Three days of a colleague's work vanished from main
A colleague reports that their commits from the last three days are gone from `main`. `git log` on `main` shows your commits but not theirs. They have not deleted anything and their local branch still has their work.
You rebased your feature branch onto `main` yesterday to tidy the history, then pushed. The push was rejected as non-fast-forward, so you used `git push --force` and it succeeded.
Explain the exact mechanism by which their commits left main, whether the work is recoverable and how, and what single flag would have prevented this while still letting you push your rewritten branch.
Choose how you want to be interrogated
The same case under two modes is two different exercises. If you are unsure, RCA drill is the one that trains root-cause analysis most directly.
RCA drill
A symptom, and nothing else. Find the cause and prove it.
Trains: Hypothesis generation, ranking by prior, and naming the test that discriminates.
Red team
You propose. It attacks. It is trying to make you wrong.
Trains: Defending a position under pressure, and noticing when you should concede.
Socratic
Questions only. It will never tell you the answer.
Trains: Deriving from first principles instead of retrieving from memory.
Design review
Present an architecture. Justify every trade-off you made.
Trains: Stating what you optimised and what you gave up, on purpose.
Viva
Rapid escalating questions. Ends in a graded verdict.
Trains: Answering under time pressure without hedging.
Integration
Problems that span several domains at once. The hardest mode.
Trains: Reasoning across boundaries, where the cause is in a different system to the symptom.
Before you start: you begin locked. The Mentor will give you nothing — not a nudge, not a category — until you state a specific position and the mechanism you think produces it. Four genuine attempts unlock the resolution. There is no shortcut.