Great to see this. I played around with jj about two months ago and really enjoyed using it on the command line, but I found it difficult to understand the interaction with git and GitHub and decided to put it off until I had more time. (I don’t recall the specific issues I had…) Maybe this extension can remove some of that friction.
jjk caused a lot of problems for me when using multiple agents. It's running some sort of jj command that snap-shotted stuff and caused divergence (might have benefited from `--ignore-working-copy`). Not sure what the precise details were, but I gave up and uninstalled it after a week.
It does look nice, I'll give it a go. Just wanted to say that "Git-out-of-the-way source control" is the best tiny description of JJ I've ever seen, because it's both true and the pun works perfectly. It brought me joy.
It uses it when you use the git backend, but not when you don’t.
Right now, the only other backend is at Google, so it’s not practical for most people. But it’s not an inherent part of jj, and that’s really important, actually.
I worked with JJ for half a year, and it was great. However, I've since decided to go back to GIT because of compatibility with existing workflows and AI tools.
Pre-commit hooks are not possible [yet?], which is a minor inconvenience. Worse, workspaces/worktrees use a different mechanism. This causes like Claude Desktop (which uses worktrees) to break. Also Claude and other agents are always confused about JJ and fall back to git too often.
Seeing similar comments across different articles and technologies and it makes me wonder how much AI is going to hold back the adoption of new technologies going forward.
I find it a bit ridiculous to see that people or whole teams don't want to use JJ (or any tool, for that matter) because in essence they hired a "support intern" (read: AI assistant) who doesn't know or want to use it.
I noticed it get a lot better with the 4.5 models specifically. Before then, I would have to tell Claude "do a web search for the docs for jj, then do XYZ." Now I just tell it to "do XYZ using jj"
Even breaking changes in a library can cause massive pain. AI constantly wants to the use the old pattern it was trained on. Up until a few months ago it would always prefer using the 2021 edition of rust rather than 2024 for instance. Overall though I don't think this is insurmountable, but it definitely adds an impediment which will overall motivate people to do things non optimally for the foreseeable future. Luckily, not everyone is bound by AI today. I just write my own commits messages instead of letting the AI do it. jj is popular enough that I'm sure it'll learn how to use it in the next year (especially Gemini because Google is using jj internally and would probably train it on it as a result)
I agree it will hold back new technologies, but, at the same time, I'm not sure what the value add of new technologies will be going forward. Often, as is the case with git vs. jj, the value add of a new technology is mostly ergonomic. As AI becomes more ingrained in the development flow, engineers won't engage with the underlying tech directly, and so ergonomic benefits will be diminished. New technologies that emerge will need to provide benefits to AI-agents, not to engineers. Should such a technology emerge, agent developers will likely adopt it.
For this reason, programming languages, at least how we understand them today, have reached a terminal state. I could easily make a new language now, especially with the help of Claude Code et al, but there would never be any reason for any other engineer to use it.
Even if you're not authoring changes as much, change management is likely still to be a very useful activity for a long while. Also note that not everyone is using AI today, and many that do only use it as glorified auto complete. It will take many more years for it's adoption to put us in a situation like your describing, why halt progress in the meantime? My personal productivity increased greatly by switching to jj, perhaps more than adding Gemini CLI to my workflow. I can more confidently work on several changes in parallel while waiting on things like code review. This was possible before but rebasing it and dealing with merge conflicts tended to limit me from doing it beyond a handful of commits. Now I can have 20+ outstanding commits (largely with no interdependencies) and not feel like I'm paying much management overhead while doing so. I can also get them reviewed in parallel more easily.
Ah yes, the inevitable future where the only way we'll know to interact with the machine is through persuading a capricious LLM. We'll spend our days reciting litanies to the machine spirits like in 40k.
Praise and glory be to the Agentic gods. Accept this markdown file and bless this wretched body of flesh and bone with the light of working code. Long live the OpenssAIah
Pre commit hooks are complicated because jj just has a fundamentally different lifecycle than git does.
Tools that integrate with git specifically can be tough though, yeah. Some do Just Work, and some very much do not.
