name: trip-agent description: | Build and modify the Trip Assistant LangGraph agent with topic-based routing. Use when: (1) Adding or modifying classifier/specialist nodes, (2) Updating TripAssistantState schema, (3) Changing graph routing logic, (4) Adding new trip topics/specialists, (5) Working with document loading, (6) Writing or debugging tests for nodes or graph, (7) Any task involving the agent/ folder.

Trip Assistant Agent Development

Architecture

START → Classifier → Router → [Specialist Nodes] → END

The classifier analyzes user queries and routes to topic-specific specialist nodes.

Core Patterns

State Schema (src/state.py)

from typing import Annotated, Literal
from typing_extensions import TypedDict
from langgraph.graph.message import add_messages

class TripAssistantState(TypedDict):
    messages: Annotated[list, add_messages]
    topic: Literal["flights", "hotels", "activities", ...] | None
    # Add fields as needed for routing context

Graph Structure (src/graph.py)

from langgraph.graph import StateGraph, START, END

graph = StateGraph(TripAssistantState)
graph.add_node("classifier", classify_query)
graph.add_node("flights_specialist", handle_flights)
graph.add_node("hotels_specialist", handle_hotels)
# ... other specialists

graph.add_edge(START, "classifier")
graph.add_conditional_edges("classifier", route_by_topic, {
    "flights": "flights_specialist",
    "hotels": "hotels_specialist",
    # ... other routes
})
graph.add_edge("flights_specialist", END)
# ... other edges to END

app = graph.compile()

Routing Function

def route_by_topic(state: TripAssistantState) -> str:
    return state["topic"]  # Returns node name based on classified topic

Adding a New Specialist

1. Create node function in src/nodes/<topic>_specialist.py
2. Add topic to TripAssistantState.topic Literal type
3. Register node in graph.py: graph.add_node("<topic>_specialist", handler)
4. Add routing edge: "<topic>": "<topic>_specialist"
5. Add edge to END: graph.add_edge("<topic>_specialist", END)
6. Write tests first (TDD)

Document Loading (src/documents.py)

Trip data lives in data/*.txt. Load documents for RAG context:

from pathlib import Path

def load_trip_docs() -> list[str]:
    data_dir = Path(__file__).parent.parent / "data"
    return [f.read_text() for f in data_dir.glob("*.txt")]

Testing (TDD Required)

Always write tests first:

# tests/test_<node_name>.py
def test_classifier_routes_flight_query():
    state = {"messages": [HumanMessage(content="What time is my flight?")]}
    result = classify_query(state)
    assert result["topic"] == "flights"

Run: pytest tests/ -v

References

• Node patterns: See references/node-patterns.md for classifier and specialist implementation details
• Testing patterns: See references/testing-patterns.md for TDD patterns and fixtures

Quality Checks

Before committing:

pre-commit run --all-files
mypy src/
pytest tests/ -v