WebSocket Protocol

Overview

VIZOCHOK uses a WebSocket-based protocol for real-time streaming chat. The protocol is designed around three principles:

Auth via first message — credentials are sent as the first WebSocket message, not as query parameters (which would appear in server logs).
Structured messages — all messages are JSON objects with a type field for routing.
Streaming text — LLM responses are delivered token-by-token via text_delta messages for real-time display.

Connection Lifecycle

WebSocket Connect

Client establishes WebSocket connection. Server accepts.

Authentication

Client sends {"type":"auth","token":"pk_..."} (must be first message). Server responds with {"type":"auth_ok"}.

Session Initialization

New conversation: Server sends {"type":"conversation_started", "conversation_id":"..."}Reconnection: Server sends {"type":"session_restored", "conversation_id":"...", "selected_items":[...]} with cart state and pending tools.

Message Exchange

Client sends {"type":"message","text":"..."}. Server responds with status updates, text_delta chunks (repeated), text_end, and response_complete.

Disconnect

Client closes connection or disconnects. Session is saved to Redis for reconnection.

Endpoint

wss://api.vizochok.com/api/v1/ws/chat

For self-hosted deployments, replace the host with your API base URL. The SDK automatically converts https:// to wss://.

Client to Server Messages

auth

Must be the first message sent after connection. The server waits up to 10 seconds for this message before closing the connection with code 4001.

Field	Type	Required	Description
`type`	`string`	Yes	Must be `"auth"`.
`token`	`string`	Yes	API key (public `pk_` or secret `sk_`).
`store_id`	`string`	No	Store identifier. Used for webhook routing.
`user_id`	`string`	No	User identifier. Enables per-user rate limits and personalization.

{
  "type": "auth",
  "token": "pk_live_abc123",
  "store_id": "my-store",
  "user_id": "user_42"
}

message

Send a text message from the user.

Field	Type	Required	Description
`type`	`string`	Yes	Must be `"message"`.
`text`	`string`	Yes	The user’s message text. Max 64 KB.
`store_id`	`string`	No	Store identifier.
`user_id`	`string`	No	User identifier.
`conversation_id`	`string`	No	Conversation ID from `conversation_started` or `session_restored`. Omit to start a new conversation.
`language`	`string`	No	Language code: `"uk"`, `"en"`, or `"ru"`. Default: `"uk"`.

{
  "type": "message",
  "text": "Find me some milk",
  "store_id": "my-store",
  "user_id": "user_42",
  "conversation_id": "conv_abc123"
}

action

Send a user action in response to an interactive tool (product selection, quick reply, checklist, meal plan).

Field	Type	Required	Description
`type`	`string`	Yes	Must be `"action"`.
`action`	`string`	Yes	Action type: `"select"`, `"checklist_confirm"`, `"meal_plan_approve"`, `"meal_plan_modify"`.
`store_id`	`string`	No	Store identifier.
`user_id`	`string`	No	User identifier.
`conversation_id`	`string`	No	Current conversation ID.
`sku`	`string`	No	Product SKU (for `"select"` action).
`quantity`	`number`	No	Product quantity (for `"select"` action).
`recipe_name`	`string`	No	Recipe name (for `"checklist_confirm"` action).
`selected`	`string[]`	No	Deselected ingredient names (for `"checklist_confirm"` action).
`text`	`string`	No	Modification text (for `"meal_plan_modify"` action).

{
  "type": "action",
  "action": "select",
  "sku": "milk-001",
  "quantity": 2,
  "store_id": "my-store",
  "conversation_id": "conv_abc123"
}

ping

Client-initiated keepalive message. The SDK sends this every 30 seconds.

{ "type": "ping" }

pong

Response to a server-initiated ping. Must be sent within 60 seconds to avoid heartbeat timeout.

{ "type": "pong" }

Server to Client Messages

auth_ok

Confirms successful authentication. Sent immediately after a valid auth message.

{ "type": "auth_ok" }

conversation_started

Sent when a new conversation is created (first message with no conversation_id).

Field	Type	Description
`type`	`string`	`"conversation_started"`
`conversation_id`	`string`	The new conversation’s unique ID.

{
  "type": "conversation_started",
  "conversation_id": "conv_abc123"
}

session_restored

Sent on reconnect when the client provides an existing conversation_id that has an active Redis session. Contains the current cart state and any pending interactive tool.

Field	Type	Description
`type`	`string`	`"session_restored"`
`conversation_id`	`string`	The restored conversation ID.
`selected_items`	`CartItem[]`	Current cart items (optional, present if cart is non-empty).
`cart_total`	`number`	Total cart value (optional).
`pending_tool`	`object`	Pending interactive tool awaiting user input (optional).

