# Phase 10: Per-User Rate Limits — Subplan

## Goal

Enforce per-user daily AI message limits with admin-configurable defaults, per-user overrides, usage tracking, and frontend quota visibility.

## Prerequisites

- Settings table + service, admin panel, chat/message system

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## Tasks

- [x] **10.1** Add `max_ai_messages_per_day` nullable int to User model. Migration 008 (or 009).
- [x] **10.2** Seed `default_max_ai_messages_per_day` setting (default: 100).
- [x] **10.3** Create `backend/app/services/usage_service.py`: get_user_message_count_today, get_user_daily_limit.
- [x] **10.4** Enforce limit in `POST /chats/{id}/messages` before streaming (429 if exceeded).
- [x] **10.5** Add `GET /chats/quota` endpoint (used, limit, resets_at).
- [x] **10.6** Expose max_ai_messages_per_day in admin user schemas + service.
- [x] **10.7** Add `GET /admin/usage` stats endpoint (per-user daily counts).
- [x] **10.8** Frontend: show quota in chat header ("X/Y messages today").
- [x] **10.9** Frontend: admin usage page.
- [x] **10.10** Frontend: handle 429 in chat, routes, sidebar, i18n.
- [x] **10.11** Tests + verification.

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## Acceptance Criteria

1. Sending at daily limit returns 429
2. Admin configures default limit via settings
3. Per-user override works (NULL = use default)
4. Chat header shows usage counter
5. Admin usage page shows per-user stats
6. All UI text in en/ru

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## Status

**COMPLETED**