Add explanatory-output-style plugin to smoke workflows with marketplace URL and MCP config support

.github/workflows/smoke-claude.md

@@ -18,6 +18,8 @@ name: Smoke Claude
 engine:
   id: claude
   max-turns: 15
+plugins:
+  - anthropics/claude-code/plugins/explanatory-output-style
 strict: true
 imports:
   - shared/mood.md

.github/workflows/smoke-copilot.md

@@ -15,6 +15,8 @@ permissions:
   actions: read
 name: Smoke Copilot
 engine: copilot
+plugins:
+  - anthropics/claude-code/plugins/explanatory-output-style
 imports:
   - shared/mood.md
   - shared/gh.md

.github/workflows/smoke-test-tools.md

@@ -12,6 +12,8 @@ permissions:
   pull-requests: read
 name: Agent Container Smoke Test
 engine: copilot
+plugins:
+  - anthropics/claude-code/plugins/explanatory-output-style
 strict: true
 runtimes:
   node:

docs/src/content/docs/reference/frontmatter.md

@@ -107,6 +107,7 @@ Specifies plugins to install before workflow execution. Plugins are installed us
 plugins:
   - github/test-plugin
   - acme/custom-tools
+  - anthropics/claude-code/plugins/explanatory-output-style
 ```
 
 **Object format** (with custom token):
@@ -118,14 +119,20 @@ plugins:
   github-token: ${{ secrets.CUSTOM_PLUGIN_TOKEN }}
 ```
 
+**Plugin identifier formats:**
+- **GitHub repository**: `org/repo` (e.g., `github/test-plugin`)
+- **Sub-plugin path**: `org/repo/path/to/plugin` (e.g., `anthropics/claude-code/plugins/explanatory-output-style`)
+
+**Note**: The plugin format must be compatible with the engine's CLI `plugin install` command. Currently, GitHub repository paths (with optional sub-paths) are the standard format supported across engines.
+
 **Token precedence** for plugin installation (highest to lowest):
 1. Custom `plugins.github-token` from object format
 2. Custom top-level `github-token`
 3. `${{ secrets.GH_AW_PLUGINS_TOKEN }}`
 4. `${{ secrets.GH_AW_GITHUB_TOKEN }}`
 5. `${{ secrets.GITHUB_TOKEN }}` (default)
 
-Each plugin repository must be specified in `org/repo` format. The compiler generates installation steps that run after the engine CLI is installed but before workflow execution begins.
+The compiler generates installation steps that run after the engine CLI is installed but before workflow execution begins.
 
