From e51fedabd001a55757b50a2ae1bd13a6893a2d6d Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 01:53:10 +0000
Subject: [PATCH 01/17] [SPLIT_MODULE] Make getWasmImports return Proxy (NFC)

When `SPLIT_MODULE` is set, this makes the `imports` object returned by
`getWasmImports` itself a Proxy, which redirects property requests
starting with `placeholder` to an inner `splitModuleProxyHandler` that
processes the second module loading, and process all other property
requests to the original `imports` object itself.

This is a prepration to add multi-split loading functionality to the JS
runtime. In the multi-split mode, we don't have a single seconday module
`[modulename].deferred.wasm`, but instead multiple secondary modules. We
plan to have multiple placeholder namespace (e.g., `placeholder_2`,
`placeholder_3`, ...) that match those multiple files, and this can't be
hardcoded with one `placeholder` string as we currently do, so having
the `imports` object itself as a `Proxy` provides us flexibility to
handle multiple placeholder namespaces and load correct modules later.
---
 src/preamble.js | 50 ++++++++++++++++++++++++++++++-------------------
 1 file changed, 31 insertions(+), 19 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 89f10bb379b38..3dd5ec9689184 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -487,27 +487,37 @@ async function getWasmBinary(binaryFile) {
 
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
-var splitModuleProxyHandler = {
+var wasmImportsProxyHandler = {
   get(target, prop, receiver) {
-    return (...args) => {
+    if (prop.startsWith('placeholder')) {
+      const moduleName = prop;
+      var splitModuleProxyHandler = {
+        get(target, prop, receiver) {
+          return (...args) => {
 #if ASYNCIFY == 2
-      throw new Error('Placeholder function "' + prop + '" should not be called when using JSPI.');
+            throw new Error('Placeholder function "' + prop + '" should not be called when using JSPI.');
 #else
-      err(`placeholder function called: ${prop}`);
-      var imports = {'primary': wasmExports};
-      // Replace '.wasm' suffix with '.deferred.wasm'.
-      var deferred = wasmBinaryFile.slice(0, -5) + '.deferred.wasm'
-      loadSplitModule(deferred, imports, prop);
-      err('instantiated deferred module, continuing');
+            // TODO: Implement multi-split module loading
+            err(`placeholder function called: ${prop}`);
+            var imports = {'primary': wasmExports};
+            // Replace '.wasm' suffix with '.deferred.wasm'.
+            var deferred = wasmBinaryFile.slice(0, -5) + '.deferred.wasm'
+            loadSplitModule(deferred, imports, prop);
+            err('instantiated deferred module, continuing');
 #if RELOCATABLE
-      // When the table is dynamically laid out, the placeholder functions names
-      // are offsets from the table base. In the main module, the table base is
-      // always 1.
-      prop = 1 + parseInt(prop);
+            // When the table is dynamically laid out, the placeholder functions names
+            // are offsets from the table base. In the main module, the table base is
+            // always 1.
+            prop = 1 + parseInt(prop);
 #endif
-      return wasmTable.get({{{ toIndexType('prop') }}})(...args);
+            return wasmTable.get({{{ toIndexType('prop') }}})(...args);
 #endif
+          }
+        }
+      };
+      return new Proxy({}, splitModuleProxyHandler);
     }
+    return target[prop];
   }
 };
 #endif
@@ -633,6 +643,7 @@ async function instantiateAsync(binary, binaryFile, imports) {
 #endif // SOURCE_PHASE_IMPORTS
 
 #if !WASM_ESM_INTEGRATION
+
 function getWasmImports() {
 #if PTHREADS || WASM_WORKERS || (IMPORTED_MEMORY && MODULARIZE == 'instance')
   assignWasmImports();
@@ -653,21 +664,22 @@ function getWasmImports() {
 #endif
 #endif
   // prepare imports
-  return {
+  var imports = {
 #if MINIFY_WASM_IMPORTED_MODULES
     'a': wasmImports,
 #else // MINIFY_WASM_IMPORTED_MODULES
     'env': wasmImports,
     '{{{ WASI_MODULE_NAME }}}': wasmImports,
 #endif // MINIFY_WASM_IMPORTED_MODULES
-#if SPLIT_MODULE
-    'placeholder': new Proxy({}, splitModuleProxyHandler),
-#endif
 #if RELOCATABLE
     'GOT.mem': new Proxy(wasmImports, GOTHandler),
     'GOT.func': new Proxy(wasmImports, GOTHandler),
 #endif
-  }
+  };
+#if SPLIT_MODULE
+  imports = new Proxy(imports, wasmImportsProxyHandler);
+#endif
+  return imports;
 }
 
 // Create the wasm instance.

