Image input not working?
It works for me with Koboldcpp, with Q8 or Q6 quants and I used the BF16 mmproj file. I do not know how llama.cpp works directly, do you have mmproj file loaded?
image input also not working for me. I'm using Q5 version on llama.cpp
Reasoning doesn't work for me with this model. It does with the official original gemma-4.
Reasoning works well with all I tried - Q8 and Q6 from here and Q4KL from bartowski (Koboldcpp + SillyTavern + text completion with my template). But you need to have correct template, which is bit complex with this model. There were initial problems in llamacpp though with BOS token etc, so that could be issue too. Good system prompt helps as well to instruct what it should actually reason about. I did not try <4bpw quants though but <4bpw reasoning models never worked well for me in the past anyway.
Make sure that beside channel/thought tokens you also have <|think|> token at the beginning of first system prompt, otherwise it might refuse to reason despite everything else set correctly.
Reasoning works with google/gemma-4-31b, but not with unsloth/gemma-4-31b-it.
Shouldn't they both require the same settings?
In LM Studio google/gemma-4-31b is shown as having reasoning capabilities, but unsloth/gemma-4-31b-it doesn't. unsloth/gemma-4-31b-it also doesn't think when I use it. (Every model can do the fake think in Silly btw. It's really more like taking notes.)
Edit: I had to do this to enable think https://huggingface.co/unsloth/gemma-4-26B-A4B-it-GGUF/discussions/6
I don't use LM studio so can't help there. Just for reference - Q8, Q6, and I think I also tried Q5KM from this repository - they all worked well with reasoning reliably. So when they don't work, it is probably wrong setup/prompt. Can't say about other quants from this repo as I did not try those.
Also, google/gemma-4-31b (without -it) is base model as far as I see. It should not even use any instruct templates, it is just text competition model/ model for further post-training. I am surprised if that even worked for you somehow. google/gemma-4-31b-it is the instruct model and this repo is quant from that. The -it version is the one you should use, unless you know what you are doing (eg you want base model for some reason).

