github-pr-autofix

GitHub PR autofix

Reconciler + agentic pattern that extends the PR validator with AI-powered auto-fixing using the metaagent framework.

What it does:

• Same validation as the PR validator, via the shared prvalidation library.
• When the driftlessaf/autofix label is present, the property ENABLE_AUTOFIX is set to true and validation fails, an AI agent running on Vertex AI automatically fixes the PR title and/or description.
• Supports both Gemini and Claude models, selected via the AGENT_MODEL env var, which defaults to gemini-3.8-flash.
• Updates the PR title to conventional commit format.
• Generates a meaningful description from PR context, including the list of validation issues and the list of changed files.
• Surfaces the model used, fixes applied, and agent reasoning in the Check Run output.
• Caps the number of agent invocations per PR generation to prevent loops, configurable via MAX_FIX_ATTEMPTS with a default of 2.

The reconciler concepts shared with the validator are documented in the main examples README; they cover the StatusManager, the Details payload, the idempotent reconcile loop, workqueue integration, and error handling.

Configuration

Env var	Default	Description
ENABLE_AUTOFIX	false	Master switch — when false, behaves identically to the validator
AUTOFIX_LABEL	driftlessaf/autofix	PR label that gates agent execution
GCP_PROJECT_ID	—	Vertex AI project. Required when ENABLE_AUTOFIX=true.
GCP_REGION	global	Vertex AI region
AGENT_MODEL	gemini-3.8-flash	Model identifier passed to Vertex AI
MAX_FIX_ATTEMPTS	2	Max agent invocations per PR generation, where a generation is the hash of SHA, title, and body

Switching to Claude Sonnet:

AGENT_MODEL=claude-sonnet-4-5@20250929

Agent tools

The agent is given two tools, both backed by func callbacks against the GitHub client so they can be unit-tested without a live API:

• update_pr_title — Updates the PR title. Validates the new title against prvalidation.ConventionalCommitRegex and a 72-character limit before calling GitHub.
• update_pr_description — Updates the PR body. Validates the new description is at least 20 characters after trimming.

After the agent finishes, the reconciler re-fetches the PR, re-runs prvalidation.ValidatePR, and records the outcome in the Check Run via statusmanager. The recorded outcome includes FixesApplied, AgentReasoning, and ModelUsed.

Architecture

 ┌──────────┐                              GCP
 │  GitHub  │    ┌────────────────────────────────────────────────────────────────┐
 │          │    │                                                                │
 │  PR open │    │  ┌─────────────┐   ┌──────────────────────┐                    │
 │  PR edit ├────┼─►│github-events├──►│  CloudEvents Broker  │                    │
 │          │    │  │  (webhook)  │   │  (filter + enqueue)  │                    │
 │          │    │  └─────────────┘   └──────────┬───────────┘                    │
 └────▲─────┘    │                               │                                │
      │          │                               ▼                                │
      │          │                    ┌──────────────────────┐                    │
      │          │                    │     Workqueue        │                    │
      │          │                    │  (rcv + dispatcher)  │                    │
      │          │                    └──────────┬───────────┘                    │
      │          │                               │                                │
      │          │                               ▼                                │
      │          │  ┌──────────────┐  ┌──────────────────────┐  ┌──────────────┐  │
      │          │  │   OctoSTS    │◄─│     Reconciler       │─►│  Metaagent   │  │
      │          │  │ (get token)  │  │ (validator + agent)  │  │  (Vertex AI) │  │
      │          │  └──────────────┘  └──────────┬───────────┘  └──────────────┘  │
      │          │                               │                                │
      └──────────┼───────────────────────────────┘                                │
  Check Run +    │    Create/Update Check Run + Update PR via GitHub API          │
  PR Updates     └────────────────────────────────────────────────────────────────┘

Flow:

1. GitHub sends a webhook when a PR is opened or edited.
2. github-events converts the webhook into a CloudEvent.
3. The CloudEvents Broker routes it onto the Workqueue.
4. The reconciler validates the PR title and description.
5. If validation fails, the driftlessaf/autofix label is present, and the fix-attempt budget is not exhausted:
   • Vertex AI is invoked through metaagent, using either Gemini or Claude as selected by AGENT_MODEL.
   • The agent calls update_pr_title and/or update_pr_description.
   • The reconciler re-validates the resulting PR state.
6. The Check Run is updated with the final results, including the model used and reasoning.

File layout

github-pr-autofix/
└── cmd/reconciler/
    ├── main.go       # Reconciler with label gating, attempt budget, agent orchestration
    ├── agent.go      # Metaagent construction (Gemini/Claude via Vertex AI)
    ├── prtools.go    # PRTools callbacks + ToolProvider implementation
    ├── prompts.go    # System and user prompts
    ├── types.go      # PRContext (request) and PRFixResult (response)
    ├── doc.go        # Package docs
    └── main_test.go  # Unit tests

Running tests

cd examples
go test ./github-pr-autofix/...

No GitHub credentials or Vertex AI access required — the agent path is exercised via mocked PRTools callbacks.