yoloyolo/.planning/RETROSPECTIVE.md

# Retrospective

## Milestone: v1.0 — MVP

**Shipped:** 2026-03-26
**Phases:** 4 | **Plans:** 11 | **Timeline:** 3 days (2026-03-24 -> 2026-03-26)
**LOC:** 3,254 Go | **Files:** 84 modified

### What Was Built
- Config-driven packet classifier with 12 protocol rules and 4 hash-bucketed unknown classes
- Live packet capture via pure Go go-pcap with privilege detection and non-blocking channel pipeline
- Additive synthesis engine: per-class oscillators, EMA amplitude smoothing, constant-power stereo mixing
- MP3 encoding via embedded LAME, zero-packet guard
- End-to-end pipeline with clean Ctrl+C shutdown
- BPF filter and offline pcap file sonification with timestamp-based windowing

### What Worked
- Risk-ordered phases: hardest foundation first (capture), then synthesis in isolation, then integration — no phase blocked on another's bugs
- TDD approach in executor agents caught signature mismatches early
- Pure Go capture layer (go-pcap) avoided libpcap dependency headaches
- Hand-rolled synthesis kept dependencies minimal and code understandable
- Wave-based parallel execution for independent plans

### What Was Inefficient
- Some SUMMARY.md files had empty one-liner fields, causing noisy milestone extraction
- Phase 4 research could have been lighter — BPF/pcap APIs were straightforward

### Patterns Established
- Ordered []Rule slice for classifier (first-match-wins, extensible)
- io.Writer injection for testable stderr output
- Buffered channels between pipeline stages (512-1024) to absorb bursts
- Package-level globals for Cobra flag binding
- Timestamp-based windowing for non-live sources

### Key Lessons
- Embedding C source (go-lame) is a good tradeoff: CGo at build time only, no runtime dependency
- go-audio/wav was unnecessary — writing PCM bytes directly to LameWriter is simpler
- Hash-bucketed unknowns (4 classes) are sufficient for audio distinction without k-means complexity

## Milestone: v1.1 — Custom Sound Mappings

**Shipped:** 2026-03-26
**Phases:** 3 | **Plans:** 6 | **Timeline:** 1 day (2026-03-26)
**LOC:** ~4,675 Go (+1,421 from v1.0) | **Packages:** 7

### What Was Built
- Four waveform types (sine, square, sawtooth, triangle) with bandlimited additive synthesis
- TOML config system: auto-discovery, partial overrides, unknown-key validation, `--config` flag
- User-defined `[[rules]]` classification rules with first-match-wins prepend semantics
- Auto-frequency assignment (FNV-32a hash) for custom class names
- `--print-config` flag with commented TOML output and source annotations
- LoadResult struct pattern for clean config-to-pipeline data flow

### What Worked
- Incremental config extension: Phase 6 built the config package, Phase 7 extended it cleanly
- TDD plans (type: tdd in frontmatter) produced higher-quality code with fewer regressions
- FNV-32a frequency assignment was verified experimentally during research before planning
- Worktree isolation for parallel executor agents prevented merge conflicts
- Reusing existing patterns (Rule struct, NewClassifier injection, Cobra flag-on-root) kept code consistent

### What Was Inefficient
- SUMMARY.md one-liner extraction continued to be noisy — summary-extract needs improvement
- Phase 5 could potentially have been merged with Phase 6 (waveform + config together)

### Patterns Established
- LoadResult struct for multi-value config returns (extensible without breaking callers)
- Pointer fields (`*float64`, `*string`) for partial TOML override semantics
- FNV-32a hash for deterministic resource assignment from string keys
- Flag-on-root pattern for early-exit operations (--list-interfaces, --print-config)
- `addAutoFreqEntries()` pattern: fill gaps in config before merge

### Key Lessons
- BurntSushi/toml Undecoded() works with array-of-tables (verified experimentally)
- Manual string building beats TOML encoder when you need inline comments/annotations
- Config extension is smooth when the original Load() was designed with clean boundaries

## Milestone: v1.2 — Extended Protocol Coverage

**Shipped:** 2026-03-27
**Phases:** 4 | **Plans:** 7 | **Timeline:** 1 day (2026-03-27)
**LOC:** ~6,000 Go (+1,325 from v1.1) | **Files:** 19 modified

### What Was Built
- Removed stale constants and future-proofed test bounds (Nyquist-based validation)
- Rebalanced all ClassFreqConfigs to major-second ladder in family frequency bands (65-3250 Hz) with Group field
- 21 new TrafficClass constants and 30 port-matching rules across 7 protocol families
- 28 new classification subtests covering all new port/protocol/transport combinations
- 21 ClassFreqConfigs entries with family-coherent sound design
- Group-ordered --print-config with section headers and [groups] TOML reassignment

### What Worked
- Cleanup-first approach (Phase 8) prevented cascading test failures throughout the milestone
- Design-before-code (Phase 9 frequency table locked before any protocol code) avoided retroactive rebalancing
- Strict phase ordering (constants -> rules -> config) kept three-location atomicity tests green
- Musical interval spacing (major second ratio 1.122) produced perceptually distinct yet family-coherent sounds
- Oscillator normalization bug caught and fixed during frequency rebalancing (math.Abs for alternating-sign harmonics)

### What Was Inefficient
- Phase 9 plan 09-01 ROADMAP checkbox wasn't updated after execution — milestone readiness check showed incomplete
- REQUIREMENTS.md traceability wasn't updated for Phase 9 completions (FREQ-01 through GRP-04 still showed Pending)
- STATE.md accumulated merge conflict markers from earlier worktree operations, persisted unnoticed

### Patterns Established
- Group field as string (not enum) on FreqConfig — extensible without code changes
- Major-second ladder pattern for family-band frequency allocation
- groupOrder canonical slice for deterministic section ordering in config output
- rawConfig Groups map for TOML [groups] table parsing

### Key Lessons
- Musical interval ratios are better than fixed Hz steps for frequency allocation — prevents critical band masking
- Group-based config output requires building from effective (post-reassignment) groups, not defaults
- Cleanup phases are high-ROI when they prevent test failures in every subsequent phase

## Cross-Milestone Trends

| Metric | v1.0 | v1.1 | v1.2 |
|--------|------|------|------|
| Phases | 4 | 3 | 4 |
| Plans | 11 | 6 | 7 |
| Days | 3 | 1 | 1 |
| LOC | 3,254 | 4,675 | ~6,000 |
| Avg plan duration | ~8 min | ~5 min | ~4 min |