🫱🏼‍🫲🏽 refactor: Improve Agent Handoffs (#11172)

* fix: Tool Resources Dropped between Agent Handoffs

* fix: agent deletion process to remove handoff edges

- Added logic to the `deleteAgent` function to remove references to the deleted agent from other agents' handoff edges.
- Implemented error handling to log any issues encountered during the edge removal process.
- Introduced a new test case to verify that handoff edges are correctly removed when an agent is deleted, ensuring data integrity across agent relationships.

* fix: Improve agent loading process by handling orphaned references

- Added logic to track and log agents that fail to load during initialization, preventing errors from interrupting the process.
- Introduced a Set to store skipped agent IDs and updated edge filtering to exclude these orphaned references, enhancing data integrity in agent relationships.

* chore: Update @librechat/agents to version 3.0.62

* feat: Enhance agent initialization with edge collection and filtering

- Introduced new functions for edge collection and filtering orphaned edges, improving the agent loading process.
- Refactored the `initializeClient` function to utilize breadth-first search (BFS) for discovering connected agents, enabling transitive handoffs.
- Added a new module for edge-related utilities, including deduplication and participant extraction, to streamline edge management.
- Updated the agent configuration handling to ensure proper edge processing and integrity during initialization.

* refactor: primary agent ID selection for multi-agent conversations

- Added a new function `findPrimaryAgentId` to determine the primary agent ID from a set of agent IDs based on suffix rules.
- Updated `createMultiAgentMapper` to filter messages by primary agent for parallel agents and handle handoffs appropriately.
- Enhanced message processing logic to ensure correct inclusion of agent content based on group and agent ID presence.
- Improved documentation to clarify the distinctions between parallel execution and handoff scenarios.

* feat: Implement primary agent ID selection for multi-agent content filtering

* chore: Update @librechat/agents to version 3.0.63 in package.json and package-lock.json

* chore: Update @librechat/agents to version 3.0.64 in package.json and package-lock.json

* chore: Update @librechat/agents to version 3.0.65 in package.json and package-lock.json

* feat: Add optional agent name to run creation for improved identification

* chore: Update @librechat/agents to version 3.0.66 in package.json and package-lock.json

* test: Add unit tests for edge utilities including key generation, participant extraction, and orphaned edge filtering

- Implemented tests for `getEdgeKey`, `getEdgeParticipants`, `filterOrphanedEdges`, and `createEdgeCollector` functions.
- Ensured comprehensive coverage for various edge cases, including handling of arrays and default values.
- Verified correct behavior of edge filtering based on skipped agents and deduplication of edges.

api/server/controllers/agents/client.js

@@ -98,12 +98,42 @@ function logToolError(graph, error, toolId) {
 /** Regex pattern to match agent ID suffix (____N) */
 const AGENT_SUFFIX_PATTERN = /____(\d+)$/;
 
+/**
+ * Finds the primary agent ID within a set of agent IDs.
+ * Primary = no suffix (____N) or lowest suffix number.
+ * @param {Set<string>} agentIds
+ * @returns {string | null}
+ */
+function findPrimaryAgentId(agentIds) {
+  let primaryAgentId = null;
+  let lowestSuffixIndex = Infinity;
+
+  for (const agentId of agentIds) {
+    const suffixMatch = agentId.match(AGENT_SUFFIX_PATTERN);
+    if (!suffixMatch) {
+      return agentId;
+    }
+    const suffixIndex = parseInt(suffixMatch[1], 10);
+    if (suffixIndex < lowestSuffixIndex) {
+      lowestSuffixIndex = suffixIndex;
+      primaryAgentId = agentId;
+    }
+  }
+
+  return primaryAgentId;
+}
+
 /**
  * Creates a mapMethod for getMessagesForConversation that processes agent content.
  * - Strips agentId/groupId metadata from all content
- * - For multi-agent: filters to primary agent content only (no suffix or lowest suffix)
+ * - For parallel agents (addedConvo with groupId): filters each group to its primary agent
+ * - For handoffs (agentId without groupId): keeps all content from all agents
  * - For multi-agent: applies agent labels to content
  *
+ * The key distinction:
+ * - Parallel execution (addedConvo): Parts have both agentId AND groupId
+ * - Handoffs: Parts only have agentId, no groupId
+ *
  * @param {Agent} primaryAgent - Primary agent configuration
  * @param {Map<string, Agent>} [agentConfigs] - Additional agent configurations
  * @returns {(message: TMessage) => TMessage} Map method for processing messages
@@ -127,40 +157,38 @@ function createMultiAgentMapper(primaryAgent, agentConfigs) {
       return message;
     }
 
