Re: HEADSUP: all MirageOS unikernel compilations are broken right now

[Hannes Mehnert <hannes@xxxxxxxxxxx>]

A workaround awaits to be merged at 
https://github.com/ocaml/opam-repository/pull/29219 - which adds a 
conflicts to mirage-runtime with lwt 6.0.0.
It would be great to have this merged rather sooner than later. At the 
same time, this can be reverted once the issue in dune is resolved.

Best,

Hannes

On 12/01/2026 20:15, Hannes Mehnert wrote:
> Dear everyone,
>
> first of all: Happy New Year! :)
>
> since lwt 6.0.0 came into existance, unfortunately all MirageOS 
> unikernel compilations (for any target apart from unix) are broken.
> The issue is that lwt now uses
> ```
>   (libraries
>   (select lwt_rte.ml from
>    (lwt_runtime_events -> lwt_rte.with.ml)
>    (-> lwt_rte.without.ml))))
> ```
>
> Which interacts badly with dune / solo5 cross-compilation. I opened an 
> issue at the dune issue tracker https://github.com/ocaml/dune/issues/13299
> Any help is appreciated. I've no experience with dune, and do not 
> understand how MirageOS unikernels are compiled (when typing `make 
> build`) well enough.
>
> We, well, Reynir, discovered that while working on DNSvizor https:// 
> github.com/robur-coop/dnsvizor/pull/116
> Best,
>
> Hannes