From 470fcfb52034fa0bdf29472fcc9325696710aecb Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 05:58:07 +0000
Subject: [PATCH 02/17] Automatic rebaseline of codesize expectations. NFC

This is an automatic change generated by tools/maint/rebaseline_tests.py.

The following (7) test expectation files were updated by
running the tests with `--rebaseline`:

```
codesize/test_codesize_cxx_wasmfs.json: 176780 => 176780 [+0 bytes / +0.00%]
test/codesize/test_codesize_file_preload.expected.js updated
codesize/test_codesize_files_wasmfs.json: 55683 => 55683 [+0 bytes / +0.00%]
codesize/test_codesize_hello_O0.json: 39197 => 39189 [-8 bytes / -0.02%]
codesize/test_codesize_hello_dylink_all.json: 843553 => 843559 [+6 bytes / +0.00%]
test/codesize/test_codesize_minimal_O0.expected.js updated
codesize/test_unoptimized_code_size.json: 180236 => 180290 [+54 bytes / +0.03%]

Average change: +0.00% (-0.02% - +0.03%)
```
---
 test/codesize/test_codesize_cxx_wasmfs.json   |  4 +--
 .../test_codesize_file_preload.expected.js    |  3 +-
 test/codesize/test_codesize_files_wasmfs.json |  4 +--
 test/codesize/test_codesize_hello_O0.json     |  8 +++---
 .../test_codesize_hello_dylink_all.json       |  4 +--
 .../test_codesize_minimal_O0.expected.js      |  5 ++--
 test/codesize/test_unoptimized_code_size.json | 28 +++++++++----------
 7 files changed, 29 insertions(+), 27 deletions(-)

diff --git a/test/codesize/test_codesize_cxx_wasmfs.json b/test/codesize/test_codesize_cxx_wasmfs.json
index 3b2be1f142d31..3021f01f12876 100644
--- a/test/codesize/test_codesize_cxx_wasmfs.json
+++ b/test/codesize/test_codesize_cxx_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 7059,
   "a.out.js.gz": 3330,
   "a.out.nodebug.wasm": 169721,
-  "a.out.nodebug.wasm.gz": 62983,
+  "a.out.nodebug.wasm.gz": 62981,
   "total": 176780,
-  "total_gz": 66313,
+  "total_gz": 66311,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_file_preload.expected.js b/test/codesize/test_codesize_file_preload.expected.js
index 6a54d91bcc8e2..c4e879be679a1 100644
--- a/test/codesize/test_codesize_file_preload.expected.js
+++ b/test/codesize/test_codesize_file_preload.expected.js
@@ -447,9 +447,10 @@ async function instantiateAsync(binary, binaryFile, imports) {
 
 function getWasmImports() {
   // prepare imports
-  return {
+  var imports = {
     "a": wasmImports
   };
+  return imports;
 }
 
 // Create the wasm instance.
diff --git a/test/codesize/test_codesize_files_wasmfs.json b/test/codesize/test_codesize_files_wasmfs.json
index 5497bd2b1ee39..fb687e208a871 100644
--- a/test/codesize/test_codesize_files_wasmfs.json
+++ b/test/codesize/test_codesize_files_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 5465,
   "a.out.js.gz": 2576,
   "a.out.nodebug.wasm": 50218,
-  "a.out.nodebug.wasm.gz": 18082,
+  "a.out.nodebug.wasm.gz": 18086,
   "total": 55683,
-  "total_gz": 20658,
+  "total_gz": 20662,
   "sent": [
     "a (emscripten_date_now)",
     "b (emscripten_err)",
diff --git a/test/codesize/test_codesize_hello_O0.json b/test/codesize/test_codesize_hello_O0.json
index 3586b686893df..701ff3b943459 100644
--- a/test/codesize/test_codesize_hello_O0.json
+++ b/test/codesize/test_codesize_hello_O0.json
@@ -1,10 +1,10 @@
 {
   "a.out.js": 24070,
   "a.out.js.gz": 8666,
-  "a.out.nodebug.wasm": 15127,
-  "a.out.nodebug.wasm.gz": 7450,
-  "total": 39197,
-  "total_gz": 16116,
+  "a.out.nodebug.wasm": 15119,
+  "a.out.nodebug.wasm.gz": 7444,
+  "total": 39189,
+  "total_gz": 16110,
   "sent": [
     "fd_write"
   ],
diff --git a/test/codesize/test_codesize_hello_dylink_all.json b/test/codesize/test_codesize_hello_dylink_all.json
index aa27e63c7d228..05ebe029c71ac 100644
--- a/test/codesize/test_codesize_hello_dylink_all.json
+++ b/test/codesize/test_codesize_hello_dylink_all.json
@@ -1,7 +1,7 @@
 {
   "a.out.js": 245829,
-  "a.out.nodebug.wasm": 597724,
-  "total": 843553,
+  "a.out.nodebug.wasm": 597730,
+  "total": 843559,
   "sent": [
     "IMG_Init",
     "IMG_Load",
diff --git a/test/codesize/test_codesize_minimal_O0.expected.js b/test/codesize/test_codesize_minimal_O0.expected.js
index cd9adf6366115..52577c13e659f 100644
--- a/test/codesize/test_codesize_minimal_O0.expected.js
+++ b/test/codesize/test_codesize_minimal_O0.expected.js
@@ -658,10 +658,11 @@ async function instantiateAsync(binary, binaryFile, imports) {
 
