External delay differential equation solver

Is it possible to use external DDE solver (user defined) function for fitting parameters to the model.
As I know Stan doesn’t provide DDE solver. Do you have any idea?

Julia’s Turing.jl can use any of the DifferentialEquations.jl solvers which includes DDEs. I would like to add this to Stan as well by having Stan call the Julia DiffEq libraries, but currently Stan is missing an FFI (https://discourse.mc-stan.org/t/foreign-function-interface-in-stans-future/) which would be required to do this (but I’m continuing to watch this space and see how it evolves!)