diff --git a/docs/SPEC-SpireTab-refresh.md b/docs/SPEC-SpireTab-refresh.md
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+# SPEC: SpireTab Refresh & Casting Fixes
+
+## 1. Objective
+
+Fix multiple issues with the SpireTab and spell casting system:
+
+1. **Cast bar not updating**: Spell cast progress (`castProgress`) doesn't update visually during combat
+2. **Casting doesn't cost mana**: Mana costs are not deducted when spells are cast
+3. **SpireTab full-screen experience**: SpireTab should be a dedicated screen where:
+   - Player cannot study skills (must climb down to exit spire first)
+   - Layout is optimized for combat focus
+4. **Confusing layout**: Current SpireTab layout is cluttered and needs refresh for better UX
+
+**Why**:
+- Casting feels broken when progress bar doesn't update
+- Players get free spells (no mana cost) which breaks game balance
+- Spire should feel like a separate "mode" with focused combat
+- Current layout confuses players about available actions
+
+## 2. Controls/API
+
+### Player-Facing Controls
+- **Climb Up/Down buttons**: Change floors (already exists)
+- **Spell selection**: Click to set active spell (already exists)
+- **Enter Spire Mode**: Button to enter dedicated spire screen (already exists)
+- **Cast progress bar**: Visual indicator of spell casting progress (BROKEN - needs fix)
+- **Climb Down to Exit**: Only way to leave spire mode (NEW behavior)
+
+### Modified Game Internals
+- `combatStore.ts`:
+  - `castProgress`: Should update 0-1 per tick (fix binding)
+  - `processCombatTick()`: Should properly deduct mana costs via `deductSpellCost()`
+- `SpireTab.tsx`:
+  - Remove study progress components (player can't study in spire)
+  - Remove crafting progress components (irrelevant in spire)
+  - Add "Climb Down" button to exit spire mode
+  - Refresh layout for clarity
+
+### Public API Changes
+None (internal bug fixes + UI refresh)
+
+## 3. Project Layout
+
+Follow modular architecture rules from AGENTS.md:
+
+### Files to Modify
+| File | Purpose | Line Count Check |
+|------|---------|------------------|
+| `src/components/game/tabs/SpireTab.tsx` | Main SpireTab component - refresh layout, remove study/crafting | Must stay <400 lines |
+| `src/components/game/tabs/SpireHeader.tsx` | Spire header - ensure maxFloorReached works | Must stay <400 lines |
+| `src/components/game/tabs/FloorControls.tsx` | Floor controls - add "Climb Down to Exit" | Must stay <400 lines |
+| `src/lib/game/stores/combat-actions.ts` | Fix mana deduction in `processCombatTick()` | Must stay <400 lines |
+| `src/lib/game/stores/combatStore.ts` | Ensure `castProgress` updates correctly | Must stay <400 lines |
+
+### Files to Create
+| File | Purpose | Line Count Check |
+|------|---------|------------------|
+| None (modifying existing files only) | | |
+
+### Stores to Use (NO LEGACY STORES!)
+- ✅ `useCombatStore` from `src/lib/game/stores/combatStore`
+- ✅ `useManaStore` from `src/lib/game/stores/manaStore`
+- ✅ `usePrestigeStore` from `src/lib/game/stores/prestigeStore`
+- ❌ NO `import from '@/lib/game/store'` (legacy!)
+- ❌ NO `import from '@/lib/game/store-modules/'` (legacy!)
+
+### Module Ownership
+- SpireTab UI: `components/game/tabs/`
+- Combat logic: `stores/combat-actions.ts`
+- Store state: `stores/combatStore.ts`
+
+## 4. Code Style
+
+Follow existing project conventions:
+- TypeScript strict mode, explicit type annotations
+- Zustand store patterns: `set()`, `get()` for state updates
+- Use modular stores ONLY (AGENTS.md rule)
+- Naming: camelCase for variables/functions, PascalCase for interfaces/types
+- No `any` types, use defined interfaces from `src/lib/game/types/`
+- Follow ESLint rules (run `npm run lint` before committing)
+- Use existing patterns for combat/spell casting
+
+### Key Patterns
+- Cast progress: `useCombatStore((s) => s.castProgress)` (0-1 value)
+- Mana deduction: Use `deductSpellCost()` from `src/lib/game/utils/`
+- Guard against undefined stores: Optional chaining `state?.castProgress`
+
+## 5. Testing
+
+### What to Test
+1. **Cast bar updates**: `castProgress` changes during combat ticks
+2. **Mana costs deducted**: Raw mana/elements decrease when spells cast
+3. **No studying in spire**: Study components not rendered when `simpleMode=true`
+4. **Climb down to exit**: Button appears in spire mode, clears `spireMode`
+5. **Layout refresh**: SpireTab renders cleanly without clutter
+
+### How to Test
+- Unit tests using Vitest (existing test framework)
+- Test files in `src/lib/game/stores/__tests__/`
+- Mock game state to simulate combat ticks
+- Assert castProgress changes over time
+- Assert mana decreases after spell cast
+- Use `useCombatStore.getState()` for assertions
+
+### Tooling
+- Vitest (test runner)
+- Zustand store testing patterns (use `getState()`)
+- Mock `deductSpellCost()` to verify calls
+
+## 6. Boundaries (Out-of-Scope Items)
+
+- No changes to spell definitions or damage calculations
+- No changes to attunement system (separate from spire)
+- No changes to prestige/system (unless directly related to spire exit)
+- No new tabs or major architectural changes
+- No changes to legacy store (we're avoiding it, not fixing it here)
+- No changes to other tabs (SkillsTab, CraftingTab, etc.)
+
+## Acceptance Criteria (Per Requirement)
+
+| # | Requirement | Acceptance Criterion |
+|---|-------------|----------------------|
+| 1 | Cast bar updates during spell casting | `castProgress` in combatStore changes 0→1 over time, and UI reflects this |
+| 2 | Casting costs mana | `rawMana` or element mana decreases by `spell.cost` when spell completes |
+| 3 | SpireTab is full-screen combat focus | Study/Crafting components NOT rendered when `simpleMode=true` |
+| 4 | Player must climb down to exit spire | "Climb Down" button visible in spire mode, clears `spireMode` on click |
+| 5 | Layout refresh for clarity | SpireTab has clear sections: Floor Info, Combat, Controls (no clutter) |
+| 6 | Use modular stores only | Zero imports from `store.ts` or `store-modules/` in modified files |
+| 7 | All files <400 lines | Pre-commit hook passes for all modified files |
+| 8 | Regression tests added | New test file `spire-tab-refresh.test.ts` passes in `npm run test` |
+
+## Verification Checklist (Do NOT implement until approved!)
+
+- ☐ SPEC.md committed to version control (not yet)
+- ☑ Every feature has explicit acceptance criterion (above)
+- ☑ Out-of-scope items listed (Boundaries section)
+- ☐ Human has reviewed and approved (**WAITING FOR THIS**)
+- ☐ No implementation code exists yet (correct - spec only)
+
+**I will NOT proceed to PLAN or IMPLEMENT phases until this spec is approved by you (the human).**
+
+Please review and approve, or request changes.
diff --git a/docs/project-structure.txt b/docs/project-structure.txt
index 109885f..88fb0bf 100644
--- a/docs/project-structure.txt
+++ b/docs/project-structure.txt
@@ -12,6 +12,7 @@ Mana-Loop/
 │   └── custom.db
 ├── docs/
 │   ├── GAME_BRIEFING.md
+│   ├── SPEC-SpireTab-refresh.md
 │   ├── project-structure.txt
 │   └── skills.md
 ├── download/