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+---
+phase: 9
+slug: frequency-design-and-group-architecture
+status: draft
+nyquist_compliant: false
+wave_0_complete: false
+created: 2026-03-27
+---
+
+# Phase 9 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | go test |
+| **Config file** | none — standard Go test runner |
+| **Quick run command** | `go test ./synth/... ./config/...` |
+| **Full suite command** | `go test ./...` |
+| **Estimated runtime** | ~5 seconds |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `go test ./synth/... ./config/...`
+- **After every plan wave:** Run `go test ./...`
+- **Before `/gsd:verify-work`:** Full suite must be green
+- **Max feedback latency:** 5 seconds
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|-----------|-------------------|-------------|--------|
+| 09-01-01 | 01 | 1 | FREQ-01 | unit | `go test ./synth/... -run TestFreqConfig` | ✅ | ⬜ pending |
+| 09-01-02 | 01 | 1 | FREQ-02 | unit | `go test ./synth/... -run TestInterval` | ❌ W0 | ⬜ pending |
+| 09-01-03 | 01 | 1 | GRP-01 | unit | `go test ./synth/... -run TestGroupField` | ❌ W0 | ⬜ pending |
+| 09-01-04 | 01 | 1 | FREQ-03 | unit | `go test ./config/... -run TestAutoAssign` | ✅ | ⬜ pending |
+| 09-01-05 | 01 | 1 | FREQ-04 | unit | `go test ./synth/... -run TestFrequencies` | ✅ | ⬜ pending |
+| 09-01-06 | 01 | 1 | GRP-04 | unit | `go test ./synth/... -run TestGroupPopulated` | ❌ W0 | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+- [ ] `synth/bank_test.go` — TestIntervalConstraint: verify all within-family pairs have ratio >= 1.122
+- [ ] `synth/bank_test.go` — TestGroupFieldPopulated: verify all ClassFreqConfigs entries have non-empty Group
+- [ ] Update `TestHarmonicsNonEmpty` to accept >= 1 harmonic (for WaveformSine entries)
+
+*Existing infrastructure covers most phase requirements. Wave 0 adds targeted assertions for new constraints.*
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Frequency table documented in planning doc | FREQ-01 | Documentation artifact | Inspect 09-RESEARCH.md or code comment for complete Hz/waveform/group table |
+
+---
+
+## Validation Sign-Off
+
+- [ ] All tasks have `<automated>` verify or Wave 0 dependencies
+- [ ] Sampling continuity: no 3 consecutive tasks without automated verify
+- [ ] Wave 0 covers all MISSING references
+- [ ] No watch-mode flags
+- [ ] Feedback latency < 5s
+- [ ] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending