTest {
         assertArrayEquals(jpeg, reply.body)
         assertEquals(403, get(first.replace(Regex("t=[0-9a-f]+"), "t=x")).status)
         // A receiver handed the same address twice shows what it already has.
-        val second = relay.showImage(byteArrayOf(9), "image/jpeg").getString("url")
+        val second = send(byteArrayOf(9), "image/jpeg")
         assertNotEquals(first, second)
         assertArrayEquals(byteArrayOf(9), get(second).body)
     }
 
-    @Test fun `only a picture is served as one`() {
-        val refused = try { relay.showImage(byteArrayOf(1), "text/html"); false } catch (e: IllegalArgumentException) { true }
+    @Test fun `a track is served with its cover, and by range`() {
+        val track = ByteArray(20) { it.toByte() }
+        val cover = byteArrayOf(0xFF.toByte(), 0xD8.toByte(), 7)
+        val url = send(track, "audio/flac", JSONObject().put("title", "A Song").put("artist", "Some Band"), cover)
+        assertEquals("audio/flac", relay.fileType)
+        val meta = relay.fileMeta()!!
+        assertEquals("A Song", meta.getString("title"))
+        assertArrayEquals(cover, get(meta.getString("cover")).body)
+        val part = getRange(url, "bytes=5-9")
+        assertEquals(206, part.status)
+        assertEquals("bytes 5-9/20", part.headers["content-range"])
+        assertArrayEquals(track.copyOfRange(5, 10), part.body)
+        assertArrayEquals(track.copyOfRange(15, 20), getRange(url, "bytes=15-").body)
+        assertEquals(416, getRange(url, "bytes=50-60").status)
+    }
+
+    @Test fun `only a whole picture or sound is served as one`() {
+        val refused = try { relay.beginFile("text/html", 1, null, null, JSONObject()); false } catch (e: IllegalArgumentException) { true }
         assertTrue(refused)
-        assertNull(relay.imageUrl)
+        assertNull(relay.fileUrl)
+        relay.beginFile("audio/mpeg", 10, null, null, JSONObject())
+        relay.writeFile(byteArrayOf(1, 2, 3))
+        val short = try { relay.endFile(); false } catch (e: IllegalStateException) { true }
+        assertTrue(short)
+        assertNull(relay.fileUrl)
     }
 
-    @Test fun `a film started over a photo takes the photo down`() {
-        relay.showImage(byteArrayOf(1), "image/jpeg")
+    @Test fun `a film started over a file takes the file down`() {
+        send(byteArrayOf(1), "image/jpeg")
         relay.start(null, null)
-        assertNull(relay.imageUrl)
+        assertNull(relay.fileUrl)
     }
 
     @Test fun `the preflight is answered before the token is checked`() {
diff --git a/packages/meshbay-client/src/cast-chromecast.js b/packages/meshbay-client/src/cast-chromecast.js
index 4c8ddf0..8c6c9c6 100644
--- a/packages/meshbay-client/src/cast-chromecast.js
+++ b/packages/meshbay-client/src/cast-chromecast.js
@@ -42,17 +42,30 @@ const TEXT_TRACK_STYLE = Object.freeze({
 
 /**
  * What to hand `player.load()` for a stream, with or without subtitles, or
- * for a photo.
+ * for a whole file the relay serves.
  *
  * `streamType: 'LIVE'` because the relay has no beginning to seek back to —
  * the film's own timeline lives on this side, and a seek restarts the relay.
- * A photo is not a stream at all.
+ * A file is the relay's to describe (`file`: its type and what to show with
+ * it), never the page's: a photo is not a stream at all, and a music track is
+ * an ordinary buffered file the receiver seeks in itself.
  */
-function mediaFor(mediaUrl, subtitle, contentType) {
-  if (contentType && contentType.startsWith('image/')) {
-    return { contentId: mediaUrl, contentType, streamType: 'NONE',
+function mediaFor(mediaUrl, subtitle, file) {
+  if (file && file.contentType.startsWith('image/')) {
+    return { contentId: mediaUrl, contentType: file.contentType, streamType: 'NONE',
              metadata: { metadataType: 4 } };   // PhotoMediaMetadata
   }
+  if (file) {
+    const meta = file.meta || {};
+    return {
+      contentId: mediaUrl, contentType: file.contentType, streamType: 'BUFFERED',
+      metadata: {
+        metadataType: 3,                         // MusicTrackMediaMetadata
+        title: meta.title || '', artist: meta.artist || '', albumName: meta.album || '',
+        images: meta.cover ? [{ url: meta.cover }] : [],
+      },
+    };
+  }
   const media = {
     contentId: mediaUrl,
     contentType: 'video/mp4',
@@ -73,11 +86,14 @@ function mediaFor(mediaUrl, subtitle, contentType) {
   return media;
 }
 
-function loadOptionsFor(subtitle) {
-  return {
+function loadOptionsFor(subtitle, startAt) {
+  const options = {
     autoplay: true,
     activeTrackIds: subtitle && subtitle.url ? [TEXT_TRACK_ID] : [],
   };
+  // Where in a track to begin: a cast started mid-song carries on from there.
+  if (startAt > 0) options.currentTime = startAt;
+  return options;
 }
 
 class CastChromecast {
@@ -145,7 +161,7 @@ class CastChromecast {
     }
   }
 
-  async connect(deviceId, mediaUrl, subtitle, contentType) {
+  async connect(deviceId, mediaUrl, subtitle, file, startAt) {
     const device = this._devices.get(deviceId);
     if (!device) throw new Error(`Unknown device: ${deviceId}`);
 
@@ -185,7 +201,7 @@ class CastChromecast {
 
     debug(`[cast-chromecast] loading with ${subtitle?.url ? 'subtitles' : 'no subtitles'}`);
     const status = await new Promise((resolve, reject) => {
-      player.load(mediaFor(mediaUrl, subtitle, contentType), loadOptionsFor(subtitle),
+      player.load(mediaFor(mediaUrl, subtitle, file), loadOptionsFor(subtitle, startAt),
         (err, s) => {
           if (err) return reject(err);
           resolve(s);
@@ -197,12 +213,12 @@ class CastChromecast {
     return { deviceName: device.name, playerState: status.playerState };
   }
 
-  async reload(mediaUrl, subtitle, contentType) {
+  async reload(mediaUrl, subtitle, file, startAt) {
     if (!this._player) throw new Error('Not connected');
     debug(`[cast-chromecast] reloading stream on "${this._connectedDevice?.name}"`
       + ` with ${subtitle?.url ? 'subtitles' : 'no subtitles'}`);
     const status = await new Promise((resolve, reject) => {
-      this._player.load(mediaFor(mediaUrl, subtitle, contentType), loadOptionsFor(subtitle),
+      this._player.load(mediaFor(mediaUrl, subtitle, file), loadOptionsFor(subtitle, startAt),
         (err, s) => {
           if (err) return reject(err);
           resolve(s);
@@ -256,6 +272,16 @@ class CastChromecast {
     return { playerState: status && status.playerState };
   }
 
+  /** Where in a track the receiver should be; a film seeks by restarting the relay instead. */
+  async seek(seconds) {
+    if (!this._player) throw new Error('Not connected');
+    const status = await new Promise((resolve, reject) => {
+      this._player.seek(Math.max(0, Number(seconds) || 0), (err, s) => (err ? reject(err) : resolve(s)));
+    });
+    this._noteStatus(status);
+    return { playerState: status && status.playerState };
+  }
+
   async play() {
     if (!this._player) throw new Error('Not connected');
     const status = await new Promise((resolve, reject) => {
diff --git a/packages/meshbay-client/src/cast-relay.js b/packages/meshbay-client/src/cast-relay.js
index c5eadc7..ed20b33 100644
--- a/packages/meshbay-client/src/cast-relay.js
+++ b/packages/meshbay-client/src/cast-relay.js
@@ -15,9 +15,11 @@
  * a media element, so unlike the stream it needs CORS headers to be readable
  * at all.
  *
- * A photo is served at `/image`, one at a time: the page decrypts it, scales
- * it to the television and hands it here, and the receiver loads it as a
- * picture. The relay starts for it when it is not already running.
+ * A whole file — a photo, or a music track with its cover at `/cover` — is
+ * served at `/file`, one at a time: the page decrypts it and hands it over in
+ * pieces (begin, writes, end), and the receiver loads it as a picture or as
+ * music. Ranges are honoured there, which is what a receiver seeks with. The
+ * relay starts for a file when it is not already running.
  *
  * Mitigations:
  *   · Bind to the LAN interface, never 0.0.0.0
@@ -56,7 +58,14 @@ const debug = util.debuglog('cast-relay');
 const RING_CAP = 64;
 // What the receiver is ever told a photo is. The page re-encodes every photo
 // to JPEG, so this list is a guard, not a menu.
-const IMAGE_TYPES = new Set(['image/jpeg', 'image/png', 'image/webp']);
+const FILE_TYPES = new Set([
+  'image/jpeg', 'image/png', 'image/webp',
+  'audio/mpeg', 'audio/mp4', 'audio/aac', 'audio/flac', 'audio/ogg', 'audio/opus',
+  'audio/wav', 'audio/webm',
+]);
+// A track is a few megabytes, a long lossless one a few hundred; this only
+// stops a page from filling the machine's memory.
+const FILE_MAX_BYTES = 1024 * 1024 * 1024;
 const BACKPRESSURE_HIGH = 8 * 1024 * 1024;
 const MOOF = 0x6d6f6f66;
 const PORT_BASE = 19550;
@@ -170,8 +179,9 @@ class CastRelay {
     this._bytesSent = 0;
     this._subtitle = null;
     this._subtitleVersion = 0;
-    this._image = null;
-    this._imageVersion = 0;
+    this._file = null;
+    this._fileVersion = 0;
+    this._incoming = null;
   }
 
   get active() { return this._server !== null; }
@@ -195,26 +205,67 @@ class CastRelay {
   }
 
   /**
-   * Where the current photo can be fetched, or null when there is none.
+   * Where the current file can be fetched, or null when there is none.
    * Versioned for the same reason as the subtitle: a receiver handed the same
    * address twice shows what it already has.
    */
-  get imageUrl() {
-    if (!this._server || !this._image) return null;
-    return `http://${this._lanIP}:${this._port}/image`
-      + `?t=${this._token}&v=${this._imageVersion}`;
+  get fileUrl() {
+    if (!this._server || !this._file) return null;
+    return `http://${this._lanIP}:${this._port}/file`
+      + `?t=${this._token}&v=${this._fileVersion}`;
   }
 
-  get imageType() { return this._image ? this._image.type : null; }
+  get fileType() { return this._file ? this._file.type : null; }
 
