langchain-ai/langchain · error · ValueError

Box dimensions should be > 1

Error message

Box dimensions should be > 1

What it means

Raised by AsciiCanvas.box() when width or height is <= 1. Boxes (node frames) must span at least 2 columns and 2 lines so the border has an interior. The width/height come from the vertex view produced by the grandalf sugiyama layout, so a node whose computed w/h collapsed to 1 triggers this while drawing.

Source

Thrown at libs/core/langchain_core/runnables/graph_ascii.py:174

        """
        for i, char in enumerate(text):
            self.point(x + i, y, char)

    def box(self, x0: int, y0: int, width: int, height: int) -> None:
        """Create a box on ASCII canvas.

        Args:
            x0: x coordinate of the box corner.
            y0: y coordinate of the box corner.
            width: box width.
            height: box height.

        Raises:
            ValueError: if box dimensions are invalid.
        """
        if width <= 1 or height <= 1:
            msg = "Box dimensions should be > 1"
            raise ValueError(msg)

        width -= 1
        height -= 1

        for x in range(x0, x0 + width):
            self.point(x, y0, "-")
            self.point(x, y0 + height, "-")

        for y in range(y0, y0 + height):
            self.point(x0, y, "|")
            self.point(x0 + width, y, "|")

        self.point(x0, y0, "+")
        self.point(x0 + width, y0, "+")
        self.point(x0, y0 + height, "+")
        self.point(x0 + width, y0 + height, "+")

View on GitHub (pinned to e32fa9a52e)

Solutions

1. If calling box() directly, pass width >= 2 and height >= 2
2. Shorten or simplify node names so the layout gives each node a non-degenerate size
3. Fall back to graph.draw_mermaid() or draw_mermaid_png() instead of draw_ascii()
4. Report as a langchain bug if a default graph triggers it

Example fix

// before
canvas.box(x, y, 1, h)
// after
canvas.box(x, y, max(2, w), max(2, h))

if width < 2 or height < 2:
    raise ValueError("box needs width >= 2 and height >= 2")

def valid_box(w: int, h: int) -> bool:
    return w > 1 and h > 1

try:
    graph.draw_ascii()
except ValueError:
    graph.draw_mermaid()

When it happens

Trigger: Calling draw_ascii() on a graph where a vertex view has w <= 1 or h <= 1 (degenerate layout); direct AsciiCanvas.box(x0, y0, width, height) calls with width or height <= 1.

Common situations: Custom node labels or graphs that make the layout engine compute degenerate box sizes; manual canvas usage. Rare for normal chains using draw_ascii().

Related errors

• y should be >= 0 and < number of lines
• Not enough points to draw an edge
• Invalid edge coordinates: start_x={start_x}, start_y={start_
• 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/447ee7e891d996a8. Report an issue: GitHub.