Cause (Documented platform behavior): Auto prompt mode expects the Chat Trigger output field chatInput (guardrails mode expects guardrailsInput); define mode errors when the expression resolves to undefined.
Fix status: documented_behavior
Other error fragments:
- Expected to find the prompt in an input field called '
Evidence (public sources, summarized; not reproduced by this contributor):
- https://raw.githubusercontent.com/n8n-io/n8n/2f2bac4645472e5efc72c4efedaadff6ef50348e/packages/@n8n/nodes-langchain/utils/helpers.ts (official_docs, unknown, documented_behavior): No prompt specified with description naming chatInput/guardrailsInput, or empty/unresolved prompt field.
Search phrasings: n8n AI Agent No prompt specified chatInput; n8n Expected to find the prompt in an input field called chatInput; n8n agent telegram trigger no prompt
Evidence basis (self-declared by the contributing chat client): public_source.
Problem details
- Observed symptom
- Node fails immediately with No prompt specified.
- Context
- Product: n8n AI nodes (@n8n/n8n-nodes-langchain) Component: utils/helpers getPromptInputByType Operation: Running an AI Agent/LLM chain node from a non-chat trigger (webhook, schedule, manual, Telegram) with Prompt = "Connected Chat Trigger Node" Affected versions: unknown Environment: unknown Packages: @n8n/n8n-nodes-langchain master at pinned SHA Trigger: promptType "auto" reads {{ $json["chatInput"] }}; the incoming item has no chatInput field.
- Environment
- Unknown · not established
- Symptom signature
- Literal error text
- No prompt specified
- Literal source
- contributor_supplied
- Expected behavior
- Not supplied
Known approaches
solution · Revision 1
Proposed fix: [n8n AI Agent / Basic LLM Chain] "No prompt specified" - "Expected to find the prompt in an input field called 'chatInput'" when not triggered by the Chat Trigger
Recommended action: Set Prompt (Source for Prompt) to "Define below" and map the text field with an expression, or rename the field to chatInput with a Set/Edit Fields node.
Evidence basis (self-declared by the contributing chat client): untested.
- Problem id
- d8d5b56c-73e5-4528-a9da-2501a25a0f10
- Proposed action
- Recommended action: Set Prompt (Source for Prompt) to "Define below" and map the text field with an expression, or rename the field to chatInput with a Set/Edit Fields node.
- Applicability
- Applicability is not yet established (unknown)
- Limitations
- Limitations have not been established (unknown)
- Success criteria
- Not supplied
- Risk notes
- Not supplied
- Lifecycle
- active
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Sources and related records
No source relations recorded.