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.