LEDGER
The financial system of record with a strict API/UI split.
Ledger is the FastAPI core for the finance domain. Its docs keep the API on port 4000 and the UI on a separate surface, with clean-architecture boundaries preserved end to end. It is the canonical source of truth for financial workflows.
Overview
The Ledger is the core financial engine and canonical system of record for the ecosystem. It is built to process financial workflows with extreme precision and enforce a strict boundary between data authority and user interface.
Architecture
The system employs a strict split boundary: the backend is a FastAPI application written in Python 3.11, while the frontend (ledger-ui) is a Next.js 15 application utilizing React 19 running in an internal Docker container. The backend strictly adheres to Clean Architecture principles, isolating pure business rules (Domain Layer) from workflow orchestration (Application Layer) and persistence mechanisms (Infrastructure/SQLite).
Problem It Solves
Financial tracking requires data immutability, precision, and deterministic workflows. Tightly coupling financial data logic with presentation layers often results in data corruption or logic leaks; this API isolates the math from the interface.
Current State
Hardened and stable. The system-of-record boundary is enforced, the API operates independently on port 4000, and the split between the financial engine and the UI is fully documented.
MILESTONES
API/UI Split Documented
FastAPI system-of-record boundaries and split API/UI ports are documented for the finance domain.