Dashboard URLs, Email Confirmation & SSR Flow Configure the identity provider so the code has a correct redirect and confirmation environment
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.
Configure Auth before writing UI code Authentication flows depend on dashboard configuration. If the Site URL or email template is wrong, perfectly correct Next.js code can still redirect to the wrong place or fail to establish an SSR session.
Local development configuration • Keep the Email provider enabled.
• Use email confirmation for the production-style learning flow.
• Set Site URL to http://localhost:3000 during local development.
• Add staging and production URLs to the allowed redirect list before deployment.
• Do not weaken confirmation or redirect policy merely to make testing easier.
SSR confirmation email template For the server-rendered PKCE-style flow used here, the confirmation email sends a token hash back to a server route that exchanges it for a session cookie.
{{ .SiteURL }}/auth/confirm?token_hash={{ .TokenHash }}&type=emailv
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The token hash is exchanged server-side; the authenticated session is then stored through the SSR cookie client.
Do not allow arbitrary destinations from user-controlled next parameters without validating same-origin/relative paths. This phase uses a fixed /account destination to keep the flow explicit.
Authentication answers who the request represents. Treating decoded or client-supplied identity as trusted is a security boundary failure.
Restate the goal of “Dashboard URLs Email Confirmation and PKCE” 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 “Dashboard URLs Email Confirmation and PKCE” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
Create browser and server Supabase clients with the correct key exposure model.
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.