Project 6: OAuth-Protected Integration App

Build a scoped OAuth integration with deterministic reconnect behavior and secure protected tool execution.

Quick Reference

Attribute Value
Difficulty Advanced
Time Estimate 2-3 weeks
Main Programming Language TypeScript
Alternative Programming Languages Python, Go
Coolness Level Level 4
Business Potential Very High
Prerequisites OAuth concepts, token lifecycle, API security
Key Topics Least privilege, auth challenge handling, scope enforcement

1. Learning Objectives

  1. Define least-privilege scopes per tool.
  2. Implement deterministic auth challenge and reconnect flows.
  3. Handle token expiry and scope errors gracefully.
  4. Trace auth failures without leaking sensitive data.

2. All Theory Needed (Per-Concept Breakdown)

OAuth in Conversational Tool Systems

Fundamentals OAuth in ChatGPT Apps protects user-specific data access by separating authentication from authorization and enforcing scopes. The key goal is controlled delegation, not “just login.”

Deep Dive into the concept A robust OAuth flow in this environment must align three layers: user consent, tool scope requirements, and runtime recovery behavior. Start by mapping every tool to minimum required scope. During execution, validate scopes on every protected call. On missing/expired credentials, return structured auth challenges so the host can guide reconnection.

Token lifecycle handling is core reliability work. Expiry, refresh, revocation, and insufficient scope are distinct failure modes and must produce distinct error envelopes. Avoid generic 401 responses. Include actionable guidance for recovery.

For security, keep tokens out of client logs and UI state where possible. Use server-side token handling and minimal exposure in component channels.

Minimal concrete example

error envelope:
{ code:"INSUFFICIENT_SCOPE", required_scope:"invoices.read", retryable:false, trace_id:"trc_901" }

3. Project Specification

3.1 What You Will Build

An app that accesses protected invoice data after user consent.

3.2 Functional Requirements

  1. Trigger connect flow for protected calls.
  2. Enforce scope checks in tool handlers.
  3. Handle token expiry with reconnect path.
  4. Return normalized auth errors.

3.3 Real World Outcome

User asks for private invoice list.
App prompts connect.
User grants scope.
Tool returns invoices.
Token expires later; reconnect flow resumes without lost context.

4. Solution Architecture

protected tool call -> token validator -> scope gate -> backend API -> normalized response
                      | failure
                      v
               auth challenge envelope

5. Implementation Guide

5.1 The Core Question You’re Answering

“How do I enforce least privilege while keeping user flows smooth during auth interruptions?”

5.2 Concepts You Must Understand First

  1. Scope matrix design.
  2. Token expiry and refresh patterns.
  3. Auth error normalization.

5.3 Questions to Guide Your Design

  1. What is minimum scope for each tool?
  2. How do you communicate reconnect needs clearly?
  3. Which auth events must be logged for security review?

5.4 Thinking Exercise

Create a failure taxonomy for missing token, expired token, and insufficient scope.

5.5 The Interview Questions They’ll Ask

  1. Difference between authentication and authorization?
  2. Why least privilege matters operationally?
  3. How should auth failures be surfaced in ChatGPT Apps?
  4. How do you test token lifecycle safely?
  5. What logs are safe vs unsafe in auth flows?

5.6 Hints in Layers

  • Hint 1: Build scope matrix before coding.
  • Hint 2: Normalize all auth errors.
  • Hint 3: Add forced-expiry tests.
  • Hint 4: Verify reconnect preserves prior intent.

5.7 Books That Will Help

Topic Book Chapter
Security boundaries “Foundations of Information Security” Auth/access sections
Defensive systems “Clean Architecture” Boundary control
Reliability under failure “The Pragmatic Programmer” Automation and tracing

6. Testing Strategy

  • Scope enforcement tests.
  • Forced token expiry tests.
  • Reconnect continuity tests.

7. Common Pitfalls & Debugging

Pitfall Symptom Solution
Over-scoped requests Review friction, security risk Least-privilege scope matrix
Generic 401 errors User confusion Structured auth challenge envelopes
Token leakage in logs Security incident risk Log redaction and strict telemetry schema

8. Extensions & Challenges

  • Add multi-provider auth support.
  • Add admin scope audit dashboard.
  • Add suspicious-auth anomaly alerts.

9. Real-World Connections

  • CRM account integrations
  • HR systems access
  • Finance reporting tools

10. Resources

  • OpenAI authenticate-users docs
  • MCP authorization specification
  • RFC 6749 and RFC 7636

11. Self-Assessment Checklist

  • I can design a scope matrix with least privilege.
  • I can recover from token expiry without flow breakage.
  • I can normalize and trace auth failures safely.

12. Submission / Completion Criteria

Minimum Viable Completion

  • Protected tools with scoped auth and reconnect flow.

Full Completion

  • Includes forced-expiry tests, secure logging, and clear recovery UX.