langgraph-events 0.5.0

Opinionated event-driven abstraction for LangGraph. State IS events.

langgraph-events

Opinionated event-driven abstraction for LangGraph. State IS events.

[!CAUTION] Experimental (v0.5.0) - This is an early-stage personal project, not a supported product. The API will change without notice or migration path.

Quick Start

Group related commands and events into a Namespace; colocate the handler on the command.

from langgraph_events import Command, Domain, DomainEvent, EventGraph


class Order(Namespace):
    class Place(Command):
        customer_id: str

        class Placed(DomainEvent):
            order_id: str

        def handle(self) -> Placed:
            return Order.Place.Placed(order_id=f"o-{self.customer_id}")


graph = EventGraph([Order.Place])
log = graph.invoke(Order.Place(customer_id="alice"))
print(log.latest(Order.Place.Placed))

External @on(...) handlers compose in the same graph — use them for invariants, declared exceptions, or reactions across domains. See Concepts and Control Flow.

Installation

pip install langgraph-events

# With AG-UI adapter support
pip install "langgraph-events[agui]"

# From source (development)
pip install git+https://github.com/cadance-io/langgraph-events.git

Documentation

• Docs site (GitHub Pages): https://cadance-io.github.io/langgraph-events/
• Local docs index: docs/index.md
• Getting started: docs/getting-started.md
• Core concepts: docs/concepts.md
• Patterns: docs/patterns.md
• API reference: docs/api.md
• AG-UI adapter: docs/agui.md
• Checkpointer and graph evolution: docs/checkpointer-evolution.md

Development

uv sync --group dev
uv run pytest tests/
uv run ruff check src/ tests/
uv run mypy src/

License

MIT - see LICENSE.