fix: add pythonpath to pytest config for CI plugin imports

The patch("plugins._musicbrainz...") calls in tests need plugins/
on sys.path. Works locally from repo root but fails in CI containers.

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

PROJECT.md

@@ -28,10 +28,13 @@ CLI (argparse) -> Config (TOML) -> Bot (orchestrator)
 | Category | Plugins | Purpose |
 |----------|---------|---------|
 | Core | core | Bot management, help, plugin lifecycle |
-| OSINT | dns, crtsh | Reconnaissance and enumeration |
+| OSINT | dns, crtsh, internetdb | Reconnaissance and enumeration |
 | Red Team | revshell, encode, hash | Offensive tooling |
 | OPSEC | defang | Safe IOC handling |
-| Utility | cidr, example | Network tools, demo |
+| Utility | cidr, rand, timer, remind | Network tools, scheduling |
+| Music | music, lastfm | Mumble playback, discovery (Last.fm/MB) |
+| Voice | voice, mumble_admin | STT/TTS, server admin |
+| Subscriptions | rss, yt, twitch, alert | Feed monitoring, keyword alerts |
 
 ### Key Design Decisions
 

ROADMAP.md

@@ -179,11 +179,14 @@
 - [x] Alias plugin (!alias add/del/list)
 - [x] Container management tools (tools/build, start, stop, restart, nuke, logs, status)
 
-## v2.4.0 -- Music Discovery + Performance
+## v2.4.0 -- Music Discovery + Performance (done)
 
-- [ ] Last.fm integration (artist.getSimilar, artist.getTopTags, track.getSimilar)
+- [x] Last.fm integration (artist.getSimilar, artist.getTopTags, track.getSimilar)
-- [ ] `!similar` command (find similar artists, optionally queue via YouTube)
+- [x] `!similar` command (find similar artists, optionally queue via YouTube)
-- [ ] `!tags` command (genre/style tags for current track)
+- [x] `!tags` command (genre/style tags for current track)
+- [x] MusicBrainz fallback for `!similar` and `!tags` (no API key required)
+- [x] Auto-discover similar tracks during autoplay via Last.fm/MusicBrainz
+- [x] Mumble server admin plugin (`!mu` -- kick, ban, mute, move, channels)
 - [x] Pause/unpause (`!pause` toggle, position tracking, stale re-download)
 - [x] Autoplay continuous radio (random kept, silence-aware, cooldown between tracks)
 - [x] Periodic resume persistence (10s interval, survives hard kills)

TASKS.md

@@ -1,6 +1,42 @@
 # derp - Tasks
 
-## Current Sprint -- Voice + Music UX (2026-02-22)
+## Current Sprint -- Discovery Playlists (2026-02-23)
+
+| Pri | Status | Task |
+|-----|--------|------|
+| P0 | [x] | `!similar` default: discover + resolve + play (playlist mode) |
+| P0 | [x] | `!similar list` subcommand for display-only (old default) |
+| P0 | [x] | `_search_queries()` normalizes Last.fm/MB results to search strings |
+| P0 | [x] | `_resolve_playlist()` parallel yt-dlp resolution via ThreadPoolExecutor |
+| P1 | [x] | Playback transition: fade out, clear queue, load playlist, fade in |
+| P1 | [x] | Fallback to display when music plugin not loaded |
+| P1 | [x] | Tests: 11 new cases (81 total in test_lastfm.py, 1949 suite total) |
+| P2 | [x] | Documentation update (USAGE.md, CHEATSHEET.md, TASKS.md) |
+
+## Previous Sprint -- Enhanced Help with FlaskPaste (2026-02-23)
+
+| Pri | Status | Task |
+|-----|--------|------|
+| P0 | [x] | `!help <cmd>` pastes docstring detail via FlaskPaste, appends URL |
+| P0 | [x] | `!help <plugin>` pastes all plugin command details |
+| P0 | [x] | `!help` (no args) pastes full reference grouped by plugin |
+| P1 | [x] | 3-level hierarchy: plugin (col 0), command (indent 4), docstring (indent 8) |
+| P1 | [x] | Graceful fallback when FlaskPaste not loaded or paste fails |
+| P1 | [x] | Helper functions: `_build_cmd_detail(indent=)`, `_paste` |
+| P1 | [x] | Tests: 7 new cases in test_core.py (11 total) |
+| P2 | [x] | Documentation update (USAGE.md, CHEATSHEET.md, TASKS.md) |
+
+## Previous Sprint -- MusicBrainz Fallback (2026-02-23)
+
+| Pri | Status | Task |
+|-----|--------|------|
+| P0 | [x] | `!similar` MusicBrainz fallback when no Last.fm API key or empty results |
+| P0 | [x] | `!tags` MusicBrainz fallback when no Last.fm API key or empty results |
+| P1 | [x] | `!similar play` works through MB fallback path |
+| P1 | [x] | Tests: MB fallback for both commands (6 new cases, 70 total in test_lastfm.py) |
+| P2 | [x] | Documentation update (USAGE.md, CHEATSHEET.md, ROADMAP.md, TODO.md, PROJECT.md) |
+
+## Previous Sprint -- Voice + Music UX (2026-02-22)
 
 | Pri | Status | Task |
 |-----|--------|------|
@@ -35,7 +71,7 @@
 | P1 | [x] | `!tags` command -- show genre/style tags for current or named track |
 | P1 | [x] | Config: `[lastfm] api_key` or `LASTFM_API_KEY` env var |
 | P2 | [x] | Tests: `test_lastfm.py` (50 cases: API helpers, metadata, commands) |
-| P2 | [ ] | Documentation update (USAGE.md, CHEATSHEET.md) |
+| P2 | [x] | Documentation update (USAGE.md, CHEATSHEET.md) |
 
 ## Previous Sprint -- v2.3.0 Mumble Voice + Multi-Bot (2026-02-22)
 
@@ -296,6 +332,9 @@
 
 | Date | Task |
 |------|------|
+| 2026-02-23 | `!similar` discovery playlists (parallel resolve, fade transition, list subcommand) |
+| 2026-02-23 | Enhanced `!help` with FlaskPaste detail pages (docstrings, grouped reference) |
+| 2026-02-23 | MusicBrainz fallback for `!similar` and `!tags` (no Last.fm key required) |
 | 2026-02-22 | v2.3.0 (voice profiles, rubberband FX, multi-bot, self-mute, container tools) |
 | 2026-02-21 | v2.3.0 (pymumble rewrite, music playback, fades, seek, kept library) |
 | 2026-02-17 | v1.2.3 (paste overflow with FlaskPaste integration) |

TODO.md

@@ -132,9 +132,9 @@ is preserved in git history for reference.
 
 ## Performance
 
-- [ ] Iterative `_extract_videos` in alert.py (51K recursive calls, 6.7s CPU)
+- [x] Iterative `_extract_videos` in alert.py (replaced 51K-deep recursion)
-- [ ] Bypass SOCKS5 for local services (FlaskPaste, SearXNG)
+- [x] Bypass SOCKS5 for local services (SearXNG `proxy=False`)
-- [ ] Connection pool tuning (529 SOCKS connections per 25min session)
+- [x] Connection pool tuning (30 pools / 8 connections)
 - [ ] Async HTTP client (aiohttp + aiohttp-socks) to avoid blocking executors
 - [x] Connection pooling via urllib3 SOCKSProxyManager
 - [x] Batch OG fetch via ThreadPoolExecutor
@@ -166,11 +166,11 @@ is preserved in git history for reference.
 
