[Bug]: Agents API (Chat Completions + Responses) fails for multi-agent handoffs

[zachmak]

What happened?

Multi-agent orchestrator agents work correctly through the LibreChat web UI but fail with a 500 error when called through the Agents API endpoints (/api/agents/v1/chat/completions and
/api/agents/v1/responses).

Error:
Error: Found edge ending at unknown node agent_q3Yf1J3NqKONncExJKt0F
at StateGraph.validate (node_modules/@langchain/langgraph/dist/graph/graph.cjs:317:23)
at StateGraph.compile (node_modules/@langchain/langgraph/dist/graph/state.cjs:398:14)
at MultiAgentGraph.createWorkflow (node_modules/@librechat/agents/dist/cjs/graphs/MultiAgentGraph.cjs:907:24)
at Run.createMultiAgentGraph (node_modules/@librechat/agents/dist/cjs/run.cjs:126:32)
at Run.create (node_modules/@librechat/agents/dist/cjs/run.cjs:136:16)

Root cause:

The UI path (api/server/services/Endpoints/agents/initialize.js, ~lines 170-240) performs BFS edge discovery via createEdgeCollector(), loading and initializing all sub-agents referenced in the
orchestrator's edges before passing the full agents array to createRun().

The API controllers (api/server/controllers/agents/openai.js and responses.js) skip this entirely. They only load the primary agent and pass agents: [primaryConfig] to createRun(). However, the
primary agent's edges still reference sub-agent IDs. When createRun() detects edges, it sets the graph type to multi-agent and builds a MultiAgentGraph. The graph builder only adds nodes for agents
in the array (just the primary), but the edges point to sub-agent IDs that were never registered as nodes. StateGraph.validate() then fails.

Environment:

• LibreChat version: 0.8.4
• Node.js: 20.20.1
• Deployment: Kubernetes

Version Information

Environment:

• LibreChat version: 0.8.4
• Node.js: 20.20.1
• Deployment: Kubernetes

Steps to Reproduce

Steps to reproduce:

1. Create a multi-agent orchestrator (Agent A) that delegates to sub-agents (Agent B, Agent C) via edges
2. Verify it works through the LibreChat web UI
3. Call Agent A through the Agents API:
   POST /api/agents/v1/chat/completions
   Authorization: Bearer <api_key>
   {"model": "<agent_a_id>", "messages": [{"role": "user", "content": "Hello"}], "stream": true}
4. Returns HTTP 500 with the Found edge ending at unknown node error

What browsers are you seeing the problem on?

No response

Relevant log output

Error: Found edge ending at unknown node `agent_q3Yf1J3NqKONncExJKt0F`
      at StateGraph.validate (node_modules/@langchain/langgraph/dist/graph/graph.cjs:317:23)
      at StateGraph.compile (node_modules/@langchain/langgraph/dist/graph/state.cjs:398:14)
      at MultiAgentGraph.createWorkflow (node_modules/@librechat/agents/dist/cjs/graphs/MultiAgentGraph.cjs:907:24)
      at Run.createMultiAgentGraph (node_modules/@librechat/agents/dist/cjs/run.cjs:126:32)
      at Run.create (node_modules/@librechat/agents/dist/cjs/run.cjs:136:16)

Screenshots

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

[snsn3]

Same issue here, when running the request via API. Everything works great in the UI but via API, only agents without chain/handoff work as expected.

Retry 1/2 after error: HTTP 500: {"error":{"message":"Found edge ending at unknown node agent_","type":"server_error","param":null,"code":null}}
Retry 2/2 after error: HTTP 500: {"error":{"message":"Found edge ending at unknown node agent_","type":"server_error","param":null,"code":null}}
Status: failed
Error: HTTP 500: {"error":{"message":"Found edge ending at unknown node agent_t","type":"server_error","param":null,"code":null}}