langchain-ai/langchain · error · ValueError

Invalid edge coordinates: start_x={start_x}, start_y={start_

Error message

Invalid edge coordinates: start_x={start_x}, start_y={start_y}, end_x={end_x}, end_y={end_y}

What it means

Before drawing each edge segment, draw_ascii() subtracts the graph-wide minimum x/y offsets and rounds; if any resulting coordinate is negative it raises this ValueError with the offending coordinates. Negative values mean the layout placed part of an edge left/above the minimum corner, i.e. inconsistent geometry or a rounding artifact.

Source

Thrown at libs/core/langchain_core/runnables/graph_ascii.py:348

            raise ValueError(msg)
        for index in range(1, len(edge.view.pts)):
            start = edge.view.pts[index - 1]
            end = edge.view.pts[index]

            start_x = round(start[0] - minx)
            start_y = round(start[1] - miny)
            end_x = round(end[0] - minx)
            end_y = round(end[1] - miny)

            if start_x < 0 or start_y < 0 or end_x < 0 or end_y < 0:
                msg = (
                    "Invalid edge coordinates: "
                    f"start_x={start_x}, "
                    f"start_y={start_y}, "
                    f"end_x={end_x}, "
                    f"end_y={end_y}"
                )
                raise ValueError(msg)

            canvas.line(start_x, start_y, end_x, end_y, "." if edge.data else "*")

    for vertex in sug.g.sV:
        # NOTE: moving boxes w/2 to the left
        x = vertex.view.xy[0] - vertex.view.w / 2.0
        y = vertex.view.xy[1]

        canvas.box(
            round(x - minx),
            round(y - miny),
            vertex.view.w,
            vertex.view.h,
        )

        canvas.text(round(x - minx) + 1, round(y - miny) + 1, vertex.data)

    return canvas.draw()

View on GitHub (pinned to e32fa9a52e)

Solutions

1. Retry with draw_mermaid() which does not use this code path
2. Upgrade langchain-core and grandalf (layout rounding fixes land over time)
3. Slightly change the graph (node labels/edges) to shift layout coordinates off the boundary
4. Report as a bug with a minimal reproducer

try:
    graph.draw_ascii()
except ValueError as e:
    if "Invalid edge coordinates" in str(e):
        art = graph.draw_mermaid()

When it happens

Trigger: graph.draw_ascii() when round(point - minx/miny) goes negative for an edge point — floating-point rounding right at a boundary or inconsistent layout minima.

Common situations: Edge case in the grandalf layout for particular graph shapes; not user-controllable via public API. Rare.

Related errors

• Not enough points to draw an edge
• y should be >= 0 and < number of lines
• Box dimensions should be > 1
• Install grandalf to draw graphs: `pip install grandalf`.
• Found duplicate subgraph '{subgraph}' -- this likely means t

AI-assisted analysis of langchain-ai/langchain@e32fa9a52e (2026-08-14). Data as JSON: /api/errors/e8e73013391b229a. Report an issue: GitHub.