New Cask Agent Skill

Creating a New Homebrew Cask

You are orchestrating the creation of a new Homebrew cask. This skill coordinates multiple specialist agents and scripts to complete the workflow.

IMPORTANT: This skill runs in the main conversation context. You will use the Task tool to spawn agents for specialized work.

Input

URL provided: $ARGUMENTS

If no URL was provided, ask the user for:

• The app name, OR
• A download URL (direct link to DMG/ZIP), OR
• The product homepage (you'll find the download link)

Workflow Overview

1. Pre-flight checks    → Agent: pre-flight-checker
2. Download & inspect   → Agent: app-inspector
3. Livecheck strategy   → Agent: livecheck-advisor
4. Write cask file      → Agent: cask-writer
5. Testing              → Automated tests, install, createzap, uninstall
6. Submit PR            → Agent: pr-submitter

Create a task list to track progress through these steps.

Step-by-Step Execution

Step 1: Pre-flight Checks

Before investing time, verify the app is suitable:

Use the Task tool:
- subagent_type: homebrew:pre-flight-checker
- prompt: Check if this app is suitable for homebrew-cask submission.
  <include whatever info you have: URL, app name, homepage>

The agent will derive any missing info (app name from URL, homepage via search, etc.) and include it in the output.

Capture from output: App name, homepage, download URL, description - you'll need these for later steps.

Decision point: If the agent returns REJECT, stop and explain why to the user. If CAUTION, inform the user and ask if they want to proceed.

Step 2: Download and Inspect

Download and inspect the app in one step:

Use the Task tool:
- subagent_type: homebrew:app-inspector
- prompt: Download and inspect the app.
  Download URL: <url>
  Homepage: <homepage>

The agent will download the file, compute the SHA256, extract all metadata, and run Homebrew's generate_cask_token tool to get the canonical token.

Capture from output: Suggested token, SHA256, version, bundle ID, app name, min macOS, auto-update info (framework, appcast URL if found), architecture.

Use the suggested token from app-inspector for subsequent steps. This token comes from Homebrew's tooling and handles naming conventions and collision detection.

Note on versioned URLs: If the download URL is unversioned (e.g., App.dmg), the livecheck-advisor may find a versioned URL in an appcast, release feed, or other source. If so, you'll need to re-download using the versioned URL to get the correct SHA256.

Step 3: Livecheck Strategy

Determine how to check for updates:

Use the Task tool:
- subagent_type: homebrew:livecheck-advisor
- prompt: Recommend a livecheck strategy for <app-name>.
  Download URL: <url>
  Homepage: <homepage>
  Update URL: <appcast-or-feed-url-if-found>
  Current version: <version>

Get the recommended livecheck block.

Step 4: Write the Cask

Synthesize everything into a cask file:

Use the Task tool:
- subagent_type: homebrew:cask-writer
- prompt: Write a cask for <app-name> with this metadata:
  Token: <token>
  Version: <version>
  URL: <download-url>
  SHA256: <checksum> (or :no_check if unversioned URL)
  (If separate binaries per architecture, provide URL and SHA256 for each)
  Name: <display-name>
  Description: <one-line-desc>
  Homepage: <homepage>
  Bundle ID: <bundle-id>
  App bundle: <app-name>.app
  Min macOS: <min-version>
  Auto-updates: <yes/no>
  Livecheck: <livecheck-block>
  Architecture: <arm64/intel/universal, only if not universal>

Note: The zap stanza is added later after running createzap during testing.

Step 5: Testing

Automated Tests

Run the validation script:

${CLAUDE_PLUGIN_ROOT}/scripts/test-cask.sh "<token>"

If tests fail, review the output, fix the cask (often brew style --fix handles style issues), and re-run.

For unversioned URLs: Use --skip-livecheck flag.

Install and Validate

• Install:

   HOMEBREW_NO_INSTALL_FROM_API=1 brew install --cask <token>

• Launch:

   open -a "<App Name>"

• User verification: Ask the user to sign in or set up the app if needed, then confirm when done.

Zap Discovery

• Run createzap (try both app name and bundle ID):

   brew tap nrlquaker/createzap 2>/dev/null || true
   brew createzap "<App Name>"
   brew createzap "<bundle-id>"

• Update the cask - Add the discovered zap paths using the Edit tool. For simple additions you can edit directly; for significant changes, re-invoke the cask-writer agent.

• Uninstall:

   brew uninstall --cask <token>

• Re-run automated tests if zap stanza was added.

Step 6: Submit PR

When ready to submit:

Use the Task tool:
- subagent_type: homebrew:pr-submitter
- prompt: Submit a PR for the <token> cask.
  Version: <version>
  Cask path: <path-to-cask-file>
  All tests passed: yes

Error Recovery

If any step fails:

• The task list shows which steps completed
• You can resume from the failed step
• Agent outputs are preserved in conversation history

Reference Documentation

For detailed guidance, agents can read these docs (at /opt/homebrew/docs/):

• Acceptable-Casks.md - What's allowed
• Cask-Cookbook.md - Stanza reference
• Brew-Livecheck.md - Livecheck strategies
• Adding-Software-to-Homebrew.md - Contribution process

Scripts Location

Scripts are at ${CLAUDE_PLUGIN_ROOT}/scripts/:

• download-checksum.sh <url> [filename] - Download and SHA256
• test-cask.sh <token> [--skip-livecheck] - Run audit/style/livecheck