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# Implementation Summary

**Session ID**: `phase24-session04-combat-playback-effects-layer` **Package**: apps/web **Completed**: 2026-07-08 **Duration**: 2 hours

***

## Overview

Session 04 shipped the battlefield combat playback effects layer for linked Legion camps. Real linked mission events now derive bounded presentation state for strikes, failed-result counterattacks, combo/stage props, display-only HP drain, and verified-kill burn-down effects while preserving projection, storage, protocol, server, reward, and privacy boundaries.

***

## Deliverables

### Files Created

| File                                                          | Purpose                                                                                                   | Lines |
| ------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------- | ----- |
| `apps/web/src/lib/combatPlaybackEffects.ts`                   | Pure linked-combat playback selector, caps, HP display, verification mapping, and safe presentation model | 496   |
| `apps/web/src/components/battlefield/CombatPlaybackLayer.tsx` | Battlefield effects layer for strikes, counterattacks, combo stages, stage props, HP drain, and burn-down | 467   |
| `apps/web/tests/combatPlaybackEffects.test.ts`                | Pure model tests for linked-only playback, combos, stage props, HP drain, verification, caps, and privacy | 412   |
| `apps/web/tests/CombatPlaybackLayer.test.tsx`                 | Component tests for caps, cleanup, reduced motion, joint assault, counterattacks, and product-facing DOM  | 343   |

### Files Modified

| File                                                                   | Changes                                                                                                                             |
| ---------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------- |
| `apps/web/src/components/battlefield/Battlefield.tsx`                  | Wired combat playback inputs from store selectors, camp links, ranked camps, hero coordinates, hero names, and reduced-motion state |
| `apps/web/src/components/battlefield/CampLayer.tsx`                    | Exported camp placement contracts and coordinate helpers without changing camp authority                                            |
| `apps/web/src/index.css`                                               | Added combat playback motion classes, stage props, HP chips, burn-down treatment, and reduced-motion overrides                      |
| `apps/web/tests/Battlefield.test.tsx`                                  | Added integration coverage for linked strike, counterattack, verification-only kill, unlinked no-op, and layer order                |
| `.spec_system/specs/phase24-session04-combat-playback-effects-layer/*` | Added session spec, task checklist, implementation notes, code review, security report, validation report, and this summary         |
| `.spec_system/PRD/phase_24/PRD_phase_24.md`                            | Marked Session 04 complete and advanced phase progress                                                                              |
| `.spec_system/state.json`                                              | Cleared current session, appended completed session, and recorded completion history                                                |
| `apps/web/package.json`                                                | Bumped package patch version                                                                                                        |
| `package-lock.json`                                                    | Matched the `apps/web` package version                                                                                              |

***

## Technical Decisions

1. **Pure model before React rendering**: Event selection, caps, combo state, display HP, and verification matching live in `combatPlaybackEffects.ts` so trust boundaries can be tested without the component layer.
2. **Presentation-only battlefield layer**: `CombatPlaybackLayer` reads selector-fed projection evidence and owns only transient UI timers; it does not write to the store, mutate projection, unlock rewards, or persist progress.
3. **Evidence-backed kill visuals**: Burn-down state is derived only from successful `task_verification` evidence that can be related to a linked mission and camp.
4. **Hashed effect references**: Raw mission and tool identifiers are hashed before becoming effect keys or DOM test ids to avoid leaking sensitive producer data.

***

## Test Results

| Metric         | Value                               |
| -------------- | ----------------------------------- |
| Focused Tests  | 49                                  |
| Focused Passed | 49                                  |
| Root Tests     | 3343                                |
| Root Passed    | 3342 passed, 1 skipped              |
| Coverage       | Not reported by configured commands |

***

## Lessons Learned

1. Transient battlefield effects still need privacy review because DOM ids and test ids can leak raw event identifiers if not sanitized.
2. Verification events do not always carry enough direct mission context, so unmatched verification must remain a no-op instead of guessing a camp kill.
3. Reduced-motion parity is easier to keep honest when static twins are added in the same component pass as motion effects.

***

## Future Considerations

Items for future sessions:

1. Session 05 should layer scrying posture and alert focus on top of the new combat playback without adding competing pulse sources.
2. Session 06 can reuse the bounded strike categories for world cues and bark routing.
3. Session 07 should regression-test replay, reconnect, mock, persistence, and privacy boundaries against the completed playback layer.
4. Session 08 should connect generated Phase 3 asset sheets through typed app references rather than runtime discovery from `assets/generated`.

***

## Session Statistics

* **Tasks**: 22 completed
* **Files Created**: 4 app/test deliverables plus 6 session artifacts
* **Files Modified**: 9 closeout and app/test files, plus phase/game-design documentation already in the session surface
* **Tests Added**: 17 focused combat playback tests across the new pure and component files, plus battlefield integration coverage
* **Blockers**: 0 resolved


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