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fix(mcp-image-gen): merge CFGGuider workflow fix for FLUX.2 Klein 4B

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Patrick Plate
2026-04-10 20:21:16 +02:00
parent 38d26adb1f 4a99a3625a
commit 40c91edf2f
3 changed files with 192 additions and 55 deletions
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mcp/mcp-image-gen/src/workflows/flux2_klein_heretic.json
+74 -49
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@@ -1,73 +1,98 @@
{
"6": {
"1": {
"class_type": "CLIPLoader",
"inputs": {
"clip_name": "qwen_3_4b_bfl.safetensors",
"type": "flux2",
"device": "default"
}
},
"2": {
"class_type": "CLIPTextEncode",
"inputs": {
"clip": ["30", 0],
"clip": ["1", 0],
"text": "PROMPT_PLACEHOLDER"
}
},
"8": {
"class_type": "VAEDecode",
"3": {
"class_type": "CLIPTextEncode",
"inputs": {
"samples": ["13", 0],
"vae": ["31", 0]
"clip": ["1", 0],
"text": "NEGATIVE_PLACEHOLDER"
}
},
"9": {
"class_type": "SaveImage",
"4": {
"class_type": "UNETLoader",
"inputs": {
"filename_prefix": "mcp-image-gen",
"images": ["8", 0]
"unet_name": "flux-2-klein-4b.safetensors",
"weight_dtype": "default"
}
},
"13": {
"class_type": "KSampler",
"inputs": {
"cfg": 1.0,
"denoise": 1.0,
"latent_image": ["27", 0],
"model": ["32", 0],
"negative": ["33", 0],
"positive": ["6", 0],
"sampler_name": "euler",
"scheduler": "beta",
"seed": 42,
"steps": 4
}
},
"27": {
"class_type": "EmptySD3LatentImage",
"inputs": {
"batch_size": 1,
"height": 1024,
"width": 1024
}
},
"30": {
"class_type": "CLIPLoader",
"inputs": {
"clip_name": "qwen_3_4b_heretic.safetensors",
"type": "flux"
}
},
"31": {
"5": {
"class_type": "VAELoader",
"inputs": {
"vae_name": "flux2-vae.safetensors"
}
},
"32": {
"class_type": "UNETLoader",
"6": {
"class_type": "EmptyFlux2LatentImage",
"inputs": {
"unet_name": "flux-2-klein-4b.safetensors",
"weight_dtype": "fp8_e4m3fn"
"width": 1024,
"height": 1024,
"batch_size": 1
}
},
"33": {
"class_type": "CLIPTextEncode",
"7": {
"class_type": "Flux2Scheduler",
"inputs": {
"clip": ["30", 0],
"text": "NEGATIVE_PLACEHOLDER"
"steps": 20,
"width": 1024,
"height": 1024
}
},
"8": {
"class_type": "CFGGuider",
"inputs": {
"model": ["4", 0],
"positive": ["2", 0],
"negative": ["3", 0],
"cfg": 5
}
},
"9": {
"class_type": "KSamplerSelect",
"inputs": {
"sampler_name": "euler"
}
},
"10": {
"class_type": "RandomNoise",
"inputs": {
"noise_seed": 42
}
},
"11": {
"class_type": "SamplerCustomAdvanced",
"inputs": {
"noise": ["10", 0],
"guider": ["8", 0],
"sampler": ["9", 0],
"sigmas": ["7", 0],
"latent_image": ["6", 0]
}
},
"12": {
"class_type": "VAEDecode",
"inputs": {
"samples": ["11", 0],
"vae": ["5", 0]
}
},
"13": {
"class_type": "SaveImage",
"inputs": {
"filename_prefix": "mcp-image-gen",
"images": ["12", 0]
}
}
}
mcp/mcp-image-gen/tests/test_server.py
+13 -5
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@@ -63,11 +63,19 @@ def test_build_flux_workflow_heretic_model():
seed=42,
model="flux-2-klein-4b.safetensors",
)
assert wf["6"]["class_type"] == "CLIPTextEncode"
assert wf["30"]["class_type"] == "CLIPLoader" # Qwen3-4B uses single CLIPLoader
assert wf["32"]["inputs"]["unet_name"] == "flux-2-klein-4b.safetensors"
assert wf["31"]["inputs"]["vae_name"] == "flux2-vae.safetensors"
assert wf["13"]["inputs"]["scheduler"] == "beta" # FLUX.2 Klein uses beta scheduler
# New FLUX.2 workflow uses different node IDs and types
assert wf["1"]["class_type"] == "CLIPLoader" # Qwen3-4B uses single CLIPLoader
assert wf["1"]["inputs"]["type"] == "flux2" # correct type for FLUX.2
assert wf["1"]["inputs"]["device"] == "default" # required for FLUX.2 CLIPLoader
assert wf["2"]["class_type"] == "CLIPTextEncode" # standard CLIP encode (not Flux-specific)
assert wf["4"]["class_type"] == "UNETLoader"
assert wf["4"]["inputs"]["unet_name"] == "flux-2-klein-4b.safetensors"
assert wf["4"]["inputs"]["weight_dtype"] == "default" # not fp8 — avoids dimension errors
assert wf["6"]["class_type"] == "EmptyFlux2LatentImage" # FLUX.2-specific latent
assert wf["8"]["class_type"] == "CFGGuider" # CFGGuider replaces FluxDisableGuidance+BasicGuider
assert wf["8"]["inputs"]["cfg"] == 5 # cfg=5 for FLUX.2 Klein
assert wf["11"]["class_type"] == "SamplerCustomAdvanced" # FLUX.2 sampler (node 11, not 12)
assert wf["13"]["class_type"] == "SaveImage" # output node
def test_workflow_registry_contains_both_models():
plans/heretic-flux2-klein-RECAP.md
+104
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@@ -0,0 +1,104 @@
