diff --git a/cogsetup.sh b/cogsetup.sh
index 44538f2..ef1485d 100644
--- a/cogsetup.sh
+++ b/cogsetup.sh
@@ -52,7 +52,9 @@
   # it with this function. If the user is running repo within a Cog workspace,
   # we'll fail with an error, otherwise, we run the original repo command with
   # the given args.
-  ORIG_REPO_PATH=`which repo`
+  if ! ORIG_REPO_PATH=`which repo`; then
+    return 0
+  fi
   function repo {
     if [[ "${PWD}" == /google/cog/* ]]; then
       echo "\e[01;31mERROR:\e[0mrepo command is disallowed within Cog workspaces."
diff --git a/core/dex_preopt.mk b/core/dex_preopt.mk
index 08311ca..26b8b17 100644
--- a/core/dex_preopt.mk
+++ b/core/dex_preopt.mk
@@ -123,22 +123,28 @@
 
 $(call dist-for-goals, droidcore, $(boot_zip))
 
-ifneq (,$(filter true,$(ART_MODULE_BUILD_FROM_SOURCE) $(MODULE_BUILD_FROM_SOURCE)))
 # Build the system_server.zip which contains the Apex system server jars and standalone system server jars
+system_server_dex2oat_dir := $(SOONG_OUT_DIR)/system_server_dexjars
 system_server_zip := $(PRODUCT_OUT)/system_server.zip
+# non_updatable_system_server_jars contains jars in /system and /system_ext that are not part of an apex.
+non_updatable_system_server_jars := \
+  $(foreach m,$(PRODUCT_SYSTEM_SERVER_JARS),\
+    $(system_server_dex2oat_dir)/$(call word-colon,2,$(m)).jar)
+
 apex_system_server_jars := \
   $(foreach m,$(PRODUCT_APEX_SYSTEM_SERVER_JARS),\
-    $(PRODUCT_OUT)/apex/$(call word-colon,1,$(m))/javalib/$(call word-colon,2,$(m)).jar)
+    $(system_server_dex2oat_dir)/$(call word-colon,2,$(m)).jar)
 
 apex_standalone_system_server_jars := \
   $(foreach m,$(PRODUCT_APEX_STANDALONE_SYSTEM_SERVER_JARS),\
-    $(PRODUCT_OUT)/apex/$(call word-colon,1,$(m))/javalib/$(call word-colon,2,$(m)).jar)
+    $(system_server_dex2oat_dir)/$(call word-colon,2,$(m)).jar)
 
 standalone_system_server_jars := \
   $(foreach m,$(PRODUCT_STANDALONE_SYSTEM_SERVER_JARS),\
-    $(PRODUCT_OUT)/apex/$(call word-colon,1,$(m))/javalib/$(call word-colon,2,$(m)).jar)
+    $(system_server_dex2oat_dir)/$(call word-colon,2,$(m)).jar)
 
-$(system_server_zip): PRIVATE_SYSTEM_SERVER_JARS := $(system_server_jars)
+$(system_server_zip): PRIVATE_SYSTEM_SERVER_DEX2OAT_DIR := $(system_server_dex2oat_dir)
+$(system_server_zip): PRIVATE_SYSTEM_SERVER_JARS := $(non_updatable_system_server_jars)
 $(system_server_zip): PRIVATE_APEX_SYSTEM_SERVER_JARS := $(apex_system_server_jars)
 $(system_server_zip): PRIVATE_APEX_STANDALONE_SYSTEM_SERVER_JARS := $(apex_standalone_system_server_jars)
 $(system_server_zip): PRIVATE_STANDALONE_SYSTEM_SERVER_JARS := $(standalone_system_server_jars)
@@ -146,14 +152,13 @@
 	@echo "Create system server package: $@"
 	rm -f $@
 	$(SOONG_ZIP) -o $@ \
-	  -C $(PRODUCT_OUT) $(addprefix -f ,$(PRIVATE_SYSTEM_SERVER_JARS)) \
-	  -C $(PRODUCT_OUT) $(addprefix -f ,$(PRIVATE_APEX_SYSTEM_SERVER_JARS)) \
-          -C $(PRODUCT_OUT) $(addprefix -f ,$(PRIVATE_APEX_STANDALONE_SYSTEM_SERVER_JARS)) \
-	  -C $(PRODUCT_OUT) $(addprefix -f ,$(PRIVATE_STANDALONE_SYSTEM_SERVER_JARS))
+	  -C $(PRIVATE_SYSTEM_SERVER_DEX2OAT_DIR) $(addprefix -f ,$(PRIVATE_SYSTEM_SERVER_JARS)) \
+	  -C $(PRIVATE_SYSTEM_SERVER_DEX2OAT_DIR) $(addprefix -f ,$(PRIVATE_APEX_SYSTEM_SERVER_JARS)) \
+	  -C $(PRIVATE_SYSTEM_SERVER_DEX2OAT_DIR) $(addprefix -f ,$(PRIVATE_APEX_STANDALONE_SYSTEM_SERVER_JARS)) \
+	  -C $(PRIVATE_SYSTEM_SERVER_DEX2OAT_DIR) $(addprefix -f ,$(PRIVATE_STANDALONE_SYSTEM_SERVER_JARS))
 
