It’s a bit strange, since because “this.project” is null is exactly the message you get if you use BndTools 7.1 from what I understand. Have you restarted Eclipse since the downgrade, and made sure that there are no remains of 7.1 anywhere in Eclipse?
I have tried on both 2025-03 and 2025-06, downloading to bndtools 7.0:
Adding mqtt binding to pom.xml in the demo project, then adding it to the app.bndrun:
Then when pressing Resolve:
I have restarted Eclipse, I have build both demo app and binding commandline successfuly, I have run Maven → Update project:
but nothing seems to solve it.
I have had Eclipse setup working for earlier OH versions (3 and 4), and debugged bindings w.o. issues many times before.
Yes, this is frustrating a lot of people, and I don’t quite understand why nothing is done about it.
I can’t explain why downgrading to 7.0 shouldn’t work, but I’ve heard others report the same. I can only assume that some bits or pieces of 7.1 are left behind somehow.
It’s worth a try to make an installation using the procedure I explained here, as it makes sure that 7.0 is installed from the beginning, without the downgrade later, which seems to have a better chance at avoiding this issue:
Note: “Expand” the post to see the full explanations with pictures.
I wanted to respond indicating that your setup worked for me, but the topic was closed 
Maybe a PR is worth the try?
It works!!! 
Thank you very much!
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I am trying to setup Eclipse on new Linux Mint. I uninstalled bndtools 7.1.0 and installed bndtools 7.0.0 but when I first try to resolve app.bndrun, I get this error:
This was already a nightmare to make it work on Windows 10 and now the nightmare is back for Linux Mint…
Try the file I’ve created that’s referenced a few posts above. It has solved the same issue for others… which reminds me that I should probably get that PR for distro made so that hopefully this won’t happen to everybody.
I just read your linked post, is it normal that I don’t see your screen captures ?
Yes, if you have a fix, please create a PR.
I am running a full build in case it could help.
I will try later your file, hoping that without the screen capture I can find where to enter this file.
Press the little “expand arrow” and you’ll see them.
edit: Sorry, right now the screenshots don’t work for me either. They used to work, so I don’t know what’s happening.
edit2: The screenshots are gone from the original post: Californium removed? - #78 by Nadahar. I don’t think I’ve kept them, so if the forum has deleted them, I’m afraid they are gone permanently.
edit3: It seems like all links in that post had been invalidated - even the link to the file itself. I really hope this is a temporary problem with the forum…
In “Plug-ins” tab, I still see traces of 7.1.0, could it be the problem ? How to remove them ?
while in “Installed Software” tab, I can see only 7.0.0:
That could be, and I don’t know.
Maybe you should uninstall BndTools completely from Eclipse first, and see if the traces go, before installing 7.0.0?
I will try.
Maybe I have to clean my .p2 folder also.
PR created:
I guess those that wish to get it merged should do their work behind the scenes 
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@Nadahar : selecting your file (after downloading it and renaming it) fails for me:
In fact, I am not able to download your txt file !!! The file I download is the HTML page of the forum !
Edit: The link is broken:
Can I use simply the file you updated in GitHub ?
Edit2: If I use the file from your GitHub PR, it does not work, the file does not contain a valid projet … apparently.
Yes
You must not select it on the “first page”, but on the second… except for that, it should work.
I can attach the file here too…
openHAB2.setup.txt (219.5 KB)
(rename to .setup instead of .setup.txt)
Are you sure that the setup process has the appropriate permissions to read the file?
File permissions look good.
Am I at the right place or not to provide this file ? You see my screen capture, I click on the green “+” icon at the top of this window where you have several icons. Is it correct ?
I moved the file in a different folder and now the error is different: project is already contained in the index.
It very much looks correct, yes.
I’ve had the same error you have in the past, and I just cannot remember what the cause was, but it was something really “stupid”. That’s why I asked about the permissions, I’m pretty sure it’s something banal like that. Another thing on the same level, the “extension” of the file is supposed to be .setup - make sure that it really is, and that the extension isn’t just hidden in the UI for example.
This error I haven’t seen, and frankly, don’t understand at all.