GitHub Action

The official ophi-dev/mehen GitHub Action computes changed-file metric trends on every pull request, compares them against the base branch, and publishes a sticky comment with the deltas. It is the primary consumption surface for mehen today.

Each cell shows the new value with the base-branch value in parentheses and a colored indicator — 🟢 improvement, 🔴 regression, ⚪ no material change — so reviewers see at a glance which files a PR made more or less complex.

Minimal workflow

.github/workflows/mehen.yml

name: mehen
on: pull_request

jobs:
  mehen:
    runs-on: ubuntu-latest
    permissions:
      contents: read
      pull-requests: write
      issues: write
    steps:
      - uses: actions/checkout@v6
        with:
          fetch-depth: 0

      - uses: ophi-dev/mehen@v1
        with:
          paths: src

That’s the whole setup. The action installs the mehen CLI, runs mehen diff against the PR’s base branch, and posts a sticky comment with the per-file metric deltas.

Polyglot monorepo

For monorepos, pass each tracked root and let mehen pick supported languages from changed files in those trees:

- uses: ophi-dev/mehen@v1
  with:
    paths: |
      crates/api/src
      apps/web/src
      tools
    thresholds: |
      cyclomatic=5
      cognitive=4
      loc.lloc=120

Inputs

Input	Default	Description
`version`	`""` (latest)	Version of the mehen npm package to run.
`install-method`	`npm`	How to provide the mehen CLI: `npm`, `cargo`, or `path`.
`mehen-path`	`mehen`	Path to a mehen executable when `install-method: path`.
`node-version`	`24`	Node.js version used by the action runner.
`paths`	`.`	Repository-relative files or directories to compare. Newline, comma, or semicolon separated.
`include`	`""`	Glob patterns to include.
`exclude`	`""`	Glob patterns to exclude.
`exclude-tests`	`true`	Exclude common test-file patterns (`_test.go`, `/__tests__/`, `.spec.ts`) on top of any user-provided excludes.
`metrics`	`""`	Comma-separated metrics passed to `mehen diff`.
`from`	`""`	Base git revision. Defaults to the PR base branch or `main`.
`to`	`""`	Head git revision. Defaults to the PR head SHA or `HEAD`.
`show-unchanged`	`false`	Include files where all selected metrics are unchanged.
`comment`	`true`	Create or update a pull request comment.
`github-token`	(workflow token)	GitHub token used to update PR comments.
`thresholds`	`""`	Adverse per-file delta limits, e.g. `cyclomatic=5,cognitive=3,loc.lloc=100`.
`fail-on-threshold`	`true`	Fail the action when any configured threshold is exceeded.
`comment-title`	`## 📊 Source Code Metrics`	Markdown heading used for the sticky comment.

Outputs

Output	Description
`violations`	Number of threshold violations.
`report_json`	Path to the JSON diff report produced by mehen.
`report_markdown`	Path to the rendered Markdown report.

Permissions

The action needs to write PR comments:

permissions:
  contents: read
  pull-requests: write
  issues: write

contents: read lets the runner check out the repo. pull-requests: write and issues: write let the action upsert the sticky comment.

Sticky comment

The action posts a single comment on the PR and updates it on each push instead of stacking new comments. The Markdown layout, cell format, and callout catalog are documented on the PR comment design page.

Markdown documentation section

When a PR touches Markdown files, mehen diff emits a Documentation Metrics section inside the same sticky comment, anchored by  (visible in the screenshot above). It carries a five-column headline table (DMI, Words, FKGL/Tateishi RS, Link Debt, Filler Risk), severity-ranked callouts drawn from a fixed template catalog, and a collapsed drill-down with the deeper structural, wording, and readability tables. On code-only PRs the section is suppressed entirely. The full specification — anchor rules, cell format, callout catalog, and --fail-on gating — is on the PR comment design page.

SQL in the diff

SQL files are analyzed automatically and appear in the same Source Code Metrics table on the PR comment. Because SQL and source-code files publish different metric families, a mixed PR renders a single table whose columns are the union of each language’s defaults — every row fills only the columns its analyzer emits, and the rest render as –. This keeps SQL changes visible on the default action path instead of silently dropping out. See mehen diff for how the default metric set is resolved per file language.

Examples

Strict gating
Comment-only (advisory)
Pin a version
Use a pre-installed binary

- uses: ophi-dev/mehen@v1
  with:
    paths: src
    thresholds: |
      cyclomatic=3
      cognitive=3
    fail-on-threshold: true

- uses: ophi-dev/mehen@v1
  with:
    paths: src
    fail-on-threshold: false

- uses: ophi-dev/mehen@v1
  with:
    paths: src
    version: "1.1.0"

- run: cargo binstall --git https://github.com/ophi-dev/mehen mehen
- uses: ophi-dev/mehen@v1
  with:
    install-method: path
    mehen-path: $(which mehen)
    paths: src

​Minimal workflow

​Polyglot monorepo

​Inputs

​Outputs

​Permissions

​Sticky comment

​Markdown documentation section

​SQL in the diff

​Examples

​See also