> ## Documentation Index > Fetch the complete documentation index at: https://docs.openhands.dev/llms.txt > Use this file to discover all available pages before exploring further. # Send Message To Conversation > Send a follow-up message to an existing conversation. This REST endpoint provides a simplified way to send messages to a running conversation without requiring a WebSocket connection. **Alternative Approaches:** This endpoint is a convenience wrapper. You can also interact with the agent server directly using: 1. **WebSocket**: Connect to the agent server's WebSocket endpoint for real-time bidirectional communication 2. **Agent Server REST API**: Call the agent server's REST endpoints directly using the `conversation_url` from `GET /api/v1/app-conversations/{id}` **Design Note:** This endpoint is intentionally a thin proxy that forwards messages to the agent server without additional processing logic. Any custom processing (validation, transformation, side effects) should be implemented via webhook callbacks, not in this endpoint. This ensures that direct agent server invocation and this convenience endpoint remain functionally equivalent. **Prerequisites:** - The sandbox must be in RUNNING state - If the sandbox is PAUSED, call `POST /api/v1/sandboxes/{sandbox_id}/resume` first - If the sandbox is STARTING, wait for it to reach RUNNING state **Error responses:** - 404: Conversation or sandbox not found - 409: Sandbox exists but is not running (PAUSED, STARTING, STOPPING) - 410: Conversation is archived (sandbox no longer exists) - 503: Sandbox is in ERROR state or agent server is unavailable Args: conversation_id: The UUID of the conversation to send the message to request: The message content and options Returns: AppSendMessageResponse with success status and sandbox state ## OpenAPI ````yaml /openapi/openhands-cloud.json post /api/v1/app-conversations/{conversation_id}/send-message openapi: 3.1.0 info: title: OpenHands description: 'OpenHands: Code Less, Make More' version: 0.0.1 servers: [] security: [] paths: /api/v1/app-conversations/{conversation_id}/send-message: post: tags: - Conversations summary: Send Message To Conversation description: >- Send a follow-up message to an existing conversation. This REST endpoint provides a simplified way to send messages to a running conversation without requiring a WebSocket connection. **Alternative Approaches:** This endpoint is a convenience wrapper. You can also interact with the agent server directly using: 1. **WebSocket**: Connect to the agent server's WebSocket endpoint for real-time bidirectional communication 2. **Agent Server REST API**: Call the agent server's REST endpoints directly using the `conversation_url` from `GET /api/v1/app-conversations/{id}` **Design Note:** This endpoint is intentionally a thin proxy that forwards messages to the agent server without additional processing logic. Any custom processing (validation, transformation, side effects) should be implemented via webhook callbacks, not in this endpoint. This ensures that direct agent server invocation and this convenience endpoint remain functionally equivalent. **Prerequisites:** - The sandbox must be in RUNNING state - If the sandbox is PAUSED, call `POST /api/v1/sandboxes/{sandbox_id}/resume` first - If the sandbox is STARTING, wait for it to reach RUNNING state **Error responses:** - 404: Conversation or sandbox not found - 409: Sandbox exists but is not running (PAUSED, STARTING, STOPPING) - 410: Conversation is archived (sandbox no longer exists) - 503: Sandbox is in ERROR state or agent server is unavailable Args: conversation_id: The UUID of the conversation to send the message to request: The message content and options Returns: AppSendMessageResponse with success status and sandbox state operationId: >- send_message_to_conversation_api_v1_app_conversations__conversation_id__send_message_post parameters: - name: conversation_id in: path required: true schema: type: string format: uuid title: Conversation Id requestBody: required: true content: application/json: schema: $ref: '#/components/schemas/AppSendMessageRequest' responses: '200': description: Successful Response content: application/json: schema: $ref: '#/components/schemas/AppSendMessageResponse' '404': description: Conversation or sandbox not found '409': description: >- Sandbox is not running. Resume it first via POST /sandboxes/{id}/resume '410': description: Conversation is archived (sandbox no longer exists) '422': description: Validation Error content: application/json: schema: $ref: '#/components/schemas/HTTPValidationError' '503': description: Sandbox is in error state or agent server unavailable security: - APIKeyHeader: [] components: schemas: AppSendMessageRequest: properties: role: type: string const: user title: Role description: The role of the message sender. Currently only "user" is supported. default: user content: items: anyOf: - $ref: '#/components/schemas/TextContent' - $ref: '#/components/schemas/ImageContent' type: array minItems: 1 title: Content description: The message content as a list of text and/or image content blocks. run: type: boolean title: Run description: Whether to automatically run the agent after sending the message. default: true type: object required: - content title: AppSendMessageRequest description: |- Request to send a follow-up message to a conversation. This is used to send messages to an existing conversation via REST API, as an alternative to WebSocket communication. AppSendMessageResponse: properties: success: type: boolean title: Success description: Whether the message was successfully sent to the agent. sandbox_status: $ref: '#/components/schemas/SandboxStatus' description: The current status of the sandbox after the operation. message: anyOf: - type: string - type: 'null' title: Message description: >- Optional message with additional details (e.g., if sandbox was resumed). type: object required: - success - sandbox_status title: AppSendMessageResponse description: Response from sending a message to a conversation. HTTPValidationError: properties: detail: items: $ref: '#/components/schemas/ValidationError' type: array title: Detail type: object title: HTTPValidationError TextContent: properties: cache_prompt: type: boolean title: Cache Prompt default: false type: type: string const: text title: Type default: text text: type: string title: Text additionalProperties: false type: object required: - text title: TextContent ImageContent: properties: cache_prompt: type: boolean title: Cache Prompt default: false type: type: string const: image title: Type default: image image_urls: items: type: string type: array title: Image Urls type: object required: - image_urls title: ImageContent SandboxStatus: type: string enum: - STARTING - RUNNING - PAUSED - ERROR - MISSING title: SandboxStatus ValidationError: properties: loc: items: anyOf: - type: string - type: integer type: array title: Location msg: type: string title: Message type: type: string title: Error Type input: title: Input ctx: type: object title: Context type: object required: - loc - msg - type title: ValidationError securitySchemes: APIKeyHeader: type: apiKey in: header name: X-Access-Token ````