Claude Code's prompt suggestions do a full-context cache read.

A user instrumenting Claude Code measured that the greyed-out inline suggestions, the ones proposing things like "commit and push," trigger a cache read of the entire context on a full-size model. Median measured cost was 91% of the corresponding real prompt, and at high context lengths the total reached about 10% of a weekly Fable limit. The author is careful: turning it off doesn't double your usage, since tool calls dominate. He also flags that compacting after the cache expires is separately expensive. Single-source and self-instrumented, but the methodology is stated and the setting is one toggle.