Sign-In, Sign-Out & Session Lifecycle Create and terminate real Supabase sessions without confusing UI state with security state
Phase 17 - Supabase Authentication Volume 05 - Authentication & Security
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Phase 17 implements cookie-based Supabase Auth in Next.js. NestJS token verification remains Phase 18.
Sign-in establishes the cookie-backed session TaskFlow uses a Server Action to submit email/password to Supabase Auth. When authentication succeeds, @supabase/ssr writes the session into cookies through the server client/response path.
const { error } = await supabase.auth.signInWithPassword({ email, password, })
if (error) { redirect('/login?error=Unable+to+sign+in') }
revalidatePath('/', 'layout') redirect('/account')
Why the public error is generic Supabase sign-in errors can intentionally avoid distinguishing a missing account from a wrong password. TaskFlow preserves that privacy behavior instead of displaying account-enumeration hints.
Sign-out scope is a product decision Supabase JavaScript signOut supports global, local, and others scopes. JavaScript defaults to global. TaskFlow explicitly chooses local for the ordinary Sign out button so one browser session does not unexpectedly terminate the user on every other device.
await supabase.auth.signOut({ scope: 'local' })local Terminate the current session only
global Terminate all refresh sessions for the user
others Terminate other sessions while keeping current session
Revoking/signing out refresh-session state does not magically invalidate an already issued access token before its exp time. This is why short access-token lifetimes and server verification still matter.
Authentication answers who the request represents. Treating decoded or client-supplied identity as trusted is a security boundary failure.
Restate the goal of “SignIn SignOut and Session Lifecycle” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: credentials/session → token → verification → trusted identity → protected operation. Mark the one boundary this lesson changes.
Inspect the current repository state and record the exact files, route, table, or runtime involved. Avoid creating an abstraction before you can name the existing owner.
Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.
Connect the slice to TaskFlow’s phase artifact: Working TaskFlow authentication UI/session integration whose server-side checks are explicit and ready to hand tokens to NestJS.. Verify behavior from the outside as a user or API client would.
Create one controlled failure that is safe to reproduce. Predict the symptom first, capture evidence, locate the earliest broken boundary, then fix only that cause.
Close the reference and rebuild or explain the core change from memory. Record what you would monitor or test before trusting the same change in production.
const token = readBearerToken(request);
const claims = await verifier.verify(token);
request.user = {
id: claims.sub,
email: claims.email,
};Do not copy this as a finished answer. Predict what each boundary does, type the smallest useful slice, run it, then compare the result with your prediction.
Inspect whether a token exists, whether it is expired, which issuer/audience signed it, and what the API verifier expects.
Trust only verified server claims; never repair identity by accepting a client-sent user id.
Without copying the final source, create a second small scenario that applies “SignIn SignOut and Session Lifecycle” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Inspect the session/access token and prepare the boundary for NestJS verification without exposing service-role credentials.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Relying only on client-side route hiding
Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.Why does this responsibility live here, what input does it trust, what output proves success, and what would go wrong if another layer owned it?
If your explanation is vague, repeat the boundary trace before moving on.Close the reference. Reproduce the core idea from memory or explain the exact request/data flow aloud. Then check your diff or notes for accidental shortcuts that bypass validation, authorization, error handling, or verification earned in earlier phases.