Claude Opus 4.5 vs GPT-5.3-Codex
Claude Opus 4.5 (2025) and GPT-5.3-Codex (2026) are agentic coding models from Anthropic and OpenAI. 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 comparison covers specs, pricing, capabilities, benchmarks, provider availability, and production fit.
GPT-5.3-Codex is ~186% cheaper at $1.75/1M; pay for Claude Opus 4.5 only for coding workflow support.
Decision scorecard
Local evidence first| Signal | Claude Opus 4.5 | GPT-5.3-Codex |
|---|---|---|
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200K | 400K |
| Cheapest output | $25/1M tokens | $14/1M tokens |
| Provider routes | 5 tracked | 2 tracked |
| Shared benchmarks | 2 rows | SWE-bench Verified leader |
Decision tradeoffs
- Claude Opus 4.5 has broader tracked provider coverage for fallback and procurement 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.
- GPT-5.3-Codex leads the largest shared benchmark signal on SWE-bench Verified 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.
- 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 prices on this page.
Claude Opus 4.5
$10,250
Cheapest tracked route: Microsoft Foundry
GPT-5.3-Codex
$4,900
Cheapest tracked route: OpenRouter
Estimated monthly gap: $5,350. Batch, cache, and negotiated pricing are excluded from this local estimate.
Switch friction
- Provider overlap exists on OpenRouter; 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.
- Provider overlap exists on OpenRouter; 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.
- Claude Opus 4.5 adds Multimodal in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-11-01 | 2026-02-05 |
| Context window | 200K | 400K |
| Parameters | — | — |
| Architecture | decoder only | decoder only |
| License | Proprietary | Proprietary |
| Knowledge cutoff | 2025-12 | 2025-08 |
Pricing and availability
| Pricing attribute | Claude Opus 4.5 | GPT-5.3-Codex |
|---|---|---|
| Input price | $5/1M tokens | $1.75/1M tokens |
| Output price | $25/1M tokens | $14/1M tokens |
| Providers |
Capabilities
| Capability | Claude Opus 4.5 | GPT-5.3-Codex |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | No |
| Reasoning | Yes | Yes |
| Function calling | Yes | Yes |
| Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
Benchmarks
| Benchmark | Claude Opus 4.5 | GPT-5.3-Codex |
|---|---|---|
| SWE-bench Verified | 80.9 | 85.0 |
| SWE-bench Pro | 41.8 | 56.8 |
Deep dive
On shared benchmark coverage, SWE-bench Verified has Claude Opus 4.5 at 80.9 and GPT-5.3-Codex at 85, with GPT-5.3-Codex ahead by 4.1 points; SWE-bench Pro has Claude Opus 4.5 at 41.8 and GPT-5.3-Codex at 56.8, with GPT-5.3-Codex ahead by 15 points. The largest visible gap is 15 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 multimodal input: Claude Opus 4.5. Both models share vision, reasoning mode, function calling, and tool use, 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, while GPT-5.3-Codex lists $1.75/1M input and $14/1M output tokens on the cheapest tracked provider. A 70/30 input-output blend puts GPT-5.3-Codex lower by about $5.58 per million blended tokens. Availability is 5 providers versus 2, so concentration risk also matters.
Choose Claude Opus 4.5 when coding workflow support and broader provider choice are central to the workload. Choose GPT-5.3-Codex when coding workflow support, 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 GPT-5.3-Codex?
GPT-5.3-Codex supports 400K 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 GPT-5.3-Codex?
GPT-5.3-Codex is cheaper on tracked token pricing. Claude Opus 4.5 costs $5/1M input and $25/1M output tokens. GPT-5.3-Codex costs $1.75/1M input and $14/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Opus 4.5 or GPT-5.3-Codex open source?
Claude Opus 4.5 is listed under Proprietary. GPT-5.3-Codex 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 GPT-5.3-Codex?
Both Claude Opus 4.5 and GPT-5.3-Codex expose vision. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface. Use this as a quick comparison signal, then confirm the provider-specific limits before committing to production.
Which is better for multimodal input, Claude Opus 4.5 or GPT-5.3-Codex?
Claude Opus 4.5 has the clearer documented multimodal input signal in this comparison. If multimodal input is mission-critical, validate it against the provider endpoint because model-level support and API-level exposure can differ.
Where can I run Claude Opus 4.5 and GPT-5.3-Codex?
Claude Opus 4.5 is available on Microsoft Foundry, Anthropic, GCP Vertex AI, AWS Bedrock, and OpenRouter. GPT-5.3-Codex is available on OpenRouter and OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-05-19. Data sourced from public model cards and provider documentation.