A single node — Flux Detail Guidance (FDG) — that adds natural micro-detail to a Flux.1 refine without raising denoise and without changing composition or text.

It's a Flux port of the "token detail guidance" self-guidance idea. Crucially, it's a per-forward-pass MODEL patch, so unlike full-image inversion/upscalers it runs inside tiled samplers (Ultimate SD Upscale, etc.) at 3K-4K. Pairs naturally with a clean solver such as seeds_3 at eta=0 (ComfyUI-SEEDS3Sampler).

How it works

During a chosen window of the denoise schedule, each step runs the model twice:

eps_full = model(x)                  # normal
eps_weak = model(x) with the image-token high-frequency detail attenuated
                                     # in a selected band of Flux double-blocks
delta    = eps_full - eps_weak       # = the detail the model was adding
eps      = eps_full + scale * shaped(delta)

shaped() splits the delta into mid/high frequency bands (weighting high-freq more in late steps), gates the hardest edges to avoid outline halos, and std-limits it, so you get texture/detail back without color drift or crunchy edges. An output_rescale stabilizer blends the result back toward the normal pass.

Cost: ~2x model evaluations during the active window only.

Install

cd ComfyUI/custom_nodes
git clone https://github.com/lookuters22/ComfyUI-FluxDetailGuidance

Restart ComfyUI. Node appears under Flux/experimental.

Wiring (refiner)

UNETLoader -> (LoRAs) -> ModelSamplingFlux -> Flux Detail Guidance -> UltimateSDUpscaleCustomSample

Use a clean sampler (e.g. SEEDS-3 Sampler eta=0) and the ays scheduler.

Parameters

Param	Default	Notes
`double_start` / `double_end`	10 / 19	Double-block band to weaken (Flux-dev has 19). Set `end <= start` to disable.
`single_start` / `single_end`	15 / 38	Single-block band to weaken (Flux-dev has 38 — most of the detail lives here). Set `end <= start` to disable.
`step_start` / `step_end`	0.0 / 1.0	Active window as a fraction of the executed steps. At low denoise (e.g. 0.3) the executed steps are already the tail, so keep `step_start` near 0.
`guidance_scale`	0.35	Detail strength. Main dial. Start 0.3-0.6 and raise until it looks crunchy.
`weaken_strength`	0.5	How hard the weak pass suppresses detail per block (bigger delta = more effect).
`blur_passes`	1	Defines the "detail" scale (high-freq residual). 1 = finest.
`output_rescale`	0.3	Stabilizer toward the normal-pass statistics. Lower = more raw detail.
`adaptive_gate`	True	Only weaken where local detail energy is high; keeps flat areas clean.

Tuning: not enough detail -> raise guidance_scale, widen the single-block band, or lower output_rescale. Halos / crunch / "flat contrasty default-Flux look" -> lower guidance_scale, narrow the band, and avoid weakening the early blocks (keep the bands in the back half of each stack so the weak pass stays a detail-starved model, not a broken one).

Notes / limitations

Flux only. Requires .model.diffusion_model.double_blocks + single_blocks; it refuses to patch non-Flux models. (Z-Image / SD / SDXL are different architectures.)
Patches both double-blocks (pure image stream) and single-blocks (image tokens sliced out of the [txt ; img] sequence via transformer_options["img_slice"]).
If a step's image-token count doesn't match a plain grid (e.g. Kontext/reference latents add tokens), the weak attenuation safely no-ops for that pass.
Cost: ~2x model evaluations during the active window only.

License

MIT. No ComfyUI source is copied; only public model-patcher APIs are used.