workerd

Methodology

Bug attribution uses symbol-level matching from commit history. For each fix commit, we look at the changed symbols (functions, classes, methods) and trace backwards to find who last modified that symbol in a non-fix commit. This person is the probable bug introducer. The algorithm only works when commits have symbol-level data from the Navigara analysis engine — the coverage rate shows what percentage of fix commits had this data available.

The Semantic Problem: Growth vs. Fixes Inversion

The current metrics model has a semantic inversion: when developer A creates a feature with a bug, they receive grow (positive). When developer B fixes that bug, they receive waste (negative). The bug creator is rewarded while the fixer is penalized. Bug attribution addresses this by explicitly tracking who introduced bugs and who fixed them, providing a more accurate picture of code quality contributions.

Proposed API Endpoint

Currently computed client-side from commit data. Ideal server-side endpoint:

POST /v1/repositories/{repositoryId}/bug-attributions
Content-Type: application/json

Request:
{
  "startTime": "2025-01-01T00:00:00Z",
  "endTime": "2025-12-31T23:59:59Z"
}

Response:
{
  "totalBugsAttributed": 42,
  "selfFixRate": 35,
  "coverageRate": 78,
  "attributions": [
    {
      "filePath": "src/lib/auth.ts",
      "symbol": "validateToken",
      "introducer": { "name": "Alice", "email": "alice@co.com", "commitSha": "abc123" },
      "fixer": { "name": "Bob", "email": "bob@co.com", "commitSha": "def456" },
      "fixedAt": "2025-06-15T10:30:00Z",
      "isSelfFix": false
    }
  ]
}

Methodology

Investment Quality reclassifies engineering effort based on bug attribution data. Commits identified as buggy origins (those that introduced bugs later fixed by someone) have their grow and maintenance time moved into the Wasted Time category. Their waste (fix commits) remains counted as productive. All other commits retain their standard classification: grow is productive, maintenance is maintenance, and waste (fixes) is productive.

Relationship to Growth / Maintenance / Fixes

The standard model classifies commits as Growth, Maintenance, or Fixes. Investment Quality adds a quality lens: a commit that introduced a bug is retrospectively counted as a poor investment — the engineering time spent on it was wasted because it ultimately required additional fix work. Fix commits (Fixes in the standard model) are reframed as productive, because fixing bugs is valuable work.

Proposed API Endpoint

Currently computed client-side from commit and bug attribution data. Ideal server-side endpoint:

POST /v1/organizations/{orgId}/investment-quality
Content-Type: application/json

Request:
{
  "startTime": "2025-01-01T00:00:00Z",
  "endTime": "2025-12-31T23:59:59Z",
  "bucketSize": "BUCKET_SIZE_MONTH",
  "groupBy": ["repository_id" | "deliverer_email"]
}

Response:
{
  "productivePct": 74,
  "maintenancePct": 18,
  "wastedPct": 8,
  "buckets": [
    {
      "bucketStart": "2025-01-01T00:00:00Z",
      "productive": 4.2,
      "maintenance": 1.8,
      "wasted": 0.6
    }
  ]
}