GPT-5.6 Terra API Pricing & Cost Calculator

How this is calculated

GPT-5.6 Terra is priced at $2.00 per million input tokens and $12.00 per million output tokens at OpenAI's published list price, with a 90% prompt caching discount ($0.20 per million). That puts it 2x below GPT-5.6 Sol on input and 10x above GPT-5.6 Luna on input. OpenAI's standard 50% batch discount applies via the Batch API ($1.00 per million inputs, $6.00 per million outputs). Note: OpenRouter currently runs a limited-time 50% discount that can show Terra at $1/$6 in live calculators.

Verdict

GPT-5.6 Terra lands at $2/M input and $12/M output, with a 90% cache discount dropping input to $0.20/M and the 50% batch discount (via OpenAI's Batch API) cutting both to $1/M input and $6/M output. The 2x savings against GPT-5.6 Sol on input and the 10x premium over Luna make Terra the natural default for general production traffic where frontier-tier reasoning actually matters. The cache discount is what carries the long-context case: an agentic loop with a stable 100K system prompt budgeted at the cached input rate is small enough that you keep Terra on for the loop instead of cascading down to a cheaper model.