Description

Under disagg.mode=switch with fast truncate enabled, reconcile on stable trips the __timestamp_no_ts_fix assertion select_tw->stop_txn >= select_tw->start_txn. Reproduces at ~5% of CONFIG.fail runs.

Root cause

WT-17272 (1) was not implemented. The truncate-vs-uncommitted-single-key-update case remains: there is no chain visibility check on the truncate-ingest path.

Short term fix

Since write conflict detection is properly implemented and we need testing for switch mode, we will serialise all truncates. All truncates can't have a contending write in test/format.