markus41/devstudio

Plugin Dev Studio Workflow

Comprehensive development environment for building, testing, and validating Claude Code plugins with hot-reload support.

When to Use This Skill

Activate this skill when:

• Developing a new plugin and need rapid iteration with live validation
• Debugging plugin manifest or resource file issues
• Visualizing plugin dependency graphs for architecture review
• Building regression test suites for plugin commands
• Preparing a plugin for publication to a registry

Architecture Overview

The Dev Studio consists of four core subsystems:

+------------------+     +---------------+     +-------------------+
|   FileWatcher    | --> |  HotReloader  | --> | Resource Registry |
| (FNV-1a hashing) |     | (Validation)  |     | (Live state)      |
+------------------+     +---------------+     +-------------------+
                                |
                                v
                     +--------------------+
                     | Console Reporter   |
                     | (file:line errors) |
                     +--------------------+

+-------------------+     +---------------------------+
| PluginPlayground  |     | DependencyGraphRenderer   |
| (Record/Replay)   |     | (ASCII + Mermaid output)  |
+-------------------+     +---------------------------+

FileWatcher

Monitors a plugin directory for file changes using filesystem watchers with content-hash-based change detection.

Key design decisions:

• Uses FNV-1a (32-bit) hashing for speed — non-cryptographic, but extremely fast for small files
• Only triggers reload when file content actually changed (ignores timestamp-only updates)
• Debounces rapid changes with a 100ms window to batch editor save operations
• Classifies files by resource type (command, skill, agent, config, source)

HotReloader

Processes file changes and maintains a live resource registry.

On each change:

1. If manifest changed: re-read, re-validate JSON structure and required fields
2. If markdown resource changed: re-lint frontmatter (YAML validity, required fields)
3. Update resource registry: add new resources, update modified ones, remove deleted ones
4. Report validation results with file:line references for inline error display

PluginPlayground

Isolated execution context for testing plugin commands.

Record-replay workflow:

1. Register mock capabilities for external dependencies
2. Execute commands and record full input/output pairs as fixtures
3. Save fixtures to tests/fixtures/ as JSON
4. Replay fixtures in CI to detect regressions

DependencyGraphRenderer

Builds and renders plugin dependency graphs.

Two output formats:

• ASCII tree: Uses Unicode box-drawing characters for terminal display
• Mermaid diagram: Pasteable into GitHub markdown, Notion, or Mermaid Live Editor

Development Workflow

Phase 1: Scaffold and Configure

# Create plugin structure
mkdir -p my-plugin/{commands,skills,agents,config,src,tests/fixtures}
mkdir -p my-plugin/.claude-plugin

# Create minimal manifest
cat > my-plugin/.claude-plugin/plugin.json << 'EOF'
{
  "name": "my-plugin",
  "version": "0.1.0",
  "description": "My new plugin",
  "contextEntry": "CONTEXT.md",
  "capabilities": {
    "provides": ["my-capability"],
    "requires": []
  }
}
EOF

# Create required operator runbook
cat > my-plugin/CLAUDE.md << 'EOF'
# My Plugin Guide

## Purpose
- Brief description of plugin intent.

## Supported Commands
- command-name (commands/command-name.md)

## Prohibited Actions
- List destructive or out-of-scope operations.

## Required Validation Checks
- npm run check:plugin-context
- npm run check:plugin-schema

## Context Budget
1. CONTEXT_SUMMARY.md
2. commands/index (or commands/)
3. README.md and only task-relevant deep docs

## Escalation Path
- Describe who reviews risky or blocking changes.
EOF

# Create operator context entrypoint (keep concise)
cat > my-plugin/CONTEXT.md << 'EOF'
# my-plugin Context

## Purpose
One-paragraph operator summary.

## Key Commands
- /my:command

## Agent Inventory
- my-agent

## Load Deeper Docs When
- You need implementation details or architecture rationale.
EOF

Phase 2: Develop with Hot-Reload

# Start the dev server with file watching
/mp:dev serve ./my-plugin --watch

The dev server will:

• Validate the manifest on startup
• Discover and register all commands, skills, and agents
• Watch for file changes and re-validate on save
• Show inline errors with file:line references

Phase 3: Test in Playground

# Launch interactive playground
/mp:dev playground ./my-plugin

# In the playground:
# > run /my:command "test input"
# > save my-test-case
# > log

Phase 4: Visualize Dependencies

# Show dependency graph
/mp:dev graph ./my-plugin

Review the ASCII tree to verify:

• All capability declarations are correct
• Inter-resource dependencies are properly linked
• No circular dependencies exist

Phase 5: Validate Before Publish

# Full validation suite
/mp:dev validate ./my-plugin

Fix all errors before publishing. Warnings are advisory but should be addressed.

Phase 6: Regression Testing

# List saved fixtures
/mp:dev fixture list

# Replay a specific fixture
/mp:dev fixture replay my-test-case

Validation Rules

Manifest Validation (plugin.json)

| Rule | Severity | Description | |------|----------|-------------| | Valid JSON | error | File must be parseable JSON | | name field | error | Must be a non-empty string | | version field | error | Must be a non-empty string | | description field | error | Must be a non-empty string | | contextEntry field | error | Must reference CONTEXT.md or PLUGIN_CONTEXT.md | | CLAUDE.md present | error | Plugin root must include CLAUDE.md runbook | | capabilities present | warning | Plugin should declare capabilities | | capabilities.provides is array | error | Must be an array of strings | | capabilities.requires is array | error | Must be an array of strings |

Command/Skill Validation (.md files)

| Rule | Severity | Description | |------|----------|-------------| | Has frontmatter | error | Must start with --- | | Frontmatter closed | error | Must have closing --- | | name in frontmatter | error | Commands and skills must have a name | | description in frontmatter | warning | Should have a description | | Top-level heading | info | Should have # Title after frontmatter |

File Structure

plugin-root/
  .claude-plugin/
    plugin.json          # Plugin manifest (validated by HotReloader)
  CLAUDE.md              # Required operator runbook and context budget
  CONTEXT.md             # Minimal operator context entrypoint
  commands/
    *.md                 # Slash commands (validated for frontmatter)
  skills/
    */SKILL.md           # Skills (validated for frontmatter)
  agents/
    *.md                 # Agents (validated for frontmatter)
  config/
    *.json               # Configuration files
  src/
    devstudio/
      types.ts           # Type definitions
      server.ts          # FileWatcher, HotReloader, Playground, GraphRenderer
  tests/
    fixtures/
      *.json             # Recorded test fixtures (from playground)

Troubleshooting

Common Issues

"Plugin manifest not found"

• Ensure .claude-plugin/plugin.json exists in the plugin root
• Check that the path passed to /mp:dev is correct

"Missing YAML frontmatter"

• Markdown resource files must start with --- on the first line
• Frontmatter must be closed with a second --- line

"Content hash unchanged but file was modified"

• The FileWatcher uses content hashing, not timestamps
• If only whitespace changed, verify the hash actually differs
• The FNV-1a hash has a very low (but non-zero) collision rate for small changes

"Fixture replay fails with empty output"

• Playground execution is a simulation; real command execution requires the Claude runtime
• Record the actual output using recordOutput() after command execution

Source Files

• Types: src/devstudio/types.ts
• Implementation: src/devstudio/server.ts
• Command: commands/dev.md
• This skill: skills/devstudio/SKILL.md

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Skill version: 1.0 Module: dev-studio (marketplace-pro plugin)