feat: add createSequentialChainEdges function to add back agent chaining via multi-agents

packages/api/src/agents/chain.ts

@@ -0,0 +1,46 @@
+import { PromptTemplate } from '@langchain/core/prompts';
+import { BaseMessage, getBufferString } from '@langchain/core/messages';
+import type { GraphEdge } from '@librechat/agents';
+
+const DEFAULT_PROMPT_TEMPLATE = `Based on the following conversation and analysis from previous agents, please provide your insights:\n\n{convo}\n\nPlease add your specific expertise and perspective to this discussion.`;
+
+/**
+ * Helper function to create sequential chain edges with buffer string prompts
+ *
+ * @param agentIds - Array of agent IDs in order of execution
+ * @param promptTemplate - Optional prompt template string; defaults to a predefined template if not provided
+ * @returns Array of edges configured for sequential chain with buffer prompts
+ */
+export async function createSequentialChainEdges(
+  agentIds: string[],
+  promptTemplate = DEFAULT_PROMPT_TEMPLATE,
+): Promise<GraphEdge[]> {
+  const edges: GraphEdge[] = [];
+
+  for (let i = 0; i < agentIds.length - 1; i++) {
+    const fromAgent = agentIds[i];
+    const toAgent = agentIds[i + 1];
+
+    edges.push({
+      from: fromAgent,
+      to: toAgent,
+      edgeType: 'direct',
+      // Use a prompt function to create the buffer string from all previous results
+      prompt: async (messages: BaseMessage[], startIndex: number) => {
+        /** Only the messages from this run (after startIndex) are passed in */
+        const runMessages = messages.slice(startIndex);
+        const bufferString = getBufferString(runMessages);
+        const template = PromptTemplate.fromTemplate(promptTemplate);
+        const result = await template.invoke({
+          convo: bufferString,
+        });
+        return result.value;
+      },
+      /** Critical: exclude previous results so only the prompt is passed */
+      excludeResults: true,
+      description: `Sequential chain from ${fromAgent} to ${toAgent}`,
+    });
+  }
+
+  return edges;
+}

packages/api/src/agents/index.ts

@@ -1,3 +1,4 @@
+export * from './chain';
 export * from './config';
 export * from './memory';
 export * from './migration';