From a79a38a22a6145c475f50eeadb79b451aee31c11 Mon Sep 17 00:00:00 2001
From: Christophe Besson <cbesson@gmail.com>
Date: Wed, 16 Sep 2026 10:21:58 +0200
Subject: docs: playlists — storage split, queue ops, and the UI design
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The 256 KB cap contradicted its own worked example; entries were also
missing `size`/`name`, without which a stored track cannot be fetched
at all. Storage becomes a manifest plus one blob per playlist,
compressed, so starring a track no longer rewrites the collection.

Adds the UI pass that was missing: the queue verbs, the menus, and the
one real code change behind them — the player's queue can today only
be replaced, not appended to.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
---
 docs/MESHBAY_DESIGN.md |   57 ++-
 docs/playlists.md      | 1096 +++++++++++++++++++++++++++++++++++-------------
 2 files changed, 847 insertions(+), 306 deletions(-)

diff --git a/docs/MESHBAY_DESIGN.md b/docs/MESHBAY_DESIGN.md
index 2b6d1ac..aaa232c 100644
--- a/docs/MESHBAY_DESIGN.md
+++ b/docs/MESHBAY_DESIGN.md
@@ -32,7 +32,7 @@
 | **this document** | the architecture, the trust model, and the reason each decision is what it is |
 | `MESHBAY_NODE_PROTOCOL.md` | the MNP wire format, message by message |
 | `transfers-v1.md` | the transfer system's failure-mode analysis, kept because a synthesis cannot carry "every way a slot can be lost" |
-| `playlists.md` | the playlist design in full — decided, not built (§9.10) |
+| `playlists.md` | the playlist design and its interface in full — decided, not built (§9.10) |
 | `cast-smart-tv.md` | the DLNA/UPnP device backend — designed, not built (§11.4) |
 | `WINDOWS-PORT.md` | the Windows port's audit and packaging detail (§11.2) |
 | `PACKAGING-GUIDE.md`, `HTTPS.md`, `MAIL-SERVER.md`, `windows-build.md` | installation and server operations |
@@ -2327,10 +2327,23 @@ removed from the hub, and it is the same rule that keeps resume positions local:
 *nothing new learns what you watch.* An encrypted blob on the hub is technically
 trivial and is still refused.
 
-It lives on the node instead, as **an opaque per-account blob in `bundles.db`** —
-the same shape as the keypair bundle, which the node already stores and cannot
-read. **No new trust boundary**: the node is not asked to hold a kind of thing it
-does not already hold for that same account.
+It lives on the node instead, as **opaque per-account blobs in `bundles.db`** — the
+same shape as the keypair bundle, which the node already stores and cannot read.
+**No new trust boundary**: the node is not asked to hold a kind of thing it does
+not already hold for that same account.
+
+**One blob per playlist, plus a small manifest** — not one blob for the collection,
+and the reason is write amplification rather than size. Under a single blob,
+starring one track rewrites and re-uploads the whole collection to every node
+reached; split, it rewrites that one playlist. The manifest — names, revisions,
+tombstones, counts, a few KB — is also the only thing every menu needs, so "add to
+playlist" draws instantly with every node offline, and a body is fetched only when
+its playlist is opened or played. Blobs are **compressed before sealing and padded
+after**: the payload is repetitive enough to be worth a factor of three, and the
+padding is what stops a ciphertext length from counting somebody's tracks. The node
+caps each blob and the account's total, and **refuses rather than truncates** — a
+truncating cap silently loses tracks, which is the failure the whole design exists
+to prevent.
 
 **The key is the one thing that must not be got wrong.** Identity keys are per node
 (§3.2), so a blob encrypted under one is unreadable from every other node — the
@@ -2340,14 +2353,36 @@ is the bundle key, so `playlist_key = HKDF(bundle_key, info =
 Argon2 run, and a purpose-separated subkey rather than the bundle key reused with a
 different AAD (§4.4's rule). The nonce is 96 random bits and never a counter, for
 exactly the reason chat's is (§4.5): two devices of one account derive the *same*
-key, which is the point.
+key, which is the point. The AAD names the blob's *kind*, so one playlist's body
+cannot be served in place of another's.
 
 **Merge is the hard third, and the granularity is what makes it tractable.** The
-unit is **one playlist, not the collection**; revision counters order writes, never
-the wall clock; and **a deletion is a tombstone, never an absence** — an absence is
-indistinguishable from a device that has not seen the addition yet. A node that is
-offline for a month therefore cannot corrupt anything: it holds an older revision of
-some playlists and is overwritten per playlist, not wholesale.
+unit is **one playlist, not the collection** — which the per-playlist blob now
+makes true of the storage as well, so two devices editing two playlists do not even
+write the same row. Revision counters order writes, never the wall clock; and **a
+deletion is a tombstone, never an absence** — an absence is indistinguishable from a
+device that has not seen the addition yet. A node that is offline for a month
+therefore cannot corrupt anything: it holds an older revision of some playlists and
+is overwritten per playlist, not wholesale.
+
+**The interface is a menu inside Music, not a page.** Music's player is already
+persistent at shell level and already holds a queue that crosses groups; *loading* a
+playlist replaces that queue, and below that call a playlist and an album are
+indistinguishable — so auto-advance, shuffle and prefetch are unchanged by
+construction. The one genuine code change is that the queue can today only be
+*replaced*: "play next" and "add to queue" require it to become appendable, which
+makes it a small reducer rather than three pieces of component state. Everything
+else is a context menu on a cover or a track row, and one button in Music's sticky
+toolbar. Because Music is mounted by both the group page and the Search page
+(§9.11), a playlist built inside a group is managed from the consolidated view with
+no second surface and no application-registry entry.
+
+**Unavailability is answered at play time, not at add time.** Whether a group is
+reachable is only knowable by dialing, and refusing to add a track because its node
+is off tonight loses the user's intent permanently to a condition that lasts an
+evening. So adding never dials; playback skips, distinguishing a file that will not
+decode (a property of that file) from a group that does not answer (a property of
+that group, whose tracks are then skipped together).
 
 **It adds no dialing and no new streaming path.** Sync rides connections the client
 already makes, and playback is unchanged (§9.8).
diff --git a/docs/playlists.md b/docs/playlists.md
index 485011a..ecbbac4 100644
--- a/docs/playlists.md
+++ b/docs/playlists.md
@@ -1,23 +1,22 @@
 # MeshBay — Playlists (design)
 
 > Status: **proposal**, not implemented. This was deferred out of the Music
-> application's design,
-> which deferred it for the right reason: *"a genuinely new category of
-> per-account node state, not covered by anything E9 already enumerates —
-> needs its own design pass (ownership, sync across devices, whether it's
-> node-local or something else)"*. This document is that pass.
+> application's design, which deferred it for the right reason: *"a genuinely
+> new category of per-account node state, not covered by anything E9 already
+> enumerates — needs its own design pass (ownership, sync across devices,
+> whether it's node-local or something else)"*. This document is that pass.
 >
 > Read `MESHBAY_DESIGN.md` §9.8 first — Music is built, and this adds nothing
-> to its playback path. Read §9.11 second: the
-> cross-group consolidation this feature needs already exists there, and
-> most of the work is recognising that.
+> to its playback *path*. Read §9.11 second: the cross-group consolidation
+> this feature needs already exists there, and most of the work is
+> recognising that.
 >
 > **Scope, settled before writing this:** a playlist belongs to **one
 > account** and is never shared with other group members. That answer is what
-> keeps §5 small; see §10 for what changes if it is ever reversed.
+> keeps §6 small; see §13 for what changes if it is ever reversed.
 >
-> Follows the project convention: every claim names the adversary it holds
-> against (§9).
+> Follows the project convention: every claim names the adversary or the
+> failure it holds against (§12).
 
 ---
 
@@ -28,36 +27,64 @@ turn up on that person's other devices — and so that one playlist may hold
 albums from **several different groups on several different nodes**, the way
 the Search page already searches a consolidated view. With the constraint,
 stated up front, that nodes go offline for an evening or for a month and that
-this must not corrupt anything.
+this must not corrupt anything. And — added after the first draft, and now
+half of this document — **a user interface**: the queue verbs (play, play
+next, enqueue) that a music player is expected to have, a way to build a
+playlist from what is on screen, a way to manage playlists from one button,
+and none of it breaking the album auto-advance and prefetch that already
+work.
+
+## 0.1 What changed from the first draft, and why
+
+The first draft answered the storage question and stopped. Three things in it
+were wrong or missing, and they are corrected here rather than patched:
+
+| | First draft | Now | §  |
+|---|---|---|---|
+| Size | one blob for everything, capped at 256 KB | **manifest + one blob per playlist**, compressed, stored as a BLOB; caps per unit | §4, §5 |
+| The stored track reference | "takes it unchanged" into `onPlayQueue` | **it does not** — `size` and `name` are missing and both are required to fetch a track at all | §5.3 |
+| UI | one route `/playlists` and a sidebar entry | **dropped.** A menu in Music's sticky toolbar, which Search → Music inherits for free | §9, §13 O7 |
+
+The 256 KB figure contradicted its own worked example: the draft estimated
+1 000 tracks at ~200 bytes as "~200 KB", against a cap applied to `blob_enc`,
+which was a **base64 TEXT** column — so its own example was already ~267 KB on
+the wire, over a cap it declared generous. §4 redoes the arithmetic with the
+fields that actually have to be there.
 
