eae9057baf
New editor-beta.html: a bidirectional live mirror over the existing USB-MIDI SysEx channel (0x7D). Either the website or the device can edit grooves, change tempo/volume, start/stop, or select set-list items, and the other reflects it. - src/livesync.js: LiveSync layer (opcodes 0x40 HELLO / 0x41 FULL / 0x42 DELTA / 0x43 BYE) riding the existing _ensureMidi/_send/onDeviceMidi plumbing. Fine deltas for transport/bpm/vol/sel/beat, coalesced full-state for structural edits; echo suppression via origin + _applyingRemote guard; device-authoritative heartbeat reconciles drift. ?loopback=1 self-test mode (no hardware needed). - editor-beta.html: copy of editor.html + "Live sync" toggle, SysEx routing, and broadcast hooks at each mutation choke point (guarded by _applyingRemote). - docs/livesync-protocol.md: wire spec + firmware checklist for pico-cp/app.py (firmware half owned by the other instance — editor side + spec only here). - build.sh / deploy.sh: add editor-beta.html to the build + version-stamp loops. Editor side only; pico-cp/app.py untouched. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
195 lines
9.7 KiB
Markdown
195 lines
9.7 KiB
Markdown
# PM Live-Sync protocol (beta)
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Bidirectional live mirror between the **PM_E‑1 editor** (web) and a **PM_K‑1 device**
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(firmware). When armed, either side can edit a groove, change tempo/volume,
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start/stop, or select a set‑list item, and the other side reflects it in real
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time.
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It rides the **existing USB‑MIDI SysEx channel** (manufacturer `0x7D`) that the
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device link already uses for RTC / version / programs / firmware — no new
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transport, no new browser permission.
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- **Editor side:** implemented in `src/livesync.js` + hooks in `editor-beta.html`.
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- **Device side:** to be implemented in `pico-cp/app.py` (this document is the contract).
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- **Browser support:** Web MIDI = Chrome / Edge / Firefox (no Safari), same as the existing "Device audio" feature.
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---
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## 1. Frames
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Every message is one SysEx frame:
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```
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F0 7D <op> <payload ASCII bytes, each 0x00–0x7F> F7
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```
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`<op>` lives in the free `0x40` block (existing ops: `0x01` RTC, `0x02/0x03`
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version, `0x10` programs, `0x21/22/23` firmware, `0x7E/0x7F` NAK/ACK):
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| op | name | direction | payload |
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|------|-------|------------------|-------------------------------------------|
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| 0x40 | HELLO | either → either | `<origin>` |
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| 0x41 | FULL | either → either | `<origin>;<seq>;<running>;<sl>;<item>;<patch>` |
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| 0x42 | DELTA | either → either | `<origin>;<seq>;<evt>` |
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| 0x43 | BYE | either → either | `<origin>` |
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- **Payload is 7‑bit ASCII** — never emit a byte > `0x7F` (it corrupts the SysEx
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stream and, per `build.sh`, would also break the firmware‑update path). All
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share‑language patch strings are already ASCII.
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- `<origin>` — a short per‑session id (the editor uses e.g. `e1a2b3c`). Used to
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drop your own echoes (see §4).
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- `<seq>` — a monotonically increasing integer per sender. Informational /
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duplicate‑drop; ordering is guaranteed by USB‑MIDI so no reordering logic is
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required.
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- `<running>` — `0` or `1`.
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- `<sl>` / `<item>` — set‑list and item index of the loaded program, or `-1`.
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- `<patch>` — a share‑language patch string (see §3). It contains `;` and `/`,
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so it is **always the tail**: parse the first 5 `;`‑fields, then rejoin the
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rest as the patch.
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---
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## 2. DELTA event grammar (`<evt>`)
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One mutation, no `;` inside. Reuses the share‑language tokens (see
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`src/engine.js` / README "Share language").
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| evt | meaning |
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|------------------------------|----------------------------------------------------|
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| `play` | start transport |
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| `stop` | stop transport |
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| `bpm=<n>` | set tempo (clamped to the firmware's BPM range) |
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| `vol=<pct>` | master volume, 0–100 |
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| `sel=<sl>/<item>` | cue/load a set‑list item |
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| `beat=<lane>/<step>/<level>` | per‑step dynamics; level `0/1/2/3` = mute/normal/accent/ghost |
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| `lane=<lane>/<field>/<value>`| lane field edit (see below) |
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`<lane>` and `<step>` are **0‑based** indices into the current program's lane
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list / that lane's step list (same order both sides).
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`lane=` fields and values:
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| field | value |
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|-----------|------------------------------------------------|
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| `sound` | voice name (`kick`, `snare`, `hatClosed`, …) |
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| `groups` | grouping string, e.g. `2+2+3` |
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| `sub` | subdivision int: 1 / 2 / 3 / 4 / 6 |
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| `swing` | `0` or `1` |
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| `gain` | dB int, e.g. `-3` |
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| `poly` | `0` or `1` |
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| `enabled` | `0` or `1` (0 = silenced lane) |
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> Structural changes that re‑shape the lane list (add lane, remove lane,
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> reorder) are **not** sent as deltas. Send a fresh **`0x41` FULL** instead — it
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> is simpler and self‑healing. The editor does exactly this (a coalesced
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> full‑state push ~150 ms after the last structural/practice edit).
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---
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## 3. What each side emits vs. applies
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The two halves are **asymmetric in what they emit but symmetric in what they
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apply** — each must apply *every* op/evt listed above.
