[DOC-13578]: Release note MB-68626

modules/release-notes/pages/relnotes.adoc

@@ -11,6 +11,7 @@ For information about new features and major improvements made in Couchbase Serv
 
 include::partial$docs-server-8.0.0-fixes-and-improvements.adoc[]
 include::partial$docs-server-8.0.0-breaking-changes.adoc[]
+include::partial$docs-server-8.0.0-known-issues.adoc[]
 
 == Documentation for Earlier Versions
 

modules/release-notes/partials/docs-server-8.0.0-known-issues.adoc

@@ -0,0 +1,39 @@
+
+[#known-issues-800]
+== Known Issues 8.0.0 (October 2025)
+
+For Couchbase Server 8.0.0 was released in October 2025,
+these are the known issues that aren’t yet resolved.
+
+
+
+[#dlist-known-issues-800-index-service]
+=== Index Service
+
+*https://jira.issues.couchbase.com/browse/MB-68626/[MB-68626]*::
+
+*Vector Index Batch Build Memory Consumption*
++
+When building multiple vector indexes in a batch, the system fetches random sample vectors from KV for all indexes simultaneously, even though only one index is trained at a time.
+If the indexer is not properly sized for build batch size, this can cause excessive memory consumption, leading to Out of Memory (OOM) kills.
++
+*Root Cause:* Indexer fetches and evaluates vectors for all indexes in the batch concurrently without throttling, creating significant memory overhead.
++
+*Symptoms:*
+
+* OOM kills during vector index build operations
+
+* High memory usage (HeapInUse approaching memory quota)
+
+* Fatal error: `runtime: out of memory`
+
+* Memory allocation failures during vector sampling
+
++
+*Workaround:* Properly size the indexer for random sample vectors
+and configure the index build batch size to limit the number of indexes built together
+by taking into account the available memory quota and vector sizes
+
+
+
+