StepFun Client

StepFun Client is the boring node every other node in this pack depends on. It's where you paste your API key, and it hands out a ready-to-use client object that the chat nodes and the video uploader expect on their client input. On its own it does nothing visible - no output, no display, no cost. It's the gateway, not the destination.

Think of it like a power supply for the rest of the pack: you wire one StepFunClient into the graph, and it feeds the nodes that actually talk to the API. Every meaningful StepFun workflow starts here.

How it works

Under the hood it constructs an OpenAI SDK client pointed at StepFun's OpenAI-compatible endpoint:

OpenAI(base_url="https://api.stepfun.com/v1", api_key=api_key)

That's it. The pack's chat nodes reuse the official OpenAI client rather than rolling their own HTTP calls, which means StepFun is speaking OpenAI's wire protocol - a pattern you'll see across a lot of these API-wrapper packs. The client object flows through the graph as a custom type (STEPFUN_CLIENT), so you can't accidentally plug it into a node expecting a different kind of client; the type system keeps the wires honest.

Inputs and outputs

• api_key - a single required string field. Paste the key you get from the StepFun platform's account overview page.

Output: client, typed STEPFUN_CLIENT, which feeds into StepFun Chat Completion, StepFun Video Chat, and StepFun Video File Uploader.

That's the entire node. One field, one output.

Getting the key and installing

Install the pack first - ComfyUI Manager (search "ComfyUI-SCStepFun") or:

cd ComfyUI/custom_nodes
git clone https://github.com/chenbaiyujason/ComfyUI_StepFun
cd ComfyUI_StepFun
pip install -r requirements.txt

Restart ComfyUI. Then sign up at platform.stepfun.com, grab a key from the account overview, and paste it into the node. StepFun is a Chinese AI lab (the same company behind the open-weights StepVideo and NextStep models), so the signup and billing flow is oriented toward their platform - check their request-restriction page if you hit a wall on what models your key can use. The README links to it for a reason.

Common issues

• 401s downstream - a typo'd or expired key here will make every chat node fail with an auth error. The client node itself won't complain; the failure shows up one step later.
• Key saved into the workflow - this is the one to actually worry about. The key lives in a plain widget, which means it's embedded in the workflow JSON and in the metadata of any PNG you save from that workflow. The ecosystem's security history is a reminder that custom-node workflows get shared and scraped; treat a workflow containing a live key like a password. Rotate keys you've shared, or blank the field before exporting.
• No internet - no client error, no call ever succeeds.

One more honest note: because it's an API-key node for a paid service, it's only worth installing if you're actually going to use the StepFun models. If that's your plan, this is the one node you can't skip - everything else in the pack plugs into it.