[CI] BWC failures on 9.0.7 due to assertion error

[mark-vieira]

When investigating the root cause of these failures I notice the following exception on one of the nodes: https://gradle-enterprise.elastic.co/s/sn7ogqaqosr7w/tests/task/:x-pack:plugin:esql:qa:server:mixed-cluster:v9.0.7%23yamlRestTest/details/org.elasticsearch.xpack.esql.qa.mixed.EsqlClientYamlIT?page=eyJvdXRwdXQiOnsiMCI6Mn19&top-execution=1

[2025-11-19T20:41:32,447][ERROR][o.e.b.ElasticsearchUncaughtExceptionHandler] [test-cluster-0] fatal error in thread [elasticsearch-error-rethrower], exiting
java.lang.AssertionError: cluster:internal/xpack/ml/auditor/reset[n]
	at org.elasticsearch.transport.InboundAggregator.lambda$new$0(InboundAggregator.java:47) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundAggregator.initializeRequestState(InboundAggregator.java:198) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundAggregator.headerReceived(InboundAggregator.java:67) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundPipeline.headerReceived(InboundPipeline.java:139) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundPipeline.forwardFragments(InboundPipeline.java:113) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundPipeline.doHandleBytes(InboundPipeline.java:97) ~[elasticsearch-9.0.7.jar:?]
	at org.elasticsearch.transport.InboundPipeline.handleBytes(InboundPipeline.java:62) ~[elasticsearch-9.0.7.jar:?]

[elasticsearchmachine]

Pinging @elastic/ml-core (Team:ML)

[benwtrent]

Labeling as a blocker. Bwc means we might actually break bwc with an upgrade :(

[davidkyle]

These open backport PRs will fix this issue

• [9.2] [ML] Fix mixed cluster tests where nodes action is not available (#137456) #137881
• [9.1] [ML] Fix mixed cluster tests where nodes action is not available (#137456) #137882

[breskeby]

MArking as stateful blocker only as this otherwise stops serverless promotion