commit: 8c5002b06fd737f75941a73785ce75e3ca7f5ce1 1. Put a 5 second sleep between (1) and (2) to increase the chance that another transaction starts in between. Unable to find source-code formatter for language: c++. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml opObserver->onTransactionPrepare(opCtx); lk.lock(); _checkIsActiveTransaction(lk, *opCtx->getTxnNumber(), true ); invariant(_txnState == MultiDocumentTransactionState::kPrepared); + sleep(5); opCtx->getWriteUnitOfWork()->prepare(); 2. repro.js: Unable to find source-code formatter for language: cpp. Available languages are: actionscript, ada, applescript, bash, c, c#, c++, cpp, css, erlang, go, groovy, haskell, html, java, javascript, js, json, lua, none, nyan, objc, perl, php, python, r, rainbow, ruby, scala, sh, sql, swift, visualbasic, xml, yaml const session = db.getMongo().startSession({causalConsistency: false }); const sessionDB = session.getDatabase( 'test' ); sessionDB.a.insert({x: 1}); session.startTransaction({readConcern: {level: "snapshot" }}); assert .commandWorked(sessionDB.runCommand({ update: 'a' , updates: [{q: {x: 1}, u: {$inc: {x: 1}}}], })); let awaitShell = startParallelShell(function() { const session = db.getMongo().startSession({causalConsistency: false }); const sessionDB = session.getDatabase( 'test' ); while (1) { session.startTransaction({readConcern: {level: "snapshot" }}); sessionDB.a.find().toArray(); session.abortTransaction(); } }); assert .commandWorked(sessionDB.adminCommand({prepareTransaction: 1})); session.abortTransaction(); awaitShell();