 function getWasmImports() {
   // prepare imports
-  return {
+  var imports = {
     'env': wasmImports,
     'wasi_snapshot_preview1': wasmImports,
-  }
+  };
+  return imports;
 }
 
 // Create the wasm instance.
diff --git a/test/codesize/test_unoptimized_code_size.json b/test/codesize/test_unoptimized_code_size.json
index d8c830a2899cb..ae60057550c37 100644
--- a/test/codesize/test_unoptimized_code_size.json
+++ b/test/codesize/test_unoptimized_code_size.json
@@ -1,16 +1,16 @@
 {
-  "hello_world.js": 56566,
-  "hello_world.js.gz": 17601,
-  "hello_world.wasm": 15127,
-  "hello_world.wasm.gz": 7450,
-  "no_asserts.js": 26608,
-  "no_asserts.js.gz": 8874,
-  "no_asserts.wasm": 12227,
-  "no_asserts.wasm.gz": 6010,
-  "strict.js": 54581,
-  "strict.js.gz": 16947,
-  "strict.wasm": 15127,
-  "strict.wasm.gz": 7447,
-  "total": 180236,
-  "total_gz": 64329
+  "hello_world.js": 56592,
+  "hello_world.js.gz": 17608,
+  "hello_world.wasm": 15119,
+  "hello_world.wasm.gz": 7444,
+  "no_asserts.js": 26634,
+  "no_asserts.js.gz": 8883,
+  "no_asserts.wasm": 12219,
+  "no_asserts.wasm.gz": 6005,
+  "strict.js": 54607,
+  "strict.js.gz": 16955,
+  "strict.wasm": 15119,
+  "strict.wasm.gz": 7442,
+  "total": 180290,
+  "total_gz": 64337
 }

From 6a30a500744cdbae804a7ceff78c1015d8966de4 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 06:18:06 +0000
Subject: [PATCH 03/17] Address a comment

---
 src/preamble.js | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 3dd5ec9689184..4d38d912aa456 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -488,9 +488,8 @@ async function getWasmBinary(binaryFile) {
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
 var wasmImportsProxyHandler = {
-  get(target, prop, receiver) {
-    if (prop.startsWith('placeholder')) {
-      const moduleName = prop;
+  get(target, namespace, receiver) {
+    if (namespace.startsWith('placeholder')) {
       var splitModuleProxyHandler = {
         get(target, prop, receiver) {
           return (...args) => {
@@ -517,7 +516,7 @@ var wasmImportsProxyHandler = {
       };
       return new Proxy({}, splitModuleProxyHandler);
     }
-    return target[prop];
+    return target[namespace];
   }
 };
 #endif

From 3c5e7ad2282f444704a5cee4c3b70791c1dca231 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 06:21:03 +0000
Subject: [PATCH 04/17] namespace -> env

---
 src/preamble.js | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 4d38d912aa456..5286391de61ab 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -488,8 +488,8 @@ async function getWasmBinary(binaryFile) {
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
 var wasmImportsProxyHandler = {
-  get(target, namespace, receiver) {
-    if (namespace.startsWith('placeholder')) {
+  get(target, env, receiver) {
+    if (env.startsWith('placeholder')) {
       var splitModuleProxyHandler = {
         get(target, prop, receiver) {
           return (...args) => {
@@ -516,7 +516,7 @@ var wasmImportsProxyHandler = {
       };
       return new Proxy({}, splitModuleProxyHandler);
     }
-    return target[namespace];
+    return target[env];
   }
 };
 #endif

From 3ddcbd19848e05a759127d9ad4f66b3b8995a111 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 06:55:59 +0000
Subject: [PATCH 05/17] Rename `prop` -> `base`

