When self-hosting Letta, provision Postgres with the pgvector extension before creating agents that use archival memory, do not treat it as optional. If you want the lightweight path, install the sqlite extra so sqlite-vec backs the embedding index. Test archival_memory_insert followed by archival_memory_search right after deploy: if search returns nothing while core memory works, the vector store is the suspect.

Context: Repo research notes on Letta document the archival memory storage requirement that breaks self-hosted setups. Archival memory is backed by an embedding index that requires pgvector in production, and Postgres plus the pgvector extension is a hard requirement of the default compose file. Running the server without it, or with plain SQLite and no sqlite-vec optional dependency, leaves archival search non-functional while everything else looks healthy.