Explicit node coordinates (x/y positions) not fully respected in Sankey diagram

We (@janosh) are trying to generate a Sankey diagram but for some reason the explicit coordinates are not fully respected. The "right_a" node has a coordinate of (0.9, 0.05) (top right), but for some reason shows at bottom left.

plotly 6.3.1, macos 26.0.1

import plotly.graph_objects as go


labels = ["left_a", "left_b", "left_c", "left_d", "left_e", "left_f", "left_g", "left_h", "left_i", "left_j", "left_k", "left_l", "left_m",
    "left_n", "left_o", "left_p", "left_q", "left_r",
    "right_a", "right_b", "right_c", "right_d", "right_e", "right_f", "right_g", "right_h", "right_i", "right_j", "right_k", "right_l"]

node_pos = {
    "left_a": (0.1, 0.1), "left_b": (0.1, 0.14), "left_c": (0.1, 0.18), "left_d": (0.1, 0.23),
    "left_e": (0.1, 0.27), "left_f": (0.1, 0.31), "left_g": (0.1, 0.35),
    "left_h": (0.1, 0.40), "left_i": (0.1, 0.44), "left_j": (0.1, 0.48),
    "left_k": (0.1, 0.52), "left_l": (0.1, 0.56), "left_m": (0.1, 0.61),
    "left_n": (0.1, 0.65), "left_o": (0.1, 0.69), "left_p": (0.1, 0.73),
    "left_q": (0.1, 0.77), "left_r": (0.1, 0.82),
    "right_a": (0.9, 0.05),
    "right_b": (0.9, 0.15), "right_c": (0.9, 0.25), "right_d": (0.9, 0.35), "right_e": (0.9, 0.45), "right_f": (0.9, 0.55), "right_g": (0.9, 0.65),
    "right_h": (0.9, 0.75), "right_i": (0.9, 0.85), "right_j": (0.9, 0.93), "right_k": (0.9, 0.97), "right_l": (0.9, 0.99)}

sources = [0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 3, 3, 3, 3, 4, 4, 4, 5, 5, 5, 5, 5, 6, 6, 6, 6, 7, 7, 7, 7, 7, 8, 9, 9, 9, 9, 9, 9, 9, 9, 10,
    10, 10, 11, 12, 13, 13, 13, 13, 13, 13, 14, 14, 14, 14, 14, 14, 14, 14, 14, 15, 15, 15, 15, 15, 15, 16, 16, 16, 18, 18, 18, 19, 19, 19, 19, ]

targets = [23, 21, 20, 26, 30, 20, 24, 22, 21, 20, 20, 25, 29, 22, 22, 29, 20, 20, 22, 25, 24, 29, 20, 22, 29, 21, 21, 20, 24, 30, 22,
    20, 20, 21, 25, 22, 30, 28, 24, 29, 20, 21, 24, 20, 20, 22, 20, 23, 21, 24, 31, 25, 21, 22, 20, 23, 30, 27, 26, 24, 21, 20, 22,
    23, 30, 25, 20, 21, 22, 20, 21, 25, 20, 22, 21, 24, ]
values = [1 for _ in targets]
assert len(sources) == len(targets) == len(values)

x_positions: list[float] = [node_pos[lbl][0] for lbl in labels]
y_positions: list[float] = [node_pos[lbl][1] for lbl in labels]

fig = go.Figure(
    go.Sankey(
        arrangement="fixed",
        node=dict(
            label=labels,
            x=x_positions,
            y=y_positions,
        ),
        link=dict(
            source=sources,
            target=targets,
            value=values,
        ),
    )
)

# fig.show()

fig.write_image("debug.svg", format="svg")

Start by running the provided Sankey reproduction with arrangement="fixed" and exporting debug.svg, then trace the Sankey implementation and its handling of node x/y coordinates. Done means explicit coordinates such as right_a at (0.9, 0.05) are reflected in the rendered diagram without regressing other fixed-position nodes.