ADR-004: Collection Model Resolution

Status: accepted Date: 2026-04-06 Author: Gordon Mickel

Context

GNO already has a global preset system for embedding, reranking, expansion, and answer generation.

That works well for most users, but some workspaces need one collection to use a different retrieval stack than the rest:

  • code-heavy docs vs prose-heavy docs
  • local CPU-friendly defaults vs a heavier collection
  • incremental experimentation without replacing the whole active preset

The project should support that without forcing users to duplicate an entire preset for one collection or inventing a second config file format.

Decision

Add optional collection-scoped model overrides inside the existing central config file.

Resolution order:

  1. collection role override
  2. active preset role
  3. built-in default fallback

Overrides are partial by role. A collection can override only rerank, for example, while inheriting embed, expand, and gen from the active preset.

Consequences

Positive

  • collection-specific retrieval tuning without replacing the whole preset system
  • less duplication than creating per-collection presets
  • clearer mental model than adding config files inside collection roots

Negative

  • model resolution is no longer purely “active preset only”
  • collection-aware operations must pass the collection name into model resolution explicitly
  • cross-collection operations still need careful handling when multiple collections could imply different model choices

Notes

  • This ADR covers model resolution only.
  • It does not imply per-collection chunking strategy, per-collection runtime shells, or per-folder config files.