Confluence DC supports OpenSearch since version 9.0 but doesn't officially supports Vector Search.

Opensearch offers Vector Search (also known as, Semantic Search) that will enhance search outcomes in Confluence.

Semantic Search

Semantic search helps search engines understand queries. Unlike traditional search, which takes into account only keywords, semantic search also considers their meaning in the search context. Thus, a semantic search engine based on a deep neural network (DNN) has the ability to answer natural language queries in a human-like manner

Suggestions:

To offer official support for vector search in Confluence