0001 — Architecture and stack

Status

Accepted.

Context

We are implementing a Travel Planner SaaS from a design handoff (../reference/handoff.md). Requirements fixed the methodology (FSD frontend, DDD/Hexagonal backend), the stack (pnpm, React, TS, PostgreSQL, Better Auth, mapcn), and the repo template (../reference/template-agentic-coding.md).

Decision

• Monorepo with pnpm workspaces: apps/web and apps/api.
• Frontend: React + TypeScript + Vite, Feature-Sliced Design v2.1, cossUI primitives, make-interfaces-feel-better polish, mapcn/MapLibre for maps.
• Backend: Hono + TypeScript, Domain-Driven Design with a Hexagonal (ports & adapters) layout; the Trip aggregate holds the business rules.
• Persistence: PostgreSQL via pg, plain SQL migrations.
• Auth: Better Auth (email + password) sharing the DB pool.
• Docs & tooling: template-style AGENTS.md, docs/ tree, Makefile, docs:check, and CLAUDE.md/.claude symlinks.

Consequences

• Clear separation lets domain logic be unit-tested without DB/HTTP.
• FSD's downward import rule and DDD's inward dependency rule are enforced by structure and review.
• Rebuilding the prototype's template-engine components as real cossUI React primitives is upfront work but removes the dc-runtime dependency.