# Chat History Persistence & Cross-Device Sync

## New File: `src/chat-history.ts`
- Added `PersistedMessage` and `ChatHistoryData` interfaces for typed storage
- `loadChatHistory()` — reads from `chat-history.json` in the plugin folder via `vault.adapter`
- `saveChatHistory()` — writes user/assistant messages to disk (strips system/tool messages)
- `clearChatHistory()` — writes an empty history file (not deletion) for reliable Obsidian Sync propagation
- `toPersistableMessages()` / `toRuntimeMessages()` — conversion between runtime `ChatMessage[]` and storage format
- `isValidChatHistory()` — strict type guard for safe JSON parsing with version check

## Modified: `src/chat-view.ts`
- On **open**: restores persisted chat history, renders user messages as plain text and assistant messages as markdown (with wiki-link navigation)
- On **message send**: debounced save (500ms) after user message and after assistant response completes
- On **close**: flushes pending save and cleans up debounce timer
- On **clear chat**: writes empty history file and updates sync snapshot
- Added `reloadChatHistory()` public method for external sync triggers; skips reload if streaming is active to avoid UI disruption
- Added `saveChatHistoryDebounced()` with snapshot update to prevent false sync reloads from local writes

## Modified: `src/main.ts`
- Added `onExternalSettingsChange()` — reloads settings and checks for chat history changes when Obsidian Sync updates `data.json`
- Added `visibilitychange` DOM event listener — checks for synced changes when the app regains focus (covers device switching)
- Added `checkChatHistorySync()` — snapshot-based change detection that reloads the chat view only when the persisted file differs from the known state
- Added `updateChatSnapshot()` — called after local saves and restores to prevent false sync triggers
- Added `buildChatSnapshot()` helper — lightweight string comparison using message count and last message content