-  /** Serve one photo, starting the relay if nothing else has. */
-  async showImage({ bytes, type }) {
-    if (!IMAGE_TYPES.has(type)) throw new Error(`Not a picture a receiver shows: ${type}`);
+  /** What the receiver is told the file is: title, artist, album, cover. */
+  get fileMeta() {
+    if (!this._file) return null;
+    const { title, artist, album } = this._file.meta;
+    const cover = this._file.cover
+      ? `http://${this._lanIP}:${this._port}/cover?t=${this._token}&v=${this._fileVersion}`
+      : null;
+    return { title, artist, album, cover };
+  }
+
+  /**
+   * A file arrives in three steps, so that a large one never has to cross in
+   * a single message: `beginFile` names it, `writeFile` appends, `endFile`
+   * puts it up and answers its address. The relay starts if nothing has.
+   */
+  async beginFile({ type, size, cover, title, artist, album }) {
+    if (!FILE_TYPES.has(type)) throw new Error(`Not something a receiver shows: ${type}`);
+    if (!(size > 0 && size <= FILE_MAX_BYTES)) throw new Error(`Bad file size: ${size}`);
+    if (cover && !FILE_TYPES.has(cover.type)) throw new Error(`Bad cover type: ${cover.type}`);
     if (!this._server) await this.start({});
-    this._image = { bytes: Buffer.from(bytes), type };
-    this._imageVersion++;
-    debug(`[cast-relay] image set: ${this._image.bytes.length} bytes, ${type}, v${this._imageVersion}`);
-    return { url: this.imageUrl };
+    const text = (v) => (typeof v === 'string' ? v.slice(0, 500) : '');
+    this._incoming = {
+      type, size, parts: [], received: 0,
+      cover: cover && cover.type.startsWith('image/')
+        ? { bytes: Buffer.from(cover.bytes), type: cover.type } : null,
+      meta: { title: text(title), artist: text(artist), album: text(album) },
+    };
+    return true;
+  }
+
+  writeFile(bytes) {
+    const f = this._incoming;
+    if (!f) throw new Error('No file is being sent');
+    const buf = Buffer.from(bytes);
+    if (f.received + buf.length > f.size) throw new Error('More bytes than announced');
+    f.parts.push(buf);
+    f.received += buf.length;
+    return true;
+  }
+
+  endFile() {
+    const f = this._incoming;
+    this._incoming = null;
+    if (!f) throw new Error('No file is being sent');
+    if (f.received !== f.size) throw new Error(`File cut short: ${f.received} of ${f.size} bytes`);
+    this._file = { bytes: Buffer.concat(f.parts), type: f.type, cover: f.cover, meta: f.meta };
+    this._fileVersion++;
+    debug(`[cast-relay] file set: ${f.size} bytes, ${f.type}, v${this._fileVersion}`);
+    return { url: this.fileUrl };
   }
 
   get subtitle() {
@@ -264,7 +315,8 @@ class CastRelay {
     this._chunkCount = 0;
     this._bytesSent = 0;
     this._subtitle = null;
-    this._image = null;
+    this._file = null;
+    this._incoming = null;
     this.setSubtitle(subtitle);
 
     const server = http.createServer((req, res) => this._handle(req, res));
@@ -356,7 +408,8 @@ class CastRelay {
     this._token = null;
     this._initSegment = null;
     this._subtitle = null;
-    this._image = null;
+    this._file = null;
+    this._incoming = null;
     this._ring = [];
     this._accum.reset();
     this._fragCount = 0;
@@ -400,8 +453,13 @@ class CastRelay {
       return;
     }
 
-    if (url.pathname === '/image') {
-      this._handleImage(res);
+    if (url.pathname === '/file') {
+      this._handleFile(req, res);
+      return;
+    }
+
+    if (url.pathname === '/cover') {
+      this._handleCover(res);
       return;
     }
 
@@ -459,20 +517,58 @@ class CastRelay {
     debug(`[cast-relay] subtitle served: ${this._subtitle.vtt.length} bytes`);
   }
 
-  _handleImage(res) {
-    if (!this._image) {
+  /**
+   * The whole file, or the one range asked for: a receiver seeks in a track
+   * by asking for the bytes from there on.
+   */
+  _handleFile(req, res) {
+    const f = this._file;
+    if (!f) {
+      res.writeHead(404, CORS_HEADERS);
+      res.end();
+      return;
+    }
+    const total = f.bytes.length;
+    const base = {
+      ...CORS_HEADERS,
+      'Content-Type': f.type,
+      'Cache-Control': 'no-store',
+      'Accept-Ranges': 'bytes',
+    };
+    const m = /^bytes=(\d*)-(\d*)$/.exec(req.headers.range || '');
+    if (m && (m[1] !== '' || m[2] !== '')) {
+      let from = m[1] === '' ? total - Number(m[2]) : Number(m[1]);
+      let to = m[1] === '' || m[2] === '' ? total - 1 : Math.min(Number(m[2]), total - 1);
+      from = Math.max(0, from);
+      if (from > to || from >= total) {
+        res.writeHead(416, { ...base, 'Content-Range': `bytes */${total}` });
+        res.end();
+        return;
+      }
+      res.writeHead(206, { ...base, 'Content-Range': `bytes ${from}-${to}/${total}`,
+                           'Content-Length': to - from + 1 });
+      res.end(f.bytes.subarray(from, to + 1));
+      return;
+    }
+    res.writeHead(200, { ...base, 'Content-Length': total });
+    res.end(f.bytes);
+    debug(`[cast-relay] file served: ${total} bytes`);
+  }
+
+  _handleCover(res) {
+    const c = this._file && this._file.cover;
+    if (!c) {
       res.writeHead(404, CORS_HEADERS);
       res.end();
       return;
     }
     res.writeHead(200, {
       ...CORS_HEADERS,
-      'Content-Type': this._image.type,
-      'Content-Length': this._image.bytes.length,
+      'Content-Type': c.type,
+      'Content-Length': c.bytes.length,
       'Cache-Control': 'no-store',
     });
-    res.end(this._image.bytes);
-    debug(`[cast-relay] image served: ${this._image.bytes.length} bytes`);
+    res.end(c.bytes);
   }
 }
 
diff --git a/packages/meshbay-client/src/main.js b/packages/meshbay-client/src/main.js
index 1c371f5..a2a7a86 100644
--- a/packages/meshbay-client/src/main.js
+++ b/packages/meshbay-client/src/main.js
@@ -2333,29 +2333,31 @@ function registerBridge() {
 
   handle('cast:devices', async () => castChromecast.devices());
 
-  // One photo at a time, scaled and re-encoded by the page.
-  handle('cast:image', async (_e, img) => {
-    return castRelay.showImage({ bytes: Buffer.from(img.bytes), type: img.type });
-  });
+  // A whole file for the receiver — a photo, a music track — in three steps,
+  // so that a large one never crosses in a single message.
+  handle('cast:file:begin', async (_e, f) => castRelay.beginFile(f || {}));
+  handle('cast:file:write', async (_e, data) => castRelay.writeFile(Buffer.from(data)));
+  handle('cast:file:end', async () => castRelay.endFile());
 
-  // The relay's photo is loaded as a picture, anything else as the stream;
-  // the page does not get to say which.
+  // The relay's file is loaded as what the relay says it is, anything else as
+  // the stream; the page does not get to say which.
   const loadOf = (mediaUrl, subtitle) => (
-    mediaUrl && mediaUrl === castRelay.imageUrl
-      ? { subtitle: null, contentType: castRelay.imageType }
-      : { subtitle: subtitle === undefined ? castRelay.subtitle : subtitle,
-          contentType: 'video/mp4' });
+    mediaUrl && mediaUrl === castRelay.fileUrl
+      ? { subtitle: null, file: { contentType: castRelay.fileType, meta: castRelay.fileMeta } }
+      : { subtitle: subtitle === undefined ? castRelay.subtitle : subtitle, file: null });
 
-  handle('cast:chromecast:connect', async (_e, { deviceId, mediaUrl, subtitle }) => {
+  handle('cast:chromecast:connect', async (_e, { deviceId, mediaUrl, subtitle, startAt }) => {
     const l = loadOf(mediaUrl, subtitle);
-    return castChromecast.connect(deviceId, mediaUrl, l.subtitle, l.contentType);
+    return castChromecast.connect(deviceId, mediaUrl, l.subtitle, l.file, l.file ? startAt : 0);
   });
 
-  handle('cast:chromecast:reload', async (_e, { mediaUrl, subtitle }) => {
+  handle('cast:chromecast:reload', async (_e, { mediaUrl, subtitle, startAt }) => {
     const l = loadOf(mediaUrl, subtitle);
-    return castChromecast.reload(mediaUrl, l.subtitle, l.contentType);
+    return castChromecast.reload(mediaUrl, l.subtitle, l.file, l.file ? startAt : 0);
   });
 
+  handle('cast:chromecast:seek', async (_e, seconds) => castChromecast.seek(seconds));
+
   // The player becomes a remote while casting: these drive the receiver.
   handle('cast:chromecast:pause', async () => castChromecast.pause());
   handle('cast:chromecast:play', async () => castChromecast.play());
diff --git a/packages/meshbay-client/src/preload.js b/packages/meshbay-client/src/preload.js
index f12d68e..0de76db 100644
--- a/packages/meshbay-client/src/preload.js
+++ b/packages/meshbay-client/src/preload.js
@@ -178,7 +178,18 @@ contextBridge.exposeInMainWorld('meshbay', {
     push: (data) => ipcRenderer.invoke('cast:push', data),
     stop: () => ipcRenderer.invoke('cast:stop'),
     subtitle: (sub) => ipcRenderer.invoke('cast:subtitle', sub),
-    image: (img) => ipcRenderer.invoke('cast:image', img),
+    // A file in pieces of a few megabytes, as the Android bridge sends it.
+    file: async (f) => {
+      const bytes = f.bytes;
+      await ipcRenderer.invoke('cast:file:begin', {
+        type: f.type, size: bytes.length, cover: f.cover || null,
+        title: f.title, artist: f.artist, album: f.album,
+      });
+      for (let at = 0; at < bytes.length; at += 4 * 1024 * 1024) {
+        await ipcRenderer.invoke('cast:file:write', bytes.subarray(at, at + 4 * 1024 * 1024));
+      }
+      return ipcRenderer.invoke('cast:file:end');
+    },
     finish: () => ipcRenderer.invoke('cast:finish'),
     status: () => ipcRenderer.invoke('cast:status'),
     scan: () => ipcRenderer.invoke('cast:scan'),
@@ -188,6 +199,7 @@ contextBridge.exposeInMainWorld('meshbay', {
     chromecastDisconnect: () => ipcRenderer.invoke('cast:chromecast:disconnect'),
     chromecastPause: () => ipcRenderer.invoke('cast:chromecast:pause'),
     chromecastPlay: () => ipcRenderer.invoke('cast:chromecast:play'),
+    chromecastSeek: (seconds) => ipcRenderer.invoke('cast:chromecast:seek', seconds),
   },
 
   // A sink that writes to disk as chunks arrive, never a buffer handed over at
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/cast-session.js b/packages/meshbay-hub/src/meshbay_hub/static/cast-session.js
index 007722c..9f93919 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/cast-session.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/cast-session.js
@@ -11,10 +11,14 @@ import * as platform from './platform.js';
 // in the lightbox is shown there. In memory only: a television chosen
 // yesterday may be off today, and choosing it again is one tap.
 //
-// The receiver is the default media receiver, which shows a film or a
-// picture and nothing else; the interface itself stays on this device.
+// The receiver is the default media receiver, which shows one film, one
+// picture or one track at a time and nothing else; the interface itself stays
+// on this device. `owner` says which of the three the television is showing
+// now ('video', 'photo', 'music'), so that the music bar stops treating the
+// receiver as its own once a film or a photo has taken it.
 
 let current = null;
+let owner = null;
 const listeners = new Set();
 
 function notify() {
@@ -23,7 +27,15 @@ function notify() {
 
 export const castSession = {
   get device() { return current; },
+  get owner() { return owner; },
   get supported() { return Boolean(platform.capabilities.lanCast && platform.cast.available); },
+  /** Whether a whole file (a photo, a track) can be sent: an older shell cannot. */
+  get canSendFiles() { return this.supported && platform.cast.canSendFiles; },
+  /** The television now shows what `who` sends it. */
+  claim(who) {
+    owner = who;
+    notify();
+  },
   choose(device) {
     current = device ? { id: device.id, name: device.name } : null;
     notify();
@@ -32,6 +44,7 @@ export const castSession = {
   forget() { this.choose(null); },
   /** Stop casting: the television goes back to its idle screen. */
   async end() {
+    owner = null;
     this.choose(null);
     photoGen++;
     await platform.cast.chromecastDisconnect().catch(() => {});
@@ -49,6 +62,27 @@ export function useCastDevice() {
   return device;
 }
 