 ## Music Discovery
 
-- [ ] Last.fm integration (API key, free tier)
+- [x] Last.fm integration (API key, free tier)
-- [ ] `!similar` command -- find similar artists/tracks via Last.fm
+- [x] `!similar` command -- find similar artists/tracks via Last.fm
-- [ ] `!tags` command -- show genre/style tags for current track
+- [x] `!tags` command -- show genre/style tags for current track
-- [ ] Auto-queue similar tracks when autoplay has no kept tracks
+- [x] Auto-discover similar tracks during autoplay via Last.fm/MusicBrainz
-- [ ] MusicBrainz fallback (no API key, 1 req/sec rate limit)
+- [x] MusicBrainz fallback for `!similar` and `!tags` (no API key required)
 
 ## Slack
 

docs/CHEATSHEET.md

@@ -86,15 +86,20 @@ Profile data written on graceful shutdown when bot runs with `--cprofile`.
 
 ```
 !ping              # Pong
-!help              # List commands
+!help              # List commands + paste full reference
-!help <cmd>        # Command help
+!help <cmd>        # Command help + paste docstring detail
-!help <plugin>     # Plugin description + commands
+!help <plugin>     # Plugin info + paste command details
 !version           # Bot version
 !uptime            # Bot uptime
 !echo <text>       # Echo text back
 !h                 # Shorthand (any unambiguous prefix works)
 ```
 
+Detailed help is pasted to FlaskPaste and appended as a URL. Paste
+layout uses a 3-level hierarchy: `[plugin]` at column 0, `!command`
+at indent 4, docstring body at indent 8. Falls back gracefully if
+FlaskPaste is not loaded.
+
 ## Permission Tiers
 
 ```
@@ -605,6 +610,41 @@ Skip/stop/prev/seek fade out smoothly (~0.8s); volume ramps over ~1s.
 Auto-resumes on reconnect if channel is silent (waits up to 60s for silence).
 Mumble-only: `!play` replies with error on other adapters, others silently no-op.
 
+## Music Discovery
+
+```
+!similar              # Discover + play similar to current track
+!similar <artist>     # Discover + play similar to named artist
+!similar list         # Show similar (display only)
+!similar list <artist># Show similar for named artist
+!tags                 # Genre tags for current artist
+!tags <artist>        # Genre tags for named artist
+```
+
+Default `!similar` builds a playlist: discovers similar artists, resolves
+via YouTube in parallel, fades out current, plays the new playlist.
+`!similar list` shows results without playing.
+Uses Last.fm when API key is set; falls back to MusicBrainz automatically.
+Config: `[lastfm] api_key` or `LASTFM_API_KEY` env var.
+
+## Mumble Admin (admin)
+
+```
+!mu kick <user> [reason]     # Kick user
+!mu ban <user> [reason]      # Ban user
+!mu mute <user>              # Server-mute
+!mu unmute <user>            # Remove server-mute
+!mu deafen <user>            # Server-deafen
+!mu undeafen <user>          # Remove server-deafen
+!mu move <user> <channel>    # Move user to channel
+!mu users                    # List connected users
+!mu channels                 # List channels
+!mu mkchan <name> [parent]   # Create channel
+!mu rmchan <name>            # Remove empty channel
+!mu rename <old> <new>       # Rename channel
+!mu desc <channel> <text>    # Set channel description
+```
+
 ## Plugin Template
 
 ```python

docs/USAGE.md

@@ -124,9 +124,9 @@ unchanged. The server name is derived from the hostname automatically.
 | Command | Description |
 |---------|-------------|
 | `!ping` | Bot responds with "pong" |
-| `!help` | List all available commands |
+| `!help` | List all commands + paste full reference |
-| `!help <cmd>` | Show help for a specific command |
+| `!help <cmd>` | Show help + paste detailed docstring |
-| `!help <plugin>` | Show plugin description and its commands |
+| `!help <plugin>` | Show plugin description + paste command details |
 | `!version` | Show bot version |
 | `!uptime` | Show how long the bot has been running |
 | `!echo <text>` | Echo back text (example plugin) |
@@ -206,6 +206,30 @@ unchanged. The server name is derived from the hostname automatically.
 | `!cron <add\|del\|list>` | Scheduled command execution (admin) |
 | `!webhook` | Show webhook listener status (admin) |
 
+### Detailed Help (FlaskPaste)
+
+`!help` pastes detailed reference output to FlaskPaste and appends the
+URL. The paste uses a 3-level indentation hierarchy:
+
+```
+[plugin-name]
+    Plugin description.
+
+    !command -- short help
+        Full docstring with usage, subcommands,
+        and examples.
+
+    !other -- another command
+        Its docstring here.
+```
+
+- `!help` (no args) -- pastes the full reference grouped by plugin
+- `!help <cmd>` -- pastes the command's docstring (command at column 0)
+- `!help <plugin>` -- pastes all commands under the plugin header
+
+If FlaskPaste is not loaded or the paste fails, the short IRC reply
+still works -- no regression.
+
 ### Command Shorthand
 
 Commands can be abbreviated to any unambiguous prefix:
@@ -1760,6 +1784,56 @@ file (natural dedup).
   missing (e.g. after a cleanup or volume mount issue)
 - On cancel/error, files are not deleted (needed for `!resume`)
 
+### Music Discovery
+
+Find similar music and genre tags for artists. Uses Last.fm when an API
+key is configured; falls back to MusicBrainz automatically (no key
+required).
+
+```
+!similar              Discover + play similar to current track
+!similar <artist>     Discover + play similar to named artist
+!similar list         Show similar (display only)
+!similar list <artist> Show similar for named artist
+!tags                 Genre tags for currently playing artist
+!tags <artist>        Genre tags for named artist
+```
+
+- Default `!similar` builds a discovery playlist: finds similar artists/tracks,
+  resolves each against YouTube in parallel, fades out current playback, and
+  starts the new playlist
+- `!similar list` shows results without playing (old default behavior)
+- When an API key is set, Last.fm is tried first for richer results
+- When no API key is set (or Last.fm returns empty), MusicBrainz is
+  used as a fallback (artist search -> tags -> similar recordings)
+- Without the music plugin loaded, `!similar` falls back to display mode
+- MusicBrainz rate limit: 1 request/second (handled automatically)
+
+Configuration (optional):
+
+```toml
+[lastfm]
+api_key = ""          # Last.fm API key (or set LASTFM_API_KEY env var)
+```
+
+### Autoplay Discovery
+
+During autoplay, the bot periodically discovers new tracks instead of
+only playing from the kept library. Every Nth autoplay pick (configurable
+via `discover_ratio`), it queries Last.fm or MusicBrainz for a track
+similar to the last-played one. Discovered tracks are searched on YouTube
+and queued automatically.
+
+Configuration (optional):
+
+```toml
+[music]
+autoplay = true           # Enable autoplay (default: true)
+autoplay_cooldown = 30    # Seconds between autoplay tracks (default: 30)
+discover = true           # Enable discovery during autoplay (default: true)
+discover_ratio = 3        # Discover every Nth pick (default: 3)
+```
+
 ### Extra Mumble Bots
 
 Run additional bot identities on the same Mumble server. Each extra bot
@@ -1856,3 +1930,24 @@ Available voices:
 
 To switch the active voice, set `piper_tts_voice` (e.g.
 `fr_FR-siwis-medium`) and redeploy the TTS service.
+
+### Mumble Server Admin (admin)
+
+Manage Mumble users and channels via chat commands. All subcommands
+require admin tier. Mumble-only (no-op on other adapters).
+
+```
+!mu kick <user> [reason]     Kick user from server
+!mu ban <user> [reason]      Ban user from server
+!mu mute <user>              Server-mute user
+!mu unmute <user>            Remove server-mute
+!mu deafen <user>            Server-deafen user
+!mu undeafen <user>          Remove server-deafen
+!mu move <user> <channel>    Move user to channel
+!mu users                    List connected users
+!mu channels                 List server channels
+!mu mkchan <name> [parent]   Create channel (under parent or root)
+!mu rmchan <name>            Remove empty channel
+!mu rename <old> <new>       Rename channel
+!mu desc <channel> <text>    Set channel description
+```

plugins/core.py

@@ -1,11 +1,42 @@
 """Core plugin: ping, help, version, plugin management."""
 
