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LLM signals let you extract structured data that cannot be explicitly logged but can be inferred from trace data. You define a prompt that describes what to look for (for example, “Agent completes checkout process”), and Laminar sends the signal definition plus the trace_id to the semantic-event service. The service returns a structured payload that Laminar stores as a signal event linked to that trace.

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When to use LLM signals

  • Business outcomes - Describe criteria for a successful outcome, for example “User responded with ‘Thank you’”.
  • Logical errors - Describe a case when an agent fails to complete a task, for example “Agent fails to complete checkout process”.
  • Behavioral patterns - Categorize user requests by specifying “request category” in the structured output schema.
If you already log structured events in your application code, you do not need LLM signals for those.

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Create a signal (UI)

To define a new signal from trace data:
Create new signal form showing name, prompt, structured output schema, and test trace
  1. Open Signals and click Create signal.
  2. (Optional) Start from a template to prefill the prompt and schema.
  3. Fill in:
    • Name: choose a stable signal name (for example, checkout.completed or navigation.failed).
    • Prompt: describe what the signal should detect or extract from trace data.
    • Structured Output: define a JSON schema for the signal payload (keep it small and stable).
    • (Optional) Test Signal: enter a trace ID to validate the output before creating it.
  4. Click Create.

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Run the signal on traces

Once the signal exists:
  • Use Jobs to backfill a time range or filtered set of traces.
  • Use Triggers to keep the signal running on new traces that match your trigger filters.

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Jobs (backfill)

Use a job when you want to run a signal against historical traces or a filtered slice of data. How it works in the UI:
  • Go to the signal’s Jobs tab and click Create Job.
  • Pick a time range (default is the last 24 hours).
  • Add filters and/or search to narrow the trace set.
  • Select either specific traces or all traces matching your filters.
  • Click Create signal job to enqueue processing.
What to expect:
  • A job creates one run per trace.
  • Runs appear in the Runs tab with status (Pending, Completed, Failed).
  • If the signal is identified, you will see an Event ID and the signal appears in the Events tab.
  • If the signal is not identified, the run completes without an event.

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Triggers (live)

Use a trigger to run the signal automatically on new traces. How it works in the UI:
  • Go to the signal’s Triggers tab and click Add Trigger.
  • Add one or more filters (all conditions must match).
  • The trigger runs on new traces that match those filters.
What to expect:
  • Each matching trace creates a run with source “Trigger.”
  • Signal events appear in the Events tab when identified.

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Viewing signal events

In the Laminar dashboard:
Signals events table with filters and trace links
  1. Go to Signals and open your signal.
  2. Use Events to see the raw event stream and jump to traces.
  3. (Optional) Query signal events in the SQL Editor using the signal_events table.
Once you have LLM signals running, you can cluster them to discover patterns and group similar events together.