301 · Self-serve class
Review the change.
Explain the decision.
An AI agent added refund retries to a payments service. It also changed logging and fees. Follow the evidence from Diagnose to a bounded repair plan.
What this class should change
- Shared intuition
- Understand what a tool notices, how it reaches its output, and what remains unchecked.
- Shared language
- Distinguish a signal, a finding, checked evidence, a defect, and a human decision.
- Shared behavior
- Follow the code, run a suitable check, preserve evidence, and keep repairs within their agreed scope.
Before you start
Keep the code beside the explanation.
This reader includes the lesson’s source files and recorded evidence. To execute commands, use your local payments fixture and SPEED checkout.
- You can read TypeScript and follow shell and Python code. SPEED vocabulary is introduced in the class.
- Run fixture commands from
301-config. Keep the SPEED implementation open alongside it. - The recorded fee reproduction used Node v26.9.0. The lesson’s source notes identify the environment and run behind each result.
Use Sources to inspect code, Commands to copy local commands, and Notes to retain questions. You can pause and resume at any step.
The connected walkthrough
01The payments change
Understand the support request, the four-file change, and who owns the requirements.
Diagnose
Explain how the first F2 rule produces a signal and what that observation leaves unchecked.
Review
Check the reviewer’s claims against the code, requirements, and a suitable reproduction.
Eval
Trace which test ran, what its pass establishes, and why the separate fee check is still needed.
Explain the fee defect
Connect the reproduced fee failure to its requirement, account impact, and the decision the product owner needs to make.
Define
Prepare an actionable defect draft with checked facts and provenance, then inspect the existing report without filing a duplicate.
Plan
Judge the proposed repair’s files, completion criteria, dependencies, and source references against the fee defect.
Recorded evidence and source material
The complete spoken lesson is preserved. Screenshots and saved results are historical evidence, labelled by their run. The lesson flags fresh Review output and generated fee-repair Plan tasks as still needing verification; this reader does not claim to have generated either.
Fixture checkout: aa7cebc. SPEED: 1de583a. Referenced files are snapshots of the teaching checkouts, including their working-tree contents.