In the explain queryPlan of join-optimized plans:

• Rename stages: NESTED_LOOP_JOIN_EMBEDDING to NESTED_LOOP_JOIN, HASH_JOIN_EMBEDDING to HASH_JOIN, INDEXED_NESTED_LOOP_JOIN_EMBEDDING to INDEXED_NESTED_LOOP_JOIN, INDEX_PROBE_NODE to INDEX_PROBE.
• Replace leftEmbeddingField/rightEmbeddingField on join nodes with embedAs on the root of each embedded collection's access path (no 'none' sentinel).
• Serialize joinPredicates with output-document paths (prefixed with the $lookup as field; base collection fields unprefixed).

Done together so the join and plan stability golden files are regenerated once.