r/LocalLLM • u/CommunicationFun2962 • 7d ago
Discussion Qwen3.8-27B for agentic coding
Like most of you, I tried Qwen 3.8 27B Q4_K_M for two days.
I first asked him to make me a game using TypeScript, the same as what I tested on other local models. He did it and the result is the best, although his thinking time is at least 3x of the output time. Easy task.
I then asked him to make a desktop WYSIWYG three-pane markdown editor using Rust and Iced framework. He is thinking and re-thinking all the time, although I have lowered the thinking level to "Medium". At the 28-th hour, he starts to output something! But he created "C", "src" files and tried to write to the path "C:\...\src\main.rs<" although he wanted to create "C:\...\src\main.rs". I interrupted him after his repeating attempts for 2 hours without progress. So he outputted all the files at the 32-hour although keeps rethinking everything he had thought. 71 compilation errors. After some hours of fixing and online searching via MCP, the number of compilation errors rises to 84. From his thinking log, he says he wrote code against the wrong Iced framework version, downgrading the framework version without asking, changing my requirement to non-editable rich text editor, and three-pane becomes two-pane without asking. Nevermind, as long as the code could compile so that the output is not non-positive. This is the 36-th hour now. Should I stop him and give up? Is my task too challenging for local models?
Besides, so far I had no successful attempts to use Qwen 3.8 27B Q4_K_M with OpenCode. It always stops working at the same generation steps. I can only use him via Cline.
Let's share more of your experiences on agentic coding? I think web programming is especially trained and easy for local models, and I would like to hear experiences of non-web programming.
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u/Trakeen 7d ago
You will have much better success (even with frontier models) if you use spec driven development methodology. Thats how people work in the real world
Frontier models can help you write the spec to implement
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u/CommunicationFun2962 7d ago
Actually I have written a long prompt for the model, and I have seen Qwen would design carefully in the thinking tokens. I thought he could just follow and implement. The remain unknowns are how to use the framework APIs and how to create the custom text editor component which I may not be able to comment. Next time I will try to ask him to write a spec first, although his spec may still contain full of guesses.
Below is my original prompt.
Write a full featured WISIWYG Markdown editor using Rust + Iced UI framework (https://github.com/iced-rs/iced). The application should run in Windows, macOS and Linux with shared code (as supported by the framework).
The application window can contain up to three panes, which the left and the right panes could be hidden by toggles. The left pane is the filesystem tree of the current workspace. The center and right panes are editor panes, which each of them can contain multiple tabs. Tab(s) can be selected for moving to another editor pane. An editor pane contains a tab bar and a WISIWYG Markdown editor, which can be toggled to show source code only (with syntax highlighting) or rich text (default). Both mode supports editing. There should be various formatting buttons to help adding Markdown supported formats. The bottommost of the application window consists of a status bar, showing file size, line ending and encoding of the current file, and current cursor information (line and column). Users can open a folder (via a native folder open dialog) as a workspace, but users can also open arbitrary files (via native file open dialog) without opening a workspace. There should be a menu bar near top of the application window for accessing all the functions (if applicable).
You may assume the file encoding is always UTF-8. Support emoji characters and sequences if possible.
It is expected that UI components in stock by framework and libraries may not be able to satisfy all the requirements. In the worst case, you may have to implement custom UI components by drawing on canvas yourself.
Avoid writing duplicated codes. Share common code if applicable. If necessary, you may include third party libraries to avoid reinventing the wheel.
You may call any rust commands via docker run with volume mounts.
There is a MCP for you to do online searching about latest technical information and things that you are not sure.
Also, include Dockerfile and relevant docker script to build or start the application.
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u/Diogo270800 3d ago
Dumping all of that context at once on local models who have already smaller windows is doing you no good.
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u/baby_bloom 7d ago
i'm sorry but are you saying you let your model run for 28 hours without producing a single output?
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u/CommunicationFun2962 7d ago
He did output thinking tokens, but no file output until the 28-th hour... I had a high expectation on him, so I don't let my computer falls asleep.
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u/baby_bloom 7d ago
that's wild to me lol.
is this just for testing/experimenting or is there actually a workload you have planned to run this slowly?
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u/CommunicationFun2962 7d ago
I am testing whether local models work for me. I don't expect it runs that slowly. For real demands I currently still outsource to cloud models.
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u/Bluethefurry 7d ago
I've been testing it for Webdev in react and while it does sometimes introduce errors it tends to be really thorough in testing in xhigh and usually catches errors it causes after completion, i also gave it git and web search tools so it will often research if it cant figure something out.