-    // Find primary agent ID (no suffix, or lowest suffix number) - only needed for multi-agent
-    let primaryAgentId = null;
-    let hasAgentMetadata = false;
-
-    if (hasMultipleAgents) {
-      let lowestSuffixIndex = Infinity;
-      for (const part of message.content) {
-        const agentId = part?.agentId;
-        if (!agentId) {
-          continue;
-        }
-        hasAgentMetadata = true;
-
-        const suffixMatch = agentId.match(AGENT_SUFFIX_PATTERN);
-        if (!suffixMatch) {
-          primaryAgentId = agentId;
-          break;
-        }
-        const suffixIndex = parseInt(suffixMatch[1], 10);
-        if (suffixIndex < lowestSuffixIndex) {
-          lowestSuffixIndex = suffixIndex;
-          primaryAgentId = agentId;
-        }
-      }
-    } else {
-      // Single agent: just check if any metadata exists
-      hasAgentMetadata = message.content.some((part) => part?.agentId || part?.groupId);
-    }
-
+    // Check for metadata
+    const hasAgentMetadata = message.content.some((part) => part?.agentId || part?.groupId != null);
     if (!hasAgentMetadata) {
       return message;
     }
 
     try {
+      // Build a map of groupId -> Set of agentIds, to find primary per group
+      /** @type {Map<number, Set<string>>} */
+      const groupAgentMap = new Map();
+
+      for (const part of message.content) {
+        const groupId = part?.groupId;
+        const agentId = part?.agentId;
+        if (groupId != null && agentId) {
+          if (!groupAgentMap.has(groupId)) {
+            groupAgentMap.set(groupId, new Set());
+          }
+          groupAgentMap.get(groupId).add(agentId);
+        }
+      }
+
+      // For each group, find the primary agent
+      /** @type {Map<number, string>} */
+      const groupPrimaryMap = new Map();
+      for (const [groupId, agentIds] of groupAgentMap) {
+        const primary = findPrimaryAgentId(agentIds);
+        if (primary) {
+          groupPrimaryMap.set(groupId, primary);
+        }
+      }
+
       /** @type {Array<TMessageContentParts>} */
       const filteredContent = [];
       /** @type {Record<number, string>} */
@@ -168,8 +196,16 @@ function createMultiAgentMapper(primaryAgent, agentConfigs) {
 
       for (const part of message.content) {
         const agentId = part?.agentId;
-        // For single agent: include all parts; for multi-agent: filter to primary
-        if (!hasMultipleAgents || !agentId || agentId === primaryAgentId) {
+        const groupId = part?.groupId;
+
+        // Filtering logic:
+        // - No groupId (handoffs): always include
+        // - Has groupId (parallel): only include if it's the primary for that group
+        const isParallelPart = groupId != null;
+        const groupPrimary = isParallelPart ? groupPrimaryMap.get(groupId) : null;
+        const shouldInclude = !isParallelPart || !agentId || agentId === groupPrimary;
+
+        if (shouldInclude) {
           const newIndex = filteredContent.length;
           const { agentId: _a, groupId: _g, ...cleanPart } = part;
           filteredContent.push(cleanPart);
@@ -325,11 +361,14 @@ class AgentClient extends BaseClient {
     { instructions = null, additional_instructions = null },
     opts,
   ) {
+    const hasAddedConvo = this.options.req?.body?.addedConvo != null;
     const orderedMessages = this.constructor.getMessagesForConversation({
       messages,
       parentMessageId,
       summary: this.shouldSummarize,
-      mapMethod: createMultiAgentMapper(this.options.agent, this.agentConfigs),
+      mapMethod: hasAddedConvo
+        ? createMultiAgentMapper(this.options.agent, this.agentConfigs)
+        : undefined,
     });
 
