Messages changedapi/messages
Nearest release: v2.1.282, published an hour before this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.
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Lines+529added
Lines−0removed
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1,199
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First seen
14 Aug 2026
this site's first read of the page
Recorded edits13to this page, all time
### Cache Miss Messages Changed ### Cache Miss Model Changed ### Cache Miss Previous Message Not Found ### Cache Miss Reason ### Cache Miss System Changed ### Cache Miss Tools Changed ### Cache Miss Unavailable ### Diagnostics ### Diagnostics Param
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from line 1199
11991199
12001200 - `string`
12011201
1202- `diagnostics: optional DiagnosticsParam or null`
1203
1204 Request-level diagnostics. Currently carries the previous response
1205 id for prompt-cache divergence reporting.
1206
1207 - `previous_message_id: optional string or null`
1208
1209 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.
1210
1211 maxLength: 256
1212
12021213- `inference_geo: optional string or null`
12031214
12041215 Specifies the geographic region for inference processing. If not specified, the workspace's `default_inference_geo` is used.
from line 3875
38643875
38653876 - `file_id: string`
38663877
3878 - `diagnostics: Diagnostics or null`
3879
3880 Request-level diagnostics: why the prompt cache could not fully reuse
3881 the prefix of the request named by `diagnostics.previous_message_id`.
3882
3883 - `cache_miss_reason: CacheMissReason or null`
3884
3885 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.
3886
3887 - `CacheMissModelChanged object`
3888
3889 - `type: "model_changed"`
3890
3891 default: model_changed
3892
3893 - `cache_missed_input_tokens: number`
3894
3895 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3896
3897 - `CacheMissSystemChanged object`
3898
3899 - `type: "system_changed"`
3900
3901 default: system_changed
3902
3903 - `cache_missed_input_tokens: number`
3904
3905 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3906
3907 - `CacheMissToolsChanged object`
3908
3909 - `type: "tools_changed"`
3910
3911 default: tools_changed
3912
3913 - `cache_missed_input_tokens: number`
3914
3915 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3916
3917 - `CacheMissMessagesChanged object`
3918
3919 - `type: "messages_changed"`
3920
3921 default: messages_changed
3922
3923 - `cache_missed_input_tokens: number`
3924
3925 Approximate number of input tokens that would have been read from cache had the prefix matched the previous request.
3926
3927 - `CacheMissPreviousMessageNotFound object`
3928
3929 - `type: "previous_message_not_found"`
3930
3931 default: previous_message_not_found
3932
3933 - `CacheMissUnavailable object`
3934
3935 - `type: "unavailable"`
3936
3937 default: unavailable
3938
38673939 - `model: Model`
38683940
38693941 The model that will complete your prompt.
from line 4480
44084480 "type": "text"
44094481 }
44104482 ],
4483 "diagnostics": {
4484 "cache_miss_reason": {
4485 "cache_missed_input_tokens": 0,
4486 "type": "model_changed"
4487 }
4488 },
44114489 "model": "claude-opus-5",
44124490 "role": "assistant",
44134491 "stop_details": {
from line 8406
83288406
83298407 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
83308408
8331 - `url: string`
8332
8333 The final post-redirect URL the download was served from.
8334
8335 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8336
8337 - `error: optional string or null`
8338
8339 The failure or cancellation detail, when known.
8340
8341 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
8342
8343### Browser State Change Download Completed
8344
8345- `BrowserStateChangeDownloadCompleted object`
8346
8347 A file download that finished during this call, reported with the
8348 same `download_id` as its `download_started` — or without a prior
8349 `download_started`, when the download finished during the call that
8350 started it (at most one state change per `download_id` per result).
8351
8352 - `type: "download_completed"`
8353
8354 - `download_id: string`
8355
8356 The caller-assigned identifier for this download, stable across the state changes reporting it.
8357
8358 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8359
8360 - `url: string`
8361
8362 The final post-redirect URL the download was served from.
8363
8364 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8365
8366 - `path: optional string or null`
8367
8368 Where the executor saved the file, on the executor's filesystem. Only included when another tool in the same environment can read the file at that path.
8369
8370 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
8371
8372 - `size_bytes: optional number or null`
8373
8374 The completed download's size.
8375
8376 minimum: 0
8377
8378### Browser State Change Download Failed
8379
8380- `BrowserStateChangeDownloadFailed object`
8381
8382 A file download that failed — or was cancelled — during this call.
8383
8384 - `type: "download_failed"`
8385
8386 - `download_id: string`
8387
8388 The caller-assigned identifier for this download, stable across the state changes reporting it.
8389
8390 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8391
8392 - `url: string`
8393
8394 The final post-redirect URL the download was served from.
8395
8396 maxLength: 4096, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8397
8398 - `error: optional string or null`
8399
8400 The failure or cancellation detail, when known.
8401
8402 pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$, maxLength: 4096
8403
8404### Browser State Change Download Started
8405
8406- `BrowserStateChangeDownloadStarted object`
8407
8408 A file download that started during this call.
8409
8410 - `type: "download_started"`
8411
8412 - `download_id: string`
8413
8414 The caller-assigned identifier for this download, stable across the state changes reporting it.
8415
8416 maxLength: 4096, minLength: 1, pattern: ^[^\x00-\x1f\x7f-\x9f\u2028\u2029]*$
8417
8418 - `url: string`
8419
8420 The final post
8409
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