AsyncAPI channel · Anthropic
· Anthropic Messages Streaming API
/messages
Server-Sent Events stream returned by `POST https://api.anthropic.com/v1/messages`
when the request body includes `"stream": true`. Each SSE frame's event name
maps to one of the messages defined below; the JSON payload after `data:`
carries the matching schema.
Receive Anthropic Messages streaming events over HTTP+SSE
Messages
message_start
Opens a streamed response with a Message object whose content array is empty.
Content-Type: application/json
content_block_start
Marks the start of a content block at a given index in the final Message.content array.
Content-Type: application/json
content_block_delta
Carries a partial update for the content block at the specified index.
Content-Type: application/json
content_block_stop
Marks the end of the content block at the given index.
Content-Type: application/json
message_delta
Top-level updates to the final Message (stop reason, sequence) plus cumulative usage.
Content-Type: application/json
message_stop
Final event on the stream; the connection is closed afterward.
Content-Type: application/json
ping
Keep-alive event; may appear any number of times during the stream.
Content-Type: application/json
error
Error event emitted in the stream (e.g. overloaded_error during high load).
Content-Type: application/json
About AsyncAPI
The AsyncAPI specification describes event-driven APIs the way OpenAPI describes request/response APIs. A channel is the named pipe — a webhook URL, a Kafka topic, a WebSocket route, an MQTT subject — that producers and consumers publish or subscribe to. Each channel carries one or more messages with structured payloads, and an operation declares whether a given party sends or receives on that channel.
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