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docs: use ChatPromptTemplate.fromMessages for LangChain chat prompts #2981

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docs: use ChatPromptTemplate.fromMessages for LangChain chat prompts #2981

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9878aa3
docs: use ChatPromptTemplate.fromMessages for LangChain chat prompts
bensondavis May 22, 2026
8167e01
docs: map getLangchainPrompt() to tuples in message-placeholders TS e…
bensondavis May 22, 2026
dceaec3
Merge branch 'main' into docs/fix-langchain-chat-prompt-from-messages
jannikmaierhoefer Jun 3, 2026
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4 changes: 2 additions & 2 deletions content/docs/prompt-management/features/message-placeholders.mdx
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Original file line number Diff line number Diff line change
Expand Up @@ -154,7 +154,7 @@ langfuse = get_client()
langfuse_prompt = langfuse.get_prompt("movie-critic-chat")

# Using langchain, you can obtain a MessagesPlaceholder object for unresolved placeholders
langchain_prompt = ChatPromptTemplate.from_template(langfuse_prompt.get_langchain_prompt())
langchain_prompt = ChatPromptTemplate.from_messages(langfuse_prompt.get_langchain_prompt())

# -> langchain_prompt = [
# SystemMessage(content="You are an expert movie critic"),
Expand All @@ -179,7 +179,7 @@ const langfusePrompt = await langfuse.prompt.get("movie-critic-chat", {
});

// Using langchain, you can obtain a ChatPromptTemplate with MessagesPlaceholder objects for unresolved placeholders
const langchainPrompt = ChatPromptTemplate.fromTemplate(
const langchainPrompt = ChatPromptTemplate.fromMessages(
langfusePrompt.getLangchainPrompt()
);
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6 changes: 3 additions & 3 deletions content/docs/prompt-management/features/variables.mdx
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Expand Up @@ -184,7 +184,7 @@ compiled = langchain_prompt.format(criticLevel="expert", movie="Dune 2")

# For chat prompts
langfuse_chat_prompt = langfuse.get_prompt("movie-critic-chat")
langchain_chat_prompt = ChatPromptTemplate.from_template(
langchain_chat_prompt = ChatPromptTemplate.from_messages(
langfuse_chat_prompt.get_langchain_prompt()
)

Expand Down Expand Up @@ -224,8 +224,8 @@ const compiled = await langchainPrompt.format({
const langfuseChatPrompt = await langfuse.prompt.get("movie-critic-chat", {
type: "chat",
});
const langchainChatPrompt = ChatPromptTemplate.fromTemplate(
langfuseChatPrompt.getLangchainPrompt()
const langchainChatPrompt = ChatPromptTemplate.fromMessages(
langfuseChatPrompt.getLangchainPrompt().map((m) => [m.role, m.content])
);

// Compile with variables
Expand Down