[Bug] sample_params broken/frozen? (Z-Turbo)

[SolicTous]

Git commit

6b3edaa

Operating System & Version

win 10

GGML backends

CUDA

Command-line arguments used

"../sd-server.exe" -v --listen-ip 0.0.0.0 --diffusion-model ../../Models/Diffusers/Transformer/Z-Image/z_image_turbo-Q4_0.gguf --vae ../../Models/Diffusers/Vae/pig_flux_vae_fp32-f16.gguf --llm ../../Models/Diffusers/LLM/Qwen/Qwen3-4B-Instruct-2507-Q8_0.gguf --diffusion-fa --cfg-scale 1.0 --steps 8 --vae-tiling --vae-tile-overlap 0.125 -H 1024 -W 1024

Steps to reproduce

Just generate image via sdcpp/v1/img_gen endpoint with json like this

    json={
        "prompt": prompts[key],
        "sample_params": {
            "guidance": {
                "txt_cfg": cfg,
            },
            "sample_method": sampler,
            "sample_steps": st,
            "scheduler": scheduler,
        },
        "width": sz,
        "height": sz,
        "seed": 1
    }
)

What you expected to happen

Different images after change sampler or scheduler
Not sure, but I see difference in old scan https://drive.google.com/file/d/1tf277KI4SabVTLB15pZrlv2eQaCJyTSB/view?usp=sharing

What actually happened

All images SAME, differs only for lcm, but all other is same, like it's ignoring settings.
https://drive.google.com/file/d/1cD3OeiMenDyTRgycVXfr399tPMQYAfRa/view?usp=sharing

Logs / error messages / stack trace

In logs I see that sampler is changed.

Additional context / environment details

No response

[SolicTous]

Additional info: I just tried to analyze samplers and schedulers using some metrics and was surprised to find that the images have the exact same values. That really shouldn't be the case.