The pending_tool object varies by tool type:

Tool Name	Fields
`show_products_to_user`	`name`, `id`, `products: ProductItem[]`
`ask_user`	`name`, `id`, `options: string[]`
`show_recipe_checklist`	`name`, `id`, `recipe_name: string`, `ingredients: string[]`
`show_meal_plan`	`name`, `id`, `title`, `days`, `total_ingredients`

{
  "type": "session_restored",
  "conversation_id": "conv_abc123",
  "selected_items": [
    { "sku": "milk-001", "name": "Milk 2.5%", "price": 42.90, "quantity": 1 }
  ],
  "cart_total": 42.90
}

text_delta

A single token (or small chunk) of streaming text from the LLM. Multiple text_delta messages form a complete text block, terminated by text_end.

Field	Type	Description
`type`	`string`	`"text_delta"`
`delta`	`string`	Text fragment to append.

{ "type": "text_delta", "delta": "Here " }
{ "type": "text_delta", "delta": "are some " }
{ "type": "text_delta", "delta": "options:" }

text_end

Signals the end of a streaming text block. After this, the streaming cursor should stop.

{ "type": "text_end" }

text

A complete text block (non-streaming). Used for short, pre-formed responses.

Field	Type	Description
`type`	`string`	`"text"`
`text`	`string`	Complete text content.

{ "type": "text", "text": "Added to cart!" }

status

Progress indicator during tool execution. Replaced in the UI when a new status arrives for the same message.

Field	Type	Description
`type`	`string`	`"status"`
`code`	`string`	Status code (mapped to localized text by the SDK).
`text`	`string`	Fallback text if the SDK does not recognize the code.
`query`	`string`	Search query (for `"searching"` status).
`product`	`string`	Product name (for `"adding_to_cart"` status).

Status codes:

Code	English	Ukrainian
`searching`	Searching products …	Шукаю …
`thinking`	Thinking…	Думаю…
`adding_to_cart`	Adding to cart…	Додаю …
`removing_from_cart`	Removing from cart…	Видаляю з кошика…
`updating_cart`	Updating cart…	Оновлюю кількість…
`suggesting`	Selecting the best options…	Підбираю найкращі варіанти…
`generating_plan`	Creating a meal plan…	Створюю план харчування…
`checking_list`	Checking the list…	Перевіряю список…
`updating_profile`	Updating preferences…	Оновлюю налаштування…
`loading_cart`	Loading cart…	Завантажую кошик…
`clearing_cart`	Clearing cart…	Очищую кошик…
`loading_details`	Loading details…	Завантажую деталі…
`preparing_results`	Preparing results…	Готую результати…
`completing_session`	Completing session…	Завершую сесію…
`processing`	Processing…	Обробляю…

product_cards

Display a set of products for the user to select from.

Field	Type	Description
`type`	`string`	`"product_cards"`
`text`	`string`	Introductory text (e.g., “Here are some options:”).
`items`	`ProductItem[]`	Array of products to display.
`query`	`string`	The search query that produced these results (optional).

quick_replies

Display quick reply buttons for the user to choose from.

Field	Type	Description
`type`	`string`	`"quick_replies"`
`options`	`string[]`	Array of reply option texts.

{
  "type": "quick_replies",
  "options": ["Yes, add all", "Show cheaper options", "No thanks"]
}

confirmation

Confirms a cart operation (add, remove, update).

Field	Type	Description
`type`	`string`	`"confirmation"`
`text`	`string`	Confirmation message.
`product`	`ProductItem`	The product that was added/removed/updated.

ingredient_checklist

Display a recipe ingredient checklist for user selection.

Field	Type	Description
`type`	`string`	`"ingredient_checklist"`
`recipe_name`	`string`	Name of the recipe.
`text`	`string`	Description text.
`ingredients`	`IngredientItem[]`	Array of ingredients with selection state.

Each IngredientItem:

Field	Type	Description
`id`	`string`	Unique ingredient identifier.
`name`	`string`	Ingredient display name.
`selected`	`boolean`	Whether the ingredient is pre-selected.

meal_plan

Display a generated meal plan for the user to approve or modify.

Field	Type	Description
`type`	`string`	`"meal_plan"`
`title`	`string`	Plan title.
`days`	`MealPlanDay[]`	Array of days with meals.
`total_ingredients`	`string[]`	Combined ingredient list across all days.
`message`	`string`	Summary message.

session_summary

Display a summary of the current session’s cart.

Field	Type	Description
`type`	`string`	`"session_summary"`
`items`	`CartItem[]`	All items in the session cart.
`total`	`number`	Total cart value.

cart_changed

Notification that the cart was modified. This is a UI-only event — the actual cart state lives on the client’s backend.

Field	Type	Description
`type`	`string`	`"cart_changed"`
`action`	`string`	`"item_selected"`, `"item_removed"`, `"quantity_updated"`, or `"cart_cleared"`.
`sku`	`string`	SKU of the affected product.
`name`	`string`	Name of the affected product.
`quantity`	`number`	New quantity.
`price`	`number`	Product price.
`items`	`CartItem[]`	Complete cart after the change.
`total`	`number`	New cart total.

response_complete

Signals the end of an agent response. The conversation is ready for the next user message.