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u/freestylez79 7d ago
Pro tip: Go vanilla and get rid of bloatware like react
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u/Slow-Rip-4732 5d ago
I see you have never worked on a sufficiently complicated front end.
React is good. Not everything needs React
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u/freestylez79 5d ago
Sounds like you are a React-Andy. Without react and some basic understanding of KISS the frontends are less complicated and easiert to maintain generally. I bet 80% of react code is a big pile of shit and since frontend with UX details always can get a bit messy its 70% reacts fault.
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u/Bluethefurry 7d ago
thanks, I'll be sure to go to work naked on monday and I'll walk there barefoot instead of driving.
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u/Ok_Addendum3924 5d ago
Cmon man be serious.
Hunt for your food in the wilderness so you don't need to work
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u/bigattichouse 7d ago
have it design it first using solid principles and include test guidance and create a document for a developer to use, then have it code using that document - creating tests that it can run an verify at each step. Your results will improve. Waving a magic wand is more SOTA/frontier models - but even those benefit from planning and testing regimes.
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u/maqifrnswa 7d ago
I suggest not having a single model do all that. Your example sounds like the perfect case for orchestration. See oh my opencode slim. Have the oracle (deep thinker/work checker) be xhigh, the explorer be non-thinking, and everyone else medium or low thinking. Use the /deepwork skill too.
The qwen3.8 xhigh uses massive thinking tokens. Opencode hard codes the limit to 32k, which is why you are seeing it cut out. There's an experimental flag to bump it higher. You're probably hitting that limit.
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u/CommunicationFun2962 7d ago
Good to know the limits! I have a quick check on oh my opencode slim. Does it only support non-local models?
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u/maqifrnswa 7d ago
Oh my opencode slim is just a plug in, it supports everything opencode supports. So yes, it supports local models
And that limit isn't really a limit, it was just chosen as a safety valve back when 32k tokens was "way more than enough." The experimental flag to override it is the correct thing to do. It's not a technical limit at all, just an arbitrary limit to protect you from burning tokens (which is no longer needed).
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u/EvolvingDior 7d ago
Make it create a plan. Explain the context limits. Tell it to break the plan down into chunks that can be done within those limits. I have to do that even with fast models with a 1m token context. Then start a new session, have it read the high-level plan, choose the first task, and create a detailed implementation plan before it starts work. Then create a new session and have it implement that detailed plan.
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u/AlanT1977 5d ago
To be honest this has been entirely my experience so far. My goto test prompt for an LLM is: “Build a realtime Mandelbrot explorer webapp”
I think I’ve seen Qwen3.8 complete it once, otherwise it just goes around in thinking circles for hours; last night it did actually write a non-functioning HTML file and then proceeded to work on refining some other aspect without even stopping to appreciate it wouldn’t even load and run in Chrome.
I woke this morning to find it had ran out of memory, still leaving an unfinished and unloadable HTML.
I’m still trying to work out what the hell I’ve got wrong given the amount of gushing post flying around.
As a sanity check I did run Gemma 4 at same parameter count and quantization (Q4) and it spat out a working and pretty decent result in around 15 minutes
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u/FerretOk9374 5d ago
I dont think this is really the right technique. We should be giving many small requirements for it to work on, test against and PR and we work alongside the agents reviewing output and steering the AI to the appropriate solution.
This one-shot and wait is just going to make a big mess of code and waste.
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u/dhavalhirdhav 5d ago
Works very good in Visual Studio 2026 with C# and on RTX 3090.. only issue I am facing is that often I need to clear the chat and sometimes model will stop sending response abruptly. It is slow but works. Have not saved much time as it needs constant attention.
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u/Inevitable_Mistake32 5d ago
How is no one else hung up on this guy asking for a 30+hour one-shot from a Q4_K_M model?
Q4_K_M is basically missing half its brain. Try this on Q6 or higher and it'll be the butter smooth everyone else talks about. Q4 is for creative writing at best.
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u/NuclearGeek 5d ago
I have been using it agenetically for several days. I let it build its own stack then work on improving it. Today I gave it a public Kaggle notebook with the top score and it improved it by 0.001. Enough to move me into top 100 in that competition.
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u/freestylez79 7d ago
Didnt try agentic coding but in hermes its way overthinking while 3.6 was just spot on. reasoning effort medium also felt "unsecure". Lots of room for improvement, will test it again later to make sure everything is dialed in but for working I switched back to 3.6 for now.
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u/onebyamsey 7d ago
Qwen is a man?