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**Editor emits:**
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- fine `0x42` deltas for `play`/`stop`, `bpm`, `vol`, `sel`, `beat`
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- a coalesced `0x41` FULL for any lane‑field / add / remove / practice (trainer,
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ramp, segment bars, countdown) edit
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- `0x41` FULL on connect and in reply to a received `0x40`
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**Device should emit** (from its on‑device input handlers):
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- `play`/`stop` when button A toggles transport
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- `bpm=<n>` when the joystick / tap changes tempo (throttle to ≤ ~10/s)
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- `sel=<sl>/<item>` on set‑list navigation
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- `beat=<lane>/<step>/<level>` on a touch beat edit (`app.py` ~573–625)
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- a `0x41` FULL after any lane add/remove/reorder or multi‑field lane edit
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- a periodic `0x41` FULL **heartbeat** (~every 3–5 s) — the device is the
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convergence authority (see §4)
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- `0x41` FULL in reply to a received `0x40`
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The `patch` in a `0x41` is produced by the device's existing program serializer
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(the inverse of `parse_program()` in `app.py`). It must round‑trip through the
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editor's `patchToSetup()` — i.e. the same grammar already used for
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`programs.json` `prog` strings, plus a leading `t<bpm>` and optional `vol<pct>`.
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---
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## 4. Echo / loop suppression and conflict policy
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Two rules keep the mirror from oscillating:
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1. **Applying a remote change never re‑broadcasts.** Wrap every apply in an
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"applying remote" flag (the editor uses `_applyingRemote`) and have all of
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your broadcast hooks early‑out while it is set. This is the primary guard.
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2. **Drop your own origin.** On receive, if `origin == myOrigin`, ignore the
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frame. (Belt‑and‑suspenders; also lets the editor's `?loopback=1` self‑test
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work by relabeling echoes as a peer.)
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**Convergence:** the **device is authoritative**. Its periodic `0x41` heartbeat
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is treated as ground truth, so if both sides edited the same field in the same
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instant, they reconcile within one heartbeat. To avoid flicker, a receiver
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should **diff the incoming `patch` against its current state and skip the
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rebuild if they're equal** (the editor does this in `_applyFull`), only
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reconciling transport.
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This is single‑user‑friendly (last‑writer‑wins per field). True simultaneous
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multi‑editor use is out of scope for the beta.
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---
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## 5. Handshake & lifecycle
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```
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editor "Live sync" ON ─► 0x40 HELLO ─────────────► device
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◄──────────── 0x41 FULL ◄── (device's current state)
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editor 0x41 FULL ──────────────────────────────► (editor's current state)
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… steady state: 0x42 deltas both ways, device 0x41 heartbeat …
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editor "Live sync" OFF ─► 0x43 BYE ────────────► device
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```
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On connect the editor sends **both** a `0x40` (asking for the device's state)
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and a `0x41` (offering its own), so whichever side the user considers "source of
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truth" wins immediately. A device that boots with sync idle should simply answer
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`0x40` with a `0x41` and start emitting deltas once it has heard from a peer.
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---
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## 6. Firmware checklist (`pico-cp/app.py`)
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- [ ] **Dispatch** `0x40/0x41/0x42` in the SysEx handler (~`app.py:1361‑1415`,
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alongside `0x01/0x02/0x10/0x21‑23`). Ignore frames whose origin is your own.
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- [ ] **HELLO (`0x40`)** → reply `0x41` FULL built from current `App` state
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(running, sl/idx, serialized program).
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- [ ] **FULL (`0x41`)** → diff vs. current program; if different, load it
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(reuse `parse_program()` / the `programs.json` load path); then reconcile
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`running` (start/stop). Wrap in your remote‑apply flag.
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- [ ] **DELTA (`0x42`)** → apply `play/stop/bpm/vol/sel/beat/lane` to `App`
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state, wrapped in the remote‑apply flag so the on‑device handlers don't
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re‑broadcast.
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- [ ] **Broadcast** a `0x42` from each on‑device input handler (button A,
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joystick tempo, touch beat edit, set‑list nav, lane editor), guarded by
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the remote‑apply flag. Structural lane changes → `0x41` FULL.
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- [ ] **Heartbeat:** emit `0x41` FULL every ~3–5 s while a peer is connected.
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- [ ] **BYE (`0x43`)** → mark the peer gone (stop heartbeating/emitting until
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the next HELLO).
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- [ ] **Throttle** high‑rate sources (joystick tempo) and keep frames small —
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the RP2040 USB‑MIDI RX buffer is tiny (the firmware updater already chunks
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at 64 bytes), and live traffic shares the bus with MIDI clock, note‑out,
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and the editor's Active‑Sensing heartbeat. Don't let a flood stall a
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concurrent firmware push.
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### Built‑in vs. user set lists (must match the editor)
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The PM_K‑1's built‑in playlists (Styles / Practice / Song) are **baked into
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firmware and read‑only**; on‑device edits **copy‑on‑write** into the user
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"My edits" list. The editor follows the same rule (`userSetlists()` excludes the
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seeded titles). So a **remote edit that targets a built‑in must follow the same
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copy‑on‑write semantics** on the receiving side, or the two halves will disagree
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about where the edit landed. When in doubt, after such an edit send a `0x41`
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FULL with the resulting (copied) program so both sides converge on the same
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target.
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### Out of scope for the beta
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- Streaming the device practice log (`history.json`) up to the browser.
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- Mirroring device `settings.json` (LED brightness, MIDI config, etc.).
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- Multi‑peer / multi‑editor arbitration beyond last‑writer‑wins.
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