StepFun

FluffBuzz includes a bundled StepFun provider plugin with two provider ids:

stepfun for the standard endpoint
stepfun-plan for the Step Plan endpoint

Standard and Step Plan are separate providers with different endpoints and model ref prefixes (stepfun/... vs stepfun-plan/...). Use a China key with the .com endpoints and a global key with the .ai endpoints.

Region and endpoint overview

Endpoint	China (`.com`)	Global (`.ai`)
Standard	`https://api.stepfun.com/v1`	`https://api.stepfun.ai/v1`
Step Plan	`https://api.stepfun.com/step_plan/v1`	`https://api.stepfun.ai/step_plan/v1`

Auth env var: STEPFUN_API_KEY

Built-in catalog

Standard (stepfun):

Model ref	Context	Max output	Notes
`stepfun/step-3.5-flash`	262,144	65,536	Default standard model

Step Plan (stepfun-plan):

Model ref	Context	Max output	Notes
`stepfun-plan/step-3.5-flash`	262,144	65,536	Default Step Plan model
`stepfun-plan/step-3.5-flash-2603`	262,144	65,536	Additional Step Plan model

Getting started

Choose your provider surface and follow the setup steps.

Standard
Step Plan

Best for: general-purpose use via the standard StepFun endpoint.

Choose your endpoint region

Auth choice	Endpoint	Region
`stepfun-standard-api-key-intl`	`https://api.stepfun.ai/v1`	International
`stepfun-standard-api-key-cn`	`https://api.stepfun.com/v1`	China

Run onboarding

fluffbuzz onboard --auth-choice stepfun-standard-api-key-intl

Or for the China endpoint:

fluffbuzz onboard --auth-choice stepfun-standard-api-key-cn

Non-interactive alternative

fluffbuzz onboard --auth-choice stepfun-standard-api-key-intl \
  --stepfun-api-key "$STEPFUN_API_KEY"

Verify models are available

fluffbuzz models list --provider stepfun

Model refs

Default model: stepfun/step-3.5-flash

Best for: Step Plan reasoning endpoint.

Choose your endpoint region

Auth choice	Endpoint	Region
`stepfun-plan-api-key-intl`	`https://api.stepfun.ai/step_plan/v1`	International
`stepfun-plan-api-key-cn`	`https://api.stepfun.com/step_plan/v1`	China

Run onboarding

fluffbuzz onboard --auth-choice stepfun-plan-api-key-intl

Or for the China endpoint:

fluffbuzz onboard --auth-choice stepfun-plan-api-key-cn

Non-interactive alternative

fluffbuzz onboard --auth-choice stepfun-plan-api-key-intl \
  --stepfun-api-key "$STEPFUN_API_KEY"

Verify models are available

fluffbuzz models list --provider stepfun-plan

Model refs

Default model: stepfun-plan/step-3.5-flash
Alternate model: stepfun-plan/step-3.5-flash-2603

Advanced configuration

Full config: Standard provider

{
  env: { STEPFUN_API_KEY: "your-key" },
  agents: { defaults: { model: { primary: "stepfun/step-3.5-flash" } } },
  models: {
    mode: "merge",
    providers: {
      stepfun: {
        baseUrl: "https://api.stepfun.ai/v1",
        api: "openai-completions",
        apiKey: "${STEPFUN_API_KEY}",
        models: [
          {
            id: "step-3.5-flash",
            name: "Step 3.5 Flash",
            reasoning: true,
            input: ["text"],
            cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
            contextWindow: 262144,
            maxTokens: 65536,
          },
        ],
      },
    },
  },
}

Full config: Step Plan provider

{
  env: { STEPFUN_API_KEY: "your-key" },
  agents: { defaults: { model: { primary: "stepfun-plan/step-3.5-flash" } } },
  models: {
    mode: "merge",
    providers: {
      "stepfun-plan": {
        baseUrl: "https://api.stepfun.ai/step_plan/v1",
        api: "openai-completions",
        apiKey: "${STEPFUN_API_KEY}",
        models: [
          {
            id: "step-3.5-flash",
            name: "Step 3.5 Flash",
            reasoning: true,
            input: ["text"],
            cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
            contextWindow: 262144,
            maxTokens: 65536,
          },
          {
            id: "step-3.5-flash-2603",
            name: "Step 3.5 Flash 2603",
            reasoning: true,
            input: ["text"],
            cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
            contextWindow: 262144,
            maxTokens: 65536,
          },
        ],
      },
    },
  },
}

Notes

The provider is bundled with FluffBuzz, so there is no separate plugin install step.
step-3.5-flash-2603 is currently exposed only on stepfun-plan.
A single auth flow writes region-matched profiles for both stepfun and stepfun-plan, so both surfaces can be discovered together.
Use fluffbuzz models list and fluffbuzz models set <provider/model> to inspect or switch models.

For the broader provider overview, see Model providers.

Model selection

Overview of all providers, model refs, and failover behavior.

Configuration reference

Full config schema for providers, models, and plugins.

Model selection

How to choose and configure models.

StepFun Platform

StepFun API key management and documentation.

Overview

Concepts and configuration

Providers

Region and endpoint overview

Built-in catalog

Getting started

Model refs

Model refs

Advanced configuration

Model selection

Configuration reference

Model selection

StepFun Platform

​Region and endpoint overview

​Built-in catalog

​Getting started

​Model refs

​Model refs

​Advanced configuration

​Related

Model selection

Configuration reference

Model selection

StepFun Platform

Region and endpoint overview

Built-in catalog

Getting started

Model refs

Model refs

Advanced configuration

Related