Flux API
Flux image generation with Dev, Pro, and 2 Klein, plus single-image editing with Dev and Pro.
curl -X POST https://runapi.ai/api/v1/flux/text_to_image \
-H "Authorization: Bearer $RUNAPI_KEY" \
-H "Content-Type: application/json" \
-d '{
"model": "flux-dev",
"prompt": "Generate a 4K product hero image of a matte-black water bottle on a beige stone surface, soft side light."
}'import { FluxClient } from "@runapi.ai/flux";
const client = new FluxClient();
const result = await client.textToImage.run({
model: "flux-dev",
prompt: "Generate a 4K product hero image of a matte-black water bottle on a beige stone surface, soft side light.",
});require "runapi/flux"
client = RunApi::Flux::Client.new
result = client.text_to_image.run(
model: "flux-dev",
prompt: "Generate a 4K product hero image of a matte-black water bottle on a beige stone surface, soft side light."
)npx skills add runapi-ai/flux -g# Claude Code
claude mcp add runapi -s user -- npx -y @runapi.ai/mcp
# Codex
codex plugin install runapi-mcp@agents
# Cursor / Windsurf / VS Code
npx @runapi.ai/mcp init cursorFlux spans high-quality production, efficient iteration, and low-latency generation across three models, with single-image editing available on Dev and Pro.
- Multiple variants for different speed, quality, and cost tiers
- Model skill includes docs, schemas, pricing, and setup notes
- Works with Claude Code, Codex, Gemini CLI, Cursor, and VS Code
- Single API key and unified billing across all variants
- Async task management with polling and webhook callbacks
- Failed generations are not charged
Compare all API variants
Install the Flux skill for app development
Load the model docs, schemas, pricing notes, and setup steps into your coding workspace.
# Install the model skill for app development workflows
npx skills add runapi-ai/flux -gInstall the Flux skill for this app: 1. Add runapi-ai/flux with the skills installer. 2. Load SKILL.md in this workspace. 3. Use its docs, schemas, pricing notes, and setup steps when adding model features. 4. Confirm the install path when done.
From model skill to first result in four steps
Choose a model
Browse the model catalog and pick the model and variant that match your output type, quality bar, and latency target. Each variant page shows its model ID, pricing, and parameter constraints so you can compare before committing.
Configure
Set your RunAPI API key as an environment variable and install the model skill in your coding workspace. The skill loads docs, typed schemas, pricing notes, and setup steps so your agent has the right context from the start.
Call
Use the skill instructions to add the model feature inside your application. Send a POST request with your prompt, model ID, and parameters. RunAPI routes the request, manages the async lifecycle, and returns structured JSON.
Receive
Poll by task ID for completion, stream results end-to-end when supported, or configure a webhook callback URL to receive results automatically. The CLI provides a built-in wait command, and the SDKs offer both polling and callback patterns.
What is the Flux API?
The Flux API exposes a image model from Black Forest Labs, accessible through RunAPI with a single API key and per-call billing. Developers call Flux the same way they call any other model in the RunAPI catalog — set the model parameter, submit a request, and receive structured JSON. The model skill packages docs, typed schemas, pricing notes, and setup steps so your coding agent has the right context before you write integration code. Billing is unified across all providers, failed generations are never charged, and results are retrievable by task ID.
Why route the Flux API through RunAPI
One auth, every provider
A single RunAPI API key unlocks the whole model catalog across all providers. No separate accounts to create, no API keys to rotate per integration, and no credential management overhead. Add a new model to your app by changing one parameter.
Unified pricing & billing
Per-call pricing in USD, billed monthly into a single invoice. No subscription tiers, no minimum spend, and failed generations are never charged. The pricing page and check_pricing API show exact costs before you commit to a model.
Schema-first SDK
Typed schemas, parameter constraints, and setup notes are packaged in the model skill so your implementation starts from the right contract. The skill loads into Claude Code, Codex, Gemini CLI, Cursor, and VS Code — your agent knows the correct request shape before you write a line of code.
Common questions
Which Flux model should I use?
Use Flux Dev for efficient iteration, Flux Pro for the strongest prompt adherence and visual detail, and Flux 2 Klein for rapid, low-latency workflows.
Can Flux edit an existing image?
Yes. With Flux Dev or Flux Pro, the remix-image endpoint edits exactly one publicly accessible source image from text instructions and returns the same task response shape as text-to-image.
Which variant should I start with?
Pick the cheapest variant that meets your quality bar. Most teams start on the fast variant and graduate to pro for production.
Is there a free tier?
New accounts get free first calls on every model. After that, pay per call.
Do you stream results?
Where streaming is available, RunAPI streams end-to-end.
How are failures billed?
Failed generations are not charged.
Are outputs cached?
Generated outputs are stored and retrievable by task ID. Inputs are not cached.
Can I use commercially?
Yes — commercial use is included for every variant unless a model license explicitly restricts it, which is called out on the variant page.
What about rate limits?
Per-key rate limits scale with usage tier. See pricing page for current limits.
Where can I report issues?
Open an issue on the public GitHub repo or email support.