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Technology Stack Additions: v1.1 Features & Extensibility

Project: YellowJacket v1.1 Researched: 2026-03-06 Overall confidence: HIGH (tag writing, beep audio) / MEDIUM (MusicBrainz API, plugin architecture)

This document covers only new libraries and patterns needed for v1.1 features. The existing stack (Go 1.25, Wails v2.10.2, Lit 3.2.1, beep v2.1.1, modernc.org/sqlite, dhowden/tag, BurntSushi/toml, etc.) is validated and unchanged.

Recommended Stack Additions

1. Tag Writing — MP3 (ID3v2)

Technology Version Import Path Purpose Why
n10v/id3v2 v2.1.4 github.com/n10v/id3v2/v2 Read/write ID3v2.3 and v2.4 tags for MP3 files The only maintained pure-Go library with full ID3v2 write support. 359 stars, 43 releases, active (last release Feb 2023, stable). dhowden/tag (existing) is read-only — it cannot write tags back.

Confidence: HIGH — verified via GitHub repo, pkg.go.dev. The v2 module path uses the /v2 subdirectory pattern (github.com/n10v/id3v2/v2).

API surface used:

tag, err := id3v2.Open("file.mp3", id3v2.Options{Parse: true})
defer tag.Close()
tag.SetArtist("New Artist")
tag.SetTitle("New Title")
tag.SetAlbum("New Album")
tag.SetGenre("Electronic")
tag.SetYear("2024")
// Write back to file
err = tag.Save()

Integration notes:

  • Operates on the file directly (open, modify, save). Does not need the existing beep pipeline.
  • Must close the file before beep can play it — coordinate with player via a "stop playback → write tags → reload" flow.
  • Keep dhowden/tag for reading (scan pipeline uses it). Use n10v/id3v2 only for writing MP3 files.
  • Thread safety: id3v2 file operations are not concurrent-safe. The tag editor backend service should serialize writes.

2. Tag Writing — FLAC (Vorbis Comments)

Technology Version Import Path Purpose Why
go-flac/go-flac v2.x github.com/go-flac/go-flac/v2 Parse and reassemble FLAC file metadata blocks Low-level FLAC metadata manipulation. 44 stars. Provides ParseFile, modify Meta slice, Save.
go-flac/flacvorbis v2.x github.com/go-flac/flacvorbis/v2 Read/write Vorbis comment metadata blocks within FLAC files Companion to go-flac. Provides ParseFromMetaDataBlock, Add, Set for FLAC vorbis comments. 11 stars, but the only option in the Go ecosystem.

Confidence: MEDIUM — both libraries are small and niche but are the standard Go solution for FLAC tag writing. v2 modules exist in /v2 subdirectories.

API surface used:

f, err := flac.ParseFile("file.flac")
// Find existing vorbis comment block
var cmt *flacvorbis.MetadataBlockVorbisComment
var cmtIdx int
for idx, meta := range f.Meta {
    if meta.Type == flac.VorbisComment {
        cmt, _ = flacvorbis.ParseFromMetaDataBlock(*meta)
        cmtIdx = idx
    }
}
if cmt == nil {
    cmt = flacvorbis.New()
}
cmt.Add(flacvorbis.FIELD_TITLE, []byte("New Title"))
cmt.Add(flacvorbis.FIELD_ARTIST, []byte("New Artist"))
cmtMeta := cmt.Marshal()
if cmtIdx > 0 {
    f.Meta[cmtIdx] = &cmtMeta
} else {
    f.Meta = append(f.Meta, &cmtMeta)
}
f.Save("file.flac")

Integration notes:

  • go-flac reads the entire FLAC file into memory (metadata + audio frames). For large FLAC files (100MB+), this uses significant memory. The write operation is atomic (writes full file).
  • Same coordination needed: stop playback → write → reload.

3. Tag Writing — OGG Vorbis and WAV

Format Approach Why
OGG Vorbis Defer to v1.2 or use external tool No mature pure-Go library exists for writing OGG Vorbis comments. The OGG container format makes in-place tag editing complex. Consider shelling out to vorbiscomment CLI tool if needed, or defer.
WAV Not needed for v1.1 WAV files rarely have meaningful tags (no standard tagging convention). INFO chunks exist but are rarely used in music libraries.

