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- **Description:** Currently, `langchain_core.runnables.graph_mermaid.py` is hardcoded to use mermaid.ink to render graph diagrams. It would be nice to allow users to specify a custom URL, e.g. for self-hosted instances of the Mermaid server. - **Issue:** [Langchain Forum: allow custom mermaid API URL](https://forum.langchain.com/t/feature-request-allow-custom-mermaid-api-url/1472) - **Dependencies:** None - [X] **Add tests and docs**: Added unit tests using mock requests. - [X] **Lint and test**: Run `make format`, `make lint` and `make test`. Minimal example using the feature: ```python import os import operator from pathlib import Path from typing import Any, Annotated, TypedDict from langgraph.graph import StateGraph class State(TypedDict): messages: Annotated[list[dict[str, Any]], operator.add] def hello_node(state: State) -> State: return {"messages": [{"role": "assistant", "content": "pong!"}]} builder = StateGraph(State) builder.add_node("hello_node", hello_node) builder.add_edge("__start__", "hello_node") builder.add_edge("hello_node", "__end__") graph = builder.compile() # Run graph output = graph.invoke({"messages": [{"role": "user", "content": "ping?"}]}) # Draw graph Path("graph.png").write_bytes(graph.get_graph().draw_mermaid_png(base_url="https://custom-mermaid.ink")) ``` --------- Co-authored-by: Eugene Yurtsev <eyurtsev@gmail.com>