 ---
 
 ## 1. What this design does not reopen
 
-- **Views over the index, never a catalogue** (`MESHBAY_DESIGN.md` §6.5, §9.1,
-  draft-v6 §2.7). A playlist is a list of *references*; it creates no second
-  identity for a file and no server-side database of content.
-- **Nothing about content reaches the hub** (H7, draft-v6 §2.5). §3.1.
-- **No new streaming path.** `MESHBAY_DESIGN.md` §9.8 stands untouched: a track is
-  fetched through `pipelinedDownload` and handed to `<audio>`. Playlists add
-  no node-side playback code whatsoever.
-- **Node-side derived data lives in the node's own `data_dir`**, never beside
-  a shared file (`MESHBAY_DESIGN.md` §6.5). The blob in §3.3 goes in `bundles.db`.
+- **Views over the index, never a catalogue** (`MESHBAY_DESIGN.md` §6.5, §9.1).
+  A playlist is a list of *references*; it creates no second identity for a
+  file and no server-side database of content.
+- **Nothing about content reaches the hub** (H7). §3.1.
+- **No new streaming path.** `MESHBAY_DESIGN.md` §9.8 stands untouched: a track
+  is fetched through `pipelinedDownload` and handed to `<audio>`. Playlists add
+  no node-side playback code whatsoever, and no change to transcode, chunking,
+  or the GEK.
+- **Node-side derived data lives in the node's own `data_dir`**, never beside a
+  shared file (`MESHBAY_DESIGN.md` §6.5). The blobs in §3.3 go in `bundles.db`.
 - **Identity keys are per node** (`MESHBAY_DESIGN.md` §3.2). §3.4 exists
   entirely because of this, and getting it wrong is the fastest way to ship a
   playlist that cannot be read from the second device it was invented for.
+- **The player bar stays where it is.** It is already at shell level in
+  `app.js`, already resolves a connection per track from `entry.groupId`, and
+  already crosses groups within one queue. The cross-group requirement reads
+  like the hard part and is in fact already built.
 
 ---
 
-## 2. Three problems, and only one of them is hard
+## 2. Four problems, and only two of them are hard
 
 | | Problem | Where it is solved |
 |---|---|---|
-| A | Somewhere durable to put a few KB per account | §3 — several acceptable answers, one clearly best |
-| B | How to **name** a track that lives in one group on one node, inside a list that spans several | §4.2 — where the silent failures live |
-| C | Reconciling N copies when nodes are ON and OFF | §5 — the stated fear, and it is well founded *only* for the wrong granularity |
+| A | Somewhere durable to put a few hundred KB per account | §3 — several acceptable answers, one clearly best |
+| B | How to **name** a track that lives in one group on one node, inside a list that spans several | §5.3 — where the silent failures live |
+| C | Reconciling N copies when nodes are ON and OFF | §6 — the stated fear, well founded *only* for the wrong granularity |
+| D | A queue that can be **appended to**, not only replaced | §8 — the player's queue is three `useState`s reset wholesale; that is the one real code change |
 
-The request reads as a storage problem. Storage is the easy third of it.
+The request reads as a storage problem. Storage is the easy quarter of it.
 
 ---
 
@@ -66,14 +93,14 @@ The request reads as a storage problem. Storage is the easy third of it.
 ### 3.1 Not the hub, and the rule is narrower than "nothing on the hub"
 
 The hub *does* hold small per-account state: `user_preferences`
-(`db/models.py:303`), behind an allowlist of keys that already includes
+(`db/models.py:302`), behind an allowlist of keys that already includes
 `music_keep_screen_on` and `default_tab:<group_id>`. So the operative rule is
 not "the hub stores nothing about a user". It is:
 
 > **No content metadata on the hub.**
 
 A playlist is, literally, a list of blake3 hashes of private-group files —
-plus, if it is to render while nodes are offline (§4.2), their titles and
+plus, if it is to render while nodes are offline (§5.3), their titles and
 artists. That is the exact object H7 removed from the hub, and it is what
 `CLAUDE.md` already pins one size smaller for the video resume position:
 *"nothing new learns what you watch"*.
@@ -91,20 +118,20 @@ argument.
 If a future need makes hub involvement genuinely attractive, the only
 acceptable shape is a **version vector** — `playlists_rev: 7` in
 `user_preferences`, telling a client that some node is stale — never the
-payload. Even that is probably not worth its own migration; §6 gets the same
+payload. Even that is probably not worth its own migration; §7 gets the same
 result with no hub change at all.
 
 ### 3.2 Not node-to-node
 
 Refused, and not on cost grounds. Nodes do not know each other, share no
-authenticated channel, and `replication.py` is legacy public-content code
-that has nothing to do with this. Beyond the protocol that would have to be
-invented, it leaks the thing this architecture is most careful about:
-node A would learn that this account also uses node B — that two unrelated
-operators host the same person. Per-node identity exists precisely so that
-this correlation is unavailable (`MESHBAY_DESIGN.md` §3.2).
+authenticated channel, and `replication.py` is legacy public-content code that
+has nothing to do with this. Beyond the protocol that would have to be
+invented, it leaks the thing this architecture is most careful about: node A
+would learn that this account also uses node B — that two unrelated operators
+host the same person. Per-node identity exists precisely so that this
+correlation is unavailable (`MESHBAY_DESIGN.md` §3.2).
 
-### 3.3 The node, as an opaque per-account blob — a shape already built
+### 3.3 The node, as opaque per-account blobs — a shape already built
 
 The node already stores an encrypted per-account object it cannot read: the
 keypair bundle (`bundle_store.py`, table `keypair_bundles`, MNP ops
@@ -118,22 +145,36 @@ A new table in the same `bundles.db`:
 ```sql
 CREATE TABLE IF NOT EXISTS user_blobs (
     user_id     TEXT NOT NULL,
-    kind        TEXT NOT NULL,          -- "playlists" today; the column is the
-                                        -- reason a second one needs no migration
+    kind        TEXT NOT NULL,          -- "playlists" (the manifest), or
+                                        -- "playlist:<id>" (one playlist's tracks)
     rev         INTEGER NOT NULL,
-    blob_enc    TEXT NOT NULL,
-    blob_enc_recovery TEXT,             -- reserved, §10 O2 — see below
+    blob_enc    BLOB NOT NULL,          -- NOT TEXT — see below
+    blob_enc_recovery BLOB,             -- reserved, §13 O2
     stored_at   TEXT NOT NULL DEFAULT (datetime('now')),
     PRIMARY KEY (user_id, kind)
 );
 ```
 
+Two deliberate differences from `keypair_bundles`, each of which is a mistake
+avoided rather than a preference:
+
+- **`BLOB`, not `TEXT`.** `keypair_bundles.bundle_enc` is base64 TEXT because
+  it holds a few hundred bytes and nobody will ever notice the 33 % tax. This
+  table holds hundreds of KB, where a third is not a rounding error. The
+  transport already carries msgpack `bin` (`transport.js:3571` handles it
+  explicitly), and `aiosqlite` binds `bytes` natively, so base64 buys nothing
+  here and costs a third of every write.
+- **`kind` is a namespace, not an enum.** `"playlists"` is the manifest;
+  `"playlist:<uuid>"` is one playlist's tracks. The allowlist in §8.2 is a
+  *pattern*, not a literal set, and that is the whole reason the split in §4
+  costs no second table.
+
 `blob_enc_recovery` is declared now and left NULL. `bundle_store.py` already
-carries `_migrate_keypair_recovery` — a `PRAGMA table_info` dance — for
-exactly this column added to exactly this kind of table one release late.
-`CREATE TABLE IF NOT EXISTS` never adds a column, which is the node-local
-twin of the `create_all()` lesson in `CLAUDE.md`. Declaring the slot costs
-nothing today and removes the migration entirely.
+carries `_migrate_keypair_recovery` — a `PRAGMA table_info` dance — for exactly
+this column added to exactly this kind of table one release late. `CREATE TABLE
+IF NOT EXISTS` never adds a column, which is the node-local twin of the
+`create_all()` lesson in `CLAUDE.md`. Declaring the slot costs nothing today
+and removes the migration entirely.
 
 ### 3.4 The key — the one thing that must not be got wrong
 
@@ -152,38 +193,127 @@ playlist_key = HKDF-SHA256(bundle_key_v2, info = "meshbay:playlists:v1")
 Three consequences, each of which is a line of code somewhere:
 
