Sweep 22 Sep 2026 · 17:19Z Build v2.1.280 501 read Stable v2.1.267 Latest v2.1.280 Next v2.1.280 Feeds RSS JSON llms.txt Unofficial
One change · api

Count tokens in a Message changed

api/beta/messages/count_tokens

Nearest release: v2.1.258, published an hour after this site recorded the change. Shown because the two are within 24 hours of each other. Nothing here says the release caused the edit.

Recorded here
Lines+70added
Lines−22removed
From line 16 where the diff opens
First seen 14 Aug 2026 this site's first read of the page
Recorded edits10to this page, all time

The whole hunk

from line 16, old and new numbered
/
lines
from line 16
1616 
1717 - `string`
1818 
19 - `"message-batches-2024-09-24" or "prompt-caching-2024-07-31" or "computer-use-2024-10-22" or 38 more`
19 - `"message-batches-2024-09-24" or "prompt-caching-2024-07-31" or "computer-use-2024-10-22" or 41 more`
2020 
2121 - `"message-batches-2024-09-24"`
2222 
from line 100
100100 
101101 - `"ce-user-management-2026-07-13"`
102102 
103 - `"mid-conversation-output-config-2026-07-01"`
104 
105 - `"thinking-binding-controls-2026-08-01"`
106 
107 - `"mid-conversation-system-clear-at-2026-08-21"`
108 
103109- `"anthropic-user-profile-id": optional string`
104110 
105111 The user profile ID to attribute this request to. Use when acting on behalf of a party other than your organization. Requires the `user-profiles` beta header.
from line 1386
13801386 
13811387 See [models](https://docs.anthropic.com/en/docs/models-overview) for additional details and options.
13821388 
1383 - `"claude-sonnet-5" or "claude-fable-5" or "claude-mythos-5" or 12 more`
1389 - `"claude-fable-5-1" or "claude-mythos-5-1" or "claude-sonnet-5" or 14 more`
13841390 
13851391 The model that will complete your prompt.
13861392 
13871393 See [models](https://docs.anthropic.com/en/docs/models-overview) for additional details and options.
13881394 
1395 - `"claude-fable-5-1"`
1396 
1397 Frontier intelligence for ambitious tasks across coding, scientific discovery, and enterprise workflows
1398 
1399 - `"claude-mythos-5-1"`
1400 
1401 Our most capable model for cybersecurity and biology research, available through trusted access programs
1402 
13891403 - `"claude-sonnet-5"`
13901404 
13911405 High-performance model for coding and agents
from line 1480
14661480 
14671481 - `"system"`
14681482 
1483 - `clear_at: optional "next_user_message" or "never" or null`
1484 
1485 How long this system message's text stays in front of the model. `"never"` (the default) renders it on every request that includes it. `"next_user_message"` renders it only for the user turn it follows: once a later `role: "user"` message exists in `messages` the message stays in the array (send it unchanged) but is no longer shown to the model. Only permitted on `role: "system"` messages.
1486 
1487 - `"next_user_message"`
1488 
1489 - `"never"`
1490 
1491 - `output_config: optional BetaSystemMessageOutputConfig or null`
1492 
1493 Per-message output configuration on a role:"system" input message.
1494 
1495 Fields here apply per-turn; `format` remains top-level only. An
1496 empty `{}` is accepted on a message that carries content; a message
1497 with neither content nor output_config fields is rejected.
1498 
1499 - `effort: optional "low" or "medium" or "high" or 2 more or null`
1500 
1501 All possible effort levels.
1502 
1503 - `"low"`
1504 
1505 - `"medium"`
1506 
1507 - `"high"`
1508 
1509 - `"xhigh"`
1510 
1511 - `"max"`
1512 
14691513- `model: Model`
14701514 
14711515 The model that will complete your prompt.
from line 1748
17041748 
17051749 - `type: "enabled"`
17061750 
1751 - `block_binding: optional BetaThinkingBlockBinding or null`
1752 
1753 Controls for block binding: what happens when a thinking block this
1754 request sends back fails the conversation check. Every field is optional;
1755 an empty object means every default.
1756 
1757 - `prefix_mismatch_behavior: optional BetaThinkingPrefixMismatchBehavior or null`
1758 
1759 What happens when a thinking block in `messages` fails the conversation
1760 check: it was created in a different conversation, or the messages before
1761 it have changed since. `"error"` (the default) fails the request with a
1762 400 error. `"drop_block"` removes the failing blocks and the request
1763 proceeds; the model no longer sees the dropped reasoning.
1764 
1765 - `"error"`
1766 
1767 - `"drop_block"`
1768 
17071769 - `display: optional "summarized" or "omitted" or "updates" or null`
17081770 
17091771 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
from line 1784
17221784 
17231785 - `type: "adaptive"`
17241786 
1787 - `block_binding: optional BetaThinkingBlockBinding or null`
1788 
1789 Controls for block binding: what happens when a thinking block this
1790 request sends back fails the conversation check. Every field is optional;
1791 an empty object means every default.
1792 
17251793 - `display: optional "summarized" or "omitted" or "updates" or null`
17261794 
17271795 Controls how thinking content appears in the response. When set to `summarized`, thinking is returned normally. When set to `omitted`, thinking content is redacted but a signature is returned for multi-turn continuity. Defaults to `summarized`.
from line 2181
21132181 
21142182 - `type: "browser_toolset_20260801"`
21152183 
2116 - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"`
2117 
2118 - `"direct"`
2119 
2120 - `"code_execution_20250825"`
2121 
2122 - `"code_execution_20260120"`
2123 
2124 - `"code_execution_20260521"`
2125 
21262184 - `cache_control: optional BetaCacheControlEphemeral or null`
21272185 
21282186 Create a cache control breakpoint at this content block.
from line 2806
27482806 via `configs.zoom.enabled`.
27492807 
27502808 - `type: "computer_toolset_20260801"`
2751 
2752 - `allowed_callers: optional array of "direct" or "code_execution_20250825" or "code_execution_20260120" or "code_execution_20260521"`
2753 
2754 - `"direct"`
2755 
2756 - `"code_execution_20250825"`
2757 
2758 - `"code_execution_20260120"`
2759 
2760 - `"code_execution_20260521"`
27612809 
27622810 - `cache_control: optional BetaCacheControlEphemeral or null`
27632811