Epicenter auth

Better Auth owns hosted sessions and social-provider login. Epicenter clients hold signed session bearers behind stable Accounts. Self-hosted instances issue named-user sessions after passkey sign-in.

Read packages/auth/README.md and packages/auth/src/auth-contract.ts before changing client API shape. The README owns the explanation; the contract owns the signatures. Do not reconstruct OAuth grants, refresh-token rotation, client registrations, or a cookie-only dashboard client.

Ground external behavior

When correctness depends on Better Auth sessions, cookies, plugins, freshness, or provider linking, ask DeepWiki a narrow question against better-auth/better-auth, then verify decisive details against the installed source, types, tests, or official docs. Online examples may target another version.

Useful installed source landmarks are the bearer plugin, API session routes, API dispatch, internal adapter, and social callback routes. Epicenter's packages/server/src/auth/session-handoff.ts is a small issuance plugin, not a replacement session engine.

Global before-hooks run before plugin before-hooks. A management gate cannot assume bearer normalization has happened: use the public session API with explicit headers and test a real header-only request. Distinguish a rejected credential from a database failure; a transient fault must not retire good identity.

Client composition

Browser apps use createBrowserRedirectAuth({ appId, server }) with one build-configured AuthServer; the dashboard uses createHostedBrowserRedirectAuth. Never restore a server destination from saved preferences. Credentials must match the configured origin before publishing identity or making requests. The framework-independent createSessionAuth composes a launcher and persisted storage. It owns credential verification, ordered persistence, cancellation, and Account retirement in one runtime.

Desktop WebViews use createDesktopBrokerAuth. Bun holds the remote session and captures its boot Account. A failed relaunch must not give old windows the replacement Account. The host owns no application store or sync engine.

The Svelte adapter fromAuth makes state reads track through createSubscriber. Keep issuer, storage, and launcher conventions outside it. Retain the callback-capable concrete type where a callback route needs it.

Account lifetime

An application session keeps one person and one server for its entire lifetime.

AuthClient selects getState().account; it exposes sign-in, sign-out, profile, and state. Application HTTP and sockets use the captured Account. AuthIdentityState is the serializable principal projection for desktop bootstrap, with no credential or transport functions.

Preserve these guarantees:

• Disconnection and uninterrupted same-person reauthentication keep the same Account object. Navigation and host relaunch create new runtimes.
• Sign-out or account replacement permanently retires the old Account. Later sign-in creates a new Account even for the same principal.
• Retirement aborts HTTP and response streams and closes sockets. Pending authorization and retries check the captured lifetime after awaits.
• Caller cancellation stops that request without cancelling shared verification.
• An Account rejects foreign origins before attaching credentials and does not follow redirects. Ambient cookies cannot choose another principal.
• Retry, erase, blob, and inference work uses the captured Account, never a new read of mutable auth state.

Use packages/auth/src/account-lifetime.test.ts for lifetime schedules and apps/epicenter/src/account-transport.test.ts for real loopback HTTP and sockets. Retain delayed blob and stream regressions when replacing credential fixtures.

Persisted identity and network access

PersistedAuth is exactly { token, principalId }. The session token authorizes online access; the cached principal selects the local data partition. It is not an offline decryption key. Profile data is fetched on demand.

PersistedAuthStorage has a synchronous initial snapshot and set(value | null). The runtime reads initial once and serializes writes. Browser storage and preloaded native serialized storage adapt that port. Do not add old-format readers or suppress write failures.

A cached principal can boot local data without network access. Before first resource use, /api/session must confirm that the credential belongs to it. A rejection preserves local identity and publishes reauth-required. An unavailable server refuses traffic without deleting identity. A verified different principal retires and clears the old attachment.

account.fetch uses credentials: 'omit'. A 401 pauses that credential; retry once only if same-Account reauthentication installed another credential while the request was in flight. Preserve replayable bodies and check retirement before either dispatch. There is no automatic refresh exchange.

Sign-out retires locally immediately, clears persistence, and awaits a best-effort revocation attempt bounded to five seconds. Success does not confirm remote revocation. Replacement awaits old-token cleanup outside the storage queue so sign-out can still clear storage promptly. Native relaunch awaits the auth operation; do not turn revocation into fire-and-forget before process exit.

Sign-in and handoff

startSignIn begins a flow. completeSignIn consumes a callback; do not make one verb infer the other from a query string. Only callback-capable clients expose completion, narrowed with isCallbackAuthClient.

A launcher returns { status: 'launched' } for browser navigation or { status: 'completed', token } for in-process native completion. The runtime verifies the token, persists it, and publishes the Account. Repeated same-kind calls share one in-flight operation.

