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api/versioning.md

Changed on 2026-02-11 10:56:44 EST

+5 lines added
-5 lines removed
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# Versions¶

When making API requests, you must send an `anthropic-version` request header. For example, `anthropic-version: 2023-06-01`. If you are using our [client SDKs](/docs/en/api/client-sdks), this is handled for you automatically.¶

---¶

For any given API version, we will preserve:¶

* Existing input parameters¶
* Existing output parameters¶

However, we may do the following:¶

* Add additional optional inputs¶
* Add additional values to the output¶
* Change conditions for specific error types¶
* Add new variants to enum-like output values (for example, streaming event types)¶

Generally, if you are using the API as documented in this reference, we will not break your usage.¶

## Version history¶

We always recommend using the latest API version whenever possible. Previous versions are considered deprecated and may be unavailable for new users.¶

* `2023-06-01`
* New format for [streaming](/docs/en/build-with-claude/streaming) server-sent events (SSE):
* Completions are incremental. For example, `" Hello"`, `" my"`, `" name"`, `" is"`, `" Claude." ` instead of `" Hello"`, `" Hello my"`, `" Hello my name"`, `" Hello my name is"`, `" Hello my name is Claude."`.
* All events are [named events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#named%5Fevents), rather than [data-only events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#data-only%5Fmessages).
* Removed unnecessary `data: [DONE]` event.
* Removed legacy `exception` and `truncated` values in responses.¶
* `2023-01-01`: Initial release.

Unified Diff

--- a/api/versioning.md
+++ b/api/versioning.md
@@ -22,10 +22,10 @@
 
 We always recommend using the latest API version whenever possible. Previous versions are considered deprecated and may be unavailable for new users.
 
-* `2023-06-01`  
-   * New format for [streaming](/docs/en/build-with-claude/streaming) server-sent events (SSE):  
-         * Completions are incremental. For example, `" Hello"`, `" my"`, `" name"`, `" is"`, `" Claude." ` instead of `" Hello"`, `" Hello my"`, `" Hello my name"`, `" Hello my name is"`, `" Hello my name is Claude."`.  
-         * All events are [named events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#named%5Fevents), rather than [data-only events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#data-only%5Fmessages).  
-         * Removed unnecessary `data: [DONE]` event.  
+* `2023-06-01`
+   * New format for [streaming](/docs/en/build-with-claude/streaming) server-sent events (SSE):
+         * Completions are incremental. For example, `" Hello"`, `" my"`, `" name"`, `" is"`, `" Claude." ` instead of `" Hello"`, `" Hello my"`, `" Hello my name"`, `" Hello my name is"`, `" Hello my name is Claude."`.
+         * All events are [named events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#named%5Fevents), rather than [data-only events](https://developer.mozilla.org/en-US/Web/API/Server-sent%5Fevents/Using%5Fserver-sent%5Fevents#data-only%5Fmessages).
+         * Removed unnecessary `data: [DONE]` event.
    * Removed legacy `exception` and `truncated` values in responses.
 * `2023-01-01`: Initial release.