API referenceSupport & configuration

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When making API requests, you must send an anthropic-version request header. For example, anthropic-version: 2023-06-01. If you are using the client SDKs, this is handled for you automatically.

For any given version with the Messages API, Anthropic preserves:

• Existing input parameters
• Existing output parameters

However, Anthropic 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, Anthropic will not break your usage.

Version history

Anthropic recommends 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 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, rather than data-only events.
    • Removed unnecessary data: [DONE] event.
  • Removed legacy exception and truncated values in responses.
• 2023-01-01: Initial release.