 - **`deriveEncryptionKey` must return an HKDF handle as well as the AES-GCM
-  one.** Today it imports the 32 Argon2 bytes non-extractably as `AES-GCM`
-  with `['encrypt','decrypt']`, from which nothing can be derived. Import the
-  *same* `out.hash` a second time as `HKDF` with `['deriveKey']`. One Argon2
-  run, two handles, no extra cost on the 650 ms sign-in path. Do **not** add a
-  second Argon2 call, and do **not** encrypt playlists directly under the
-  bundle key with a different AAD: `groupbox.py` already sets the convention
-  ("*Never reuse `chunk_key_aes` with a pseudo-file for this*") and
-  purpose-separated subkeys are what it looks like here.
-- **v2 only.** `bundleKey` is `{v2, v1}` so that a bundle written before the
-  KDF changed can still be opened. Playlists are new; there is no legacy blob
-  and therefore no v1 branch. One less thing that can silently take the wrong
-  fork.
+  one.** Today (`keyderive.js:154`) it imports the 32 Argon2 bytes
+  non-extractably as `AES-GCM` with `['encrypt','decrypt']`, from which nothing
+  can be derived. Import the *same* `out.hash` a second time as `HKDF` with
+  `['deriveKey']`. One Argon2 run, two handles, no extra cost on the 650 ms
+  sign-in path. Do **not** add a second Argon2 call, and do **not** encrypt
+  playlists directly under the bundle key with a different AAD: `groupbox.py`
+  already sets the convention ("*Never reuse `chunk_key_aes` with a pseudo-file
+  for this*") and purpose-separated subkeys are what it looks like here.
+- **v2 only.** `bundleKey` is `{v2, v1}` so that a bundle written before the KDF
+  changed can still be opened. Playlists are new; there is no legacy blob and
+  therefore no v1 branch. One less thing that can silently take the wrong fork.
 - **The nonce is 96 random bits, never a counter.** Two devices of one account
-  derive the *same* playlist key — that is the whole point — so a counter
-  would repeat. This is the same reasoning already recorded for chat subkeys
-  in `CLAUDE.md`'s module table, and it is safe for the same reason.
+  derive the *same* playlist key — that is the whole point — so a counter would
+  repeat. This is the same reasoning already recorded for chat subkeys in
+  `CLAUDE.md`'s module table, and it is safe for the same reason.
+
+A passphrase change re-derives the key and every blob must be re-encrypted on
+the next write, exactly as the keypair bundle already is ("*re-encrypted on the
+next backup*"). With the split of §4 that is now N+1 writes rather than one —
+do them lazily, on each playlist's next write, not in a loop at sign-in.
+
+**AAD** = `"user_blob|<kind>|<user_id>"`, mirroring `groupbox.associated_data`.
+`<kind>` is the full namespaced kind, so a body sealed for playlist A cannot be
+served in place of playlist B's — which a bare `"playlists"` AAD would have
+allowed, and which is a real substitution now that there is more than one row.
+It does not, and cannot, prevent rollback — §6.4.
+
+---
+
+## 4. Size — the first draft's arithmetic, redone
+
+### 4.1 What an entry actually costs
+
+§5.3 settles which fields have to be stored. With short msgpack keys:
+
+| field | bytes |
+|---|---|
+| `id` (blake3 hex) | 65 |
+| `g` (group UUID, 36 chars) | 37 |
+| `n` (filename) | ~31 |
+| `p` (path) | ~56 |
+| `t` (display title) | ~26 |
+| `a` (artist) | ~16 |
+| `b` (album) | ~23 |
+| `s` (size), `d` (duration), `tn`, `hv` | ~10 |
+| 11 keys + map header | ~34 |
+| **total** | **~300 B** |
+
+The first draft said 200 B, from a field list that could not play a track.
+
+### 4.2 Three realistic accounts
+
+| | entries | plaintext | base64 (draft) | deflate + BLOB (this draft) |
+|---|---|---|---|---|
+| draft's own example | 1 000 | 300 KB | **400 KB** — over its own 256 KB cap | ~100 KB |
+| ordinary user: Favourites 2 000 + 15 lists | ~4 250 | 1.3 MB | 1.7 MB | ~430 KB |
+| heavy user | 20 000 | 6 MB | 8 MB | ~2 MB |
+
+So: **the doubt was correct, and by roughly an order of magnitude.** 256 KB is
+not enough for one realistic Favourites list, let alone a collection.
+
+### 4.3 Four fixes, in order of how much they matter
+
+**1. Split the storage per playlist (§3.3's `kind` namespace).** This is the
+one that matters, and not mainly for the cap. Under one blob, starring a single
+track rewrites and re-uploads *the whole collection* — 1.7 MB, to every node
+reached, for one star. Twenty stars in an evening is 34 MB over WebRTC per node.
+Split, the same star rewrites Favourites (~200 KB) plus a ~3 KB manifest. The
+merge unit was already one playlist (§6.1); this makes the *storage* unit agree
+with it, which is also why the merge gets simpler rather than harder.
+
+It has a second payoff, bigger than it looks: the **manifest alone is enough to
+draw every menu in §9**. "Add to playlist ▸" lists names, and names are in the
+manifest — a few KB, always in IndexedDB, rendered instantly with every node
+offline and no body fetched. Under one blob that menu waits on megabytes.
+
+**2. Compress before sealing.** `CompressionStream('deflate-raw')` — native in
+Chromium, Firefox 113+, Safari 16.4+, and therefore in the Electron build; no
+dependency, and the project has no compression library today (`zipstream.js`
+deliberately stores rather than deflates, for a different reason). The shape is
+about as compressible as data gets: the 11 keys repeat every entry, `group_id`
+repeats across the whole list, and path prefixes repeat per album. 3× is
+conservative for this; 4× is typical.
+
+  **Order is compress → pad → seal, never seal → compress.** Ciphertext does not
+  compress, and the padding must be inside the AEAD.
 
-A passphrase change re-derives the key and the blob must be re-encrypted on
-the next write, exactly as the keypair bundle already is ("*re-encrypted on
-the next backup*").
+**3. `BLOB` not `TEXT`** (§3.3) — a third of every write, free.
 
-**AAD** = `"user_blob|playlists|<user_id>"`, mirroring
-`groupbox.associated_data`. It binds the ciphertext to its owner and its
-kind. It does not, and cannot, prevent rollback — §5.4.
+**4. Caps that refuse, never truncate.** A truncating cap silently loses tracks,
+which is the failure this whole document exists to prevent.
+
+| limit | value | enforced by |
+|---|---|---|
+| manifest (`kind = "playlists"`) | 64 KB sealed | node |
+| one body (`kind = "playlist:<id>"`) | 1 MB sealed ≈ 10 000 tracks | node |
+| all rows for one account on one node | 8 MB | node |
+| tracks per playlist | 10 000 | client, before sealing |
+| playlists per account | 200 | client, before sealing |
+
+The client limits exist so the ordinary case produces a sentence in the UI
+rather than an MNP error; the node limits exist because a client is not
+trusted to hold to them, and this is an unbounded write primitive pointed at
+someone else's disk. Noted in passing, and out of scope here:
+`_do_keypair_bundle_store` (`webrtc_server.py:1113`) has **no cap at all**
+today. Worth its own line somewhere.
+
+**Padding.** Pad the compressed plaintext up to the next 4 KB before sealing.
+The length otherwise tells the operator roughly how many tracks this account
+has collected, and — once compression is in — roughly how repetitive its paths
+are. Cheap, and it is the only metadata this design leaks to a node that the
+node cannot already see. See §12 for the chosen-plaintext angle and why it is
+named and then dismissed.
 
 ---
 
-## 4. The data model
+## 5. The data model
 
-### 4.1 The blob
+### 5.1 The manifest — `kind = "playlists"`
 
-Plaintext-before-sealing, msgpack (same encoding as everything else on MNP):
+Small, always resident, and the only thing every menu needs:
 
 ```
 {
@@ -191,11 +321,12 @@ Plaintext-before-sealing, msgpack (same encoding as everything else on MNP):
   "playlists": {
     "<playlist_id>": {
       "name":       "Evening",
-      "rev":        7,
+      "rev":        7,               -- of the manifest entry
+      "body_rev":   41,              -- of the body blob, §5.2
       "device":     "<device_pk_ed25519, first 16 hex>",
-      "updated_at": 1757000000,        -- display only, never a merge input
+      "updated_at": 1757000000,      -- display only, never a merge input
       "deleted":    false,
-      "tracks": [ <entry>, ... ]
+      "count":      312              -- display only; the body is authoritative
     },
     ...
   }
@@ -205,163 +336,208 @@ Plaintext-before-sealing, msgpack (same encoding as everything else on MNP):
 `playlist_id` is a client-generated UUID, with one reserved value:
 `"favorites"`. **Favourites is a playlist**, not a second mechanism — deciding
 that now is what stops a parallel store being built next to this one in three
-months.
+months. It is *implicit*: never created by the user, materialised on first use,
+always first in every picker (as asked), and **it cannot be deleted** (§9.3).
+Emptying it is fine. Refusing the delete outright is what keeps §6.3's
+tombstone rule free of an exception, and a tombstone rule with an exception is
+how §6.3's defect ships.
+
+### 5.2 A body — `kind = "playlist:<id>"`
+
+```
+{ "v": 1, "id": "<playlist_id>", "rev": 41, "device": "...",
+  "tracks": [ <entry>, ... ] }
+```
+
+Array order *is* playlist order. `rev` here is the body's own, and the
+manifest's `body_rev` is a copy of it — a client that sees a manifest naming
+`body_rev: 41` while holding body `rev: 39` knows to fetch without fetching to
+find out. A body whose manifest entry is `deleted` is dropped locally and
+`user_blob_delete`d on each node as it is reached; the tombstone in the
+manifest is what survives, not the body.
 
-### 4.2 A track reference, and why each field is there
+### 5.3 A track reference — and the field the first draft omitted
 
