Reference: backend sources

DDD + Hexagonal (Clean Architecture)

Source

• Skill: .agents/skills/clean-ddd-hexagonal/SKILL.md and references/

Relevant rule

• Dependencies point inward: interfaces -> application -> domain; infrastructure implements domain ports.
• domain/ has no framework/DB/transport dependencies. Behavior lives inside entities (no anemic models). One repository per aggregate. Keep controllers thin. One aggregate per transaction; cross-aggregate consistency via events.

Project decision

• apps/api/src/{domain,application,infrastructure,interfaces}.
• Trip is the aggregate root; Stop, TripMember, Expense are contained. Money and SettlementPlan are value objects. Vote/comment/expense/split rules live in the domain.
• Repository ports live in domain/*/ports; PostgreSQL adapters implement them in infrastructure/persistence. See ../backend/domain.md.

Hono

Source

• Skill retrieval + Better Auth docs (Context7 /better-auth/better-auth).
• Upstream: https://hono.dev

Relevant rule

• Framework-agnostic web framework running on Node, Workers, etc. Better Auth mounts as app.on(["POST","GET"], "/api/auth/*", (c) => auth.handler(c.req.raw)).

Project decision

• Hono is the interfaces/http adapter. The same app is served by a Node entry (@hono/node-server) for Docker and a Workers fetch entry for Cloudflare. Routes parse input, call use cases, and format responses. See ../backend/api/README.md.

Better Auth

Source

• Skill: .agents/skills/better-auth-best-practices/SKILL.md
• Context7 /better-auth/better-auth
• Upstream: https://better-auth.com/docs

Relevant rule

• betterAuth({ database, emailAndPassword, trustedOrigins, ... }). Accepts a pg.Pool directly. BETTER_AUTH_SECRET (>= 32 chars) and BASE_URL via env. Node: toNodeHandler(auth); Web/Workers: auth.handler(request). Run the CLI migrate/generate after config or plugin changes.

Project decision

• Config in infrastructure/auth/auth.ts using a pg.Pool from the shared database module, emailAndPassword.enabled, and trustedOrigins from env. Mounted on Hono at /api/auth/*. Auth tables are created by SQL migration so the same schema applies to Docker Postgres and Hyperdrive-fronted Postgres. See ../backend/auth.md.

PostgreSQL

Source

• node-postgres (pg): https://node-postgres.com
• Prototype seed data (members, days, stops, expenses).

Relevant rule

• Use a pooled client. On Cloudflare Workers, external Postgres must be reached through Hyperdrive with Node.js compatibility enabled.

Project decision

• A single pg.Pool factory backs both Better Auth and repositories. Node reads DATABASE_URL; Workers read the Hyperdrive binding's connectionString. Plain SQL migrations in apps/api/migrations. See ../backend/database.md.