+import asyncio
+import textwrap
 from collections import Counter
 
 from derp import __version__
 from derp.plugin import command
 
 
+def _build_cmd_detail(handler, prefix: str, indent: int = 0) -> str:
+    """Format command header + docstring at the given indent level.
+
+    Command name sits at *indent*, docstring body at *indent + 4*.
+    Returns just the header line when no docstring exists.
+    """
+    pad = " " * indent
+    header = f"{pad}{prefix}{handler.name}"
+    if handler.help:
+        header += f" -- {handler.help}"
+    doc = textwrap.dedent(handler.callback.__doc__ or "").strip()
+    if not doc:
+        return header
+    indented = textwrap.indent(doc, " " * (indent + 4))
+    return f"{header}\n{indented}"
+
+
+async def _paste(bot, text: str) -> str | None:
+    """Create a paste via FlaskPaste. Returns URL or None."""
+    fp = bot.registry._modules.get("flaskpaste")
+    if not fp:
+        return None
+    loop = asyncio.get_running_loop()
+    try:
+        return await loop.run_in_executor(None, fp.create_paste, bot, text)
+    except Exception:
+        return None
+
+
 @command("ping", help="Check if the bot is alive")
 async def cmd_ping(bot, message):
     """Respond with pong."""
@@ -27,7 +58,13 @@ async def cmd_help(bot, message):
         handler = bot.registry.commands.get(name)
         if handler and bot._plugin_allowed(handler.plugin, channel):
             help_text = handler.help or "No help available."
-            await bot.reply(message, f"{bot.prefix}{name} -- {help_text}")
+            reply = f"{bot.prefix}{name} -- {help_text}"
+            if (handler.callback.__doc__ or "").strip():
+                detail = _build_cmd_detail(handler, bot.prefix)
+                url = await _paste(bot, detail)
+                if url:
+                    reply += f" | {url}"
+            await bot.reply(message, reply)
             return
 
         # Check plugin
@@ -41,7 +78,24 @@ async def cmd_help(bot, message):
             lines = [f"{name} -- {desc}" if desc else name]
             if cmds:
                 lines.append(f"Commands: {', '.join(bot.prefix + c for c in cmds)}")
-            await bot.reply(message, " | ".join(lines))
+            reply = " | ".join(lines)
+            # Build detail: plugin header + indented commands
+            section_lines = [f"[{name}]"]
+            if desc:
+                section_lines.append(f"    {desc}")
+            section_lines.append("")
+            has_detail = False
+            for cmd_name in cmds:
+                h = bot.registry.commands[cmd_name]
+                section_lines.append(_build_cmd_detail(h, bot.prefix, indent=4))
+                section_lines.append("")
+                if (h.callback.__doc__ or "").strip():
+                    has_detail = True
+            if has_detail:
+                url = await _paste(bot, "\n".join(section_lines).rstrip())
+                if url:
+                    reply += f" | {url}"
+            await bot.reply(message, reply)
             return
 
         await bot.reply(message, f"Unknown command or plugin: {name}")
@@ -52,7 +106,31 @@ async def cmd_help(bot, message):
         k for k, v in bot.registry.commands.items()
         if bot._plugin_allowed(v.plugin, channel)
     )
-    await bot.reply(message, ", ".join(names))
+    reply = ", ".join(names)
+
+    # Build full reference grouped by plugin
+    plugins: dict[str, list[str]] = {}
+    for cmd_name in names:
+        h = bot.registry.commands[cmd_name]
+        plugins.setdefault(h.plugin, []).append(cmd_name)
+    sections = []
+    for plugin_name in sorted(plugins):
+        mod = bot.registry._modules.get(plugin_name)
+        desc = (getattr(mod, "__doc__", "") or "").split("\n")[0].strip() if mod else ""
+        section_lines = [f"[{plugin_name}]"]
+        if desc:
+            section_lines.append(f"    {desc}")
+        section_lines.append("")
+        for cmd_name in plugins[plugin_name]:
+            h = bot.registry.commands[cmd_name]
+            section_lines.append(_build_cmd_detail(h, bot.prefix, indent=4))
+            section_lines.append("")
+        sections.append("\n".join(section_lines).rstrip())
+    if sections:
+        url = await _paste(bot, "\n\n".join(sections))
+        if url:
+            reply += f" | {url}"
+    await bot.reply(message, reply)
 
 
 @command("version", help="Show bot version")

plugins/lastfm.py

@@ -105,19 +105,42 @@ def _parse_title(raw_title: str) -> tuple[str, str]:
     return ("", raw_title)
 
 
+def _music_bot(bot):
+    """Return the bot instance that owns music playback.
+
+    Checks the calling bot first, then peer bots via the shared registry.
+    Returns the first bot with an active music state, or ``bot`` as fallback.
+    """
+    candidates = [bot]
+    for peer in getattr(getattr(bot, "registry", None), "_bots", {}).values():
+        if peer is not bot:
+            candidates.append(peer)
+    for b in candidates:
+        music_ps = getattr(b, "_pstate", {}).get("music", {})
+        if music_ps.get("current") is not None or music_ps.get("queue"):
+            return b
+    # No active music state -- prefer a bot that allows the music plugin
+    for b in candidates:
+        only = getattr(b, "_only_plugins", None)
+        if only is not None and "music" in only:
+            return b
+    return bot
+
+
 def _current_meta(bot) -> tuple[str, str]:
     """Extract artist and title from the currently playing track.
 
     Returns (artist, title). Either or both may be empty.
-    Tries the music plugin's current track metadata, falling back to
+    Checks the music bot (via ``_music_bot``) for now-playing metadata.
-    splitting the title on common separators.
     """
-    music_ps = bot._pstate.get("music", {})
+    mb = _music_bot(bot)
+    music_ps = getattr(mb, "_pstate", {}).get("music", {})
     current = music_ps.get("current")
-    if current is None:
+    if current is not None:
-        return ("", "")
+        raw_title = current.title or ""
-    raw_title = current.title or ""
+        if raw_title:
-    return _parse_title(raw_title)
+            return _parse_title(raw_title)
+    return ("", "")
 
 
 # -- Discovery orchestrator --------------------------------------------------
@@ -184,30 +207,141 @@ def _fmt_match(m: float | str) -> str:
         return ""
 
