BMAB SD-WebUI API T2I

What it is

This is the actual "generate an image" node in BMAB's webui-bridge family, and it does exactly what it sounds like: it fires a text-to-image request at a remote Automatic1111-style server and hands the resulting image back into your ComfyUI graph. You're not running the diffusion model locally in ComfyUI at all here - you're a client, and the remote webui does the actual sampling.

It only makes sense paired with BMAB SD-WebUI API Server, which is where the connection comes from. Think of it as ComfyUI's version of filling out the txt2img tab on a webui you're not looking at.

Inputs and outputs

The core fields will look instantly familiar if you've ever used A1111: prompt and negative_prompt (both multiline), width/height (default 512, capped 128–4000), steps (default 20), cfg_scale (default 7), and seed (default -1 for random, up to 1,000,000). All of that gets required - you set it here on the ComfyUI side and BMAB relays it to the server.

The required api_server input is the wire coming out of the Server node. Three optional sockets round it out: hires_fix (a Hires.fix config, which comes from elsewhere in the BMAB pack - not one of the nodes covered here), extension (an EXTENSION config, same story), and controlnet - which is exactly where BMAB SD-WebUI API ControlNet plugs in, letting you drive the remote server's ControlNet extension from ComfyUI.

Two outputs: API Server - the same connection, passed straight through - and image, the generated result. Passing the server connection back out is a small but deliberate BMAB habit you'll see across this pack: it means you can chain a T2I into an I2I into another T2I without rewiring the Server node into every single one.

How to install it

Through ComfyUI Manager, search comfyui_bmab - it pulls in the pack itself plus the two dependencies it needs (comfyui_controlnet_aux and ComfyUI_IPAdapter_plus). Manually:

cd ComfyUI/custom_nodes
git clone https://github.com/portu-sim/comfyui_bmab.git
cd comfyui_bmab
pip install -r requirements.txt

then the same for the two dependency repos, and a restart. This node itself doesn't need anything beyond BMAB's base requirements - the heavy lifting happens on the remote server, not locally.

Common issues

Since generation happens on the other machine, none of ComfyUI's own VRAM or model-loading concerns apply here - but the remote server's do. If the webui is out of memory or the wrong checkpoint is loaded, this node will fail or hang the same way a manual txt2img request would, and the error will usually be webui-side rather than something ComfyUI can explain clearly.

Seed behavior is worth double-checking too: -1 means "let the server pick," which is great for exploring but means you can't blindly reproduce a result just by looking at the ComfyUI graph - you need the actual seed the webui used, which BMAB doesn't surface back to you here. If reproducibility matters, set a fixed seed explicitly rather than leaving it at -1.

And because hires_fix, extension, and controlnet are all optional inputs coming from other BMAB nodes, an empty graph without them will just run a plain txt2img - nothing breaks, but it's easy to think you've wired in a hires pass or a ControlNet unit when you actually haven't connected anything to that socket.