 $(call dist-for-goals, droidcore, $(system_server_zip))
 
-endif  #ART_MODULE_BUILD_FROM_SOURCE || MODULE_BUILD_FROM_SOURCE
 endif  #PRODUCT_USES_DEFAULT_ART_CONFIG
 endif  #WITH_DEXPREOPT_ART_BOOT_IMG_ONLY
 endif  #WITH_DEXPREOPT
diff --git a/tools/aconfig/aconfig/src/codegen/cpp.rs b/tools/aconfig/aconfig/src/codegen/cpp.rs
index cd71b10..e743b2f 100644
--- a/tools/aconfig/aconfig/src/codegen/cpp.rs
+++ b/tools/aconfig/aconfig/src/codegen/cpp.rs
@@ -16,6 +16,7 @@
 
 use anyhow::{ensure, Result};
 use serde::Serialize;
+use std::collections::HashMap;
 use std::path::PathBuf;
 use tinytemplate::TinyTemplate;
 
@@ -29,13 +30,15 @@
     package: &str,
     parsed_flags_iter: I,
     codegen_mode: CodegenMode,
+    flag_ids: HashMap<String, u16>,
+    allow_instrumentation: bool,
 ) -> Result<Vec<OutputFile>>
 where
     I: Iterator<Item = ProtoParsedFlag>,
 {
     let mut readwrite_count = 0;
     let class_elements: Vec<ClassElement> = parsed_flags_iter
-        .map(|pf| create_class_element(package, &pf, &mut readwrite_count))
+        .map(|pf| create_class_element(package, &pf, flag_ids.clone(), &mut readwrite_count))
         .collect();
     let readwrite = readwrite_count > 0;
     let has_fixed_read_only = class_elements.iter().any(|item| item.is_fixed_read_only);
@@ -53,6 +56,7 @@
         readwrite_count,
         is_test_mode: codegen_mode == CodegenMode::Test,
         class_elements,
+        allow_instrumentation,
     };
 
     let files = [
@@ -96,6 +100,7 @@
     pub readwrite_count: i32,
     pub is_test_mode: bool,
     pub class_elements: Vec<ClassElement>,
+    pub allow_instrumentation: bool,
 }
 
 #[derive(Serialize)]
@@ -106,11 +111,18 @@
     pub default_value: String,
     pub flag_name: String,
     pub flag_macro: String,
+    pub flag_offset: u16,
     pub device_config_namespace: String,
     pub device_config_flag: String,
+    pub container: String,
 }
 
-fn create_class_element(package: &str, pf: &ProtoParsedFlag, rw_count: &mut i32) -> ClassElement {
+fn create_class_element(
+    package: &str,
+    pf: &ProtoParsedFlag,
+    flag_ids: HashMap<String, u16>,
+    rw_count: &mut i32,
+) -> ClassElement {
     ClassElement {
         readwrite_idx: if pf.permission() == ProtoFlagPermission::READ_WRITE {
             let index = *rw_count;
@@ -128,9 +140,11 @@
         },
         flag_name: pf.name().to_string(),
         flag_macro: pf.name().to_uppercase(),
+        flag_offset: *flag_ids.get(pf.name()).expect("values checked at flag parse time"),
         device_config_namespace: pf.namespace().to_string(),
         device_config_flag: codegen::create_device_config_ident(package, pf.name())
             .expect("values checked at flag parse time"),
+        container: pf.container().to_string(),
     }
 }
 
