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id tutorial-getting-started-error-handling
type procedural
created 2026-05-21 10:47:00 -0400
diataxis_type tutorial
title Get started with the error-handling plugin

Get started with the error-handling plugin

This tutorial walks you through installing the plugin and seeing both skills trigger on a real piece of code. You will:

  1. Install the plugin from the marketplace.
  2. Ask Claude to review a deliberately broken CLI error path — cdc-review fires.
  3. Ask Claude to add a dual-format error to the same code — cdc-err fires.
  4. See the two skills hand off cleanly.

You need: Claude Code installed, a terminal, and ~10 minutes.

1. Install the plugin

In Claude Code:

/plugin marketplace add zircote/cdc-error-plugin
/plugin install error-handling@cdc-errors

When the picker shows cdc-err, cdc-review, and cdc-handle under Available skills, the plugin is loaded.

2. Create the example code

Make a throwaway directory and paste this Python in app.py:

import sys, requests

def fetch(url):
    try:
        r = requests.get(url, timeout=5)
        r.raise_for_status()
        return r.json()
    except Exception:
        pass  # swallow

if __name__ == "__main__":
    data = fetch(sys.argv[1])
    print(data)

The bug is the bare except: pass — it swallows the cause chain and the program then crashes with a confusing TypeError because data is None.

3. Trigger cdc-review

In Claude Code, in that directory:

review the error handling in app.py

cdc-review activates. You should see:

  • a classified finding tagged [must-fix] for the swallowed exception,
  • a before/after diff that re-raises with cause preservation,
  • at least one [praise] finding (the timeout was set correctly).

This is the source-code-quality side of the plugin.

4. Trigger cdc-err

Now ask for the output format:

make app.py emit a problem+json envelope to stderr when the fetch fails

cdc-err activates. You should see:

  • a JSON envelope with the five RFC 9457 fields (type, title, status, detail, instance),
  • the three mandatory agent extensions (retry_after, suggested_fix, code_actions[]),
  • a --format=json|pretty flag with TTY auto-detection.

This is the CLI-output side.

5. See the handoff

Ask a question that crosses both:

review app.py's error output AND propagation

Both skills engage, each declining the other's scope and naming the sibling. cdc-review covers propagation; cdc-err covers the envelope.

Next steps