ComfyUI MiniMax H3 SPEED V2: Multi-Sampler Progressive Resolution

Same seed and prompt, 960x544 at 24 fps, 10.125s. Left: full-resolution baseline, no SPEED (571.49s). Middle: 3-stage at delta 0.005 (438.85s). Right: 4-stage at delta 0.05 (237.57s).

How SPEED splits the schedule

MiniMax H3 pays full spatial cost on every denoising step, including the early ones where the latent is dominated by noise and no high-frequency detail exists yet. SPEED moves those steps down to a smaller grid and works back up: the sampler denoises at a fraction of the target resolution, then transitions the latent to a larger grid for the remaining steps.

The node ships three automatic ladders, selected by a single stages value:

Tolerance (Delta), noise_amplitude and noise_decay_exponent decide when each transition happens; the shipped defaults come from the author's own calibration fit, and the README recommends leaving them alone unless you are running a Harvest calibration. The high-frequency bands exposed by a resolution increase are filled from a deterministic, transition-seeded Gaussian field under the default direct_coarse noise policy. A second policy, coupled_full_grid, derives those bands from a single full-resolution noise field instead; the author has not confirmed it improves quality and it is not the default.

SPEED applies to MiniMax H3 only, and H3's audio stream always stays at full resolution.

What changed in V2

The repository's CHANGELOG.md lists this as 2.0.0. The substantive changes:

• Sampler support. SPEED is no longer tied to Euler. V2 accepts Euler, Heun, DPM2, Exp Heun 2 X0 and RES Multistep. The stateless samplers use ComfyUI's own sampler objects; RES Multistep keeps previous-step history, so V2 runs it through a run-scoped adapter and clears that state whenever SPEED changes resolution, rather than carrying history into a differently-sized latent.
• Sampler-aware Sigma Harvest. The calibration node now reports parameters for the sampler you actually selected instead of assuming Euler, and it defaults to the same 0.005 tolerance as the automatic path.
• Unified planning. Automatic and Manual share one planning and validation implementation. Automatic now calculates transitions from the live sigma schedule and the current latent dimensions.
• I2V keyframe fix. Keyframe latents are resized from their original full-resolution copy instead of resizing an already resized tensor, and they are restored before the final stage and after a failed run. The author's summary: image-to-video should no longer get progressively blurrier at each resolution change.
• Leaner Harvest memory. V1 held every full-resolution residual tensor until the run finished and analysed them afterwards. V2 reduces each residual to a small radial DCT power profile inside the callback and discards the tensor.
• Continuous progress and previews. A SPEED run now reports as one generation instead of several unrelated sampler calls.
• Regression coverage was widened across sampler selection, RES state, I2V, transitions, Harvest, workflows and noise policies.

Measured speedups

The repository publishes an evidence folder with timings behind the claims: one RTX 5080 with 128GB of system RAM, 960x544 output at 24 fps for 10.125 seconds, same seed and prompt across every row. The full-resolution Euler baseline is 571.49s.

The same folder states the limits of those numbers plainly. They are an Euler-only reference set: they do not establish speed or quality parity for the four samplers V2 added, and they should not be read as proof that one noise policy beats another. The author's instruction is to re-run the Harvest calibration and benchmark your own sampler, model and scheduler combination.

The three nodes

Installation is a clone of the package into ComfyUI/custom_nodes/ and a restart. In a workflow, replace SamplerCustomAdvanced with the SPEED sampler node and connect the same noise, guider, sigmas and latent_image inputs; an all-in-one KSampler has to be split into ComfyUI's advanced sampling components first.

Workflows

The repository ships three frontend-format workflows. The calculated variant runs Sigma Harvest inside the graph so the calibration values arrive automatically; the manual variant exposes the ladder for hand-tuning.

The calculated workflow wraps an image-to-video H3 graph in a subgraph and sets the SPEED sampler to stages = 3, direct_coarse, delta = 0.005, noise_amplitude = 12.105, noise_decay_exponent = 0.773, seed_offset = 10000 and sampler = euler. Its notes point at the pruned int8 convrot fl2va checkpoint, the nvfp4 Qwen3-VL 32B text encoder and H3's separate video and audio VAEs.

Availability

• Node pack: StanLukuvka/ComfyUI-MiniMax-H3-SPEED
• Workflows: workflows/
• Benchmarks and comparison clips: evidence/
• Changelog: CHANGELOG.md

The repository had collected 85 stars when this was written. The announcement thread ran in r/comfyui, and much of the discussion asked for side-by-side output rather than the timing table; the author pointed readers at the evidence folder and at a separate third-party speed comparison. No independent reproduction of the V2 sampler set had been published at the time of writing.