diff --git a/solver/datagen/__init__.py b/solver/datagen/__init__.py
index e69de29..6e53b70 100644
--- a/solver/datagen/__init__.py
+++ b/solver/datagen/__init__.py
@@ -0,0 +1,17 @@
+"""Data generation utilities for assembly constraint training data."""
+
+from solver.datagen.types import (
+    ConstraintAnalysis,
+    Joint,
+    JointType,
+    PebbleState,
+    RigidBody,
+)
+
+__all__ = [
+    "ConstraintAnalysis",
+    "Joint",
+    "JointType",
+    "PebbleState",
+    "RigidBody",
+]
diff --git a/solver/datagen/types.py b/solver/datagen/types.py
new file mode 100644
index 0000000..754e5dc
--- /dev/null
+++ b/solver/datagen/types.py
@@ -0,0 +1,137 @@
+"""Shared data types for assembly constraint analysis.
+
+Types ported from the pebble-game synthetic data generator for reuse
+across the solver package (data generation, training, inference).
+"""
+
+from __future__ import annotations
+
+import enum
+from dataclasses import dataclass, field
+from typing import TYPE_CHECKING
+
+import numpy as np
+
+if TYPE_CHECKING:
+    from typing import Any
+
+__all__ = [
+    "ConstraintAnalysis",
+    "Joint",
+    "JointType",
+    "PebbleState",
+    "RigidBody",
+]
+
+
+# ---------------------------------------------------------------------------
+# Joint definitions: each joint type removes a known number of DOF
+# ---------------------------------------------------------------------------
+
+
+class JointType(enum.Enum):
+    """Standard CAD joint types with their DOF-removal counts.
+
+    Each joint between two 6-DOF rigid bodies removes a specific number
+    of relative degrees of freedom. In the body-bar-hinge multigraph
+    representation, each joint maps to a number of edges equal to the
+    DOF it removes.
+
+    DOF removed = number of scalar constraint equations the joint imposes.
+    """
+
+    FIXED = 6  # Locks all relative motion
+    REVOLUTE = 5  # Allows rotation about one axis
+    CYLINDRICAL = 4  # Allows rotation + translation along one axis
+    SLIDER = 5  # Allows translation along one axis (prismatic)
+    BALL = 3  # Allows rotation about a point (spherical)
+    PLANAR = 3  # Allows 2D translation + rotation normal to plane
+    SCREW = 5  # Coupled rotation-translation (helical)
+    UNIVERSAL = 4  # Two rotational DOF (Cardan/U-joint)
+    PARALLEL = 3  # Forces parallel orientation (3 rotation constraints)
+    PERPENDICULAR = 1  # Single angular constraint
+    DISTANCE = 1  # Single scalar distance constraint
+
+
+# ---------------------------------------------------------------------------
+# Data structures
+# ---------------------------------------------------------------------------
+
+
+@dataclass
+class RigidBody:
+    """A rigid body in the assembly with pose and geometry info."""
+
+    body_id: int
+    position: np.ndarray = field(default_factory=lambda: np.zeros(3))
+    orientation: np.ndarray = field(default_factory=lambda: np.eye(3))
+
+    # Anchor points for joints, in local frame
+    # Populated when joints reference specific geometry
+    local_anchors: dict[str, np.ndarray] = field(default_factory=dict)
+
+
+@dataclass
+class Joint:
+    """A joint connecting two rigid bodies."""
+
+    joint_id: int
+    body_a: int  # Index of first body
+    body_b: int  # Index of second body
+    joint_type: JointType
+
+    # Joint parameters in world frame
+    anchor_a: np.ndarray = field(default_factory=lambda: np.zeros(3))
+    anchor_b: np.ndarray = field(default_factory=lambda: np.zeros(3))
+    axis: np.ndarray = field(
+        default_factory=lambda: np.array([0.0, 0.0, 1.0]),
+    )
+
+    # For screw joints
+    pitch: float = 0.0
+
+
+@dataclass
+class PebbleState:
+    """Tracks the state of the pebble game on the multigraph."""
+
+    # Number of free pebbles per body (vertex). Starts at 6.
+    free_pebbles: dict[int, int] = field(default_factory=dict)
+
+    # Directed edges: edge_id -> (source_body, target_body)
+    # Edge is directed away from the body that "spent" a pebble.
+    directed_edges: dict[int, tuple[int, int]] = field(default_factory=dict)
+
+    # Track which edges are independent vs redundant
+    independent_edges: set[int] = field(default_factory=set)
+    redundant_edges: set[int] = field(default_factory=set)
+
+    # Adjacency: body_id -> set of (edge_id, neighbor_body_id)
+    # Following directed edges *towards* a body (incoming edges)
+    incoming: dict[int, set[tuple[int, int]]] = field(default_factory=dict)
+
+    # Outgoing edges from a body
+    outgoing: dict[int, set[tuple[int, int]]] = field(default_factory=dict)
+
+
+@dataclass
+class ConstraintAnalysis:
+    """Results of analyzing an assembly's constraint system."""
+
+    # Pebble game (combinatorial) results
+    combinatorial_dof: int
+    combinatorial_internal_dof: int
+    combinatorial_redundant: int
+    combinatorial_classification: str
+    per_edge_results: list[dict[str, Any]]
+
+    # Numerical (Jacobian) results
+    jacobian_rank: int
+    jacobian_nullity: int  # = 6n - rank = total DOF
+    jacobian_internal_dof: int  # = nullity - 6
+    numerically_dependent: list[int]
+
+    # Combined
+    geometric_degeneracies: int  # = combinatorial_independent - jacobian_rank
+    is_rigid: bool
+    is_minimally_rigid: bool