snapshot of https://github.com/mattermost/mattermost.git (master, 2026-09-16; blobs > 131072B omitted)

webapp/platform/client/CLAUDE.OPTIONAL.md

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+# CLAUDE: `platform/client/` (`@mattermost/client`)
+
+## Purpose
+- Implements the Client4 HTTP layer and WebSocket client used by all Mattermost web apps and plugins.
+- Source of truth for API endpoint definitions and low-level networking helpers.
+
+## Structure
+- `src/client4.ts` – REST endpoints, auth handling, retries.
+- `src/websocket.ts` – WebSocket manager for real-time events.
+- `src/helpers.ts` / `errors.ts` – shared logic for response parsing and error types.
+
+## Client4 Usage
+Singleton HTTP client for all Mattermost API requests. Methods return `Promise<ClientResponse<T>>`:
+
+```typescript
+interface ClientResponse<T> {
+    response: Response;  // Fetch Response object
+    headers: Headers;    // Response headers
+    data: T;            // Parsed response data
+}
+```
+
+### Usage Rules
+1. **Actions Only**: `Client4` should only be called from Redux actions, never directly in components.
+2. **Error Handling**: Always handle errors appropriately.
+
+## Adding New Endpoints
+Add new API methods to `client4.ts`. Keep signatures Promise-based.
+
+```typescript
+getSomething = (id: string) => {
+    return this.doFetch<SomethingType>(
+        `${this.getSomethingRoute(id)}`,
+        {method: 'get'},
+    );
+};
+```
+
+## Error Handling
+- Throw `ClientError` (see `errors.ts`) with enough context.
+- Include `forceLogoutIfNecessary` logic upstream in calling actions; do not couple that here.
+
+## WebSocket Client
+`websocket.ts` provides real-time event handling, connection management, and automatic reconnection. Accessed via `WebSocketClient` wrapper in web app.
+
+## Guidelines
+- Follow `webapp/STYLE_GUIDE.md → Networking`.
+- Each new server API must be added here first, including TypeScript types and tests.
+- Never reference React or browser globals—this package must run in Node.