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# Implementation Summary

**Session ID**: `phase22-session01-projection-contract` **Package**: apps/web **Completed**: 2026-07-05 **Duration**: 1.1 hours

***

## Overview

Created the Phase 22 v1 game projection contract for `apps/web`. The session added a pure, versioned, serializable `gameProjection.ts` module with neutral aggregate state, deterministic initial state, defensive browser-storage helpers, replay/mock persistence guards, and a same-reference reducer shell for later reducer sessions. Focused Vitest coverage now proves the contract shape, fallback parsing, storage behavior, serialization boundary, persistence guard behavior, and reducer no-op behavior.

***

## Deliverables

### Files Created

| File                                    | Purpose                                                                                                                                       | Lines |
| --------------------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------- | ----- |
| `apps/web/src/lib/gameProjection.ts`    | Versioned projection contract, initial-state factory, reducer shell, runtime guards, and persistence helpers.                                 | 696   |
| `apps/web/tests/gameProjection.test.ts` | Focused Vitest coverage for projection shape, determinism, parsing, storage, JSON boundaries, persistence guards, and reducer no-op behavior. | 345   |

### Files Modified

| File                                                                               | Changes                                                                       |
| ---------------------------------------------------------------------------------- | ----------------------------------------------------------------------------- |
| `.spec_system/specs/phase22-session01-projection-contract/spec.md`                 | Planned the session scope, success criteria, dependencies, and test strategy. |
| `.spec_system/specs/phase22-session01-projection-contract/tasks.md`                | Tracked and completed all 19 implementation tasks.                            |
| `.spec_system/specs/phase22-session01-projection-contract/implementation-notes.md` | Recorded task-by-task implementation evidence and verification commands.      |
| `.spec_system/specs/phase22-session01-projection-contract/code-review.md`          | Recorded review findings and resolved repairs.                                |
| `.spec_system/specs/phase22-session01-projection-contract/security-compliance.md`  | Recorded security and GDPR review results.                                    |
| `.spec_system/specs/phase22-session01-projection-contract/validation.md`           | Recorded final PASS validation evidence.                                      |

***

## Technical Decisions

1. **Pure projection authority**: Kept the v1 contract in `apps/web/src/lib/gameProjection.ts` with a type-only protocol import so later store sessions can fold events without adding a second runtime authority.
2. **Fail-closed persistence boundary**: Invalid, missing, wrong-version, or unsafe persisted data returns a fresh projection instead of partially trusting unvalidated browser storage.
3. **Reducer shell before slice behavior**: Exported `reduceGameProjection` as a same-reference no-op contract so Sessions 02-04 can add focused reducer slices without stealing scope in Session 01.

***

## Test Results

| Metric   | Value                                                      |
| -------- | ---------------------------------------------------------- |
| Tests    | 3169 full-suite passed, 1 skipped; 10 focused tests passed |
| Passed   | 3169 full-suite, 10 focused                                |
| Coverage | Not emitted by configured commands                         |

***

## Lessons Learned

1. The projection must stay derived-only; tests now guard against accidentally serializing existing source-of-truth, replay, prompt, path, provider, token, or secret data.
2. Defensive browser-storage helpers need explicit coverage for both read and write failures because future lifecycle sessions will rely on these helpers in page events.

***

## Future Considerations

Items for future sessions:

1. Add hero attention reducer behavior in Session 02 without changing the v1 root contract.
2. Fold the projection into the store and selectors in Session 05 through a single event-apply path.
3. Add debounced lifecycle persistence and local erasure coverage in Sessions 06 and 08.

***

## Session Statistics

* **Tasks**: 19 completed
* **Files Created**: 2
* **Files Modified**: 6
* **Tests Added**: 10
* **Blockers**: 0 resolved


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