Create a Message changedapi/messages/create
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Lines−0removed
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First seen
14 Aug 2026
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Recorded edits13to this page, all time
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from line 1197, old and new numbered
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from line 1197
11971197
11981198 - `string`
11991199
1200- `diagnostics: optional DiagnosticsParam or null`
1201
1202 Request-level diagnostics. Currently carries the previous response
1203 id for prompt-cache divergence reporting.
1204
1205 - `previous_message_id: optional string or null`
1206
1207 The `id` (`msg_...`) from this client's previous /v1/messages response. The server compares that request's prompt fingerprint against this one and returns `diagnostics.cache_miss_reason` when the prompt-cache prefix could not be reused. Pass `null` on the first turn to opt in without a prior message to compare.
1208
1209 maxLength: 256
1210
12001211- `inference_geo: optional string or null`
12011212
12021213 Specifies the geographic region for inference processing. If not specified, the workspace's `default_inference_geo` is used.
from line 3873
38623873
38633874 - `file_id: string`
38643875
3876 - `diagnostics: Diagnostics or null`
3877
3878 Request-level diagnostics: why the prompt cache could not fully reuse
3879 the prefix of the request named by `diagnostics.previous_message_id`.
3880
3881 - `cache_miss_reason: CacheMissReason or null`
3882
3883 Explains why the prompt cache could not fully reuse the prefix from the request identified by `diagnostics.previous_message_id`. `null` means diagnosis is still pending — the response was serialized before the background comparison completed.
3884
3885 - `CacheMissModelChanged object`
3886
3887 - `type: "model_changed"`
3888
3889 default: model_changed
3890
3891 - `cache_missed_input_tokens: number`
3892
3893 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3894
3895 - `CacheMissSystemChanged object`
3896
3897 - `type: "system_changed"`
3898
3899 default: system_changed
3900
3901 - `cache_missed_input_tokens: number`
3902
3903 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3904
3905 - `CacheMissToolsChanged object`
3906
3907 - `type: "tools_changed"`
3908
3909 default: tools_changed
3910
3911 - `cache_missed_input_tokens: number`
3912
3913 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3914
3915 - `CacheMissMessagesChanged object`
3916
3917 - `type: "messages_changed"`
3918
3919 default: messages_changed
3920
3921 - `cache_missed_input_tokens: number`
3922
3923 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3924
3925 - `CacheMissPreviousMessageNotFound object`
3926
3927 - `type: "previous_message_not_found"`
3928
3929 default: previous_message_not_found
3930
3931 - `CacheMissUnavailable object`
3932
3933 - `type: "unavailable"`
3934
3935 default: unavailable
3936
38653937 - `model: Model`
38663938
38673939 The model that will complete your prompt.
from line 4478
44064478 "type": "text"
44074479 }
44084480 ],
4481 "diagnostics": {
4482 "cache_miss_reason": {
4483 "cache_missed_input_tokens": 0,
4484 "type": "model_changed"
4485 }
4486 },
44094487 "model": "claude-opus-5",
44104488 "role": "assistant",
44114489 "stop_details": {
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