openai.internal.default_cache_breakpoint

The `prompt_cache_breakpoint` a `${cache()}` sends to `model`: `{"mode": "explicit"}`, the only value the field takes, or null for a model that rejects the field (GPT-5.5 and earlier), where a `${cache()}` sends nothing. The value marks one position; it is not the request-level `prompt_cache_options.mode`, so the request stays in OpenAI's implicit mode.

Reference version

Signature

function openai.internal.default_cache_breakpoint(model: string) -> baml.json.json throws never

The prompt_cache_breakpoint a ${cache()} sends to model: {"mode": "explicit"}, the only value the field takes, or null for a model that rejects the field (GPT-5.5 and earlier), where a ${cache()} sends nothing. The value marks one position; it is not the request-level prompt_cache_options.mode, so the request stays in OpenAI's implicit mode.

Source:<builtin>/openai/ns_internal/chat.bamlbytes 4916–5106