diff --git a/.gitignore b/.gitignore
index a7bffed..e703372 100644
--- a/.gitignore
+++ b/.gitignore
@@ -30,6 +30,9 @@ cmake-build-*/
 # Emscripten cache
 .emscripten_cache/
 
+# Local emsdk installation (managed by scripts/setup-emsdk.sh)
+/tools/emsdk/
+
 # Clean clone for reproducible builds (generated by build-wxwidgets-wasm-clean.sh)
 wxwidgets-clean/
 
diff --git a/README.md b/README.md
index 871ea29..18506ea 100644
--- a/README.md
+++ b/README.md
@@ -28,7 +28,7 @@ npm run test:kicad    # KiCad tests (2 tests)
 ### wxWidgets Only (No Docker)
 
 ```bash
-# Requires: Emscripten SDK 4.0+, Node.js 18+
+# Requires: Node.js 18+ (Emscripten SDK auto-installed on first build)
 ./scripts/build-wxuniversal-wasm.sh
 ./scripts/build-wasm-test.sh
 cd tests && npm install && npm test
@@ -117,15 +117,15 @@ Output: `tests/apps/standalone/`
 - 10+ GB disk space for build cache
 
 ### For wxWidgets Build (Local)
-- Emscripten SDK 4.0+
 - Node.js 18+ (for tests)
+- Emscripten SDK (auto-installed on first build)
 
 ```bash
-# macOS
-brew install emscripten node
-
 # Initialize submodules
 git submodule update --init --recursive
+
+# Install Emscripten SDK (auto-runs on first build, or run manually)
+./scripts/setup-emsdk.sh
 ```
 
 ## Testing
diff --git a/docker/Dockerfile b/docker/Dockerfile
index 2e2cca1..fc69fca 100644
--- a/docker/Dockerfile
+++ b/docker/Dockerfile
@@ -1,5 +1,5 @@
 # Use ARM64-native image for Apple Silicon (M1/M2/M3/M4)
-FROM emscripten/emsdk:4.0.22-arm64
+FROM emscripten/emsdk:4.0.2-arm64
 
 # Install build tools required for KiCad WASM build
 RUN apt-get update && apt-get install -y \
diff --git a/docker/build.sh b/docker/build.sh
index 7dc66ca..30f8561 100755
--- a/docker/build.sh
+++ b/docker/build.sh
@@ -33,6 +33,7 @@ docker compose -f docker/docker-compose.yml up -d
 # This avoids the timestamp mismatch cycle that caused full rebuilds every time.
 # Transferred files get current container time, so make detects them correctly.
 echo "Syncing source code to container..."
+# rsync exit code 24 = "some files vanished before transfer" (harmless race condition)
 docker compose -f docker/docker-compose.yml exec kicad-wasm-builder \
     rsync -r --delete --checksum \
         --exclude="build-wasm" \
@@ -41,7 +42,8 @@ docker compose -f docker/docker-compose.yml exec kicad-wasm-builder \
         --exclude="logs" \
         --exclude=".idea" \
         --exclude="node_modules" \
-        /workspace-host/ /workspace/
+        --exclude="tools/emsdk" \
+        /workspace-host/ /workspace/ || [ $? -eq 24 ]
 
 # Run build command (without asyncify - handled on host due to memory requirements)
 docker compose -f docker/docker-compose.yml exec kicad-wasm-builder \
diff --git a/scripts/build-gal-webgl-test.sh b/scripts/build-gal-webgl-test.sh
index 1e9ad24..e0aca78 100755
--- a/scripts/build-gal-webgl-test.sh
+++ b/scripts/build-gal-webgl-test.sh
@@ -21,7 +21,7 @@ set -e
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 
-# Source common environment (sets up Python 3.10+ for Emscripten)
+# Source common environment (sets up local emsdk)
 QUIET=1 source "$SCRIPT_DIR/common/env.sh"
 
