Only put streams onto isolation-compatible circuits
This is the meat of Proposal 171 (#1865 (moved)): Once we have the code to tell Tor how to isolate streams (#3515 (moved)), and once we have the logic to decide how to treat isolated streams (#3516 (moved)), we can actually hook everything up so that streams never get attached to circuits with other incompatible streams.
To upload designs, you'll need to enable LFS and have an admin enable hashed storage. More information