Claude Opus 4.5 vs GPT-5.5 Instant
Claude Opus 4.5 (2025) and GPT-5.5 Instant (2026) are frontier reasoning models from Anthropic and OpenAI. Claude Opus 4.5 ships a 200K-token context window, while GPT-5.5 Instant ships a 400K-token context window. On LMArena Text Arena - Creative Writing, Claude Opus 4.5 leads by 25 pts. On pricing, both list $5/1M input tokens on the cheapest listed route. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
Pick Claude Opus 4.5 for general evaluation; GPT-5.5 Instant is better when coding workflow support matters more.
Decision scorecard
Local evidence first| Signal | Claude Opus 4.5 | GPT-5.5 Instant |
|---|---|---|
| Best for | reasoning-heavy apps, multimodal apps, and tool-calling agents | multimodal apps and tool-calling agents |
| Decision fit | Coding, RAG, and Agents | Coding, RAG, and Agents |
| Context window | 200K | 400K |
| Cheapest output | $25/1M tokens | $30/1M tokens |
| Provider routes | 6 tracked | 1 tracked |
| Shared benchmarks | LMArena Text Arena - Creative Writing leader | 3 shared |
Decision tradeoffs
- Claude Opus 4.5 holds a shared-benchmark lead on LMArena Text Arena - Creative Writing, ahead by 25 points.
- Claude Opus 4.5 has the lower cheapest tracked output price at $25/1M tokens.
- Claude Opus 4.5 has broader tracked provider coverage for fallback and route flexibility.
- Claude Opus 4.5 uniquely exposes Reasoning in local model data.
- Local decision data tags Claude Opus 4.5 for Coding, RAG, and Agents.
- GPT-5.5 Instant holds a shared-benchmark lead on Chatbot Arena, ahead by 7 points.
- GPT-5.5 Instant has the larger context window for long prompts, retrieval packs, or transcript analysis.
- Local decision data tags GPT-5.5 Instant 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.
Claude Opus 4.5
$10,250
Cheapest tracked route/tier: Microsoft Foundry
GPT-5.5 Instant
$11,500
Cheapest tracked route/tier: OpenAI API
Estimated monthly gap: $1,250. Batch, cache, alternate speed tiers, and negotiated pricing are excluded from this local estimate.
Switch friction
- No overlapping tracked provider route is sourced for Claude Opus 4.5 and GPT-5.5 Instant; plan for SDK, billing, or endpoint changes.
- GPT-5.5 Instant is $5/1M tokens higher on cheapest tracked output pricing, so quality gains need to justify the spend.
- Check replacement coverage for Reasoning before moving production traffic.
- No overlapping tracked provider route is sourced for GPT-5.5 Instant and Claude Opus 4.5; plan for SDK, billing, or endpoint changes.
- Claude Opus 4.5 is $5/1M tokens lower on cheapest tracked output pricing before cache, batch, or negotiated discounts.
- Claude Opus 4.5 adds Reasoning in local capability data.
Specs
| Specification | ||
|---|---|---|
| Released | 2025-11-01 | 2026-05-05 |
| Context window | 200K | 400K |
| Parameters | — | — |
| Architecture | Decoder Only | Decoder Only |
| License | Proprietary | Proprietary |
| Openness | Proprietary | Proprietary |
| Weights | Not released | Not released |
| Code | Unknown | Unknown |
| Commercial use | Restricted | Restricted |
| Knowledge cutoff | 2025-12 | 2025-08 |
Pricing and availability
| Pricing attribute | Claude Opus 4.5 | GPT-5.5 Instant |
|---|---|---|
| Input price | $5/1M tokens | $5/1M tokens |
| Output price | $25/1M tokens | $30/1M tokens |
| Providers |
Capabilities
| Capability | Claude Opus 4.5 | GPT-5.5 Instant |
|---|---|---|
| Vision | Yes | Yes |
| Multimodal | Yes | Yes |
| Reasoning | Yes | No |
| JSON / Tool use | Yes | Yes |
| Structured outputs | Yes | Yes |
| Code execution | Yes | Yes |
| IDE integration | No | No |
| Computer use | No | No |
| Parallel agents | No | No |
Benchmarks
| Benchmark | Claude Opus 4.5 | GPT-5.5 Instant |
|---|---|---|
| LMArena Text Arena - Creative Writing | 1443.0 | 1418.0 |
| Chatbot Arena | 1466.0 | 1473.0 |
| MMMU Pro | 73.9 | 76.0 |
Deep dive
On shared benchmark coverage, LMArena Text Arena - Creative Writing has Claude Opus 4.5 at 1443 and GPT-5.5 Instant at 1418, with Claude Opus 4.5 ahead by 25 points; Chatbot Arena has Claude Opus 4.5 at 1466 and GPT-5.5 Instant at 1473, with GPT-5.5 Instant ahead by 7 points; MMMU Pro has Claude Opus 4.5 at 73.9 and GPT-5.5 Instant at 76, with GPT-5.5 Instant ahead by 2.1 points. The largest visible gap is 25 points on LMArena Text Arena - Creative Writing, 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 reasoning mode: Claude Opus 4.5. Both models share vision, multimodal input, JSON / Tool use, and JSON / 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 on the cheapest listed provider, while GPT-5.5 Instant lists $5/1M input and $30/1M output tokens on the cheapest listed provider. A 70/30 input-output blend puts Claude Opus 4.5 lower by about $1.50 per million blended tokens. Availability is 6 providers versus 1, 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-5.5 Instant when coding workflow support and larger context windows 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-5.5 Instant?
GPT-5.5 Instant 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-5.5 Instant?
Claude Opus 4.5 is cheaper on listed token pricing. Claude Opus 4.5 costs $5/1M input and $25/1M output tokens. GPT-5.5 Instant costs $5/1M input and $30/1M output tokens. Provider discounts or batch pricing can still change the final bill.
Is Claude Opus 4.5 or GPT-5.5 Instant open source?
Claude Opus 4.5 is listed under Proprietary. GPT-5.5 Instant 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-5.5 Instant?
Both Claude Opus 4.5 and GPT-5.5 Instant 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-5.5 Instant?
Both Claude Opus 4.5 and GPT-5.5 Instant expose multimodal input. The better choice depends on benchmark fit, context budget, pricing, and whether your provider route exposes the same capability surface.
Where can I run Claude Opus 4.5 and GPT-5.5 Instant?
Claude Opus 4.5 is available on Microsoft Foundry, Anthropic, GCP Vertex AI, AWS Bedrock, and OpenRouter. GPT-5.5 Instant is available on OpenAI API. Provider coverage can affect latency, region availability, compliance posture, and fallback options.
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Last reviewed: 2026-10-17. Data sourced from public model cards and provider documentation.