 TEST_DIR="$PROJECT_ROOT/tests/gal-regression/wasm"
@@ -35,7 +35,7 @@ echo "  clang: $(which clang)"
 
 # Verify em++ is available
 if ! command -v em++ &> /dev/null; then
-    echo "ERROR: em++ not found. Please install via: brew install emscripten"
+    echo "ERROR: em++ not found. Run: ./scripts/setup-emsdk.sh"
     exit 1
 fi
 
diff --git a/scripts/build-wxuniversal-wasm.sh b/scripts/build-wxuniversal-wasm.sh
index 836df82..6283e30 100755
--- a/scripts/build-wxuniversal-wasm.sh
+++ b/scripts/build-wxuniversal-wasm.sh
@@ -4,12 +4,12 @@
 # Redirect all output to a log file (re-execs script with redirection)
 source "$(dirname "$0")/common/logging.sh"
 
-# Source common environment (sets up EMSDK_PYTHON for Emscripten 4.0.22+)
+# Source common environment (sets up local emsdk)
 source "$(dirname "$0")/common/env.sh"
 # This builds the GUI-enabled wxWidgets needed for KiCad
 #
 # Prerequisites:
-# - Emscripten SDK installed and activated
+# - Emscripten SDK (auto-installed by env.sh via scripts/setup-emsdk.sh)
 # - autoconf (for regenerating configure from configure.in)
 #
 # To regenerate Makefile.in from bakefiles (after modifying files.bkl):
@@ -23,14 +23,6 @@ source "$(dirname "$0")/common/env.sh"
 
 set -e
 
-# Ensure 'python' command is available (macOS only has python3)
-# Homebrew's python libexec has the python -> python3 symlink
-if [[ -d "/opt/homebrew/opt/python/libexec/bin" ]]; then
-    export PATH="/opt/homebrew/opt/python/libexec/bin:$PATH"
-elif [[ -d "/usr/local/opt/python/libexec/bin" ]]; then
-    export PATH="/usr/local/opt/python/libexec/bin:$PATH"
-fi
-
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
 BUILD_DIR="$PROJECT_ROOT/build-wasm/wxwidgets-universal"
diff --git a/scripts/common/env.sh b/scripts/common/env.sh
index 268b94a..7916a74 100755
--- a/scripts/common/env.sh
+++ b/scripts/common/env.sh
@@ -36,47 +36,18 @@ export WX_BUILD="$BUILD_ROOT/wxwidgets-universal"
 # Emscripten settings
 export EMSDK_QUIET=1
 
-# Homebrew Emscripten configuration
-# The em++ script uses EMSDK_PYTHON (not PYTHON env var) for the Python interpreter
-# and finds clang via PATH - Emscripten bundles its own LLVM with WebAssembly support
-if [[ -d "/opt/homebrew/Cellar/emscripten" ]]; then
-    _EM_VERSION=$(ls /opt/homebrew/Cellar/emscripten/ | sort -V | tail -1)
-    _EM_LLVM_BIN="/opt/homebrew/Cellar/emscripten/$_EM_VERSION/libexec/llvm/bin"
-    if [[ -d "$_EM_LLVM_BIN" ]]; then
-        # Add bundled LLVM to PATH so Emscripten finds its clang (not /usr/bin/clang)
-        export PATH="$_EM_LLVM_BIN:$PATH"
-    fi
-elif [[ -d "/usr/local/Cellar/emscripten" ]]; then
-    _EM_VERSION=$(ls /usr/local/Cellar/emscripten/ | sort -V | tail -1)
-    _EM_LLVM_BIN="/usr/local/Cellar/emscripten/$_EM_VERSION/libexec/llvm/bin"
-    if [[ -d "$_EM_LLVM_BIN" ]]; then
-        export PATH="$_EM_LLVM_BIN:$PATH"
-    fi
+# Local emsdk: auto-install if missing, then source its environment
+# The emsdk bundles its own Python, Node, and LLVM — no Homebrew needed
+_EMSDK_DIR="$_KICAD_WASM_PROJECT_ROOT/tools/emsdk"
+_EMSDK_ENV="$_EMSDK_DIR/emsdk_env.sh"
+
+if [ ! -f "$_EMSDK_ENV" ]; then
+    echo "Emscripten SDK not found. Installing..."
