---
url: /en/build/showcase/ai-review.md
---
With AI capabilities, you can let pipelines automatically review Pull Requests (PRs), quickly discovering potential issues and improving code quality.

**Cloud Native Build** supports two ways to perform AI code reviews. You can choose the method that suits your scenario.

## Token Overview

The pipeline provides three NPC-related environment variables. They all have the same permissions and represent the pipeline trigger, only differing in which NPC role they represent:

| Environment Variable | Description |
|---------------------|-------------|
| `CNB_TOKEN` | When mentioning a custom NPC role, represents the mentioned custom role |
| `CNB_TOKEN_FOR_CODEBUDDY` | When mentioning the system role CodeBuddy, represents the system role CodeBuddy |
| `CNB_TOKEN_FOR_AI` | Can be used by users in non-NPC pipelines as needed |

## Comparison

| Comparison | Method 1: AI Review Plugin | Method 2: NPC Event |
|------------|---------------------------|---------------------|
| Trigger | Automatic via pipeline | Mention NPC in PR comment |
| Token used | `CNB_TOKEN_FOR_AI` | `CNB_TOKEN` (custom role) or `CNB_TOKEN_FOR_CODEBUDDY` (system role) |
| Use case | Auto-review every PR event | On-demand review, flexible control |
| Config location | `.cnb.yml` pipeline config | `.cnb.yml` + `.cnb/settings.yml` (custom role) |

## Method 1: Use AI Review Plugin

Use the `cnbcool/ai-review` image as a pipeline plugin to automatically perform code review when PR events are triggered.

### Configuration Example

```yaml title=".cnb.yml"
main:
  pull_request:
    - stages:
        - name: Code Review
          image: cnbcool/ai-review:latest
          settings:
            type: code-review
```

### How It Works

1. When a PR is created or updated on the `main` branch, the pipeline is automatically triggered.
2. The pipeline can use the `CNB_TOKEN_FOR_AI` environment variable to call the OpenAPI AI capability.
3. The AI reviews the code changes in the PR and submits review results as comments on the PR.

### Use Cases

* Automatically get AI review feedback on every PR
* Enforce quality checks before merging code

## Method 2: Trigger NPC Event

Mention an NPC role in a PR comment to trigger the NPC event pipeline and perform AI review.

### How to Trigger

* **System NPC**: Simply mention `@CodeBuddy` in the PR comment, for example:

```text
@CodeBuddy Code review
```

* **Custom NPC**: First [configure a custom NPC role](../npc.md#custom-npc) in your repository, then mention it in the PR comment, for example:

```text
@cnb/feedback(评审专家) Code review
```

### NPC Event How It Works

1. When someone comments and mentions an NPC in a PR, it triggers the `pull_request.comment@npc` event.
2. The system loads the `.cnb.yml` configuration from the NPC's repository and parses the corresponding role's event pipeline.
3. The pipeline calls the OpenAPI AI capability using the token:
   * When mentioning a custom NPC, uses `CNB_TOKEN`, representing the mentioned custom role
   * When mentioning the system role CodeBuddy, uses `CNB_TOKEN_FOR_CODEBUDDY`, representing the system role CodeBuddy
4. The review results are submitted to the PR comment with the NPC's identity.

For detailed configuration, see [NPC](../npc.md).

### NPC Event Use Cases

* Trigger review on demand instead of every PR automatically
* Use custom review roles and styles
* Let NPC perform other automation tasks during the review

## Notes

* Both methods require ensuring the pipeline has sufficient permissions to access the code repository and submit comments.
* When the NPC event pipeline runs, its TOKEN permissions are limited to the current repository.
* If you need to make code changes during review, you can enable [NPC Work Mode](../npc.md#work-mode).