 ```
-{ "group_id": ..., "file_id": <blake3 hex>, "hash_version": 1|2,
-  "path": "Some Artist/An Album/03 - A Track.flac",
-  "title": ..., "artist": ..., "album": ..., "duration": 214 }
+{ "id": <blake3 hex>, "g": <group_id>, "hv": 1|2,
+  "n": "03 - A Track.flac",          -- filename
+  "s": 41238711,                     -- bytes
+  "p": "Some Artist/An Album",       -- directory path, group-relative
+  "t": "A Track", "a": "Some Artist", "b": "An Album",
+  "d": 214, "tn": 3 }
 ```
 
-A bare hash is not enough, and each field prevents a specific failure:
-
-- **`group_id`** — the player resolves its connection per track from
-  `entry.groupId` (`music-player.js:288`). Without it there is nothing to
-  dial, and a `file_id` alone has no meaning outside a group.
-- **`title` / `artist` / `album` / `duration`, denormalised** — this is not
-  redundancy, it is the core of the design. With them a playlist renders
-  **completely** with every node offline, unplayable entries greyed out, in
-  the same spirit as the Search page reporting its `unreachable` list rather
-  than failing. Without them, an offline playlist is a column of hex strings —
-  and *that* is the incoherence the request is worried about. It is a
-  display problem, and it is solved by copying four small strings.
-- **`hash_version`** — the index already has two hashing schemes
-  (`protocol.py:292`: 1 = whole file, 2 = 45 MB sample). A re-hash would
-  orphan every entry in every playlist, silently and all at once.
-- **`path`** — content addressing survives a move; a path survives a
-  re-encode. Keeping both means either can repair the other: on a sight of
-  the live index, an entry whose `file_id` is absent but whose `path` matches
-  has its id rewritten in place (and vice versa), once, on the client.
-
-Rehydration is by design cheap: a playlist entry is a subset of the
-`IndexEntry`-plus-`groupId` shape the player already consumes, so
-`onPlayQueue(tracks, startIndex)` takes it unchanged.
-
-**Availability bonus, close to free.** `source-merge.js` exists because the
-same content appears in more than one group. At play time, if the entry's own
-`group_id` has no reachable node but the same `file_id` appears in another
-cached index whose node is up, play it from there. That is a global playlist
-that heals itself when one operator's machine is off, reusing the
-fold-on-content-hash logic already written for Search. Default on; see §9 for
-the one thing it changes.
-
-### 4.3 Size
-
-A thousand tracks at ~200 bytes each is ~200 KB before compression. That is
-small, and it is also an unbounded write primitive pointed at someone else's
-disk, so:
-
-- The node **caps and refuses**, never truncates. 256 KB of `blob_enc` is
-  generous for the shape above. (Noted in passing: `_do_keypair_bundle_store`
-  (`webrtc_server.py:1056`) has no cap at all today. Out of scope here, worth
-  its own line somewhere.)
-- The client **pads the plaintext up to the next 4 KB** before sealing. The
-  ciphertext length otherwise tells the operator roughly how many tracks this
-  account has collected. Cheap, and it is the only metadata this design leaks
-  to a node that the node cannot already see.
+Each field prevents a specific failure:
+
+- **`g`** — the player resolves its connection per track from `entry.groupId`
+  (`music-player.js:292`). Without it there is nothing to dial, and a hash alone
+  has no meaning outside a group.
+- **`s` and `n` — the correction.** The first draft's entry had neither, and
+  claimed the result was droppable into `onPlayQueue` unchanged. It is not.
+  `fetchTrackBlob` (`music-player.js:289`) computes
+  `Math.ceil(entry.size / CHUNK_SIZE)` to know how many chunks to ask for, calls
+  `guessMime(entry.name)` for the blob type, and tests `entry.name` against
+  `NEEDS_TRANSCODE_RE` to decide whether a `.wma`/`.mpc` needs the node-side
+  conversion first. **Without `s` a playlist entry cannot be downloaded at
+  all**, and without `n` it is downloaded and then handed to `<audio>` with the
+  wrong MIME, or a WMA is handed over raw and fails to decode in every browser.
+  The symptom is "playlists don't play", found at integration time and nowhere
+  earlier.
+- **`t` / `a` / `b` / `d` / `tn`, denormalised** — this is not redundancy, it is
+  the core of the design. With them a playlist renders **completely** with every
+  node offline, unplayable entries greyed, in the same spirit as the Search page
+  reporting its `unreachable` list rather than failing. Without them, an offline
+  playlist is a column of hex strings. A display problem, solved by copying four
+  small strings.
+- **`hv`** — the index already has two hashing schemes (`protocol.py:297`:
+  1 = whole file, 2 = 45 MB sample). A re-hash would orphan every entry in every
+  playlist, silently and all at once.
+- **`p`** — content addressing survives a move; a path survives a re-encode.
+  Keeping both means either can repair the other: on a sight of the live index,
+  an entry whose `id` is absent but whose `p`+`n` match has its id rewritten in
+  place (and vice versa), once, on the client.
+
+**Rehydration, and the whitelist that is not optional.** A stored entry is
+mapped to the player's entry shape (`id, name, path, size, duration,
+display_title, artist, album, track_no, hash_version, groupId`) on load, and
+the reverse map on save is a **strict field whitelist**. The entries the UI
+hands over carry live junk: `_tRef` and `_gRef` (a transport and a CryptoKey,
+attached by the Search page's merge), `_origPath`, and whatever else a future
+view hangs on them. msgpack-encoding a transport object throws at best; storing
+a stale one and reading it back a week later is worse, because it looks like a
+connection and is not. Whitelist on the way in, in `playlists.js`, once.
+
+**Availability bonus, close to free.** `source-merge.js` exists because the same
+content appears in more than one group. At play time, if the entry's own `g` has
+no reachable node but the same `id` appears in another cached index whose node
+is up, play it from there. That is a global playlist that heals itself when one
+operator's machine is off, reusing the fold-on-content-hash logic already
+written for Search. Default on; see §12 for the one thing it changes.
 
 ---
 
-## 5. Merge — the part that has to be right
+## 6. Merge — the part that has to be right
 
-The stated fear is correct **for a single blob under last-writer-wins**: node
-A is off while an edit is made, node B is off while the next one is, and one
-edit disappears with nothing to show for it. Four rules remove it.
+The stated fear is correct **for a single blob under last-writer-wins**: node A
+is off while an edit is made, node B is off while the next one is, and one edit
+disappears with nothing to show for it. Four rules remove it.
 
-### 5.1 The unit is a playlist, not the collection
+### 6.1 The unit is a playlist, not the collection
 
-The blob is a map keyed by `playlist_id`, and merging is per key. Two
-playlists edited on two devices never collide, which is the overwhelmingly
-common case for one person with two or three devices.
+The manifest is a map keyed by `playlist_id` and merges per key; bodies are
+separate rows and merge one against one. Two playlists edited on two devices
+never collide, which is the overwhelmingly common case for one person with two
+or three devices. §4.3's split means this is now true of the *storage* as well
+as the merge, so two devices editing two playlists do not even write the same
+row.
 
-### 5.2 `rev`, never the wall clock
+### 6.2 `rev`, never the wall clock
 
-Each playlist carries a monotonic `rev` and the `device` that last wrote it.
-Merge takes the higher `rev`; a tie is broken by the lexicographically
-smaller `device`, so every device reaches the same answer without talking to
-any other. `updated_at` is carried for display and is **never** read by the
-merge — clocks across devices are not trustworthy, and a clock-based merge
-fails roughly one time in twenty, which is the frequency at which this
-codebase's history says a defect ships.
+Each manifest entry and each body carries a monotonic `rev` and the `device`
+that last wrote it. Merge takes the higher `rev`; a tie is broken by the
+lexicographically smaller `device`, so every device reaches the same answer
+without talking to any other. `updated_at` is carried for display and is
+**never** read by the merge — clocks across devices are not trustworthy, and a
+clock-based merge fails roughly one time in twenty, which is the frequency at
+which this codebase's history says a defect ships.
 
-### 5.3 A deletion is a tombstone, never an absence
+### 6.3 A deletion is a tombstone, never an absence
 
-`deleted: true`, kept. Absence must mean "this copy is older than the one
-that created it". Otherwise a node rehomed after three weeks **resurrects
-every deleted playlist** — this is the single most likely defect in the whole
-design, it looks like a sync working correctly right up until it doesn't, and
-it deserves its own named test. Tombstones are collected only when every
-known node reports a `rev` at or above the deleting one, which for a
+`deleted: true` in the manifest, kept. Absence must mean "this copy is older
+than the one that created it". Otherwise a node rehomed after three weeks
+**resurrects every deleted playlist** — this is the single most likely defect in
+the whole design, it looks like a sync working correctly right up until it
+doesn't, and it deserves its own named test. Tombstones are collected only when
+every known node reports a `rev` at or above the deleting one, which for a
 single-node account is immediate and for a multi-node one is eventual; a
 tombstone is ~40 bytes, so there is no hurry.
 
-### 5.4 Rollback, and why local-first answers it
+A body arriving for a playlist the manifest tombstones is **dropped, not
+resurrected** — the manifest is the authority on existence. That ordering is
+the whole reason `count` lives in the manifest rather than being derived from
+the body.
+
+### 6.4 Rollback, and why local-first answers it
 
-AEAD authenticates a blob; it does not stop a node handing back an older one
-it still has (or a fresh one it never received). The defence is that **the
-client is the authority**: the merged state lives in the client's own
-IndexedDB, and merge takes the maximum `rev` across *local plus every node
-answering*. A stale or lying node can only lose the tie. It can never lower
-the merged state, because the local copy is one of the inputs.
+AEAD authenticates a blob; it does not stop a node handing back an older one it
+still has (or a fresh one it never received). The defence is that **the client
+is the authority**: the merged state lives in the client's own IndexedDB, and
+merge takes the maximum `rev` across *local plus every node answering*. A stale
+or lying node can only lose the tie. It can never lower the merged state,
+because the local copy is one of the inputs.
 
-This is what makes an offline node a non-event rather than a hazard. Nodes
-are backups and a transport. They are not the source of truth, and no node
-being reachable at all still leaves every playlist correct and, thanks to
-§4.2, fully legible.
+This is what makes an offline node a non-event rather than a hazard. Nodes are
+backups and a transport. They are not the source of truth, and no node being
+reachable at all still leaves every playlist correct and, thanks to §5.3, fully
+legible.
 
-### 5.5 What is genuinely lost, stated plainly
+### 6.5 What is genuinely lost, stated plainly
 
-Device 1 makes an edit, reaches no node, and is then lost or cleared: that
-edit is gone. This is the exposure of any offline-first application, it is
-not fixable without a durable always-reachable writer (which is §3.1, and
-refused), and it is still enormously better than today, where the same edit
-is lost on a cache clear regardless of what was online.
+Device 1 makes an edit, reaches no node, and is then lost or cleared: that edit
+is gone. This is the exposure of any offline-first application, it is not
+fixable without a durable always-reachable writer (which is §3.1, and refused),
+and it is still enormously better than today, where the same edit is lost on a
+cache clear regardless of what was online.
 
 ---
 
-## 6. Sync — and the point is that it adds no dialing
+## 7. Sync — and the point is that it adds no dialing
 
 A sweep of every group's node costs 10 s per unreachable one; the Search page
 does it deliberately, batched three at a time, because the user asked it to.
 Playlists must not do that at sign-in.
 
-**Sync rides on connections that were happening anyway.** Whenever a
-transport to any node is open for any other reason — opening a group, the
-Search page's sweep, the music pool dialing to play a track — the client
-piggybacks a `user_blob_fetch`, merges, and sends `user_blob_store` back if
-that node's copy is behind. `ConnectionPool` (`search-page.js:36`) already
-holds up to `MAX_POOL_SIZE` (12) live connections and hands them out by
-group, so this is a hook, not a new mechanism.
+**Sync rides on connections that were happening anyway.** Whenever a transport
+to any node is open for any other reason — opening a group, the Search page's
+sweep, the music pool dialing to play a track — the client piggybacks a
+`user_blob_fetch` for the **manifest**, merges, and sends `user_blob_store` back
+if that node's copy is behind. `ConnectionPool` (`search-page.js:82`) already
+holds up to `MAX_POOL_SIZE` (12) live connections and hands them out by group,
+so this is a hook, not a new mechanism.
+
+**Bodies are fetched lazily**, and this is what the split buys at sync time as
+well as at menu time: the manifest says which bodies are stale (`body_rev`), and
+a body is pulled when it is opened, loaded, or edited — not on every connection.
+A user with 40 playlists who only ever plays two never transfers the other 38.
 
 Two additions on top:
 
-- **An explicit "Sync now"** on the Playlists page, which does the Search-style
-  sweep and reports which nodes it could not reach — the same honest
-  reporting `fetchAllIndexes` already does.
-- **On sign-in, nothing.** The local copy is authoritative and complete
-  (§5.4); the first group opened will reconcile.
+- **An explicit "Sync now"** in the playlist menu, which does the Search-style
+  sweep and reports which nodes it could not reach — the same honest reporting
+  `fetchAllIndexes` already does.
+- **On sign-in, nothing.** The local copy is authoritative and complete (§6.4);
+  the first group opened will reconcile.
 
-A device that only ever opens one group therefore only ever converges with
-one node. That is correct and not a defect: convergence is eventual, and the
-copy the user is looking at is right the whole time.
+A device that only ever opens one group therefore only ever converges with one
+node. That is correct and not a defect: convergence is eventual, and the copy
+the user is looking at is right the whole time. It is also the honest answer to
+"I made this playlist inside group A" (§11): the write lands on whatever node
+was reachable, which is usually A's, and spreads from there.
 
 ---
 
-## 7. Protocol and node-side implementation
+## 8. Protocol and node-side implementation
 
-### 7.1 MNP — additive, MINOR bump (2.1)
+### 8.1 MNP — additive, MINOR bump (2.1)
 