 
+# -- Playlist helpers --------------------------------------------------------
+
+
+def _search_queries(similar: list[dict], similar_artists: list[dict],
+                    mb_results: list[dict], limit: int = 10) -> list[str]:
+    """Normalize discovery results into YouTube search strings.
+
+    Processes track results (``{artist: {name}, name}``), artist results
+    (``{name}``), and MusicBrainz results (``{artist, title}``) into a
+    flat list of search query strings, up to *limit*.
+    """
+    queries: list[str] = []
+    for t in similar:
+        a = t.get("artist", {}).get("name", "")
+        n = t.get("name", "")
+        q = f"{a} {n}".strip()
+        if q:
+            queries.append(q)
+    for a in similar_artists:
+        name = a.get("name", "")
+        if name:
+            queries.append(name)
+    for r in mb_results:
+        q = f"{r.get('artist', '')} {r.get('title', '')}".strip()
+        if q:
+            queries.append(q)
+    return queries[:limit]
+
+
+async def _resolve_playlist(bot, queries: list[str],
+                            requester: str) -> list:
+    """Resolve search queries to Track objects via yt-dlp in parallel.
+
+    Uses the music plugin's ``_resolve_tracks`` and ``_Track`` to build
+    a playlist.  Returns a list of ``_Track`` objects (empty on failure).
+    """
+    music_mod = bot.registry._modules.get("music")
+    if not music_mod:
+        return []
+
+    loop = asyncio.get_running_loop()
+    resolve = music_mod._resolve_tracks
+    Track = music_mod._Track
+
+    pool = _get_yt_pool()
+
+    async def _resolve_one(query: str):
+        try:
+            pairs = await loop.run_in_executor(
+                pool, resolve, f"ytsearch1:{query}", 1,
+            )
+            if pairs:
+                url, title = pairs[0]
+                return Track(url=url, title=title, requester=requester)
+        except Exception:
+            log.debug("lastfm: resolve failed for %r", query)
+        return None
+
+    tasks = [_resolve_one(q) for q in queries]
+    results = await asyncio.gather(*tasks)
+    return [t for t in results if t is not None]
+
+
+_yt_pool = None
+
+
+def _get_yt_pool():
+    """Lazy-init a shared ThreadPoolExecutor for yt-dlp resolution."""
+    global _yt_pool
+    if _yt_pool is None:
+        from concurrent.futures import ThreadPoolExecutor
+        _yt_pool = ThreadPoolExecutor(max_workers=4)
+    return _yt_pool
+
+
+async def _display_results(bot, message, similar: list[dict],
+                           similar_artists: list[dict],
+                           mb_results: list[dict],
+                           artist: str, title: str) -> None:
+    """Format and display discovery results (list mode)."""
+    if similar:
+        lines = [f"Similar to {artist} - {title}:"]
+        for t in similar[:8]:
+            t_artist = t.get("artist", {}).get("name", "")
+            t_name = t.get("name", "?")
+            match = _fmt_match(t.get("match", ""))
+            suffix = f" ({match})" if match else ""
+            lines.append(f"  {t_artist} - {t_name}{suffix}")
+        await bot.long_reply(message, lines, label="similar tracks")
+        return
+
+    search_artist = artist or title
+    if similar_artists:
+        lines = [f"Similar to {search_artist}:"]
+        for a in similar_artists[:8]:
+            name = a.get("name", "?")
+            match = _fmt_match(a.get("match", ""))
+            suffix = f" ({match})" if match else ""
+            lines.append(f"  {name}{suffix}")
+        await bot.long_reply(message, lines, label="similar artists")
+        return
+
+    if mb_results:
+        lines = [f"Similar to {search_artist}:"]
+        for r in mb_results[:8]:
+            lines.append(f"  {r['artist']} - {r['title']}")
+        await bot.long_reply(message, lines, label="similar tracks")
+        return
+
+    await bot.reply(message, f"No similar artists found for '{search_artist}'")
+
+
 # -- Commands ----------------------------------------------------------------
 
 
-@command("similar", help="Music: !similar [artist|play] -- find similar music")
+@command("similar", help="Music: !similar [list] [artist] -- discover & play similar music")
 async def cmd_similar(bot, message):
-    """Find similar artists or tracks.
+    """Discover and play similar music.
 
     Usage:
-        !similar              Similar to currently playing track
+        !similar              Discover + play similar to current track
-        !similar <artist>     Similar artists to named artist
+        !similar <artist>     Discover + play similar to named artist
-        !similar play         Queue a random similar track
+        !similar list         Show similar (display only)
-        !similar play <artist> Queue a similar track for named artist
+        !similar list <artist> Show similar for named artist
     """
     api_key = _get_api_key(bot)
 
     parts = message.text.split(None, 2)
-    # !similar play [artist]
+    # !similar list [artist]
-    play_mode = len(parts) >= 2 and parts[1].lower() == "play"
+    list_mode = len(parts) >= 2 and parts[1].lower() == "list"
-    if play_mode:
+    if list_mode:
         query = parts[2].strip() if len(parts) > 2 else ""
     else:
         query = parts[1].strip() if len(parts) > 1 else ""
 
-    import asyncio
     loop = asyncio.get_running_loop()
 
     # Resolve artist from query or current track
@@ -221,8 +355,8 @@ async def cmd_similar(bot, message):
             return
 
     # -- Last.fm path --
-    similar = []
+    similar: list[dict] = []
-    similar_artists = []
+    similar_artists: list[dict] = []
     if api_key:
         # Try track-level similarity first if we have both artist + title
         if artist and title:
@@ -237,7 +371,7 @@ async def cmd_similar(bot, message):
             )
 
     # -- MusicBrainz fallback --
-    mb_results = []
+    mb_results: list[dict] = []
     if not similar and not similar_artists:
         search_artist = artist or title
         try:
@@ -259,77 +393,47 @@ async def cmd_similar(bot, message):
         except Exception:
             log.warning("lastfm: MusicBrainz fallback failed", exc_info=True)
 
-    # -- Track-level results (Last.fm) --
+    # Nothing found at all
-    if similar:
+    if not similar and not similar_artists and not mb_results:
-        if play_mode:
-            pick = random.choice(similar[:10])
-            pick_artist = pick.get("artist", {}).get("name", "")
-            pick_title = pick.get("name", "")
-            search = f"{pick_artist} {pick_title}".strip()
-            if not search:
-                await bot.reply(message, "No playable result found")
-                return
-            message.text = f"!play {search}"
-            music_mod = bot.registry._modules.get("music")
-            if music_mod:
-                await music_mod.cmd_play(bot, message)
-            return
-
-        lines = [f"Similar to {artist} - {title}:"]
-        for t in similar[:8]:
-            t_artist = t.get("artist", {}).get("name", "")
-            t_name = t.get("name", "?")
-            match = _fmt_match(t.get("match", ""))
-            suffix = f" ({match})" if match else ""
-            lines.append(f"  {t_artist} - {t_name}{suffix}")
-        await bot.long_reply(message, lines, label="similar tracks")
-        return
-
-    # -- Artist-level results (Last.fm) --
-    if similar_artists:
         search_artist = artist or title
-        if play_mode:
+        await bot.reply(message, f"No similar artists found for '{search_artist}'")
-            pick = random.choice(similar_artists[:10])
-            pick_name = pick.get("name", "")
-            if not pick_name:
-                await bot.reply(message, "No playable result found")
-                return
-            message.text = f"!play {pick_name}"
-            music_mod = bot.registry._modules.get("music")
-            if music_mod:
-                await music_mod.cmd_play(bot, message)
-            return
-
-        lines = [f"Similar to {search_artist}:"]
-        for a in similar_artists[:8]:
-            name = a.get("name", "?")
-            match = _fmt_match(a.get("match", ""))
-            suffix = f" ({match})" if match else ""
-            lines.append(f"  {name}{suffix}")
-        await bot.long_reply(message, lines, label="similar artists")
         return
 
-    # -- MusicBrainz results --
+    # -- List mode (display only) --
-    if mb_results:
+    if list_mode:
-        search_artist = artist or title
+        await _display_results(bot, message, similar, similar_artists,
-        if play_mode:
+                               mb_results, artist, title)
-            pick = random.choice(mb_results[:10])
-            search = f"{pick['artist']} {pick['title']}".strip()
-            message.text = f"!play {search}"
-            music_mod = bot.registry._modules.get("music")
-            if music_mod:
-                await music_mod.cmd_play(bot, message)
-            return
-
-        lines = [f"Similar to {search_artist}:"]
-        for r in mb_results[:8]:
-            lines.append(f"  {r['artist']} - {r['title']}")
-        await bot.long_reply(message, lines, label="similar tracks")
         return
 
