Codex on AWS bedrock bug causing 10x charges

Native Codex CLI v0.147.0 on Amazon Bedrock Mantle cannot enable GPT-5.6 Sol’s explicit prompt-caching; cache-write tokens comprised roughly 85% of model spend from 2026-08-05 to 08-08, with 6.709 M cache-write input tokens across 76 requests (≈88 K per request). The provider lacks the required prompt_cache_options and prompt_cache_breakpoint fields, blocking configuration of explicit-cache mode, and the issue request adds serialization support, a typed breakpoint field, capability gating, and telemetry for cache reads and writes.