Manage Gemini Tracing

Setup Gemini Tracing

Configure OpenInference tracing for Gemini CLI sessions to Arize AX (cloud) or Phoenix (self-hosted). Spans are sent directly to the backend from hooks -- no background process or backend-specific dependencies are needed in the user's environment.

How to Use This Skill

This skill follows a decision tree workflow. Start by asking the user where they are in the setup process:

1. Is the harness already installed?

   • Check ~/.gemini/settings.json for 8 hook entries with name: arize-tracing
   • Check ~/.arize/harness/config.json for the harnesses.gemini block
   • If both are present -> Jump to Validate or Troubleshoot

2. Do they already have credentials?

   • Yes -> Jump to Configure Settings
   • No -> Continue to step 3

3. Which backend do they want to use?

   • Phoenix (self-hosted) -> Go to Set Up Phoenix
   • Arize AX (cloud) -> Go to Set Up Arize AX

4. Are they troubleshooting?

   • Yes -> Jump to Troubleshoot

Important: Only follow the relevant path for the user's needs. Don't go through all sections.

Set Up Phoenix

Phoenix is self-hosted. No Python dependencies are needed for tracing -- spans are sent directly via send_span() using stdlib urllib.

Install Phoenix

Ask if they already have Phoenix running. If not, walk through:

# Option A: pip
pip install arize-phoenix && phoenix serve

# Option B: Docker
docker run -p 6006:6006 arizephoenix/phoenix:latest

Phoenix UI will be available at http://localhost:6006. Confirm it's running:

curl -sf http://localhost:6006/v1/traces >/dev/null && echo "Phoenix is running" || echo "Phoenix not reachable"

Then proceed to Configure Settings with the Phoenix endpoint.

Set Up Arize AX

Arize AX is available as a SaaS platform or as an on-prem deployment. Users need an account, a space, and an API key.

First, ask the user: "Are you using the Arize SaaS platform or an on-prem instance?"

• SaaS -> Uses the default endpoint (otlp.arize.com:443). Continue below.
• On-prem -> The user will need to provide their custom OTLP endpoint (e.g., otlp.mycompany.arize.com:443). Ask for it and note it for the Configure Settings step.

1. Create an account

If the user doesn't have an Arize account:

• SaaS: Sign up at https://app.arize.com/auth/join
• On-prem: Contact their administrator for access to the on-prem instance

2. Get Space ID and API key

Walk the user through finding their credentials:

1. Log in to their Arize instance (https://app.arize.com for SaaS, or their on-prem URL)
2. Click Settings (gear icon) in the left sidebar
3. The Space ID is shown on the Space Settings page
4. Go to the API Keys tab
5. Click Create API Key or copy an existing one

Both api_key and space_id are required for the shared config.

No Python dependencies are needed. Both Phoenix and Arize AX use HTTP/JSON -- no additional Python dependencies are needed.

Then proceed to Configure Settings. If the user is on an on-prem instance, remind them to provide their custom endpoint.

Configure Settings

Important: Users must run this setup before tracing will work. The send_span() function requires ~/.arize/harness/config.json to exist for backend credential resolution.

Ask the user for:

1. Backend choice: Phoenix or Arize AX
2. Credentials (only if no existing config):
   • Phoenix: endpoint URL (default: http://localhost:6006), optional API key
   • Arize AX: API key and Space ID
3. OTLP Endpoint (Arize AX only, optional): For hosted Arize instances using a custom endpoint. Defaults to otlp.arize.com:443.
4. Project name (optional): defaults to "gemini", stored under harnesses.gemini.project_name
5. User ID (optional): Set ARIZE_USER_ID env var to identify spans by user (useful for teams)

Write the config

The config file at ~/.arize/harness/config.json is the single source of truth for backend credentials and per-harness settings. Create the directory structure if needed: mkdir -p ~/.arize/harness/{bin,run,logs,state/gemini}

Important: read-merge-write. If ~/.arize/harness/config.json already exists, read it first, then merge in the new or updated fields (e.g., add/update the harnesses.gemini entry) while preserving existing backend credentials. Only prompt for backend credentials if no existing config is found.

Phoenix:

{
  "harnesses": {
    "gemini": {
      "project_name": "gemini",
      "target": "phoenix",
      "endpoint": "<endpoint>",
      "api_key": ""
    }
  }
}

Arize AX:

{
  "harnesses": {
    "gemini": {
      "project_name": "gemini",
      "target": "arize",
      "endpoint": "otlp.arize.com:443",
      "api_key": "<key>",
      "space_id": "<id>"
    }
  }
}

If the user has a custom OTLP endpoint, set it in harnesses.gemini.endpoint.

Activate Gemini hooks

Gemini CLI uses ~/.gemini/settings.json for hook registration. Hooks are configured under hooks.<EventName> as an array of matcher/hook objects.

Install or reinstall via the installer:

./install.sh gemini

To uninstall:

./install.sh uninstall gemini

The installer registers all 8 hook events (SessionStart, SessionEnd, BeforeAgent, AfterAgent, BeforeModel, AfterModel, BeforeTool, AfterTool) in ~/.gemini/settings.json with name: arize-tracing on each entry.

Validate

1. Config exists: Run cat ~/.arize/harness/config.json to verify the config file exists and has correct backend credentials under harnesses.gemini.
2. Phoenix (if applicable): Run curl -sf <endpoint>/v1/traces >/dev/null to check connectivity.
3. Hooks active: Verify ~/.gemini/settings.json contains 8 hook entries with name: arize-tracing.
4. Quick dry-run test (optional):

   echo '{"event":"BeforeModel"}' | ARIZE_DRY_RUN=true arize-hook-gemini-before-model
   

Confirm

Tell the user:

• Config saved to ~/.arize/harness/config.json
• Gemini CLI hooks activated via ~/.gemini/settings.json
• Spans are sent directly to the backend from hooks -- no background process needed
• After saving, open a new Gemini CLI session and traces will appear in their Phoenix UI or Arize AX dashboard under the project name
• Mention ARIZE_DRY_RUN=true to test without sending data (set as env var before launching Gemini CLI)
• Mention ARIZE_VERBOSE=true for debug output
• Errors are always written to ~/.arize/harness/logs/gemini.log; set ARIZE_VERBOSE=true in the shell before launching Gemini CLI to also capture routine hook activity
• Toggle tracing on/off via ARIZE_TRACE_ENABLED env var (must be exported in the user's shell -- Gemini hooks read host env vars)
• Tail the log file at ~/.arize/harness/logs/gemini.log for real-time debugging

Hook Events

Gemini CLI fires 8 hook events. Each event is registered in ~/.gemini/settings.json and maps to a dedicated CLI entry point.

Troubleshoot

Common issues and fixes for Gemini CLI: