| # LTX-2.5 first-and-last-frame — the config that actually works |
|
|
| Extracted from `video_ltx2_5_flf2v fresg.json`, the workflow Radek confirmed |
| produces good output. Recorded because getting this wrong looks like a broken |
| model rather than a wrong preset. |
|
|
| ## The trap |
|
|
| There are **two LTX-2.5 transformers and they need opposite sampling regimes.** |
| Running one at the other's settings produces soft, washed-out, distorted frames |
| that read as a bad model or bad anchors. It is neither. |
|
|
| | | distilled (what the preset uses) | dev | |
| |---|---|---| |
| | transformer | `ltx-2.5-22b-distilled-transformer-comfy-int8-convrot` | `ltx-2.5-22b-dev-transformer-bf16` | |
| | text encoder | `gemma4-12b-with-proj-ltx-2.5-comfy-int8-convrot` | `gemma4-12b-with-proj-ltx-2.5-bf16` | |
| | steps | **8** | ~24 | |
| | guidance | `LTXVDualCFGGuider` at **1, 1** | CFG ~4 | |
| | sampler | `SamplerEulerAncestral` (eta 0, s_noise 1) | euler | |
| | sigmas | `ManualSigmas`, explicit 9-value list | `LTXVScheduler` | |
| |
| ## Verified working values |
| |
| ``` |
| UNETLoader ltx-2.5-22b-distilled-transformer-comfy-int8-convrot.safetensors, default |
| CLIPLoader gemma4-12b-with-proj-ltx-2.5-comfy-int8-convrot.safetensors, type=ltxv |
| VAELoader ltx-2.5-video-vae-bf16.safetensors (video) |
| VAELoader ltx-2.5-audio-vae-bf16.safetensors (audio) |
| ManualSigmas 1.0, 0.99375, 0.9875, 0.98125, 0.975, 0.909375, 0.725, 0.421875, 0.0 |
| SamplerEulerAncestral eta 0, s_noise 1 |
| LTXVDualCFGGuider 1, 1 |
| LTXVAddGuide frame_idx 0, strength 0.7 (first frame) |
| LTXVAddGuide frame_idx -1, strength 0.7 (last frame, chained off the first) |
| LTXVPreprocess img_compression 18 |
| size / length 1280 x 720, 5 s @ 24 fps |
| audio LTXVEmptyLatentAudio — the model generates its own audio |
| ``` |
| |
| Both guides run at strength **0.7**, not 1.0, and the second consumes the |
| first's conditioning *and* latent. `LTXVCropGuides` strips the guide frames |
| before decode. |
| |
| ## prompt_enhance |
|
|
| The preset ships it **on**, loading `gemma4_e2b_it_bf16.safetensors` as a second |
| CLIP. It rewrites the prompt through Gemma before encoding. |
|
|
| **Turn it off when the prompt contains dialogue you need spoken verbatim, or a |
| trigger word.** The rewriter will paraphrase both. It is also the documented |
| reason a Comfy Cloud test destroyed the `AKUSPACE` trigger and the level words. |
| Leave it on only for loose scene prompts where wording does not matter. |
|
|
| ## The AKUSPACE LoRA does not belong in this graph |
|
|
| Tested and confirmed on 2026-08-13: the adapter is **reference-conditioned**. It |
| was trained to transform a reference audio input, so with no reference present |
| it is off-distribution and produces near-silence at any strength. In a graph |
| where audio is pinned by a zero noise mask it never runs at all. |
|
|
| The working chain is **video render → take its generated audio → a2a pass with |
| the LoRA → remux onto the same frames**. That also gives the before/after pair |
| for free: the untouched render is the base-model baseline. |
|
|
| Note `loras/ltx-2.5-22b-distilled-lora-450-bf16.safetensors` in the LTX repo is |
| an unrelated distillation-acceleration LoRA, not ours. |
|
|
| ## Serving |
|
|
| ComfyUI on **8189** (8188 is a proxy on some templates). Reachable across a |
| tailnet as `http://<host>:8189`. ComfyUI holds its weights in VRAM after a run — |
| call `POST /free {"unload_models":true,"free_memory":true}` before running the |
| trainer on the same GPU, or the a2a pass dies with CUDA OOM while Comfy sits on |
| 66 GB. |
|
|