 ```
-user_blob_store  { kind, rev, blob_enc }        client → node
-user_blob_fetch  { kind }                       client → node
-user_blob_resp   { kind, rev, blob_enc|null }   node   → client
+user_blob_store   { kind, rev, blob_enc }        client → node
+user_blob_fetch   { kind }                       client → node
+user_blob_list    { }                            client → node
+user_blob_delete  { kind }                       client → node
+user_blob_resp    { kind, rev, blob_enc|null }   node   → client
+user_blob_list_resp { blobs: [{kind, rev}] }     node   → client
 ```
 
-Modelled on `KEYPAIR_BUNDLE_*` in every respect, including that the node
-stores and returns an opaque string. `kind` is validated against a small
-allowlist (`{"playlists"}`) so the table does not become an arbitrary
+`user_blob_list` is new relative to the first draft and is what the split
+requires: a client that has lost its local state (a cache clear, a new device)
+must be able to discover which bodies exist without guessing UUIDs. It returns
+`kind` and `rev` only — never a payload — so it costs one small message and
+tells the node nothing it does not already know from its own table.
+
+Modelled on `KEYPAIR_BUNDLE_*` in every respect, including that the node stores
+and returns an opaque byte string. `kind` is validated against a **pattern** —
+`playlists` or `playlist:<uuid>` — so the table does not become an arbitrary
 key/value store for whatever a client feels like writing.
 
 Every reply carries `req_id` through the ordinary `_send` path. This is not
@@ -369,150 +545,480 @@ optional and does not need re-arguing: `CLAUDE.md` records at length what
 arrival-order matching costs, and the victim is never the request that was
 answered wrongly.
 
-### 7.2 Node side
+### 8.2 Node side
 
 | Piece | Where | What |
 |---|---|---|
-| Storage | `meshbay_node/bundle_store.py` | `user_blobs` table (§3.3), `store_user_blob` / `fetch_user_blob`, same shape as `store_keypair` / `fetch_keypair` |
-| Handlers | `transport/webrtc_server.py` | `_do_user_blob_store` / `_do_user_blob_fetch`, `self._user_id` from the authenticated session (NS6), never from the message |
-| Cap | same | Refuse over 256 KB with a stated reason; refuse an unknown `kind` |
-| Audit | same | `user_blob_store` / `user_blob_fetch` events, same as `keypair_bundle_store` already logs |
+| Storage | `meshbay_node/bundle_store.py` | `user_blobs` table (§3.3); `store_user_blob` / `fetch_user_blob` / `list_user_blobs` / `delete_user_blob`, same shape as `store_keypair` / `fetch_keypair` |
+| Handlers | `transport/webrtc_server.py` | `_do_user_blob_store` / `_fetch` / `_list` / `_delete`; `self._user_id` from the authenticated session (NS6), **never** from the message |
+| Caps | same | §4.3's four limits. Refuse with a stated reason; refuse a `kind` that does not match the pattern |
+| Audit | same | `user_blob_store` / `_fetch` / `_delete` events, as `keypair_bundle_store` already logs |
 
 `user_id` comes from the session, exactly as `_do_keypair_bundle_store` takes
-it — a `user_id` in the message body would let any member read or overwrite
-any other member's blob, which is the C5 shape one size down.
+it — a `user_id` in the message body would let any member read or overwrite any
+other member's blob, which is the C5 shape one size down.
 
 **No hub change. No change to indexing, streaming, transcoding, or the GEK.**
 
-### 7.3 What the node can and cannot do with it
+### 8.3 What the node can and cannot do with it
 
-It can delete it, lose it with its disk, or serve a stale copy (§5.4 covers
-the last). Durability is "the local copy, plus N node copies", with no
-guarantee from any single one — which for an account on one node means the
-local copy matters. Worth one line in the UI, not a warning dialog.
+It can delete it, lose it with its disk, or serve a stale copy (§6.4 covers the
+last). Durability is "the local copy, plus N node copies", with no guarantee
+from any single one — which for an account on one node means the local copy
+matters. Worth one line in the UI, not a warning dialog.
 
 ---
 
-## 8. Client side
-
-### 8.1 A pure module, deliberately separate from the UI
-
-`static/playlists.js` holds the data layer and **no UI**: load/merge/save,
-the tombstone rules, the id/path repair, seal and open. This is not tidiness.
-Source-reading tests are weak evidence and are most of what this repo can do
-for the SPA — but a pure function over two objects can be *executed*, the way
-`tests/harness/mse_harness.mjs` lifts the real player functions and runs
-them. The merge is the one part of this feature that can be properly tested,
-so it must not be entangled with a component.
-
-`tests/harness/playlist_merge.mjs` runs the real `merge()` over scripted
-divergences: two devices, one node offline for each in turn, a delete on one
-side and an edit on the other, a resurrect attempt, a `rev` tie. Model the
-environment, never the code under test.
-
-### 8.2 Where it appears
-
-Playlists cross groups, so they do not belong to a group's Music tab:
-
-- **New route `/playlists`** and `static/playlists-page.js`, a sibling of
-  `/search`, plus a sidebar entry. It renders from the **cached** indexes
-  (`getAllCachedIndexes`), so it opens instantly and works with everything
-  offline; it dials only to play, or on "Sync now".
-- **"Add to playlist"** in `music-app.js` (album and track level) and in
-  `search-page.js`'s music results — both already have the entry in hand,
-  with `groupId` attached.
-- **The player bar needs nothing.** It is already at shell level in `app.js`,
-  already resolves a connection per track from `entry.groupId`, and already
-  crosses groups within one queue. This is worth stating loudly, because the
-  cross-group requirement reads like the hard part and is in fact already
-  built (the cross-group merge already covers it — `MESHBAY_DESIGN.md` §9.11).
-
-### 8.3 The IndexedDB detail that will otherwise be missed
-
-`hub-client.js` opens `meshbay` at `IDB_VERSION = 1` with a single store,
-`group_indexes`. Adding a `playlists` store means **bumping to 2** and
-handling it in the existing `onupgradeneeded`, which currently creates one
-store and would otherwise never run again. A store that is never created
-throws on first access, at a point far from the version constant.
-
-### 8.4 Checklist, per `MESHBAY_DESIGN.md` §9.4
-
-1. `playlists.js` (data) and `playlists-page.js` (UI).
-2. Route + sidebar entry in `app.js`.
-3. Nothing for caching: every file under `static/` feeds the `/a/<hash>/`
-   fingerprint.
-4. `test_hook_ordering.py` (`STATIC_FILES`) and
-   `test_transport_contracts.py` (`SPLIT_FILES`) — both new files.
-5. i18n keys in all ten `static/locales/*.js`; `test_locales.py` holds them
-   to `en.js`'s key set.
-6. `npm run sync-ui` in `meshbay-client`, confirmed reported.
+## 9. The queue — the change the UI actually needs
+
+This section answers the question asked directly, because the answer is yes and
+the reason is worth stating precisely.
+
+### 9.1 Yes: "load a playlist" replaces the current queue
+
+There is already a current list, it is what shuffle operates over, and loading a
+playlist into it is the right shape. Concretely, in `music-player.js`:
+
+```js
+const [tracks, setTracks] = useState([]);   // the queue, in insertion order
+const [order,  setOrder]  = useState([]);   // indices into tracks — the play order
+const [pos,    setPos]    = useState(0);    // index into order
+```
+
+`order` is the indirection that makes shuffle work without disturbing `tracks`
+(`shuffledOrder`, `toggleShuffle` at `music-player.js:444`), `pos` walks it, and
+`prefetchNext(fromPos)` reads `tracks[order[fromPos + i]]`. An album handed over
+by `onPlayQueue(album.tracks, i)` and a playlist handed over the same way are
+**indistinguishable** below that call. So:
+
+> **Load = `onPlayQueue(playlistTracks, 0, null, 'replace')`.** Confirmed. The
+> existing queue is discarded, shuffle applies to the new one on the next
+> render, prefetch warms from the new index 0, and auto-advance runs exactly as
+> it does for an album — because it *is* the same code path, untouched.
+
+### 9.2 The real work: the queue can only be replaced today
+
+`onPlayQueue` flows to `app.js:738`:
 
-No `apps.js` registry entry and no `ALLOWED_APPS` change: this is not a group
-application. It is a page, like Search.
+```js
+setMusicQueue({ tracks, startIndex, nonce: Date.now() });
+```
+
+and the player's effect keyed on `[queue]` (`music-player.js:344`) resets
+`tracks`, `order`, `pos`, the error and the failure counter — wholesale, every
+time. **There is no way to add to the queue without restarting it**, and "play
+next" and "enqueue" are exactly that. This is problem D, and it is the only part
+of the UI request that is not a new component over existing plumbing.
+
+**The shape:** one more field, defaulted, so no existing call site changes.
+
+```js
+onPlayQueue(tracks, startIndex, source, op)   // op: 'replace' | 'next' | 'append'
+```
+
+- `'replace'` (the default, and what every call site today means) — today's path,
+  behaviour for behaviour.
