diff --git a/papers/colored_edge_flip_classes/experiments/colored_edge_flip_class_survey.py b/papers/colored_edge_flip_classes/experiments/colored_edge_flip_class_survey.py
index 43f569c..bedd41a 100644
--- a/papers/colored_edge_flip_classes/experiments/colored_edge_flip_class_survey.py
+++ b/papers/colored_edge_flip_classes/experiments/colored_edge_flip_class_survey.py
@@ -15,6 +15,8 @@ For each min-degree-5 maximal planar graph G of order n:
 If for some (H, phi) a graph isomorphic to G is reached, G is "found" and we
 move on. Otherwise we save G and stop.
 """
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
 from typing import Iterator, Any, cast
 from sage.all import Graph, graphs  # type: ignore[attr-defined]  # pylint: disable=no-name-in-module
 from sage.graphs.graph_coloring import all_graph_colorings  # type: ignore[attr-defined]  # pylint: disable=no-name-in-module
diff --git a/papers/colored_pentagon_contractions/experiments/colored_pentagon_contractions.py b/papers/colored_pentagon_contractions/experiments/colored_pentagon_contractions.py
index 5c75d24..192522b 100644
--- a/papers/colored_pentagon_contractions/experiments/colored_pentagon_contractions.py
+++ b/papers/colored_pentagon_contractions/experiments/colored_pentagon_contractions.py
@@ -1,4 +1,6 @@
 """Example: colored pentagon reduction on a random 20-vertex triangulation."""
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
 from collections import defaultdict
 from pathlib import Path
 from typing import Any, cast, TypedDict, Literal
diff --git a/papers/plane_depth_sequencing/experiments/draw_quad_sequence.py b/papers/plane_depth_sequencing/experiments/draw_quad_sequence.py
new file mode 100644
index 0000000..2fad927
--- /dev/null
+++ b/papers/plane_depth_sequencing/experiments/draw_quad_sequence.py
@@ -0,0 +1,278 @@
+"""Draw a graph with quadrilateral sequence diagram for the plane depth sequencing paper.
+
+Usage:
+  sage draw_quad_sequence.py --seed 42 --n 7 --output quad_sequence.png
+"""
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))  # sibling experiment modules
+from PIL import Image, ImageDraw
+import argparse
+from pathlib import Path
+from sage.all import graphs, Graph  # type: ignore
+from sage.misc.randstate import set_random_seed  # type: ignore
+from plane_depth_sequencing import (
+    quadrilateral_sequencing,
+    _quad_vertices,
+    _level_edge_of_face,
+    _quad_type,
+    get_plane_depth_labelling,
+)
+from lib.tutte_embedding import tutte_embedding
+
+
+def generate_sequence(seed: int, n: int) -> tuple[list[dict], dict, Graph, list, Graph]:
+    """Generate a quadrilateral sequence and return (sequence_data, depth_labelling, original_graph, outer_cycle, deep_embedding_graph)."""
+    set_random_seed(seed)
+    g = graphs.RandomTriangulation(n)
+    g.is_planar(set_embedding=True)
+    embedding = g.get_embedding()
+    faces = g.faces(embedding)
+    outer_cycle = [u for u, _ in faces[0]]
+
+    result = quadrilateral_sequencing(g, outer_cycle)
+    sequence = result['sequence']
+    move_codes = result['move_codes']
+    depth_labelling = result['depth_labelling']
+    g_prime = result['deep_embedding']
+
+    move_names = {0: "AD", 1: "LA", 2: "J", 3: "RC"}
+    quad_type_colors = {
+        "deep_diamond": (178, 223, 219),
+        "shallow_diamond": (255, 224, 178),
+        "s_quad": (248, 187, 208),
+    }
+
+    # Pass 1: collect each quad's level-edge endpoints, apexes, and full vertex set.
