diff --git a/.changeset/moody-snakes-study.md b/.changeset/moody-snakes-study.md
new file mode 100644
index 0000000000..c5758897ed
--- /dev/null
+++ b/.changeset/moody-snakes-study.md
@@ -0,0 +1,10 @@
+---
+"@lynx-js/rspeedy": patch
+"@lynx-js/template-webpack-plugin": patch
+---
+
+feat: opt-in the web platform's new binary output format
+
+Introduce a new flag to enable the new binary output format.
+
+Currently it's an internal-use-only flag that will be removed in the future; set the corresponding environment variable to 'true' to enable it.
diff --git a/packages/webpack/template-webpack-plugin/package.json b/packages/webpack/template-webpack-plugin/package.json
index 84e413db4c..890e31db88 100644
--- a/packages/webpack/template-webpack-plugin/package.json
+++ b/packages/webpack/template-webpack-plugin/package.json
@@ -38,6 +38,7 @@
   "dependencies": {
     "@lynx-js/css-serializer": "workspace:*",
     "@lynx-js/tasm": "0.0.20",
+    "@lynx-js/web-core-wasm": "workspace:*",
     "@lynx-js/webpack-runtime-globals": "workspace:^",
     "@rspack/lite-tapable": "1.1.0",
     "css-tree": "^3.1.0",
@@ -46,7 +47,6 @@
   "devDependencies": {
     "@lynx-js/test-tools": "workspace:*",
     "@lynx-js/vitest-setup": "workspace:*",
-    "@lynx-js/web-core-wasm": "workspace:*",
     "@microsoft/api-extractor": "catalog:",
     "@types/css-tree": "^2.3.11",
     "@types/object.groupby": "^1.0.4",
diff --git a/packages/webpack/template-webpack-plugin/src/WebEncodePlugin.ts b/packages/webpack/template-webpack-plugin/src/WebEncodePlugin.ts
index 9eacd47caa..eca646e4b3 100644
--- a/packages/webpack/template-webpack-plugin/src/WebEncodePlugin.ts
+++ b/packages/webpack/template-webpack-plugin/src/WebEncodePlugin.ts
@@ -102,22 +102,15 @@ export class WebEncodePlugin {
             customSections: encodeOptions.customSections ?? {},
             elementTemplates: encodeOptions['elementTemplates'] ?? {},
           };
-          const isExperimentalWebBinary = !!process
+          const isExperimentalWebBinary = process
             .env['EXPERIMENTAL_USE_WEB_BINARY_TEMPLATE'];
-          if (isExperimentalWebBinary) {
-            const { encode } = await import('@lynx-js/web-core-wasm/encode')
-              .catch(
-                () => {
-                  throw new Error(
-                    `FLAG EXPERIMENTAL_USE_WEB_BINARY_TEMPLATE IS INTERNAL USED ONLY`,
-                  );
-                },
-              );
+          if (isExperimentalWebBinary === 'true') {
+            const { encode } = await import('@lynx-js/web-core-wasm/encode');
             return {
               buffer: Buffer.from(encode(tasmJSONInfo as TasmJSONInfo)),
               debugInfo: '',
             };
-          } else {
+          } else if (isExperimentalWebBinary == null /*undefined or null */) {
             return {
               buffer: Buffer.from(
                 JSON.stringify({
@@ -133,6 +126,11 @@ export class WebEncodePlugin {
               ),
               debugInfo: '',
             };
+          } else {
+            // only allow 'true' or undefined/null
+            throw new Error(
+              `Unknown value of EXPERIMENTAL_USE_WEB_BINARY_TEMPLATE: ${isExperimentalWebBinary}. Expecting "true" or undefined.`,
+            );
           }
         });
       },
diff --git a/pnpm-lock.yaml b/pnpm-lock.yaml
index cacbb74b81..2e20085a6a 100644
--- a/pnpm-lock.yaml
+++ b/pnpm-lock.yaml
@@ -1638,6 +1638,9 @@ importers:
       '@lynx-js/tasm':
         specifier: 0.0.20
         version: 0.0.20
+      '@lynx-js/web-core-wasm':
+        specifier: workspace:*
+        version: link:../../web-platform/web-core-wasm
       '@lynx-js/webpack-runtime-globals':
         specifier: workspace:^
         version: link:../webpack-runtime-globals
@@ -1657,9 +1660,6 @@ importers:
       '@lynx-js/vitest-setup':
         specifier: workspace:*
         version: link:../../tools/vitest-setup
-      '@lynx-js/web-core-wasm':
-        specifier: workspace:*
-        version: link:../../web-platform/web-core-wasm
       '@microsoft/api-extractor':
         specifier: 'catalog:'
         version: 7.57.6(@types/node@24.10.13)