From 6235ad21fe2ee86d755627863668d57c8e761eba Mon Sep 17 00:00:00 2001
From: Danny Avila <danny@librechat.ai>
Date: Thu, 4 Sep 2025 21:25:13 -0400
Subject: [PATCH] feat: add `createSequentialChainEdges` function to add back
 agent chaining via multi-agents

---
 .../services/Endpoints/agents/initialize.js   | 32 +++++++++----
 packages/api/src/agents/chain.ts              | 46 +++++++++++++++++++
 packages/api/src/agents/index.ts              |  1 +
 3 files changed, 69 insertions(+), 10 deletions(-)
 create mode 100644 packages/api/src/agents/chain.ts

diff --git a/api/server/services/Endpoints/agents/initialize.js b/api/server/services/Endpoints/agents/initialize.js
index e0ee5b862b..503bf8f117 100644
--- a/api/server/services/Endpoints/agents/initialize.js
+++ b/api/server/services/Endpoints/agents/initialize.js
@@ -1,6 +1,10 @@
 const { logger } = require('@librechat/data-schemas');
 const { createContentAggregator } = require('@librechat/agents');
-const { validateAgentModel, getCustomEndpointConfig } = require('@librechat/api');
+const {
+  validateAgentModel,
+  getCustomEndpointConfig,
+  createSequentialChainEdges,
+} = require('@librechat/api');
 const {
   Constants,
   EModelEndpoint,
@@ -156,15 +160,9 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
     agentConfigs.set(agentId, config);
   }
 
-  if (agent_ids?.length) {
-    for (const agentId of agent_ids) {
-      await processAgent(agentId);
-    }
-  }
-
-  if ((primaryConfig.edges?.length ?? 0) > 0) {
-    const edges = primaryConfig.edges;
-    const checkAgentInit = (agentId) => agentId === primaryConfig.id || agentConfigs.has(agentId);
+  let edges = primaryConfig.edges;
+  const checkAgentInit = (agentId) => agentId === primaryConfig.id || agentConfigs.has(agentId);
+  if ((edges?.length ?? 0) > 0) {
     for (const edge of edges) {
       if (Array.isArray(edge.to)) {
         for (const to of edge.to) {
@@ -194,6 +192,20 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
     }
   }
 
+  if (agent_ids?.length) {
+    for (const agentId of agent_ids) {
+      if (checkAgentInit(agentId)) {
+        continue;
+      }
+      await processAgent(agentId);
+    }
+
+    const chain = await createSequentialChainEdges([primaryConfig.id].concat(agent_ids));
+    edges = edges ? edges.concat(chain) : chain;
+  }
+
+  primaryConfig.edges = edges;
+
   let endpointConfig = appConfig.endpoints?.[primaryConfig.endpoint];
   if (!isAgentsEndpoint(primaryConfig.endpoint) && !endpointConfig) {
     try {
diff --git a/packages/api/src/agents/chain.ts b/packages/api/src/agents/chain.ts
new file mode 100644
index 0000000000..fe8377ade8
--- /dev/null
+++ b/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;
+}
diff --git a/packages/api/src/agents/index.ts b/packages/api/src/agents/index.ts
index 7cb6ce50b2..938573acb0 100644
--- a/packages/api/src/agents/index.ts
+++ b/packages/api/src/agents/index.ts
@@ -1,3 +1,4 @@
+export * from './chain';
 export * from './config';
 export * from './memory';
 export * from './migration';