cache-diagnostics changedbuild-with-claude/cache-diagnostics
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702702<Tabs>
703703 <Tab title="cURL">
704704 <Info>
705 This workflow doesn't translate well to a one-off shell command. See the SDK tabs for the loop pattern; the per-turn HTTP request is identical to [Basic usage](https://platform.claude.com/docs/en/build-with-claude/cache-diagnostics#basic-usage).
705 This workflow doesn't translate well to a one-off shell command. Use the Claude SDK to run the loop; the per-turn HTTP request is identical to [Basic usage](https://platform.claude.com/docs/en/build-with-claude/cache-diagnostics#basic-usage).
706706 </Info>
707707 </Tab>
708708
709709 <Tab title="CLI">
710710 <Info>
711 This workflow doesn't translate well to a one-off shell command. See the SDK tabs for the loop pattern; the per-turn CLI invocation is identical to [Basic usage](https://platform.claude.com/docs/en/build-with-claude/cache-diagnostics#basic-usage).
711 This workflow doesn't translate well to a one-off shell command. Use the Claude SDK to run the loop; the per-turn CLI command is identical to [Basic usage](https://platform.claude.com/docs/en/build-with-claude/cache-diagnostics#basic-usage).
712712 </Info>
713713 </Tab>
714714
from line 968
968968| Value | Meaning |
969969| ------------------------------ | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
970970| `null` | The request did not include the `diagnostics` object, `previous_message_id` was `null` (first turn, nothing to compare), or a comparison ran and found no divergence. |
971| `{"cache_miss_reason": null}` | The comparison was still running when the response was serialized. This can happen when the response starts very quickly. Treat it as inconclusive and check the next turn. |
971| `{"cache_miss_reason": null}` | The comparison was still running when the response was serialized. This can occur when the response starts very quickly. Treat it as inconclusive and check the next turn. |
972972| `{"cache_miss_reason": {...}}` | A `cache_miss_reason` is attached. For `*_changed` types this identifies the first divergence point; `previous_message_not_found` and `unavailable` are cases where no comparison was produced. |
973973
974974When `cache_miss_reason` is non-null, it looks like this:
from line 996
996996
997997## Cache miss reason types
998998
999`cache_miss_reason` is a discriminated union on `type`. The response reports the earliest divergence only, so fix it first; later ones may be hidden behind it.
999`cache_miss_reason` is a discriminated union on `type`. The response reports the earliest divergence only, so fix it first; later ones might be hidden behind it.
10001000
10011001| Type | What it means | What to change |
10021002| ---------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
from line 1013
10131013
10141014## Reading diagnostics alongside usage
10151015
1016`diagnostics` answers "did my request change?" while `usage.cache_read_input_tokens` answers "did the cache hit?". Combining them tells you where to look.
1016`diagnostics` answers "did my request change?" whereas `usage.cache_read_input_tokens` answers "did the cache hit?" Combining them tells you where to look.
10171017
10181018This matrix applies to turns where you passed a real `previous_message_id`. On the first turn (`previous_message_id: null`), `diagnostics` is always `null` and `cache_read_input_tokens` is normally zero because the cache is being written, not read; no troubleshooting is needed. The matrix also does not apply when `cache_miss_reason` is `null` (the comparison is still pending; check the next turn) or when its `type` is `previous_message_not_found` or `unavailable` (no comparison was produced).
10191019
from line 1021
10211021| ----------------------------------------- | ----------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ |
10221022| `null` | high | Working as expected. Your prefix is stable and the cache hit. |
10231023| `null` | low or zero | Your requests match but the cache entry was no longer available. Consider shortening gaps between turns or using the [1-hour cache TTL](https://platform.claude.com/docs/en/build-with-claude/prompt-caching#1-hour-cache-duration). |
1024| `cache_miss_reason` is a `*_changed` type | low or zero | Your bug. The request changed; fix the cause indicated by `type`. |
1024| `cache_miss_reason` is a `*_changed` type | low or zero | The request changed; fix the cause indicated by `type`. |
10251025| `cache_miss_reason` is a `*_changed` type | high | Rare. A change occurred late in the prompt but an earlier `cache_control` breakpoint still hit. Worth fixing, but low impact. |
10261026
10271027## Limitations
from line 1029
10291029* **Claude API only:** Not available on Amazon Bedrock or Google Cloud.
10301030* **Limited retention:** Fingerprints for `previous_message_id` lookup expire after a short period. Run diagnostic comparisons between closely spaced requests.
10311031* **Same workspace:** The previous request must have run in the same organization and workspace. To check, compare the `anthropic-workspace-id` [response header](https://platform.claude.com/docs/en/api/overview#response-headers) on the two responses.
1032* **Comparison horizon:** For very long conversations where the only change is deep in the message list, the response may be `unavailable` rather than a precise location.
1032* **Comparison horizon:** For very long conversations where the only change is deep in the message list, the response might be `unavailable` rather than a precise location.
10331033* **Best-effort:** Diagnostics never blocks or fails your request. If diagnostic information is not available, the response returns `unavailable`, or `cache_miss_reason: null` when the comparison was still running.
10341034
10351035## Data retention
No line in this hunk matches that.