BIG LAB UPDATES · 21 OCTOBER 2026
OpenAI's API can now keep your instructions cached for 12 hours
Developers using OpenAI's Responses API with GPT-5.6 or newer can now keep a long shared start to their prompts (instructions, tools and background context) cached for 12 hours instead of about 30 minutes. Writing to the 12-hour cache costs 2.5 times the normal input price, against 1.25 times for the short one, while reading from it stays cheap.
Why it mattersIf you run an agent or chatbot that reuses the same long instructions all day, with gaps of more than half an hour, this can cut costs and speed up replies. If it's used constantly or only now and then, it may not pay off, so ask your developer to check.
Sources
How we knowCompany figures are labelled as their own claims; anything we couldn't verify is labelled as a report or a claim.
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