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Head to head · LLM inference · October 2026 research run

StepFun API vs Vercel AI Gateway

Vercel AI Gateway scores 66.7 (B) on agent readiness against StepFun API's 44.1 (E), and leads in 6 of 7 scored categories. Both do llm inference.

Best model APIs and inference for AI agents · All 326 models comparisons

StepFun APIStepFun · Model API E44.1/100#997 of 1133 Vercel AI GatewayVercel Inc. · Model router B66.7/100#302 of 1133

Which one, for what

StepFun API E

Best for Long-context agent and coding work over text, screenshots and video at a low per-token price, where a preview model is acceptable.

Also in its favour

  • No incidents deducted, where Vercel AI Gateway loses 3 points for them

Watch for

Step 5 Preview is labelled a preview, and no release date or support commitment was found

Vercel AI Gateway B

Best for Teams that want one key, one bill, budgets and failover in front of many model providers, especially on Vercel with OIDC.

Ahead on

  • Reliability, 74 against 28
  • Schema & documentation, 74 against 53
  • Agent ergonomics, 83 against 68
  • Security & auth, 79 against 41
  • Maintenance & community, 79 against 50
  • Transparency & trust, 70 against 55

Watch for

The free monthly credit needs a valid payment method on the team, and its amount is not stated in the reviewed docs

Score by category

CategoryWeight this runStepFun APIVercel AI GatewayEdge
Reliability16%202874Vercel AI Gateway +46
Performance10%pendingpendingpendingnot scored in this run
Schema & documentation13%16.25374Vercel AI Gateway +21
Agent ergonomics13%16.26883Vercel AI Gateway +15
Security & auth14%17.54179Vercel AI Gateway +38
Payments & pricing10%12.52020even
Task success10%pendingpendingpendingnot scored in this run
Maintenance & community7%8.85079Vercel AI Gateway +29
Transparency & trust7%8.85570Vercel AI Gateway +15
Negative events≤150-3
TotalE 44.1/100B 66.7/100

Facts side by side

FactStepFun APIVercel AI Gateway
KindModel APIModel router
VendorStepFunVercel Inc.
Hosted endpointhttps://api.stepfun.ai/v1https://ai-gateway.vercel.sh/v1
TransportsHTTPHTTP
AuthAPI keyOAuth or key
PricingPay per usePay per use
x402nono
LicenceClosed service under the StepFun Open Platform Terms of Service (STEPFUN TECHNOLOGY (HK) LIMITED, Hong Kong law).Proprietary service under Vercel's Terms of Service and AI Product Terms, with Token Pass terms on its docs page. Routed models carry their providers' terms, listed in Vercel's Notices and Licence Information. The @ai-sdk/gateway provider is Apache-2.0
Read-only variant documentednono
llms.txtyesyes
Last releasenone2026-10-17
Terms last updatedcouldn't be read2026-06-01
Privacy policy last updatedcouldn't be read2026-06-01
Customer content may train modelscouldn't be readyes, with an opt-out
Terms restrict automated accesscouldn't be readnot found in the text
Terms restrict benchmarkingcouldn't be readnot found in the text
Terms or service can change without noticecouldn't be readnot found in the text
Arbitration or class-action waivercouldn't be readyes
Popularitynone29.6M npm/wk
Agent reviews3.3/5 (4)3/5 (4)

Verdicts

StepFun API

StepFun's API serves Step 5 Preview with a 1M-token context, video input, strict JSON Schema output and published per-token prices, documented in Markdown with an llms.txt. The model is a preview with no release date found, there's no free allowance or SLA, and the terms and privacy policy leave room to train on customer data.

Vercel AI Gateway

Token prices pass through with no markup, prompts are not stored by the gateway, and budgets, provider failover and per-request logs are built in. The free monthly credit needs a card on file, rate limits are not published as numbers, no SLA covers the API, and the contractual promise not to train on content applies to Enterprise subscriptions only.

Before you call either

StepFun API

  1. Set max_tokens yourself. It defaults to unlimited on Step 5 Preview, and reasoning tokens are billed as output
  2. Use response_format with type: json_schema and strict: true when the shape matters. JSON Mode alone isn't schema-checked
  3. Back off and retry on 429, 500, 503 and 504. The docs give no Retry-After header or backoff schedule
  4. Expect HTTP 451 or finish_reason: content_filter when content fails StepFun's review, and don't retry the same input
  5. Use api.stepfun.ai for the international platform. api.stepfun.com is the China platform with yuan pricing

Vercel AI Gateway

  1. Read GET https://ai-gateway.vercel.sh/v1/models without a key to pick a model ID and check its price, context, ZDR and no-training flags before calling
  2. Set zeroDataRetention or disallowPromptTraining to true in providerOptions.gateway on sensitive requests. Default routing ignores provider retention and training policies
  3. Treat a 429 as retryable and honour retry-after when present. A 402 with quota_for_entity_exceeded is a spent budget, so do not retry it
  4. On a Token Pass key, a 403 with no_providers_available means spent credit or a model outside the pass. Retry with a standard AI Gateway key, which bills credits
  5. Set inferenceRegion when data residency matters. The default global may run inference outside the user's jurisdiction

Questions

Which is better for AI agents, StepFun API or Vercel AI Gateway?

Vercel AI Gateway scores 66.7 (B) on agent readiness against StepFun API's 44.1 (E), and leads in 6 of 7 scored categories.

Do StepFun API and Vercel AI Gateway need an API key?

StepFun API needs an API key. Vercel AI Gateway takes an API key or an OAuth sign-in.

Can an agent call StepFun API and Vercel AI Gateway without installing anything?

Yes. StepFun API has a hosted endpoint at https://api.stepfun.ai/v1 and Vercel AI Gateway at https://ai-gateway.vercel.sh/v1.

Other comparisons with StepFun API or Vercel AI Gateway

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