Does cached content still count?
API cache pricing and subscription allowances are different systems. Do not transfer a discount from one to the other.
Sources reviewed:
API cache pricing and subscription allowances are different systems. Do not transfer a discount from one to the other.
Codex / OpenAI
API prompt caching can reduce input cost for repeated prefixes. It does not establish a fixed Codex subscription discount.
Claude
Reusing cached project content helps conserve allowance; new or uncached material still contributes.
In practice
Keep reusable context stable. Check the usage and billing rules for the product you actually use.