New "Usage" tab in Settings showing token consumption analytics:
- **Data cards**: Total Tokens, Total Cost, Sessions, Cache Hit Rate
- **Bar chart**: Daily token usage with model/provider color grouping
using recharts v3, with custom tooltip and continuous date x-axis
- **Provider tracking**: Each session now records the active provider
name (e.g. "Kimi Coding Plan") so the chart distinguishes usage
across different providers, not just model names
Backend changes (db.ts):
- Added `provider_name` column to chat_sessions with auto-migration
- Added `getTokenUsageStats(days)` with summary + daily aggregation
- SQL uses `json_valid()` guard to prevent malformed JSON crashes
- Fixed off-by-one: 7D now shows exactly 7 calendar days, not 8
- Provider-qualified grouping: shows provider name when set,
plain model name when using direct Anthropic
API changes (route.ts):
- Persists effectiveModel and activeProvider name on every message
- Captures model from SDK init event for accurate tracking
- New GET /api/usage/stats endpoint
Frontend fixes:
- SettingsLayout: replaced useEffect+setState with useSyncExternalStore
to fix react-hooks/set-state-in-effect lint error
- UsageStatsSection: AbortController prevents request race on rapid
range switching; cache hit rate formula corrected to
cache_read/(cache_read+input); date gaps filled with zeros for
continuous x-axis
- Full i18n support (en + zh)
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