---
 src/preamble.js | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 5286391de61ab..328ea113ec79f 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -491,25 +491,25 @@ var wasmImportsProxyHandler = {
   get(target, env, receiver) {
     if (env.startsWith('placeholder')) {
       var splitModuleProxyHandler = {
-        get(target, prop, receiver) {
+        get(target, base, receiver) {
           return (...args) => {
 #if ASYNCIFY == 2
-            throw new Error('Placeholder function "' + prop + '" should not be called when using JSPI.');
+            throw new Error('Placeholder function "' + base + '" should not be called when using JSPI.');
 #else
             // TODO: Implement multi-split module loading
-            err(`placeholder function called: ${prop}`);
+            err(`placeholder function called: ${base}`);
             var imports = {'primary': wasmExports};
             // Replace '.wasm' suffix with '.deferred.wasm'.
             var deferred = wasmBinaryFile.slice(0, -5) + '.deferred.wasm'
-            loadSplitModule(deferred, imports, prop);
+            loadSplitModule(deferred, imports, base);
             err('instantiated deferred module, continuing');
 #if RELOCATABLE
             // When the table is dynamically laid out, the placeholder functions names
             // are offsets from the table base. In the main module, the table base is
             // always 1.
-            prop = 1 + parseInt(prop);
+            base = 1 + parseInt(base);
 #endif
-            return wasmTable.get({{{ toIndexType('prop') }}})(...args);
+            return wasmTable.get({{{ toIndexType('base') }}})(...args);
 #endif
           }
         }

From b2a22d437a9c383dfaecfbe9abb4a0eba689ec8c Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 07:03:35 +0000
Subject: [PATCH 06/17] [SPLIT_MODULE] Support multi-split loading

---
 src/preamble.js | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 328ea113ec79f..f697f4bb82846 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -490,6 +490,13 @@ async function getWasmBinary(binaryFile) {
 var wasmImportsProxyHandler = {
   get(target, env, receiver) {
     if (env.startsWith('placeholder')) {
+      let secondaryFile;
+      if (env == 'placeholder') {
+        secondaryFile = wasmBinaryFile.slice(0, -5) + '.deferred.wasm';
+      } else {
+        let moduleID = env.split('.')[1];
+        secondaryFile = wasmBinaryFile.slice(0, -5) + '.' + moduleID + '.wasm';
+      }
       var splitModuleProxyHandler = {
         get(target, base, receiver) {
           return (...args) => {
@@ -500,8 +507,7 @@ var wasmImportsProxyHandler = {
             err(`placeholder function called: ${base}`);
             var imports = {'primary': wasmExports};
             // Replace '.wasm' suffix with '.deferred.wasm'.
-            var deferred = wasmBinaryFile.slice(0, -5) + '.deferred.wasm'
-            loadSplitModule(deferred, imports, base);
+            loadSplitModule(secondaryFile, imports, base);
             err('instantiated deferred module, continuing');
 #if RELOCATABLE
             // When the table is dynamically laid out, the placeholder functions names

From e918916ecd5a4705c6c98bf21f694ad2b2983864 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 21:43:19 +0000
Subject: [PATCH 07/17] wasmImportsProxyHandler -> splitImportsProxyHandler

---
 src/preamble.js | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index f697f4bb82846..0ec5415ef7e80 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -487,7 +487,7 @@ async function getWasmBinary(binaryFile) {
 
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
-var wasmImportsProxyHandler = {
+var splitImportsProxyHandler = {
   get(target, env, receiver) {
     if (env.startsWith('placeholder')) {
       let secondaryFile;
@@ -682,7 +682,7 @@ function getWasmImports() {
 #endif
   };
 #if SPLIT_MODULE
-  imports = new Proxy(imports, wasmImportsProxyHandler);
+  imports = new Proxy(imports, splitImportsProxyHandler);
 #endif
   return imports;
 }

From 6cb0c42754724b6682640750a628aba986c8b329 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 21:44:42 +0000
Subject: [PATCH 08/17] env -> moduleName

---
 src/preamble.js | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 0ec5415ef7e80..8941daeb6af5c 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -488,13 +488,13 @@ async function getWasmBinary(binaryFile) {
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
 var splitImportsProxyHandler = {
-  get(target, env, receiver) {
-    if (env.startsWith('placeholder')) {
+  get(target, moduleName, receiver) {
+    if (moduleName.startsWith('placeholder')) {
       let secondaryFile;
-      if (env == 'placeholder') {
+      if (moduleName == 'placeholder') {
         secondaryFile = wasmBinaryFile.slice(0, -5) + '.deferred.wasm';
       } else {
-        let moduleID = env.split('.')[1];
+        let moduleID = moduleName.split('.')[1];
         secondaryFile = wasmBinaryFile.slice(0, -5) + '.' + moduleID + '.wasm';
       }
       var splitModuleProxyHandler = {
@@ -522,7 +522,7 @@ var splitImportsProxyHandler = {
       };
       return new Proxy({}, splitModuleProxyHandler);
     }
-    return target[env];
+    return target[moduleName];
   }
 };
 #endif

