[CI] CoreWithMultipleProjectsClientYamlTestSuiteIT test {yaml=search.vectors/40_knn_search/Dimensions are dynamically set} failing

[elasticsearchmachine]

Build Scans:

• elasticsearch-periodic-platform-support #9199 / windows-2025_checkpart2_platform-support-windows
• elasticsearch-periodic #9129 / openjdk23_checkpart2_java-matrix

Reproduction Line:

gradlew ":x-pack:qa:multi-project:core-rest-tests-with-multiple-projects:yamlRestTest" --tests "org.elasticsearch.multiproject.test.CoreWithMultipleProjectsClientYamlTestSuiteIT" -Dtests.method="test {yaml=search.vectors/40_knn_search/Dimensions are dynamically set}" -Dtests.seed=473D05C923ECCC5F -Dtests.locale=hr-BA -Dtests.timezone=America/Bahia -Druntime.java=24

Applicable branches:
main

Reproduces locally?:
N/A

Failure History:
See dashboard

Failure Message:

java.lang.AssertionError: Failure at [search.vectors/40_knn_search:632]: field [test_index.mappings.properties.embedding.dims] is null

Issue Reasons:

• [main] 2 failures in test test {yaml=search.vectors/40_knn_search/Dimensions are dynamically set} (0.6% fail rate in 339 executions)

Note:
This issue was created using new test triage automation. Please report issues or feedback to es-delivery.

[elasticsearchmachine]

Pinging @elastic/es-data-management (Team:Data Management)

[nielsbauman]

Forwarding to the search team since the failure seems to be related to vectors/embeddings. Also note that the failure doesn't seem related to multi-project, as there are also failures for non-multi-project test suites, for example: https://gradle-enterprise.elastic.co/s/bpd5dtsawadb6.

[elasticsearchmachine]

Pinging @elastic/es-search-relevance (Team:Search Relevance)