+    raw = []
+    quads = sequence[:6]  # Limit to first 6 for readability
+    for i, quad in enumerate(quads):
+        quad_type = _quad_type(quad, depth_labelling)
+        f1, f2 = list(quad)
+        level_edge = _level_edge_of_face(f1, depth_labelling)
+        p, q = list(level_edge)
+        a = next(v for v in f1 if v not in level_edge)
+        b = next(v for v in f2 if v not in level_edge)
+        # Apex with the smaller depth goes on top, larger depth on bottom.
+        top, bottom = (a, b) if depth_labelling[a] <= depth_labelling[b] else (b, a)
+        move = move_names[move_codes[i - 1]] if i > 0 else ""
+        move_label = f"Q_{i+1}" if i == 0 else f"Q_{i+1}^{{{move}}}"
+        raw.append({
+            "level": (p, q),
+            "verts": {p, q, a, b},
+            "top": top,
+            "bottom": bottom,
+            "move": move_label,
+            "type": quad_type,
+            "color": quad_type_colors[quad_type],
+        })
+
+    # Pass 2: chain the diamonds. The left/right corners of a diamond are its level
+    # edge endpoints. A vertex shared with the PREVIOUS quad's level edge was that
+    # quad's right corner, so it goes on the LEFT here; a vertex shared with the NEXT
+    # quad's level edge goes on the RIGHT. Apex vertices are centered (top/bottom) and
+    # impose no left/right constraint, so only level-edge sharing matters.
+    sequence_data = []
+    for i, r in enumerate(raw):
+        p, q = r["level"]
+        prev_level = set(raw[i - 1]["level"]) if i > 0 else set()
+        next_level = set(raw[i + 1]["level"]) if i + 1 < len(raw) else set()
+
+        p_prev, q_prev = p in prev_level, q in prev_level
+        p_next, q_next = p in next_level, q in next_level
+
+        if p_prev != q_prev:            # exactly one shared with prev -> left
+            left = p if p_prev else q
+            right = q if p_prev else p
+        elif p_next != q_next:          # else exactly one shared with next -> right
+            right = p if p_next else q
+            left = q if p_next else p
+        else:                           # no chain constraint: deterministic fallback
+            right = max(p, q, key=str)
+            left = q if right == p else p
+
+        sequence_data.append({
+            "left": left,
+            "right": right,
+            "top": r["top"],
+            "bottom": r["bottom"],
+            "depth_left": depth_labelling[left],
+            "depth_right": depth_labelling[right],
+            "depth_top": depth_labelling[r["top"]],
+            "depth_bottom": depth_labelling[r["bottom"]],
+            "move": r["move"],
+            "type": r["type"],
+            "color": r["color"],
+        })
+
+    return sequence_data, depth_labelling, g, outer_cycle, g_prime
+
+
+def draw_graph(g_prime: Graph, outer_cycle: list, depth_labelling: dict, width: int, height: int) -> Image.Image:
+    """Draw the deep embedding graph with Tutte embedding and depth labels in a square."""
