fix: content node refs field + thread head update

Fixes #161

Fixes #162

Co-authored-by: Cursor <cursoragent@cursor.com>

packages/workflow-cas/src/merkle.ts

@@ -1,8 +1,41 @@
 import { parse, stringify } from "yaml";
 
-import type { CasStore, MerkleNode, StepMerklePayload, ThreadMerklePayload } from "./types.js";
+import type {
+  CasStore,
+  MerkleNode,
+  MerkleNodeType,
+  StepMerklePayload,
+  ThreadMerklePayload,
+} from "./types.js";
+
+function requireStringHashArray(value: unknown, notArrayMessage: string): string[] {
+  if (!Array.isArray(value)) {
+    throw new Error(notArrayMessage);
+  }
+  const out: string[] = [];
+  for (const c of value) {
+    if (typeof c !== "string") {
+      throw new Error("merkle: hash entry must be a string");
+    }
+    out.push(c);
+  }
+  return out;
+}
+
+function edgeListRaw(rec: Record<string, unknown>, type: MerkleNodeType): unknown {
+  if (type === "content") {
+    return rec.refs !== undefined ? rec.refs : rec.children;
+  }
+  return rec.children;
+}
 
 export function serializeMerkleNode(node: MerkleNode): string {
+  if (node.type === "content") {
+    return stringify(
+      { type: node.type, payload: node.payload, refs: node.children },
+      { indent: 2 },
+    );
+  }
   return stringify(
     { type: node.type, payload: node.payload, children: node.children },
     { indent: 2 },
@@ -17,23 +50,18 @@ export function parseMerkleNode(yamlText: string): MerkleNode {
   const rec = raw as Record<string, unknown>;
   const type = rec.type;
   const payload = rec.payload;
-  const children = rec.children;
   if (type !== "content" && type !== "step" && type !== "thread") {
     throw new Error("merkle: invalid or missing type");
   }
   if (typeof payload !== "string" && (payload === null || typeof payload !== "object")) {
     throw new Error("merkle: payload must be a string or object");
   }
-  if (!Array.isArray(children)) {
-    throw new Error("merkle: children must be an array");
-  }
-  const childHashes: string[] = [];
-  for (const c of children) {
-    if (typeof c !== "string") {
-      throw new Error("merkle: child hash must be a string");
-    }
-    childHashes.push(c);
-  }
+
+  const notArrayMsg =
+    type === "content"
+      ? "merkle: content node requires refs or children array"
+      : "merkle: children must be an array";
+  const childHashes = requireStringHashArray(edgeListRaw(rec, type), notArrayMsg);
   return {
     type,
     payload: typeof payload === "string" ? payload : (payload as Record<string, unknown>),
@@ -85,8 +113,8 @@ export async function putContentMerkleNode(store: CasStore, content: string): Pr
 /**
  * Loads a CAS blob and returns the payload string for a `content` node.
  *
- * Accepts both the legacy `{type:content, payload, children}` Merkle layout
- * and the RFC v3 `{type:content, payload, refs}` content node layout.
+ * Accepts both the legacy `{ type:content, payload, children }` Merkle layout
+ * and the RFC-aligned `{ type:content, payload, refs }` content node layout.
  */
 export async function getContentMerklePayload(
   store: CasStore,

packages/workflow-cas/src/reachable.ts

@@ -9,7 +9,10 @@ function refsFromBlob(content: string): string[] {
       return [];
     }
     const rec = raw as Record<string, unknown>;
-    const refs = rec.refs;
+    let refs = rec.refs;
+    if (!Array.isArray(refs) && Array.isArray(rec.children)) {
+      refs = rec.children;
+    }
     if (!Array.isArray(refs)) {
       return [];
     }

packages/workflow-execute/src/extract/extract-fn.ts

@@ -20,7 +20,7 @@ const CAS_GET_TOOL_DEFINITION = {
   function: {
     name: "cas_get",
     description:
-      "Read a Merkle DAG node from content-addressed storage by its hash. Returns YAML-formatted node with type, payload, and children fields.",
+      "Read a Merkle DAG node from content-addressed storage by its hash. Returns YAML-formatted node with type, payload, and refs or children fields (content nodes use refs).",
     parameters: {
       type: "object",
       properties: {
@@ -102,7 +102,7 @@ export function createExtract(provider: LlmProvider, deps: ExtractDeps): Extract
       };
     },
     systemPromptForStructuredTool: (structuredToolName) =>
-      `You extract structured metadata from the agent output below. Use cas_get to read Merkle DAG nodes from CAS (YAML: type, payload, children) when the agent output references hashes you must traverse. When you have the complete structured object, call the ${structuredToolName} tool with JSON arguments matching the schema. You may instead reply with only a JSON object (no prose) when no tools are needed.`,
+      `You extract structured metadata from the agent output below. Use cas_get to read Merkle DAG nodes from CAS (YAML: type, payload, refs for content nodes or children for step/thread legacy nodes) when the agent output references hashes you must traverse. When you have the complete structured object, call the ${structuredToolName} tool with JSON arguments matching the schema. You may instead reply with only a JSON object (no prose) when no tools are needed.`,
     toolHandler: async (call, thread) => {
       if (call.function.name !== "cas_get") {
         return `Unexpected tool routed to handler: ${call.function.name}`;