OpenAI compatible API · Attested · Public status

OpenAI: gpt-oss-120b vs Step 3.5 Flash 2603

gpt-oss-120b vs Step 3.5 Flash 2603: compare current API pricing, context, provider routes, privacy, p50 latency, and OpenAI-compatible access.

Verify gateway

Onebase URL to migrate

100sof models and routes

0prompt or output logs. Always.

Compare routesProviders, price, context, and policy posture in one view.

Use auto when uptime mattersKeep a primary model and let fallback handle provider failures.

Same API shapeUse the OpenAI client and set the model you want.

Practical read

Monthly evidence

OpenAI: gpt-oss-120b has the lower cheapest prompt+completion route on TrustedRouter. OpenAI: gpt-oss-120b has more provider fallback routes, while Step 3.5 Flash 2603 has the larger context window. Current TrustedRouter probes show OpenAI: gpt-oss-120b with the lower p50 TTFT.

$0.211/1MOpenAI: gpt-oss-120b cheapest route

$0.422/1MStep 3.5 Flash 2603 cheapest route

665 msOpenAI: gpt-oss-120b fastest measured p50 TTFT via baseten

1503 msStep 3.5 Flash 2603 fastest measured p50 TTFT via stepfun

Prices and live route measurements can change. Use the monthly reports when you need a stable evidence window, then run a small task-specific eval before choosing a production default.

OpenAI: gpt-oss-120bStep 3.5 Flash 2603

Model idopenai/gpt-oss-120bstepfun/step-3.5-flash-2603

Publisher OpenAI StepFun

AI IQ IQ 105#63 —

Context131,072 tokens262,144 tokens

Provider routes331

Cheapest route$0.211/1M$0.422/1M

Privacy posturehas provider E2EE routeprovider posture varies

Fastest measured p50 TTFT665 ms via baseten1503 ms via stepfun

Highest measured throughputnot enough datanot enough data

Recent route uptime range83.33% to 100.00%100.00%

Modes chat chat

OpenAI: gpt-oss-120b routes

Overview33 endpoints
PricingPrompt and completion rates
ProvidersAll serving providers

Step 3.5 Flash 2603 routes

Overview1 endpoints

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Production choice

Pick a default model. Keep fallback enabled.

TrustedRouter is useful when you know the model you want, but still need provider rollover, budget limits, usage records, and a prompt path you can verify.

OpenAI clientPython

client = OpenAI(
    base_url="https://api.trustedrouter.com/v1",
    api_key="sk-tr-v1-..."
)

response = client.chat.completions.create(
    model="openai/gpt-oss-120b",
    messages=messages,
)

Questions

Which should I use, OpenAI: gpt-oss-120b or Step 3.5 Flash 2603?

Is OpenAI: gpt-oss-120b or Step 3.5 Flash 2603 cheaper?

The current cheapest TrustedRouter route is $0.211/1M for OpenAI: gpt-oss-120b and $0.422/1M for Step 3.5 Flash 2603. The comparison uses current catalog prices and updates as provider pricing changes.

Is OpenAI: gpt-oss-120b or Step 3.5 Flash 2603 faster?

Current measured p50 time to first token is 665 ms for OpenAI: gpt-oss-120b and 1503 ms for Step 3.5 Flash 2603. These are routed probe measurements, not vendor-advertised speeds, and update as new samples arrive.

Can I test OpenAI: gpt-oss-120b and Step 3.5 Flash 2603 with the same API?

Yes. Use the same OpenAI-compatible TrustedRouter base URL and API key, then change only the model id between openai/gpt-oss-120b and stepfun/step-3.5-flash-2603. This makes side-by-side evals possible without maintaining two provider integrations.