+// ── A file on the television ─────────────────────────────────────────────────
+//
+// A photo or a music track, whole, handed to the relay and loaded on the
+// session's television — connected if it is not yet, reloaded if it is. The
+// relay, not the page, tells the receiver what the file is; the page only
+// names it (title, artist, album, cover) and says where in it to begin.
+
+export async function loadFile({ owner: who, startAt = 0, ...file }) {
+  const device = current;
+  if (!device || !castSession.canSendFiles) throw new Error('No television to cast to');
+  castSession.claim(who);
+  const sent = await platform.cast.file(file);
+  if (!sent) throw new Error('The cast relay did not take the file');
+  const status = await platform.cast.status();
+  if (status && status.chromecast && status.chromecast.connected) {
+    await platform.cast.chromecastReload({ mediaUrl: sent.url, startAt });
+  } else {
+    await platform.cast.chromecastConnect({ deviceId: device.id, mediaUrl: sent.url, startAt });
+  }
+}
+
 // ── A photo on the television ────────────────────────────────────────────────
 //
 // Scaled to fit 1920×1080 and re-encoded as JPEG before it leaves: a camera's
@@ -87,18 +121,10 @@ let photoChain = Promise.resolve();
 export function showPhoto(blob) {
   const gen = ++photoGen;
   photoChain = photoChain.then(async () => {
-    const device = current;
-    if (gen !== photoGen || !device || !platform.cast.canShowImages) return;
+    if (gen !== photoGen || !current || !castSession.canSendFiles) return;
     const bytes = await scaledForTv(blob);
     if (gen !== photoGen) return;
-    const shown = await platform.cast.image({ bytes, type: 'image/jpeg' });
-    if (!shown || gen !== photoGen) return;
-    const status = await platform.cast.status();
-    if (status && status.chromecast && status.chromecast.connected) {
-      await platform.cast.chromecastReload({ mediaUrl: shown.url });
-    } else {
-      await platform.cast.chromecastConnect({ deviceId: device.id, mediaUrl: shown.url });
-    }
+    await loadFile({ owner: 'photo', bytes, type: 'image/jpeg' });
   }).catch((err) => console.warn('[cast] photo not shown:', err));
   return photoChain;
 }
@@ -111,9 +137,12 @@ export function showPhoto(blob) {
 // toolbar. `cls` and `iconCls` are the button's and its icon's own classes,
 // so it matches its neighbours.
 // `onChosen` runs after a television is picked, for the view that has
-// something to show on it straight away.
+// something to show on it straight away. `up` opens the menu above the
+// button, for one at the bottom of the window.
 
-export function CastButton({ variant = 'page', cls = 'tb-btn tb-btn-icon', iconCls = '', onChosen }) {
+export function CastButton({
+  variant = 'page', cls = 'tb-btn tb-btn-icon', iconCls = '', onChosen, up = false,
+}) {
   const device = useCastDevice();
   const [open, setOpen] = useState(false);
   const [devices, setDevices] = useState([]);
@@ -143,7 +172,7 @@ export function CastButton({ variant = 'page', cls = 'tb-btn tb-btn-icon', iconC
   if (!castSession.supported) return null;
 
   const overlay = variant === 'overlay';
-  const menuCls = overlay ? 'cast-picker' : 'ctx-menu cast-menu';
+  const menuCls = `${overlay ? 'cast-picker' : 'ctx-menu cast-menu'}${up ? ' cast-menu-up' : ''}`;
   const itemCls = overlay ? 'cast-picker-item' : 'ctx-menu-item';
   const title = device ? `${t('cast.casting_to')} ${device.name}` : t('cast.start');
 
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
index 67be344..f2c4374 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/music-app.js
@@ -10,6 +10,7 @@ import { usePager, Pager, pageSizeFrom } from './pager.js';
 import { Menu, MenuDots, useMenu } from './menu.js';
 import { PlaylistMenuButton, NameModal, usePlaylists } from './playlist-menu.js';
 import * as P from './playlists.js';
+import { CastButton } from './cast-session.js';
 
 // -- Music --------------------------------------------------------------------
 //
@@ -747,6 +748,8 @@ function MusicApp({
           lists=${playlists} reload=${reloadPlaylists}
           onPlayQueue=${onPlayQueue} onSync=${syncNow} />`}
         <${Pager} pager=${pager} />
+        ${/* The television the music bar plays to (cast-session.js). */''}
+        <${CastButton} />
         ${!hideFilter && html`<div class="tb-search">
           <${Icon} name="search" />
           <input type="text" placeholder="${t('group.filter')}"
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/music-player.js b/packages/meshbay-hub/src/meshbay_hub/static/music-player.js
index e97ce00..4587990 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/music-player.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/music-player.js
@@ -6,7 +6,8 @@ import { t } from './i18n.js';
 import { Icon } from './icon.js';
 import { useStickyBand } from './sticky.js';
 import { CHUNK_SIZE, pipelinedDownload } from './file-utils.js';
-import { playback } from './platform.js';
+import { playback, cast as castBridge } from './platform.js';
+import { castSession, useCastDevice, loadFile, CastButton } from './cast-session.js';
 
 /**
  * The Music app's persistent player bar (docs/MESHBAY_DESIGN.md §9.8).
@@ -30,6 +31,14 @@ import { playback } from './platform.js';
  * through `transport.requestAudioTranscode` first — a node-side,
  * cached-after-once AAC/M4A conversion — before the same download/blob path
  * runs.
+ *
+ * With a television chosen (cast-session.js), the same decrypted track is
+ * handed to the cast relay instead of the <audio> element, with its cover,
+ * and the bar becomes the receiver's remote: its play, pause, seek, previous
+ * and next drive the television, its clock is the television's, and the end
+ * of a track there moves the queue on as `ended` does here (docs/MESHBAY_DESIGN.md
+ * §11.4). The element keeps the track's source for its duration, and never
+ * plays while casting.
  */
 
 const MIME_BY_EXT = {
@@ -351,6 +360,64 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
     }
   }, []);
 
+  // ── Casting ──────────────────────────────────────────────────────────────
+  const castDevice = useCastDevice();
+  const remote = Boolean(castDevice) && castSession.canSendFiles;
+  const remoteRef = useRef(remote);
+  // Which track the television was last given, where it was when last
+  // polled, and which track's end has already moved the queue on: the
+  // receiver keeps reporting FINISHED until it is given something else.
+  const remoteTrackRef = useRef(null);
+  const remotePosRef = useRef(null);
+  const finishedRef = useRef(null);
+  // True while a track is on its way to the television: the receiver's
+  // status still describes the previous one until it lands.
+  const sendingRef = useRef(false);
+
+  // The track's cover, for the television to show beside it — found as the
+  // album card finds it (music-app.js): this track's own, else another queued
+  // track of the same album that carries one, else the cover the node found
+  // for the album. The node answers that last question from its cache, and
+  // asks MusicBrainz only where the group has it on and the track is tagged.
+  // A cover that cannot be had is no reason not to play the track.
+  const fetchCover = useCallback(async (entry) => {
+    try {
+      const { transport, gek } = await getConnection(entry.groupId);
+      if (!transport || !transport.connected) return null;
+      const sibling = entry.album && tracks.find((tr) => tr.thumb_hash
+        && tr.groupId === entry.groupId && tr.album === entry.album && tr.artist === entry.artist);
+      let hash = entry.thumb_hash || (sibling && sibling.thumb_hash) || null;
+      if (!hash && transport.fetchMusicMeta) {
+        const meta = await transport.fetchMusicMeta(entry.id).catch(() => null);
+        hash = (meta && meta.cover_thumb_hash) || null;
+      }
+      if (!hash) return null;
+      const chunks = await pipelinedDownload(transport, gek, hash, 1);
+      return { bytes: new Uint8Array(await new Blob(chunks).arrayBuffer()), type: 'image/jpeg' };
+    } catch {
+      return null;
+    }
+  }, [getConnection, tracks]);
+
+  const sendToTv = useCallback(async (entry, startAt = 0) => {
+    const cached = blobCacheRef.current.get(entry.id);
+    if (!cached) throw new Error(t('music.err_playback'));
+    sendingRef.current = true;
+    try {
+      const cover = await fetchCover(entry);
+      remoteTrackRef.current = entry.id;
+      remotePosRef.current = startAt;
+      finishedRef.current = null;
+      await loadFile({
+        owner: 'music', startAt,
+        bytes: new Uint8Array(await cached.blob.arrayBuffer()), type: cached.mime, cover,
+        title: entry.display_title || entry.name, artist: entry.artist || '', album: entry.album || '',
+      });
+    } finally {
+      sendingRef.current = false;
+    }
+  }, [fetchCover]);
+
   const fetchTrackBlob = useCallback(async (entry) => {
     const cached = blobCacheRef.current.get(entry.id);
     if (cached) return cached.url;
@@ -395,7 +462,8 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
     const chunks = await pipelinedDownload(transport, gek, downloadId, totalChunks);
     const blob = new Blob(chunks, { type: mime });
     const url = URL.createObjectURL(blob);
-    blobCacheRef.current.set(entry.id, { url, order: blobInsertRef.current++ });
+    // The blob itself too: a cast hands its bytes to the relay.
+    blobCacheRef.current.set(entry.id, { url, blob, mime, order: blobInsertRef.current++ });
     evictOldBlobs();
     return url;
   }, [getConnection, evictOldBlobs]);
@@ -520,6 +588,22 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
         if (!audio) return;
         audio.src = url;
         audio.currentTime = 0;
+        if (remoteRef.current) {
+          // To the television; the element keeps the source for its duration.
+          audio.pause();
+          setCurrentTime(0);
+          try {
+            await sendToTv(currentTrack, 0);
+          } catch (castErr) {
+            castErr.isCast = true;
+            throw castErr;
+          }
+          if (loadTokenRef.current !== myToken) return;
+          consecutiveFailuresRef.current = 0;
+          setPlaying(true);
+          prefetchNext(pos);
+          return;
+        }
         await audio.play();
         consecutiveFailuresRef.current = 0;
         setPlaying(true);
@@ -529,6 +613,9 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
         // Autoplay refused (no recent tap): the track is loaded and fine, it
         // waits for the play button. Not an error, and no reason to skip it.
         if (err && err.name === 'NotAllowedError') { setPlaying(false); prefetchNext(pos); return; }
+        // The television did not take it: that says nothing about the track,
+        // so the queue stays where it is, with the reason on screen.
+        if (err && err.isCast) { setError(err.message || String(err)); setPlaying(false); return; }
         if (err && err.isGroupDown && asleepOrJustWoke()) {
           // Our own connection is what went, not the group: keep the spinner
           // and this track, and try it again once we are back.
@@ -557,6 +644,9 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
   // stream). Both paths converge on the same bounded advance, so whichever
   // fires first, the queue moves on exactly once.
   const handleMediaError = useCallback(() => {
+    // Casting, the element only holds the source for its duration: whether it
+    // could decode it says nothing about what the television is playing.
+    if (remoteRef.current) return;
     const audio = audioRef.current;
     const mediaError = audio && audio.error;
     setError((mediaError && mediaError.message) || t('music.err_playback'));
@@ -583,27 +673,111 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
     if (order.length === 0) return;
     // A few seconds in: restart the current track, the way most players do,
     // rather than always jumping to the previous one.
+    if (remoteRef.current && castSession.owner === 'music' && (remotePosRef.current || 0) > 3) {
+      castBridge.chromecastSeek(0).catch(() => {});
+      remotePosRef.current = 0;
+      setCurrentTime(0);
+      return;
+    }
     const audio = audioRef.current;
-    if (audio && audio.currentTime > 3) { audio.currentTime = 0; return; }
+    if (!remoteRef.current && audio && audio.currentTime > 3) { audio.currentTime = 0; return; }
     if (pos > 0) { skipTo(pos - 1); return; }
     if (repeat === 'all') { skipTo(order.length - 1); }
   }, [pos, order.length, repeat, skipTo]);
 
