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# Implementation Summary

**Session ID**: `phase16-session03-data-layer-demo-fixtures` **Completed**: 2026-06-02 **Duration**: 0.7 hours

***

## Overview

Expanded the Hermes client data layer to cover the new Phase 16 read and write contracts, added bounded demo fixtures for the new domains, and locked the behavior down with focused parser and hook tests. The session kept write access behind `useHermesAdmin`, preserved the existing read-state modes, and avoided optimistic cache mutation in favor of success-only invalidation.

***

## Deliverables

### Files Created

| File                                     | Purpose                                        | Lines |
| ---------------------------------------- | ---------------------------------------------- | ----- |
| `src/lib/__tests__/hermes-types.test.ts` | Expanded read parser and demo fixture coverage | \~180 |

### Files Modified

| File                                            | Changes                                                                                                                   |
| ----------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------- |
| `src/lib/hermes-types.ts`                       | Added read payload types and parsers for connections, profiles, templates, session detail, missions, documents, and trash |
| `src/lib/hermes-admin-types.ts`                 | Added admin write request/response types and parsers for image, mission, sync, document, and Obsidian writes              |
| `src/hooks/use-hermes.ts`                       | Added query keys, options, result fields, read queries, token gating, and document file helper                            |
| `src/hooks/use-hermes-admin.ts`                 | Added domain mutation groups, duplicate-trigger prevention, and query invalidation for new writes                         |
| `src/lib/hermes-demo-data.ts`                   | Added bounded fixture data for expanded domains and exported it through `HERMES_DEMO_DATA`                                |
| `src/lib/__tests__/hermes-admin-types.test.ts`  | Covered new admin parsers and malformed payload rejection                                                                 |
| `src/hooks/__tests__/use-hermes.test.tsx`       | Covered new read queries, token gating, offline behavior, malformed payloads, and file helper results                     |
| `src/hooks/__tests__/use-hermes-admin.test.tsx` | Covered new admin actions, duplicate prevention, invalidation, and disabled/token/offline states                          |

***

## Technical Decisions

1. **Parser-first client contracts**: Live and demo payloads share the same typed parsers so the hook layer does not invent UI-only shapes.
2. **Success-only invalidation**: Admin writes invalidate affected queries only after successful bridge responses, which keeps cached state aligned with the backend contract.

***

## Test Results

| Metric   | Value |
| -------- | ----- |
| Tests    | 70    |
| Passed   | 70    |
| Coverage | N/A   |

***

## Lessons Learned

1. The new Hermes domains fit cleanly into the existing read-view and mutation-view split.
2. Bounded demo data is enough for later UI sessions as long as it stays on the same typed payload shapes as live responses.

***

## Future Considerations

1. Sessions 17-20 can consume the new hooks without adding more bridge work.
2. The next UI pass should continue to treat admin writes as explicitly gated, side-effecting operations.

***

## Session Statistics

* **Tasks**: 21 completed
* **Files Created**: 1
* **Files Modified**: 8
* **Tests Added**: 3
* **Blockers**: 0 resolved


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