langgraph

langgraph-governed-agent

Demonstrates how to integrate Agent Assembly with LangGraph to enforce governance policy on the tools a graph's nodes call — before any tool executes.

What this example demonstrates

• Initializing Agent Assembly with init_assembly() in offline sdk-only mode.
• Installing node-level governance hooks with LangGraphAdapter, which wraps a compiled StateGraph's nodes.
• Routing tool calls through LangChain's AssemblyCallbackHandler so each tool is checked against policy.
• A linear graph START → research → report → END where:
  • research calls an allowed tool (get_weather).
  • report calls a denied tool (delete_files — blocked by policy).
• How ToolExecutionBlockedError halts the graph the moment a blocked tool is reached.

The example runs fully offline: the graph is driven with deterministic nodes, so no LLM, API key, or running gateway is required.

Prerequisites

Requirement	Version
Python	>= 3.12
uv	latest
Agent Assembly Python SDK	>= 0.0.1b2

No running Agent Assembly gateway is required for the offline demo.

Setup

cd python/langgraph
uv sync --extra dev

Run

uv run python src/main.py

Expected output

==============================================================
  Agent Assembly — LangGraph Governed Agent Demo
==============================================================

Initializing Agent Assembly (gateway: http://localhost:8080, sdk-only mode)...
  Agent:    langgraph-demo-agent
  Gateway:  http://localhost:8080
  Mode:     sdk-only (offline demo)

Policy rules (local simulation of gateway policy):
  DENY    — delete_files, write_file  (destructive operations)
  PENDING — send_email                (requires human approval)
  ALLOW   — everything else

Invoking governed graph: START → research → report → END
--------------------------------------------
  → research node: get_weather
     ✅ ALLOWED  — gathered notes (mock response)
  → report node: delete_files
     ❌ BLOCKED  — Tool 'delete_files' is blocked by policy rule 'deny_destructive_operations'.

Assembly context shut down.

Run tests

uv run pytest tests/ -v

Switching to production mode

1. Start an Agent Assembly gateway or use your SaaS workspace URL.
2. Copy .env.example to .env and fill in your credentials.
3. Run with gateway environment variables:

AGENT_ASSEMBLY_GATEWAY_URL=http://localhost:8080 \
AGENT_ASSEMBLY_API_KEY=your-key \
uv run python src/main.py

In production, init_assembly() auto-detects LangGraph and registers the adapter automatically, and the gateway enforces the policy rules — replace LocalPolicyEngine with the gateway-backed interceptor.

Troubleshooting

Problem	Fix
ModuleNotFoundError: agent_assembly	Run uv sync first
ModuleNotFoundError: langgraph	Run uv sync — langgraph is a required dependency
ToolExecutionBlockedError in tests	Expected — the deny/pending policy rules are intentional

Links

• Agent Assembly Python SDK
• Agent Assembly Examples
• Python Examples