Success from completion means the identity is installed and published. The callback route must still leave with window.location.replace(...), including same-principal completion where no identity event fires. Do not open an application store inside the departing callback document.

startSignIn({ reauthenticate: true }) bypasses passive hosted Continue and asks for a completed provider/passkey sign-in. It must not sign out first, because uninterrupted same-person reauthentication preserves the Account.

The hosted handoff has exact approved callbacks, state, S256 PKCE, atomic single-use consumption, and short code expiry. URLs carry code and state, never a session token. Redemption creates an independent revocable session and inherits the source authentication age. Preserve shared transaction versions and local cancellation generations: old responses cannot overwrite new choices, even after the newer transaction completes. Revoke orphaned results where possible.

Native callback waiting must exist before opening the browser. Cancellation, timeout, disposal, and opener failure must clear waiters and queued callbacks. The remote session remains in Bun, never a WebView bootstrap.

Dashboard and management

The dashboard uses the same captured Account composition as browser apps. Key its mounted child and query cache on the Account object, not principal alone. Late profile, billing, or mutation results must stay with the old attachment, including sign-out followed by same-person sign-in.

The management client sends its captured Account bearer and expected principal. Hosted cookie auth belongs to the sign-in page. Preserve provider and passkey ceremonies without ambient-cookie fallback in dashboard operations.

Only the browser adapter enables challenge/state cookies for the exact same-origin /auth/link-social, /auth/passkey/generate-register-options, and /auth/passkey/verify-registration routes, with captured bearer and expected principal headers already attached. Their guard must resolve the explicit bearer before library cookie reads. Keep all other Account traffic cookie-free.

Sensitive changes require a live session younger than 600 seconds and the matching principal. Renewal and passive handoff do not reset authentication age. Ordinary social sign-in, including provider SSO, may create fresh permission; do not describe this as human-presence verification. A stolen fresh bearer has the same authority when presented as the signed session cookie.

Provider linking binds the principal at authorized initiation. Later sign-out cannot undo an already-authorized linking operation. Test callback binding and implicit same-email linking separately; they have different policy gates.

Resource validation and socket bounds

Hosted resource routes use requireBearerPrincipal with resolveRequestSessionPrincipal. The resolver calls Better Auth with only the explicit bearer and live session lookup. No cookie fallback or JWT verifier remains. /api/session is the resource identity projection, not another session engine.

Unknown, expired, or revoked credentials are 401. Database and infrastructure failures are retryable 503. The self-host deployment supplies its static-token resolver to the same resource guard and resolves valid tokens to INSTANCE_PRINCIPAL_ID.

Hosted sessions have a 30-day sliding expiry, updated after one day of use. Verify renewal through resource traffic, not only a direct helper call. Deployments need isolated session stores and secrets; client origin checks do not replace server-side deployment isolation.

A store socket is authenticated at admission and receives a server-computed 600-second deadline. Preserve deadline attachment across hibernation and cursor updates, check all input/output paths, and sweep idle sockets with an alarm. Revocation rejects the next admission; it is not immediate closure of all admitted sockets. Percent-encode signed tokens in bearer subprotocols because signature padding is illegal in raw WebSocket protocol names.

Boot selection

The mounted working owner reads the plain client's getState() once and passes the captured Account to product resource opening. Imports and preloads acquire no resources. Keep reactive .state reads in UI modules adapted with fromAuth. Callback and sign-out documents acquire no primary stores. Browser sign-in may start from a working page because the callback installs the next Account in a fresh document.

Honeycrisp supports signed-out local startup. Whispering has no accounts. Vocab requires an Account. Honeycrisp's Local and Personal routes select independently opened stores. One warning before explicit account changes authorizes interruption of active recordings and unsaved drafts, including work started while sign-in is pending. Desktop acceptance disposes the boot auth owner, serializes next-boot credentials behind its queued writes, awaits bounded token revocation, and restarts. Cancellation before acceptance leaves working windows open. The process never installs a successor Account; failed writes or restart keep old access fenced, and new pages show restart-required UI.

Browser departures make the UI inert and replace the document without waiting for producer or persistence drains. Deliberate sign-out retires the working document before credential clearing: its retirement notification must not race the bounded auth operation. Unexpected retirement enters a resource-free recovery destination. Recovery opens no resources until explicitly requested. A cancelled navigation or history restoration must not reactivate retired resources. Preserve component disposal, acquisition rollback, account fences, and independent source-library transfer lifetimes.