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 MMMU Pro, GPT-5.5 Instant leads by 2.1 pts. On pricing, both list $5/1M input tokens on the cheapest tracked route. This comparison covers specs, pricing, API access, capabilities, benchmarks, input and output token costs, and production fit for coding and agent workloads.
GPT-5.5 Instant is safer overall; choose Claude Opus 4.5 when coding workflow support matters.
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 | 1 shared | MMMU Pro leader |
Decision tradeoffs
- 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 MMMU Pro, ahead by 2.1 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 | Commercial use: conditional | Commercial use: conditional |
| 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 |
|---|---|---|
| MMMU Pro | 73.9 | 76.0 |
Continue comparing
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Last reviewed: 2026-07-26. Data sourced from public model cards and provider documentation.