From 4f2f3b394450db70eec4f97945ec5edce5049bbc Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 21:46:10 +0000
Subject: [PATCH 09/17] Wrap dbg messages within RUNTIME_DEBUG

---
 src/preamble.js | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 8941daeb6af5c..710e478c0b68a 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -504,11 +504,15 @@ var splitImportsProxyHandler = {
             throw new Error('Placeholder function "' + base + '" should not be called when using JSPI.');
 #else
             // TODO: Implement multi-split module loading
-            err(`placeholder function called: ${base}`);
+#if RUNTIME_DEBUG
+            dbg(`placeholder function called: ${base}`);
+#endif
             var imports = {'primary': wasmExports};
             // Replace '.wasm' suffix with '.deferred.wasm'.
             loadSplitModule(secondaryFile, imports, base);
-            err('instantiated deferred module, continuing');
+#if RUNTIME_DEBUG
+            dbg('instantiated deferred module, continuing');
+#endif
 #if RELOCATABLE
             // When the table is dynamically laid out, the placeholder functions names
             // are offsets from the table base. In the main module, the table base is

From 68c330878fcc4e2049c7e5a0788b4fd2149838ef Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 23:29:35 +0000
Subject: [PATCH 10/17] Revert "[SPLIT_MODULE] Support multi-split loading"

This reverts commit b2a22d437a9c383dfaecfbe9abb4a0eba689ec8c.
---
 src/preamble.js | 7 -------
 1 file changed, 7 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 710e478c0b68a..8c97ea91ed714 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -490,13 +490,6 @@ async function getWasmBinary(binaryFile) {
 var splitImportsProxyHandler = {
   get(target, moduleName, receiver) {
     if (moduleName.startsWith('placeholder')) {
-      let secondaryFile;
-      if (moduleName == 'placeholder') {
-        secondaryFile = wasmBinaryFile.slice(0, -5) + '.deferred.wasm';
-      } else {
-        let moduleID = moduleName.split('.')[1];
-        secondaryFile = wasmBinaryFile.slice(0, -5) + '.' + moduleID + '.wasm';
-      }
       var splitModuleProxyHandler = {
         get(target, base, receiver) {
           return (...args) => {

From eaea168cee1d1c7a423b2abed387f07d7e6aab62 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 23:36:35 +0000
Subject: [PATCH 11/17] Rename handlers

---
 src/preamble.js | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 8c97ea91ed714..3fa0fc3ed3b22 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -487,10 +487,10 @@ async function getWasmBinary(binaryFile) {
 
 #if SPLIT_MODULE
 {{{ makeModuleReceiveWithVar('loadSplitModule', undefined, 'instantiateSync') }}}
-var splitImportsProxyHandler = {
+var splitModuleProxyHandler = {
   get(target, moduleName, receiver) {
     if (moduleName.startsWith('placeholder')) {
-      var splitModuleProxyHandler = {
+      var innerHandler = {
         get(target, base, receiver) {
           return (...args) => {
 #if ASYNCIFY == 2
@@ -517,7 +517,7 @@ var splitImportsProxyHandler = {
           }
         }
       };
-      return new Proxy({}, splitModuleProxyHandler);
+      return new Proxy({}, innerHandler);
     }
     return target[moduleName];
   }
@@ -679,7 +679,7 @@ function getWasmImports() {
 #endif
   };
 #if SPLIT_MODULE
-  imports = new Proxy(imports, splitImportsProxyHandler);
+  imports = new Proxy(imports, splitModuleProxyHandler);
 #endif
   return imports;
 }

From 147482f49c53252e7182fdb901a80e9196e3ed57 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 23:38:54 +0000
Subject: [PATCH 12/17] Automatic rebaseline of codesize expectations. NFC

This is an automatic change generated by tools/maint/rebaseline_tests.py.