+- `'next'` — splice the new indices into `order` at `pos + 1`. `pos` does not
+  move, the `<audio>` element is not touched, nothing reloads.
+- `'append'` — push them at the end of `order`.
+
+### 9.3 Collapse `tracks` / `order` / `pos` into one reducer
+
+Three `useState`s updated from one event is where this ships a defect. `setOrder`
+needs the length `setTracks` is about to produce, and cannot see it; read from
+the stale closure instead and two enqueue clicks in the same tick produce indices
+that both point past the end — a queue with holes, from a double click.
+
+So `queue-ops.js`: a pure reducer over `{ tracks, order, pos }` with actions
+`replace / insertNext / append / removeAt / skipTo / reshuffle`. Two reasons,
+and the second is the one that counts:
+
+1. It is the only way the append is correct under batching.
+2. **It can be executed by a test.** Source-reading tests are weak evidence and
+   are most of what this repo can do for the SPA — but a pure function over a
+   state object runs, the way `tests/harness/mse_harness.mjs` lifts the real
+   player functions and runs them. `tests/harness/queue_ops.mjs` drives: append
+   to an empty queue, insert-next at the last position, insert-next while
+   shuffled, two appends in one tick, remove the currently playing track,
+   toggle shuffle after an append. Model the environment, never the code under
+   test.
+
+The regression guard is that `replace` must produce exactly today's
+`{ tracks, order, pos }` for the same inputs — it is a mechanical lift of the
+existing effect body, and the harness pins it.
+
+### 9.4 Three details that are cheap now and expensive later
+
+- **Shuffle and append.** Appended tracks go at the end of `order`, in the order
+  given, *not* reshuffled into the middle. That is what every player does and
+  what "add to queue" means. `toggleShuffle` rebuilds `order` from
+  `tracks.length` and so stays correct after any number of appends, for free.
+- **`prefetchNext(pos)` must be called after an `insertNext`**, or the track the
+  user just asked to play next is the one track in the queue that is cold. One
+  line, and the only visible regression an enqueue can introduce. Nothing needs
+  evicting: `blobCacheRef` is keyed by `entry.id`, so a blob already fetched for
+  a track that has moved index is still keyed correctly.
+- **`groupTransportRef` must only be set on `'replace'`** (`app.js:728`). It is
+  a single-slot fast path for the group currently open; repointing it because
+  the user enqueued one track from another group silently drops the playing
+  group back to the pool. Not a bug — the pool works — but a pointless one.
+
+### 9.5 Prefetch across groups — the one new consideration
+
+`prefetchDepth()` returns 5 on Wi-Fi, and `MAX_CACHED_BLOBS` is 6 to match.
+Unchanged, and **must** stay unchanged: raising either is the obvious thing to
+do for a long playlist and is wrong, because for an album those 5 tracks share
+one connection, and for a cross-group playlist they may need **five different
+node dials**, each up to 10 s, against a pool of 12.
+
+Rule: **prefetch only entries whose group already has a live connection in the
+pool**; let the rest warm when the queue reaches them and the dial happens
+anyway. An album is unaffected (one group, always live). A shuffled cross-group
+playlist stops trying to open half the pool to warm tracks it may never reach.
+
+---
+
+## 10. The user interface
+
+Nothing here is a new page. Requirement 6 — that all of this work inside a group
+*and* on Search → Music — is satisfied by putting it in `music-app.js`, which
+`group-page.js` and `search-page.js` (with `groupId="search"`,
+`search-page.js:784`) already both mount. Written once, appears in both.
+
+### 10.1 A shared menu component, because there is none
+
+The codebase has no context menu and no dropdown outside the account menu in
+`app.js:99`. `menu.js` provides `<Menu>` and `useMenu()`:
+
+- opens on **right-click** (`onContextMenu`, `preventDefault()`) and on a **dots
+  button** — `icon.js` already has `dots` (`icon.js:54`). Both affordances, both
+  platforms: the button is visible on hover on a fine pointer and always visible
+  under `@media (pointer: coarse)`.
+- closes on Escape, on an outside click, and **on scroll**. The last one is not
+  optional here: Music's toolbar is a sticky band and the grid scrolls beneath
+  it, so a menu that survives a scroll is a menu now anchored to a different
+  album than the one it was opened on.
+- flips its anchor when it would open past the viewport edge, which on a phone
+  is most of the time.
+- submenus: a flyout on a fine pointer; **on a coarse pointer, a sheet**. A
+  two-level flyout (§10.3's "remove a track") has nowhere to go at 400 px, and
+  building it as a nested flyout and then discovering that on a phone is the
+  predictable version of this.
+
+Videos, Photos and Files all want this component eventually. It is deliberately
+generic and lives outside `music-*.js`.
+
+### 10.2 The per-item menu — cover art and track rows
+
+On an album card (`AlbumCard`, `music-app.js:253`), on a detail-modal track row,
+and on a flat-list row (`FlatTrackRow`, `music-app.js:370`):
+
+```
+Play                     → onPlayQueue(items, 0, source, 'replace')
+Play next                → 'next'
+Add to queue             → 'append'
+────────────────────────
+Add to playlist        ▸   Favourites
+                           <other playlists, by name>
+                           ────────────
+                           New playlist…
+```
+
+`items` is the album's tracks in track order, or the single track. The submenu
+is drawn from the **manifest** (§4.3): instant, offline, no body fetched.
+Favourites is always first, as asked, and is materialised on first use so it is
+there on a fresh account with nothing created. "New playlist…" at the bottom
+costs one item and covers the commonest way a playlist comes to exist — wanting
+to put something in one.
+
+**One structural blocker, found in the existing markup.** `music-track-row` is a
+`<button>` (`music-app.js:312`, `:373`, `music-player.js:167`) and `music-card`
+is a `<div onClick>`. A dots `<button>` cannot nest inside a `<button>` — it is
+invalid HTML and browsers reparent it, which breaks the row. The row must become
+a `<div class="music-track-row">` holding a title `<button>` (the play action,
+keeping today's keyboard behaviour) and a trailing dots `<button>`. Mechanical,
+touches three call sites, and is the kind of thing that turns into "why does the
+menu open behind the row" if it is discovered during implementation instead of
+here.
+
+### 10.3 The single toolbar button
+
+One `tb-btn` in `.video-toolbar` in `music-app.js` — the sticky band
+(`style.css` "Sticky chrome": `.sticky-chrome > .video-toolbar` pins under
+`--nav-h + --chrome-h`), so it is reachable at any scroll position, as asked.
+A new `playlist` glyph in `icon.js` next to `music`. One button, one icon, no
+label — the toolbar already wraps to three rows on a phone
+(`style.css:2557`) and has no room for a word.
+
+The menu, in the requested order:
+
+```
+Load a playlist                    ▸  <list>          → replace the queue, play
+Save the current queue as…            <name prompt>   ← §10.4
+New playlist…                         <name prompt>
+Delete a playlist                  ▸  <list>          → inline confirm
+Remove a track from a playlist     ▸  <list> ▸ <tracks>
+────────────────────────────────
+Sync now                                              ← §7
+```
+
+Two additions to what was asked, both stated so they can be refused: **"Save the
+current queue as…"** is placed at 2 because it is a creation verb and belongs
+next to the other one; **"Sync now"** is §7's explicit sweep, which has to live
+somewhere and this is the only playlist surface there is.
+
+Rules the list items carry:
+
+- **Load** replaces (§9.1) and starts playing. It fetches the body first if
+  `body_rev` says the local copy is stale, which is the one place a playlist
+  action can block — show the spinner the page already has.
+- **New** takes a name only, as asked; tracks are attached afterwards. The name
+  must be unique *for this user*, checked against the manifest, case-folded with
+  the same `foldKey` the Music grouping already uses (`music-app.js`, exported)
+  rather than a second normaliser — a copy keeps agreeing until one of them
+  changes.
+- **Delete** never lists Favourites (§5.1). It confirms inline; not
+  `window.confirm()`, which blocks the SPA's event loop and looks like a browser
+  alert in an Electron shell.
+- **Remove a track** is the two-level one, and is a **sheet on mobile**
+  (§10.1): pick the playlist, then its tracklist with a trash button per row.
+  That sheet is also where reordering lands if O4 is ever taken up, which is
+  another reason not to build it as a flyout.
+
+### 10.4 Saving the current queue
+
+Reachable from two places, deliberately: the **queue panel** (`QueuePanel`,
+`music-player.js:136`) gets a button in its top bar, because that panel is where
+"the current queue" is a thing the user can see; and the toolbar menu mirrors it
