C4 Level 3 — Core API Components
The internal architecture of the Core API, following the IDesign 4-layer pattern.
IDesign Layer Details
Clients Layer
The Accounting API no longer handles chat or webhook input directly. Channels (Slack, Teams, Web, Email) connect to the Conversation Agent, which manages multi-turn context, clarification, and language detection. The Conversation Agent calls the Accounting API via POST /solve.
| Component |
Triggers |
Responsibility |
| SolveController |
POST /solve from Conversation Agent |
Receive a single task (classified, with context), route to TaskManager |
| SchedulerController |
Cron (daily/weekly) |
Trigger MonitorManager for compliance checks |
| DashboardController |
Web UI requests |
Serve audit trail, analytics, config CRUD |
Managers Layer
| Component |
Orchestrates |
Responsibility |
| TaskManager |
ClassifyEngine → AgentManager |
Route user request to correct workflow |
| AgentManager |
LLMAccessor + AccountingProvider |
Run LLM agent loop with function-calling (max 15 turns) |
| MonitorManager |
RulesEngine + ComplianceEngine |
Daily checks: overdue bills, expense violations, month-end |
| AuditManager |
DataAccessor |
Log every action, support undo/reverse |
Engines Layer (pure logic, no I/O)
| Component |
Input |
Output |
| RulesEngine |
expense/invoice + company rules |
PASS / VIOLATION + reason |
| ClassifyEngine |
user message |
task_type (regex fast-path or LLM) |
| AmountEngine |
gross/net/vat_rate |
Calculated amounts, currency conversion |
| ComplianceEngine |
ledger data + month/year |
Checklist status, missing items |
Resource Access Layer
| Component |
External System |
Handles |
| IAccountingProvider |
Tripletex / Fiken |
Provider interface for all accounting operations |
| TripletexProvider |
Tripletex API v2 |
Auth, caching, rate limiting. Implements IAccountingProvider |
| FikenProvider |
Fiken API v2 |
OAuth2, rate limiting. Implements IAccountingProvider |
| LLMAccessor |
Gemini / Claude |
Function-calling interface, retry, fallback |
| DataAccessor |
D1 / Supabase |
Audit trail, company config, rules |
| NotificationAccessor |
Slack, Teams, Email |
Send alerts, chat responses |
| FileAccessor |
Local + OCR |
PDF text extraction, image OCR |