Claude Opus 4.5 vs Step 3.7 Flash
Claude Opus 4.5 (2025) and Step 3.7 Flash (2026) are frontier-tier reasoning models from Anthropic and StepFun. Claude Opus 4.5 ships a 200k-token context window, while Step 3.7 Flash ships a 256k-token context window. On SWE-bench Pro, Step 3.7 Flash leads by 14.5 pts. On pricing, Step 3.7 Flash costs $0.20/1M input tokens versus $5/1M 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 ~2400% cheaper at $0.20/1M; pay for Claude Opus 4.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Opus 4.5 | 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 | $25/1M tokens | $1.15/1M tokens |
| Provider routes | 6 tracked | 3 tracked |
| Shared benchmarks | 1 rows | SWE-bench Pro leader |
Decision tradeoffs
- Claude Opus 4.5 has broader tracked provider coverage for fallback and procurement flexibility.
- Claude Opus 4.5 uniquely exposes Code execution in local model data.
- Local decision data tags Claude Opus 4.5 for Coding, RAG, and Agents.
- Step 3.7 Flash holds a shared-benchmark lead on SWE-bench Pro, ahead by 14.5 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.
Claude Opus 4.5
$10,250
Cheapest tracked route/tier: Microsoft Foundry
Step 3.7 Flash
$448
Cheapest tracked route/tier: StepFun
Estimated monthly gap: $9,803. 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 $23.85/1M 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.
- Claude Opus 4.5 is $23.85/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Claude Opus 4.5 adds Code execution in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-11-01 | 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 | 2025-12 | - |
Pricing and availability
| Pricing attribute | Claude Opus 4.5 | Step 3.7 Flash |
|---|---|---|
| Input price | $5/1M tokens | $0.20/1M tokens |
| Output price | $25/1M tokens | $1.15/1M tokens |
| Providers |
Capabilities
| Capability | Claude Opus 4.5 | 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 | Claude Opus 4.5 | Step 3.7 Flash |
|---|---|---|
| SWE-bench Pro | 41.8 | 56.3 |
Deep dive
On shared benchmark coverage, SWE-bench Pro has Claude Opus 4.5 at 41.8 and Step 3.7 Flash at 56.3, with Step 3.7 Flash ahead by 14.5 points. The largest visible gap is 14.5 points on SWE-bench Pro, 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: Claude Opus 4.5. 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, Claude Opus 4.5 lists $5/1M input and $25/1M 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 $10.52 per million blended tokens. Availability is 6 providers versus 3, so concentration risk also matters.
Choose Claude Opus 4.5 when coding workflow support and broader provider choice 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, Claude Opus 4.5 or Step 3.7 Flash?
Step 3.7 Flash supports 256k tokens, while Claude Opus 4.5 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, Claude Opus 4.5 or Step 3.7 Flash?
Step 3.7 Flash is cheaper on tracked token pricing. Claude Opus 4.5 costs $5/1M input and $25/1M 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 Claude Opus 4.5 or Step 3.7 Flash open source?
Claude Opus 4.5 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, Claude Opus 4.5 or Step 3.7 Flash?
Both Claude Opus 4.5 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.
Which is better for multimodal input, Claude Opus 4.5 or Step 3.7 Flash?
Both Claude Opus 4.5 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.
Where can I run Claude Opus 4.5 and Step 3.7 Flash?
Claude Opus 4.5 is available on Microsoft Foundry, Anthropic, GCP Vertex AI, AWS Bedrock, and OpenRouter. Step 3.7 Flash is available on StepFun, OpenRouter, and NVIDIA NIM. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-29. Data sourced from public model cards and provider documentation.