The whole hunk
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269269 "cache_write_tokens": 352000,
270270 "miss_recache_tokens": 310200,
271271 "last_miss_at": 1738425230,
272 "last_miss_cause": {
273 "causes": ["tools_changed"],
274 "tools_added": 2,
275 "tools_removed": 0
276 },
277 "miss_causes": {
278 "tools_changed": 2
279 },
272280 "recache_tokens_if_cold": 45000
273281 },
274282 "fast_mode": false,
from line 386
378386| `cache_write_tokens` | All tokens written to the cache this session, the first request's initial write included |
379387| `miss_recache_tokens` | Tokens written to the cache by the requests counted as misses |
380388| `last_miss_at` | When the last miss happened, in epoch seconds. `null` while the session has no misses |
389| `last_miss_cause` | What Claude Code identified as the likely cause of the last miss, described under [Last miss cause](#last-miss-cause). Requires Claude Code v2.1.260 or later |
390| `miss_causes` | How many of this session's diagnosed misses had each cause, keyed by the same cause names as `last_miss_cause`. Requires Claude Code v2.1.260 or later |
381391| `recache_tokens_if_cold` | Tokens the next request re-caches if the cache has gone cold by then. `null` right after a compaction or a clearing of old tool results, until the next request records the rewritten conversation's size |
382392
383393Claude Code shows the same statistics in the terminal, on the [`/usage` command's `Prompt cache (main)` line](/docs/en/costs#prompt-cache-statistics).
394
395<h4 id="last-miss-cause">
396 Last miss cause
397</h4>
398
399The `last_miss_cause` object reports what Claude Code identified as the likely cause of the most recent miss. Its `causes` array holds one or more cause names, such as `tools_changed`, `system_prompt_changed`, `ttl_expired_5m`, or `likely_server_side`. The object is `null` until the session's first miss, and again whenever Claude Code couldn't identify a cause for the most recent miss. Requires Claude Code v2.1.260 or later.
400
401Two causes add counts to the object:
402
403* `tools_added` and `tools_removed`: with `tools_changed`, how many tools were added to or removed from the request
404* `system_char_delta`: with `system_prompt_changed`, the change in the system prompt's length, in characters
384405
385406## Examples
386407