Every story sits in one of four schools, inside one subject, and declares one level. Start with the school that matches the question you are asking, then choose how much reasoning you want to do.
The regression suite recorded sixty real rider-days from production. Two years later it approved the wrong fare rule, then reported the correct fix as a regression.
Subject
03 · Software design, testing, and safe evolution +1 more
Content area
Behavior specification, regression evidence, and safe change +1 more
PackProof inspected every package through six cameras. Its weekly training table still invented physical evidence for packages no technician had examined.
Subject
11 · ML systems and decision quality
Content area
Label, outcome, and observation contracts +1 more
Outcome, observation, and labelUnknown versus negative labelLabel availability timeLabel lineage and revision
School IVHow intelligent systems are built and governedBeginner
The backfill matched every offset, key and timestamp. One value it read from outside the log had changed its mind about a day that had already been settled.
Subject
06 · Event-driven and analytical data systems +2 more
Content area
Event time, replay, and rebuild determinism +3 more
As-of enrichmentReplay determinismValid time versus assertion timeCross-key invariant+1
School IIIHow production systems are operated and trustedAdvanced
Future traffic returned to the old model release. One approved deal had already crossed the boundary in an old summary, then propagated through booking, collateral, notices, evaluation, and learning data.
Subject
12 · Generative model behavior, adaptation, and inference
Content area
Behavioral versioning, provider change, coexistence, migration, and rollback +1 more
Behavior bundleBehavioral release identityMixed-version coexistenceAttempt and descendant lineage+1
School IVHow intelligent systems are built and governedProfessional
Barge-in stopped the audio, the model, and the turn, and asked the tool to stop. The payment had already been accepted, and the assistant said it had been held.
Subject
13 · Agentic and multimodal product systems +3 more
Content area
Turn detection, full duplex, and interruption +3 more
The model proposed the right recovery. The human approved it. Then one lost cloud response split what the workflow knew from what production had already done.
Subject
13 · Agentic and multimodal product systems +3 more
Content area
Durable execution and authoritative workflow state +2 more
State persistence and checkpointingIdempotency keyExactly-once semanticsFencing token+1
School IVHow intelligent systems are built and governedProfessional