What Claude Opus 4.7 actually is (and what makes it different)
Opus 4.7 is the flagship of Anthropic's 'Claude 4' generation, succeeding Opus 4.5 (mid-2025) and Opus 4 (early 2025). It is the high end of a three-tier menu (Opus, Sonnet, Haiku) that Anthropic has maintained since Claude 3 in 2024 — Opus for hardest tasks at highest price, Sonnet for the production sweet spot, Haiku for cost-sensitive volume.
What makes Opus 4.7 different from GPT-5: stronger long-form writing voice, more disciplined instruction following on complex multi-step prompts, more aggressive prompt caching (90% off the cached read portion, vs OpenAI's also-90% but with different cache eligibility rules), native XML-tag structuring as the canonical prompt format, and extended thinking — Anthropic's name for explicit, configurable chain-of-thought reasoning that you can budget in tokens per call.
Where GPT-5 collapsed reasoning into a single `reasoning_effort` parameter, Anthropic exposes 'extended thinking' as a separate `thinking` block in the API: you set a `budget_tokens` (e.g. 5,000) and Opus 4.7 burns up to that many thinking tokens before producing the visible answer. Like reasoning tokens on GPT-5, thinking tokens bill at the output rate.