Confidence: HIGH — exhaustive search found no viable pure-Go OGG Vorbis tag writer.

Recommendation: Implement tag editing for MP3 and FLAC first (covers ~95% of music libraries). Show "read-only" indicator for OGG/WAV files in the tag editor UI. Add OGG support later if demand exists.

4. MusicBrainz API Client

Technology Version Import Path Purpose Why
Direct HTTP + encoding/json stdlib — Query MusicBrainz REST API (JSON format) Use Go's standard library rather than a third-party client. See rationale below.

Confidence: HIGH — MusicBrainz API is well-documented REST/JSON. The API is simple enough that a custom thin client is better than available libraries.

Why NOT use michiwend/gomusicbrainz:

  • Last meaningful commit was years ago, no Go modules support initially (added by community), uses XML parsing. 64 stars but effectively unmaintained.
  • The library only supports search and lookup — no browse requests.
  • MusicBrainz API supports JSON natively (fmt=json or Accept: application/json), making XML parsing unnecessary.

Why NOT use go.uploadedlobster.com/musicbrainzws2:

  • Hosted on SourceHut, harder to verify maintenance status.
  • Low adoption (not visible on GitHub).

Custom client approach (recommended):

// backend/musicbrainz/client.go
package musicbrainz

type Client struct {
    httpClient *http.Client
    baseURL    string
    userAgent  string
    rateLimiter *time.Ticker  // MusicBrainz requires max 1 req/sec
}

func NewClient(appName, appVersion, contactURL string) *Client {
    return &Client{
        httpClient: &http.Client{Timeout: 10 * time.Second},
        baseURL:    "https://musicbrainz.org/ws/2",
        userAgent:  fmt.Sprintf("%s/%s (%s)", appName, appVersion, contactURL),
        rateLimiter: time.NewTicker(time.Second), // 1 request per second
    }
}

MusicBrainz API integration points:

  • Rate limiting: MANDATORY — max 1 request per second. Use time.Ticker with channel-based throttling.
  • User-Agent: MANDATORY — must include app name, version, and contact URL. MusicBrainz blocks requests without meaningful user-agents.
  • Endpoints needed for read-only browser:
    • GET /ws/2/artist/<MBID>?inc=release-groups&fmt=json — Artist lookup with discography
    • GET /ws/2/release-group/<MBID>?inc=releases&fmt=json — Album editions
    • GET /ws/2/release/<MBID>?inc=recordings+media&fmt=json — Track listings
    • GET /ws/2/artist?query=<QUERY>&fmt=json — Artist search
    • GET /ws/2/release-group?query=<QUERY>&fmt=json — Album search
  • Response caching: Cache API responses in SQLite with TTL (e.g., 7 days). MusicBrainz data is slow-changing. Reduces API calls and improves UI responsiveness.
  • No authentication needed: Read-only lookups and searches are unauthenticated.

5. Gapless Playback + Crossfade

Technology Version Purpose Why
beep.Mixer v2.1.1 (existing) Mix two streams for crossfade Already in the dependency tree. beep.Mixer dynamically adds/removes streamers and mixes them. KeepAlive(true) keeps it playing silence when no streamers are active.
beep.Seq v2.1.1 (existing) Chain streams for gapless Already used in startPaused(). beep.Seq(s1, s2) plays s1 then s2 without gap.
effects.Volume v2.1.1 (existing) Per-stream volume for fade curves Already used for main volume. Create separate Volume wrappers for fade-in/fade-out.

Confidence: HIGH — all primitives already exist in beep v2.1.1.

No new dependencies needed. Gapless and crossfade are implemented by changing how the streamer chain is composed, not by adding new libraries.

Gapless architecture:

// Instead of: speaker.Play(beep.Seq(currentStream, beep.Callback(onFinished)))
// Use: pre-decode next track and Seq them together.

// When current track nears end (e.g., 2 seconds remaining):
nextStreamer, nextFormat := decodeNextTrack()
resampled := beep.Resample(4, nextFormat.SampleRate, speakerSampleRate, nextStreamer)
// The beep.Seq already playing will seamlessly transition to the next stream.

Crossfade architecture:

// Use a Mixer as the root streamer instead of a single chain.
type CrossfadeMixer struct {
    mixer     beep.Mixer
    fadeInMs  int
    fadeOutMs int
}

// When transitioning:
// 1. Create fade-out volume wrapper on current stream
// 2. Create fade-in volume wrapper on next stream  
// 3. Add both to mixer
// 4. Use beep.StreamerFunc to drive the volume ramps over time

Key integration changes:

  • The Player struct currently uses speaker.Play(beep.Seq(...)) for single-stream playback. For gapless/crossfade, switch to a persistent beep.Mixer registered with the speaker once at init.
  • Add/remove streams from the mixer rather than calling speaker.Play() per track.
  • The beep.Callback for end-of-track still works but fires per-stream in the mixer, not per-speaker-play.
  • Pre-decoding the next track requires knowing what the next track IS. This means the player needs awareness of the queue (currently it only knows about the current file). Wire this via a "next track provider" interface.

6. Plugin System Architecture

Technology Version Purpose Why
Go plugin package stdlib ❌ NOT recommended Linux-only, same Go version required, fragile.
hashicorp/go-plugin — ❌ NOT recommended gRPC-based, heavy for a desktop app, designed for server-side tools.
Custom interface + registration — ✅ Recommended Define Go interfaces for backend hooks. Plugins implement interfaces and register at init.

Confidence: MEDIUM — plugin architecture is inherently design-specific. No off-the-shelf solution fits perfectly.

Recommended approach: Compiled-in plugin system with runtime-loaded UI

Backend plugins (Go):

// backend/plugin/api.go
package plugin

// Plugin is the interface all backend plugins must implement.
type Plugin interface {
    ID() string
    Name() string
    Version() string
    Init(ctx PluginContext) error
    Shutdown() error
}

// PluginContext provides access to app services.
type PluginContext struct {
    DB        *database.DB
    Events    EventEmitter
    Config    ConfigAccess
    Logger    *slog.Logger
}

// Hook interfaces — plugins implement the ones they care about.
type OnTrackChangeHook interface {
    OnTrackChange(track TrackInfo) error
}
type OnScanCompleteHook interface {
    OnScanComplete(metrics ScanMetrics) error
}

For v1.1, backend plugins are compiled into the binary (via Go build tags or registration in main.go). True dynamic loading can come later via process-based plugins (subprocess + JSON-RPC).

Frontend plugins (TypeScript/Lit):

  • Plugins provide Lit web components that register themselves via customElements.define().
  • The layout system (see below) allows placing plugin components in UI sections.
  • Plugin JS bundles are loaded at runtime from a plugins directory via dynamic import().

No new Go dependencies needed for the initial plugin system. The complexity is in API design, not in libraries.

7. Layout Customization System

Technology Purpose Why
Existing: Lit + config.toml Section-based layout config The existing TOML config system and Lit component architecture are sufficient. No new dependencies needed.

Confidence: HIGH — this is a UI architecture problem, not a library problem.

Architecture:

# config.toml additions:
[Layout]
  [Layout.Sidebar]
  components = ["navigation", "now-playing-art"]
  width = 250
  
  [Layout.MainPanel]
  components = ["track-list"]
  
  [Layout.BottomBar]
  components = ["audio-player", "queue-mini"]

Frontend implementation:

// A layout-section component that renders configured child components
@customElement('layout-section')
class LayoutSection extends LitElement {
    @property() section: string = '';
    @property({ type: Array }) components: string[] = [];
    
    render() {
        return html`${this.components.map(name => {
            const tag = document.createElement(name);
            return tag;
        })}`;
    }
}

Component registry pattern:

// Each component declares its constraints
interface LayoutComponent {
    tagName: string;
    displayName: string;
    minWidth?: number;
    minHeight?: number;
    allowedSections: string[];
}

const registry = new Map<string, LayoutComponent>();

No new npm dependencies needed. Lit's customElements.define() provides the dynamic component loading mechanism. The config system already handles TOML persistence and live reload.

