Chroma¶

Chroma locks a collection's dimension when it is created. Changing embedding model there means creating a new collection and re-adding everything — which is precisely the situation rebasis exists for.

pip install "rebasis[chroma]"

URI¶

chroma:///absolute/path/to/db#collection_name

The collection name after # is required. Without it rebasis cannot know which collection you mean, and guessing would be worse than asking.

Probe¶

rebasis probe \
  --store chroma:///Users/me/vault/chroma#notes \
  --old sentence-transformers/all-MiniLM-L6-v2 \
  --new BAAI/bge-base-en-v1.5 \
  --report report.html

Reads only. The collection is not modified, and the command works against a read-only filesystem.

What Chroma supports¶

Capability	Supported
Read vectors	yes
Read text	yes
Upsert vectors	yes
Metadata filter	yes
Dimension locked	yes
In-place update	yes

The locked dimension is the important row. If your new model has a different dimension, migration cannot write the new vectors into the existing collection — bridging is the path, and rebasis will tell you so before it starts rather than halfway through.

If the collection is not found¶

RB-E3003  Chroma has no collection named 'note'.
          Available: notes, archive, drafts.

rebasis lists what is actually there. A collection name typo is the first thing a new user gets wrong, so the error is written to fix itself.