+    "$_KICAD_WASM_SCRIPTS_DIR/setup-emsdk.sh"
 fi
 
-# Emscripten 4.0.22+ requires Python 3.10+ (uses match statement and type union syntax)
-# The em++ shell script checks EMSDK_PYTHON first, then falls back to `which python3`
-# Set EMSDK_PYTHON to Homebrew's Python to ensure correct version is used
-if [[ -d "/opt/homebrew/opt/python@3.14/bin" ]]; then
-    export EMSDK_PYTHON="/opt/homebrew/opt/python@3.14/bin/python3.14"
-elif [[ -d "/opt/homebrew/opt/python@3.13/bin" ]]; then
-    export EMSDK_PYTHON="/opt/homebrew/opt/python@3.13/bin/python3.13"
-elif [[ -d "/opt/homebrew/opt/python@3.12/bin" ]]; then
-    export EMSDK_PYTHON="/opt/homebrew/opt/python@3.12/bin/python3.12"
-elif [[ -d "/opt/homebrew/opt/python@3.11/bin" ]]; then
-    export EMSDK_PYTHON="/opt/homebrew/opt/python@3.11/bin/python3.11"
-elif [[ -d "/opt/homebrew/opt/python@3.10/bin" ]]; then
-    export EMSDK_PYTHON="/opt/homebrew/opt/python@3.10/bin/python3.10"
-elif [[ -d "/usr/local/opt/python@3.14/bin" ]]; then
-    export EMSDK_PYTHON="/usr/local/opt/python@3.14/bin/python3.14"
-elif [[ -d "/usr/local/opt/python@3.13/bin" ]]; then
-    export EMSDK_PYTHON="/usr/local/opt/python@3.13/bin/python3.13"
-elif [[ -d "/usr/local/opt/python@3.12/bin" ]]; then
-    export EMSDK_PYTHON="/usr/local/opt/python@3.12/bin/python3.12"
-elif [[ -d "/usr/local/opt/python@3.11/bin" ]]; then
-    export EMSDK_PYTHON="/usr/local/opt/python@3.11/bin/python3.11"
-elif [[ -d "/usr/local/opt/python@3.10/bin" ]]; then
-    export EMSDK_PYTHON="/usr/local/opt/python@3.10/bin/python3.10"
+if [ -f "$_EMSDK_ENV" ]; then
+    source "$_EMSDK_ENV" 2>/dev/null
 fi
 
 # Common compiler flags
diff --git a/scripts/common/functions.sh b/scripts/common/functions.sh
index 36e8b76..82d2c09 100755
--- a/scripts/common/functions.sh
+++ b/scripts/common/functions.sh
@@ -53,7 +53,7 @@ setup_error_trap() {
 # Verify Emscripten is available
 verify_emscripten() {
     if ! command -v emcc &> /dev/null; then
-        log_error "Emscripten not found. Please run: source /path/to/emsdk/emsdk_env.sh"
+        log_error "Emscripten not found. Run: ./scripts/setup-emsdk.sh"
         exit 1
     fi
     log_info "Using Emscripten: $(emcc --version | head -1)"
diff --git a/scripts/common/get-wasm-opt.sh b/scripts/common/get-wasm-opt.sh
index 647505e..a20b980 100755
--- a/scripts/common/get-wasm-opt.sh
+++ b/scripts/common/get-wasm-opt.sh
@@ -1,17 +1,35 @@
 #!/bin/bash
-# Download and cache Binaryen wasm-opt
+# Get path to Binaryen wasm-opt
 #
-# Usage: ./scripts/tools/get-wasm-opt.sh
+# Usage: ./scripts/common/get-wasm-opt.sh
 # Output: Prints path to wasm-opt executable
 #
-# Binaryen v121 is used because v125 has a regression causing asyncify crashes.
-# The binary is cached in tools/binaryen-121/
+# Prefers the emsdk-bundled Binaryen (tools/emsdk/upstream/bin/) so that the
+# wasm-opt and wasm-emscripten-finalize versions match the Emscripten that
+# generated the JS glue. A version mismatch between the compiler's Binaryen
+# (e.g. v121+72 dev) and a standalone release (v121) corrupts asyncify
+# metadata, causing "func is not a function" errors at runtime.
+#
+# Falls back to downloading standalone Binaryen v121 if emsdk is not installed
+# locally (e.g. CI environments that only use Docker).
