Question 1

What does this GPT-5.4 mini vs Step 3.5 Flash 2603 comparison cover?

Accepted Answer

It brings together documented inputs and outputs, token limits, deployment terms and available pricing. When both models have source-linked, verified results on a shared benchmark, those results are shown with their individual sources. The comparison is a starting point for evaluating your own workload.

Question 2

Which is cheaper: GPT-5.4 mini or Step 3.5 Flash 2603?

Accepted Answer

GPT-5.4 mini lists $0.75 input and $4.50 output per 1M tokens. Step 3.5 Flash 2603 lists $0.10 input and $0.30 output. The cheaper workload depends on the mix of input and output. Long-context tiers, caching, batch processing and retries can change the bill.

Question 3

Which has the larger context window: GPT-5.4 mini or Step 3.5 Flash 2603?

Accepted Answer

GPT-5.4 mini lists 400K tokens and Step 3.5 Flash 2603 lists 256K. GPT-5.4 mini therefore has the larger recorded context window, but capacity alone is not a quality score.

Question 4

Which is faster: GPT-5.4 mini or Step 3.5 Flash 2603?

Accepted Answer

There is no matched speed measurement for both models with the same source, host, region and date. Test the same prompts at your expected concurrency and measure time to the first useful response as well as complete task time.

Question 5

What input and output types do GPT-5.4 mini and Step 3.5 Flash 2603 support?

Accepted Answer

GPT-5.4 mini records text, image input and text output. Step 3.5 Flash 2603 records text input and text output. “Not documented” means the current source record is incomplete; it does not prove that a modality is unsupported.

Question 6

Should I choose GPT-5.4 mini or Step 3.5 Flash 2603?

Accepted Answer

Consider GPT-5.4 mini if you need larger context. Consider Step 3.5 Flash 2603 if you need larger maximum output or a lower listed input rate or a lower listed output rate. Step 3.5 Flash 2603 offers downloadable weights; GPT-5.4 mini is listed as a proprietary model. Compare licence terms and operating costs before choosing a deployment. Test both on the same representative examples and judge the output against your acceptance criteria. Include tool failures, retries and the time to a completed task.

Specification	GPT-5.4 mini	Step 3.5 Flash 2603
Provider	OpenAI	StepFun
Listed pricing route	OpenAI	StepFun
Model family	gpt-mini	—
Accepted inputs	text, image	text
Produced outputs	text	text
Context window	400KHigher	256K
Max output	128K	256KHigher
Input price / 1M	$0.75	$0.10Lower
Output price / 1M	$4.50	$0.30Lower
Reasoning mode	Documented	Documented
Tool calling	Documented	Documented
Image input	Documented	Not documented
Audio input	Not documented	Not documented
Structured output	Documented	Not documented
License	Proprietary	Open weights

GPT-5.4 mini vs Step 3.5 Flash 2603

GPT-5.4 mini

Step 3.5 Flash 2603

Key differences

Pricing, limits and capabilities

Which model should you choose?

Documentation and model profiles

Questions people ask

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