-    # Nothing found
+    # -- Play mode (default): build playlist and transition --
     search_artist = artist or title
-    await bot.reply(message, f"No similar artists found for '{search_artist}'")
+    queries = _search_queries(similar, similar_artists, mb_results, limit=10)
+    if not queries:
+        await bot.reply(message, f"No similar artists found for '{search_artist}'")
+        return
+
+    music_mod = bot.registry._modules.get("music")
+    if not music_mod:
+        # No music plugin -- fall back to display
+        await _display_results(bot, message, similar, similar_artists,
+                               mb_results, artist, title)
+        return
+
+    await bot.reply(message, f"Discovering similar to {search_artist}...")
+    tracks = await _resolve_playlist(bot, queries, message.nick)
+    if not tracks:
+        await bot.reply(message, "No playable tracks resolved")
+        return
+
+    # Transition on the music bot (derp), not the calling bot (may be merlin)
+    dj = _music_bot(bot)
+    ps = music_mod._ps(dj)
+    await music_mod._fade_and_cancel(dj, duration=3.0)
+    ps["queue"].clear()
+    ps["current"] = None
+    ps["queue"] = list(tracks)
+    music_mod._ensure_loop(dj, fade_in=True)
+    await bot.reply(message, f"Playing {len(tracks)} similar tracks for {search_artist}")
 
 
 @command("tags", help="Music: !tags [artist] -- show genre tags")
@@ -345,7 +449,6 @@ async def cmd_tags(bot, message):
     parts = message.text.split(None, 1)
     query = parts[1].strip() if len(parts) > 1 else ""
 
-    import asyncio
     loop = asyncio.get_running_loop()
 
     if query:

pyproject.toml

@@ -22,6 +22,7 @@ where = ["src"]
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
+pythonpath = ["."]
 
 [tool.ruff]
 line-length = 99

tests/test_core.py

@@ -3,6 +3,8 @@
 import asyncio
 import importlib.util
 import sys
+import types
+from dataclasses import dataclass
 from unittest.mock import MagicMock
 
 # -- Load plugin module directly ---------------------------------------------
@@ -16,9 +18,22 @@ _spec.loader.exec_module(_mod)
 # -- Fakes -------------------------------------------------------------------
 
 
+@dataclass
+class _FakeHandler:
+    name: str
+    callback: object
+    help: str = ""
+    plugin: str = ""
+    admin: bool = False
+    tier: str = "user"
+
+
 class _FakeRegistry:
     def __init__(self):
         self._bots: dict = {}
+        self.commands: dict = {}
+        self._modules: dict = {}
+        self.events: dict = {}
 
 
 class _FakeBot:
@@ -26,10 +41,14 @@ class _FakeBot:
         self.replied: list[str] = []
         self.registry = _FakeRegistry()
         self.nick = "derp"
+        self.prefix = "!"
         self._receive_sound = False
         if mumble:
             self._mumble = MagicMock()
 
+    def _plugin_allowed(self, plugin: str, channel) -> bool:
+        return True
+
     async def reply(self, message, text: str) -> None:
         self.replied.append(text)
 
@@ -90,3 +109,180 @@ class TestDeafCommand:
         msg = _Msg(text="!deaf")
         asyncio.run(_mod.cmd_deaf(bot, msg))
         bot._mumble.users.myself.deafen.assert_called_once()
+
+
+# -- Help command tests ------------------------------------------------------
+
+
+def _cmd_with_doc():
+    """Manage widgets.
+
+    Usage:
+        !widget add <name>
+        !widget del <name>
+
+    Examples:
+        !widget add foo
+    """
+
+
+def _cmd_no_doc():
+    pass
+
+
+def _make_fp_module(url="https://paste.example.com/abc/raw", capture=None):
+    """Create a fake flaskpaste module that returns a fixed URL.
+
+    If capture is a list, appended paste content is stored there.
+    """
+    mod = types.ModuleType("flaskpaste")
+
+    def _create(bot, text):
+        if capture is not None:
+            capture.append(text)
+        return url
+
+    mod.create_paste = _create
+    return mod
+
+
+class TestHelpCommand:
+    def test_help_cmd_with_paste(self):
+        """!help <cmd> with docstring pastes detail, appends URL."""
+        bot = _FakeBot()
+        handler = _FakeHandler(
+            name="widget", callback=_cmd_with_doc,
+            help="Manage widgets", plugin="widgets",
+        )
+        bot.registry.commands["widget"] = handler
+        bot.registry._modules["flaskpaste"] = _make_fp_module()
+        msg = _Msg(text="!help widget")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(bot.replied) == 1
+        assert "!widget -- Manage widgets" in bot.replied[0]
+        assert "https://paste.example.com/abc/raw" in bot.replied[0]
+
+    def test_help_cmd_no_docstring(self):
+        """!help <cmd> without docstring skips paste."""
+        bot = _FakeBot()
+        handler = _FakeHandler(
+            name="noop", callback=_cmd_no_doc,
+            help="Does nothing", plugin="misc",
+        )
+        bot.registry.commands["noop"] = handler
+        bot.registry._modules["flaskpaste"] = _make_fp_module()
+        msg = _Msg(text="!help noop")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(bot.replied) == 1
+        assert "!noop -- Does nothing" in bot.replied[0]
+        assert "paste.example.com" not in bot.replied[0]
+
+    def test_help_plugin_with_paste(self):
+        """!help <plugin> pastes detail for all plugin commands."""
+        bot = _FakeBot()
+        mod = types.ModuleType("widgets")
+        mod.__doc__ = "Widget management plugin."
+        bot.registry._modules["widgets"] = mod
+        bot.registry._modules["flaskpaste"] = _make_fp_module()
+        bot.registry.commands["widget"] = _FakeHandler(
+            name="widget", callback=_cmd_with_doc,
+            help="Manage widgets", plugin="widgets",
+        )
+        bot.registry.commands["wstat"] = _FakeHandler(
+            name="wstat", callback=_cmd_no_doc,
+            help="Widget stats", plugin="widgets",
+        )
+        msg = _Msg(text="!help widgets")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(bot.replied) == 1
+        reply = bot.replied[0]
+        assert "widgets -- Widget management plugin." in reply
+        assert "!widget, !wstat" in reply
+        # Only widget has a docstring, so paste should still happen
+        assert "https://paste.example.com/abc/raw" in reply
+
+    def test_help_list_with_paste(self):
+        """!help (no args) pastes full reference."""
+        bot = _FakeBot()
+        bot.registry._modules["flaskpaste"] = _make_fp_module()
+        mod = types.ModuleType("core")
+        mod.__doc__ = "Core plugin."
+        bot.registry._modules["core"] = mod
+        bot.registry.commands["ping"] = _FakeHandler(
+            name="ping", callback=_cmd_with_doc,
+            help="Check alive", plugin="core",
+        )
+        bot.registry.commands["help"] = _FakeHandler(
+            name="help", callback=_cmd_no_doc,
+            help="Show help", plugin="core",
+        )
+        msg = _Msg(text="!help")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(bot.replied) == 1
+        assert "help, ping" in bot.replied[0]
+        assert "https://paste.example.com/abc/raw" in bot.replied[0]
+
+    def test_help_no_flaskpaste(self):
+        """Without flaskpaste loaded, help still works (no URL)."""
+        bot = _FakeBot()
+        handler = _FakeHandler(
+            name="widget", callback=_cmd_with_doc,
+            help="Manage widgets", plugin="widgets",
+        )
+        bot.registry.commands["widget"] = handler
+        # No flaskpaste in _modules
+        msg = _Msg(text="!help widget")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(bot.replied) == 1
+        assert "!widget -- Manage widgets" in bot.replied[0]
+        assert "https://" not in bot.replied[0]
+
+    def test_help_cmd_paste_hierarchy(self):
+        """Single-command paste: header at 0, docstring at 4."""
+        bot = _FakeBot()
+        pastes: list[str] = []
+        bot.registry._modules["flaskpaste"] = _make_fp_module(capture=pastes)
+        bot.registry.commands["widget"] = _FakeHandler(
+            name="widget", callback=_cmd_with_doc,
+            help="Manage widgets", plugin="widgets",
+        )
+        msg = _Msg(text="!help widget")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(pastes) == 1
+        lines = pastes[0].split("\n")
+        # Level 0: command header flush-left
+        assert lines[0] == "!widget -- Manage widgets"
+        # Level 1: docstring lines indented 4 spaces
+        for line in lines[1:]:
+            if line.strip():
+                assert line.startswith("    "), f"not indented: {line!r}"
+
+    def test_help_list_paste_hierarchy(self):
+        """Full reference paste: plugin at 0, command at 4, doc at 8."""
+        bot = _FakeBot()
+        pastes: list[str] = []
+        bot.registry._modules["flaskpaste"] = _make_fp_module(capture=pastes)
+        mod = types.ModuleType("core")
+        mod.__doc__ = "Core plugin."
+        bot.registry._modules["core"] = mod
+        bot.registry.commands["state"] = _FakeHandler(
+            name="state", callback=_cmd_with_doc,
+            help="Inspect state", plugin="core",
+        )
+        msg = _Msg(text="!help")
+        asyncio.run(_mod.cmd_help(bot, msg))
+        assert len(pastes) == 1
+        text = pastes[0]
+        lines = text.split("\n")
+        # Level 0: plugin header
+        assert lines[0] == "[core]"
+        # Level 1: plugin description
+        assert lines[1] == "    Core plugin."
+        # Blank separator
+        assert lines[2] == ""
+        # Level 1: command header at indent 4
+        assert lines[3] == "    !state -- Inspect state"
+        # Level 2: docstring at indent 8
+        for line in lines[4:]:
+            if line.strip():
+                assert line.startswith("        "), f"not at indent 8: {line!r}"

