summary system backend implementation

docs/services/chat-client.md

@@ -98,14 +98,15 @@ src/
 │   ├── MessageBubble.jsx    # Individual message bubble — renders markdown via react-markdown
 │   ├── InfoPanel.jsx        # Right panel — model selector and session metadata (slide-in)
 │   ├── SessionModal.jsx     # Modal for session rename, project assignment, delete
-│   ├── ProjectModal.jsx     # Modal for project create, edit, delete
+│   ├── ProjectModal.jsx     # Modal for project create/edit — name, description, colour,
+│   │                        #   system prompt override; delete confirmation
 │   ├── AllChatsView.jsx     # Paginated session list with project indicator column
 │   ├── AllProjectsView.jsx  # Project tile grid with create/edit/delete; tile click navigates to ProjectView
 │   ├── ProjectView.jsx      # Individual project — conversations, new chat input, memory
 │   │                        #   placeholder, user notes, ⋮ edit/delete menu
 │   ├── MemoryView.jsx       # Paginated, searchable, expandable, deletable episode viewer
-│   └── SettingsView.jsx     # Settings — Memory limits, Models (inference params, active
-│                            #   model, context window), Service Health, Appearance placeholder
+│   └── SettingsView.jsx     # Settings — Memory, Models, Behaviour (system prompt),
+│                            #   About, Appearance
 ├── index.css                # Global reset, CSS variables, utility classes
 └── main.jsx                 # React entry point
 ```
@@ -151,7 +152,7 @@ in the `ChatWindow` header.
 
 | View | Component | Trigger |
 |---|---|---|
-| `'home'` | `HomeView` | Initial load; going back from chat with no history |
+| `'home'` | `HomeView` | Initial load |
 | `'chat'` | `ChatWindow` | Selecting a session; new chat; sending from HomeView |
 | `'all-chats'` | `AllChatsView` | "All Chats →" or ☰ icon in collapsed rail |
 | `'all-projects'` | `AllProjectsView` | "View Projects" button or ⊞ icon |
@@ -178,10 +179,9 @@ leaving `'home'` expands it.
 - Centred textarea input — sending creates a new session and navigates to chat
 - Quick action pills that populate the input without auto-sending
 
-Sending from HomeView uses `handleHomeSend` in `App.jsx`, which calls
-`createSession()` (returns the new session object), then immediately calls
-`sendMessage` with the session passed directly as a parameter — avoiding the
-React state settling race condition that would cause the message to be dropped.
+`handleHomeSend` in `App.jsx` calls `createSession()` (which returns the new
+session object), then immediately calls `sendMessage` with the session passed
+directly — avoiding the React state settling race condition.
 
 ## CSS Architecture
 
@@ -283,6 +283,7 @@ mode, and delete confirmation in `confirm-delete` mode.
 - `useContextMenu` dismisses on a `window` click listener
 - Dynamic `updateSession` SQL builds `SET` clause from only the fields passed — prevents accidental overwrites
 - `AllChatsView` pagination uses `CLIENT_DEFAULTS.PAGE_SIZE` (not `API_DEFAULTS.PAGE_SIZE` which doesn't exist)
+- `Sidebar` groups sessions by project — `key` must be passed directly to `<SessionRow key={...}>`, not included in the props spread object
 
 ## Sidebar — Session Grouping
 
@@ -302,11 +303,27 @@ The isolated toggle has been removed from `ProjectModal`.
 `useProjects` fetches the project list from `GET /projects` on mount and
 exposes `refreshProjects` for keeping the sidebar in sync after mutations.
 
-`ProjectModal` handles create, edit, and delete confirmation. Fields: name
-(required), description (optional), colour picker.
+### ProjectModal Fields
 
-Clicking a project tile in `AllProjectsView` calls `onSelectProject` then
-navigates to `'project'`.
+- **Name** (required)
+- **Description** (optional)
+- **Colour** — picker from six preset hex values
+- **System Prompt** (optional) — overrides the global system prompt for all
+  conversations in this project. Leave blank to use the global default.
+  Stored as `system_prompt` (snake_case) matching the SQLite column.
+  `Enter` key does not submit — textarea fields make it ambiguous. Save button only.
+
+`handleSave` in `ProjectView` destructures `system_prompt` (snake_case) to
+match what `ProjectModal` sends. `updateProject` in `orchestration.js` uses
+a passthrough pattern — spreads all fields into the request body.
+
+### System Prompt Hierarchy
+
+System prompt resolution in `chat/index.js` (orchestration):
+
+1. `project.system_prompt` — if set on the project (highest priority)
+2. `settings.systemPrompt` — global setting from `settings.json`
+3. `ORCHESTRATION.SYSTEM_PROMPT` — hardcoded constant in `@nexusai/shared` (last resort)
 
 ### ProjectView
 
@@ -322,9 +339,8 @@ navigates to `'project'`.
   saved value (`savedNotes` state tracks the baseline, not `initialNotes`)
 
 `updateProject` in `orchestration.js` uses a passthrough pattern — spreads
-all fields directly into the request body, only transforming `isolated` if
-present. This allows partial updates like `{ notes }` without clobbering
-other fields.
+all fields directly into the request body. This allows partial updates like
+`{ notes }` or `{ system_prompt }` without clobbering other fields.
 
 For memory isolation behaviour, see `memory-isolation.md`.
 
@@ -337,9 +353,9 @@ buttons during in-flight requests.
 
 `SettingsView` receives `settings`/`saveSetting`/`saving` from a single
 `useSettings()` call at the top level and passes them as props to
-`ModelsSection` and `ModelsFolderSetting` — avoiding triple fetch on mount.
-`modelProps` (context window, loaded model) is fetched once in `App.jsx` and
-passed down as a prop, eliminating a duplicate fetch on every settings open.
+`ModelsSection`, `ModelsFolderSetting`, and `SystemPromptSetting` — avoiding
+triple fetch on mount. `modelProps` (context window, loaded model) is fetched
+once in `App.jsx` and passed down as a prop.
 
 `SettingsView` is organised into sections:
 
@@ -347,6 +363,9 @@ passed down as a prop, eliminating a duplicate fetch on every settings open.
 - **Models** — models folder path, temperature, repeat penalty, Top-P, Top-K,
   active model dropdown, read-only model info panel (file, size, context window,
   loaded model from llama-server)
+- **Behaviour** — global system prompt textarea (`SystemPromptSetting`). Save
+  button appears only when content differs from `savedPrompt` state. Saving an
+  empty string sends `null` which reverts to the hardcoded default.
 - **About** — service health check panel, version
 - **Appearance** — theme (coming soon)