The following (5) test expectation files were updated by
running the tests with `--rebaseline`:

```
codesize/test_codesize_cxx_wasmfs.json: 176780 => 176780 [+0 bytes / +0.00%]
codesize/test_codesize_files_wasmfs.json: 55683 => 55683 [+0 bytes / +0.00%]
codesize/test_codesize_hello_O0.json: 39189 => 39197 [+8 bytes / +0.02%]
codesize/test_codesize_hello_dylink_all.json: 843559 => 843553 [-6 bytes / -0.00%]
codesize/test_unoptimized_code_size.json: 180290 => 180314 [+24 bytes / +0.01%]

Average change: +0.01% (-0.00% - +0.02%)
```
---
 test/codesize/test_codesize_cxx_wasmfs.json      |  4 ++--
 test/codesize/test_codesize_files_wasmfs.json    |  4 ++--
 test/codesize/test_codesize_hello_O0.json        |  8 ++++----
 .../codesize/test_codesize_hello_dylink_all.json |  4 ++--
 test/codesize/test_unoptimized_code_size.json    | 16 ++++++++--------
 5 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/test/codesize/test_codesize_cxx_wasmfs.json b/test/codesize/test_codesize_cxx_wasmfs.json
index 3021f01f12876..3b2be1f142d31 100644
--- a/test/codesize/test_codesize_cxx_wasmfs.json
+++ b/test/codesize/test_codesize_cxx_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 7059,
   "a.out.js.gz": 3330,
   "a.out.nodebug.wasm": 169721,
-  "a.out.nodebug.wasm.gz": 62981,
+  "a.out.nodebug.wasm.gz": 62983,
   "total": 176780,
-  "total_gz": 66311,
+  "total_gz": 66313,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_files_wasmfs.json b/test/codesize/test_codesize_files_wasmfs.json
index fb687e208a871..5497bd2b1ee39 100644
--- a/test/codesize/test_codesize_files_wasmfs.json
+++ b/test/codesize/test_codesize_files_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 5465,
   "a.out.js.gz": 2576,
   "a.out.nodebug.wasm": 50218,
-  "a.out.nodebug.wasm.gz": 18086,
+  "a.out.nodebug.wasm.gz": 18082,
   "total": 55683,
-  "total_gz": 20662,
+  "total_gz": 20658,
   "sent": [
     "a (emscripten_date_now)",
     "b (emscripten_err)",
diff --git a/test/codesize/test_codesize_hello_O0.json b/test/codesize/test_codesize_hello_O0.json
index 701ff3b943459..3586b686893df 100644
--- a/test/codesize/test_codesize_hello_O0.json
+++ b/test/codesize/test_codesize_hello_O0.json
@@ -1,10 +1,10 @@
 {
   "a.out.js": 24070,
   "a.out.js.gz": 8666,
-  "a.out.nodebug.wasm": 15119,
-  "a.out.nodebug.wasm.gz": 7444,
-  "total": 39189,
-  "total_gz": 16110,
+  "a.out.nodebug.wasm": 15127,
+  "a.out.nodebug.wasm.gz": 7450,
+  "total": 39197,
+  "total_gz": 16116,
   "sent": [
     "fd_write"
   ],
diff --git a/test/codesize/test_codesize_hello_dylink_all.json b/test/codesize/test_codesize_hello_dylink_all.json
index 05ebe029c71ac..aa27e63c7d228 100644
--- a/test/codesize/test_codesize_hello_dylink_all.json
+++ b/test/codesize/test_codesize_hello_dylink_all.json
@@ -1,7 +1,7 @@
 {
   "a.out.js": 245829,
-  "a.out.nodebug.wasm": 597730,
-  "total": 843559,
+  "a.out.nodebug.wasm": 597724,
+  "total": 843553,
   "sent": [
     "IMG_Init",
     "IMG_Load",
diff --git a/test/codesize/test_unoptimized_code_size.json b/test/codesize/test_unoptimized_code_size.json
index ae60057550c37..c583e5c655fb6 100644
--- a/test/codesize/test_unoptimized_code_size.json
+++ b/test/codesize/test_unoptimized_code_size.json
@@ -1,16 +1,16 @@
 {
   "hello_world.js": 56592,
   "hello_world.js.gz": 17608,
-  "hello_world.wasm": 15119,
-  "hello_world.wasm.gz": 7444,
+  "hello_world.wasm": 15127,
+  "hello_world.wasm.gz": 7450,
   "no_asserts.js": 26634,
   "no_asserts.js.gz": 8883,
-  "no_asserts.wasm": 12219,
-  "no_asserts.wasm.gz": 6005,
+  "no_asserts.wasm": 12227,
+  "no_asserts.wasm.gz": 6010,
   "strict.js": 54607,
   "strict.js.gz": 16955,
-  "strict.wasm": 15119,
-  "strict.wasm.gz": 7442,
-  "total": 180290,
-  "total_gz": 64337
+  "strict.wasm": 15127,
+  "strict.wasm.gz": 7447,
+  "total": 180314,
+  "total_gz": 64353
 }

From 3919476bc3c5735dc68ff7dfe2565669a670e7b5 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 23:54:27 +0000
Subject: [PATCH 13/17] Fix errors from previous revert ;(

---
 src/preamble.js | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/src/preamble.js b/src/preamble.js
index 3fa0fc3ed3b22..4226ea800efe3 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -502,7 +502,8 @@ var splitModuleProxyHandler = {
 #endif
             var imports = {'primary': wasmExports};
             // Replace '.wasm' suffix with '.deferred.wasm'.
-            loadSplitModule(secondaryFile, imports, base);
+            var deferred = wasmBinaryFile.slice(0, -5) + '.deferred.wasm'
+            loadSplitModule(deferred, imports, base);
 #if RUNTIME_DEBUG
             dbg('instantiated deferred module, continuing');
 #endif

