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Bridges connect your nodes to the event system.

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What is a Bridge?

Bridges are event transport that sit between the Nodes and the Bus. Messages are received and sent on the Bridge. You can subscribe to specific event types on a Bridge and execute actions when those events occur. When subscribing to an event type, you create a Route, which runs when an event of that type is received on the bridge.

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Basic Example

from line import Bridge
from line.events import UserStoppedSpeaking

# Create bridge for your node
bridge = Bridge(chat_node)

# Define route: when user stops speaking, generate response.
bridge.on(UserStoppedSpeaking).map(chat_node.generate)

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Key Concepts

Event Patterns: Patterns that match events (e.g., UserTranscriptionReceived, ToolCall, "*" for all events). Actions: What to do when an event matches (e.g., call a node method, transform data, broadcast new events). Filtering: Additional criteria for when routes should trigger (source, event properties, custom functions).

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Event Patterns

# Match specific event type
bridge.on(UserTranscriptionReceived).map(handle_user_input)

# Match all events with wildcard
bridge.on("*").map(log_all_events)

# Filter by source
bridge.on(AgentResponse, source="main_agent").map(send_to_user)

# Custom filtering
bridge.on(
    ToolCall,
    filter_fn=lambda msg: msg.event.tool_name == "calculator",
).map(handle_calc)