Session outcomes
Password sign-in can return a Session, a pending two-factor challenge, an unverified email, a Ban or a refusal. Treat those as distinct outcomes. session-outcome.ts and two-factor-outcome.ts provide the shared interpretation; hooks own navigation and error presentation.
The server registers two-factor, admin, organization, passkey, Expo and MCP OAuth plugins. Email verification policy comes from AUTH_SKIP_EMAIL_VERIFICATION; setup makes the intended policy explicit. Server authorization always reads the database; Better Auth's signed cookie snapshot only answers the browser's presentation read (see Session reads).
Session reads
The session row in the database is the authority. Better Auth's cookie cache (session.cookieCache: compact, signed with HMAC, maxAge 60 s) keeps a snapshot of the session and user in the better-auth.session_data cookie (__Secure- on https). That snapshot only shapes the UI:
| Read | Source |
|---|---|
The browser's presentation read: the /_auth guard, useSession, tab focus (GET /api/auth/get-session) | The snapshot while it is younger than 60 s, without a statement; otherwise the database, which re-issues it |
| SSR guard and prefetches, the oRPC context, the files gateway, the admin guard and admin procedures | The database: getAuthorizedSession passes disableCookieCache |
Every other /api/auth/* request (organization endpoints, invitations, update-user) | The database: createAuth().handler strips the snapshot from the request (withoutSessionSnapshot), so Better Auth's own endpoints never authorize with it |
The read after this device changed its session (useAuthMutation({ resetSession })) | The database (disableCookieCache), which re-issues the snapshot so later presentation reads agree |
Every database read re-issues the snapshot, so server-rendered pages and oRPC responses also refresh it. The /_auth guard never waits on a cached signed-in session: it lets the navigation start and re-reads in the background once the read is older than 15 s (SESSION_STALE_MS). GET /get-session runs outside the request transaction.
What a revocation looks like:
| Change | UI shell | Data |
|---|---|---|
| Sign-out on this device | Gone at once: Better Auth expires both cookies | Refused |
| Sign-out in another tab | That tab leaves for /login at once (session-identity.ts) | Refused |
| Session revoked on another device (sign out everywhere, admin revoke, ban) | May stay for up to 60 s, until the snapshot expires or the page is reloaded | The first data request answers 401 and the app goes to /login |
| Member removed from the Active Organization | May keep showing the Organization | Refused at once: the membership check and RLS answer 403 |
| Platform admin demoted | Admin navigation and /admin re-read the role from the database | Admin procedures re-read it too |
The native app keeps the same cookies through the Expo client, so its useSession reads the snapshot under the same 60 s window. Its oRPC calls stay authoritative, a 401 clears the local session, and refreshAuthSession bypasses the snapshot after its own changes. To invalidate every snapshot at once (for example after changing what the session carries), set session.cookieCache.version.
Organizations and roles
Signup provisions a personal Organization. A User may be a Member of several Organizations; the Session selects one Active Organization. Todos and files belong to that Organization. Platform role admin grants global administration; Org roles owner, admin and member do not grant platform administration.
Membership must be checked at the operation, even if the UI already selected an Organization. An MCP token has no active selection and stays pinned to the User's personal Organization. See connecting agents.
Invitations
An invitation email is the app writing to a stranger on a signed-in User's behalf, so invite-member is treated as outbound mail, not as a form. Four controls apply, all in packages/auth (invitation-policy.ts):
- Role. Only the Organization roles
ownerandadminholdinvitation: create; amemberholds no write permission. These are Better Auth's default roles, passed explicitly in the plugin configuration so a change is a visible diff. - Verified inviter. The inviter's email must be verified, regardless of
AUTH_SKIP_EMAIL_VERIFICATION. With the defaulttrue, an account signs in unverified and can create Organizations, but its first invitation is refused withINVITER_EMAIL_NOT_VERIFIEDuntil the address is confirmed; the web dialog and the mobile invite group show that state and offer to send the verification email. The choice is deliberate: skipping verification is a sign-in convenience for the account holder, not a licence to send mail in their name. - Daily caps. Rolling 24-hour counts on the
invitationtable: 20 per inviter across all Organizations (INVITATION_DAILY_LIMIT_REACHED) and 50 per Organization across all inviters (ORGANIZATION_INVITATION_DAILY_LIMIT_REACHED), both HTTP 429. Better Auth'sinvitationLimitcaps pending invitations per Organization at 50 (INVITATION_LIMIT_REACHED). Constants live inINVITATION_POLICY. - Rate limit.
/organization/invite-memberhas its owncustomRulesentry, 10 requests per 10 minutes per client IP, next to the credential endpoints.
The checks run in beforeCreateInvitation, before the row is written and before any mail is sent, and again in a root hooks.before for the resend: true path, which re-sends an existing invitation without creating one. Counting runs on the handle Better Auth already holds (the auth.better-auth system scope, ADR-0009): one inviter's invitations span Organizations, so no tenant scope could see them all. The email itself never puts inviter text in the subject; see Email.
A refusal is a typed APIError; packages/errors maps each code to a message in every locale, and both clients show it through the shared mutation helper. Re-sending an existing invitation is not counted against the daily caps (the row already exists); the IP rule bounds it.
Rate limits
Better Auth rate limiting is on everywhere except Vitest. Its Postgres storage uses a separate connection and one upsert per counted request, so a rolled-back failure still counts. The hourly auth cleanup sweeps expired rows. The key is the trusted client IP (cf-connecting-ip on Workers, resolved by client-ip.ts) and the auth path.
| Path | Limit | Reason |
|---|---|---|
/get-session | Exempt | The read can answer from the signed snapshot without a database statement. |
/jwks | Exempt | Public keys; MCP loads them at most once a minute per isolate. |
/sign-in/email, /sign-up/email | 5 per 60 seconds | Limit credential guessing and account creation. |
/request-password-reset, /reset-password | 3 per 60 seconds | Limit password reset attempts. |
/organization/invite-member | 10 per 600 seconds | Limit outbound invitations. |
Every other path uses Better Auth's defaults: 100 per 10 seconds, with 3 per 10 seconds for built-in sign-in, sign-up, password change and email change paths unless overridden above. A 429 response carries Retry-After; the handler copies Better Auth 1.7.16’s X-Retry-After value to the standard header. Rate-limit tests opt in with NODE_ENV=production.
Web and native
Web auth hooks coordinate TanStack Query, forms and redirects. Mobile uses the Better Auth Expo client, secure credential storage and native passkey integration. Its route gate revalidates the Session and hides private content during a transition. Logout, expiry or an authoritative 401 clears private state. A 403 does not automatically sign out an otherwise valid Session.
Every web form with a password field sets method="post". The server-rendered ones (sign-in, sign-up, reset and change password) also keep submit disabled until useHydrated() is true, so a click before hydration never sends credentials in a GET URL.
Extend safely
Add auth behavior to the server factory and its tests, then expose the outcome through a hook. Keep email callbacks, membership checks and audit recording in their existing owners. Test revoked Sessions and Organization changes as well as successful login. Never treat an impersonated admin's original identity as permission to access /admin.