ai-agents-langchain-prompt-pla-calling-getlangchainprompt-without-resolving-all-p-62b64650

THEN Upgrade to Langfuse JS/TS SDK v4.2.0 or later, where the issue is fixed. If upgrade not possible, manually transform the output: map objects with variableName and optional to { type: 'placeholder', name: msg.variableName } before passing to ChatPromptTemplate.fromMessages().

const rawMessages = langfusePrompt.getLangchainPrompt();
const fixedMessages = rawMessages.map(msg => {
  if (msg.variableName && typeof msg.optional === "boolean") {
    return { type: "placeholder", name: msg.variableName };
  }
  return msg;
});
const langchainPrompt = ChatPromptTemplate.fromMessages(fixedMessages);