Real-Time Notifications

Overview

Knowledge Stack provides two real-time communication channels:

WebSocket — For receiving instant notifications about events in your tenant (e.g., document ingestion completed)
Server-Sent Events (SSE) — For streaming AI assistant responses token-by-token

Both channels use Redis Streams as the underlying message transport, which enables horizontal scaling across multiple server instances.

WebSocket Notifications

Connecting

Connect to the WebSocket endpoint at:

WS /v1/ws

Authentication is handled automatically via your session cookie (ks_uat). On a successful connection, you will receive a confirmation message:

{
  "type": "system",
  "event": "connection_established",
  "connection_id": "abc-123",
  "user_id": "...",
  "tenant_id": "..."
}

Subscribing to Channels

After connecting, subscribe to notification channels by sending JSON messages:

{"action": "subscribe", "channel": "ks:{tenant_id}:notifications"}

You can also subscribe to user-specific notifications:

{"action": "subscribe", "channel": "ks:{tenant_id}:users:{user_id}"}

To unsubscribe:

{"action": "unsubscribe", "channel": "ks:{tenant_id}:notifications"}

Channel Security

Two security rules are enforced on all subscriptions:

The tenant_id in the channel must match your authenticated tenant
For user channels, the user_id must match your authenticated user

Notification Events

Event	Description	Key Fields
`document_ingestion_completed`	A document has finished processing	`document_id`, `document_version_id`, `workflow_id`

Server Messages

Event	Description
`connection_established`	Connection accepted, includes your `connection_id`
`subscribed`	Successfully subscribed to a channel
`unsubscribed`	Successfully unsubscribed from a channel
`error`	An error occurred (includes `code` and `message`)

Connection Close Codes

Code	Meaning
4401	Unauthorized — invalid or missing session
4403	Forbidden — you are not a member of this tenant
4503	Service unavailable — real-time features are disabled
1001	Server shutting down

Keepalive

The connection uses standard WebSocket ping/pong frames (RFC 6455) for keepalive. No application-level heartbeat is needed.

SSE Thread Streaming

Endpoint

GET /v1/threads/{thread_id}/stream

Authentication uses standard REST authentication (session cookie).

Query Parameters

Parameter	Type	Required	Description
`last_message_id`	UUID	No	The ID of the last message you received. Used for reconnection.
`last_entry_id`	string	No	The stream entry ID of the last event you received. Required when `last_message_id` is provided.

Streaming Events

When the AI assistant generates a response, you receive a sequence of SSE events:

Event	Description
`message_start`	A new assistant message is beginning
`text_start`	A text segment is starting
`text_delta`	A chunk of text content (the `delta` field contains the text)
`text_end`	The current text segment is complete
`step`	A tool call or processing step occurred
`citations`	Source citations for the response
`message_end`	The assistant message is complete
`done`	The stream is finished (`data: [DONE]`)

The typical event lifecycle is:

message_start -> text_start -> text_delta* -> text_end -> citations? -> message_end -> done

Tool call step events may be interleaved during processing.

SSE Event Format

Each event follows this format:

id: 1706000000000-5
event: text_delta
data: {"delta":"Hello","id":"msg-uuid","part_id":"part-uuid","ts":"2026-02-17T10:30:00Z","message_id":"msg-uuid"}

Reconnection

If your connection drops while an assistant response is still streaming, you can reconnect with replay:

GET /v1/threads/{thread_id}/stream?last_message_id=abc&last_entry_id=1706000000000-5

Knowledge Stack will replay any events you missed and then continue with live events. You will receive a replay_complete event when replay is finished:

event: replay_complete
data: {"replayed_count":12,"last_entry_id":"1706000000000-50"}

If the message has already finished streaming when you reconnect, you will receive a message_not_streaming event instead. In that case, fetch the complete message via the REST API:

GET /v1/threads/{thread_id}/messages/{message_id}

Best Practices for SSE

Open a new SSE connection when you navigate to a thread
For reconnection mid-stream, always include both last_message_id and last_entry_id
Do not rely on EventSource auto-reconnect — close the connection and open a new one with updated parameters
The stream self-terminates when done. Open a new connection for the next message.

SSE Keepalive

The server sends SSE comment pings (: ping) every 30 seconds to keep the connection alive.

Configuration

If you are self-hosting Knowledge Stack, these settings control the real-time notification system:

Setting	Default	Environment Variable	Description
Redis URL	`DISABLED`	`REDIS_URL`	Redis connection string. Set to `DISABLED` to turn off real-time features.
Max connections	`20`	`REDIS_MAX_CONNECTIONS`	Redis connection pool size
Stream TTL	`30` min	`WS_STREAM_TTL_MINUTES`	How long stream entries are retained
SSE buffer size	`1024`	`SSE_QUEUE_SIZE`	Maximum buffered events per subscriber

Error Handling

Scenario	What Happens
Redis is disabled	WebSocket returns close code 4503. SSE returns an error.
Redis goes down during use	The system automatically retries with exponential backoff
Your SSE client disconnects	Your subscription is cleaned up automatically
SSE buffer fills up	Your subscription is removed to prevent memory issues
Message is no longer streaming	SSE returns `message_not_streaming` — fetch the message via REST instead

Get Started

SDKs & MCP

Cookbook

Concepts

Ingestion Pipeline

Agent

Infrastructure

Design

Operations

Overview

WebSocket Notifications

Connecting

Subscribing to Channels

Channel Security

Notification Events

Server Messages

Connection Close Codes

Keepalive

SSE Thread Streaming

Endpoint

Query Parameters

Streaming Events

SSE Event Format

Reconnection

Best Practices for SSE

SSE Keepalive

Configuration

Error Handling

​Overview

​WebSocket Notifications

​Connecting

​Subscribing to Channels

​Channel Security

​Notification Events

​Server Messages

​Connection Close Codes

​Keepalive

​SSE Thread Streaming

​Endpoint

​Query Parameters

​Streaming Events

​SSE Event Format

​Reconnection

​Best Practices for SSE

​SSE Keepalive

​Configuration

​Error Handling

Overview

WebSocket Notifications

Connecting

Subscribing to Channels

Channel Security

Notification Events

Server Messages

Connection Close Codes

Keepalive

SSE Thread Streaming

Endpoint

Query Parameters

Streaming Events

SSE Event Format

Reconnection

Best Practices for SSE

SSE Keepalive

Configuration

Error Handling