Based on the knowledge sources available, the record_sessions_percent option is described as: "Percentage of SDK initializations that will qualify for replay data capture. A value of '1' = 1%." [Init Options]
The documentation does not explicitly state whether decimal values (e.g., 0.5) are supported for this parameter. Since you've already tested it and found it doesn't appear to work with decimals, this aligns with the fact that the docs only reference whole number examples.
The knowledge sources do not contain enough information to confirm or deny decimal support for record_sessions_percent on the web SDK. I'd recommend reaching out to Mixpanel Support directly to clarify whether sub-1% decimal values are supported, or to request that feature if it isn't.
As a potential workaround in the meantime, you could use the manual capture approach — keeping record_sessions_percent at 0 and programmatically calling mixpanel.start_session_recording() only for a fraction of users based on your own sampling logic in your application code. [Capturing Replays]
