Three checks. The engine tests pin the overdue boundary from both sides: day 42 of a stated 28-day cycle still counts, day 43 stops counting and reports fifteen days later than usual. The round-trip test calls the real GET handler, reads the response body as text and parses it, so a field that both ends handle but the wire never carries fails here. It runs the same instant twice for two accounts in different timezones and gets two different answers, which is what the account timezone is for. It also checks the ring's cycle day against the phase engine the coach read uses, so the two cannot tell someone two different days. The guard reads the syntax tree of every file under components, hooks and app, and fails on a grace-period constant, on an overdue verdict computed rather than read, and on a cycle-day count compared against a sum. It follows local bindings, so lifting the threshold into a variable above the comparison does not hide it. A companion suite tries nine disguises against the same detector and pins five innocent shapes it must ignore, including an overdue medication dose.
src/app/
The Next.js App Router tree: the page surfaces a logged-in user sees and the REST API under api/. Server components are the default; "use client" is added only where a hook, state, or browser API needs it. Routing is file-based — a page.tsx is a page, a route.ts is an API endpoint.
API routes (api/)
Every endpoint wraps its handler in apiHandler (@/lib/api-handler), parses any body with Zod safeParse, narrows userId from the session or Bearer token (never from the body), and returns the { data, error, meta? } envelope. requireAdmin() is cookie-only, so api/admin/ is unreachable by Bearer token. Notable groups:
auth/— login, register, password, passkey (WebAuthn), refresh, Codex device-OAuth.measurements/,mood-entries/,medications/,sleep/— the core health-data CRUD + batch/bulk ingest.ingest/— external Bearer-token ingest surfaces.insights/,analytics/,dashboard/— AI insights, the Coach SSE stream, trend summaries, the first-paint dashboard snapshot.withings/,whoop/,fitbit/,integrations/,sync/— OAuth connect/sync/webhook surfaces and the offline delta feed.fhir/,share-links/,doctor-report/,export/,import/— clinician-facing FHIR R4 read API, shareable records, report + data export.notifications/,devices/,send/,telegram/— channel registration, device tokens, dispatch, webhook intake.admin/— operator panel APIs (cookie-only).health/,version/,meta/,internal/— health check, build-version probe, runtime metadata, worker-internal routes.
Page surfaces
measurements/, medications/, mood/, insights/, achievements/, notifications/, settings/, onboarding/, admin/, plus the public about/, privacy/, bugreport/, the share-record route c/, and the root dashboard (page.tsx). Shared shell + chrome lives in layout.tsx; error.tsx / global-error.tsx / not-found.tsx / loading.tsx cover the framework boundaries. layout.tsx holds the one nonce-bound dangerouslySetInnerHTML (theme bootstrap).
Conventions
See ../../CLAUDE.md. The request-flow walk in .planning/codebase/arch.md annotates each layer with file:line citations. Related dirs: handlers compose ../lib/; pages render ../components/.