+    img = Image.new('RGB', (width, height), 'white')
+    draw = ImageDraw.Draw(img)
+
+    # Get Tutte embedding for the deep embedding graph
+    pos = tutte_embedding(g_prime, outer_cycle)
+
+    # Get data bounds
+    xs = [p[0] for p in pos.values()]
+    ys = [p[1] for p in pos.values()]
+    x_min, x_max = min(xs), max(xs)
+    y_min, y_max = min(ys), max(ys)
+    x_range = x_max - x_min if x_max > x_min else 1
+    y_range = y_max - y_min if y_max > y_min else 1
+
+    # Create a square region in the center of the image
+    margin = 30
+    max_size = min(width, height) - 2 * margin
+    graph_size = max_size
+
+    # Center the square graph horizontally
+    graph_x_min = (width - graph_size) // 2
+    graph_x_max = graph_x_min + graph_size
+    graph_y_min = margin
+    graph_y_max = margin + graph_size
+
+    def data_to_pixel(x: float, y: float) -> tuple[int, int]:
+        px = graph_x_min + (x - x_min) / x_range * (graph_x_max - graph_x_min)
+        py = graph_y_min + (y - y_min) / y_range * (graph_y_max - graph_y_min)
+        return int(px), int(py)
+
+    # Draw edges
+    for u, v in g_prime.edges(labels=False):
+        px1, py1 = data_to_pixel(pos[u][0], pos[u][1])
+        px2, py2 = data_to_pixel(pos[v][0], pos[v][1])
+        # Color level edges differently
+        if depth_labelling[u] == depth_labelling[v]:
+            draw.line([(px1, py1), (px2, py2)], fill=(150, 150, 150), width=1)
+        else:
+            draw.line([(px1, py1), (px2, py2)], fill=(50, 50, 50), width=1)
+
+    # Draw vertices
+    for v, (x, y) in pos.items():
+        px, py = data_to_pixel(x, y)
+        depth = depth_labelling[v]
+        if v in outer_cycle:
+            color = (25, 118, 210)  # blue
+        else:
+            color = (0, 0, 0)  # black
+        draw.ellipse([px-5, py-5, px+5, py+5], fill=color)
+        # Draw label with vertex ID and depth
+        label = f"{v}^{depth}"
+        draw.text((px-12, py-20), label, fill='black')
+
+    return img
+
+
+def draw_diagram(sequence_data: list[dict], depth_labelling: dict, output_path: str):
+    """Draw and save the sequence diagram."""
+    width = 300 + len(sequence_data) * 400
+    height = 380
+    img = Image.new('RGB', (width, height), 'white')
+    draw = ImageDraw.Draw(img)
+
+    # Data-to-pixel coordinate mapping
+    data_x_min = -2.0
+    data_x_max = 0.5 + len(sequence_data) * 3.5
+    data_y_min = -1.1
+    data_y_max = 2.3
+    pixel_x_min = 80
+    pixel_x_max = width - 40
+    pixel_y_min = 40
+    pixel_y_max = height - 40
+
+    def data_to_pixel(x: float, y: float) -> tuple[int, int]:
+        px = pixel_x_min + (x - data_x_min) / (data_x_max - data_x_min) * (pixel_x_max - pixel_x_min)
+        py = pixel_y_max - (y - data_y_min) / (data_y_max - data_y_min) * (pixel_y_max - pixel_y_min)
+        return int(px), int(py)
+
+    step_width = 3.5
+    r = 0.45
+
+    # Depth -> data-y: smaller depth higher on screen (larger data-y).
+    all_depths = [
+        d for quad in sequence_data
+        for d in (quad["depth_left"], quad["depth_right"], quad["depth_top"], quad["depth_bottom"])
+    ]
+    min_d, max_d = min(all_depths), max(all_depths)
+    y_of = lambda d: 1.0 - (d - min_d) * 0.5
+
+    for i, quad_data in enumerate(sequence_data):
+        x = i * step_width
+        color = quad_data["color"]
+
+        # Place the four corners. The level edge {left,right} is horizontal (both at
+        # the same depth); the apexes sit above (smaller depth) and below (larger).
+        p_left = data_to_pixel(x - r, y_of(quad_data["depth_left"]))
+        p_right = data_to_pixel(x + r, y_of(quad_data["depth_right"]))
+        p_top = data_to_pixel(x, y_of(quad_data["depth_top"]))
+        p_bottom = data_to_pixel(x, y_of(quad_data["depth_bottom"]))
+
+        # Polygon in cyclic order so the diamond is non-self-intersecting.
+        corners = [p_left, p_top, p_right, p_bottom]
+        draw.polygon(corners, fill=color, outline='black', width=2)
+        for px, py in corners:
+            draw.ellipse([px-5, py-5, px+5, py+5], fill='black')
+
+        # Vertex labels, offset away from the diamond body.