   const onEnded = useCallback(() => {
     if (repeat === 'one') {
+      if (remoteRef.current && currentTrack) {
+        sendToTv(currentTrack, 0).catch((e) => { setError(e.message || String(e)); setPlaying(false); });
+        return;
+      }
       const audio = audioRef.current;
       if (audio) { audio.currentTime = 0; audio.play().catch(() => {}); }
       return;
     }
     skipNext();
-  }, [repeat, skipNext]);
+  }, [repeat, skipNext, currentTrack, sendToTv]);
+  const onEndedRef = useRef(onEnded);
+  onEndedRef.current = onEnded;
 
   const togglePlaying = useCallback(() => {
+    if (remoteRef.current && currentTrack) {
+      // A film or a photo has the television: playing again gives it back
+      // the track, from where it was.
+      if (castSession.owner !== 'music') {
+        sendToTv(currentTrack, remotePosRef.current || 0)
+          .then(() => { setError(''); setPlaying(true); })
+          .catch((e) => { setError(e.message || String(e)); setPlaying(false); });
+        return;
+      }
+      (playing ? castBridge.chromecastPause() : castBridge.chromecastPlay())
+        .then(() => setPlaying(!playing)).catch(() => {});
+      return;
+    }
     const audio = audioRef.current;
     if (!audio) return;
     if (playing) { audio.pause(); setPlaying(false); }
     else { audio.play().then(() => { setError(''); setPlaying(true); }).catch(() => {}); }
-  }, [playing]);
+  }, [playing, currentTrack, sendToTv]);
+
+  // A television chosen, or let go, in the middle of a track: the track goes
+  // on from where it was, on the other side.
+  useEffect(() => {
+    const was = remoteRef.current;
+    remoteRef.current = remote;
+    if (was === remote || !currentTrack) return;
+    const audio = audioRef.current;
+    if (remote) {
+      const at = audio ? audio.currentTime : 0;
+      const wasPlaying = playing;
+      if (audio) audio.pause();
+      // Still loading: the load effect sends it once it has it.
+      if (!blobCacheRef.current.has(currentTrack.id)) return;
+      sendToTv(currentTrack, at)
+        .then(async () => {
+          if (!wasPlaying) await castBridge.chromecastPause().catch(() => {});
+          setPlaying(wasPlaying);
+        })
+        .catch((e) => { setError(e.message || String(e)); setPlaying(false); });
+    } else {
+      const at = remotePosRef.current;
+      remoteTrackRef.current = null;
+      if (audio && at != null && isFinite(at)) audio.currentTime = at;
+      if (playing && audio) audio.play().catch(() => setPlaying(false));
+    }
+    // eslint-disable-next-line
+  }, [remote]);
+
+  // The television's clock and state, once a second, for as long as the
+  // track there is ours.
+  useEffect(() => {
+    if (!remote) return undefined;
+    let stopped = false;
+    const tick = async () => {
+      if (sendingRef.current || castSession.owner !== 'music' || !remoteTrackRef.current) return;
+      const s = await castBridge.status().catch(() => null);
+      const c = s && s.chromecast;
+      if (stopped || sendingRef.current || castSession.owner !== 'music' || !c) return;
+      if (!c.connected) { setPlaying(false); return; }
+      if (c.position != null) { remotePosRef.current = c.position; setCurrentTime(c.position); }
+      const state = c.playerState;
+      if (state === 'PLAYING' || state === 'BUFFERING') setPlaying(true);
+      else if (state === 'PAUSED') setPlaying(false);
+      else if (state === 'IDLE' && String(c.idleReason || '').toLowerCase() === 'finished'
+               && finishedRef.current !== remoteTrackRef.current) {
+        finishedRef.current = remoteTrackRef.current;
+        onEndedRef.current();
+      }
+    };
+    const id = setInterval(tick, 1000);
+    tick();
+    // A film or a photo took the television: the track there has stopped.
+    // Not when casting stops altogether — the track then carries on here.
+    const unsubscribe = castSession.subscribe(() => {
+      if (castSession.device && castSession.owner !== 'music') setPlaying(false);
+    });
+    return () => { stopped = true; clearInterval(id); unsubscribe(); };
+  }, [remote]);
 
   // Reshuffling keeps the currently playing track in place — turning shuffle
   // on mid-album must not interrupt what's already playing. Which track that
@@ -624,19 +798,36 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
   }, []);
 
   const seek = useCallback((e) => {
+    const to = parseFloat(e.target.value);
+    if (remoteRef.current) {
+      if (castSession.owner !== 'music') return;
+      castBridge.chromecastSeek(to).catch(() => {});
+      remotePosRef.current = to;
+      setCurrentTime(to);
+      return;
+    }
     const audio = audioRef.current;
-    if (audio && isFinite(audio.duration)) audio.currentTime = parseFloat(e.target.value);
+    if (audio && isFinite(audio.duration)) audio.currentTime = to;
   }, []);
 
   const handleClose = useCallback(() => {
     const audio = audioRef.current;
     if (audio) audio.pause();
+    // The television stops with the bar; it stays chosen for what comes next.
+    if (remoteRef.current && castSession.owner === 'music') {
+      castSession.claim(null);
+      castBridge.chromecastDisconnect().catch(() => {});
+      castBridge.stop().catch(() => {});
+    }
     if (onClose) onClose();
   }, [onClose]);
 
   if (!currentTrack) return null;
 
   const title = currentTrack.display_title || currentTrack.name;
+  // The element's, once it has read the file; the index's until then — and
+  // while casting, a file this device cannot decode still has a length.
+  const shownDuration = (isFinite(duration) && duration > 0) ? duration : (currentTrack.duration || 0);
   const repeatLabel = repeat === 'off' ? t('music.player_repeat_off')
     : repeat === 'all' ? t('music.player_repeat_all') : t('music.player_repeat_one');
 
@@ -678,17 +869,18 @@ function MusicPlayerBar({ getConnection, queue, onClose, userPrefs, onSaveQueue
       </div>
       <div class="music-player-seek">
         <span class="music-player-time">${formatTime(currentTime)}</span>
-        <input type="range" min="0" max=${duration || 0} step="1" value=${currentTime}
-          disabled=${!duration} onInput=${seek} />
-        <span class="music-player-time">${formatTime(duration)}</span>
+        <input type="range" min="0" max=${shownDuration} step="1" value=${currentTime}
+          disabled=${!shownDuration} onInput=${seek} />
+        <span class="music-player-time">${formatTime(shownDuration)}</span>
       </div>
       <div class="music-player-volume">
         <${Icon} name="volume" />
         <input type="range" min="0" max="1" step="0.05" value=${volume}
-          title=${t('music.player_volume')}
+          title=${t('music.player_volume')} disabled=${remote}
           onInput=${(e) => setVolume(parseFloat(e.target.value))} />
       </div>
       <div class="music-player-extra">
+        <${CastButton} cls="music-player-btn" up />
         <button class="music-player-btn" title=${t('music.player_queue')} onClick=${() => setShowQueue(true)}>
           <${Icon} name="menu" />
         </button>
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/platform.js b/packages/meshbay-hub/src/meshbay_hub/static/platform.js
index 3a0c628..28817c7 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/platform.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/platform.js
@@ -460,14 +460,16 @@ export const cast = {
     if (!bridge || !bridge.cast || !bridge.cast.subtitle) return null;
     return bridge.cast.subtitle(sub);
   },
-  // A photo for the receiver: `{ bytes, type }`, already scaled to the
-  // television. Absent from an older shell, so callers check `canShowImages`.
-  get canShowImages() {
-    return Boolean(bridge && bridge.cast && bridge.cast.image);
+  // A whole file for the receiver — a photo already scaled to the television,
+  // a music track — as `{ bytes, type, cover?: { bytes, type }, title?,
+  // artist?, album? }`; answers `{ url }` to load. Absent from an older
+  // shell, so callers check `canSendFiles`.
+  get canSendFiles() {
+    return Boolean(bridge && bridge.cast && bridge.cast.file);
   },
-  async image(img) {
-    if (!this.canShowImages) return null;
-    return bridge.cast.image(img);
+  async file(f) {
+    if (!this.canSendFiles) return null;
+    return bridge.cast.file(f);
   },
   async finish() {
     if (!bridge || !bridge.cast) return false;
@@ -529,6 +531,15 @@ export const cast = {
     if (!this.canControl) return null;
     return bridge.cast.chromecastPlay();
   },
+  // Seeking inside a file the receiver plays (a track); a film seeks by
+  // restarting the relay instead.
+  get canSeek() {
+    return Boolean(bridge && bridge.cast && bridge.cast.chromecastSeek);
+  },
+  async chromecastSeek(seconds) {
+    if (!this.canSeek) return null;
+    return bridge.cast.chromecastSeek(seconds);
+  },
 };
 
 /**
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/style.css b/packages/meshbay-hub/src/meshbay_hub/static/style.css
index 9be414f..9383043 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/style.css
+++ b/packages/meshbay-hub/src/meshbay_hub/static/style.css
@@ -2054,6 +2054,8 @@ button:disabled { opacity: 0.5; cursor: not-allowed; }
    any other menu there, hung under the button rather than at a point. */
 .cast-btn.casting { color: var(--accent); border-color: var(--accent); }
 .ctx-menu.cast-menu { position: absolute; top: calc(100% + 4px); right: 0; z-index: 150; }
+/* From the music bar, at the bottom of the window: the menu opens upward. */
+.cast-menu-up { top: auto !important; bottom: calc(100% + 4px); }
 .ctx-menu-item.cast-menu-current { color: var(--text-dim); cursor: default; }
 .ctx-menu-item.cast-menu-current:hover { background: none; }
 .ctx-menu-item svg { width: 16px; height: 16px; flex-shrink: 0; }
diff --git a/packages/meshbay-hub/src/meshbay_hub/static/video-player.js b/packages/meshbay-hub/src/meshbay_hub/static/video-player.js
index ed1f18c..37ea727 100644
--- a/packages/meshbay-hub/src/meshbay_hub/static/video-player.js
+++ b/packages/meshbay-hub/src/meshbay_hub/static/video-player.js
@@ -1316,6 +1316,7 @@ function VideoPlayer({ entry, transportRef, gekRef, onClose, onDownload }) {
               }).then(async (result) => {
                 if (castRestartGenRef.current !== gen) return;
                 if (!result) return;
+                if (device || castSession.device) castSession.claim('video');
                 setCastUrl(result.url);
                 const status = await platform.cast.status();
                 if (status && status.chromecast && status.chromecast.connected) {
diff --git a/packages/meshbay-hub/tests/harness/cast_session_probe.py b/packages/meshbay-hub/tests/harness/cast_session_probe.py
index 2904860..573dd95 100644
--- a/packages/meshbay-hub/tests/harness/cast_session_probe.py
+++ b/packages/meshbay-hub/tests/harness/cast_session_probe.py
@@ -40,9 +40,13 @@ FRAME = r"""<!doctype html><html><head><meta charset=utf-8>
 <script>
 // A module that fails to load never reaches its own catch: say so.
 const report = (error) => parent.postMessage({ error }, '*');
-addEventListener('error', (e) => report(
-  `${e.message || 'load error'} ${e.filename || (e.target && e.target.src) || ''}`
-  + `:${e.lineno || ''}`), true);
+// Scripts only: the music case's stub track is three bytes no <audio>
+// element can decode, which is expected and is not the page failing.
+addEventListener('error', (e) => {
+  if (!(e instanceof ErrorEvent) && !(e.target && e.target.tagName === 'SCRIPT')) return;
+  report(`${e.message || 'load error'} ${e.filename || (e.target && e.target.src) || ''}`
+         + `:${e.lineno || ''}`);
+}, true);
 addEventListener('unhandledrejection',
   (e) => report(String((e.reason && e.reason.stack) || e.reason)));
 const WITH_BRIDGE = !location.search.includes('nobridge');
@@ -111,6 +115,8 @@ window.MeshBayTransport = function () {
 // The native side, as the Electron preload and the Android shim present it,
 // recording every cast call.
 window.CALLS = [];
+// What the stub receiver reports: the music case moves it along.
+window.TV = { state: 'IDLE', position: 0, idle: null };
 if (WITH_BRIDGE) {
   let connected = false, v = 0;
   const rec = (name, arg) => { CALLS.push({ name, arg }); };
@@ -127,13 +133,19 @@ if (WITH_BRIDGE) {
       stop: async () => { rec('stop'); return true; },
       subtitle: async () => null,
       finish: async () => true,
-      image: async (img) => {
-        const bmp = await createImageBitmap(new Blob([img.bytes], { type: img.type }));
-        rec('image', { type: img.type, width: bmp.width, height: bmp.height,
-                       jpeg: img.bytes[0] === 0xff && img.bytes[1] === 0xd8 });
-        return { url: 'http://tv/image?t=x&v=' + (++v) };
+      file: async (f) => {
+        let info = { type: f.type, size: f.bytes.length, title: f.title || null,
+                     artist: f.artist || null, album: f.album || null, cover: !!f.cover };
+        if (f.type.startsWith('image/')) {
+          const bmp = await createImageBitmap(new Blob([f.bytes], { type: f.type }));
+          info = { ...info, width: bmp.width, height: bmp.height,
+                   jpeg: f.bytes[0] === 0xff && f.bytes[1] === 0xd8 };
+        }
+        rec('file', info);
+        return { url: 'http://tv/file?t=x&v=' + (++v) };
       },
-      status: async () => ({ active: true, url: null, chromecast: { connected } }),
+      status: async () => ({ active: true, url: null, chromecast: {
+        connected, playerState: TV.state, position: TV.position, idleReason: TV.idle } }),
       scan: async () => { rec('scan'); return true; },
       devices: async () => ({ devices: [{ id: 'tv1', name: 'Salon' }], scanning: false }),
       chromecastConnect: async (o) => {
@@ -142,8 +154,9 @@ if (WITH_BRIDGE) {
       },
       chromecastReload: async (o) => { rec('reload', o); return { playerState: 'IDLE' }; },
       chromecastDisconnect: async () => { rec('disconnect'); connected = false; return true; },
-      chromecastPause: async () => ({}),
-      chromecastPlay: async () => ({}),
+      chromecastPause: async () => { rec('pause'); TV.state = 'PAUSED'; return {}; },
+      chromecastPlay: async () => { rec('play'); TV.state = 'PLAYING'; return {}; },
+      chromecastSeek: async (t) => { rec('seek', t); TV.position = t; return {}; },
     },
   };
 }
@@ -161,12 +174,91 @@ async function until(pred, what, tries = 200) {
   throw new Error('timed out waiting for ' + what);
 }
 const calls = (name) => CALLS.filter((c) => c.name === name);
+const files = () => calls('file').map((c) => c.arg);
 // Files is always first; then the enabled apps in their registry order.
 const videosTab = () => $$('.group-tab')[1];
 const count = () => (($('.photo-lightbox-count') || {}).textContent || '').trim();
 
