diff --git a/packages/breadboard/src/board.ts b/packages/breadboard/src/board.ts
new file mode 100644
index 00000000000..ca7056f77ec
--- /dev/null
+++ b/packages/breadboard/src/board.ts
@@ -0,0 +1,40 @@
+import type { GraphDescriptor, Edge, NodeDescriptor } from "./types.js";
+
+export class Board {
+  private edges: Edge[] = [];
+  private nodes: NodeDescriptor[] = [];
+
+  serialize(): GraphDescriptor {
+    return {
+      edges: this.edges.map((edge) => {
+        const serialized: Edge = {
+          from: edge.from,
+          to: edge.to,
+        };
+        if (edge.out !== undefined) serialized.out = edge.out;
+        if (edge.in !== undefined) serialized.in = edge.in;
+        if (edge.required !== undefined) serialized.required = edge.required;
+        return serialized;
+      }),
+      nodes: this.nodes,
+    };
+  }
+
+  static deserialize(descriptor: GraphDescriptor): Board {
+    const board = new Board();
+    board.nodes = descriptor.nodes || [];
+    
+    for (const edge of descriptor.edges || []) {
+      const newEdge: Edge = {
+        from: edge.from,
+        to: edge.to,
+      };
+      if (edge.out !== undefined) newEdge.out = edge.out;
+      if (edge.in !== undefined) newEdge.in = edge.in;
+      if (edge.required !== undefined) newEdge.required = edge.required;
+      board.edges.push(newEdge);
+    }
+    
+    return board;
+  }
+}
\ No newline at end of file
diff --git a/packages/breadboard/src/node.ts b/packages/breadboard/src/node.ts
new file mode 100644
index 00000000000..21ed9098c3f
--- /dev/null
+++ b/packages/breadboard/src/node.ts
@@ -0,0 +1,35 @@
+export interface WireOptions {
+  required?: boolean;
+}
+
+export class Wire {
+  source: Node;
+  target: Node;
+  required: boolean;
+
+  constructor(source: Node, target: Node, required: boolean = false) {
+    this.source = source;
+    this.target = target;
+    this.required = required;
+  }
+}
+
+export class Node {
+  id: string;
+  outgoing: Wire[] = [];
+
+  constructor(id: string) {
+    this.id = id;
+    this.outgoing = [];
+  }
+
+  to(target: Node, options?: WireOptions): Wire {
+    const wire = new Wire(this, target, options?.required);
+    this.outgoing.push(wire);
+    return wire;
+  }
+
+  requiredTo(target: Node): Wire {
+    return this.to(target, { required: true });
+  }
+}
\ No newline at end of file
diff --git a/packages/breadboard/src/runtime/traversal.ts b/packages/breadboard/src/runtime/traversal.ts
new file mode 100644
index 00000000000..8f78b269154
--- /dev/null
+++ b/packages/breadboard/src/runtime/traversal.ts
@@ -0,0 +1,74 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import type { Edge, NodeIdentifier, InputValues } from "../types.js";
+
+interface TraversalEdge {
+  from: NodeIdentifier;
+  to: NodeIdentifier;
+  out: string;
+  in: string;
+  required?: boolean;
+}
+
+interface NodeState {
+  inputs: InputValues;
+  receivedEdges: Set<string>;
+}
+
+export class Traversal {
+  private incomingEdges: Map<NodeIdentifier, TraversalEdge[]> = new Map();
+  private nodeStates: Map<NodeIdentifier, NodeState> = new Map();
+  
+  constructor(edges: Edge[]) {
+    for (const edge of edges) {
+      const edgesForNode = this.incomingEdges.get(edge.to) || [];
+      edgesForNode.push(edge as TraversalEdge);
+      this.incomingEdges.set(edge.to, edgesForNode);
+    }
+  }
+  
+  /**
+   * Check if a node is ready to execute.
+   * A node is ready only when all required incoming edges have provided data.
+   */
+  isNodeReady(nodeId: NodeIdentifier): boolean {
+    const edges = this.incomingEdges.get(nodeId) || [];
+    const state = this.nodeStates.get(nodeId);
+    
+    for (const edge of edges) {
+      if (edge.required) {
+        const edgeKey = `${edge.from}:${edge.out}`;
+        if (!state?.receivedEdges.has(edgeKey)) {
+          return false;
+        }
+      }
+    }
+    
+    return true;
+  }
+  
+  /**
+   * Receive data from an edge.
+   */
+  receiveEdgeData(nodeId: NodeIdentifier, from: NodeIdentifier, out: string, data: unknown): void {
+    let state = this.nodeStates.get(nodeId);
+    if (!state) {
+      state = { inputs: {}, receivedEdges: new Set() };
+      this.nodeStates.set(nodeId, state);
+    }
+    
+    state.receivedEdges.add(`${from}:${out}`);
+    
+    if (data !== undefined && typeof data === "object") {
+      Object.assign(state.inputs, data);
+    }
+  }
+  
+  getNodeInputs(nodeId: NodeIdentifier): InputValues {
+    return this.nodeStates.get(nodeId)?.inputs || {};
+  }
+}
\ No newline at end of file
diff --git a/packages/breadboard/src/types.ts b/packages/breadboard/src/types.ts
new file mode 100644
index 00000000000..39d7528f80a
--- /dev/null
+++ b/packages/breadboard/src/types.ts
@@ -0,0 +1,26 @@
+/**
+ * @license
+ * Copyright 2024 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+export type NodeIdentifier = string;
+
+/**
+ * Represents an edge (wire) connecting two nodes in the graph.
+ */
+export interface Edge {
+  from: NodeIdentifier;
+  to: NodeIdentifier;
+  out?: string;
+  in?: string;
+  required?: boolean;
+}
+
+/**
+ * Proxy interface for building node connections in a fluent API style.
+ */
+export interface NodeProxy {
+  to(target: NodeIdentifier): void;
+  requiredTo(target: NodeIdentifier): void;
+}
\ No newline at end of file