1. Identity model — email is the identity, three optional credential slots (username, password_hash, oidc_subject), the @-in-username ban that makes namespaces provably disjoint.
2. Login dispatcher — @-in-input decides the path. Single DB lookup.
3. Login paths — four ways in (username+password, email+password, email+magic-link, OIDC redirect) with their pre-conditions.
4. Magic-link eligibility ladder — the three-branch table with OIDC unconditional reject, password flag-gated, no-credential allowed.
5. Registration paths — four ways (/api/auth/register with full creds, email-only, grant-by-email invitation, OIDC JIT).
6. Anti-enumeration — per-endpoint table showing what each surface returns and why; explicit note that instance-wide policy stays visible.
7. Security trade-offs — mailbox-as-bypass (lenient vs strict), no native MFA, magic-link as bearer token, enumeration via timing.
8. Rate limits — the five caps from PR 12 + classic auth, with env knobs.
9. Audit events — table of 12 event names with reason keys; every entry verified grep-able in src/.
10. Migration path — what existing instances see when PR 16-20 land (forward-only, non-destructive).
11. Future direction — login_strategy — the seven-row matrix sketch as the explicit-policy north star.
12. Out of scope — TOTP/WebAuthn, external→internal promotion, session_kind, differentiated session TTL, OCM, email-verified gates (PR 23), device-bound tokens (PR 22), anti-enum timing parity, per-user opt-out, login_strategy implementation.
13. Related documents — cross-refs to magic-link-auth, ReBAC, share-integration, env-vars.
Edouard Vanbelle