+        labels = [
+            (p_left, quad_data["left"], (-18, -6)),
+            (p_right, quad_data["right"], (10, -6)),
+            (p_top, quad_data["top"], (-4, -18)),
+            (p_bottom, quad_data["bottom"], (-4, 8)),
+        ]
+        for (px, py), vid, (dx, dy) in labels:
+            draw.text((px + dx, py + dy), str(vid), fill='black')
+
+        # Quad move label at the centroid.
+        cx = sum(p[0] for p in corners) // 4
+        cy = sum(p[1] for p in corners) // 4
+        draw.text((cx-15, cy-6), quad_data["move"], fill='black')
+
+        # Depth gridline labels on the left of the first quad.
+        if i == 0:
+            for d in range(min_d, max_d + 1):
+                label_px, label_py = data_to_pixel(x - 1.2, y_of(d))
+                draw.text((label_px-28, label_py-6), f"d={d}", fill=(80, 80, 80))
+
+    if output_path:
+        img.save(output_path)
+        print(f"Saved diagram to {output_path}")
+    print(f"Sequence diagram size: {img.size}")
+    return img
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument("--seed", type=int, default=42, help="Random seed for graph generation")
+    parser.add_argument("--n", type=int, default=7, help="Number of vertices in the random triangulation")
+    parser.add_argument("--output", type=str, default="quad_sequence_diagram.png", help="Output file path")
+    args = parser.parse_args()
+
+    print(f"Generating sequence for n={args.n} with seed={args.seed}")
+    sequence_data, depth_labelling, g, outer_cycle, g_prime = generate_sequence(args.seed, args.n)
+    print(f"Generated {len(sequence_data)} quadrilaterals")
+    print(f"Deep embedding has {g_prime.order()} vertices (original had {g.order()})")
+
+    # Draw deep embedding graph with depths
+    graph_width = 300 + len(sequence_data) * 400
+    graph_height = 500
+    graph_img = draw_graph(g_prime, outer_cycle, depth_labelling, graph_width, graph_height)
+
+    # Draw sequence
+    seq_width = graph_width
+    seq_height = 380
+    seq_img = draw_diagram(sequence_data, depth_labelling, None)  # Return image instead of saving
+
+    # Combine images vertically
+    combined_width = graph_width
+    combined_height = graph_height + seq_height + 20  # 20px gap
+    combined_img = Image.new('RGB', (combined_width, combined_height), 'white')
+    combined_img.paste(graph_img, (0, 0))
+    combined_img.paste(seq_img, (0, graph_height + 20))
+
+    combined_img.save(args.output)
+    print(f"Saved diagram to {args.output}")
+    print(f"Combined image size: {combined_img.size}")
diff --git a/papers/plane_depth_sequencing/experiments/draw_quad_sequence_diagram.py b/papers/plane_depth_sequencing/experiments/draw_quad_sequence_diagram.py
new file mode 100644
index 0000000..ddebba5
--- /dev/null
+++ b/papers/plane_depth_sequencing/experiments/draw_quad_sequence_diagram.py
@@ -0,0 +1,146 @@
+"""Draw a labeled quadrilateral sequence diagram for the plane depth sequencing paper."""
