> ## Documentation Index > Fetch the complete documentation index at: https://docs.dify.ai/llms.txt > Use this file to discover all available pages before exploring further. # Send Chat Message > Send a request to the chat application. ## OpenAPI ````yaml /en/api-reference/openapi_chat.json post /chat-messages openapi: 3.0.1 info: title: Chat App API description: >- Chat applications support session persistence, allowing previous chat history to be used as context for responses. This can be applicable for chatbot, customer service AI, etc. version: 1.0.0 servers: - url: '{api_base_url}' description: >- The base URL for the Chat App API. Replace {api_base_url} with the actual API base URL provided for your application. variables: api_base_url: default: https://api.dify.ai/v1 description: Actual base URL of the API security: - ApiKeyAuth: [] tags: - name: Chats description: Operations related to chat messages and interactions. - name: Files description: File upload and preview operations. - name: End Users description: Operations related to end user information. - name: Feedback description: User feedback operations. - name: Conversations description: Operations related to managing conversations. - name: TTS description: Text-to-Speech and Speech-to-Text operations. - name: Applications description: Operations to retrieve application settings and information. - name: Annotations description: Operations related to managing annotations for direct replies. paths: /chat-messages: post: tags: - Chats summary: Send Chat Message description: Send a request to the chat application. operationId: sendChatMessage requestBody: description: Request body to send a chat message. required: true content: application/json: schema: $ref: '#/components/schemas/ChatRequest' examples: streaming_example: summary: Request Example - Streaming mode value: inputs: city: San Francisco query: What are the specs of the iPhone 13 Pro Max? response_mode: streaming conversation_id: '' user: abc-123 files: - type: image transfer_method: remote_url url: https://cloud.dify.ai/logo/logo-site.png blocking_example: summary: Request Example - Blocking mode value: inputs: {} query: What are the specs of the iPhone 13 Pro Max? response_mode: blocking conversation_id: 45701982-8118-4bc5-8e9b-64562b4555f2 user: abc-123 responses: '200': description: >- Successful response. The content type and structure depend on the `response_mode` parameter in the request. - If `response_mode` is `blocking`, returns `application/json` with a `ChatCompletionResponse` object. - If `response_mode` is `streaming`, returns `text/event-stream` with a stream of `ChunkChatEvent` objects. content: application/json: schema: $ref: '#/components/schemas/ChatCompletionResponse' examples: blockingResponse: summary: Response Example - Blocking mode value: event: message task_id: c3800678-a077-43df-a102-53f23ed20b88 id: b01a39de-3480-4f3e-9f1e-4841a80f8e5e message_id: 9da23599-e713-473b-982c-4328d4f5c78a conversation_id: 45701982-8118-4bc5-8e9b-64562b4555f2 mode: chat answer: iPhone 13 Pro Max specs are listed here:... metadata: usage: prompt_tokens: 1033 prompt_unit_price: '0.001' prompt_price_unit: '0.001' prompt_price: '0.0010330' completion_tokens: 128 completion_unit_price: '0.002' completion_price_unit: '0.001' completion_price: '0.0002560' total_tokens: 1161 total_price: '0.0012890' currency: USD latency: 0.7682376249867957 retriever_resources: - position: 1 dataset_id: 101b4c97-fc2e-463c-90b1-5261a4cdcafb dataset_name: iPhone document_id: 8dd1ad74-0b5f-4175-b735-7d98bbbb4e00 document_name: iPhone List segment_id: ed599c7f-2766-4294-9d1d-e5235a61270a score: 0.98457545 content: >- "Model","Release Date","Display Size","Resolution","Processor","RAM","Storage","Camera","Battery","Operating System" "iPhone 13 Pro Max","September 24, 2021","6.7 inch","1284 x 2778","Hexa-core (2x3.23 GHz Avalanche + 4x1.82 GHz Blizzard)","6 GB","128, 256, 512 GB, 1TB","12 MP","4352 mAh","iOS 15" created_at: 1705407629 text/event-stream: schema: type: string description: >- A stream of Server-Sent Events (SSE). Each event is a JSON object prefixed with `data: ` and terminated by two newlines. See `ChunkChatEvent` for possible event structures. **SSE Parsing Guide:** Each event is a line prefixed with `data: ` followed by a JSON object, terminated by `\n\n`. Strip the `data: ` prefix before parsing JSON. The `event` field inside the JSON determines the event type. The stream ends when a `message_end` event is received. Ignore `ping` events (sent every 10 seconds to keep the connection alive). If an `error` event is received mid-stream, the stream terminates — parse the error object for details. Note that the HTTP status code is always `200` even when an error event occurs within the stream. examples: streamingResponseBasic: summary: Response Example - Streaming (Basic) value: >- data: {"event": "message", "task_id":"mock_task_id", "message_id": "5ad4cb98-f0c7-4085-b384-88c403be6290", "conversation_id": "45701982-8118-4bc5-8e9b-64562b4555f2", "answer": " I", "created_at": 1679586595} data: {"event": "message_end", "task_id":"mock_task_id", "message_id": "5ad4cb98-f0c7-4085-b384-88c403be6290", "conversation_id": "45701982-8118-4bc5-8e9b-64562b4555f2", "metadata": {"usage": {"total_tokens": 10, "latency": 1.0}}} streamingResponseAgent: summary: Response Example - Streaming (Agent) value: >- data: {"event": "agent_thought", "id": "agent_thought_id_1", "task_id": "task123", "message_id": "msg123", "conversation_id": "conv123", "position": 1, "thought": "Thinking about calling a tool...", "tool": "dalle3", "tool_input": "{\"dalle3\": {\"prompt\": \"a cute cat\"}}", "created_at": 1705395332} data: {"event": "message_file", "id": "file_id_1", "type": "image", "belongs_to": "assistant", "url": "https://example.com/cat.png", "conversation_id": "conv123"} data: {"event": "agent_message", "task_id": "task123", "message_id": "msg123", "conversation_id": "conv123", "answer": "Here is the image: ", "created_at": 1705395333} data: {"event": "message_end", "task_id":"task123", "message_id": "msg123", "conversation_id": "conv123", "metadata": {"usage": {"total_tokens": 50, "latency": 2.5}}} '400': description: >- - `app_unavailable` : App unavailable or misconfigured. - `not_chat_app` : App mode does not match the API route. - `conversation_completed` : The conversation has ended. - `provider_not_initialize` : No valid model provider credentials found. - `provider_quota_exceeded` : Model provider quota exhausted. - `model_currently_not_support` : Current model unavailable. - `completion_request_error` : Text generation failed. content: application/json: examples: app_unavailable: summary: app_unavailable value: status: 400 code: app_unavailable message: App unavailable, please check your app configurations. not_chat_app: summary: not_chat_app value: status: 400 code: not_chat_app message: Please check if your app mode matches the right API route. conversation_completed: summary: conversation_completed value: status: 400 code: conversation_completed message: >- The conversation has ended. Please start a new conversation. provider_not_initialize: summary: provider_not_initialize value: status: 400 code: provider_not_initialize message: >- No valid model provider credentials found. Please go to Settings -> Model Provider to complete your provider credentials. provider_quota_exceeded: summary: provider_quota_exceeded value: status: 400 code: provider_quota_exceeded message: >- Your quota for Dify Hosted OpenAI has been exhausted. Please go to Settings -> Model Provider to complete your own provider credentials. model_currently_not_support: summary: model_currently_not_support value: status: 400 code: model_currently_not_support message: >- Dify Hosted OpenAI trial currently not support the GPT-4 model. completion_request_error: summary: completion_request_error value: status: 400 code: completion_request_error message: Completion request failed. '404': description: '`not_found` : Conversation does not exist.' content: application/json: examples: conversation_not_exists: summary: not_found value: status: 404 code: not_found message: Conversation Not Exists. '429': description: >- - `too_many_requests` : Too many concurrent requests for this app. - `rate_limit_error` : The upstream model provider rate limit was exceeded. content: application/json: examples: too_many_requests: summary: too_many_requests value: status: 429 code: too_many_requests message: Too many requests. Please try again later. rate_limit_error: summary: rate_limit_error value: status: 429 code: rate_limit_error message: Rate Limit Error '500': description: '`internal_server_error` : Internal server error.' content: application/json: examples: internal_server_error: summary: internal_server_error value: status: 500 code: internal_server_error message: Internal server error. components: schemas: ChatRequest: type: object required: - inputs - query - user properties: query: type: string description: User input/question content. inputs: type: object description: >- Allows the entry of various variable values defined by the App. Contains key/value pairs. Refer to the `user_input_form` field in the [Get App Parameters](/api-reference/applications/get-app-parameters) response to discover the variable names and types expected by your app. additionalProperties: true response_mode: type: string enum: - streaming - blocking description: >- Mode of response return. `streaming` (recommended) uses SSE. `blocking` returns after completion (may be interrupted for long processes; not supported in Agent Assistant mode). Cloudflare timeout is `100 s`. When omitted, defaults to blocking behavior. user: type: string description: >- User identifier, unique within the application. This identifier scopes data access — conversations, messages, and files are only visible when queried with the same `user` value. conversation_id: type: string description: >- Conversation ID to continue a conversation. Pass the previous message's `conversation_id`. To start a new conversation, omit this field or pass an empty string. The response will return a `conversation_id` — pass it in subsequent messages to continue that conversation. files: