# Cache writes on every request, reads on none: move the breakpoint
## Symptom
`cache_creation_input_tokens` is nonzero every request, `cache_read_input_tokens` is 0 every request. You pay the 25 percent write surcharge every time and never get a read.
## Confirm the cause
Look at the block carrying `cache_control`. If anything in the prefix up to and including that block differs between requests, a timestamp, a request id, the new user message, the prefix hash differs and the lookback finds nothing. The docs call this out explicitly: cache writes happen only at your breakpoint, and the lookback only finds entries prior requests wrote, not stable content sitting behind the breakpoint.
## Fix
1. Move `cache_control` to the last block whose prefix is identical across the requests you want to share the cache, usually the end of the static instructions or context, not the varying block.
2. If you used automatic caching (top-level `cache_control`), it lands on the last cacheable block, which is often the varying one; switch to an explicit breakpoint on the static prefix instead.
3. Keep the breakpoint byte-identical: any change at or before it produces a different hash.
## Verify
The next identical-prefix request returns nonzero `cache_read_input_tokens` and near-zero `cache_creation_input_tokens`. Two consecutive requests with the same static prefix are the test.