diff --git a/src/vitalrouter-mruby/build_config.android.rb b/src/vitalrouter-mruby/build_config.android.rb
index 1fe34e9..706619c 100644
--- a/src/vitalrouter-mruby/build_config.android.rb
+++ b/src/vitalrouter-mruby/build_config.android.rb
@@ -4,11 +4,13 @@
   conf.gembox '../../../vitalrouter'
   
   conf.cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
+  conf.cc.flags << '-Os'
 end
 
 MRuby::CrossBuild.new('android-x64') do |conf|
   toolchain :android, arch: 'x86_64'
   conf.gembox '../../../vitalrouter'
 
-  conf.cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)  
+  conf.cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
+  conf.cc.flags << '-Os'
 end
diff --git a/src/vitalrouter-mruby/build_config.ios.rb b/src/vitalrouter-mruby/build_config.ios.rb
index b6fb5c1..57f3a53 100644
--- a/src/vitalrouter-mruby/build_config.ios.rb
+++ b/src/vitalrouter-mruby/build_config.ios.rb
@@ -6,7 +6,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk iphoneos clang -arch arm64 -isysroot "#{sdk}" -mios-version-min=#{IOS_VERSION_MIN} -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk iphoneos clang -arch arm64 -isysroot "#{sdk}" -mios-version-min=#{IOS_VERSION_MIN} -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
@@ -23,7 +23,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk iphonesimulator clang -arch x86_64 -isysroot "#{sdk}" -mios-version-min=#{IOS_VERSION_MIN} -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk iphonesimulator clang -arch x86_64 -isysroot "#{sdk}" -mios-version-min=#{IOS_VERSION_MIN} -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
diff --git a/src/vitalrouter-mruby/build_config.ios.rb.lock b/src/vitalrouter-mruby/build_config.ios.rb.lock
index d4f9489..4e7fad5 100644
--- a/src/vitalrouter-mruby/build_config.ios.rb.lock
+++ b/src/vitalrouter-mruby/build_config.ios.rb.lock
@@ -2,16 +2,3 @@
 mruby:
   version: 3.3.0
   release_no: 30300
-builds:
-  ios-arm64:
-    https://github.com/suzukaze/mruby-msgpack.git:
-      url: https://github.com/suzukaze/mruby-msgpack.git
-      branch: master
-      commit: d2538d8d1decc45953b21f41a5e07b9404df7bf7
-      version: 0.0.0
-  ios-x64:
-    https://github.com/suzukaze/mruby-msgpack.git:
-      url: https://github.com/suzukaze/mruby-msgpack.git
-      branch: master
-      commit: d2538d8d1decc45953b21f41a5e07b9404df7bf7
-      version: 0.0.0
diff --git a/src/vitalrouter-mruby/build_config.linux.rb b/src/vitalrouter-mruby/build_config.linux.rb
index dd2fc43..eb40dec 100644
--- a/src/vitalrouter-mruby/build_config.linux.rb
+++ b/src/vitalrouter-mruby/build_config.linux.rb
@@ -6,6 +6,7 @@
   conf.compilers.each do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)    
     cc.flags << '-fPIC'
+    cc.flags << '-Os'
   end
 
   conf.archiver do |archiver|
@@ -35,6 +36,7 @@
   conf.compilers.each do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
     cc.flags << '-fPIC'
+    cc.flags << '-Os'
   end
 
   conf.archiver do |archiver|
diff --git a/src/vitalrouter-mruby/build_config.macOS.rb b/src/vitalrouter-mruby/build_config.macOS.rb
index acca47d..648458f 100644
--- a/src/vitalrouter-mruby/build_config.macOS.rb
+++ b/src/vitalrouter-mruby/build_config.macOS.rb
@@ -6,6 +6,7 @@
 
   conf.cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
   conf.cc.flags << '-arch arm64'
+  conf.cc.flags << '-Os'
   conf.linker.flags << '-arch arm64'
 end
 
diff --git a/src/vitalrouter-mruby/build_config.tvOS.rb b/src/vitalrouter-mruby/build_config.tvOS.rb
index bc96b4b..ba152aa 100644
--- a/src/vitalrouter-mruby/build_config.tvOS.rb
+++ b/src/vitalrouter-mruby/build_config.tvOS.rb
@@ -4,7 +4,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk appletvos clang -arch arm64 -isysroot "#{sdk}" -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk appletvos clang -arch arm64 -isysroot "#{sdk}" -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
@@ -21,7 +21,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk appletvsimulator clang -arch x86_64 -isysroot "#{sdk}" -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk appletvsimulator clang -arch x86_64 -isysroot "#{sdk}" -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
diff --git a/src/vitalrouter-mruby/build_config.visionOS.rb b/src/vitalrouter-mruby/build_config.visionOS.rb
index cfbe1ba..92a13c0 100644
--- a/src/vitalrouter-mruby/build_config.visionOS.rb
+++ b/src/vitalrouter-mruby/build_config.visionOS.rb
@@ -6,7 +6,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)    
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk xros clang -arch arm64 -isysroot "#{sdk}" -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk xros clang -arch arm64 -isysroot "#{sdk}" -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
@@ -21,7 +21,7 @@
   conf.cc do |cc|
     cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)        
     cc.command = 'xcrun'
-    cc.flags = %W(-sdk xrsimulator clang -arch x86_64 -isysroot "#{sdk}" -g -O3 -Wall -Werror-implicit-function-declaration)
+    cc.flags = %W(-sdk xrsimulator clang -arch x86_64 -isysroot "#{sdk}" -g -Os -Wall -Werror-implicit-function-declaration)
   end
 
   conf.linker do |linker|
diff --git a/src/vitalrouter-mruby/build_config.wasm.rb b/src/vitalrouter-mruby/build_config.wasm.rb
index e43c173..90dfece 100644
--- a/src/vitalrouter-mruby/build_config.wasm.rb
+++ b/src/vitalrouter-mruby/build_config.wasm.rb
@@ -3,6 +3,7 @@
   conf.gembox '../../../vitalrouter'
 
   conf.cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
+  conf.cc.flags << '-Os'
   conf.cc.command = 'emcc'
   conf.linker.command = 'emcc'
   conf.archiver.command = 'emar'
diff --git a/src/vitalrouter-mruby/build_config.windows.rb b/src/vitalrouter-mruby/build_config.windows.rb
index be39dce..ba7e18e 100644
--- a/src/vitalrouter-mruby/build_config.windows.rb
+++ b/src/vitalrouter-mruby/build_config.windows.rb
@@ -3,4 +3,5 @@
   conf.toolchain
   conf.gembox '../../../vitalrouter'
   cc.defines = %w(MRB_NO_BOXING MRB_NO_STDIO)
+  cc.flags << '-Os'
 end