+// The music bar, with a television already chosen: two tracks of one album.
+async function music() {
+  const { MusicPlayerBar } = await import('/music-player.js');
+  const { castSession } = await import('/cast-session.js');
+  const out = {};
+  castSession.choose({ id: 'tv1', name: 'Salon' });
+  // Which hashes were fetched, so a cover can be traced to where it came from.
+  window.FETCHED = [];
+  const transport = { connected: true, async waitForReconnect() {},
+                      async fetchChunk(id) {
+                        FETCHED.push(id);
+                        return { nonce: 'n', ct: new Uint8Array([1, 2, 3]) };
+                      },
+                      // The node's MusicBrainz answer: a cover for the other album only.
+                      async fetchMusicMeta(id) {
+                        CALLS.push({ name: 'musicMeta', arg: id });
+                        return id === 't3' ? { confidence: 1, cover_thumb_hash: 'mb-cover' }
+                          : { confidence: 0 };
+                      } };
+  const getConnection = async () => ({ transport, gek: 'gek' });
+  // One has no cover of its own but Two, of the same album, has; Three is of
+  // another album whose only cover is the one the node found.
+  const track = (n, title, album, hash) => ({ id: 't' + n, name: title + '.mp3', size: 3,
+    groupId: 'g1', display_title: title, artist: 'Some Band', album, duration: 200,
+    thumb_hash: hash });
+  const queue = { tracks: [track(1, 'One', 'An Album', null), track(2, 'Two', 'An Album', 'cover2'),
+                           track(3, 'Three', 'Another Album', null)], startIndex: 0, nonce: 1 };
+  render(html`<${MusicPlayerBar} getConnection=${getConnection} queue=${queue}
+    userPrefs=${{}} onClose=${() => {}} />`, document.getElementById('root'));
+
+  await until(() => calls('connect').length === 1, 'the first track on the television');
+  out.first = { file: files()[0], connect: calls('connect')[0].arg,
+                coverFetched: FETCHED.includes('cover2') };
+  TV.state = 'PLAYING'; TV.position = 12;
+  await until(() => ($$('.music-player-time')[0] || {}).textContent === '0:12',
+              "the television's clock in the bar");
+  out.barButton = !!$('.music-player-bar .cast-btn.casting');
+  out.volumeDisabled = $('.music-player-volume input').disabled;
+
+  $('.music-player-play').click();
+  await until(() => calls('pause').length === 1, 'pause on the television');
+  const slider = $('.music-player-seek input');
+  slider.value = '30';
+  slider.dispatchEvent(new Event('input', { bubbles: true }));
+  await until(() => calls('seek').length === 1, 'a seek on the television');
+  out.seek = calls('seek')[0].arg;
+
+  // The television finishes the track: the next one goes, once.
+  TV.state = 'IDLE'; TV.idle = 'FINISHED';
+  await until(() => calls('reload').length === 1, 'the next track on the television');
+  out.second = { file: files()[1], reload: calls('reload')[0].arg,
+                 title: $('.music-player-title').textContent.trim() };
+  TV.state = 'PLAYING'; TV.idle = null; TV.position = 1;
+  await sleep(2500);
+  out.filesAfterSettling = files().length;
+
+  // Three: the cover comes from the node's answer for its album.
+  TV.state = 'IDLE'; TV.idle = 'FINISHED';
+  await until(() => calls('reload').length === 2, 'the third track on the television');
+  out.third = { file: files()[2], mbCover: FETCHED.includes('mb-cover'),
+                metaAsked: calls('musicMeta').map((c) => c.arg) };
+  TV.state = 'PLAYING'; TV.idle = null;
+
+  // Stopping the cast lets the television go.
+  await castSession.end();
+  await sleep(200);
+  out.afterStop = { disconnects: calls('disconnect').length,
+                    barCasting: !!$('.music-player-bar .cast-btn.casting') };
+  parent.postMessage(out, '*');
+}
+
 (async () => {
   const out = { bridge: !!window.meshbay };
+  if (location.search.includes('music')) {
+    try { await initLocale(); await music(); }
+    catch (err) {
+      parent.postMessage({ calls: CALLS, error: String((err && err.stack) || err) }, '*');
+    }
+    return;
+  }
   try {
     await initLocale();
     render(html`<${GroupPage} groupId="g1" token="t" username="me" userId="u1"
@@ -195,13 +287,13 @@ const count = () => (($('.photo-lightbox-count') || {}).textContent || '').trim(
     $$('.cast-menu .ctx-menu-item').find((b) => b.textContent.includes('Salon')).click();
     await until(() => $('.photo-lightbox'), 'the lightbox to open on choosing');
     await until(() => calls('connect').length === 1, 'the first photo to reach the television');
-    out.first = { count: count(), image: calls('image')[0], connect: calls('connect')[0].arg,
+    out.first = { count: count(), image: files()[0], connect: calls('connect')[0].arg,
                   lightboxCasting: !!$('.photo-lightbox .cast-btn.casting') };
 
     // Next photo: the receiver is connected, so it is reloaded.
     $('.photo-nav-next').click();
     await until(() => calls('reload').length === 1, 'the second photo');
-    out.second = { count: count(), reload: calls('reload')[0].arg, images: calls('image').length };
+    out.second = { count: count(), reload: calls('reload')[0].arg, images: files().length };
 
     // Slideshow: on by itself to the last photo, then off.
     const play = $$('.photo-lightbox .video-top-bar .video-close')
@@ -209,7 +301,7 @@ const count = () => (($('.photo-lightbox-count') || {}).textContent || '').trim(
     play.click();
     await until(() => count() === '3 / 3', 'the slideshow to reach the last photo', 160);
     await until(() => play.getAttribute('aria-pressed') === 'false', 'the slideshow to end', 160);
-    out.slideshow = { count: count(), images: calls('image').length,
+    out.slideshow = { count: count(), images: files().length,
                       reloads: calls('reload').length };
 
     // Close the lightbox; Videos shows the same television; a film opens as its remote.
@@ -341,16 +433,17 @@ def check(engine: str, cast: dict, plain: dict) -> list[str]:
     first = cast["first"]
     if first["count"] != "1 / 3":
         bad.append(f"choosing a television did not open the first photo: {first['count']}")
-    img = first["image"]["arg"]
+    img = first["image"]
     if not (img["type"] == "image/jpeg" and img["jpeg"] and img["width"] == 1440
             and img["height"] == 1080):
         bad.append(f"the photo did not leave as a 1440x1080 JPEG: {img}")
-    if first["connect"] != {"deviceId": "tv1", "mediaUrl": "http://tv/image?t=x&v=1"}:
+    if first["connect"] != {"deviceId": "tv1", "mediaUrl": "http://tv/file?t=x&v=1",
+                            "startAt": 0}:
         bad.append(f"connect: {first['connect']}")
     if not first["lightboxCasting"]:
         bad.append("the lightbox's cast button does not say it is casting")
     if cast["second"]["count"] != "2 / 3" or cast["second"]["reload"] != {
-            "mediaUrl": "http://tv/image?t=x&v=2"}:
+            "mediaUrl": "http://tv/file?t=x&v=2", "startAt": 0}:
         bad.append(f"next photo: {cast['second']}")
     if cast["slideshow"]["count"] != "3 / 3" or cast["slideshow"]["images"] != 3:
         bad.append(f"slideshow: {cast['slideshow']}")
@@ -367,6 +460,39 @@ def check(engine: str, cast: dict, plain: dict) -> list[str]:
     return [f"{engine}: {b}" for b in bad]
 