 ### Runtimes (`runtimes:`)
 

pkg/parser/schemas/main_workflow_schema.json

@@ -2483,9 +2483,10 @@
       ]
     },
     "plugins": {
-      "description": "Plugin configuration for installing plugins before workflow execution. Supports array format (list of repos/plugin configs) and object format (repos + custom token).",
+      "description": "Plugin configuration for installing plugins before workflow execution. Supports array format (list of repos/plugin configs) and object format (repos + custom token). Plugin paths can include sub-paths to specific plugins within a repository (e.g., 'anthropics/claude-code/plugins/explanatory-output-style').",
       "examples": [
         ["github/copilot-plugin", "acme/custom-tools"],
+        ["anthropics/claude-code/plugins/explanatory-output-style"],
         [
           "github/simple-plugin",
           {
@@ -2510,8 +2511,8 @@
             "oneOf": [
               {
                 "type": "string",
-                "pattern": "^[a-zA-Z0-9_-]+/[a-zA-Z0-9_-]+$",
-                "description": "Plugin repository slug in the format 'org/repo' (e.g., 'github/example-plugin')"
+                "pattern": "^([a-zA-Z0-9_-]+(/[a-zA-Z0-9_-]+)+|[a-zA-Z0-9_-]+)(@[a-zA-Z0-9_-]+)?$",
+                "description": "Plugin identifier in GitHub repository format: 'org/repo' or 'org/repo/path/to/plugin' (e.g., 'github/example-plugin', 'anthropics/claude-code/plugins/explanatory-output-style'). The pattern allows @marketplace syntax for potential future support, but current engines only support GitHub repository paths."
               },
               {
                 "type": "object",
@@ -2520,8 +2521,8 @@
                 "properties": {
                   "id": {
                     "type": "string",
-                    "pattern": "^[a-zA-Z0-9_-]+/[a-zA-Z0-9_-]+$",
-                    "description": "Plugin repository slug in the format 'org/repo' (e.g., 'github/example-plugin')"
+                    "pattern": "^([a-zA-Z0-9_-]+(/[a-zA-Z0-9_-]+)+|[a-zA-Z0-9_-]+)(@[a-zA-Z0-9_-]+)?$",
+                    "description": "Plugin repository slug in GitHub repository format: 'org/repo' or 'org/repo/path/to/plugin' (e.g., 'github/example-plugin', 'anthropics/claude-code/plugins/explanatory-output-style')"
                   },
                   "mcp": {
                     "type": "object",
@@ -2561,8 +2562,8 @@
                 "oneOf": [
                   {
                     "type": "string",
-                    "pattern": "^[a-zA-Z0-9_-]+/[a-zA-Z0-9_-]+$",
-                    "description": "Plugin repository slug in the format 'org/repo' (e.g., 'github/example-plugin')"
+                    "pattern": "^([a-zA-Z0-9_-]+(/[a-zA-Z0-9_-]+)+|[a-zA-Z0-9_-]+)(@[a-zA-Z0-9_-]+)?$",
+                    "description": "Plugin identifier in GitHub repository format: 'org/repo' or 'org/repo/path/to/plugin' (e.g., 'github/example-plugin', 'anthropics/claude-code/plugins/explanatory-output-style'). The pattern allows @marketplace syntax for potential future support, but current engines only support GitHub repository paths."
                   },
                   {
                     "type": "object",
@@ -2571,8 +2572,8 @@
                     "properties": {
                       "id": {
                         "type": "string",
-                        "pattern": "^[a-zA-Z0-9_-]+/[a-zA-Z0-9_-]+$",
-                        "description": "Plugin repository slug in the format 'org/repo' (e.g., 'github/example-plugin')"
+                        "pattern": "^([a-zA-Z0-9_-]+(/[a-zA-Z0-9_-]+)+|[a-zA-Z0-9_-]+)(@[a-zA-Z0-9_-]+)?$",
+                        "description": "Plugin repository slug in the format 'org/repo', 'org/repo/path/to/plugin', 'plugin-name@marketplace', or 'org/repo@marketplace' (e.g., 'github/example-plugin', 'anthropics/claude-code/plugins/explanatory-output-style')"
                       },
                       "mcp": {
                         "type": "object",

pkg/workflow/agentic_engine.go

@@ -125,6 +125,10 @@ type CapabilityProvider interface {
 	// SupportsFirewall returns true if this engine supports network firewalling/sandboxing
 	// When true, the engine can enforce network restrictions defined in the workflow
 	SupportsFirewall() bool
+
+	// SupportsPlugins returns true if this engine supports plugin installation
+	// When true, plugins can be installed using the engine's plugin install command
+	SupportsPlugins() bool
 }
 
 // WorkflowExecutor handles workflow compilation and execution
@@ -199,6 +203,7 @@ type BaseEngine struct {
 	supportsWebFetch       bool
 	supportsWebSearch      bool
 	supportsFirewall       bool
+	supportsPlugins        bool
 }
 
 func (e *BaseEngine) GetID() string {
@@ -241,6 +246,10 @@ func (e *BaseEngine) SupportsFirewall() bool {
 	return e.supportsFirewall
 }
 
+func (e *BaseEngine) SupportsPlugins() bool {
+	return e.supportsPlugins
+}
+
 // GetDeclaredOutputFiles returns an empty list by default (engines can override)
 func (e *BaseEngine) GetDeclaredOutputFiles() []string {
 	return []string{}

pkg/workflow/claude_engine.go

@@ -25,11 +25,12 @@ func NewClaudeEngine() *ClaudeEngine {
 			description:            "Uses Claude Code with full MCP tool support and allow-listing",
 			experimental:           false,
 			supportsToolsAllowlist: true,
-			supportsHTTPTransport:  true, // Claude supports both stdio and HTTP transport
-			supportsMaxTurns:       true, // Claude supports max-turns feature
-			supportsWebFetch:       true, // Claude has built-in WebFetch support
-			supportsWebSearch:      true, // Claude has built-in WebSearch support
-			supportsFirewall:       true, // Claude supports network firewalling via AWF
+			supportsHTTPTransport:  true,  // Claude supports both stdio and HTTP transport
+			supportsMaxTurns:       true,  // Claude supports max-turns feature
+			supportsWebFetch:       true,  // Claude has built-in WebFetch support
+			supportsWebSearch:      true,  // Claude has built-in WebSearch support
+			supportsFirewall:       true,  // Claude supports network firewalling via AWF
+			supportsPlugins:        true,  // Claude supports plugin installation
 		},
 	}
 }