prompt-caching
OpenAI ships GPT-6 Sol and Luna, making cache economics part of the model product News
OpenAI released GPT-6 Sol and Luna as cheaper API and product tiers, with cache controls that the company says cut GitHub's freshly processed prompt tokens by more than half.
Anthropic's cheaper model is not cheaper - its cache is News
Claude Fable 5.1 kept the same $10 and $50 per-million sticker price as Fable 5, but cache reads dropped to a quarter of the old rate, which is why one developer's 22,022 API calls got about 31% cheaper per prompt while using 31% more tokens.
Prompt Caching: Why AI Agents Pay Once to Read, Then Read for Pennies Lesson
Prompt caching lets an AI provider store the processed form of a repeated chunk of text -- like a long system prompt -- so it can be reused across requests at a fraction of the cost, instead of being re-processed every time.
Anthropic prompt caching pricing reference Tool
Anthropic's documentation of how cached tokens are billed: cache hits at 10% of standard input, five-minute writes at 1.25 times base input, one-hour writes at 2 times. This is the page that explains why Claude Fable 5.1 can be substantially cheaper per prompt for long agent sessions while costing exactly the same for one-shot calls.