 
+def check_music(engine: str, m: dict) -> list[str]:
+    if "error" in m:
+        return [f"{engine}: music: {m['error']}"]
+    bad = []
+    f = m["first"]["file"]
+    if not (f["type"] == "audio/mpeg" and f["title"] == "One" and f["artist"] == "Some Band"
+            and f["album"] == "An Album" and f["cover"] and m["first"]["coverFetched"]):
+        bad.append(f"the first track left without its album's cover: {m['first']}")
+    third = m["third"]
+    if not (third["file"]["title"] == "Three" and third["file"]["cover"] and third["mbCover"]):
+        bad.append(f"the node's cover did not reach the television: {third}")
+    if "t1" in third["metaAsked"] or "t2" in third["metaAsked"]:
+        bad.append(f"the node was asked for a cover a track already had: {third['metaAsked']}")
+    if m["first"]["connect"] != {"deviceId": "tv1", "mediaUrl": "http://tv/file?t=x&v=1",
+                                 "startAt": 0}:
+        bad.append(f"connect: {m['first']['connect']}")
+    if not m["barButton"]:
+        bad.append("the music bar's cast button does not say it is casting")
+    if not m["volumeDisabled"]:
+        bad.append("the volume slider still acts while casting")
+    if m["seek"] != 30:
+        bad.append(f"seek: {m['seek']}")
+    s = m["second"]
+    if s["file"]["title"] != "Two" or s["title"] != "Two" or s["reload"] != {
+            "mediaUrl": "http://tv/file?t=x&v=2", "startAt": 0}:
+        bad.append(f"the end of a track did not move the queue on: {s}")
+    if m["filesAfterSettling"] != 2:
+        bad.append(f"a finished track moved the queue on more than once: {m['filesAfterSettling']}")
+    if m["afterStop"]["disconnects"] < 1 or m["afterStop"]["barCasting"]:
+        bad.append(f"stopping: {m['afterStop']}")
+    return [f"{engine}: music: {b}" for b in bad]
+
+
 def main() -> int:
     failures = []
     with socketserver.ThreadingTCPServer(("127.0.0.1", PORT), H) as srv:
@@ -377,11 +503,13 @@ def main() -> int:
                 continue
             cast = browse(engine, "")
             plain = browse(engine, "?nobridge")
-            if cast is None or plain is None:
+            music = browse(engine, "?music")
+            if cast is None or plain is None or music is None:
                 failures.append(f"{engine}: the page never reported")
                 continue
-            print(f"{engine}:", json.dumps(cast, indent=1))
+            print(f"{engine}:", json.dumps({"photos-videos": cast, "music": music}, indent=1))
             failures += check(engine, cast, plain)
+            failures += check_music(engine, music)
     for f in failures:
         print("FAIL", f, file=sys.stderr)
     if not failures:
diff --git a/packages/meshbay-hub/tests/test_android_cast.py b/packages/meshbay-hub/tests/test_android_cast.py
index b537df7..ebcdec4 100644
--- a/packages/meshbay-hub/tests/test_android_cast.py
+++ b/packages/meshbay-hub/tests/test_android_cast.py
@@ -103,12 +103,14 @@ def test_the_receiver_is_pointed_at_the_relay_and_nothing_else():
 def test_relay_calls_keep_their_order():
     """The page does not await each push; on a pool they could overtake."""
     channels = _read(CAST / "CastChannels.kt")
-    assert '"cast:start", "cast:push", "cast:subtitle", "cast:image", "cast:finish", "cast:stop"' in channels
+    assert '"cast:start", "cast:push", "cast:subtitle",' in channels
+    assert ('"cast:file:begin", "cast:file:write", "cast:file:end", "cast:finish", "cast:stop"'
+            in channels)
     bridge = _read(SRC / "bridge" / "Bridge.kt")
     assert "Executors.newSingleThreadExecutor()" in bridge
     assert "(if (ordered) serial else work).execute" in bridge
-    assert "fun ordered(frame: BinaryFrame) = frame.channel == BinaryFrame.CAST_PUSH" in _read(
-        SRC / "bridge" / "Channels.kt")
+    assert ("fun ordered(frame: BinaryFrame) = frame.channel == BinaryFrame.CAST_PUSH"
+            " || frame.channel == BinaryFrame.CAST_FILE") in _read(SRC / "bridge" / "Channels.kt")
 