+import matplotlib.pyplot as plt
+import matplotlib.patches as patches
+from matplotlib.patches import FancyArrowPatch
+import numpy as np
+
+sequence_data = [
+    {"vertices": [-2, -1, 3, 7], "ordered": [-2, 7, -1, 3], "depths": [0, 1, 0, 1], "move": "Q_1", "type": "deep_diamond"},
+    {"vertices": [-1, 3, 4, 8], "ordered": [3, -1, 4, 8], "depths": [1, 0, 1, 2], "move": "Q_2^{AD}", "type": "s_quad"},
+    {"vertices": [2, 4, 5, 8], "ordered": [4, 2, 5, 8], "depths": [1, 0, 1, 2], "move": "Q_3^{AD}", "type": "s_quad"},
+    {"vertices": [-1, 2, 4, 6], "ordered": [4, 2, 6, -1], "depths": [1, 0, 1, 0], "move": "Q_4^{LA}", "type": "shallow_diamond"},
+]
+
+COLORS = {
+    "deep_diamond": "#B2DFDB",
+    "shallow_diamond": "#FFE0B2",
+    "s_quad": "#F8BBD0",
+}
+
+def draw_sequence_diagram(sequence_data: list[dict], output_path: str = "quad_sequence_diagram.png"):
+    """Draw the full quadrilateral sequence diagram."""
+    fig, ax = plt.subplots(figsize=(16, 5.5))
+
+    step_width = 4.0
+    y_center = 1.0
+    x_positions = [i * step_width for i in range(len(sequence_data))]
+
+    # Store vertex positions for connecting matching vertices
+    quad_vertex_positions = []
+
+    for i, quad_data in enumerate(sequence_data):
+        x = x_positions[i]
+        quad_type = quad_data["type"]
+        ordered_verts = quad_data["ordered"]
+        depths = quad_data["depths"]
+
+        # Standard positions: top, right, bottom, left (or tweezers variant)
+        if quad_type == "s_quad":
+            # Tweezers shape: top, left-pinched-upper, right, left-pinched-lower
+            r = 0.45
+            pinch = 0.25
+            std_positions = [
+                (x, y_center + r),                    # e1: top
+                (x - r + pinch, y_center + r * 0.35),  # a: left-upper
+                (x + r, y_center),                    # e2: right
+                (x - r + pinch, y_center - r * 0.35),  # b: left-lower
+            ]
+        else:
+            # Diamond shape: top, right, bottom, left
+            r = 0.45
+            std_positions = [
+                (x, y_center + r),        # e1: top
+                (x + r, y_center),        # a: right
+                (x, y_center - r),        # e2: bottom
+                (x - r, y_center),        # b: left
+            ]
+
+        # Draw polygon
+        polygon = patches.Polygon(
+            std_positions,
+            closed=True,
+            facecolor=COLORS.get(quad_type, "#CCCCCC"),
+            edgecolor="black",
+            linewidth=1.5,
+            alpha=0.75,
+        )
+        ax.add_patch(polygon)
+
+        # Draw vertices and labels
+        vertex_positions = {}
+        for vert_idx, (vertex_id, (vx, vy), depth) in enumerate(zip(ordered_verts, std_positions, depths)):
+            # Draw vertex point
+            ax.plot(vx, vy, "ko", markersize=7, zorder=5)
+            vertex_positions[vertex_id] = (vx, vy)
+
+            # Draw vertex label below
+            ax.text(vx, vy - 0.2, str(vertex_id), ha="center", va="top", fontsize=8, fontweight="bold",
+                   bbox=dict(boxstyle="round,pad=0.15", facecolor="lightyellow", alpha=0.9, edgecolor="none"))
+
+        # Draw quad label in center
+        center_x = np.mean([p[0] for p in std_positions])
+        center_y = np.mean([p[1] for p in std_positions])
+        ax.text(center_x, center_y, f"${quad_data['move']}$", ha="center", va="center",
+               fontsize=11, fontweight="bold",
+               bbox=dict(boxstyle="round,pad=0.3", facecolor="white", edgecolor="black", alpha=0.85))
+
+        # Draw depth labels on the left (only for first quad)
+        if i == 0:
+            unique_depths = sorted(set(depths))
+            for d in unique_depths:
+                label_y = y_center + 0.5 - d * 0.5
+                ax.text(x - 1.0, label_y, f"d={d}", ha="right", va="center", fontsize=9, style="italic")
+
+        quad_vertex_positions.append(vertex_positions)
+
+        # Draw arrows connecting matching vertices to next quad
+        if i < len(sequence_data) - 1:
+            next_quad_verts = set(sequence_data[i + 1]["vertices"])