8. Smart Playlists

Technology Purpose Why
Existing: SQLite + sqlc Dynamic query builder for filter rules Smart playlists are SQL WHERE clauses stored as structured data. No new dependencies needed.

Confidence: HIGH — smart playlists are a database query problem.

Architecture:

// Smart playlist rule stored in SQLite
type SmartPlaylistRule struct {
    Field    string // "genre", "year", "artist", "play_count", "date_added"
    Operator string // "equals", "contains", "greater_than", "less_than", "between"
    Value    string // The comparison value(s)
}

type SmartPlaylist struct {
    ID        int64
    Name      string
    Rules     []SmartPlaylistRule // Stored as JSON in SQLite
    MatchAll  bool                // AND vs OR for combining rules
    SortBy    string
    SortOrder string
    Limit     int                 // 0 = unlimited
}

Query generation (not sqlc — dynamic WHERE clauses):

// Hand-crafted SQL builder for smart playlists.
// Cannot use sqlc because the WHERE clause is dynamic.
func (sp *SmartPlaylist) BuildQuery() (string, []any) {
    // Build parameterized query from rules.
    // Always use parameterized queries — never interpolate values.
}

Schema addition: New smart_playlists table with JSON rules column. New migration in the existing PRAGMA user_version system.

No new dependencies needed. The existing encoding/json handles rule serialization.

9. Customizable Keyboard Shortcuts

Technology Purpose Why
Existing: Wails runtime + config.toml + Lit Frontend keyboard event handling with configurable bindings Keyboard shortcuts are a frontend concern in WebView. No new dependencies.

Confidence: HIGH — standard web keyboard event handling.

Architecture:

# config.toml additions:
[KeyboardShortcuts]
play_pause = "Space"
next_track = "MediaTrackNext"
prev_track = "MediaTrackPrevious"
volume_up = "ArrowUp"
volume_down = "ArrowDown"
seek_forward = "ArrowRight"
seek_backward = "ArrowLeft"
toggle_queue = "Q"
search = "Ctrl+F"

Frontend implementation:

// Global keyboard handler — listens on document, maps keys to actions
class KeyboardShortcutManager {
    private bindings: Map<string, string>; // key combo → action name
    private actions: Map<string, () => void>; // action name → handler
    
    handleKeyDown(e: KeyboardEvent) {
        const combo = this.normalizeCombo(e);
        const action = this.bindings.get(combo);
        if (action) {
            e.preventDefault();
            this.actions.get(action)?.();
        }
    }
}

No new dependencies needed. The Web platform's KeyboardEvent API provides everything. Store bindings in TOML config, load on startup, emit config change events on update.

10. Scan Cancellation

Technology Purpose Why
Existing: context.WithCancel Cancel in-progress library scan Go's context cancellation is the standard pattern. The scan pipeline already uses errgroup which respects context cancellation.

Confidence: HIGH — standard Go pattern.

Implementation:

// In Library struct:
type Library struct {
    scanCancel context.CancelFunc  // nil when no scan is running
    // ...
}

func (l *Library) Scan() {
    ctx, cancel := context.WithCancel(l.ctx)
    l.scanCancel = cancel
    defer func() { l.scanCancel = nil }()
    
    // Pass ctx to errgroup and all scan phases
    g, gctx := errgroup.WithContext(ctx)
    // Workers check gctx.Done() and exit early
}

func (l *Library) CancelScan() {
    if l.scanCancel != nil {
        l.scanCancel()
    }
}

No new dependencies needed. The existing golang.org/x/sync/errgroup already propagates context cancellation to worker goroutines.

