Larger Context

WT-18868 introduces switch_role with a strict synchronous transition contract. This ticket verifies which parts of that contract can be relaxed.

Motivation

The workload model should enforce only the requirements needed for correct and deterministic role transitions.

Scope

Create a requirement matrix for transitions from each role. Use focused workloads to evaluate the following areas independently:

• Read transactions and cursor state across a transition.
• Leader-to-follower transition without a new checkpoint, and delayed checkpoint after a follower-to-leader transition.
• Minimum stable-timestamp preparation in each direction.

Keep active write transactions prohibited where WiredTiger requires write quiescence. Update validation only for behaviour proven safe by the focused workloads.

Acceptance Criteria

• The requirement matrix identifies required, optional, and unsupported behaviour.
• Each accepted relaxation has a fixed model workload with matching WiredTiger behaviour.
• Unsupported behaviour remains rejected, and strict switch_role workloads continue to pass.

Outcome

Test/model uses the minimum verified requirements for synchronous switch_role.