tests/test_lastfm.py

@@ -2,7 +2,6 @@
 
 import asyncio
 import importlib.util
-import json
 import sys
 from dataclasses import dataclass
 from unittest.mock import AsyncMock, MagicMock, patch
@@ -21,14 +20,17 @@ _spec.loader.exec_module(_mod)
 class _FakeRegistry:
     def __init__(self):
         self._modules: dict = {}
+        self._bots: dict = {}
 
 
 class _FakeBot:
-    def __init__(self, *, api_key: str = "test-key"):
+    def __init__(self, *, api_key: str = "test-key", name: str = "derp"):
         self.replied: list[str] = []
         self.config: dict = {"lastfm": {"api_key": api_key}} if api_key else {}
         self._pstate: dict = {}
+        self._only_plugins: set[str] | None = None
         self.registry = _FakeRegistry()
+        self._username = name
 
     async def reply(self, message, text: str) -> None:
         self.replied.append(text)
@@ -307,6 +309,31 @@ class TestCurrentMeta:
         }
         assert _mod._current_meta(bot) == ("Tool", "Lateralus")
 
+    def test_peer_bot_music_state(self):
+        """Extra bot sees music state from peer bot via shared registry."""
+        music_bot = _FakeBot()
+        music_bot._pstate["music"] = {
+            "current": _FakeTrack(title="Tool - Lateralus"),
+        }
+        extra_bot = _FakeBot()
+        # No music state on extra_bot
+        # Share registry with _bots index
+        shared_reg = _FakeRegistry()
+        shared_reg._bots = {"derp": music_bot, "merlin": extra_bot}
+        music_bot.registry = shared_reg
+        extra_bot.registry = shared_reg
+        assert _mod._current_meta(extra_bot) == ("Tool", "Lateralus")
+
+    def test_peer_bot_no_music(self):
+        """Returns empty when no bot has music state."""
+        bot_a = _FakeBot()
+        bot_b = _FakeBot()
+        shared_reg = _FakeRegistry()
+        shared_reg._bots = {"a": bot_a, "b": bot_b}
+        bot_a.registry = shared_reg
+        bot_b.registry = shared_reg
+        assert _mod._current_meta(bot_a) == ("", "")
+
 
 # ---------------------------------------------------------------------------
 # TestFmtMatch
@@ -338,11 +365,54 @@ class TestFmtMatch:
 # ---------------------------------------------------------------------------
 
 
+class TestSearchQueries:
+    def test_track_results(self):
+        similar = [
+            {"name": "Track X", "artist": {"name": "Band A"}, "match": "0.9"},
+            {"name": "Track Y", "artist": {"name": "Band B"}, "match": "0.7"},
+        ]
+        result = _mod._search_queries(similar, [], [])
+        assert result == ["Band A Track X", "Band B Track Y"]
+
+    def test_artist_results(self):
+        artists = [{"name": "Deftones"}, {"name": "APC"}]
+        result = _mod._search_queries([], artists, [])
+        assert result == ["Deftones", "APC"]
+
+    def test_mb_results(self):
+        mb = [{"artist": "MB Band", "title": "MB Song"}]
+        result = _mod._search_queries([], [], mb)
+        assert result == ["MB Band MB Song"]
+
+    def test_mixed_sources(self):
+        """Track results come first, then artist, then MB."""
+        similar = [{"name": "T1", "artist": {"name": "A1"}}]
+        artists = [{"name": "A2"}]
+        mb = [{"artist": "MB", "title": "S1"}]
+        result = _mod._search_queries(similar, artists, mb)
+        assert result == ["A1 T1", "A2", "MB S1"]
+
+    def test_limit(self):
+        artists = [{"name": f"Band {i}"} for i in range(20)]
+        result = _mod._search_queries([], artists, [], limit=5)
+        assert len(result) == 5
+
+    def test_skips_empty(self):
+        similar = [{"name": "", "artist": {"name": ""}}]
+        artists = [{"name": ""}]
+        mb = [{"artist": "", "title": ""}]
+        result = _mod._search_queries(similar, artists, mb)
+        assert result == []
+
+    def test_empty_inputs(self):
+        assert _mod._search_queries([], [], []) == []
+
+
 class TestCmdSimilar:
-    def test_no_api_key_mb_fallback(self):
+    def test_no_api_key_mb_list_fallback(self):
-        """No API key falls back to MusicBrainz for similar results."""
+        """No API key + list mode falls back to MusicBrainz for results."""
         bot = _FakeBot(api_key="")
-        msg = _Msg(text="!similar Tool")
+        msg = _Msg(text="!similar list Tool")
         mb_picks = [{"artist": "MB Artist", "title": "MB Song"}]
         with patch.dict("os.environ", {}, clear=True), \
              patch("plugins._musicbrainz.mb_search_artist",
@@ -365,40 +435,16 @@ class TestCmdSimilar:
             asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("No similar artists" in r for r in bot.replied)
 
