Agent web search crashes after scraper/reranker failures with Cannot read properties of undefined (reading 'role')

[dabarbarian125]

What happened?

When using an Agent with LibreChat web search enabled, some searches complete successfully, but searches that hit blocked/protected pages (such as Reddit, Facebook and Pinterest) can fail and then crash the agent pipeline with:

Cannot read properties of undefined (reading 'role')

This appears to happen after upstream web-search component failures such as:

• Jina reranker 429 Too Many Requests
• Firecrawl scraper 403 Forbidden

Public-web queries can work, which suggests the core agent/tool flow is functional, but scraper/reranker failure handling may be leaving an invalid or undefined message in agent state.

Expected behavior

If a scraper or reranker fails for one or more sources, LibreChat should:

• handle the failed source gracefully
• continue with remaining usable results, or return a normal partial-failure message
• not crash in LangGraph / message reduction

Actual behavior

The agent thinks/searches for a bit, then fails with:

Something went wrong. Here's the specific error message we encountered: An error occurred while processing the request: Cannot read properties of undefined (reading 'role')

Backend logs show the crash occurs in the agent completion path and then inside LangGraph message coercion.

Version Information

LibreChat version: 0.8.3

Model:

• MiniMax 2.5 (via OpenAI-compatible/custom endpoint in LibreChat)

Web search setup:

• Search provider: SearXNG
• Scraper: Firecrawl
• Reranker: initially Jina, later changed to Cohere
• No explicit webSearch: block in librechat.yaml initially; using default web-search env/UI behavior

Control / A-B behavior

This query worked successfully and did not appear to return social/protected sources:

• Who was the first person to swim across the English Channel?

This suggests the issue is not a general model/tool failure and is more likely triggered by upstream search-source failures.

Additional notes

• Missing provider auth lookup errors also appeared in logs, for example:

  • No plugin auth SERPER_API_KEY found
  • No plugin auth SEARXNG_API_KEY found
  • No plugin auth FIRECRAWL_API_URL found
  • No plugin auth JINA_API_KEY found
  • No plugin auth COHERE_API_KEY found

However, since public-web queries can succeed, these do not appear to be the primary failure by themselves.

Hypothesis

It looks like failed scrape/rerank results may be leaving an undefined entry in the agent message state, which later crashes LangGraph when LibreChat tries to coerce messages and read .role.

What I already tried

• Switched reranker from Jina to Cohere
• Confirmed that a public-web query succeeds
• Observed that failures correlate with protected/social sources and upstream 403/429 errors

Version Information

ghcr.io/danny-avila/librechat:v0.8.3 028dd86ddb43 3.42GB 748MB U

Steps to Reproduce

1. Configure LibreChat 0.8.3 with Agent web search enabled
2. Use:
   • SearXNG for search
   • Firecrawl for scraping
   • Jina or Cohere for reranking
3. Use a query that tends to return protected/social pages (Facebook, Reddit, etc.)
4. Wait for the agent to search/scrape
5. Observe that upstream scrape/rerank errors occur
6. The request then aborts with Cannot read properties of undefined (reading 'role')

Failing prompt: "Find me the cheapest price on Lehman's stainless steel cider press"
Working prompt: "Who was the first person to swim across the English Channel?"

What browsers are you seeing the problem on?

Chrome

Relevant log output

#### Secondary crash

{"level":"error","message":"[api/server/controllers/agents/client.js #sendCompletion] Operation aborted Cannot read properties of undefined (reading 'role')","pregelTaskId":"962d881e-1370-5be3-b8b9-ac0ed57d29be","stack":"TypeError: Cannot read properties of undefined (reading 'role')\n    at _isMessageFieldWithRole (/app/node_modules/@langchain/core/dist/messages/base.cjs:396:21)\n    at coerceMessageLikeToMessage (/app/node_modules/@langchain/core/dist/messages/utils.cjs:136:52)\n    at Array.map (<anonymous>)\n    at BinaryOperatorAggregate.messagesStateReducer [as operator] (/app/node_modules/@langchain/langgraph/dist/graph/message.cjs:20:38)\n    at BinaryOperatorAggregate.update (/app/node_modules/@langchain/langgraph/dist/channels/binop.cjs:57:35)\n    at _applyWrites (/app/node_modules/@langchain/langgraph/dist/pregel/algo.cjs:177:35)\n    at _localRead (/app/node_modules/@langchain/langgraph/dist/pregel/algo.cjs:76:9)\n    at __pregel_read (/app/node_modules/@langchain/langgraph/dist/pregel/algo.cjs:560:96)\n    at ChannelRead.doRead (/app/node_modules/@langchain/langgraph/dist/pregel/read.cjs:57:20)\n    at /app/node_modules/@langchain/langgraph/dist/graph/state.cjs:664:49","timestamp":"2026-03-17T05:15:21.149Z"}


#### Upstream scraper failure


{"level":"error","message":"Error scraping https://www.facebook.com/groups/FarmDirectMinnesota/posts/1419044669191349/: Firecrawl API request failed: Request failed with status code 403","timestamp":"2026-03-17T05:15:19.488Z"}


#### Earlier upstream reranker failure with same downstream crash


AxiosError: Request failed with status code 429
    at async JinaReranker.rerank (/app/node_modules/@librechat/agents/dist/cjs/tools/search/rerankers.cjs:40:30)
    at async getHighlights (/app/node_modules/@librechat/agents/dist/cjs/tools/search/search.cjs:67:20)
    at async Object.processSources (/app/node_modules/@librechat/agents/dist/cjs/tools/search/search.cjs:502:13)


and then:


[api/server/controllers/agents/client.js #sendCompletion] Operation aborted Cannot read properties of undefined (reading 'role')

Screenshots

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[danny-avila]

Thanks for the detailed report. The search tool's error handling is actually working correctly, scraper/reranker failures are caught at every level and always return valid results. The crash is from the model (MiniMax 2.5 via OpenAI-compatible endpoint) returning an empty stream, which pushes undefined into LangGraph's message state. The correlation with search failures is indirect, degraded tool output may trigger this behavior from certain providers.

I'm refactoring this area as part of a different effort, and a guard against empty model streams will be included. Moving to discussion since the root cause is provider-side.

[dabarbarian125]

Awesome thanks Danny!

[eric-chamberlain-tw]

@danny-avila I have some users seeing this error with our custom provider. What's a short term fix? Just make sure we don't return an empty stream to LibreChat?