Claude Opus 4.5 vs GPT-5.3-Codex

Claude Opus 4.5 (2025) and GPT-5.3-Codex (2026) compare a standalone API model against a coding-specialized model. Claude Opus 4.5 ships a 200k-token context window, while GPT-5.3-Codex ships a 400k-token context window. On SWE-bench Verified, GPT-5.3-Codex leads by 4.1 pts. On pricing, GPT-5.3-Codex costs $1.75/1M input tokens versus $5/1M for the alternative. This page treats the result as workflow and deployment fit, not a universal model winner.

Treat this as a product-type comparison: Claude Opus 4.5 is standalone API model, while GPT-5.3-Codex is coding-specialized model. Choose based on workflow fit before reading any benchmark or price row as decisive.

Decision scorecard

Local evidence first
SignalClaude Opus 4.5GPT-5.3-Codex
Product typeStandalone API modelCoding-specialized model
Best forreasoning-heavy apps, multimodal apps, and tool-calling agentscustom coding agents, code generation, and tool loops
Decision fitCoding, RAG, and AgentsCoding, RAG, and Agents
Context window200k400k
Cheapest output$25/1M tokens$14/1M tokens
Provider routes6 tracked3 tracked
Shared benchmarks2 sharedSWE-bench Verified leader

Decision tradeoffs

Choose Claude Opus 4.5 when...
  • Claude Opus 4.5 has broader tracked provider coverage for fallback and route flexibility.
  • Claude Opus 4.5 uniquely exposes Multimodal in local model data.
  • Local decision data tags Claude Opus 4.5 for Coding, RAG, and Agents.
Choose GPT-5.3-Codex when...
  • GPT-5.3-Codex holds a shared-benchmark lead on SWE-bench Verified, ahead by 4.1 points.
  • GPT-5.3-Codex has the larger context window for long prompts, retrieval packs, or transcript analysis.
  • GPT-5.3-Codex has the lower cheapest tracked output price at $14/1M tokens.
  • GPT-5.3-Codex uniquely exposes Computer use in local model data.
  • Local decision data tags GPT-5.3-Codex 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 GPT-5.3-Codex

Claude Opus 4.5

$10,250

Cheapest tracked route/tier: Microsoft Foundry

GPT-5.3-Codex

$4,900

Cheapest tracked route/tier: OpenRouter

Estimated monthly gap: $5,350. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.

Switch friction

Claude Opus 4.5 -> GPT-5.3-Codex
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • GPT-5.3-Codex is $11/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
  • Check replacement coverage for Multimodal before moving production traffic.
  • GPT-5.3-Codex adds Computer use in local capability data.
GPT-5.3-Codex -> Claude Opus 4.5
  • Provider overlap exists on OpenRouter and Vercel AI Gateway; start route-level A/B tests there.
  • Claude Opus 4.5 is $11/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
  • Check replacement coverage for Computer use before moving production traffic.
  • Claude Opus 4.5 adds Multimodal in local capability data.

Specs

Specification
Released2025-11-012026-02-05
Context window200k400k
Parameters——
ArchitectureDecoder OnlyDecoder Only
LicenseProprietaryProprietary
OpennessProprietaryProprietary
WeightsNot releasedNot released
CodeUnknownUnknown
Commercial useCommercial use: conditionalCommercial use: conditional
Knowledge cutoff2025-122025-08

Pricing and availability

Pricing attributeClaude Opus 4.5GPT-5.3-Codex
Input price$5/1M tokens$1.75/1M tokens
Output price$25/1M tokens$14/1M tokens
Providers
Microsoft FoundryAnthropicGCP Vertex AIAWS BedrockOpenRouterVercel AI Gateway
OpenRouterOpenAI APIVercel AI Gateway

Capabilities

CapabilityClaude Opus 4.5GPT-5.3-Codex
VisionYesYes
MultimodalYesNo
ReasoningYesYes
JSON / Tool useYesYes
Structured outputsYesYes
Code executionYesYes
IDE integrationNoNo
Computer useNoYes
Parallel agentsNoNo

Benchmarks

BenchmarkClaude Opus 4.5GPT-5.3-Codex
SWE-bench Verified80.985.0
SWE-bench Pro41.856.8

Continue comparing

Model pages
Labs and families
Related comparisons

Popular comparisons for Claude Opus 4.5

Popular comparisons for GPT-5.3-Codex

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