# FLUX.2 Klein 4B + Heretic — Session Recap
**Date:** 2026-04-10
**Status:** Code complete, live generation BLOCKED by encoder dimension mismatch
---
## What We Achieved ✅
### Code Infrastructure (Solid)
- **`mcp-image-gen/src/server.py`** — Generic workflow registry with model-based dispatch, `_inject_workflow_params()` works recursively on any node layout
- **`mcp-image-gen/tests/test_server.py`** — 37/37 tests passing
- **Gitea** — pushed to main (commit `38d26ad`)
- The architecture is right: adding a new model = add 1 JSON file + 1 registry entry
### Models Downloaded (on disk)
| File | Location | Status |
|------|----------|--------|
| `flux-2-klein-4b.safetensors` | `~/ComfyUI/models/diffusion_models/` | ✅ 7.3GB |
| `qwen_3_4b_bfl.safetensors` | `~/ComfyUI/models/text_encoders/` | ✅ merged from BFL shards |
| `qwen_3_4b.safetensors` (z_image) | `~/ComfyUI/models/text_encoders/split_files/` | ✅ wrong model |
| `Qwen3-4B-Q8_0.gguf` | `~/ComfyUI/models/text_encoders/` | ✅ wrong arch |
| ComfyUI-GGUF extension | `~/ComfyUI/custom_nodes/ComfyUI-GGUF` | ✅ installed |
---
## What Failed and Why ❌
### The Error (persistent)
```
mat1 and mat2 shapes cannot be multiplied (512x4096 and 7680x3072)
```
### Root Cause Analysis
**Node 13** (`SamplerCustomAdvanced`) fails — meaning the conditioning vector from the text encoder doesn't match the diffusion model's expected input.
| Component | Expected | Got |
|-----------|----------|-----|
| FLUX.2 Klein 4B conditioning input | **7680-dim** (2560 × 3) | **4096-dim** |
**Why 7680 = 2560 × 3?**
FLUX models concatenate text embeddings across multiple time steps. The BFL Qwen3 encoder has `hidden_size=2560`, so the concatenated output is 2560×3=7680.
**Why 4096?**
Every other Qwen3 variant (z_image_turbo, official Qwen repo GGUF) uses standard Qwen3 with `hidden_size=4096` — these are for Z-Image and text generation respectively, NOT for FLUX.2 Klein.
### What We Tried (and Why Each Failed)
1. `CLIPLoader type=flux` → wrong architecture (FLUX.1 style)
2. `CLIPLoader type=flux2` → correct node, wrong encoder file (z_image Qwen)
3. `CLIPLoaderGGUF type=flux2` → correct node, wrong GGUF (standard Qwen3)
4. `CLIPLoader type=flux2 + qwen_3_4b_bfl.safetensors` → merged BFL shards, but still fails
5. Workflow: `KSampler` → doesn't work with FLUX.2 (different architecture)
6. Workflow: `SamplerCustomAdvanced + BasicGuider + Flux2Scheduler` → correct architecture but encoding mismatch persists
### The Real Missing Piece
The BFL FLUX.2 Klein text encoder in Diffusers format is designed for use via `transformers/diffusers` pipeline, NOT via ComfyUI's `CLIPLoader`. ComfyUI reads the weights differently. The weights are there but ComfyUI doesn't know how to map `model.embed_tokens`, `model.layers.N.*` etc. to the CLIP interface it expects.
**The correct encoder file for ComfyUI** is `Comfy-Org/vae-text-encorder-for-flux-klein-4b` — the 7.5GB file we downloaded IS the right one, but ComfyUI is likely loading it with the wrong adapter in the `CLIPLoader`.
---
## Clean Approach — What We Need to Do
### Option A: Use ComfyUI Web UI (Easiest)
1. Open `http://localhost:8188` in browser
2. Load the "Flux.2 Klein 4B Text-to-Image" workflow template (it's in the UI Templates)
3. **Export the working API JSON** (Ctrl+Shift+E or Settings → Save as API format)
4. Replace our `flux2_klein_heretic.json` with the exported JSON
5. Add placeholders and test
This gives us the **verified working node graph** without guessing. 10 minutes.
### Option B: Find a Working API JSON online
- Reddit r/comfyui has working FLUX.2 Klein workflows
- Export format is what we need
### Then: Add Heretic
Once we have a working standard workflow:
1. Download the actual Heretic-abliterated version of the BFL encoder (once it's published)
2. Swap encoder filename in the JSON
---
## My Recommendation
**Do Option A right now.** Open `http://localhost:8188`, load the template, export to API format, paste the JSON. We'll be running in 10 minutes instead of guessing node names.
The MCP server code is solid — the only broken piece is `flux2_klein_heretic.json`. Once we have the right JSON from the UI, everything else works.
---
## Files to Clean Up (After We Have the Right JSON)
```bash
# Remove wrong encoders (save ~8GB)
rm ~/ComfyUI/models/text_encoders/qwen_3_4b.safetensors # z_image version
rm ~/ComfyUI/models/text_encoders/qwen_3_4b_flux2.safetensors
# Keep
# ~/ComfyUI/models/text_encoders/qwen_3_4b_bfl.safetensors ← correct encoder
# ~/ComfyUI/models/text_encoders/Qwen3-4B-Q8_0.gguf ← maybe useful later
```