How to Diagnose OpenAI Prompt Cache Misses in the Responses API: Baselines, Reasons, Fixes, and Cost Checks
What changed on September 8: Prompt Cache Diagnostics is now generally available OpenAI’s September 8, 2026 API changelog states that Prompt Cache Diagnostics is now generally available in the Responses API for GPT-5.6 and later supported models. The feature is designed for a narrow but operationally important task: compare cache…
