401, 403, 404 & Error Contract Use status semantics without leaking inaccessible resource existence
Phase 19 - Authorization, Ownership, RBAC & Permissions Volume 05 - Authentication & Security
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Phase 19 transforms verified identity into contextual, server-side authorization decisions.
401, 403, and 404 tell different security stories TaskFlow keeps authentication failures, permission failures, and existence-hiding behavior distinct.
Authenticated workspace member lacks delete permission 403 Identity known; action forbidden
Task not visible in caller workspace scope 404 Do not reveal whether an inaccessible task exists
For object lookups across tenant boundaries, hiding existence can reduce information disclosure. For an authenticated member who can see the task but lacks a specific action, 403 is clearer.
Keep the Phase 13 error envelope { "statusCode": 403, "code": "TASK_UPDATE_FORBIDDEN", "message": "You may not update this task.", "requestId": "...", "path": "/tasks/..." }
401 403 404 and Error Contract 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.
Restate the goal of “401 403 404 and Error Contract” as one observable behavior. Write the success signal before touching code.
Trace the boundary map: failure → typed/domain error → exception mapping → HTTP envelope → client handling. 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: 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.
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.
{
"error": {
"code": "TASK_NOT_FOUND",
"message": "Task was not found",
"requestId": "req_..."
}
}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.
Return to the nearest observable boundary: input, network, process log, database, or rendered UI. Compare actual evidence with the predicted path.
Change one variable at a time and reproduce the original failure after the fix; otherwise you have correlation, not diagnosis.
Without copying the final source, create a second small scenario that applies “401 403 404 and Error Contract” to a different TaskFlow resource or input. Write the acceptance criteria first, implement it, and provide the evidence that each criterion is satisfied.
List TaskFlow actions such as workspace.read, task.create, task.update, member.manage.
Use the smallest change that demonstrates this lesson. Stop after it works and capture evidence.Checking membership after performing the mutation
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.