 
 def test_screen_off_survival_is_switched_on_only_while_casting_or_playing():
diff --git a/packages/meshbay-hub/tests/test_cast_files.py b/packages/meshbay-hub/tests/test_cast_files.py
new file mode 100644
index 0000000..8f51d80
--- /dev/null
+++ b/packages/meshbay-hub/tests/test_cast_files.py
@@ -0,0 +1,372 @@
+"""
+Whole files on a cast receiver — photos and music tracks — and the television
+a session casts to.
+
+A file takes a different road to the television than a film: no stream, one
+file at a time, handed to the relay in pieces (begin, writes, end), served at
+`/file` with its cover at `/cover`, and loaded by the default media receiver
+as a picture or as a music track. The page scales and re-encodes a photo
+first (cast-session.js); a track goes as it is stored.
+
+The first half runs the desktop relay itself, as test_cast_subtitles.py does:
+it is plain Node with no dependencies. The file is behind the same token as
+the stream, its address changes with every file — a receiver handed the same
+URL twice shows what it already has — ranges are honoured, because that is how
+a receiver seeks in a track, and only a picture or a sound is served as one.
+
+The second half holds the wiring: what the receiver loads is the shell's to
+say, never the page's; Android accepts no URL but the relay's own; a
+television chosen anywhere is the one a film opens on, with the player as its
+remote from the start; and the music bar drives the television once one is
+chosen.
+"""
+
+import json
+import re
+import shutil
+import subprocess
+from pathlib import Path
+
+import pytest
+
+PACKAGES = Path(__file__).resolve().parents[2]
+STATIC = PACKAGES / "meshbay-hub" / "src" / "meshbay_hub" / "static"
+DESKTOP = PACKAGES / "meshbay-client" / "src"
+RELAY = DESKTOP / "cast-relay.js"
+CHROMECAST = DESKTOP / "cast-chromecast.js"
+ANDROID_MAIN = PACKAGES / "meshbay-android" / "app" / "src" / "main"
+ANDROID_SRC = ANDROID_MAIN / "kotlin"
+CLIENT = ANDROID_SRC / "org" / "meshbay" / "client"
+CAST = CLIENT / "cast"
+SHIM = ANDROID_MAIN / "assets" / "bridge" / "meshbay-bridge.js"
+
+
+def _read(path: Path) -> str:
+    return path.read_text(encoding="utf-8")
+
+
+RELAY_SCRIPT = r"""
+const http = require('node:http');
+const CastRelay = require(process.argv[2]);
+const get = (url, headers = {}) => new Promise((resolve, reject) => {
+  http.get(url, { headers }, (res) => {
+    const parts = [];
+    res.on('data', (c) => parts.push(c));
+    res.on('end', () => resolve({ status: res.statusCode, headers: res.headers,
+                                  body: Buffer.concat(parts).toString('hex') }));
+  }).on('error', reject);
+});
+const refused = async (f) => { try { await f(); return false; } catch { return true; } };
+const send = async (relay, bytes, opts) => {
+  await relay.beginFile({ size: bytes.length, ...opts });
+  for (let at = 0; at < bytes.length; at += 3) relay.writeFile(bytes.subarray(at, at + 3));
+  return relay.endFile();
+};
+(async () => {
+  const relay = new CastRelay();
+  const out = {};
+  out.activeBefore = relay.active;
+  out.htmlRefused = await refused(() => relay.beginFile({ type: 'text/html', size: 3 }));
+  out.activeAfterRefusal = relay.active;
+
+  const jpeg = Buffer.from([0xff, 0xd8, 1, 2, 0xff, 0xd9]);
+  const first = await send(relay, jpeg, { type: 'image/jpeg' });
+  out.activeAfterPhoto = relay.active;
+  out.firstUrl = first.url;
+  out.photo = await get(first.url);
+  out.badToken = (await get(first.url.replace(/t=[0-9a-f]+/, 't=x'))).status;
+  out.photoMeta = relay.fileMeta;
+
+  // A track, its cover and what to show with it; read back whole and by range.
+  const track = Buffer.from([...Array(20).keys()]);
+  const second = await send(relay, track, {
+    type: 'audio/flac', title: 'A Song', artist: 'Some Band', album: 'An Album',
+    cover: { bytes: Buffer.from([0xff, 0xd8, 7, 0xff, 0xd9]), type: 'image/jpeg' } });
+  out.secondUrl = second.url;
+  out.trackType = relay.fileType;
+  out.trackMeta = relay.fileMeta;
+  out.whole = await get(second.url);
+  out.range = await get(second.url, { Range: 'bytes=5-9' });
+  out.tail = await get(second.url, { Range: 'bytes=15-' });
+  out.beyond = (await get(second.url, { Range: 'bytes=50-60' })).status;
+  out.cover = await get(relay.fileMeta.cover);
+
+  // Fewer bytes than announced is not a file; more is refused as they come.
+  await relay.beginFile({ type: 'audio/mpeg', size: 10 });
+  relay.writeFile(Buffer.from([1, 2, 3]));
+  out.shortRefused = await refused(() => relay.endFile());
+  await relay.beginFile({ type: 'audio/mpeg', size: 2 });
+  out.longRefused = await refused(() => relay.writeFile(Buffer.from([1, 2, 3])));
+  out.stillServed = (await get(second.url)).status;
+
+  await relay.start({});
+  out.fileAfterFilm = relay.fileUrl;
+  await send(relay, jpeg, { type: 'image/jpeg' });
+  await relay.stop();
+  out.fileAfterStop = relay.fileUrl;
+  console.log(JSON.stringify(out));
+})().catch((e) => { console.error(e); process.exit(1); });
+"""
+
+
+@pytest.fixture(scope="module")
+def relay_run(tmp_path_factory):
+    if shutil.which("node") is None or not RELAY.exists():
+        pytest.skip("node or the desktop client sources are not available")
+    script = tmp_path_factory.mktemp("cf") / "relay.cjs"
+    script.write_text(RELAY_SCRIPT, encoding="utf-8")
+    proc = subprocess.run(["node", str(script), str(RELAY)],
+                          capture_output=True, text=True, encoding="utf-8", timeout=30)
+    assert proc.returncode == 0, proc.stderr
+    return json.loads(proc.stdout)
+
+
+def test_a_file_starts_the_relay_and_is_served_behind_its_token(relay_run):
+    assert relay_run["activeBefore"] is False
+    assert relay_run["activeAfterPhoto"] is True
+    photo = relay_run["photo"]
+    assert photo["status"] == 200
+    assert photo["headers"]["content-type"] == "image/jpeg"
+    assert photo["headers"]["cache-control"] == "no-store"
+    assert photo["body"] == "ffd80102ffd9"
+    assert relay_run["badToken"] == 403
+    assert relay_run["photoMeta"]["cover"] is None
+
+
+def test_every_file_has_its_own_address(relay_run):
+    assert re.search(r"/file\?t=[0-9a-f]{32}&v=\d+$", relay_run["firstUrl"])
+    assert relay_run["secondUrl"] != relay_run["firstUrl"]
+
+
+def test_a_track_is_served_with_its_cover_and_what_it_is(relay_run):
+    assert relay_run["trackType"] == "audio/flac"
+    meta = relay_run["trackMeta"]
+    assert (meta["title"], meta["artist"], meta["album"]) == ("A Song", "Some Band", "An Album")
+    assert re.search(r"/cover\?t=[0-9a-f]{32}&v=\d+$", meta["cover"])
+    assert relay_run["cover"]["status"] == 200
+    assert relay_run["cover"]["body"] == "ffd807ffd9"
+    assert relay_run["whole"]["body"] == bytes(range(20)).hex()
+    assert relay_run["whole"]["headers"]["accept-ranges"] == "bytes"
+
+
+def test_a_receiver_seeks_in_a_track_by_range(relay_run):
+    r = relay_run["range"]
+    assert r["status"] == 206
+    assert r["headers"]["content-range"] == "bytes 5-9/20"
+    assert r["body"] == bytes(range(5, 10)).hex()
+    tail = relay_run["tail"]
+    assert tail["status"] == 206 and tail["body"] == bytes(range(15, 20)).hex()
+    assert relay_run["beyond"] == 416
+
+
+def test_only_a_whole_picture_or_sound_is_served(relay_run):
+    assert relay_run["htmlRefused"] is True
+    assert relay_run["activeAfterRefusal"] is False, "a refused file starts nothing"
+    assert relay_run["shortRefused"] is True
+    assert relay_run["longRefused"] is True
+    assert relay_run["stillServed"] == 200, "a failed send leaves the shown file alone"
+
+
+def test_a_film_or_a_stop_takes_the_file_down(relay_run):
+    assert relay_run["fileAfterFilm"] is None
+    assert relay_run["fileAfterStop"] is None
+
+
+def test_the_receiver_loads_a_photo_as_a_picture_and_a_track_as_music():
+    if shutil.which("node") is None or not CHROMECAST.exists():
+        pytest.skip("node or the desktop client sources are not available")
+    script = (
+        "const Module = require('node:module');"
+        "const real = Module._load;"
+        "Module._load = function (r, ...a) {"
+        "  if (r === 'bonjour-service') return { Bonjour: class {} };"
+        "  if (r === 'castv2-client') return { Client: class {}, DefaultMediaReceiver: {} };"
+        "  return real.call(this, r, ...a); };"
+        f"const {{ mediaFor, loadOptionsFor }} = require({json.dumps(str(CHROMECAST))});"
+        "const meta = { title: 'A Song', artist: 'Some Band', album: 'An Album',"
+        "               cover: 'http://x/cover?t=a&v=2' };"
+        "console.log(JSON.stringify({"
+        "  photo: mediaFor('http://x/file?t=a&v=1', null,"
+        "                  { contentType: 'image/jpeg', meta: { cover: null } }),"
+        "  track: mediaFor('http://x/file?t=a&v=2', null, { contentType: 'audio/flac', meta }),"
+        "  from: loadOptionsFor(null, 42.5),"
+        "  film: mediaFor('http://x/stream.mp4?t=a', null, null),"
+        "  filmOptions: loadOptionsFor(null, 0),"
+        "  legacy: mediaFor('http://x/stream.mp4?t=a', null) }));")
+    proc = subprocess.run(["node", "-e", script], capture_output=True, text=True,
+                          encoding="utf-8", timeout=30)
+    assert proc.returncode == 0, proc.stderr
+    out = json.loads(proc.stdout)
+    assert out["photo"]["contentType"] == "image/jpeg"
+    assert out["photo"]["streamType"] == "NONE"
+    assert "tracks" not in out["photo"]
+    track = out["track"]
+    assert track["contentType"] == "audio/flac" and track["streamType"] == "BUFFERED"
+    assert track["metadata"] == {"metadataType": 3, "title": "A Song", "artist": "Some Band",
+                                 "albumName": "An Album",
+                                 "images": [{"url": "http://x/cover?t=a&v=2"}]}
+    assert out["from"]["currentTime"] == 42.5
+    assert "currentTime" not in out["filmOptions"]
+    assert out["film"] == out["legacy"], "a film is loaded exactly as before"
+    assert out["film"]["streamType"] == "LIVE" and out["film"]["contentType"] == "video/mp4"
+
+
+def test_the_shell_not_the_page_says_what_the_receiver_loads():
+    """The page names a URL; what it is, is the relay's to say. A page that
+    could name the content type could have a television load the stream as
+    anything at all."""
+    main = _read(DESKTOP / "main.js")
+    load_of = main.split("const loadOf = ", 1)[1].split("\n\n", 1)[0]
+    assert "mediaUrl === castRelay.fileUrl" in load_of
+    assert "contentType: castRelay.fileType, meta: castRelay.fileMeta" in load_of
+    assert "subtitle: null" in load_of, "a file carries no subtitle"
+    assert main.count("loadOf(mediaUrl, subtitle)") == 2, "connect and reload both"
+    # A start position means something for a file only; a film starts where
+    # its relay does.
+    assert main.count("l.file ? startAt : 0") == 2
+
+
+def test_android_accepts_the_relays_file_and_nothing_else():
+    if not CAST.exists():
+        pytest.skip("android sources not present")
+    channels = _read(CAST / "CastChannels.kt")
+    check = channels.split("private fun relayUrl(", 1)[1].split("\n    }", 1)[0]
+    assert "asked != ours && asked != relay.fileUrl" in check
+    assert 'put("contentType", relay.fileType).put("meta", relay.fileMeta()' in channels
+    assert "url == relay.fileUrl -> null" in channels, "a file carries no subtitle"
+    assert 'if (url == relay.fileUrl) maxOf(0.0, o.optDouble("startAt", 0.0)) else 0.0' in channels
+    # A file is not a cast that has to survive the screen going off.
+    begin = channels.split('"cast:file:begin" ->', 1)[1].split('"cast:file:end"', 1)[0]
+    assert "onCasting" not in begin
+    relay = _read(CAST / "CastRelay.kt")
+    assert '"/file" -> serveFile(out, socket, range)' in relay
+    assert '"/cover" -> serveCover(out, socket)' in relay
+    serve = relay.split("private fun serve(", 1)[1]
+    assert serve.index('query["t"] != token') < serve.index('"/file"'), "behind the token"
+    # On disk, never held: a long lossless track is a few hundred megabytes.
+    assert 'File(spoolDir, "file-${fileSeq.incrementAndGet()}.bin")' in relay
+    assert "java.io.FileOutputStream(slot.path)" in relay
+    control = _read(CAST / "CastControl.kt")
+    assert "MediaInfo.STREAM_TYPE_NONE" in control
+    assert "MediaMetadata.MEDIA_TYPE_PHOTO" in control
+    assert "MediaMetadata.MEDIA_TYPE_MUSIC_TRACK" in control
+    assert "MediaInfo.STREAM_TYPE_BUFFERED" in control
+    assert "setCurrentTime((startAt * 1000).toLong())" in control
+    assert "MediaSeekOptions.Builder().setPosition(" in control
+    # Loaded is shown: a photo never reaches PLAYING, and waiting for it
+    # would hold every photo for the full fifteen seconds.
+    load = control.split("private fun load(", 1)[1]
+    assert load.index("if (photo) return") < load.index("PLAY_WAIT_MS")
+
+
+def test_a_file_crosses_the_android_bridge_in_binary_pieces():
+    """One message the size of a lossless track would be the WebView's to
+    refuse; a file goes in pieces of a megabyte, as binary frames where the
+    WebView has them."""
+    if not SHIM.exists():
+        pytest.skip("android sources not present")
+    shim = _read(SHIM)
+    assert "const CAST_FILE = 3;" in shim
+    assert "const FILE_PIECE = 1024 * 1024;" in shim
+    assert ("BINARY ? sendBinary(CAST_FILE, 0, piece) : call('cast:file:write', base64Of(piece))"
+            in shim)
+    assert "const val CAST_FILE = 3" in _read(CLIENT / "save" / "SaveNames.kt")
+    channels = _read(CLIENT / "bridge" / "Channels.kt")
+    assert "BinaryFrame.CAST_FILE -> " in channels and ".writeFile(frame.bytes" in channels
+
+
+def test_a_television_chosen_anywhere_takes_the_next_film():
+    """The player opens as the remote of a television chosen before it, the
+    cast pending until the first segment exactly as a restart is; choosing one
+    in the player keeps it for the session, and stopping there forgets it."""
+    player = _read(STATIC / "video-player.js")
+    assert ("const [autoCast] = useState(() => "
+            "(castSession.supported ? castSession.device : null));") in player
+    assert "useState(Boolean(autoCast))" in player
+    assert "castActiveRef = useRef(Boolean(autoCast))" in player
+    assert "castRestartPendingRef = useRef(Boolean(autoCast))" in player
+    assert "castDeviceRef = useRef(autoCast)" in player
+    assert "useState(autoCast ? autoCast.name : null)" in player
+    stop = player.split("const stopCast = async () => {", 1)[1].split("};", 1)[0]
+    assert "castSession.forget()" in stop
+    assert "castSession.choose(d);" in player
+    assert "castSession.claim('video')" in player
+
+
+def test_the_cast_button_is_where_the_media_are():
+    """Videos' toolbar, the Photos landing, a photo album's bar and Music's
+    toolbar are drawn by the group page and the search page alike, so one
+    button in each covers both. On the Photos landing the button keeps a
+    toolbar Search would otherwise hide. The music bar has its own, opening
+    upward from the bottom of the window."""
+    videos = _read(STATIC / "video-app.js")
+    assert "<${CastButton} />" in videos.split('<div class="video-toolbar">', 1)[1]
+    photos = _read(STATIC / "photos-app.js")
+    landing = photos.split("function PhotosApp(", 1)[1]