type: array description: >- File list for multimodal understanding, including images, documents, audio, and video. To attach a local file, first upload it via [Upload File](/api-reference/files/upload-file) and use the returned `id` as `upload_file_id` with `transfer_method: local_file`. items: type: object required: - type - transfer_method properties: type: type: string enum: - image - document - audio - video - custom description: File type. transfer_method: type: string enum: - remote_url - local_file description: >- Transfer method: `remote_url` for file URL, `local_file` for uploaded file. url: type: string format: url description: File URL (required when `transfer_method` is `remote_url`). upload_file_id: type: string description: >- Uploaded file ID obtained from the [Upload File](/api-reference/files/upload-file) API (required when `transfer_method` is `local_file`). auto_generate_name: type: boolean description: >- Auto-generate conversation title. If `false`, use the [Rename Conversation](/api-reference/conversations/rename-conversation) API with `auto_generate: true` for async title generation. default: true ChatCompletionResponse: type: object properties: event: type: string description: Event type, fixed as `message`. task_id: type: string format: uuid description: Task ID for request tracking and stop response API. id: type: string format: uuid description: Unique ID of this response event. message_id: type: string format: uuid description: >- Unique message ID. Use this as the `message_id` parameter when calling feedback or suggested questions endpoints. conversation_id: type: string format: uuid description: Conversation ID. mode: type: string description: App mode, fixed as `chat`. answer: type: string description: Complete response content. metadata: type: object description: Metadata including usage and retriever resources. properties: usage: $ref: '#/components/schemas/Usage' retriever_resources: type: array description: List of retriever resources used. items: $ref: '#/components/schemas/RetrieverResource' created_at: type: integer format: int64 description: Message creation timestamp (Unix epoch seconds). Usage: type: object description: Model usage information. properties: prompt_tokens: type: integer description: Number of tokens in the prompt. prompt_unit_price: type: string format: decimal description: Unit price per prompt token. prompt_price_unit: type: string format: decimal description: Price unit for prompt tokens. prompt_price: type: string format: decimal description: Total price for prompt tokens. completion_tokens: type: integer description: Number of tokens in the completion. completion_unit_price: type: string format: decimal description: Unit price per completion token. completion_price_unit: type: string format: decimal description: Price unit for completion tokens. completion_price: type: string format: decimal description: Total price for completion tokens. total_tokens: type: integer description: Total number of tokens used. total_price: type: string format: decimal description: Total price for all tokens. currency: type: string description: Currency for pricing. latency: type: number format: double description: Latency in seconds. RetrieverResource: type: object description: Citation and attribution information for a retriever resource. properties: id: type: string format: uuid description: Unique ID of the retriever resource. message_id: type: string format: uuid description: ID of the message this resource belongs to. position: type: integer description: Position of the resource in the list. dataset_id: type: string format: uuid description: ID of the knowledge base. dataset_name: type: string description: Name of the knowledge base. document_id: type: string format: uuid description: ID of the document. document_name: type: string description: Name of the document. data_source_type: type: string description: Type of the data source. segment_id: type: string format: uuid description: ID of the specific chunk within the document. score: type: number format: float description: Similarity score of the resource. hit_count: type: integer description: Number of times this chunk was hit. word_count: type: integer description: Word count of the chunk. segment_position: type: integer description: Position of the chunk within the document. index_node_hash: type: string description: Hash of the index node. content: type: string description: Content snippet from the resource. summary: type: string nullable: true description: Summary of the chunk content. created_at: type: integer format: int64 description: Creation timestamp (Unix epoch seconds). securitySchemes: ApiKeyAuth: type: http scheme: bearer bearerFormat: API_KEY description: >- API Key authentication. For all API requests, include your API Key in the `Authorization` HTTP Header, prefixed with `Bearer `. Example: `Authorization: Bearer {API_KEY}`. **Strongly recommend storing your API Key on the server-side, not shared or stored on the client-side, to avoid possible API-Key leakage that can lead to serious consequences.** ````