There is a semantic search API endpoint (/index_name/_semantic-search) that was released in the documentation, what is the reason this was removed?
I can't see that in the documentation sorry, but do you mean k-nearest neighbor (kNN) search | Elasticsearch Guide [8.6] | Elastic?
Well, it was removed. There is an endpoint something like _semantic-search that you can do in an index.
What version did you see it in?
If I'm not mistaken v8.5
I can't find a reference to this in GitHub about it. Unless you can find something concrete then not sure we can help sorry.
The _semantic_search endpoint existed in code for a while but was never released.
You would have seen it mentioned in docs with the yellow banner at the top saying, "You are looking at preliminary documentation for a future release. Not what you want? See the current release documentation."
We decided that instead of having a separate _semantic_search endpoint we'd be better off integrating the functionality into the standard _search endpoint. This was done in https://github.com/elastic/elasticsearch/pull/93531. The docs for it were added in [DOCS] Adds semantic search section to kNN search page by szabosteve · Pull Request #93782 · elastic/elasticsearch · GitHub. So you can read the docs for the upcoming text_embedding query type already in k-nearest neighbor (kNN) search | Elasticsearch Guide [master] | Elastic. However, once again you'll see the yellow banner at the top of this page, and you must be aware that unreleased functionality will not necessarily ever be released.
Thanks for clarifying!