fix: LangGraph Executor HITL and E2E Tests

[supreme-gg-gg]

See https://docs.langchain.com/oss/python/langgraph/interrupts for how HITL works in langgraph.

Tested the new HITL flow with a langgraph BYO agent and it works. However, unlike ADK declarative where you can just specify tools requiring approval in CRD, the developer using kagent-langgraph will need to setup their graph in a specific way following the above documentation. Most existing graphs using interrupt() mechanism should be compatible, but a more comprehensive testing would help to fully verify it especially for complex graphs.

I have provided an example in the samples folder to show how to do that for starters.

[Copilot]

Pull request overview

Updates the LangGraph BYO executor’s HITL interrupt/resume wiring and adds an E2E test + sample updates to validate invoking a LangGraph-based agent using a mocked OpenAI endpoint.

Changes:

• Switch LangGraph currency sample from langchain-google-genai/Gemini to langchain-openai/OpenAI and update related config/secrets.
• Rework kagent-langgraph executor interrupt handling to emit adk_request_confirmation-shaped DataParts and forward richer resume payloads.
• Add a new Go E2E test and mock responses for invoking the LangGraph currency agent; update Makefile to build/push the sample image.

Reviewed changes

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
python/uv.lock	Lockfile update reflecting dependency switch to langchain-openai and related resolution changes.
python/samples/langgraph/currency/pyproject.toml	Replace langchain-google-genai dependency with langchain-openai.
python/samples/langgraph/currency/currency/agent.py	Swap model provider to ChatOpenAI and update model name.
python/samples/langgraph/currency/agent.yaml	Update env var and secret refs from Google to OpenAI.
python/packages/kagent-langgraph/src/kagent/langgraph/_executor.py	Implement LangGraph-specific HITL interrupt event emission and richer resume payload forwarding.
go/core/test/e2e/mocks/invoke_langgraph_agent.json	Add mock OpenAI chat-completions for the currency sample flow.
go/core/test/e2e/invoke_api_test.go	Add E2E test that deploys and invokes the LangGraph currency agent (sync + streaming).
Makefile	Build/push the langgraph-currency sample image in push-test-agent.

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[supreme-gg-gg]

Note to users: interrupt allows the user to set arbitrary data in the graph state, this can literally be anything you want, as long as it matches the response in Command (this is unlike the HITL mechanism in ADK which only has specific fields). However, in order for our executor to work with our HITL flow we require your interrupt function to be called with the specific structure below.

This is not a limitation, you are welcome to use any interrupt mechanisms, you will just need to modify the executor to handle that specific response and convert that to a protocol message in Kagent's HITL flow documented in docs/architecture/human-in-the-loop.md. The default Kagent HITL flow is not as versatile as langgraph because it's designed around ADK rather than langgraph.

In ADK, HITL will propagate through subagents, but since our langgraph SDK does not yet support "subgraphs", that feature will not be available here. You can implement this yourself using the same logic.