Get Device

Get Device Mecha Recipe is a reflection-style node in a pack that's usually all about composing merges. It takes one recipe and returns, as a param recipe, the device that recipe's tensors live on - cuda:0, cpu, whatever it is. You then wire that string into another param input, so you can write workflows that adapt to where data actually is instead of hard-coding it.

It exists because comfy-mecha makes parameters (like device and dtype) part of the recipe graph. The pack's Mecha Merger has its own default_merge_device and output_device settings on the node itself, so most people never need this. Where it earns its keep: building self-adaptive merges - recipes that read the current device of one branch and pass it into a cast-style param elsewhere, so the workflow behaves correctly whether the GPU is loaded or everything has fallen back to CPU.

Inputs & output

• a (param) - the recipe to inspect. Note the merge-space suffix says param; you can inspect anything, but the output is naturally a param.
• merge_checkpointing - the usual branch-cache toggle.

Output: one recipe (MECHA_RECIPE) carrying the device string, e.g. "cuda:0". You can pipe it into any param socket that accepts a string recipe - device slots on cast-style operations, or store it via a Serializer to see what a branch resolved to.

How to use it (and when not to)

The realistic use is debugging and adaptive graphs. For debugging: wire a recipe through this node into a Serializer, run, and read the device in the serialized text - a quick way to confirm a branch actually moved to CPU. For adaptive graphs: instead of guessing, let the merge ask the model where it is. But if you're just trying to control where a merge runs, don't reach for this - the Mecha Merger node's default_merge_device / output_device dropdowns are the direct controls, and they're simpler.

Install & gotchas

ComfyUI Manager → search mecha → Mecha Merge Node Pack, or:

cd ComfyUI/custom_nodes
git clone https://github.com/ljleb/comfy-mecha.git
pip install -r comfy-mecha/requirements.txt

Restart; only dependency is sd-mecha==1.1.7.

The one thing that trips people: the output is a param recipe, not a string you can read in a text box directly - you need a Serializer (or Mecha Regex Weights's recipe_txt) to see it. And because it's a param, it flows into param sockets only; feeding it into a weight socket will refuse or misbehave. It's a niche node. You'll probably use it once, to understand your own graph, and then forget it exists - which is fine, that's the job.