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Phase 19 · Lesson 02

Link Supabase Identity to TaskFlow User

≈ 2 min core reading · 193 source/companion words
Learning contract

What you should be able to do after this

  • Explain Link Supabase Identity to TaskFlow User without relying on framework buzzwords.
  • Connect the lesson to the phase outcome: Enforce resource ownership, workspace membership, roles, and permissions on the API with server-side policies.
  • Reproduce the relevant behavior and verify it with evidence.
  • Diagnose at least one representative failure instead of guessing.
Figure 19.2 — TaskFlow boundary map
verified identity
resource lookup
membership
role/permission policy
allowed/denied use case
audit/error
This lesson belongs to Phase 19. Keep the full request/data path visible even when today's code changes only one box.
Instructor workflow: predict first → implement the smallest slice → run it → inspect evidence → break one assumption → diagnose → explain it back. Do not copy the whole code block before understanding the first failing boundary.

Link Supabase Identity to TaskFlow User Create a safe bridge between external identity and application-domain authorization data

Phase 19 - Authorization, Ownership, RBAC & Permissions Volume 05 - Authentication & Security

Architecture milestone

claims.sub

v

User.authSubject

v

User.id

v

Membership

Phase 19 transforms verified identity into contextual, server-side authorization decisions.

Link external identity to the application domain Supabase Auth owns authentication identity. TaskFlow owns User, Membership, Workspace, Project, and Task. We therefore add an explicit authSubject link instead of trusting email or stuffing all domain authorization into JWT claims.

model User { id String @id @default(uuid()) authSubject String? @unique email String @unique // ... }

Figure 1 - Identity mapping

Verified Supabase claims.sub

v

User.authSubject

v

TaskFlow User.id

v

Membership.userId

v

Workspace role + relationships

The external subject remains identity; the domain user remains application data.

Why nullable first?

Existing development rows already exist. Add the link as nullable, backfill trusted mappings, verify them, then consider making it required in a later migration.

Do not link by ordinary request body A browser must not be allowed to submit authSubject=user-X to claim another account. Linking is an onboarding/admin concern performed through a trusted path.

Executable lesson studio · supabase

Now turn the explanation into engineering skill.

Link Supabase Identity to TaskFlow User matters because it changes a real boundary in TaskFlow. The goal is to understand the inputs, owner, observable output, and failure modes before adding more abstraction.

By the end, you should be able to

  • Explain Link Supabase Identity to TaskFlow User in terms of concrete inputs, ownership, outputs, and evidence.
  • Implement or reproduce the smallest TaskFlow slice that demonstrates this supabase concept.
  • Diagnose one representative supabase failure using observable evidence instead of trial-and-error.
Figure 19.2B — Mental model
application
connection configuration
Supabase Postgres
database evidence
Read left-to-right while implementing. When debugging, walk right-to-left until the first observed fact differs from your prediction.
Code-along sequence

One coherent change at a time

  1. 01

    Restate the goal of “Link Supabase Identity to TaskFlow User” as one observable behavior. Write the success signal before touching code.

  2. 02

    Trace the boundary map: application → connection configuration → Supabase Postgres → database evidence. Mark the one boundary this lesson changes.

  3. 03

    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.

  4. 04

    Implement the smallest vertical slice. Add one coherent change, run the narrowest verification command, and read the output before continuing.

  5. 05

    Connect the slice to TaskFlow’s phase artifact: Permission model + guards/policies protecting TaskFlow workspace/task actions with deliberate 401/403/404 semantics.. Verify behavior from the outside as a user or API client would.

  6. 06

    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.

  7. 07

    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.

txtBoundary trace
Input -> owner -> transformation -> observable output -> failure evidence

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.

Verification

Prove the happy path

  1. Run the narrowest relevant command or request and require a clean exit/status.
  2. Inspect the boundary-specific evidence: terminal output, Network panel, database row/query plan, test report, container health, or deployment logs.
  3. Repeat the behavior once after the change so a one-off cached or stale result cannot masquerade as success.
Break it on purpose

Build debugging memory

  1. Role strings checked inconsistently in every route
  2. Change one assumption in the supabase example—identity, input, configuration, ordering, connectivity, or state—and predict the exact symptom before running it.
SymptomInvestigation path
Expected result does not appear

Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.

A shortcut appears to fix it

Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.

Closed-reference challenge

Can you transfer the idea?

Without copying the final source, create a second small scenario that applies “Link Supabase Identity to TaskFlow User” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.

Explain-back

Answer these without reopening the solution

  1. What problem does Link Supabase Identity to TaskFlow User solve in TaskFlow, and what would be observably wrong without it?
  2. Which part of the supabase boundary owns the decision, and which neighboring layer must not own it?
  3. What evidence proves the happy path instead of merely suggesting it worked?
  4. Name one realistic failure or abuse case and the first place you would inspect.
  5. If requirements doubled tomorrow, which part of this design should stay stable and which part is allowed to change?
Lesson studio

Turn the reading into skill

01

Do it

Map roles to capabilities without scattering role-name if statements across controllers.

Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.
02

Break it safely

Role strings checked inconsistently in every route

Predict the symptom before causing the failure. Then locate the earliest boundary where reality diverges from expectation.
03

Explain it back

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.
Exit ticket

Before marking complete

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.

← Authorization Mental Model and ThreatsRBAC Roles and Permission Matrix →