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.

Open source AsyncAPI → All Anthropic channels Anthropic provider profile

Provider: Anthropic AsyncAPI: v2.6.0 Spec: Anthropic Messages Streaming API Operations: 1 Messages: 8

Channel address

/messages

Operations

subscribeMessagesStream

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.

Browse every event-driven channel on the APIs.io network or compare with the broader Naftiko capability, Agent Skill, and MCP server surfaces of the same providers.