+            for vertex_id, (vx, vy) in vertex_positions.items():
+                if vertex_id in next_quad_verts:
+                    next_quad_data = sequence_data[i + 1]
+                    next_x = x_positions[i + 1]
+                    next_idx = next_quad_data["ordered"].index(vertex_id)
+
+                    if next_quad_data["type"] == "s_quad":
+                        r = 0.45
+                        pinch = 0.25
+                        next_std_positions = [
+                            (next_x, y_center + r),
+                            (next_x - r + pinch, y_center + r * 0.35),
+                            (next_x + r, y_center),
+                            (next_x - r + pinch, y_center - r * 0.35),
+                        ]
+                    else:
+                        r = 0.45
+                        next_std_positions = [
+                            (next_x, y_center + r),
+                            (next_x + r, y_center),
+                            (next_x, y_center - r),
+                            (next_x - r, y_center),
+                        ]
+
+                    next_vx, next_vy = next_std_positions[next_idx]
+
+                    # Draw connecting arrow
+                    arrow = FancyArrowPatch(
+                        (vx, vy), (next_vx, next_vy),
+                        arrowstyle="->", color="gray", linewidth=0.8, alpha=0.5, zorder=1,
+                        connectionstyle="arc3,rad=0.15"
+                    )
+                    ax.add_patch(arrow)
+
+    # Set axis properties
+    ax.set_xlim(-1.8, x_positions[-1] + 1.2)
+    ax.set_ylim(-1.0, 2.2)
+    ax.set_aspect("equal")
+    ax.axis("off")
+
+    plt.tight_layout()
+    plt.savefig(output_path, dpi=150, bbox_inches="tight")
+    print(f"Saved diagram to {output_path}")
+    plt.show()
+
+
+if __name__ == "__main__":
+    draw_sequence_diagram(sequence_data, "quad_sequence_diagram.png")
diff --git a/papers/plane_depth_sequencing/experiments/extract_sequence.py b/papers/plane_depth_sequencing/experiments/extract_sequence.py
new file mode 100644
index 0000000..682b4df
--- /dev/null
+++ b/papers/plane_depth_sequencing/experiments/extract_sequence.py
@@ -0,0 +1,39 @@
+"""Extract sequence data for diagram."""
+import os, sys
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))  # sibling experiment modules
+from sage.all import graphs  # type: ignore
+from sage.misc.randstate import set_random_seed  # type: ignore
+from plane_depth_sequencing import (
+    quadrilateral_sequencing,
+    _quad_vertices,
+    _level_edge_of_face,
+    _quad_type
+)
+
+set_random_seed(42)
+g = graphs.RandomTriangulation(7)
+g.is_planar(set_embedding=True)
+embedding = g.get_embedding()
+faces = g.faces(embedding)
+outer_cycle = [u for u, _ in faces[0]]
+
+result = quadrilateral_sequencing(g, outer_cycle)
+sequence = result['sequence']
+move_codes = result['move_codes']
+depth_labelling = result['depth_labelling']
+
+move_names = {0: "AD", 1: "LA", 2: "J", 3: "RC"}
+
+print("sequence_data = [")
+for i, quad in enumerate(sequence[:4]):
+    quad_type = _quad_type(quad, depth_labelling)
+    f1, f2 = list(quad)
+    level_edge = _level_edge_of_face(f1, depth_labelling)
+    e1, e2 = list(level_edge)
+    a = next(v for v in f1 if v not in level_edge)
+    b = next(v for v in f2 if v not in level_edge)
+    ordered_verts = [e1, a, e2, b]
+    move = move_names[move_codes[i-1]] if i > 0 else ""
+    depths_str = [depth_labelling[v] for v in ordered_verts]
+    print(f'    {{"vertices": {sorted(_quad_vertices(quad))}, "ordered": {ordered_verts}, "depths": {depths_str}, "move": "Q_{i+1}^{{{move}}}", "type": "{quad_type}"}},')
+print("]")
diff --git a/papers/plane_depth_sequencing/experiments/plane_depth_sequencing.py b/papers/plane_depth_sequencing/experiments/plane_depth_sequencing.py
index 3b7c53f..bd3327c 100644
--- a/papers/plane_depth_sequencing/experiments/plane_depth_sequencing.py
+++ b/papers/plane_depth_sequencing/experiments/plane_depth_sequencing.py
@@ -1,4 +1,6 @@
 """Plane depth sequencing on maximal planar graphs."""
