Review system design on every pull request, not just the diff.

CodeBoarding analyzes your architecture before and after a change, then comments on the PR with an inline Mermaid diagram of what changed — added, modified, and deleted components and the relationships between them. It runs the CodeBoarding engine in CI: static analysis combined with LLM reasoning.

CodeBoarding · Website · Explore examples · VS Code extension · Discord

• Builds or reuses a baseline architecture analysis for the PR base.
• Runs incremental analysis on the PR head, then diffs components and relationships.
• Posts a sticky PR comment with an inline Mermaid map. Green is added, yellow is modified, red (dashed) is deleted, for both nodes and edges.

A PR comment looks like this:

graph LR
    Orchestration_Workflow_Manager["Orchestration & Workflow Manager"]
    Incremental_Analysis_Controller["Incremental Analysis Controller"]
    Static_Analysis_Engine["Static Analysis Engine"]
    Agentic_Intelligence_Core["Agentic Intelligence Core"]
    Health_Quality_Monitor["Health & Quality Monitor"]
    Rendering_Output_Engine["Rendering & Output Engine"]
    Persistence_Provider_Infrastructure["Persistence & Provider Infrastructure"]
    Orchestration_Workflow_Manager -- "triggers change detection" --> Incremental_Analysis_Controller
    Incremental_Analysis_Controller -- "passes filtered file sets" --> Static_Analysis_Engine
    Static_Analysis_Engine -- "provides CFGs and symbol tables" --> Agentic_Intelligence_Core
    Static_Analysis_Engine -- "supplies structural metrics" --> Health_Quality_Monitor
    Agentic_Intelligence_Core -- "delivers summaries and diagrams" --> Rendering_Output_Engine
    Health_Quality_Monitor -- "provides health reports" --> Rendering_Output_Engine
    Persistence_Provider_Infrastructure -- "supplies LLM clients" --> Agentic_Intelligence_Core
    Orchestration_Workflow_Manager -- "persists pipeline state" --> Persistence_Provider_Infrastructure
    classDef added fill:#1f883d,stroke:#0b5d23,color:#fff;
    classDef modified fill:#bf8700,stroke:#7d4e00,color:#fff;
    classDef deleted fill:#cf222e,stroke:#82071e,color:#fff,stroke-dasharray:5 3;
    class Health_Quality_Monitor added;
    class Static_Analysis_Engine,Agentic_Intelligence_Core modified;
    class Persistence_Provider_Infrastructure deleted;
    linkStyle 3,5 stroke:#1f883d,stroke-width:2px;
    linkStyle 2 stroke:#bf8700,stroke-width:2px;
    linkStyle 6,7 stroke:#cf222e,stroke-width:2px,stroke-dasharray:5 3;

Create .github/workflows/codeboarding.yml:

name: CodeBoarding review

on:
  pull_request:
    # Generate once, when the PR becomes reviewable, not on every push, so you
    # don't spend an LLM job per commit. Use [opened] for strictly creation-only,
    # or add `synchronize` to re-run on each push. Refresh anytime with /codeboarding.
    # 'closed' only cancels an in-flight review (see concurrency), it doesn't start one.
    types: [opened, reopened, ready_for_review, closed]
  issue_comment:
    types: [created]

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

concurrency:
  group: codeboarding-${{ github.event.pull_request.number || github.event.issue.number }}
  # Cancel only when the PR closes — bot comments (issue_comment) and re-triggers
  # must not cancel a running review; they queue behind it instead.
  cancel-in-progress: ${{ github.event_name == 'pull_request' && github.event.action == 'closed' }}

jobs:
  review:
    runs-on: ubuntu-latest
    timeout-minutes: 60
    if: >
      (github.event_name == 'pull_request' && github.event.action != 'closed' && github.event.pull_request.draft == false) ||
      (github.event_name == 'issue_comment' && github.event.issue.pull_request != null &&
       startsWith(github.event.comment.body, '/codeboarding') &&
       contains(fromJSON('["OWNER","MEMBER","COLLABORATOR"]'), github.event.comment.author_association))
    steps:
      - uses: CodeBoarding/CodeBoarding-action@v1
        with:
          llm_api_key: ${{ secrets.OPENROUTER_API_KEY }}

Add the API key as a repository secret (Settings → Secrets and variables → Actions):

OPENROUTER_API_KEY = sk-or-...

That is the only required setup, passed via llm_api_key above. For local runs with scripts/run_local.sh, export OPENROUTER_API_KEY as an environment variable instead.

Models are optional. Omit agent_model and parsing_model to use the engine's default for your provider, or pin them inline or from a repository variable (a model name is not a secret, so use vars., not secrets.):

        with:
          llm_api_key:   ${{ secrets.OPENROUTER_API_KEY }}  # secret
          agent_model:   anthropic/claude-sonnet-4          # optional; or ${{ vars.AGENT_MODEL }}
          parsing_model: google/gemini-3-flash-preview      # optional

OpenRouter is the default, but you can use any provider the engine supports. Set llm_provider and pass that provider's key:

        with:
          llm_provider: anthropic                  # omit for OpenRouter (default)
          llm_api_key:  ${{ secrets.ANTHROPIC_API_KEY }}

llm_provider: <name> hands your key to the engine as <NAME>_API_KEY, and the engine auto-selects that provider. Set exactly one key per run.

• On a PR being opened, reopened, or marked ready for review, the diagram is generated once (per the on: triggers above). It does not re-run on every push, so you never spend an LLM job per commit; the comment reflects that point until refreshed.
• On a /codeboarding comment, a trusted collaborator (OWNER, MEMBER, or COLLABORATOR) regenerates the diagram against the current PR head, even if one already exists. Each /codeboarding invocation posts a new comment and leaves earlier comments untouched (the automatic on-open comment, and any previous /codeboarding results, stay put). Change the keyword via trigger_command.

The command needs the issue_comment trigger and runs from your default branch (a GitHub rule), so it only works once the workflow is merged there. On-demand runs on fork PRs are refused, so fork code is never analyzed with your secrets.

• No checkout step is required in your workflow. This action checks out the target PR and the CodeBoarding engine internally.
• GitHub withholds secrets from fork PRs on pull_request, so fork runs fail early if an LLM key is unavailable.
• Do not use pull_request_target for this action. It can expose secrets to PR-head code.
• GitHub renders Mermaid in strict mode, so node click-through links are not supported in the PR diagram.

Fast path, no LLM calls:

scripts/run_local.sh --base-json /tmp/base.json --head-json /tmp/head.json

Full local pipeline:

export OPENROUTER_API_KEY=sk-or-...
scripts/run_local.sh --repo /path/to/repo --base <base-ref> --head <head-ref> \
  --engine /path/to/CodeBoarding

Useful flags:

--depth N
--render-depth N
--direction LR|TD|TB|RL|BT
--changed-only
--no-edge-labels
--out DIR
--no-open

MIT. See LICENSE.