o3 vs Step 3.7 Flash
o3 (2025) and Step 3.7 Flash (2026) are frontier-tier reasoning models from OpenAI and StepFun. o3 ships a 200k-token context window, while Step 3.7 Flash ships a 256k-token context window. On Humanity's Last Exam, Step 3.7 Flash leads by 26.9 pts. On pricing, Step 3.7 Flash costs $0.20/1M input tokens versus $2/1M for the alternative. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Step 3.7 Flash is ~900% cheaper at $0.20/1M; pay for o3 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | o3 | Step 3.7 Flash |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | reasoning-heavy apps, multimodal apps, and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200k | 256k |
| Cheapest output | $8/1M tokens | $1.15/1M tokens |
| Provider routes | 3 tracked | 3 tracked |
| Shared benchmarks | 1 rows | Humanity's Last Exam leader |
Decision tradeoffs
- o3 uniquely exposes Code execution in local model data.
- Local decision data tags o3 for Coding, RAG, and Agents.
- Step 3.7 Flash holds a shared-benchmark lead on Humanity's Last Exam, ahead by 26.9 points.
- Step 3.7 Flash has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Step 3.7 Flash has the lower cheapest tracked output price at $1.15/1M tokens.
- Local decision data tags Step 3.7 Flash for Coding, RAG, and Agents.
Monthly cost at traffic
Estimate token spend from the cheapest tracked input and output route or tier on this page.
o3
$3,600
Cheapest tracked route/tier: OpenAI API
Step 3.7 Flash
$448
Cheapest tracked route/tier: StepFun
Estimated monthly gap: $3,153. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- Step 3.7 Flash is $6.85/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Check replacement coverage for Code execution before moving production traffic.
- Provider overlap exists on OpenRouter; start route-level A/B tests there.
- o3 is $6.85/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- o3 adds Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-04-16 | 2026-05-29 |
| Context window | 200k | 256k |
| Parameters | — | 198B (11B active) |
| Architecture | decoder only | mixture of experts |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Commercial use | Commercial use with conditions | Commercial use with conditions |
| Knowledge cutoff | 2024-06 | - |
Pricing and availability
| Pricing attribute | o3 | Step 3.7 Flash |
|---|---|---|
| Input price | $2/1M tokens | $0.20/1M tokens |
| Output price | $8/1M tokens | $1.15/1M tokens |
| Providers |
Capabilities
| Capability | o3 | Step 3.7 Flash |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | No |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | o3 | Step 3.7 Flash |
|---|---|---|
| Humanity's Last Exam | 20.3 | 47.2 |
Deep dive
On shared benchmark coverage, Humanity's Last Exam has o3 at 20.3 and Step 3.7 Flash at 47.2, with Step 3.7 Flash ahead by 26.9 points. The largest visible gap is 26.9 points on Humanity's Last Exam, which matters most when that benchmark mirrors your workload. Treat isolated benchmark wins as directional, because provider routing, prompt style, and tool access can move real application results.
The capability footprint differs most on code execution: o3. Both models share vision, multimodal input, reasoning mode, and function calling, so the practical split is not just feature count. Use those differences to decide whether the page is about raw model quality, agentic coding support, multimodal ingestion, or predictable structured API behavior.
For cost, o3 lists $2/1M input and $8/1M output tokens on the cheapest tracked provider, while Step 3.7 Flash lists $0.20/1M input and $1.15/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts Step 3.7 Flash lower by about $3.31 per million blended tokens. Availability is 3 providers versus 3, so concentration risk also matters.
Choose o3 when coding workflow support are central to the workload. Choose Step 3.7 Flash when long-context analysis, larger context windows, and lower input-token cost are more important. For production, rerun your own prompts through the exact provider, region, and tool stack you plan to ship.
FAQ
Which has a larger context window, o3 or Step 3.7 Flash?
Step 3.7 Flash supports 256k tokens, while o3 supports 200k tokens. That gap matters most for long documents, large codebases, retrieval-heavy agents, and conversations where earlier context must remain visible.
Which is cheaper, o3 or Step 3.7 Flash?
Step 3.7 Flash is cheaper on tracked token pricing. o3 costs $2/1M input and $8/1M output tokens. Step 3.7 Flash costs $0.20/1M input and $1.15/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is o3 or Step 3.7 Flash open source?
o3 is listed under Proprietary. Step 3.7 Flash is listed under Proprietary. License labels affect whether you can self-host, redistribute weights, or rely only on hosted APIs, so confirm the upstream license before deployment.
Which is better for vision, o3 or Step 3.7 Flash?
Both o3 and Step 3.7 Flash expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, o3 or Step 3.7 Flash?
Both o3 and Step 3.7 Flash expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Where can I run o3 and Step 3.7 Flash?
o3 is available on OpenAI API, OpenRouter, and Vercel AI Gateway. Step 3.7 Flash is available on StepFun, OpenRouter, and NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
Continue comparing
Last reviewed: 2026-06-08. Data sourced from public model cards and provider documentation.