What is the difference between symmetric and asymmetric embedding tasks?

Symmetric tasks compare two pieces of text of similar style and length, like duplicate question detection or sentence similarity. Asymmetric tasks compare a short query against a longer document, which is the standard RAG retrieval pattern. Models trained for symmetric similarity may underperform on asymmetric retrieval because query and passage have different distributions, so many embedding models use separate query and passage encoders or special prefixes like query and passage prepended to the input. Always check which mode your model expects before deployment. ---