feat!: compose the federation runtime by default and remove the capability defines

.changeset/composed-runtime-default-major.md

@@ -0,0 +1,19 @@
+---
+'@module-federation/runtime-core': major
+'@module-federation/runtime': major
+'@module-federation/webpack-bundler-runtime': major
+'@module-federation/enhanced': major
+'@module-federation/rspack': major
+'@module-federation/sdk': major
+'@module-federation/node': major
+---
+
+The composed federation runtime is the default and only bootstrap. `ModuleFederationPlugin` now always generates a bootstrap that imports only the runtime parts the build uses, and `experiments.composedRuntime` is removed.
+
+Removed:
+
+- The `FEDERATION_OPTIMIZE_NO_SHARED`, `FEDERATION_OPTIMIZE_NO_REMOTE`, `FEDERATION_OPTIMIZE_NO_SNAPSHOT_PLUGIN`, `FEDERATION_HAS_EXPOSES`, and `FEDERATION_BUILD_IDENTIFIER` defines. The plugins no longer emit them and the runtime no longer reads them. Use `experiments.optimization.disable*` with the plugin, or import the capabilities you need from `@module-federation/runtime/compose` when you bundle the runtime yourself.
+- `__webpack_require__.federation.runtime`. Use `__webpack_require__.federation.instance`, and `instance.platform.loadScriptNode` for the Node loader.
+- The fallback in `@module-federation/node` to `federation.runtime.loadScriptNode`.
+
+A build whose installed runtime packages do not export the composition subpaths now fails with an error that names the minimum runtime version. `ENV_TARGET`, `FEDERATION_ALLOW_NEW_FUNCTION`, and `FEDERATION_DEBUG` are unchanged.

packages/enhanced/src/lib/container/ModuleFederationPlugin.ts

@@ -161,15 +161,13 @@ class ModuleFederationPlugin implements WebpackPluginInstance {
 
     new compiler.webpack.DefinePlugin(definePluginOptions).apply(compiler);
 
-    if (experiments?.composedRuntime) {
-      // DefinePlugin reads its definitions per compilation, after the plan picked a mode.
-      compiler.hooks.compile.tap('ModuleFederationPlugin', () => {
-        if (!composedEntryOf(compiler)) return;
-        for (const key of Object.keys(definePluginOptions)) {
-          if (key !== 'ENV_TARGET') delete definePluginOptions[key];
-        }
-      });
-    }
+    // DefinePlugin reads its definitions per compilation, after the plan picked a mode.
+    compiler.hooks.compile.tap('ModuleFederationPlugin', () => {
+      if (!composedEntryOf(compiler)) return;
+      for (const key of Object.keys(definePluginOptions)) {
+        if (key !== 'ENV_TARGET') delete definePluginOptions[key];
+      }
+    });
   }
 
   /**

packages/enhanced/src/lib/container/runtime/FederationCompositionPlugin.ts

@@ -56,7 +56,7 @@
 export type CoveredByOptions = typeof COVERED_BY_OPTIONS;
 
 const usesSharedContainerPlugin = (compiler: Compiler) =>
   compiler.options.plugins.some(
     (plugin) =>
       typeof plugin === 'object' &&
       plugin !== null &&
@@ -196,10 +196,17 @@
     compilation: Compilation,
     { family, entry, legacyReason }: Outcome,
   ) {
-    if (legacyReason !== undefined) {
+    const { externalRuntime, provideExternalRuntime } =
+      this._options.experiments ?? {};
+    // An externalized runtime is the full runtime by request; the other reasons are worth a warning.
+    if (
+      legacyReason !== undefined &&
+      !externalRuntime &&
+      !provideExternalRuntime
+    ) {
       compilation.warnings.push(
         new WebpackError(
-          `experiments.composedRuntime is set, but this build uses the full federation runtime because ${legacyReason}.`,
+          `This build uses the full federation runtime because ${legacyReason}.`,
         ),
       );
     }

packages/enhanced/src/lib/container/runtime/FederationRuntimePlugin.ts

@@ -531,7 +531,7 @@ class FederationRuntimePlugin {
     // dont run multiple times on every apply()
     if (!onceForCompiler.has(compiler)) {
       const options = this.options;
-      if (options?.experiments?.composedRuntime) {
+      if (options) {
         new FederationCompositionPlugin(options, (composition) => {
           const source = FederationRuntimePlugin.getTemplate(
             compiler,