I’ve found a “we use jj not git for this project” in Claude.md makes falling back to git rare, but I also tend to incorporate version control into slash commands or skills directly rather than let Claude decide what to do.
I also prefer to manage version management myself directly, even with llm-gen'd CICD elements, so preferring jj hasn't been nearly as costly for me specifically :D
My team is asking the same. We are using jj with great success but tools like auto claude are designed around git and git worktrees. It's a shame - at least with git backend we can sort of make things work together.
I agree about hooks and workspaces, but I'm surprised your Claude is having issues with jj itself. jj is definitely in the training data now, so it might be a matter of guiding it with CLAUDE.md.
It usually works, but sometimes it'll try to use git instead of jj at random and needs a reminder. As JJ is not completely stable it tries some old commandline versions as well. This improved after I put in some lines in my agents file, but still it's much better at complex changes with git than jj.
If it helps, this was all I needed in my CLAUDE.md to make it use jj perfectly:
# Version Control
- IMPORTANT: YOU MUST assume we use Jujutsu ("jj") for version control. Check by running `jj root` (or look for a `.jj/` directory) to confirm.
- If I say "commit", "branch", "squash", etc., assume jj equivalents first.
- You can ignore any `git add` command, since jj always auto-adds.
- Use `jj` commands instead of `git`. Never run `git` in a jj repository.
- ALWAYS prefer jj change IDs over commit SHAs. jj change IDs are stable.
- jj doesn't usually require named branches
- If you need named branches, use `jj bookmark`, but you must manually update the bookmark after making new commits, since they won't automatically get updated
- When reading data from jj, always use `--ignore-working-copy` to avoid snapshotting the working copy (which is slow and unnecessary for read operations). But when writing (commit, squash, rebase, etc.), you MUST NOT use `--ignore-working-copy`.
- If you get "Error: The working copy is stale", run `jj workspace update-stale` first
> Stay in your editor while GitHub does the rest. VisualJJ tracks pull-request status on the change tree and lets you create PRs in a couple of clicks, so moving changes from “draft” to “merged on GitHub” feels like one smooth flow.
I love jjui, but I feel like it's also the reason I still use him over vscode. If you already use vscode, doesn't using a vscode extension make more sense?
Of course there are some people that will want a gui not matter what. Then an extension or separate program is the only thing you can do. But i think it is really nice to have the same tool available everywhere, also in the terminal. And if you want a neat and vertical pane in vscode just drag a new terminal window next to your code and run jjui in it.
One obvious case where magit isn’t useful as opposed to jj is if you’re not an emacs user.
jj has some additional features over just a nicer UI that I believe magit can’t do, but given that I haven’t used magit yet I am not 100% sure of how that comparison is exactly.
Right now, the only other backend is at Google, so it’s not practical for most people. But it’s not an inherent part of jj, and that’s really important, actually.
Pre-commit hooks are not possible [yet?], which is a minor inconvenience. Worse, workspaces/worktrees use a different mechanism. This causes like Claude Desktop (which uses worktrees) to break. Also Claude and other agents are always confused about JJ and fall back to git too often.
You're right in principle, but it just seems JJ is a solution in search of a problem.
For this reason, programming languages, at least how we understand them today, have reached a terminal state. I could easily make a new language now, especially with the help of Claude Code et al, but there would never be any reason for any other engineer to use it.
Tools that integrate with git specifically can be tough though, yeah. Some do Just Work, and some very much do not.
I’ve found a “we use jj not git for this project” in Claude.md makes falling back to git rare, but I also tend to incorporate version control into slash commands or skills directly rather than let Claude decide what to do.
Does it support stacking PRs?
EDIT: I should have looked more closely, looks like it does, though only in the Pro version: https://www.visualjj.com/docs/stacking
Can't be easy to build a GUI on top, but I'm sure a 10% revenue to be redistributed to the hero behind jj would go a long way. Would also pay off.
I feel like git is just easy-mode with magit and I don't really miss a whole lot more. I totally get this is you are using the git cli or some such.
Might just be my limited imagination though of course.
jj has some additional features over just a nicer UI that I believe magit can’t do, but given that I haven’t used magit yet I am not 100% sure of how that comparison is exactly.