Working with langfuse on a new team, need help to see on the traces the placeholder of "system" on the traces

[juanfernandezntt]

thanks en advance of the help, i´m stucking trying to donwload a traces to build a llm/judge but have problems with the system prompts inside of the traces, because is not visible in the file, only in the ui and from a mouse hold, i hope you see more clear what i mean on the pic:

thanks

[dosubot]

Hi @juanfernandezntt! I'm Dosu and I’m helping the langfuse-docs team.

The reason you can't see the "system" prompt in downloaded trace files is that Langfuse only shows it in the UI by default—it isn't automatically linked or exported with traces unless you add explicit instrumentation. If you use just the prompt text (like passing it as system_prompt), Langfuse doesn't trace or link it to generations for export.

To make system prompts visible in your trace exports, you need to manually log the prompt usage to Langfuse after your LLM call. For example, in Python, after you use the prompt, create a trace or span and include the prompt text and any relevant metadata. This way, the prompt will be part of the trace data you export. Here’s a rough example:

from langfuse import Langfuse

langfuse_client = Langfuse()

# Use your prompt text in the LLM call
prompt_text = langfuse_chat_prompt.prompt

# After the call, log the prompt usage
trace = langfuse_client.create_trace(
    name="llm-call",
    input={"prompt": prompt_text},
    metadata={"langfuse_prompt_id": langfuse_chat_prompt.id}
)

# Optionally, log the LLM output as well
langfuse_client.create_span(
    trace_id=trace.id,
    name="llm-generation",
    output={"response": llm_response},
    metadata={"prompt_id": langfuse_chat_prompt.id}
)

This is a known limitation in Langfuse’s Python integration—there’s no out-of-the-box way to link prompts to traces automatically when you only use the prompt text. Manual logging is the current workaround. For more details, see this discussion.

To reply, just mention @dosu.

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[kowyo]

It is hard to view system prompt in UI as well.