feat(core): introduce decoupled ContextManager and Sidecar architecture (#24752)

packages/core/src/context/graph/fromGraph.ts

@@ -0,0 +1,54 @@
+/**
+ * @license
+ * Copyright 2026 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+import type { Content, Part } from '@google/genai';
+import type { ConcreteNode } from './types.js';
+import type {
+  NodeSerializationWriter,
+  NodeBehaviorRegistry,
+} from './behaviorRegistry.js';
+
+class NodeSerializer implements NodeSerializationWriter {
+  private history: Content[] = [];
+  private currentModelParts: Part[] = [];
+
+  appendContent(content: Content) {
+    this.flushModelParts();
+    this.history.push(content);
+  }
+
+  appendModelPart(part: Part) {
+    this.currentModelParts.push(part);
+  }
+
+  appendUserPart(part: Part) {
+    this.flushModelParts();
+    this.history.push({ role: 'user', parts: [part] });
+  }
+
+  flushModelParts() {
+    if (this.currentModelParts.length > 0) {
+      this.history.push({ role: 'model', parts: [...this.currentModelParts] });
+      this.currentModelParts = [];
+    }
+  }
+
+  getContents(): Content[] {
+    this.flushModelParts();
+    return this.history;
+  }
+}
+
+export function fromGraph(
+  nodes: readonly ConcreteNode[],
+  registry: NodeBehaviorRegistry,
+): Content[] {
+  const writer = new NodeSerializer();
+  for (const node of nodes) {
+    const behavior = registry.get(node.type);
+    behavior.serialize(node, writer);
+  }
+  return writer.getContents();
+}