+for discoverability.
+
+It saves `order.map(i => tracks[i])` — **play order, not insertion order**. If
+shuffle is on, that freezes the shuffle, which is what "save what I am listening
+to" means. Entries pass through §5.3's whitelist on the way out.
+
+### 10.5 i18n
+
+Every string through `t()` and into all ten `static/locales/*.js`;
+`test_locales.py` holds them to `en.js`'s key set. Favourites' display name is
+`t('playlists.favorites')` — the reserved id `"favorites"` is what is stored,
+never the localised name, or an account that switches language grows a second
+favourites list.
+
+---
+
+## 11. Unavailability — three different things, and the request conflates two
+
+| state | how it is known | already handled? |
+|---|---|---|
+| **Root unavailable** — a disk not mounted, group up and saying so | `nodeRoots[].available`, filtered into `availableEntries` (`group-page.js:716`) | yes — those entries never reach the UI |
+| **Group unreachable** — no node answers | only by dialing | partly — see below |
+| **File gone** — indexed, then deleted or moved | only at fetch | yes — as a fetch failure |
+
+### 11.1 Adding is never blocked on reachability
+
+The request asks that a track from an unreachable group not be added. Applied to
+**playlists** that is the wrong rule and would make them lossy in exactly the
+case they exist for: a playlist is durable, and a group that is off tonight is
+back tomorrow. Refusing the add loses the user's intent permanently to recover
+from a condition that lasts an evening. Worse, "is this group reachable" is only
+answerable by dialing, and dialing to add is precisely the cost §7 refuses.
+
+So: **adding to a playlist never checks reachability, and never dials.** The
+entry came from a rendered list, which came from an index this client holds.
+
+### 11.2 Adding to the queue does not dial either — playback skips
+
+Same reasoning, shorter: `play` / `play next` / `append` add what was on screen.
+Loading a playlist loads all of it, greying entries whose group is in the known-
+down set (the same set `search-page.js:535`'s `isDown` already keeps) without
+removing them — a queue whose contents depend on network weather is worse than
+one with a few dimmed rows.
+
+The skipping then happens where it can actually be known, at play time, and
+**most of it is already built**: `advancePastFailure` (`music-player.js:215`)
+was written for exactly this and is why a corrupt file between two good ones
+does not stall an album.
+
+### 11.3 The one change: separate a bad file from a down group
+
+`MAX_CONSECUTIVE_FAILURES = 5` is sized for a corrupt file among good ones. A
+playlist whose next six tracks all come from one offline group hits the bound
+and stops, with an error, and the user reads that as "the playlist is broken".
+That is a regression created by playlists, in code that is correct today.
+
+Split the two failures, because they are different properties of different
+things:
+
+- **a decode / playback failure** is a property of *that file* — keep today's
+  bounded counter exactly as it is;
+- **a connect / transport failure** is a property of *that group* — mark the
+  `groupId` down for the session, advance past **every** queued track from that
+  group in one step, and reset the counter.
+
+If that empties the queue, stop **once**, with a stated count — "3 groups
+unreachable, 42 tracks skipped" — which is the same honest reporting
+`fetchAllIndexes` does, and is what the 5-bound was protecting in the first
+place. A group marked down is retried only on an explicit user action (pressing
+play or next), never automatically, so a 300-track playlist does not re-dial a
+dead node 300 times. `transport.waitForReconnect()` already covers the transient
+within-group case and is untouched.
 
 ---
 
-## 9. Security — per adversary
+## 12. Security — per adversary
 
 | Claim | Passive hub | Active hub | Malicious node operator | Another member |
 |---|---|---|---|---|
 | Playlist contents (which tracks, which groups) | ✅ never transmitted to the hub | ✅ never transmitted to the hub | sealed under a key derived from the passphrase; the node holds ciphertext only | ✅ never served to anyone but the authenticated owner (`user_id` from the session) |
-| Existence of playlists / how many | ✅ | ✅ | visible — one row, `stored_at`, and a padded length (§4.3) | ✅ |
-| Editing timing | ✅ | ✅ | visible for writes reaching *that* node | ✅ |
-| Integrity of the merged state | — | — | can serve stale or nothing; cannot lower the merged `rev` (§5.4) | — |
+| How many playlists, and their relative sizes | ✅ | ✅ | **visible, and more so than in the first draft** — one row per playlist, each with its own `stored_at` and padded length | ✅ |
+| Editing timing, per playlist | ✅ | ✅ | visible for writes reaching *that* node | ✅ |
+| Integrity of the merged state | — | — | can serve stale or nothing; cannot lower the merged `rev` (§6.4) | — |
 | Deleting a playlist | — | — | can delete its own copy; other nodes and the local copy survive it | — |
 | Which tracks are actually played | — | — | already visible — the node serves the bytes | — |
 
+**What the split costs, stated rather than buried.** One blob leaked one length
+and one timestamp. N+1 blobs leak N+1 of each: an operator can see that this
+account has nine playlists, that one of them is much larger than the rest, and
+which single one was edited at 23:40. That is more than before. It is accepted
+because the alternative is rewriting and re-uploading the entire collection on
+every star (§4.3), which leaks the same timing anyway while costing an order of
+magnitude more bandwidth — and because playlist *names* and *contents* remain
+sealed throughout.
+
+**Compression before encryption, named and dismissed.** Compressing then sealing
+makes the ciphertext length a function of the plaintext's redundancy, which is
+the CRIME/BREACH shape. It does not apply here in the form that matters: there
+is no adversary-chosen input mixed with a secret in one compression context per
+request. The residual is a one-bit-per-user-action oracle — an operator who gets
+the user to add a file *they named* to a playlist, and watches the length delta,
+learns whether a string they chose already appeared. The 4 KB padding (§4.3)
+means that oracle needs thousands of coordinated user actions to yield one
+string. Written down, not defended further.
+
 **The claim this design supports:** playlists add **no new authorization
 boundary and no new key hierarchy**. The node already stores an opaque
-per-account object for this same account under this same key material; this
-is a second payload of an existing kind, and the hub is not involved at all.
+per-account object for this same account under this same key material; this is a
+second payload of an existing kind, and the hub is not involved at all.
 
-**The claim it must not make:** that a node cannot lose or withhold a
-playlist. It can. The property is convergence with a local authority
-(§5.4/§5.5), not durability guaranteed by any node.
+**The claim it must not make:** that a node cannot lose or withhold a playlist.
+It can. The property is convergence with a local authority (§6.4/§6.5), not
+durability guaranteed by any node.
 
-**One thing §4.2's fallback changes.** Playing a track from group B because
-group A's node is offline means operator B, not operator A, sees that play.
-Both already host that file for this account and already see its other plays,
-so nothing new is learned by anyone — but it is a substitution of *observer*,
-it is not obvious from the UI, and so it is written down here rather than
-discovered later.
+**One thing §5.3's fallback changes.** Playing a track from group B because
+group A's node is offline means operator B, not operator A, sees that play. Both
+already host that file for this account and already see its other plays, so
+nothing new is learned by anyone — but it is a substitution of *observer*, it is
+not obvious from the UI, and so it is written down here rather than discovered
+later.
 
 ---
 
-## 10. Open items — deliberately deferred
+## 13. Open items — deliberately deferred
 
 | # | Item | Why not now |
 |---|---|---|
-| O1 | Sharing a playlist with other group members | **Explicitly out of scope** (settled before this document). It is not an extension: a shared playlist is group state, sealed under the GEK, with concurrent writers — which makes §5's per-playlist LWW insufficient and an OR-Set over tracks mandatory. If it is ever wanted, reopen §5, not §3 |
+| O1 | Sharing a playlist with other group members | **Explicitly out of scope.** Not an extension: a shared playlist is group state, sealed under the GEK, with concurrent writers — which makes §6's per-playlist LWW insufficient and an OR-Set over tracks mandatory. If it is ever wanted, reopen §6, not §3 |
 | O2 | A second copy wrapped under the account recovery key | `bundle_enc_recovery` is the exact precedent and the column is reserved in §3.3, so this is a client-side change alone when wanted. Not built now because a forgotten passphrase already strands more than playlists |