Field	Type	Description
`type`	`string`	`"response_complete"`
`conversation_id`	`string`	Current conversation ID.
`session_summary`	`object`	Optional. Contains `selected_items`, `total`, `item_count`.

{
  "type": "response_complete",
  "conversation_id": "conv_abc123",
  "session_summary": {
    "selected_items": [
      { "sku": "milk-001", "name": "Milk 2.5%", "price": 42.90, "quantity": 1 }
    ],
    "total": 42.90,
    "item_count": 1
  }
}

error

An error occurred while processing the message.

Field	Type	Description
`type`	`string`	`"error"`
`code`	`string`	Machine-readable error code. See Error Codes.
`text`	`string`	Fallback error text (optional).
`retry_after`	`number`	Seconds to wait before retrying (for `rate_limit_exceeded`).
`max_size`	`number`	Maximum allowed message size in bytes (for `message_too_large`).
`limit`	`number`	The limit that was exceeded (for user limit errors).

event

Internal server events. Currently ignored by the SDK but can be used for analytics.

Field	Type	Description
`type`	`string`	`"event"`
`event`	`string`	Event name.
`data`	`object`	Event-specific data.

ping / pong

Server-initiated heartbeat. The client must respond with {"type": "pong"} within 60 seconds.

{ "type": "ping" }

Server response to a client-initiated ping:

{ "type": "pong" }

Close Codes

Code	Reason	Description
`4001`	Auth timeout / Invalid auth	First message was not `auth`, timed out (10s), invalid format, or invalid/expired API key.
`4002`	Missing chat scope	API key does not have the `chat` scope.
`4003`	Origin not allowed / Deactivated	WebSocket origin not in allowed list, or tenant is deactivated.
`4004`	LLM not configured	Tenant has no LLM provider configured.
`4008`	Heartbeat timeout	No pong received within 60 seconds of a ping.
`4029`	Too many connections	API key has more than 3 concurrent WebSocket connections.

Reconnection Strategy

The SDK implements automatic reconnection with exponential backoff and jitter:

Parameter	Value
Initial delay	1,000 ms
Maximum delay	10,000 ms
Backoff formula	`min(1000 * 2^attempt, 10000)`
Jitter	+/- 25% of the computed delay
Maximum attempts	30

Reconnection Rules

Reconnects on: Network errors, unexpected disconnects, heartbeat timeouts
Does not reconnect on: Auth errors (4001, 4002, 4003, 4004), clean close, explicit disconnect() call
Attempt counter resets: On successful connection (before auth)
Network awareness: Listens for browser online/offline events; reconnects when the network comes back

Session Restore on Reconnect

When the client reconnects with a conversation_id:

Server loads the session from Redis (if still within the 1-hour TTL)
Server sends a session_restored message with cart state and any pending tool
Client can continue the conversation seamlessly

If the Redis session has expired, the server creates a new conversation.

Heartbeat

Both client and server send periodic heartbeat messages to detect dead connections:

Side	Interval	Timeout	Message
Client	30s	—	`{"type": "ping"}`
Server	30s	60s	`{"type": "ping"}`

The server closes the connection with code 4008 if no pong is received within 60 seconds.

Message Size Limits

Limit	Value	Enforced By
Client message	64 KB	SDK (pre-send check) and server
Message queue	50 messages	SDK (client-side queue during disconnect)

The SDK checks message size before sending and returns a message_too_large error via onError without transmitting the message. The server also enforces the 64 KB limit and responds with an error if exceeded.

Origin Validation

The server checks the Origin header of the WebSocket connection against the configured allowed origins list:

If the origin is not in the allowed list, the connection is closed with code 4003
This prevents unauthorized websites from connecting to the WebSocket API
The origin list is configured via the CORS_ORIGINS environment variable

Due to a Starlette/FastAPI limitation, the WebSocket must be accepted before the origin can be checked. The connection is accepted first, then immediately closed with a custom code if the origin is not allowed.

​Overview

​Connection Lifecycle

​Endpoint

​Client to Server Messages

​auth

​message

​action

​ping

​pong

​Server to Client Messages

​auth_ok

​conversation_started

​session_restored

​text_delta

​text_end

​text

​status

​product_cards

​quick_replies

​confirmation

​ingredient_checklist

​meal_plan

​session_summary

​cart_changed

​response_complete

​error

​event

​ping / pong

​Close Codes

​Reconnection Strategy

​Reconnection Rules

​Session Restore on Reconnect

​Heartbeat

​Message Size Limits

​Origin Validation

Overview

Connection Lifecycle

Endpoint

Client to Server Messages

auth

message

action

ping

pong

Server to Client Messages

auth_ok

conversation_started

session_restored

text_delta

text_end

text

status

product_cards

quick_replies

confirmation

ingredient_checklist

meal_plan

session_summary

cart_changed

response_complete

error

event

ping / pong

Close Codes

Reconnection Strategy

Reconnection Rules

Session Restore on Reconnect

Heartbeat

Message Size Limits

Origin Validation