Lane splitting — riding between lanes of slower or stopped traffic — is legal in California, so doing it does not by itself make a crash your fault. Insurers sometimes argue otherwise, but the legality of lane splitting means fault is judged the same way as in any crash.
That does not mean lane splitting is never a factor. If the speed or spacing was unsafe, an insurer may argue the rider bears some share of fault. Under pure comparative fault, that would reduce recovery by the rider's share rather than eliminate the claim.
The other driver's conduct usually remains central — a lane change without looking, an opened door, or drifting within a lane. Showing that the rider was lawfully splitting and focusing on what the driver did wrong is how these claims are built.