Presets

A preset is a named snapshot of settings that can be loaded in one click. Lancy keeps two independent kinds, and they are not interchangeable.

Kind	Snapshots	Effect	Who may write
Retrieval	top-K, BM25, RRF-K, query expansion, HyDE, reranking, candidate pool	Immediate, per query	Admins only
KB	embedding model and backend, chunking, OCR, vector store, image indexing	Requires a re-index	Admins only

Protection levels

Every preset carries a level that decides who may overwrite it. Levels are shown in the dropdown as a prefix.

Level	Prefix	Who may overwrite
0	`★`	its owner — the admin for shared presets, the user for personal ones
1	`·`	admins only; users saving over one get an error
2	`◆`	nobody, admins included

Level 2 exists for settings that must never change. No shipped preset uses it.

Seeded presets live in backend/src/lancy/seeds/presets.json and are inserted on startup if missing. Editing that file does not change a preset that already exists in the database — seeding uses INSERT OR IGNORE, so admin edits are never overwritten by a restart. The protection level is refreshed on every startup.

The `Default` retrieval preset

Default is the company-wide baseline. It is special in one way: switching knowledge base in the settings panel loads it, replacing the retrieval settings shown there. It is matched by that exact name. Switching knowledge base in the chat only selects it and changes no settings.

To change the Default preset:

Log in as admin and open Admin → Knowledge & RAG.
Adjust the retrieval settings.
Click the save icon next to the Retrieval preset dropdown, type Default, confirm.

The edit is stored globally, not against the KB you happened to have open. It keeps its · level.

A preset only changes what the panel shows. What every user's questions run with is what the admin last saved with the Save button at the bottom of the panel.

The same applies to Fast, Multi-Document and Quality: an admin saving under one of those names updates that shared preset for everyone.

What users can do

Users see the settings and presets read-only, in the settings panel of the Advanced Features page. They cannot save settings: POST /api/v1/rag/config is admin-only, because a settings save rebuilds the agents everyone answers with. Every user's questions run with the settings the admin saved.

Retrieval settings users saved in earlier versions are still in user_config.db but no longer applied.

Known rough edges

Saving a preset reports success without waiting for the server to confirm, so an unrelated failure (network, permissions) can still show a success toast. Tracked in BACKLOG.md.
There are two save controls in the panel — the disk icon saves a preset, the Apply button at the bottom pushes the current state to the server. They do different things; see DESIGN_DOC_Admin_Role_Separation.md for the planned clean-up.