feat: Expose __DC_CONTROLLERS__ for MCP integration into devtools

Author: ntucker

.changeset/expose-controllers-devtools.md

@@ -0,0 +1,9 @@
+---
+'@data-client/core': patch
+'@data-client/react': patch
+'@data-client/vue': patch
+---
+
+Add `globalThis.__DC_CONTROLLERS__` Map in dev mode for programmatic store access from browser DevTools MCP, React Native debuggers, and other development tooling.
+
+Each [DataProvider](/docs/api/DataProvider) registers its [Controller](/docs/api/Controller) keyed by the devtools connection name, supporting multiple providers on the same page.

docs/core/api/DevToolsManager.md

@@ -107,6 +107,30 @@ const managers = getDefaultManagers({
 });
 ```
 
+## Programmatic store access {#controllers}
+
+In development mode, `DevToolsManager` registers each [Controller](/docs/api/Controller) on
+`globalThis.__DC_CONTROLLERS__` — a `Map` keyed by the devtools connection name. This works
+in browsers, React Native, and Node.
+
+```js title="Browser DevTools console"
+// List all registered providers
+__DC_CONTROLLERS__.keys();
+
+// Get state from the first provider
+__DC_CONTROLLERS__.values().next().value.getState();
+
+// Get state by name
+__DC_CONTROLLERS__.get('Data Client: My App').getState();
+```
+
+This is useful for AI coding assistants using the [Chrome DevTools MCP](https://developer.chrome.com/blog/chrome-devtools-mcp)
+or [Expo MCP](https://docs.expo.dev/eas/ai/mcp/) to programmatically inspect and interact
+with the store. Each [DataProvider](/docs/api/DataProvider) registers independently, so
+multiple providers on the same page are fully supported.
+
+Controllers are removed from the map when `cleanup()` is called.
+
 ## More info
 
 Using this Manager allows in browser [debugging and store inspection](../getting-started/debugging.md).

packages/core/src/manager/DevtoolsManager.ts

@@ -94,20 +94,21 @@ export default class DevToolsManager implements Manager {
   protected actions: [ActionTypes, State<unknown>][] = [];
   declare protected controller: Controller;
   declare skipLogging?: (action: ActionTypes) => boolean;
+  declare protected devtoolsName: string;
   maxBufferLength = 100;
 
   constructor(
     config?: DevToolsConfig,
     skipLogging?: (action: ActionTypes) => boolean,
   ) {
     /* istanbul ignore next */
+    const options = { ...DEFAULT_CONFIG, ...config };
+    this.devtoolsName =
+      options.name ?? `Data Client: ${globalThis.document?.title}`;
     this.devTools =
       typeof window !== 'undefined' &&
       (window as any).__REDUX_DEVTOOLS_EXTENSION__ &&
-      (window as any).__REDUX_DEVTOOLS_EXTENSION__.connect({
-        ...DEFAULT_CONFIG,
-        ...config,
-      });
+      (window as any).__REDUX_DEVTOOLS_EXTENSION__.connect(options);
     // we cut it in half so we should double so we don't lose
     if (config?.maxAge) this.maxBufferLength = config.maxAge * 2;
     if (skipLogging) this.skipLogging = skipLogging;
@@ -118,8 +119,8 @@ export default class DevToolsManager implements Manager {
     /* istanbul ignore next */
     if (process.env.NODE_ENV !== 'production') {
       this.prototype.middleware = function (controller) {
-        if (!this.devTools) return next => action => next(action);
         this.controller = controller;
+        if (!this.devTools) return next => action => next(action);
         const reducer = createReducer(controller as any);
         let state = controller.getState();
         return next => action => {
@@ -158,6 +159,12 @@ export default class DevToolsManager implements Manager {
 
   /** Called when initial state is ready */
   init(state: State<any>) {
+    if (process.env.NODE_ENV !== 'production') {
+      ((globalThis as any).__DC_CONTROLLERS__ ??= new Map()).set(
+        this.devtoolsName,
+        this.controller,
+      );
+    }
     if (process.env.NODE_ENV !== 'production' && this.devTools) {
       this.devTools.init(state);
       this.devTools.subscribe((msg: any) => {
@@ -186,5 +193,9 @@ export default class DevToolsManager implements Manager {
   }
 
   /** Ensures all subscriptions are cleaned up. */
-  cleanup() {}
+  cleanup() {
+    if (process.env.NODE_ENV !== 'production') {
+      (globalThis as any).__DC_CONTROLLERS__?.delete(this.devtoolsName);
+    }
+  }
 }

website/blog/2026-01-19-v0.16-release-announcement.md

@@ -19,6 +19,7 @@ import { parallelFetchFixtures } from '@site/src/fixtures/post-comments';
 **Performance:**
 
 **Other Improvements:**
+- [DevToolsManager](/docs/api/DevToolsManager#controllers) exposes `globalThis.__DC_CONTROLLERS__` in dev mode for programmatic store access from [Chrome DevTools MCP](https://developer.chrome.com/blog/chrome-devtools-mcp) and [Expo MCP](https://docs.expo.dev/eas/ai/mcp/)
 - Remove misleading 'Uncaught Suspense' warning during Next.js SSR
 - Fix `sideEffect: false` type being lost with `method: 'POST'` in [RestEndpoint](/rest/api/RestEndpoint)