I get MT and non-MT workunits on my PC.
The setting is max. 8 Threads per WU.

I want to have max. 1 MT WU running at the same time and up to 12 WUs (incl. non-MT over all).

Is this possible via app_config.xml ?

I tried this way:

app_config>

<app_version>
  <app_name>milkyway_nbody</app_name>
  <plan_class>mt</plan_class>
  <cmdline>--nthreads 8</cmdline>
  <avg_ncpus>8</avg_ncpus>
  <max_concurrent>1</max_concurrent>
</app_version>

<app_version>
  <app_name>milkyway_nbody_orbit_fitting</app_name>
  <max_concurrent>11</max_concurrent>
</app_version>

<project_max_concurrent>12</project_max_concurrent>

</app_config>

But it seems that both apps are called "milkyway_nbody" :

So 08 Feb 2026 10:32:27 CET | Milkyway@home | Your app_config.xml file refers to an unknown application 'milkyway_nbody_orbit_fitting'. Known applications: 'milkyway_nbody'

For me this means I can only set globally max 1 WU and if this is a non-MT, then only one thread is working for Milkyway.

So 08 Feb 2026 10:32:27 CET | Milkyway@home | Your app_config.xml file refers to an unknown application 'milkyway_nbody_orbit_fitting'. Known applications: 'milkyway_nbody'

This message means, that your computer didn't receive any WUs for the milkyway_nbody_orbit_fitting application since you attached it to the project or since you have reset the project last time. The name is correct, it will disappear once you get a WU for that application. However there are MT and non-MT versions for both, milkyway_nbody and milkyway_nbody_orbit_fitting, so doing this via app_config.xml requires that you specify your wishes for both, however you can't stop BOINC from running one MT WU for each application, so 2x MT would be the minimum and if you don't get enough single thread WUs from the server, you might end up with idle cores unless you also run other projects than Milkyway. I can write an app_config.xml, which will get the BOINC client to try to do what you asked for, but it won't always work as expected since your BOINC client won't always have the WUs to do it exactly that way, so perhaps you can describe in more detail what you actually try to achive (how many total threads you want to use for BOINC, do you run other projects, etc.) and we might find a better solution.

In general, running Milkyway N-Body in MT-mode seems to be by far more efficient, so I'd recommend to eliminate the single thread WUs completely by setting "Max # of threads for each MilkyWay@home task" in your MilkyWay@home preferences to the desired amount of threads instead of "No limit" and remove the app_config.xml file completely unless you want to use it for something more than specifying the amount of threads.

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OK, lets ignore the orbit fitting.

If it is not possible to separate the MT and non-MT demands in the app_config, then I just want to avoid getting the non-MT WUs.

Max # of threads for each MilkyWay@home task = 8
is already set.

So I just need to remove the app_config and will get no single-Thread WUs any more?

Yes, but you need at least to reset the project (or remove it completely and than attach again). Removing app_config might not be enough to reset everything.

EDIT: I don't know why, but the server has send me 3 single thread WUs when v1.94 was released, one I crunched, the other two I aborted and since than never got any. Just so you know in case this happens to you after the reset.

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Yes, but you need at least to reset the project

Then I will keep the app_config for the moment and just delete all the single-WUs.