Tutorial 3: Coding Agent

from typing import TypedDict, Annotated
from langgraph.graph import StateGraph, START
from langgraph.graph.message import add_messages
from langchain_ollama import ChatOllama

# Setup model
llm = ChatOllama(
    model="qwen2.5-coder:7b",
    base_url="http://localhost:11434"
)

# Define state
class AgentState(TypedDict):
    messages: Annotated[list, add_messages]

# Simple agent node
def call_model(state: AgentState):
    response = llm.invoke(state["messages"])
    return {"messages": [response]}

# Build the graph
graph = StateGraph(AgentState)
graph.add_node("agent", call_model)
graph.add_edge(START, "agent")
agent = graph.compile()

# Use it
result = agent.invoke({
    "messages": [("user", "Review this code and suggest fixes: def add(a,b): return a-b")]
})
print(result["messages"][-1].content)

from langchain_core.tools import tool
from langgraph.prebuilt import ToolNode, tools_condition

# Define tools
@tool
def read_file(path: str) -> str:
    """Read a file from disk"""
    with open(path) as f:
        return f.read()

@tool
def run_tests(path: str) -> str:
    """Run pytest on a file"""
    import subprocess
    try:
        r = subprocess.run(["pytest", path, "-v"],
            capture_output=True, text=True, timeout=30)
        return r.stdout + r.stderr
    except subprocess.TimeoutExpired:
        return "Tests timed out"

# Bind tools to model
tools = [read_file, run_tests]
llm_with_tools = llm.bind_tools(tools)

# Agent node
def agent_node(state: AgentState):
    return {"messages": [llm_with_tools.invoke(state["messages"])]}

# Build graph with tools
graph = StateGraph(AgentState)
graph.add_node("agent", agent_node)
graph.add_node("tools", ToolNode(tools))
graph.add_edge(START, "agent")
graph.add_conditional_edges("agent", tools_condition, {"tools": "tools", "__end__": "__end__"})
graph.add_edge("tools", "agent")

coding_agent = graph.compile()

# Use it
result = coding_agent.invoke({
    "messages": [("user", "Write a fibonacci function, save it to fib.py, and test it")]
})
print(result["messages"][-1].content)