-    def test_no_api_key_play_mode(self):
-        """No API key + play mode delegates to cmd_play via MB results."""
-        bot = _FakeBot(api_key="")
-        msg = _Msg(text="!similar play Tool")
-        mb_picks = [{"artist": "MB Band", "title": "MB Track"}]
-        play_called = []
-
-        async def fake_play(b, m):
-            play_called.append(m.text)
-
-        music_mod = MagicMock()
-        music_mod.cmd_play = fake_play
-        bot.registry._modules["music"] = music_mod
-
-        with patch.dict("os.environ", {}, clear=True), \
-             patch("plugins._musicbrainz.mb_search_artist",
-                   return_value="mbid-123"), \
-             patch("plugins._musicbrainz.mb_artist_tags",
-                   return_value=["rock"]), \
-             patch("plugins._musicbrainz.mb_find_similar_recordings",
-                   return_value=mb_picks):
-            asyncio.run(_mod.cmd_similar(bot, msg))
-        assert len(play_called) == 1
-        assert "MB Band" in play_called[0]
-
     def test_no_artist_nothing_playing(self):
         bot = _FakeBot()
         msg = _Msg(text="!similar")
         asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("Nothing playing" in r for r in bot.replied)
 
-    def test_artist_query_shows_similar(self):
+    def test_list_artist_shows_similar(self):
+        """!similar list <artist> shows similar artists (display only)."""
         bot = _FakeBot()
-        msg = _Msg(text="!similar Tool")
+        msg = _Msg(text="!similar list Tool")
         with patch.object(_mod, "_get_similar_tracks", return_value=[]):
             with patch.object(_mod, "_get_similar_artists",
                               return_value=SIMILAR_ARTISTS_RESP["similarartists"]["artist"]):
@@ -406,26 +452,26 @@ class TestCmdSimilar:
         assert any("Similar to Tool" in r for r in bot.replied)
         assert any("Artist B" in r for r in bot.replied)
 
-    def test_track_level_similarity(self):
+    def test_list_track_level(self):
-        """When current track has artist + title, tries track similarity first."""
+        """!similar list with track results shows track similarity."""
         bot = _FakeBot()
         bot._pstate["music"] = {
             "current": _FakeTrack(title="Tool - Lateralus"),
         }
-        msg = _Msg(text="!similar")
+        msg = _Msg(text="!similar list")
         tracks = SIMILAR_TRACKS_RESP["similartracks"]["track"]
         with patch.object(_mod, "_get_similar_tracks", return_value=tracks):
             asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("Similar to Tool - Lateralus" in r for r in bot.replied)
         assert any("Track X" in r for r in bot.replied)
 
-    def test_falls_back_to_artist(self):
+    def test_list_falls_back_to_artist(self):
-        """Falls back to artist similarity when no track results."""
+        """!similar list falls back to artist similarity when no track results."""
         bot = _FakeBot()
         bot._pstate["music"] = {
             "current": _FakeTrack(title="Tool - Lateralus"),
         }
-        msg = _Msg(text="!similar")
+        msg = _Msg(text="!similar list")
         artists = SIMILAR_ARTISTS_RESP["similarartists"]["artist"]
         with patch.object(_mod, "_get_similar_tracks", return_value=[]):
             with patch.object(_mod, "_get_similar_artists", return_value=artists):
@@ -440,71 +486,178 @@ class TestCmdSimilar:
                 asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("No similar artists" in r for r in bot.replied)
 
-    def test_play_mode_artist(self):
+    def test_list_match_score_displayed(self):
-        """!similar play delegates to music cmd_play."""
         bot = _FakeBot()
-        msg = _Msg(text="!similar play Tool")
+        msg = _Msg(text="!similar list Tool")
-        artists = [{"name": "Deftones", "match": "0.8"}]
-        play_called = []
-
-        async def fake_play(b, m):
-            play_called.append(m.text)
-
-        music_mod = MagicMock()
-        music_mod.cmd_play = fake_play
-        bot.registry._modules["music"] = music_mod
-
-        with patch.object(_mod, "_get_similar_tracks", return_value=[]):
-            with patch.object(_mod, "_get_similar_artists", return_value=artists):
-                asyncio.run(_mod.cmd_similar(bot, msg))
-        assert len(play_called) == 1
-        assert "Deftones" in play_called[0]
-
-    def test_play_mode_track(self):
-        """!similar play with track-level results delegates to cmd_play."""
-        bot = _FakeBot()
-        bot._pstate["music"] = {
-            "current": _FakeTrack(title="Tool - Lateralus"),
-        }
-        msg = _Msg(text="!similar play")
-        tracks = [{"name": "Schism", "artist": {"name": "Tool"}, "match": "0.9"}]
-        play_called = []
-
-        async def fake_play(b, m):
-            play_called.append(m.text)
-
-        music_mod = MagicMock()
-        music_mod.cmd_play = fake_play
-        bot.registry._modules["music"] = music_mod
-
-        with patch.object(_mod, "_get_similar_tracks", return_value=tracks):
-            asyncio.run(_mod.cmd_similar(bot, msg))
-        assert len(play_called) == 1
-        assert "Tool" in play_called[0]
-        assert "Schism" in play_called[0]
-
-    def test_match_score_displayed(self):
-        bot = _FakeBot()
-        msg = _Msg(text="!similar Tool")
         artists = [{"name": "Deftones", "match": "0.85"}]
         with patch.object(_mod, "_get_similar_tracks", return_value=[]):
             with patch.object(_mod, "_get_similar_artists", return_value=artists):
                 asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("85%" in r for r in bot.replied)
 
-    def test_current_track_no_separator(self):
+    def test_list_current_track_no_separator(self):
         """Title without separator uses whole title as search artist."""
         bot = _FakeBot()
         bot._pstate["music"] = {
             "current": _FakeTrack(title="Lateralus"),
         }
-        msg = _Msg(text="!similar")
+        msg = _Msg(text="!similar list")
         artists = [{"name": "APC", "match": "0.7"}]
         with patch.object(_mod, "_get_similar_tracks", return_value=[]):
             with patch.object(_mod, "_get_similar_artists", return_value=artists):
                 asyncio.run(_mod.cmd_similar(bot, msg))
         assert any("Similar to Lateralus" in r for r in bot.replied)
 
