LLM Reference

Claude Sonnet 4.5 vs o3 Mini

Claude Sonnet 4.5 (2025) and o3 Mini (2025) are frontier-tier reasoning models from Anthropic and OpenAI. Claude Sonnet 4.5 ships a 200k-token context window, while o3 Mini ships a 200k-token context window. On MMLU PRO, Claude Sonnet 4.5 leads by 6.9 pts. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.

Claude Sonnet 4.5 is safer overall; choose o3 Mini when coding workflow support matters.

Decision scorecard

Local evidence first
SignalClaude Sonnet 4.5o3 Mini
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentsreasoning-heavy apps, tool-calling agents, and provider-routed production
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window200k200k
Cheapest output$15/1M tokens$4.40/1M tokens
Provider routes8 tracked4 tracked
Shared benchmarksMMLU PRO leader3 shared

Decision tradeoffs

Choose Claude Sonnet 4.5 when...
  • Claude Sonnet 4.5 holds a shared-benchmark lead on MMLU PRO, ahead by 6.9 points.
  • Claude Sonnet 4.5 has broader tracked provider coverage for fallback and route flexibility.
  • Claude Sonnet 4.5 uniquely exposes Vision and Multimodal in local model data.
  • Local decision data tags Claude Sonnet 4.5 for Coding, RAG, and Agents.
Choose o3 Mini when...
  • o3 Mini has the lower cheapest tracked output price at $4.40/1M tokens.
  • o3 Mini uniquely exposes Code execution in local model data.
  • Local decision data tags o3 Mini 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.

Lower estimate o3 Mini

Claude Sonnet 4.5

$6,150

Cheapest tracked route/tier: Microsoft Foundry

o3 Mini

$1,980

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $4,170. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Sonnet 4.5 -> o3 Mini
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • o3 Mini is $10.60/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Vision and Multimodal before moving production traffic.
  • o3 Mini adds Code execution in local capability data.
o3 Mini -> Claude Sonnet 4.5
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • Claude Sonnet 4.5 is $10.60/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Code execution before moving production traffic.
  • Claude Sonnet 4.5 adds Vision and Multimodal in local capability data.

Specs

Specification
Released2025-09-292025-01-31
Context window200k200k
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-122025-04

Pricing and availability

Pricing attributeClaude Sonnet 4.5o3 Mini
Input price
0-200,001t
$3/1M tokens
200,001t+
$6/1M tokens
$1.10/1M tokens
Output price
0-200,001t
$15/1M tokens
200,001t+
$22.50/1M tokens
$4.40/1M tokens
Providers
Microsoft FoundryAnthropicSnowflake CortexGCP Vertex AIAWS BedrockReplicate API
OpenRouterAzure OpenAIOpenAI APIVercel AI Gateway

Capabilities

CapabilityClaude Sonnet 4.5o3 Mini
VisionYesNo
MultimodalYesNo
ReasoningYesYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionNoYes
IDE integrationNoNo
Computer useNoNo
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Sonnet 4.5o3 Mini
MMLU PRO86.079.1
SWE-bench Verified77.249.3
Google-Proof Q&A83.479.7

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