basalt-26.3.2-rc-20260908: crosscluster/logical/txnmode: TestTxnModeLWW failed

crosscluster/logical/txnmode.TestTxnModeLWW [failed](https://mesolite.cluster.engflow.com/invocations/default/5d15a619-5664-4606-90d0-90e2519cd159?testReportRun=3&testReportShard=3&testReportAttempt=1#targets-Ly9wa2cvY3Jvc3NjbHVzdGVyL2xvZ2ljYWwvdHhubW9kZTp0eG5tb2RlX3Rlc3Q=) on basalt-26.3.2-rc-20260908 @ [807558e5e81666af257c811e925e4cae570abc28](https://github.com/cockroachdb/cockroach/commits/807558e5e81666af257c811e925e4cae570abc28):

```
=== RUN TestTxnModeLWW
test_log_scope.go:172: test logs captured to: outputs.zip/logTestTxnModeLWW3780409546
test_log_scope.go:82: use -show-logs to present logs inline
test_server_shim.go:168: automatically injected a shared process virtual cluster under test; see comment at top of test_server_shim.go for details.
=== RUN TestTxnModeLWW/transactional
```

Parameters:
- attempt=1
- race=true
- run=3
- shard=3
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

Same failure on other branches

- #174924 basalt-26.3: crosscluster/logical/txnmode: TestTxnModeLWW failed [A-cdc C-test-failure O-robot T-cdc branch-basalt-26.3 release-blocker]
- #174873 basalt-26.3: crosscluster/logical/txnmode: TestTxnModeLWW failed [A-cdc C-test-failure O-robot T-cdc branch-basalt-26.3 release-blocker]
- #174380 basalt-26.3: crosscluster/logical/txnmode: TestTxnModeLWW failed [A-cdc C-test-failure O-robot T-cdc branch-basalt-26.3 release-blocker]

/cc @cockroachlabs/cdc

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*TestTxnModeLWW.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Start with the crosscluster/logical/txnmode.TestTxnModeLWW failure and inspect the linked test report and captured logs for the transactional subtest. Compare this failure with the related issues #174924, #174873, and #174380 on other branches. Done means identifying the cause and restoring a passing TestTxnModeLWW run under the reported race configuration.

Written by the indexing model from the issue text.