ChooChoo for Devin.

# .devin/knowledge.md
# Generated by ChooChoo. Do not edit by hand.
# Run: choochoo context generate

## payments-api
A FastAPI service handling financial transactions.
Devin uses this file to understand what to build,
how, and what guardrails apply before opening a PR.

## Standards
- Python 3.12, strict mypy, Ruff (line-length=100)
- Pydantic models at every API boundary
- pytest, coverage ≥ 85% enforced in CI

## Boundaries
TOUCH:    src/** · tests/** · docs/**
DO NOT:   .github/** · migrations/** · infra/**
ASK:      schema changes, secrets, billing config

## Workflow Hints
- Open a draft PR after the first green test
- Reference ADR-### in commit messages
- Tag @platform-team for any infra-adjacent change

# SKILLS.md
# Generated by ChooChoo. Do not edit by hand.

## auth
JWT token lifecycle: creation, validation, refresh.
  Entry: src/auth/service.py
  Tests: tests/auth/

## payments
Stripe integration: charges, subscriptions, webhooks.
  Entry: src/payments/processor.py
  Note:  Never log STRIPE_KEY or card numbers

## database
SQLAlchemy sessions and query patterns.
  Entry: src/db/session.py
  Rule:  Always use get_db() dependency injection

## notifications
Email (SendGrid) and SMS (Twilio) dispatch.
  Entry: src/notifications/dispatch.py

# PLAN.md
# Generated by ChooChoo. Do not edit by hand.

## Goal
Refactor the authentication service to support
multi-factor authentication (MFA) via TOTP.

## Steps
1. [ ] Add TOTP secret column to users table
       migration: src/db/migrations/0023_add_totp.py
2. [ ] Implement TOTP validation in auth service
       src/auth/service.py → verify_totp()
3. [ ] Add /auth/mfa/setup and /auth/mfa/verify routes
       src/api/auth.py
4. [ ] Write unit tests for new MFA paths
       tests/auth/test_mfa.py (≥ 90% coverage)
5. [ ] Update AGENTS.md with new ADR-012

## Constraints
- Do not break existing JWT flow (ADR-001)
- TOTP secrets encrypted at rest (AES-256)
- Rate-limit /auth/mfa/verify to 5 attempts / 15 min

# ARCHITECTURE.md
# Generated by ChooChoo. Do not edit by hand.

## System Overview
payments-api is a stateless FastAPI service.
All state lives in PostgreSQL (primary data) and
Redis (sessions, rate limiting, event streams).

## Request Flow
Client → API Gateway → FastAPI → Service Layer
                                → Repository Layer
                                → PostgreSQL / Redis

## Key Modules
src/auth/        JWT issuance + TOTP (ADR-001, ADR-012)
src/payments/    Stripe integration (charges, webhooks)
src/db/          SQLAlchemy sessions + migration runner
src/api/         Route definitions (v1 + v2 namespaces)

## ADR Index
ADR-001  RS256 JWT for authentication
ADR-004  Redis Streams for webhook event bus
ADR-007  URL versioning (/v1/, /v2/)
ADR-012  TOTP-based MFA (in progress)

## Deployment
Docker → ECS Fargate  (app)
RDS PostgreSQL 15      (primary)
ElastiCache Redis 7    (cache + streams)

# GOAL.md
# Generated by ChooChoo. Do not edit by hand.

## Current Sprint Goal
Implement MFA support without breaking existing
single-factor authentication flows.

## Success Criteria
- All existing auth tests continue to pass
- New /auth/mfa/* endpoints return correct responses
- TOTP validation rejects tokens older than 30 s
- Coverage for src/auth/ stays above 90%

## Out of Scope
- SMS-based MFA (deferred to ADR-013)
- Admin UI for MFA management (separate ticket)
- Recovery codes (phase 2)

## Definition of Done
- PR reviewed and approved
- CI green (lint + test + coverage)
- AGENTS.md updated with ADR-012 summary
- Deployed to staging and smoke-tested

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