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

Try both on us. Starter credit covers your first requests, then one key routes gpt-oss-120b and Step 3.5 Flash 2603. Switch by changing the model name.

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

gpt-oss-120b has the lower published input-plus-output rate, more Credits provider routes and the lower measured p50 time to first token. Step 3.5 Flash 2603 has the larger context window.

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

$0.422/1MStep 3.5 Flash 2603 cheapest route

1033 msOpenAI: gpt-oss-120b fastest measured p50 TTFT via cerebras

2440 msStep 3.5 Flash 2603 fastest measured p50 TTFT via stepfun

The price comparison adds each route's rate for one million input tokens and one million output tokens; your cost depends on your input/output mix. 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 98#132 —

Context131,072 tokens262,144 tokens

Credits provider routes241

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

Cached input$0.015825/1M to $0.1055/1M$0.0211/1M

Privacy posturehas Confidential route (E2EE + ZDR)provider posture varies

Fastest measured p50 TTFT1033 ms via cerebras2440 ms via stepfun

Highest measured throughput132 tok/s via amazon-bedrocknot enough data

Recent route uptime range88.31% to 100.00%100.00%

Modes chat chat

OpenAI: gpt-oss-120b routes

Overview24 Credits routes
PricingInput, cached input, and output rates
ProvidersAll serving providers

Step 3.5 Flash 2603 routes

Overview1 Credits routes

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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?

gpt-oss-120b has the lower published input-plus-output rate, more Credits provider routes and the lower measured p50 time to first token. Step 3.5 Flash 2603 has the larger context window.

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 1033 ms for OpenAI: gpt-oss-120b and 2440 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.