     let payload;

api/server/services/Endpoints/agents/initialize.js

@@ -5,6 +5,8 @@ const {
   validateAgentModel,
   getCustomEndpointConfig,
   createSequentialChainEdges,
+  createEdgeCollector,
+  filterOrphanedEdges,
 } = require('@librechat/api');
 const {
   EModelEndpoint,
@@ -143,10 +145,17 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
   const agent_ids = primaryConfig.agent_ids;
   let userMCPAuthMap = primaryConfig.userMCPAuthMap;
 
+  /** @type {Set<string>} Track agents that failed to load (orphaned references) */
+  const skippedAgentIds = new Set();
+
   async function processAgent(agentId) {
     const agent = await getAgent({ id: agentId });
     if (!agent) {
-      throw new Error(`Agent ${agentId} not found`);
+      logger.warn(
+        `[processAgent] Handoff agent ${agentId} not found, skipping (orphaned reference)`,
+      );
+      skippedAgentIds.add(agentId);
+      return null;
     }
 
     const validationResult = await validateAgentModel({
@@ -187,37 +196,31 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
       userMCPAuthMap = config.userMCPAuthMap;
     }
     agentConfigs.set(agentId, config);
+    return agent;
   }
 
-  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) {
-          if (checkAgentInit(to)) {
-            continue;
-          }
-          await processAgent(to);
-        }
-      } else if (typeof edge.to === 'string' && checkAgentInit(edge.to)) {
-        continue;
-      } else if (typeof edge.to === 'string') {
-        await processAgent(edge.to);
-      }
 
-      if (Array.isArray(edge.from)) {
-        for (const from of edge.from) {
-          if (checkAgentInit(from)) {
-            continue;
-          }
-          await processAgent(from);
-        }
-      } else if (typeof edge.from === 'string' && checkAgentInit(edge.from)) {
-        continue;
-      } else if (typeof edge.from === 'string') {
-        await processAgent(edge.from);
+  // Graph topology discovery for recursive agent handoffs (BFS)
+  const { edgeMap, agentsToProcess, collectEdges } = createEdgeCollector(
+    checkAgentInit,
+    skippedAgentIds,
+  );
+
+  // Seed with primary agent's edges
+  collectEdges(primaryConfig.edges);
+
+  // BFS to load and merge all connected agents (enables transitive handoffs: A->B->C)
+  while (agentsToProcess.size > 0) {
+    const agentId = agentsToProcess.values().next().value;
+    agentsToProcess.delete(agentId);
+    try {
+      const agent = await processAgent(agentId);
+      if (agent?.edges?.length) {
+        collectEdges(agent.edges);
       }
+    } catch (err) {
+      logger.error(`[initializeClient] Error processing agent ${agentId}:`, err);
     }
   }
 
@@ -229,11 +232,12 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
       }
       await processAgent(agentId);
     }
-
     const chain = await createSequentialChainEdges([primaryConfig.id].concat(agent_ids), '{convo}');
-    edges = edges ? edges.concat(chain) : chain;
+    collectEdges(chain);
   }
 
+  let edges = Array.from(edgeMap.values());
+
   /** Multi-Convo: Process addedConvo for parallel agent execution */
   const { userMCPAuthMap: updatedMCPAuthMap } = await processAddedConvo({
     req,
@@ -261,6 +265,9 @@ const initializeClient = async ({ req, res, signal, endpointOption }) => {
     edges = [];
   }
 
+  // Filter out edges referencing non-existent agents (orphaned references)
+  edges = filterOrphanedEdges(edges, skippedAgentIds);
+
   primaryConfig.edges = edges;
 
   let endpointConfig = appConfig.endpoints?.[primaryConfig.endpoint];