 
 set -e
 
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 PROJECT_ROOT="$(cd "${SCRIPT_DIR}/../.." && pwd)"
 
+# --- Prefer emsdk-bundled Binaryen (matches the Emscripten that compiled the WASM) ---
+EMSDK_WASM_OPT="${PROJECT_ROOT}/tools/emsdk/upstream/bin/wasm-opt"
+if [ -x "${EMSDK_WASM_OPT}" ]; then
+    EMSDK_VERSION=$("${EMSDK_WASM_OPT}" --version 2>&1 || true)
+    echo "Using emsdk-bundled Binaryen: ${EMSDK_VERSION}" >&2
+    echo "${EMSDK_WASM_OPT}"
+    exit 0
+fi
+
+# --- Fallback: download standalone Binaryen (for CI or environments without local emsdk) ---
+echo "emsdk Binaryen not found at ${EMSDK_WASM_OPT}, falling back to standalone download..." >&2
+
 BINARYEN_VERSION="121"
 BINARYEN_DIR="${PROJECT_ROOT}/build-wasm/tools/binaryen-${BINARYEN_VERSION}"
 WASM_OPT="${BINARYEN_DIR}/bin/wasm-opt"
diff --git a/scripts/common/inject-dyncall-shims.sh b/scripts/common/inject-dyncall-shims.sh
index d89ea9b..d0d2e74 100755
--- a/scripts/common/inject-dyncall-shims.sh
+++ b/scripts/common/inject-dyncall-shims.sh
@@ -38,6 +38,11 @@ cat > "$SHIM_FILE" << 'HEADER'
 // === dynCall shims for Emscripten exception handling ===
 // Auto-generated: maps dynCall_SIG() calls to getWasmTableEntry()
 // This fixes "dynCall_* is not defined" errors in Emscripten 4.x
+//
+// These shims are asyncify-aware: they track Asyncify.exportCallStack so that
+// asyncify can rewind through indirect calls (e.g., main loop callbacks,
+// timer callbacks, event handlers). Without this tracking, asyncify's doRewind
+// fails because it can't find the entry function to re-enter the WASM module.
 HEADER
 
 for sig in $SIGNATURES; do
@@ -55,12 +60,31 @@ for sig in $SIGNATURES; do
         call_args="${call_args}a$i"
     done
 
-    echo "var dynCall_$sig = ($args) => getWasmTableEntry(index)($call_args);" >> "$SHIM_FILE"
+    cat >> "$SHIM_FILE" << SHIMEOF
+function dynCall_$sig($args) {
+  var tableFunc = getWasmTableEntry(index);
+  if (typeof Asyncify !== 'undefined') {
+    var rewindKey = '__dyn_${sig}_' + index;
+    if (!wasmExports[rewindKey]) wasmExports[rewindKey] = tableFunc;
+    Asyncify.exportCallStack.push(rewindKey);
+    try {
+      return tableFunc($call_args);
+    } finally {
+      if (!ABORT) {
+        Asyncify.exportCallStack.pop();
+        Asyncify.maybeStopUnwind();
+      }
+    }
+  }
+  return tableFunc($call_args);
+}
+SHIMEOF
 done
 
 echo "" >> "$SHIM_FILE"
 echo "// === End dynCall shims ===" >> "$SHIM_FILE"
 
+
 # Find the insertion point: after getWasmTableEntry definition
 # The pattern is:
 #   var getWasmTableEntry = funcPtr => {
@@ -169,6 +193,18 @@ if [ "$COUNT_BEFORE" -gt 0 ]; then
     TOTAL_FIXED=$((TOTAL_FIXED + FIXED))
 fi
 
+# Fix 5: _emscripten_set_main_loop empty iterFunc callback - signature v (void, no args)
+# Pattern: var iterFunc = (() => {});
+# The 'func' variable is the function pointer passed to _emscripten_set_main_loop
+COUNT_BEFORE=$(grep -c 'var iterFunc = (() => {});' "$JS_FILE" || true)
+if [ "$COUNT_BEFORE" -gt 0 ]; then
+    sed -i '' 's/var iterFunc = (() => {});/var iterFunc = () => dynCall_v(func);/g' "$JS_FILE"
