Anthropic Claude Opus 5 (200k) vs OpenAI GPT-5.6 Codex (1M)
Side-by-side comparison of pricing, context window, capabilities, and a real-cost sample workload.
Anthropic Claude Opus 5 (200k)
OpenAI GPT-5.6 Codex (1M)
Detailed Comparison
| Dimension | Anthropic Claude Opus 5 (200k) | OpenAI GPT-5.6 Codex (1M) |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Context window Winner | 200K | 1M |
| Input price ($/1M) TieTie | $5.00 | $5.00 |
| Output price ($/1M) Winner | $25.00 | $30.00 |
| Sample workload cost Winner 1M input + 500K output tokens | $17.50 | $20.00 |
| Released TieTie | 2026-07 | 2026-07 |
| Tokenizer | claude-4 | o200k_base |
The verdict
On the dimensions we measured, Anthropic Claude Opus 5 (200k) wins more often - particularly on cost-effectiveness for a typical 1M+0.5M workload.
Anthropic Claude Opus 5 (200k) - Key features
Anthropic's flagship Opus-class model for July 2026. Opus 5 pairs Mythos-class reasoning with the Opus price point, adds adaptive effort control and a hardened long-horizon agent loop that holds context across day-long tasks.
- Adaptive effort control (low to max)
- Best-in-class agentic coding
- Compaction-aware 200K context
- Native tool search and skills
- Interleaved thinking with tool use
OpenAI GPT-5.6 Codex (1M) - Key features
The Codex-tuned build of GPT-5.6 for the Codex CLI, IDE extension and cloud agents. Optimised for long autonomous coding sessions, patch generation and test repair rather than open-ended chat.
- Tuned for agentic coding
- Long autonomous sessions
- Patch and diff generation
- ~1M token context window
- Sandboxed execution support
How to choose
- Pick the cheaper model if your workload is mostly straightforward classification, extraction, or summarization.
- Pick the bigger context if you process long documents, large codebases, or multi-document research.
- Pick the more recent release if you need state-of-the-art reasoning quality and don't mind paying a bit more.
- Use both via a routing layer - send simple tasks to the cheaper one and complex tasks to the smarter one. This is the highest-ROI optimization in production AI.
Estimate the real cost of either model for your prompts using our Token Calculator.