Alternatives Considered

Category Recommended Alternative Why Not
MP3 tag writing n10v/id3v2 v2 bogem/id3v2 (old path) Same library — n10v/id3v2 is the current canonical path after maintainer rename
FLAC tag writing go-flac/go-flac + flacvorbis mewkiz/flac mewkiz/flac is a decoder/encoder, not a metadata editor. Would require full re-encode to change tags.
MusicBrainz client Custom HTTP client michiwend/gomusicbrainz Unmaintained, XML-only, missing browse API, no Go modules initially
MusicBrainz client Custom HTTP client go-musicbrainzws2 (SourceHut) Low adoption, hard to verify maintenance, adds unfamiliar dependency
Gapless/crossfade beep.Mixer (existing) External audio library beep already provides all needed primitives (Mixer, Seq, Volume, Resample)
Plugin system Interface-based registration hashicorp/go-plugin gRPC overhead is inappropriate for a desktop app; designed for distributed systems
Plugin system Interface-based registration Go plugin package Linux-only, same Go version required, CGo required for loading, extremely fragile
Plugin system Interface-based registration Wasm runtime (wazero) Massive complexity for v1.1; good future option for sandboxed plugins
Smart playlists Dynamic SQL builder SQLite views Views can't be parameterized at query time; rules need runtime evaluation
Keyboard shortcuts Web KeyboardEvent API Frontend hotkey library No library needed for the scope of shortcuts in a music player

What NOT to Add

These are things the existing stack already handles. Do NOT add duplicate libraries:

Capability Already Handled By DON'T Add
Tag reading github.com/dhowden/tag Any other tag reading library — keep dhowden/tag for the scan pipeline
Audio decoding gopxl/beep/v2 (mp3, flac, vorbis, wav) Any other audio decoder
Config persistence BurntSushi/toml YAML, JSON, or any other config library
Database modernc.org/sqlite Any other database or ORM
HTTP client Go stdlib net/http Any HTTP client library for MusicBrainz
JSON parsing Go stdlib encoding/json Any JSON library for MusicBrainz responses
Concurrency Go stdlib context, sync, golang.org/x/sync Any additional concurrency primitives
Frontend reactivity Lit 3.2.1 + @lit-labs/signals Any state management library
Virtual scrolling @lit-labs/virtualizer Any other virtual scrolling solution

Installation

# New Go dependencies (tag writing + FLAC metadata):
go get github.com/n10v/id3v2/v2@v2.1.4
go get github.com/go-flac/go-flac/v2
go get github.com/go-flac/flacvorbis/v2

# No new frontend (npm) dependencies needed for v1.1.
# All features use existing Lit + Web platform APIs.

Total new dependencies: 3 Go packages, 0 npm packages.

This is intentionally minimal. The v1.1 features are primarily architecture and design challenges, not library selection challenges. The existing stack is comprehensive enough that most features require new code, not new dependencies.

Integration Points with Existing Stack

Tag Editing → Player Coordination

The player holds an open file handle (p.currentFile) during playback. Tag writing libraries also need exclusive file access. The workflow must be:

  1. Player.Pause() or Player.Stop() — release the file
  2. Write tags via id3v2/go-flac
  3. Rescan the file's metadata into the database
  4. Player.LoadFile() with the same path — resume

MusicBrainz → Database Caching

MusicBrainz API responses should be cached in SQLite (new tables: mb_cache_artists, mb_cache_releases, etc.) with a TTL column. This reuses the existing database infrastructure and avoids redundant API calls. The 1-request-per-second rate limit makes caching essential for a responsive UI.

Gapless/Crossfade → Speaker Architecture

Current: speaker.Play() called per track, creates new beep.Seq each time. New: Register a persistent beep.Mixer with the speaker once at init. Add/remove per-track streamers to the mixer. This is the biggest architectural change — it affects Player, Queue auto-advance, and the playback-finished callback chain.

Smart Playlists → Existing Query Infrastructure

Smart playlists generate SQL queries against the existing track_metadata VIEW and related tables. They use the same *database.DB connection with the same SetMaxOpenConns(1) constraint. Rules are stored as JSON in a new smart_playlists table (schema migration via existing PRAGMA user_version system).

Layout Customization → Config + Frontend

New [Layout] section in config.toml, loaded via existing BurntSushi/toml config system. Layout changes emit config change events via existing Wails event bus. Frontend components register themselves in a component registry and the layout section components render them dynamically.

Plugin System → Everything

Backend plugins get a PluginContext with access to DB, events, config, logger. Frontend plugins load as JS modules via import() and register Lit web components. Both hook into the existing architecture rather than requiring new infrastructure.

Sources

Stack research for: YellowJacket v1.1 Features & Extensibility Researched: 2026-03-06

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