From 67e5380b3b9fc1f3e77f2b619c7cc6b12cc3a9d0 Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Wed, 15 Oct 2025 23:58:34 +0000
Subject: [PATCH 14/17] Anonymize the inner handler

---
 src/preamble.js | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/src/preamble.js b/src/preamble.js
index 4226ea800efe3..145964a2bf704 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -490,7 +490,7 @@ async function getWasmBinary(binaryFile) {
 var splitModuleProxyHandler = {
   get(target, moduleName, receiver) {
     if (moduleName.startsWith('placeholder')) {
-      var innerHandler = {
+      return new Proxy({}, {
         get(target, base, receiver) {
           return (...args) => {
 #if ASYNCIFY == 2
@@ -517,8 +517,7 @@ var splitModuleProxyHandler = {
 #endif
           }
         }
-      };
-      return new Proxy({}, innerHandler);
+      });
     }
     return target[moduleName];
   }

From 13f034dc3895ebdb53c3620e50a763b41f890e6d Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Thu, 16 Oct 2025 00:05:20 +0000
Subject: [PATCH 15/17] Remove a newline added by mistake

---
 src/preamble.js | 1 -
 1 file changed, 1 deletion(-)

diff --git a/src/preamble.js b/src/preamble.js
index 145964a2bf704..a8c91274d6e6c 100644
--- a/src/preamble.js
+++ b/src/preamble.js
@@ -645,7 +645,6 @@ async function instantiateAsync(binary, binaryFile, imports) {
 #endif // SOURCE_PHASE_IMPORTS
 
 #if !WASM_ESM_INTEGRATION
-
 function getWasmImports() {
 #if PTHREADS || WASM_WORKERS || (IMPORTED_MEMORY && MODULARIZE == 'instance')
   assignWasmImports();

From d0a19db38270ccc275a5a50df062203cabe4a7ce Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Thu, 16 Oct 2025 00:31:38 +0000
Subject: [PATCH 16/17] Automatic rebaseline of codesize expectations. NFC

This is an automatic change generated by tools/maint/rebaseline_tests.py.