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
 import random
 from typing import Any, TypedDict
 from sage.all import Graph, graphs  # type: ignore[attr-defined]  # pylint: disable=no-name-in-module
@@ -160,9 +162,11 @@ def extended_deep_embedding(
             next_vertex += 1
             g_prime.add_vertex(x)
             g_prime.add_edges([(x, a), (x, b), (x, c)])
-            depth_labelling[x] = depth_labelling[a] + 1
             if frozenset(face_vertices) == outer_vertices:
                 outer_cap_vertex = x
+                depth_labelling[x] = -1  # Outer-cap vertex has depth -1
+            else:
+                depth_labelling[x] = depth_labelling[a] + 1
 
     g_prime.is_planar(set_embedding=True)
     embedding = g_prime.get_embedding()
diff --git a/papers/plane_depth_sequencing/experiments/plane_depth_sequencing_figure.py b/papers/plane_depth_sequencing/experiments/plane_depth_sequencing_figure.py
index 9920c87..7c3557a 100644
--- a/papers/plane_depth_sequencing/experiments/plane_depth_sequencing_figure.py
+++ b/papers/plane_depth_sequencing/experiments/plane_depth_sequencing_figure.py
@@ -5,6 +5,9 @@ quadrilateral with a color encoding its type, and overlays the index it
 occupies in the canonical sequence Q_1, ..., Q_N. The output is a PDF placed
 next to paper.tex.
 """
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))  # sibling experiment modules
 import argparse
 from pathlib import Path
 from typing import Any
diff --git a/papers/plane_depth_sequencing/experiments/quad_sequence_coloring_check.py b/papers/plane_depth_sequencing/experiments/quad_sequence_coloring_check.py
index 36ba4df..ab72d54 100644
--- a/papers/plane_depth_sequencing/experiments/quad_sequence_coloring_check.py
+++ b/papers/plane_depth_sequencing/experiments/quad_sequence_coloring_check.py
@@ -16,6 +16,9 @@ failure as one of:
   - 'ring_completion_monochromatic': a ring completion's quad has a monochromatic edge
   - 'success': global proper 4-coloring of G'.
 """
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
+sys.path.insert(0, os.path.dirname(os.path.abspath(__file__)))  # sibling experiment modules
 from typing import Any
 from sage.all import Graph, graphs  # type: ignore[attr-defined]  # pylint: disable=no-name-in-module
 from lib.colored_graphs import canonize_and_save_graph
diff --git a/papers/plane_diamond_coloring/experiments/plane_diamond_coloring.py b/papers/plane_diamond_coloring/experiments/plane_diamond_coloring.py
index b7dd374..944149d 100644
--- a/papers/plane_diamond_coloring/experiments/plane_diamond_coloring.py
+++ b/papers/plane_diamond_coloring/experiments/plane_diamond_coloring.py
@@ -1,4 +1,6 @@
 """Plane diamond coloring on maximal planar graphs."""
+import os, sys
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), "..", "..", "..")))  # repo root for `lib`
 from typing import Any
 from sage.all import Graph, graphs  # type: ignore[attr-defined]  # pylint: disable=no-name-in-module
 from lib.colored_graphs import canonize_and_save_graph