Send a message to a conversation.

Purpose

Send a message to a conversation within an agent (formerly known as project) identified by its unique projectId and sessionId.

This endpoint enables you to send a new message to a specific conversation, facilitating seamless communication and collaboration within the agent.

By providing the projectId and sessionId, you can target the desired conversation and contribute to the ongoing discussion.

This API endpoint supports real-time streaming, allowing for instant message delivery and dynamic updates which enables efficient and interactive communication between the user and agent.

Here is an example to send a message to a conversation: API SDK.

This is the lower-level message pipe into an existing conversation session. It pairs a conversation context (sessionId) with user prompts, optional files, and persona overrides to produce answers.

At a high level, this is the canonical way to work with conversations and messages between users and the agent via the CustomGPT API.

When to use

• When you need to send a message to a conversation as part of your backend or automation workflows.
• When your app behaves like a chat widget and needs to send user prompts, files and optional persona overrides into an existing session.

For session ID:

• session_id must be less than 255 characters
• session_id must not already be present in the system, for another agent (if it's present for that agent it'll of course just send a new message to it)