The following (5) test expectation files were updated by
running the tests with `--rebaseline`:

```
codesize/test_codesize_cxx_wasmfs.json: 176780 => 176780 [+0 bytes / +0.00%]
codesize/test_codesize_files_wasmfs.json: 55683 => 55683 [+0 bytes / +0.00%]
codesize/test_codesize_hello_O0.json: 39197 => 39189 [-8 bytes / -0.02%]
codesize/test_codesize_hello_dylink_all.json: 843553 => 843559 [+6 bytes / +0.00%]
codesize/test_unoptimized_code_size.json: 180314 => 180290 [-24 bytes / -0.01%]

Average change: -0.01% (-0.02% - +0.00%)
```
---
 test/codesize/test_codesize_cxx_wasmfs.json      |  4 ++--
 test/codesize/test_codesize_files_wasmfs.json    |  4 ++--
 test/codesize/test_codesize_hello_O0.json        |  8 ++++----
 .../codesize/test_codesize_hello_dylink_all.json |  4 ++--
 test/codesize/test_unoptimized_code_size.json    | 16 ++++++++--------
 5 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/test/codesize/test_codesize_cxx_wasmfs.json b/test/codesize/test_codesize_cxx_wasmfs.json
index 3b2be1f142d31..3021f01f12876 100644
--- a/test/codesize/test_codesize_cxx_wasmfs.json
+++ b/test/codesize/test_codesize_cxx_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 7059,
   "a.out.js.gz": 3330,
   "a.out.nodebug.wasm": 169721,
-  "a.out.nodebug.wasm.gz": 62983,
+  "a.out.nodebug.wasm.gz": 62981,
   "total": 176780,
-  "total_gz": 66313,
+  "total_gz": 66311,
   "sent": [
     "__cxa_throw",
     "_abort_js",
diff --git a/test/codesize/test_codesize_files_wasmfs.json b/test/codesize/test_codesize_files_wasmfs.json
index 5497bd2b1ee39..fb687e208a871 100644
--- a/test/codesize/test_codesize_files_wasmfs.json
+++ b/test/codesize/test_codesize_files_wasmfs.json
@@ -2,9 +2,9 @@
   "a.out.js": 5465,
   "a.out.js.gz": 2576,
   "a.out.nodebug.wasm": 50218,
-  "a.out.nodebug.wasm.gz": 18082,
+  "a.out.nodebug.wasm.gz": 18086,
   "total": 55683,
-  "total_gz": 20658,
+  "total_gz": 20662,
   "sent": [
     "a (emscripten_date_now)",
     "b (emscripten_err)",
diff --git a/test/codesize/test_codesize_hello_O0.json b/test/codesize/test_codesize_hello_O0.json
index 3586b686893df..701ff3b943459 100644
--- a/test/codesize/test_codesize_hello_O0.json
+++ b/test/codesize/test_codesize_hello_O0.json
@@ -1,10 +1,10 @@
 {
   "a.out.js": 24070,
   "a.out.js.gz": 8666,
-  "a.out.nodebug.wasm": 15127,
-  "a.out.nodebug.wasm.gz": 7450,
-  "total": 39197,
-  "total_gz": 16116,
+  "a.out.nodebug.wasm": 15119,
+  "a.out.nodebug.wasm.gz": 7444,
+  "total": 39189,
+  "total_gz": 16110,
   "sent": [
     "fd_write"
   ],
diff --git a/test/codesize/test_codesize_hello_dylink_all.json b/test/codesize/test_codesize_hello_dylink_all.json
index aa27e63c7d228..05ebe029c71ac 100644
--- a/test/codesize/test_codesize_hello_dylink_all.json
+++ b/test/codesize/test_codesize_hello_dylink_all.json
@@ -1,7 +1,7 @@
 {
   "a.out.js": 245829,
-  "a.out.nodebug.wasm": 597724,
-  "total": 843553,
+  "a.out.nodebug.wasm": 597730,
+  "total": 843559,
   "sent": [
     "IMG_Init",
     "IMG_Load",
diff --git a/test/codesize/test_unoptimized_code_size.json b/test/codesize/test_unoptimized_code_size.json
index c583e5c655fb6..ae60057550c37 100644
--- a/test/codesize/test_unoptimized_code_size.json
+++ b/test/codesize/test_unoptimized_code_size.json
@@ -1,16 +1,16 @@
 {
   "hello_world.js": 56592,
   "hello_world.js.gz": 17608,
-  "hello_world.wasm": 15127,
-  "hello_world.wasm.gz": 7450,
+  "hello_world.wasm": 15119,
+  "hello_world.wasm.gz": 7444,
   "no_asserts.js": 26634,
   "no_asserts.js.gz": 8883,
-  "no_asserts.wasm": 12227,
-  "no_asserts.wasm.gz": 6010,
+  "no_asserts.wasm": 12219,
+  "no_asserts.wasm.gz": 6005,
   "strict.js": 54607,
   "strict.js.gz": 16955,
-  "strict.wasm": 15127,
-  "strict.wasm.gz": 7447,
-  "total": 180314,
-  "total_gz": 64353
+  "strict.wasm": 15119,
+  "strict.wasm.gz": 7442,
+  "total": 180290,
+  "total_gz": 64337
 }

From 6bb859f7c83bdc66a35c596142f66496442a3cfc Mon Sep 17 00:00:00 2001
From: Heejin Ahn <aheejin@gmail.com>
Date: Thu, 16 Oct 2025 16:25:06 +0000
Subject: [PATCH 17/17] Automatic rebaseline of codesize expectations. NFC

This is an automatic change generated by tools/maint/rebaseline_tests.py.

The following (1) test expectation files were updated by
running the tests with `--rebaseline`:

```
codesize/test_unoptimized_code_size.json: 180212 => 180290 [+78 bytes / +0.04%]

Average change: +0.04% (+0.04% - +0.04%)
```
---
 test/codesize/test_unoptimized_code_size.json | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/test/codesize/test_unoptimized_code_size.json b/test/codesize/test_unoptimized_code_size.json
index c176785aaee1c..ae60057550c37 100644
--- a/test/codesize/test_unoptimized_code_size.json
+++ b/test/codesize/test_unoptimized_code_size.json
@@ -1,16 +1,16 @@
 {
-  "hello_world.js": 56566,
-  "hello_world.js.gz": 17601,
+  "hello_world.js": 56592,
+  "hello_world.js.gz": 17608,
   "hello_world.wasm": 15119,
   "hello_world.wasm.gz": 7444,
-  "no_asserts.js": 26608,
-  "no_asserts.js.gz": 8874,
+  "no_asserts.js": 26634,
+  "no_asserts.js.gz": 8883,
   "no_asserts.wasm": 12219,
   "no_asserts.wasm.gz": 6005,
-  "strict.js": 54581,
-  "strict.js.gz": 16947,
+  "strict.js": 54607,
+  "strict.js.gz": 16955,
   "strict.wasm": 15119,
   "strict.wasm.gz": 7442,
-  "total": 180212,
-  "total_gz": 64313
+  "total": 180290,
+  "total_gz": 64337
 }