GPT-5.4-Cyber (OpenAI) vs StepFun Step 3.5 Flash
Which one should you pick? Here's the full breakdown.
GPT-5.4-Cyber (OpenAI)
OpenAI's defensive-cybersecurity variant of GPT-5.4, launched 2026-04-16. Lowered refusal boundary for security-research tasks and native binary reverse-engineering. Access gated via Trusted Access for Cyber (TAC) program -- thousands of verified defenders, hundreds of teams, no public pricing
StepFun Step 3.5 Flash
StepFun's (China) agent-focused open-weight model -- Step 3.5 Flash launched 2026-02-01. 196B sparse MoE, ~11B active. Benchmarks slightly ahead of DeepSeek V3.2 at over 3x smaller total size. Step 3 (321B / 38B active, Apache 2.0) and Step3-VL-10B multimodal also in the family
| Category | GPT-5.4-Cyber (OpenAI) | StepFun Step 3.5 Flash |
|---|---|---|
| Ease of Use | 5.0 | 6.0 |
| Output Quality | 8.5 | 8.0 |
| Value | 7.0 | 9.0 |
| Features | 8.0 | 8.0 |
| Overall | 7.2 | 7.8 |
Pricing Comparison
| Feature | GPT-5.4-Cyber (OpenAI) | StepFun Step 3.5 Flash |
|---|---|---|
| Free Tier | No | Yes |
| Starting Price | Not publicly disclosed | $0 |
Which Should You Pick?
Pick GPT-5.4-Cyber (OpenAI) if...
Enterprise SOC teams, established security research orgs, and vetted individual defenders who can qualify for Trusted Access for Cyber. Strongest fit if your work involves binary analysis, vulnerability research, or defensive-security tooling where standard GPT-5.4 refusals actually block the work.
Visit GPT-5.4-Cyber (OpenAI)Pick StepFun Step 3.5 Flash if...
- ✓Easier to use (6 vs 5)
- ✓Better value for money (9/10)
- ✓Has a free tier
Teams building agent systems on Chinese open-weight foundations who want something other than DeepSeek or Qwen, especially if agentic tool-use is the primary workload. Also good for Chinese-market products where StepFun's domestic tuning advantages matter. And for anyone looking to add diversity to their open-weight evaluation matrix beyond the top-3 Chinese labs.
Visit StepFun Step 3.5 FlashOur Verdict
StepFun Step 3.5 Flash edges out GPT-5.4-Cyber (OpenAI) with a 7.8 vs 7.2 overall score. Both are solid picks, but StepFun Step 3.5 Flash has the advantage in value.