What breaks in 2.4.6 with OpenSearch?

Magento 2.4.6 removed Elasticsearch support and made OpenSearch 2.x the only supported search engine. If you’re upgrading from 2.4.5 or earlier, this is the single biggest infra change you’ll hit.

What breaks:

• The Elasticsearch service. Magento won’t connect to ES 7.x anymore. You need to install OpenSearch 2.x alongside (or in place of) your existing ES, reindex the catalog, and update app/etc/env.php to point to OpenSearch.
• Custom search modules that hit Elasticsearch APIs directly. OpenSearch is API-compatible with ES 7.x for the basics but diverges on newer features. If you’ve written any custom search code, audit the API calls.
• Hosting provider configs. Cloudways, Nexcess, JetRails, MageMojo all support OpenSearch but may need a config flip. Self-hosted: install OpenSearch from the official RPM/DEB repo.
• Memory footprint. OpenSearch 2.x can use slightly more RAM than ES 7.x on the same index. If you’re running 4GB JVM heap, give it 6-8GB.

What doesn’t break: the storefront search UI is unchanged, the admin search-config screen is unchanged, third-party search extensions (Algolia, Klevu, Mirasvit) keep working because they bypass the Magento built-in search.

Workflow: install OpenSearch alongside Elasticsearch, repoint Magento to OpenSearch, smoke-test, decommission Elasticsearch a week later. Don’t do them simultaneously.