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Comet Opik is an open-source platform for evaluating, testing, and monitoring LLM applications.

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Step 1: Get your Opik credentials

In Comet, set up your Opik workspace and project:
  1. Log in to your Comet account
  2. Create or select a workspace for your LLM traces
  3. Create a project within the workspace
  4. Go to Settings > API Keys to create or copy your API key

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Step 2: Enable Broadcast in OpenRouter

Go to Settings > Observability and toggle Enable Broadcast.
Enable Broadcast

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Step 3: Configure Comet Opik

Click the edit icon next to Comet Opik and enter:
  • Api Key: Your Comet API key (starts with opik_...)
  • Workspace: Your Comet workspace name
  • Project Name: The project name where traces will be logged

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Step 4: Test and save

Click Test Connection to verify the setup. The configuration only saves if the test passes.

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Step 5: Send a test trace

Make an API request through OpenRouter and view the trace in your Opik project dashboard.
Opik Trace View

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Custom Metadata

Comet Opik supports custom metadata on both traces and spans for organizing and filtering your LLM evaluations.

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Supported Metadata Keys

KeyOpik MappingDescription
trace_idTrace metadata (openrouter_trace_id)Group multiple requests into a single trace
trace_nameTrace NameCustom name displayed in the Opik trace list
span_nameSpan NameName for intermediate spans in the hierarchy
generation_nameSpan NameName for the LLM generation span

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Example

{
  "model": "openai/gpt-4o",
  "messages": [{ "role": "user", "content": "Evaluate this response..." }],
  "user": "user_12345",
  "session_id": "session_abc",
  "trace": {
    "trace_name": "Response Quality Eval",
    "generation_name": "Quality Assessment",
    "eval_suite": "quality_v2",
    "test_case_id": "tc_001"
  }
}

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Additional Context

  • Custom metadata keys from trace are included in both the trace and span metadata objects
  • Cost information (input, output, total) is automatically added to span metadata
  • Model parameters and finish reasons are included in span metadata when available
  • The user field maps to user identification in trace metadata
  • Opik uses UUIDv7 format for trace and span IDs internally; original OpenRouter IDs are stored in metadata as openrouter_trace_id and openrouter_observation_id

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Privacy Mode

When Privacy Mode is enabled for this destination, prompt and completion content is excluded from traces. All other trace data — token usage, costs, timing, model information, and custom metadata — is still sent normally. See Privacy Mode for details.