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Anthropic vs StepFun
StepFun's Apache 2.0 Step 3.7 Flash costs $0.20 in and $1.15 out with vision and video input. Claude leads on hard reasoning and coding, and Haiku 5.5 lists lower.
By The Subconscious Team · Updated
Anthropic vs StepFun: key differences
StepFun is a Shanghai lab focused on cheap multimodal models. Step 3.7 Flash is a 198B mixture-of-experts vision-language model with only 11B active parameters, 256K context, selectable reasoning levels, tool use and structured outputs, priced at $0.20 in and $1.15 out on StepFun's API. It ships under Apache 2.0 and runs on vLLM and SGLang. Anthropic's cheapest model, Haiku 5.5, is $0.10 in and $0.50 out, and every tier offers 1M context, with no surcharge on the larger ones. StepFun's weights can be self-hosted. Claude's cannot.
The quality gap points the other way. StepFun trails frontier models on hard multimodal reasoning benchmarks, while Claude leads on real-world coding. StepFun's first-party inference is China-hosted with thin Western distribution and support, though OpenRouter carries the model. Cost-sensitive agents doing image and video understanding, or teams wanting a small-active-parameter model to self-host, get more from StepFun. Coding agents, long research runs and enterprise buyers needing major cloud procurement get more from Anthropic.
What Anthropic and StepFun do
Anthropic
Anthropic sells the Claude family of closed models through its own API, Amazon Bedrock, Google Vertex AI and Microsoft Foundry. The public lineup today runs from Claude Fable 5.1 at the top, released September 1, 2026, through Opus 5.5 ($4 in, $20 out) and Sonnet 5.5 ($2 in, $10 out) down to Haiku 5.5. List prices span a hundredfold range, from $10 in and $50 out on Fable to $0.10 in and $0.50 out on Haiku. All four tiers have a 1M token context window. The top three bill it at standard pricing, while Haiku 5.5 charges more past 100K.
Example models: Claude Fable 5.1, Claude Opus 5.5, Claude Haiku 5.5
Full Anthropic profileStepFun
StepFun is a Shanghai AI lab known for efficient multimodal models, with a mix of proprietary API models and open-weight releases. In September 2026 it launched Step 5 Preview, its new flagship for agentic work: a 600B-total, 27B-active mixture-of-experts model with 1M context and text and image input, which Artificial Analysis scores level with Kimi K3. Its cheaper workhorse, Step 3.7 Flash, came out in May 2026 as a 198B mixture-of-experts vision-language model with only 11B active parameters. It has 256K context, selectable reasoning levels, tool use and structured outputs, and it ships under Apache 2.0. StepFun's own API prices it at $0.20 in and $1.15 out per million tokens, and OpenRouter carries it too.
Example models: Step 5 Preview, Step 3.7 Flash
Full StepFun profileShould you choose Anthropic or StepFun?
Anthropic
Choose Anthropic for
- Hard coding and reasoning where quality decides
- Contexts beyond 256K tokens
- Western enterprise procurement
StepFun
Choose StepFun for
- Cheap vision and video understanding in agents
- Self-hosting an Apache 2.0 model with 11B active parameters
- Budget multimodal pipelines with structured outputs
Anthropic vs StepFun at a glance
| Attribute | Anthropic | StepFun |
|---|---|---|
| Model access | Closed | Open (Apache 2.0) and API models |
| Flagship models | Claude Fable 5.1, Opus 5.5, Sonnet 5.5, Haiku 5.5 | Step 5 Preview, Step 3.7 Flash |
| Speed | Fable is the slowest tier | ~128 tok/s on Step 3.7 Flash |
| Price | $0.10–$10 in, $0.50–$50 out per 1M | $0.20 in, $1.15 out (Step 3.7 Flash) |
| Customization | N/A | Open weights to fine-tune |
| Deployment | API, Bedrock, Vertex AI, Microsoft Foundry | First-party API, OpenRouter |
| Long context | 1M; Haiku 5.5 costs more past 100K | Up to 1M (Step 5 Preview); 256K on Step 3.7 Flash |
Frequently asked questions
What is the difference between Anthropic and StepFun?
StepFun's Apache 2.0 Step 3.7 Flash costs $0.20 in and $1.15 out with vision and video input. Claude leads on hard reasoning and coding, and Haiku 5.5 lists lower.
When should I choose Anthropic over StepFun?
Hard coding and reasoning where quality decides; Contexts beyond 256K tokens; Western enterprise procurement.
When should I choose StepFun over Anthropic?
Cheap vision and video understanding in agents; Self-hosting an Apache 2.0 model with 11B active parameters; Budget multimodal pipelines with structured outputs.
Is Anthropic or StepFun cheaper?
Anthropic: $0.10–$10 in, $0.50–$50 out per 1M. StepFun: $0.20 in, $1.15 out (Step 3.7 Flash). The cheaper choice depends on the model and workload.
Which has more context, Anthropic or StepFun?
Anthropic: 1M; Haiku 5.5 costs more past 100K. StepFun: Up to 1M (Step 5 Preview); 256K on Step 3.7 Flash.
Related comparisons
Running long-horizon agents?
If your agents run past 200K tokens, compare both against Subconscious. Our inference stack treats a long-horizon trace as the primary workload, so speed, cost, and accuracy hold up deep into the trace.