LLM Reference

Claude Sonnet 4.5 vs StepFun Step-2

Claude Sonnet 4.5 (2025) and StepFun Step-2 (2025) are frontier reasoning models from Anthropic and StepFun. Claude Sonnet 4.5 ships a 200k-token context window, while StepFun Step-2 ships a 128k-token context window. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads. It focuses on practical selection signals rather than broad model-family marketing.

StepFun Step-2 is safer overall; choose Claude Sonnet 4.5 when reasoning depth matters.

Decision scorecard

Local evidence first
SignalClaude Sonnet 4.5StepFun Step-2
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsgeneral production evaluation
Decision fitCoding, RAG, and AgentsLong context
Context window200k128k
Cheapest output$15/1M tokens-
Provider routes8 tracked0 tracked
Shared benchmarks0 shared0 shared

Decision tradeoffs

Choose Claude Sonnet 4.5 when...
  • Claude Sonnet 4.5 has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • Claude Sonnet 4.5 has broader tracked provider coverage for fallback and route flexibility.
  • Claude Sonnet 4.5 uniquely exposes Vision, Multimodal, and Reasoning in local model data.
  • Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.
Choose StepFun Step-2 when...
  • Local decision data tags StepFun Step-2 for Long context.

Monthly cost at traffic

Estimate token spend from the cheapest tracked input and output route or tier on this page.

Claude Sonnet 4.5

$6,150

Cheapest tracked route/tier: Microsoft Foundry

StepFun Step-2

Unavailable

No complete token price in local provider data

Cost delta unavailable until both models have sourced input and output token prices.

Switch friction

Claude Sonnet 4.5 -> StepFun Step-2
  • No overlapping tracked provider route is sourced for Claude Sonnet 4.5 and StepFun Step-2; plan for SDK, billing, or endpoint changes.
  • Check replacement coverage for Vision, Multimodal, and Reasoning before moving production traffic.
StepFun Step-2 -> Claude Sonnet 4.5
  • No overlapping tracked provider route is sourced for StepFun Step-2 and Claude Sonnet 4.5; plan for SDK, billing, or endpoint changes.
  • Claude Sonnet 4.5 adds Vision, Multimodal, and Reasoning in local capability data.

Specs

Specification
Released2025-09-292025-10-15
Context window200k128k
Parameters—1T (MoE)*
ArchitectureDecoder Only-
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-12-

Pricing and availability

Pricing attributeClaude Sonnet 4.5StepFun Step-2
Input price
0-200,001t
$3/1M tokens
200,001t+
$6/1M tokens
-
Output price
0-200,001t
$15/1M tokens
200,001t+
$22.50/1M tokens
-
Providers
Microsoft FoundryAnthropicSnowflake CortexGCP Vertex AIAWS BedrockReplicate API
-

Capabilities

CapabilityClaude Sonnet 4.5StepFun Step-2
VisionYesNo
MultimodalYesNo
ReasoningYesNo
JSON / Tool useYesNo
Structured outputsYesNo
Code executionNoNo
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

No shared benchmark scores are currently available for this pair.

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Model pages
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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.