Local development guide

This guide provides instructions for setting up and using local development features for Gemini CLI.

Tracing

Gemini CLI uses OpenTelemetry (OTel) to record traces that help you debug agent behavior. Traces instrument key events like model calls, tool scheduler operations, and tool calls.

Traces provide deep visibility into agent behavior and help you debug complex issues. They are captured automatically when you enable telemetry.

View traces

You can view traces using Genkit Developer UI, Jaeger, or Google Cloud.

Use Genkit

Genkit provides a web-based UI for viewing traces and other telemetry data.

Start the Genkit telemetry server:

Run the following command to start the Genkit server:
```
npm run telemetry -- --target=genkit
```
The script will output the URL for the Genkit Developer UI. For example: Genkit Developer UI: http://localhost:4000
Run Gemini CLI:

In a separate terminal, run your Gemini CLI command:
```
gemini
```
View the traces:

Open the Genkit Developer UI URL in your browser and navigate to the Traces tab to view the traces.

Use Jaeger

You can view traces in the Jaeger UI for local development.

Start the telemetry collector:

Run the following command in your terminal to download and start Jaeger and an OTel collector:
```
npm run telemetry -- --target=local
```
This command configures your workspace for local telemetry and provides a link to the Jaeger UI (usually http://localhost:16686).
- Collector logs: ~/.gemini/tmp/<projectHash>/otel/collector.log
Run Gemini CLI:

In a separate terminal, run your Gemini CLI command:
```
gemini
```
View the traces:

After running your command, open the Jaeger UI link in your browser to view the traces.

Use Google Cloud

You can use an OpenTelemetry collector to forward telemetry data to Google Cloud Trace for custom processing or routing.

Warning: Ensure you complete the Google Cloud telemetry prerequisites (Project ID, authentication, IAM roles, and APIs) before using this method.

Configure .gemini/settings.json:

{
  "telemetry": {
    "enabled": true,
    "target": "gcp",
    "useCollector": true
  }
}

Start the telemetry collector:

Run the following command to start a local OTel collector that forwards to Google Cloud:
```
npm run telemetry -- --target=gcp
```
The script outputs links to view traces, metrics, and logs in the Google Cloud Console.
- Collector logs: ~/.gemini/tmp/<projectHash>/otel/collector-gcp.log
Run Gemini CLI:

In a separate terminal, run your Gemini CLI command:
```
gemini
```
View logs, metrics, and traces:

After sending prompts, view your data in the Google Cloud Console. See the telemetry documentation for links to Logs, Metrics, and Trace explorers.

For more detailed information on telemetry, see the telemetry documentation.

Instrument code with traces

You can add traces to your own code for more detailed instrumentation.

Adding traces helps you debug and understand the flow of execution. Use the runInDevTraceSpan function to wrap any section of code in a trace span.

Here is a basic example:

import { runInDevTraceSpan } from '@google/gemini-cli-core';
import { GeminiCliOperation } from '@google/gemini-cli-core/lib/telemetry/constants.js';

await runInDevTraceSpan(
  {
    operation: GeminiCliOperation.ToolCall,
    attributes: {
      [GEN_AI_AGENT_NAME]: 'gemini-cli',
    },
  },
  async ({ metadata }) => {
    // metadata allows you to record the input and output of the
    // operation as well as other attributes.
    metadata.input = { key: 'value' };
    // Set custom attributes.
    metadata.attributes['custom.attribute'] = 'custom.value';

    // Your code to be traced goes here.
    try {
      const output = await somethingRisky();
      metadata.output = output;
      return output;
    } catch (e) {
      metadata.error = e;
      throw e;
    }
  },
);

In this example:

operation: The operation type of the span, represented by the GeminiCliOperation enum.
metadata.input: (Optional) An object containing the input data for the traced operation.
metadata.output: (Optional) An object containing the output data from the traced operation.
metadata.attributes: (Optional) A record of custom attributes to add to the span.
metadata.error: (Optional) An error object to record if the operation fails.

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