+    assert "(!hideFilter || castSession.supported) && html`" in landing
+    assert "<${CastButton} />" in landing.split('<div class="photo-toolbar">', 1)[1]
+    album = photos.split("function AlbumView(", 1)[1]
+    assert "<${CastButton}" in album
+    lightbox = photos.split("function Lightbox(", 1)[1].split("function AlbumView(", 1)[0]
+    assert '<${CastButton} variant="overlay"' in lightbox
+    assert "if (castDevice && blobUrl && blob) showPhoto(blob);" in lightbox
+    music = _read(STATIC / "music-app.js")
+    assert "<${CastButton} />" in music.split('<div class="video-toolbar">', 1)[1]
+    bar = _read(STATIC / "music-player.js")
+    assert '<${CastButton} cls="music-player-btn" up />' in bar
+    # The group page draws them through the app registry, the search page
+    # imports them: the same components either way.
+    registry = _read(STATIC / "apps.js")
+    search = _read(STATIC / "search-page.js")
+    for page in (registry, search):
+        for app in ("VideoApp", "PhotosApp", "MusicApp"):
+            assert app in page
+
+
+def test_the_music_bar_drives_the_television():
+    """With a television chosen, the decrypted track goes to the relay instead
+    of the element, and the bar's controls and clock are the receiver's. The
+    receiver keeps saying FINISHED until it is given something else, so the
+    end of a track moves the queue on once; and a television a film or a
+    photo has taken is not the bar's to read."""
+    bar = _read(STATIC / "music-player.js")
+    assert "const remote = Boolean(castDevice) && castSession.canSendFiles;" in bar
+    send = bar.split("const sendToTv = useCallback(", 1)[1].split("}, [fetchCover]);", 1)[0]
+    assert "owner: 'music', startAt," in send
+    assert "type: cached.mime, cover," in send
+    assert "sendingRef.current = true;" in send
+    load = bar.split("if (remoteRef.current) {\n          // To the television", 1)[1]
+    assert "audio.pause();" in load.split("await audio.play();", 1)[0]
+    tick = bar.split("const tick = async () => {", 1)[1].split("const id = setInterval", 1)[0]
+    assert "castSession.owner !== 'music'" in tick
+    assert "sendingRef.current" in tick
+    assert "finishedRef.current !== remoteTrackRef.current" in tick
+    assert "String(c.idleReason || '').toLowerCase() === 'finished'" in tick
+    # The cover is found as the album card finds it, not only on the track.
+    cover = bar.split("const fetchCover = useCallback(", 1)[1]
+    cover = cover.split("}, [getConnection, tracks]);", 1)[0]
+    assert "entry.thumb_hash || (sibling && sibling.thumb_hash)" in cover
+    assert "transport.fetchMusicMeta(entry.id)" in cover
+    assert "meta.cover_thumb_hash" in cover
+    assert "castBridge.chromecastSeek(to)" in bar
+    assert "castBridge.chromecastPause() : castBridge.chromecastPlay()" in bar
+    # Stopping the cast carries the track on here; a film taking the
+    # television pauses the bar.
+    assert "if (castSession.device && castSession.owner !== 'music') setPlaying(false);" in bar
+
+
+def test_a_photo_leaves_scaled_and_upright():
+    session = _read(STATIC / "cast-session.js")
+    assert "imageOrientation: 'from-image'" in session
+    assert "const TV_WIDTH = 1920;" in session and "const TV_HEIGHT = 1080;" in session
+    assert "Math.min(1, TV_WIDTH / bitmap.width, TV_HEIGHT / bitmap.height)" in session
+    assert "await loadFile({ owner: 'photo', bytes, type: 'image/jpeg' });" in session
+    # Only the newest photo asked for is sent.
+    assert session.count("gen !== photoGen") >= 2
+
+
+def test_every_locale_names_the_slideshow():
+    for f in sorted((STATIC / "locales").glob("*.js")):
+        text = f.read_text(encoding="utf-8")
+        for key in ("photo.slideshow", "photo.slideshow_stop"):
+            assert f"'{key}':" in text, f"{f.name} lacks {key}"
diff --git a/packages/meshbay-hub/tests/test_cast_photos.py b/packages/meshbay-hub/tests/test_cast_photos.py
deleted file mode 100644
index 699e663..0000000
--- a/packages/meshbay-hub/tests/test_cast_photos.py
+++ /dev/null
@@ -1,240 +0,0 @@
-"""
-Photos on a cast receiver, and the television a session casts to.
-
-A photo takes a different road to the television than a film: no stream, one
-picture at a time, served by the relay at `/image` and loaded as a picture by
-the default media receiver. The page scales and re-encodes it first
-(cast-session.js), so what reaches the relay is a JPEG the receiver can show.
-
-The first half runs the desktop relay itself, as test_cast_subtitles.py does:
-it is plain Node with no dependencies. The photo is behind the same token as
-the stream, its address changes with every photo — a receiver handed the same
-URL twice shows what it already has — and only a picture is served as one.
-
-The second half holds the wiring: the receiver is told a photo is a photo by
-the shell, never by the page; Android accepts no URL but the relay's own; and
-a television chosen anywhere is the one a film opens on, with the player as
-its remote from the start.
-"""
-
-import json
-import re
-import shutil
-import subprocess
-from pathlib import Path
-
-import pytest
-
-PACKAGES = Path(__file__).resolve().parents[2]
-STATIC = PACKAGES / "meshbay-hub" / "src" / "meshbay_hub" / "static"
-DESKTOP = PACKAGES / "meshbay-client" / "src"
-RELAY = DESKTOP / "cast-relay.js"
-CHROMECAST = DESKTOP / "cast-chromecast.js"
-ANDROID_SRC = PACKAGES / "meshbay-android" / "app" / "src" / "main" / "kotlin"
-CAST = ANDROID_SRC / "org" / "meshbay" / "client" / "cast"
-
-
-def _read(path: Path) -> str:
-    return path.read_text(encoding="utf-8")
-
-
-RELAY_SCRIPT = r"""
-const http = require('node:http');
-const CastRelay = require(process.argv[2]);
-const get = (url) => new Promise((resolve, reject) => {
-  http.get(url, (res) => {
-    const parts = [];
-    res.on('data', (c) => parts.push(c));
-    res.on('end', () => resolve({ status: res.statusCode, headers: res.headers,
-                                  body: Buffer.concat(parts).toString('hex') }));
-  }).on('error', reject);
-});
-(async () => {
-  const relay = new CastRelay();
-  const out = {};
-  out.activeBefore = relay.active;
-  try {
-    await relay.showImage({ bytes: Buffer.from('<p>'), type: 'text/html' });
-    out.htmlRefused = false;
-  } catch { out.htmlRefused = true; }
-  out.activeAfterRefusal = relay.active;
-
-  const jpeg = Buffer.from([0xff, 0xd8, 1, 2, 0xff, 0xd9]);
-  const first = await relay.showImage({ bytes: jpeg, type: 'image/jpeg' });
-  out.activeAfterPhoto = relay.active;
-  out.firstUrl = first.url;
-  out.imageType = relay.imageType;
-  out.photo = await get(first.url);
-  out.badToken = (await get(first.url.replace(/t=[0-9a-f]+/, 't=x'))).status;
-  const second = await relay.showImage({ bytes: Buffer.from([9]), type: 'image/jpeg' });
-  out.secondUrl = second.url;
-  out.second = await get(second.url);
-
-  await relay.start({});
-  out.imageAfterFilm = relay.imageUrl;
-  await relay.stop();
-  out.imageAfterStop = relay.imageUrl;
-  console.log(JSON.stringify(out));
-})().catch((e) => { console.error(e); process.exit(1); });
-"""
-
-
-@pytest.fixture(scope="module")
-def relay_run(tmp_path_factory):
-    if shutil.which("node") is None or not RELAY.exists():
-        pytest.skip("node or the desktop client sources are not available")
-    script = tmp_path_factory.mktemp("cp") / "relay.cjs"
-    script.write_text(RELAY_SCRIPT, encoding="utf-8")
-    proc = subprocess.run(["node", str(script), str(RELAY)],
-                          capture_output=True, text=True, encoding="utf-8", timeout=30)
-    assert proc.returncode == 0, proc.stderr
-    return json.loads(proc.stdout)
-
-
-def test_a_photo_starts_the_relay_and_is_served_behind_its_token(relay_run):
-    assert relay_run["activeBefore"] is False
-    assert relay_run["activeAfterPhoto"] is True
-    photo = relay_run["photo"]
-    assert photo["status"] == 200
-    assert photo["headers"]["content-type"] == "image/jpeg"
-    assert photo["headers"]["cache-control"] == "no-store"
-    assert photo["body"] == "ffd80102ffd9"
-    assert relay_run["badToken"] == 403
-    assert relay_run["imageType"] == "image/jpeg"
-
-
-def test_every_photo_has_its_own_address(relay_run):
-    assert re.search(r"/image\?t=[0-9a-f]{32}&v=\d+$", relay_run["firstUrl"])
-    assert relay_run["secondUrl"] != relay_run["firstUrl"]
-    assert relay_run["second"]["body"] == "09"
-
-
-def test_only_a_picture_is_served_as_one(relay_run):
-    assert relay_run["htmlRefused"] is True
-    assert relay_run["activeAfterRefusal"] is False, "a refused photo starts nothing"
-
-
-def test_a_film_or_a_stop_takes_the_photo_down(relay_run):
-    assert relay_run["imageAfterFilm"] is None
-    assert relay_run["imageAfterStop"] is None
-
-
-def test_the_receiver_loads_a_photo_as_a_picture():
-    if shutil.which("node") is None or not CHROMECAST.exists():
-        pytest.skip("node or the desktop client sources are not available")
-    script = (
-        "const Module = require('node:module');"
-        "const real = Module._load;"
-        "Module._load = function (r, ...a) {"
-        "  if (r === 'bonjour-service') return { Bonjour: class {} };"
-        "  if (r === 'castv2-client') return { Client: class {}, DefaultMediaReceiver: {} };"
-        "  return real.call(this, r, ...a); };"
-        f"const {{ mediaFor }} = require({json.dumps(str(CHROMECAST))});"
-        "console.log(JSON.stringify({"
-        "  photo: mediaFor('http://x/image?t=a&v=1', null, 'image/jpeg'),"
-        "  film: mediaFor('http://x/stream.mp4?t=a', null, 'video/mp4'),"
-        "  legacy: mediaFor('http://x/stream.mp4?t=a', null) }));")
-    proc = subprocess.run(["node", "-e", script], capture_output=True, text=True,
-                          encoding="utf-8", timeout=30)
-    assert proc.returncode == 0, proc.stderr
-    out = json.loads(proc.stdout)
-    assert out["photo"]["contentType"] == "image/jpeg"
-    assert out["photo"]["streamType"] == "NONE"
-    assert "tracks" not in out["photo"]
-    assert out["film"] == out["legacy"], "a film is loaded exactly as before"
-    assert out["film"]["streamType"] == "LIVE" and out["film"]["contentType"] == "video/mp4"
-
-
-def test_the_shell_not_the_page_says_what_the_receiver_loads():
-    """The page names a URL; whether it is a photo is the relay's to say. A
-    page that could name the content type could have a television load the
-    stream URL as anything at all."""
-    main = _read(DESKTOP / "main.js")
-    load_of = main.split("const loadOf = ", 1)[1].split("\n\n", 1)[0]
-    assert "mediaUrl === castRelay.imageUrl" in load_of
-    assert "contentType: castRelay.imageType" in load_of
-    assert "contentType: 'video/mp4'" in load_of
-    assert "subtitle: null" in load_of, "a photo carries no subtitle"
-    assert main.count("loadOf(mediaUrl, subtitle)") == 2, "connect and reload both"
-
-
-def test_android_accepts_the_relays_photo_and_nothing_else():
-    if not CAST.exists():
-        pytest.skip("android sources not present")
-    channels = _read(CAST / "CastChannels.kt")
-    check = channels.split("private fun relayUrl(", 1)[1].split("\n    }", 1)[0]
-    assert "asked != ours && asked != relay.imageUrl" in check
-    assert "if (url == relay.imageUrl) relay.imageType" in channels
-    assert "url == relay.imageUrl -> null" in channels, "a photo carries no subtitle"
-    # A photo is not a cast that has to survive the screen going off.
-    image = channels.split('"cast:image" ->', 1)[1].split('\n        "', 1)[0]
-    assert "onCasting" not in image
-    relay = _read(CAST / "CastRelay.kt")
-    assert '"/image" -> serveImage(out, socket)' in relay
-    serve = relay.split("private fun serve(", 1)[1]
-    assert serve.index('query["t"] != token') < serve.index('"/image"'), "behind the token"
-    control = _read(CAST / "CastControl.kt")
-    assert "MediaInfo.STREAM_TYPE_NONE" in control
-    assert "MediaMetadata.MEDIA_TYPE_PHOTO" in control
-    # Loaded is shown: a photo never reaches PLAYING, and waiting for it
-    # would hold every photo for the full fifteen seconds.
-    load = control.split("private fun load(", 1)[1]
-    assert load.index("if (photo) return") < load.index("PLAY_WAIT_MS")
-
-
-def test_a_television_chosen_anywhere_takes_the_next_film():
-    """The player opens as the remote of a television chosen before it, the
-    cast pending until the first segment exactly as a restart is; choosing one
-    in the player keeps it for the session, and stopping there forgets it."""
-    player = _read(STATIC / "video-player.js")
-    assert ("const [autoCast] = useState(() => "
-            "(castSession.supported ? castSession.device : null));") in player
-    assert "useState(Boolean(autoCast))" in player
-    assert "castActiveRef = useRef(Boolean(autoCast))" in player
-    assert "castRestartPendingRef = useRef(Boolean(autoCast))" in player
-    assert "castDeviceRef = useRef(autoCast)" in player
-    assert "useState(autoCast ? autoCast.name : null)" in player
-    stop = player.split("const stopCast = async () => {", 1)[1].split("};", 1)[0]
-    assert "castSession.forget()" in stop
-    assert "castSession.choose(d);" in player
-
-
-def test_the_cast_button_is_where_the_media_are():
-    """Videos' toolbar, the Photos landing and a photo album's bar are drawn by
-    the group page and the search page alike, so one button in each covers
-    both. On the landing the button keeps a toolbar Search would otherwise
-    hide."""
-    videos = _read(STATIC / "video-app.js")
-    assert "<${CastButton} />" in videos.split('<div class="video-toolbar">', 1)[1]
-    photos = _read(STATIC / "photos-app.js")
-    landing = photos.split("function PhotosApp(", 1)[1]
-    assert "(!hideFilter || castSession.supported) && html`" in landing
-    assert "<${CastButton} />" in landing.split('<div class="photo-toolbar">', 1)[1]
-    album = photos.split("function AlbumView(", 1)[1]
-    assert "<${CastButton}" in album
-    lightbox = photos.split("function Lightbox(", 1)[1].split("function AlbumView(", 1)[0]
-    assert '<${CastButton} variant="overlay"' in lightbox
-    assert "if (castDevice && blobUrl && blob) showPhoto(blob);" in lightbox
-    # The group page draws them through the app registry, the search page
-    # imports them: the same components either way.
-    registry = _read(STATIC / "apps.js")
-    search = _read(STATIC / "search-page.js")
-    for page in (registry, search):
-        assert "VideoApp" in page and "PhotosApp" in page
-
-
-def test_a_photo_leaves_scaled_and_upright():
-    session = _read(STATIC / "cast-session.js")
-    assert "imageOrientation: 'from-image'" in session
-    assert "const TV_WIDTH = 1920;" in session and "const TV_HEIGHT = 1080;" in session
-    assert "Math.min(1, TV_WIDTH / bitmap.width, TV_HEIGHT / bitmap.height)" in session
-    assert "'image/jpeg'" in session
-    # Only the newest photo asked for is sent.
-    assert session.count("gen !== photoGen") >= 2
-
-
-def test_every_locale_names_the_slideshow():
-    for f in sorted((STATIC / "locales").glob("*.js")):
-        text = f.read_text(encoding="utf-8")
-        for key in ("photo.slideshow", "photo.slideshow_stop"):
-            assert f"'{key}':" in text, f"{f.name} lacks {key}"