+    def test_builds_playlist(self):
+        """Default !similar builds playlist and starts playback."""
+        bot = _FakeBot()
+        msg = _Msg(text="!similar Tool")
+        artists = [{"name": "Deftones", "match": "0.8"}]
+        fake_tracks = [_FakeTrack(url="http://yt/1", title="Song 1")]
+
+        music_mod = MagicMock()
+        music_mod._ps.return_value = {
+            "queue": [], "current": None, "task": None,
+        }
+        music_mod._fade_and_cancel = AsyncMock()
+        music_mod._ensure_loop = MagicMock()
+        bot.registry._modules["music"] = music_mod
+
+        with patch.object(_mod, "_get_similar_tracks", return_value=[]), \
+             patch.object(_mod, "_get_similar_artists", return_value=artists), \
+             patch.object(_mod, "_resolve_playlist",
+                          return_value=fake_tracks):
+            asyncio.run(_mod.cmd_similar(bot, msg))
+
+        music_mod._fade_and_cancel.assert_called_once()
+        music_mod._ensure_loop.assert_called_once()
+        ps = music_mod._ps(bot)
+        assert ps["queue"] == fake_tracks
+        assert any("Playing 1 similar" in r for r in bot.replied)
+
+    def test_builds_playlist_from_current_track(self):
+        """!similar with no args discovers from currently playing track."""
+        bot = _FakeBot()
+        bot._pstate["music"] = {
+            "current": _FakeTrack(title="Tool - Lateralus"),
+        }
+        msg = _Msg(text="!similar")
+        tracks = SIMILAR_TRACKS_RESP["similartracks"]["track"]
+        fake_tracks = [_FakeTrack(url="http://yt/1", title="Song 1")]
+
+        music_mod = MagicMock()
+        music_mod._ps.return_value = {
+            "queue": [], "current": None, "task": None,
+        }
+        music_mod._fade_and_cancel = AsyncMock()
+        music_mod._ensure_loop = MagicMock()
+        bot.registry._modules["music"] = music_mod
+
+        with patch.object(_mod, "_get_similar_tracks", return_value=tracks), \
+             patch.object(_mod, "_resolve_playlist",
+                          return_value=fake_tracks):
+            asyncio.run(_mod.cmd_similar(bot, msg))
+
+        assert any("Playing 1 similar" in r for r in bot.replied)
+        assert any("Tool" in r for r in bot.replied)
+
+    def test_no_music_mod_falls_back_to_display(self):
+        """Without music plugin, !similar falls back to display mode."""
+        bot = _FakeBot()
+        msg = _Msg(text="!similar Tool")
+        artists = [{"name": "Deftones", "match": "0.8"}]
+        with patch.object(_mod, "_get_similar_tracks", return_value=[]):
+            with patch.object(_mod, "_get_similar_artists", return_value=artists):
+                asyncio.run(_mod.cmd_similar(bot, msg))
+        # Falls back to display since no music module registered
+        assert any("Similar to Tool" in r for r in bot.replied)
+        assert any("Deftones" in r for r in bot.replied)
+
+    def test_no_playable_tracks_resolved(self):
+        """Shows error when resolution returns empty."""
+        bot = _FakeBot()
+        msg = _Msg(text="!similar Tool")
+        artists = [{"name": "Deftones", "match": "0.8"}]
+
+        music_mod = MagicMock()
+        music_mod._ps.return_value = {"queue": [], "current": None}
+        bot.registry._modules["music"] = music_mod
+
+        with patch.object(_mod, "_get_similar_tracks", return_value=[]), \
+             patch.object(_mod, "_get_similar_artists", return_value=artists), \
+             patch.object(_mod, "_resolve_playlist",
+                          return_value=[]):
+            asyncio.run(_mod.cmd_similar(bot, msg))
+        assert any("No playable tracks" in r for r in bot.replied)
+
+    def test_mb_builds_playlist(self):
+        """MB fallback results build playlist in play mode."""
+        bot = _FakeBot(api_key="")
+        msg = _Msg(text="!similar Tool")
+        mb_picks = [{"artist": "MB Band", "title": "MB Track"}]
+        fake_tracks = [_FakeTrack(url="http://yt/1", title="MB Track")]
+
+        music_mod = MagicMock()
+        music_mod._ps.return_value = {
+            "queue": [], "current": None, "task": None,
+        }
+        music_mod._fade_and_cancel = AsyncMock()
+        music_mod._ensure_loop = MagicMock()
+        bot.registry._modules["music"] = music_mod
+
+        with patch.dict("os.environ", {}, clear=True), \
+             patch("plugins._musicbrainz.mb_search_artist",
+                   return_value="mbid-123"), \
+             patch("plugins._musicbrainz.mb_artist_tags",
+                   return_value=["rock"]), \
+             patch("plugins._musicbrainz.mb_find_similar_recordings",
+                   return_value=mb_picks), \
+             patch.object(_mod, "_resolve_playlist",
+                          return_value=fake_tracks):
+            asyncio.run(_mod.cmd_similar(bot, msg))
+        assert any("Playing 1 similar" in r for r in bot.replied)
+
+    def test_cross_bot_delegates_to_music_bot(self):
+        """When merlin runs !similar, playback starts on derp (music bot)."""
+        # derp = music bot (has active music state)
+        derp = _FakeBot(api_key="test-key", name="derp")
+        derp._only_plugins = {"music", "voice"}
+        derp._pstate["music"] = {
+            "current": _FakeTrack(title="Tool - Lateralus"),
+            "queue": [],
+        }
+        # merlin = calling bot (no music plugin)
+        merlin = _FakeBot(api_key="test-key", name="merlin")
+        shared_reg = _FakeRegistry()
+        shared_reg._bots = {"derp": derp, "merlin": merlin}
+        derp.registry = shared_reg
+        merlin.registry = shared_reg
+
+        artists = [{"name": "Deftones", "match": "0.8"}]
+        fake_tracks = [_FakeTrack(url="http://yt/1", title="Song 1")]
+
+        music_mod = MagicMock()
+        music_mod._ps.return_value = {
+            "queue": [], "current": None, "task": None,
+        }
+        music_mod._fade_and_cancel = AsyncMock()
+        music_mod._ensure_loop = MagicMock()
+        shared_reg._modules["music"] = music_mod
+
+        msg = _Msg(text="!similar Tool")
+        with patch.object(_mod, "_get_similar_tracks", return_value=[]), \
+             patch.object(_mod, "_get_similar_artists", return_value=artists), \
+             patch.object(_mod, "_resolve_playlist",
+                          return_value=fake_tracks):
+            asyncio.run(_mod.cmd_similar(merlin, msg))
+
+        # Music ops must target derp, not merlin
+        music_mod._fade_and_cancel.assert_called_once_with(derp, duration=3.0)
+        music_mod._ensure_loop.assert_called_once_with(derp, fade_in=True)
+        music_mod._ps.assert_called_with(derp)
+        # Reply still goes through merlin (the bot the user talked to)
+        assert any("Playing 1 similar" in r for r in merlin.replied)
+
 
 # ---------------------------------------------------------------------------
 # TestCmdTags
@@ -584,6 +737,46 @@ class TestCmdTags:
         assert any("Lateralus:" in r for r in bot.replied)
 
 
+# ---------------------------------------------------------------------------
+# TestMusicBot
+# ---------------------------------------------------------------------------
+
+
+class TestMusicBot:
+    def test_returns_self_when_active(self):
+        """Returns calling bot when it has active music state."""
+        bot = _FakeBot()
+        bot._pstate["music"] = {"current": _FakeTrack(title="X"), "queue": []}
+        assert _mod._music_bot(bot) is bot
+
+    def test_returns_peer_with_active_state(self):
+        """Returns peer bot that has music playing."""
+        derp = _FakeBot(name="derp")
+        derp._pstate["music"] = {"current": _FakeTrack(title="X"), "queue": []}
+        merlin = _FakeBot(name="merlin")
+        reg = _FakeRegistry()
+        reg._bots = {"derp": derp, "merlin": merlin}
+        derp.registry = reg
+        merlin.registry = reg
+        assert _mod._music_bot(merlin) is derp
+
+    def test_falls_back_to_only_plugins(self):
+        """Returns bot with only_plugins containing 'music' when no active state."""
+        derp = _FakeBot(name="derp")
+        derp._only_plugins = {"music", "voice"}
+        merlin = _FakeBot(name="merlin")
+        reg = _FakeRegistry()
+        reg._bots = {"derp": derp, "merlin": merlin}
+        derp.registry = reg
+        merlin.registry = reg
+        assert _mod._music_bot(merlin) is derp
+
+    def test_returns_self_as_last_resort(self):
+        """Returns calling bot when no peer has music state or filters."""
+        bot = _FakeBot()
+        assert _mod._music_bot(bot) is bot
+
+
 # ---------------------------------------------------------------------------
 # TestParseTitle
 # ---------------------------------------------------------------------------

tests/test_musicbrainz.py

@@ -4,7 +4,6 @@ import importlib.util
 import json
 import sys
 import time
-from io import BytesIO
 from unittest.mock import MagicMock, patch
 
 # -- Load module directly ----------------------------------------------------
@@ -305,6 +304,7 @@ class TestMbFindSimilarRecordings:
                 "Tool", ["rock", "metal", "prog"],
             )
         call_args = mock_req.call_args
-        query = call_args[1]["query"] if "query" in (call_args[1] or {}) else call_args[0][1].get("query", "")
+        args = call_args[1] or {}
+        query = args.get("query") or call_args[0][1].get("query", "")
         # Verify the query contains both tag references
         assert "rock" in query or "metal" in query