+    COUNT_AFTER=$(grep -c 'var iterFunc = (() => {});' "$JS_FILE" || true)
+    FIXED=$((COUNT_BEFORE - COUNT_AFTER))
+    echo "  Fixed $FIXED main loop callback(s) (dynCall_v)"
+    TOTAL_FIXED=$((TOTAL_FIXED + FIXED))
+fi
+
 if [ "$TOTAL_FIXED" -gt 0 ]; then
     echo "Total: Fixed $TOTAL_FIXED empty callback(s)"
 else
diff --git a/scripts/common/versions.sh b/scripts/common/versions.sh
index 1cb9739..85d5a40 100755
--- a/scripts/common/versions.sh
+++ b/scripts/common/versions.sh
@@ -2,6 +2,9 @@
 # Dependency versions for KiCad WASM build
 # These versions match KiCad 8.99 requirements from CMakeLists.txt and vcpkg.json
 
+# Emscripten SDK version (single source of truth for Docker and local builds)
+export EMSCRIPTEN_VERSION="4.0.2"
+
 # KiCad submodule version
 export KICAD_COMMIT="4bfed3f1746e8cc0a7d942767770f56fa28b393c"
 export KICAD_VERSION="8.99"
diff --git a/scripts/setup-emsdk.sh b/scripts/setup-emsdk.sh
new file mode 100755
index 0000000..be93317
--- /dev/null
+++ b/scripts/setup-emsdk.sh
@@ -0,0 +1,60 @@
+#!/bin/bash
+# Install and activate the Emscripten SDK (emsdk) locally
+#
+# This script is idempotent - it skips installation if the correct version
+# is already installed. The emsdk is installed into tools/emsdk/ which is
+# gitignored (~1.5GB).
+#
+# Usage:
+#   ./scripts/setup-emsdk.sh          # Install/activate pinned version
+#   ./scripts/setup-emsdk.sh --force  # Force reinstall
+
+set -e
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+PROJECT_ROOT="$(dirname "$SCRIPT_DIR")"
+
+# Source version constants
+source "$SCRIPT_DIR/common/versions.sh"
+
+EMSDK_DIR="$PROJECT_ROOT/tools/emsdk"
+VERSION="$EMSCRIPTEN_VERSION"
+
+echo "=== Emscripten SDK Setup ==="
+echo "  Version: $VERSION"
+echo "  Location: $EMSDK_DIR"
+
+# Check if already installed with correct version (unless --force)
+if [ "$1" != "--force" ] && [ -f "$EMSDK_DIR/emsdk" ]; then
+    if "$EMSDK_DIR/emsdk" list 2>/dev/null | grep -q "^[[:space:]]*${VERSION}[[:space:]]*INSTALLED"; then
+        echo "Emscripten $VERSION is already installed and active."
+        echo "Use --force to reinstall."
+        exit 0
+    fi
+fi
+
+# Clone emsdk if not present
+if [ ! -d "$EMSDK_DIR" ]; then
+    echo ""
+    echo "Cloning emsdk..."
+    mkdir -p "$PROJECT_ROOT/tools"
+    git clone https://github.com/emscripten-core/emsdk.git "$EMSDK_DIR"
+else
+    echo ""
+    echo "Updating emsdk..."
+    (cd "$EMSDK_DIR" && git pull)
+fi
+
+# Install and activate the pinned version
+echo ""
+echo "Installing Emscripten $VERSION..."
+"$EMSDK_DIR/emsdk" install "$VERSION"
+
+echo ""
+echo "Activating Emscripten $VERSION..."
+"$EMSDK_DIR/emsdk" activate "$VERSION"
+
+echo ""
+echo "=== Setup complete ==="
+echo "Emscripten $VERSION is ready."
+echo "Source env.sh to use it: source scripts/common/env.sh"
diff --git a/wxwidgets b/wxwidgets
index dd370ac..c5aaa19 160000
--- a/wxwidgets
+++ b/wxwidgets
@@ -1 +1 @@
-Subproject commit dd370ac191d5f20ea847b1bce4a611464f5baa65
+Subproject commit c5aaa19ca9cffe739d9ccbc99003bc712eda031e