-| O3 | Smart/auto playlists (by artist, by year, recently added) | These are queries over the cached index and need no storage at all. Genuinely a separate feature, and cheaper than this one |
-| O4 | Ordering conflicts resolved better than LWW | Reordering is rare and losing a reorder is survivable; losing an added track is not, and per-playlist `rev` already prevents that for one user. Revisit only with O1 |
-| O5 | Export / import a playlist as a file | Trivial once §8.1 exists (it is `JSON.stringify` of a merge unit) and worth doing, but it is not what makes playlists work across devices |
-| O6 | Tombstone collection driven by an explicit per-node acknowledged `rev` | §5.3's rule is adequate at this scale; a real garbage collector matters at thousands of deletions, which is not a real state |
+| O3 | Smart / auto playlists (by artist, by year, recently added) | Queries over the cached index; they need no storage at all. Genuinely a separate feature, and cheaper than this one |
+| O4 | Reordering a playlist, and conflicts better than LWW | Losing a reorder is survivable; losing an added track is not, and per-playlist `rev` already prevents that. The drag surface is §10.3's sheet when it comes |
+| O5 | Export / import a playlist as a file | Trivial once §14.1 exists (it is `JSON.stringify` of one body) and worth doing, but it is not what makes playlists work across devices |
+| O6 | Tombstone collection driven by an explicit per-node acknowledged `rev` | §6.3's rule is adequate at this scale; a real collector matters at thousands of deletions, which is not a real state |
+| O7 | A `/playlists` page and sidebar entry | **Dropped from this design, not deferred lightly.** The first draft proposed it; the requirement is a menu in Music's toolbar, and Music is already mounted in both places that matter (§10). A separate page would be a third surface showing the same list, and the first one to go stale |
+| O8 | Per-queue persistence — restoring the current queue after a reload | Different object with a different lifetime: the queue is ephemeral and per-device, and `localStorage` is its right home, not §3's blob. Worth doing; not this |
 
 ---
 
-## 11. Acceptance before shipping
+## 14. Client side
+
+### 14.1 Modules
+
+| file | contents | why separate |
+|---|---|---|
+| `playlists.js` | manifest + body load / merge / save, tombstones, id-path repair, compress, seal, open, the §5.3 whitelist | pure data layer, **no UI** — the merge is the one part that can be properly tested and must not be entangled with a component |
+| `queue-ops.js` | the `{tracks, order, pos}` reducer (§9.3) | same reason, and it is the part that can regress the player |
+| `menu.js` | `<Menu>`, `useMenu()` — anchored menu, submenus, coarse-pointer sheets | generic; Videos, Photos and Files want it too |
+| `playlist-menu.js` | the toolbar button, its menu, and the create / delete / remove-track / save-queue modals | ~300 lines of modal that do not belong in `music-app.js` |
+
+Edited: `music-app.js` (toolbar button, per-item menus, the `<button>` → `<div>`
+row fix), `music-player.js` (the reducer, the `op` branch, the split failure
+counters, the queue panel's save button), `app.js` (`op` through
+`handlePlayQueue`, the `groupTransportRef` guard), `hub-client.js` (IDB v2),
+`keyderive.js` (the HKDF handle), `icon.js` (a `playlist` glyph), `style.css`.
+`search-page.js` needs **nothing** — it already mounts `MusicApp`.
+
+### 14.2 The IndexedDB detail that will otherwise be missed
+
+`hub-client.js` opens `meshbay` at `IDB_VERSION = 1` (`hub-client.js:15`) with a
+single store, `group_indexes`. Adding `playlists` means **bumping to 2** and
+handling it in the existing `onupgradeneeded`, which currently creates one store
+and would otherwise never run again. A store that is never created throws on
+first access, at a point far from the version constant.
+
+One store holding the manifest and the bodies, keyed by `kind`, so §8.1's
+namespace is the IndexedDB key as well and nothing has to translate between two
+schemes.
+
+### 14.3 Checklist, per `MESHBAY_DESIGN.md` §9.4
+
+1. The four new files above, plus the edits.
+2. Nothing for caching: every file under `static/` feeds the `/a/<hash>/`
+   fingerprint.
+3. `test_hook_ordering.py` (`STATIC_FILES`) and `test_transport_contracts.py`
+   (`SPLIT_FILES`) — all four new files.
+4. i18n keys in all ten `static/locales/*.js`; `test_locales.py` holds them to
+   `en.js`'s key set.
+5. `npm run sync-ui` in `meshbay-client`, confirmed reported — CI fails if the
+   copy drifts.
+6. No `apps.js` registry entry and no `ALLOWED_APPS` change: this is not a group
+   application, it is a menu inside one that already exists.
+
+---
+
+## 15. Acceptance before shipping
+
+**No-regression first**, because §9.2 changes the player's queue state and
+nothing else in this document can be judged until that is known to be clean:
+
+1. Baseline counts **before any edit**, per `CLAUDE.md`: the hub suite has
+   pre-existing browser failures, and a count taken afterwards proves nothing.
+2. Play an album, let it auto-advance across at least three tracks, with
+   prefetch observed warming ahead. Then the same with shuffle on, toggled
+   mid-album, and confirm the playing track does not restart.
+3. `tests/harness/queue_ops.mjs` runs the real reducer through §9.3's six
+   scenarios, including **two appends in one tick**, and fails if the reducer is
+   replaced by the three-`useState` version.
+
+**Then the feature:**
 
-1. `tests/harness/playlist_merge.mjs` runs the real `merge()` through the
-   five divergences in §8.1, including the resurrect attempt, and **fails
+4. `tests/harness/playlist_merge.mjs` runs the real `merge()` through five
+   divergences — two devices, one node offline for each in turn, a delete on one
+   side and an edit on the other, a resurrect attempt, a `rev` tie — and **fails
    with the tombstone rule removed**. Check that, or the test is decoration.
-2. A round trip through a real node: seal, `user_blob_store`, restart the
-   daemon, `user_blob_fetch`, open. Confirms the blob survives the process,
-   not just the test.
-3. Read `bundles.db` back and confirm the playlist plaintext is not in it —
-   the same check `test_chat_key_storage.py` already makes for epoch keys,
-   for the same reason. A plaintext table beside it is the obvious thing to
-   write and would collapse the whole claim silently.
-4. Two browsers, one account, one node: edit in each, converge, and confirm
-   both agree. Then repeat with the node stopped between the two edits, and
-   confirm neither edit is lost when it comes back.
-5. Open `/playlists` with **every** node offline and confirm the page renders
-   in full — names, artists, durations, entries greyed — because that is the
-   requirement §4.2 exists for and it cannot be unit-tested meaningfully.
-6. Confirm the size cap refuses rather than truncates, and that the refusal
-   reaches the client as a stated reason rather than a bare `error`.
-7. Confirm sign-in still runs Argon2id exactly **once** after §3.4's change
-   (measure it; the budget is the 650 ms already recorded in draft-v5 §7.1).
+5. A round trip through a real node: seal, `user_blob_store`, restart the daemon,
+   `user_blob_fetch`, open. Confirms the blob survives the process, not just the
+   test. Repeat for a body and for the manifest.
+6. Read `bundles.db` back and confirm no playlist plaintext is in it — the same
+   check `test_chat_key_storage.py` already makes for epoch keys, for the same
+   reason. A plaintext table beside it is the obvious thing to write and would
+   collapse the whole claim silently.
+7. Two browsers, one account, one node: edit in each, converge, confirm both
+   agree. Repeat with the node stopped between the two edits, and confirm
+   neither edit is lost when it comes back.
+8. Open Music with **every** node offline and confirm every menu in §10 draws in
+   full — playlist names, track titles, artists, durations, entries greyed —
+   because that is the requirement §5.3 exists for and it cannot be unit-tested
+   meaningfully.
+9. Build a playlist of ~2 000 tracks, confirm the sealed body is under the 1 MB
+   cap, and **measure the bytes written when one track is starred** — it must be
+   the Favourites body plus the manifest, not the collection. That number is
+   what §4.3 is for.
+10. Confirm each cap refuses rather than truncates, and that the refusal reaches
+    the client as a stated reason rather than a bare `error`.
+11. Confirm sign-in still runs Argon2id exactly **once** after §3.4's change
+    (measure it; the budget is the 650 ms already recorded in draft-v5 §7.1).
+12. A playlist spanning three groups, one of them stopped: confirm it loads
+    whole, plays, skips the dead group's tracks **in one step** rather than
+    erroring on the sixth, and reports the count.
+13. Create a playlist from inside a group, then open Search → Music and confirm
+    the same playlist is in the menu there (requirement 6) — on the same device
+    immediately, on a second device after it has opened any group.
-- 
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