yellowjacket/.planning/PROJECT.md

YellowJacket

What This Is

YellowJacket is a cross-platform desktop music player built with Go (Wails v2) and TypeScript (Lit Web Components). It plays local music files (MP3, FLAC, OGG, WAV), manages a music library via SQLite, and provides queue management, playlists, cover art, and MPRIS media controls on Linux. The v1.0 Consolidation milestone strengthened the foundation — all known concurrency races are fixed, error handling is honest, SQL patterns are consolidated, performance bottlenecks are resolved, the frontend follows a consistent design language, and 84 unit tests provide a safety net for future work.

Core Value

The music player works reliably and feels solid. Every interaction is correct, responsive, and trustworthy — the foundation that all future features will build on.

Requirements

Validated

• ✓ Audio playback (play, pause, stop, seek, volume) for MP3, FLAC, OGG, WAV — existing
• ✓ Library scanning with concurrent metadata extraction pipeline — existing
• ✓ Queue management with shuffle, repeat modes, and auto-advance — existing
• ✓ Queue and player state persistence across app restarts — existing
• ✓ Full-text search across tracks, artists, albums, file paths (FTS5) — existing
• ✓ Playlist CRUD with M3U8 import/export and phantom track resolution — existing
• ✓ Favorites system with dedicated playlist — existing
• ✓ Cover art extraction, thumbnail generation (sm/md/lg), and serving — existing
• ✓ MPRIS2 media controls on Linux — existing
• ✓ Theme configuration (accent color, background shade) — existing
• ✓ Track list column configuration — existing
• ✓ Multiple library directory support — existing
• ✓ Adaptive scan concurrency based on disk type (SSD vs HDD) — existing
• ✓ Two-phase queue initialization for instant UI response — existing
• ✓ Event-driven frontend/backend synchronization — existing
• ✓ TOML-based user configuration with live reload — existing
• ✓ Browse by albums, artists, genres with detail views — existing
• ✓ Virtual scrolling for large lists — existing
• ✓ Concurrency race-free SetContext across Queue, Library, Playlist, Player — v1.0
• ✓ Error handling: startupErr moved to struct, config 0o644, MPRIS errors logged, scan warnings separated — v1.0
• ✓ FTS5 JOIN pattern consolidated into track_metadata VIEW — v1.0
• ✓ Event name codegen (Go→TypeScript) with pre-commit hook enforcement — v1.0
• ✓ Queue batch lookups use sqlc.slice(), all hand-crafted SQL documented with SAFETY comments — v1.0
• ✓ Incremental queue persistence (O(1) add/remove) and SetQueue Phase 2 dedup — v1.0
• ✓ Library store deferred loading for instant app shell — v1.0
• ✓ SQLite performance PRAGMAs (synchronous, cache_size, mmap_size) — v1.0
• ✓ Frontend repeat() with stable keys, queueMicrotask coalescing, classMap directives — v1.0
• ✓ Design token system and visual consistency across all 15 components — v1.0
• ✓ 84 unit tests: queue (29), config/player (10+), FTS5 search (15), library scan (13), entity cache (13+) — v1.0

Active

(No active requirements — next milestone not yet scoped. Run /gsd-new-milestone to define.)

Out of Scope

• Tag writing (track metadata editing) — feature work, not consolidation
• Scan cancellation — feature work, deferred to future milestone
• Cross-platform media controls (macOS/Windows) — feature work
• Database health checking / reconnection — low priority, desktop app context
• File decomposition for its own sake — only extract when it enables reuse or fixes problems
• ORM or query builder — would fight existing sqlc architecture
• Connection pooling for SQLite — meaningless with SetMaxOpenConns(1)

Context

Current state (v1.0 shipped 2026-03-05):

• Go 1.25, Wails v2.10.2, Lit 3.2.1, SQLite via modernc.org/sqlite
• ~22,450 Go LOC + ~28,600 TypeScript LOC + ~5,200 Go test LOC
• ~15 backend packages, ~20 frontend components
• Strict linting (golangci-lint v2) and TypeScript strict mode
• 84 unit tests covering queue, config, player, database, library packages
• All concurrency races fixed, app runs clean under -race
• SQL consolidated: track_metadata VIEW, sqlc.slice(), SAFETY comments
• Frontend: design token system, virtual scrolling with stable keys, debounced store notifications
• Player tests still require hardware (skipped in CI)
• No frontend unit tests (deferred to v2)

Codebase analysis available in:

• .planning/codebase/ARCHITECTURE.md
• .planning/codebase/CONCERNS.md
• .planning/codebase/CONVENTIONS.md
• .planning/codebase/INTEGRATIONS.md
• .planning/codebase/STACK.md

Constraints

• Tech stack: Go + Wails v2 + Lit + SQLite — no changes to the fundamental stack
• Build tags: All Go commands require -tags webkit2_41 on Linux
• Single writer: SQLite with WAL mode and SetMaxOpenConns(1) — design around this
• Backward compatibility: Existing user config and database must continue working after changes
• Linting: All code must pass make lint (golangci-lint v2 with strict rules)
• No CGo: Pure-Go SQLite driver (modernc.org/sqlite) — cannot switch to CGo-based drivers

Key Decisions

Decision	Rationale	Outcome
Consolidation before features	Technical debt compounds — fixing it now is cheaper than fixing it later under more code	✓ Good — solid foundation established
Tests support refactoring, not standalone goal	Testing is a means to safe refactoring, not a coverage target	✓ Good — 84 tests enabled safe SQL and perf refactoring
No cosmetic file splitting	Large files are only a problem if they cause real issues; extract only for reuse or correctness	✓ Good — avoided unnecessary churn
All improvement areas equal priority	Correctness, performance, code quality, UX, and testing are interdependent	✓ Good — balanced approach worked well
Fix races → tests → refactoring order	Can't run -race-clean tests with active data races; can't safely refactor without tests	✓ Good — each phase built on the last
SQLite VIEW for JOIN dedup	track_metadata VIEW consolidates 5-table JOIN; migration keeps inline for upgrade	✓ Good — 60 lines eliminated, tests unchanged
AST-based event codegen	Deterministic declaration-order output, no regex fragility	✓ Good — found LibraryConfigChanged gap automatically
queueMicrotask over setTimeout	Synchronous microtask batching is more predictable than macrotask scheduling	✓ Good — coalesces 8+ notifications per scan
Design tokens via :host scope	Component-level token scope matches Lit's shadow DOM encapsulation	✓ Good — consistent visual language achieved

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Last updated: 2026-03-05 after v1.0 milestone