LangChain¶

SchemaRouter integrates with LangChain as an optional boundary, not as a replacement for the LangChain runtime.

Install¶

For consumers:

pip install "schemarouter[langchain]"

For repository development:

pip install -e ".[dev,langchain]"

The core package does not depend on LangChain.

Export registered endpoints¶

from schemarouter.integrations import to_langchain_tools

tools = to_langchain_tools(router)

Each registered endpoint becomes a LangChain StructuredTool with its SchemaRouter input schema.

To expose one endpoint:

from schemarouter.integrations import to_langchain_tool

tool = to_langchain_tool(
    router,
    "weather",
    "current",
)

Runnable example¶

The repository includes a minimal executable integration example:

python examples/langchain_quickstart.py

CI runs this example in addition to the dedicated integration tests, so the documented bridge is kept executable.

Execution still flows through SchemaRouter¶

The integration does not call the original transport directly.

LangChain StructuredTool
 -> SchemaRouter ToolCall
 -> current schema validation
 -> ExecutionPolicy
 -> binding-drift check
 -> trusted invoker
 -> output validation

This means a LangChain agent gains the same fail-closed contracts as direct SchemaRouter usage.

Division of responsibility¶

A useful composition is:

Concern	Owner
Agent graph / conversation	LangChain or LangGraph
Model invocation	Surrounding framework/application
Tool catalog schema	SchemaRouter
Endpoint/argument/field plan	SchemaRouter
Side-effect policy	SchemaRouter local policy
Tool execution validation	SchemaRouter
Checkpointing / memory	Surrounding framework

SchemaRouter should not duplicate the graph runtime merely to integrate with it.

For direct StateGraph integration, see LangGraph.

Packaging¶

The bridge currently stays in the main distribution behind the langchain extra. A separate langchain-schemarouter package is intentionally deferred until an independent release cadence, material dependency pressure, or an upstream ecosystem requirement justifies the split.

See Compatibility testing for the supported range and maintenance policy.