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Connect LangGraph

koel_langgraph bridges a LangGraph backend, including first-class interrupt/resume surfacing.

import 'package:koel_core/koel_core.dart' show KoelClient;
import 'package:koel_langgraph/koel_langgraph.dart' show LangGraphAgent;

final client = KoelClient(
  agent: LangGraphAgent(
    deploymentUrl: Uri.parse('http://localhost:8003/agent'),
  ),
);

final session = client.newSession();
await session.send('Draft a release note');

The deployment URL is used verbatim​

deploymentUrl is the full AG-UI POST endpoint — nothing is appended. Unlike a base URL, LangGraph's route path is caller-configured (add_langgraph_fastapi_endpoint(..., path: ...)), so koel assumes no canonical suffix. Pass the exact endpoint your deployment exposes.

Authentication​

LangGraph ships no built-in auth on its AG-UI route, so apiKey is optional — with apiKey == null (the default) or a blank value the interceptor is a no-op, the right default for an open local deployment. Pass an apiKey only when your deployment enforces one (returning 401/403/429, mapped to businessAuth/businessForbidden/businessRateLimited):

final agent = LangGraphAgent(
  deploymentUrl: Uri.parse('https://my-langgraph.example/agent'),
  apiKey: 'xyz',
);

The key is trimmed and injected as the x-api-key header, prepended outermost so a caller-supplied inner auth wins the merge.

Interrupt / resume​

When a LangGraph run pauses on an interrupt, koel surfaces it as a CUSTOM event and you reopen the run on the same thread — see Interrupt & resume.