[WC-3105]: Mendix Pluggable MCP

package.json

@@ -13,6 +13,7 @@
         "create-gh-release": "turbo run create-gh-release --concurrency 1",
         "create-translation": "turbo run create-translation",
         "postinstall": "turbo run agent-rules",
+        "start:mcp": "pnpm --filter pluggable-widgets-mcp run start",
         "lint": "turbo run lint --continue --concurrency 1",
         "prepare": "husky install",
         "prepare-release": "pnpm --filter @mendix/automation-utils run prepare-release",

packages/pluggable-widgets-mcp/.gitignore

@@ -0,0 +1,3 @@
+dist/
+generations/
+node_modules/

packages/pluggable-widgets-mcp/.prettierrc.cjs

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+module.exports = require("@mendix/prettier-config-web-widgets");

packages/pluggable-widgets-mcp/AGENTS.md

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+# Pluggable Widgets MCP Server
+
+MCP server enabling AI assistants to scaffold and manage Mendix pluggable widgets via STDIO (default) or HTTP transport.
+
+## Quick Reference
+
+```bash
+pnpm dev          # Development with hot reload
+pnpm build        # TypeScript compilation + path alias resolution
+pnpm start        # Build and run (STDIO mode, default)
+pnpm start:http   # Build and run (HTTP mode, port 3100)
+pnpm lint         # ESLint check
+```
+
+## Project Structure
+
+```
+src/
+├── index.ts          # Entry point - transport mode selection
+├── config.ts         # Server configuration and constants
+├── security/         # Path traversal & extension validation
+├── server/           # HTTP and STDIO transport setup
+├── resources/        # MCP resources (guidelines)
+├── generators/       # XML and TSX code generators
+└── tools/            # MCP tool implementations
+```
+
+## Adding Tools
+
+1. Create `src/tools/my-feature.tools.ts`:
+
+```typescript
+import type { McpServer } from "@modelcontextprotocol/sdk/server/mcp.js";
+import { z } from "zod";
+
+export function registerMyTools(server: McpServer): void {
+    server.tool(
+        "my-tool",
+        "Description shown to LLM",
+        z.object({ param: z.string().describe("Parameter description") }),
+        async ({ param }) => ({
+            content: [{ type: "text", text: "Success" }]
+        })
+    );
+}
+```
+
+2. Register in `src/tools/index.ts`:
+
+```typescript
+import { registerMyTools } from "./my-feature.tools";
+
+export function registerAllTools(server: McpServer): void {
+    // ... existing registrations
+    registerMyTools(server);
+}
+```
+
+## Code Patterns
+
+- **Imports**: Use `@/` path alias for absolute imports from `src/`
+- **Schemas**: All tool inputs require Zod schemas
+- **Errors**: Use `createErrorResponse()` from `@/tools/utils/response`
+- **Long operations**: Use `ProgressTracker` from `@/tools/utils/progress-tracker`
+
+## Notification Behavior (Important for AI Agents)
+
+When using this MCP server, understand where different types of output appear:
+
+| Output Type                | Visibility                 | Purpose                                                 |
+| -------------------------- | -------------------------- | ------------------------------------------------------- |
+| **Tool Results**           | ✅ Visible in conversation | Final outcomes, structured data, success/error messages |
+| **Progress Notifications** | ❌ Not in conversation     | Client UI indicators only (spinners, progress bars)     |
+| **Log Messages**           | ❌ Not in conversation     | Debug console/MCP Inspector only                        |
+
+**Key Implications for AI Agents:**
+
+1. **Don't expect intermediate progress in chat**: Long operations (scaffolding, building) will show results only when complete. The conversation won't contain step-by-step progress updates.
+
+2. **Tool results are authoritative**: Only tool result content appears in the conversation history. Use this for:
+
+    - Success confirmations with file paths
+    - Structured error messages with suggestions
+    - Any information the AI needs to continue the workflow
+
+3. **Progress tracking is for humans**: `sendProgress()` and `sendLogMessage()` are for human observers using MCP Inspector or UI indicators, not for AI decision-making.
+
+4. **When debugging**:
+    - If operations seem to "hang", check MCP Inspector's Notifications/Logs panels
+    - Progress notifications confirm the server is working, even if the chat is quiet
+    - This is per MCP specification, not a bug
+
+**Example Workflow:**
+
+```typescript
+// ❌ This progress won't appear in AI's context
+await sendProgress(context, 50, "Scaffolding widget...");
+
+// ✅ This result WILL appear in AI's context
+return createToolResponse(`Widget created at ${widgetPath}`);
+```
+
+## Testing
+
+```bash
+npx @modelcontextprotocol/inspector node dist/index.js
+```
+
+## Security
+
+**Read before implementing file operations**: [docs/agent/security.md](docs/agent/security.md)
+
+All file operation tools must use `validateFilePath()` from `@/security` to prevent path traversal attacks.

packages/pluggable-widgets-mcp/CHANGELOG.md

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+# Changelog
+
+All notable changes to this MCP server will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [Unreleased]
+
+### Added
+
+- We introduce pluggable-widgets-mcp.