diff --git a/.planning/phases/03-collapsible-dashboard-sections/03-VALIDATION.md b/.planning/phases/03-collapsible-dashboard-sections/03-VALIDATION.md
new file mode 100644
index 0000000..e0d3f64
--- /dev/null
+++ b/.planning/phases/03-collapsible-dashboard-sections/03-VALIDATION.md
@@ -0,0 +1,79 @@
+---
+phase: 3
+slug: collapsible-dashboard-sections
+status: draft
+nyquist_compliant: true
+wave_0_complete: false
+created: 2026-03-17
+---
+
+# Phase 3 — Validation Strategy
+
+> Per-phase validation contract for feedback sampling during execution.
+
+---
+
+## Test Infrastructure
+
+| Property | Value |
+|----------|-------|
+| **Framework** | None installed — no test framework in project |
+| **Config file** | None |
+| **Quick run command** | `bun run lint` |
+| **Full suite command** | `bun run build` |
+| **Estimated runtime** | ~10 seconds |
+
+---
+
+## Sampling Rate
+
+- **After every task commit:** Run `bun run lint`
+- **After every plan wave:** Run `bun run build`
+- **Before `/gsd:verify-work`:** Full build must succeed + manual browser testing
+- **Max feedback latency:** 10 seconds
+
+---
+
+## Per-Task Verification Map
+
+| Task ID | Plan | Wave | Requirement | Test Type | Automated Command | File Exists | Status |
+|---------|------|------|-------------|-----------|-------------------|-------------|--------|
+| 03-01-01 | 01 | 1 | UI-COLLAPSE-01 | lint+build | `bun run lint && bun run build` | N/A | ⬜ pending |
+| 03-01-02 | 01 | 1 | UI-COLLAPSE-01 | lint+build | `bun run lint && bun run build` | N/A | ⬜ pending |
+| 03-02-01 | 02 | 1 | UI-DASH-01 | lint+build | `bun run lint && bun run build` | N/A | ⬜ pending |
+| 03-02-02 | 02 | 1 | UI-DASH-01 | lint+build | `bun run lint && bun run build` | N/A | ⬜ pending |
+
+*Status: ⬜ pending · ✅ green · ❌ red · ⚠️ flaky*
+
+---
+
+## Wave 0 Requirements
+
+Existing infrastructure covers all phase requirements. No test framework to install.
+
+---
+
+## Manual-Only Verifications
+
+| Behavior | Requirement | Why Manual | Test Instructions |
+|----------|-------------|------------|-------------------|
+| Collapsible sections render between charts and QuickAdd | UI-DASH-01 | No test framework; visual layout | Open dashboard with a budget — verify sections appear below chart grid, above QuickAdd |
+| Over-budget sections auto-expand on load | UI-DASH-01 | No test framework; state logic | Create budget where expenses exceed budget — verify those sections start expanded |
+| Carryover subtitle appears on balance card when non-zero | UI-DASH-01 | No test framework; conditional render | Set carryover_amount on a budget — verify "Includes $X carryover" subtitle appears |
+| Section expands/collapses with smooth animation | UI-COLLAPSE-01 | No test framework; CSS animation | Click section headers — verify smooth height transition |
+| No ResizeObserver loop errors on rapid toggle | UI-COLLAPSE-01 | Browser console check | Rapidly toggle sections 10+ times — check browser console for ResizeObserver errors |
+| Empty category groups are hidden | UI-COLLAPSE-01 | No test framework; conditional render | Budget with no debt items — verify debt section is absent |
+| State resets on month navigation | UI-COLLAPSE-01 | No test framework; state interaction | Expand a section, navigate to different month — verify smart defaults recalculate |
+
+---
+
+## Validation Sign-Off
+
+- [x] All tasks have automated verify (lint+build) or manual-only documented
+- [x] Sampling continuity: lint runs after every task commit
+- [x] Wave 0 covers all MISSING references (N/A — no test framework)
+- [x] No watch-mode flags
+- [x] Feedback latency < 10s
+- [x] `nyquist_compliant: true` set in frontmatter
+
+**Approval:** pending