GPT-5.6 Luna or Claude Sonnet 5.5?
Choose GPT-5.6 Luna when high-volume extraction, classification and routine agent tasks is the closer match. Choose Claude Sonnet 5.5 when full-stack software development, automated ui testing and production agent workflows matters more. Test both on the same real tasks before moving a production workflow.
High-volume extraction, classification and routine agent tasks
Full-stack software development, automated UI testing and production agent workflows
GPT-5.6 Luna
GPT-5.6 model optimized for cost-sensitive, high-volume workloads.
Official specification ↗Claude Sonnet 5.5
Anthropic's workhorse model with enhanced computer use and sub-second token generation.
Official specification ↗Side-by-side comparison
| Category | GPT-5.6 Luna | Claude Sonnet 5.5 |
|---|---|---|
| Provider | OpenAI | Anthropic |
| Type | Model · Reasoning model | Model · Balanced reasoning model |
| Pricing summary | $0.20 input, $0.02 cached input and $1.20 output per 1M tokens | $2 input, $0.20 cache read and $10 output per 1M tokens |
| Input price | $0.20 / 1M tokens | $2 / 1M tokens |
| Cached input | $0.02 / 1M tokens | $0.20 / 1M tokens |
| Output price | $1.20 / 1M tokens | $10 / 1M tokens |
| Context window | 1.05M tokens | 500K tokens |
| Maximum output | 128K tokens | 128K tokens |
| Knowledge cutoff | February 16, 2026 | August 2026 |
| Reasoning | none, low, medium, high, xhigh, max | Adaptive thinking with custom effort |
| Relative speed | Fast / cost optimized | High throughput |
| Input modalities | Text and image | Text and image |
| Output modalities | Text | Text |
| Tools and integrations | Functions, web search, file search, computer use and supported Responses API tools | Claude API tool use, desktop computer use, Claude Code |
| API / access | v1/responses, v1/chat/completions and v1/batch | Claude Messages API |
| Best fit | High-volume extraction, classification and routine agent tasks | Full-stack software development, automated UI testing and production agent workflows |
| Company | OpenAI | Anthropic |
| Product category | Model · Reasoning model | Model · Balanced reasoning model |
| Current pricing note | $0.20 input, $0.02 cached input and $1.20 output per 1M tokens | $2 input, $0.20 cache read and $10 output per 1M tokens |
| Best suited to | High-volume extraction, classification and routine agent tasks | Full-stack software development, automated UI testing and production agent workflows |
| Key capabilities | 1.05M context; 128K maximum output; Vision input; Responses API tools | Sub-second latency; Enhanced desktop computer use; 500K context; Claude Code default |
| Last verified | 2026-09-08 | 2026-10-15 |
| Official product source | https://developers.openai.com/api/docs/models/gpt-5.6-luna | https://platform.claude.com/docs/en/models/sonnet-5-5/overview |
How we reached this verdict
We looked at the things that affect everyday use: what each product can do, how its plans are structured, where it fits into your existing workflow, and what the provider currently documents. Benchmark results are useful context, but they are not a universal winner score because test settings and tools vary.
Common questions
GPT-5.6 Luna or Claude Sonnet 5.5: which should I choose?
Choose GPT-5.6 Luna for high-volume extraction, classification and routine agent tasks. Choose Claude Sonnet 5.5 for full-stack software development, automated ui testing and production agent workflows. Validate the decision with your own prompts and total task cost.
Is GPT-5.6 Luna cheaper than Claude Sonnet 5.5?
Pricing units can differ. GPT-5.6 Luna: $0.20 input, $0.02 cached input and $1.20 output per 1M tokens. Claude Sonnet 5.5: $2 input, $0.20 cache read and $10 output per 1M tokens. Check tool charges, plan limits, caching and long-context rules before comparing totals.
Which is better for coding and agent work?
Capability depends on the selected product surface, tools and harness. GPT-5.6 Luna is positioned for high-volume extraction, classification and routine agent tasks; Claude Sonnet 5.5 is positioned for full-stack software development, automated ui testing and production agent workflows. Run the same repository task on both.
How do their context windows compare?
GPT-5.6 Luna lists 1.05M tokens; Claude Sonnet 5.5 lists 500K tokens. A larger limit does not by itself guarantee better retrieval or lower cost.
Official sources
Use these provider pages to confirm current features, pricing and availability.
AI tools change quickly. We checked this page on 2026-09-08. Before you subscribe, confirm the latest price, regional availability and usage limits on the provider website.