Respond to chat message (streaming)

Streams a single assistant turn as normalized SSE events with stable turn, message, and part IDs. Emits events: turn.started, turn.status, message.created, message.part.updated, message.completed, session.usage, turn.completed.

When to use this endpoint: Recommended for building custom chat UIs that need real-time streaming progress. This is the primary streaming endpoint for new integrations.

Alternatives:

POST /chat/:id/message — synchronous, returns complete response as JSON (best for server-to-server)

POST

agent

chat

{id}

respond

curl -X POST "https://api.case.dev/agent/v1/chat/%3Cstring%3E/respond" \
  -H "Authorization: Bearer $CASEDEV_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "parts": [
    {
      "type": "text",
      "text": "<string>"
    }
  ]
}'

"<string>"

Authorizations

Authorization

string

header

required

API key starting with sk_case_

Path Parameters

string

required

Chat session ID

Body

application/json

Message payload following the AI SDK UIMessage format. The body is passed through 1:1 to the underlying chat runtime session. Currently only text parts are supported.

parts

object[]

Message content parts. Currently only "text" type is supported. Additional types (e.g. file, image) may be added in future versions.

Show child attributes

Response

Turn-scoped normalized SSE stream

The response is of type string.

Stream chat eventsRelays runtime SSE events for this chat. Supports replay from buffered events using Last-Event-ID.

⌘I

curl -X POST "https://api.case.dev/agent/v1/chat/%3Cstring%3E/respond" \
  -H "Authorization: Bearer $CASEDEV_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
  "parts": [
    {
      "type": "text",
      "text": "<string>"
    }
  ]
}'

"<string>"