@@ -1162,18 +1176,27 @@
     return true;
 }
 "#;
+    use crate::commands::assign_flag_ids;
 
     fn test_generate_cpp_code(
         parsed_flags: ProtoParsedFlags,
         mode: CodegenMode,
         expected_header: &str,
         expected_src: &str,
+        allow_instrumentation: bool,
     ) {
         let modified_parsed_flags =
             crate::commands::modify_parsed_flags_based_on_mode(parsed_flags, mode).unwrap();
-        let generated =
-            generate_cpp_code(crate::test::TEST_PACKAGE, modified_parsed_flags.into_iter(), mode)
-                .unwrap();
+        let flag_ids =
+            assign_flag_ids(crate::test::TEST_PACKAGE, modified_parsed_flags.iter()).unwrap();
+        let generated = generate_cpp_code(
+            crate::test::TEST_PACKAGE,
+            modified_parsed_flags.into_iter(),
+            mode,
+            flag_ids,
+            allow_instrumentation,
+        )
+        .unwrap();
         let mut generated_files_map = HashMap::new();
         for file in generated {
             generated_files_map.insert(
@@ -1211,6 +1234,7 @@
             CodegenMode::Production,
             EXPORTED_PROD_HEADER_EXPECTED,
             PROD_SOURCE_FILE_EXPECTED,
+            false,
         );
     }
 
@@ -1222,6 +1246,7 @@
             CodegenMode::Test,
             EXPORTED_TEST_HEADER_EXPECTED,
             TEST_SOURCE_FILE_EXPECTED,
+            false,
         );
     }
 
@@ -1233,6 +1258,7 @@
             CodegenMode::Exported,
             EXPORTED_EXPORTED_HEADER_EXPECTED,
             EXPORTED_SOURCE_FILE_EXPECTED,
+            false,
         );
     }
 
@@ -1244,6 +1270,7 @@
             CodegenMode::ForceReadOnly,
             EXPORTED_FORCE_READ_ONLY_HEADER_EXPECTED,
             FORCE_READ_ONLY_SOURCE_FILE_EXPECTED,
+            false,
         );
     }
 
@@ -1255,6 +1282,7 @@
             CodegenMode::Production,
             READ_ONLY_EXPORTED_PROD_HEADER_EXPECTED,
             READ_ONLY_PROD_SOURCE_FILE_EXPECTED,
+            false,
         );
     }
 }
diff --git a/tools/aconfig/aconfig/src/codegen/java.rs b/tools/aconfig/aconfig/src/codegen/java.rs
index 18a4be5..3360ddd 100644
--- a/tools/aconfig/aconfig/src/codegen/java.rs
+++ b/tools/aconfig/aconfig/src/codegen/java.rs
@@ -64,20 +64,27 @@
         include_str!("../../templates/FeatureFlags.java.template"),
     )?;
     template.add_template(
+        "CustomFeatureFlags.java",
+        include_str!("../../templates/CustomFeatureFlags.java.template"),
+    )?;
+    template.add_template(
         "FakeFeatureFlagsImpl.java",
         include_str!("../../templates/FakeFeatureFlagsImpl.java.template"),
     )?;
 
     let path: PathBuf = package.split('.').collect();
-    ["Flags.java", "FeatureFlags.java", "FeatureFlagsImpl.java", "FakeFeatureFlagsImpl.java"]
-        .iter()
-        .map(|file| {
-            Ok(OutputFile {
-                contents: template.render(file, &context)?.into(),
-                path: path.join(file),
-            })
-        })
-        .collect::<Result<Vec<OutputFile>>>()
+    [
+        "Flags.java",
+        "FeatureFlags.java",
+        "FeatureFlagsImpl.java",
+        "CustomFeatureFlags.java",
+        "FakeFeatureFlagsImpl.java",
+    ]
+    .iter()
+    .map(|file| {
+        Ok(OutputFile { contents: template.render(file, &context)?.into(), path: path.join(file) })
+    })
+    .collect::<Result<Vec<OutputFile>>>()
 }
 
 fn gen_flags_by_namespace(flags: &[FlagElement]) -> Vec<NamespaceFlags> {
@@ -292,76 +299,82 @@
         }
     "#;
 
-    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
+    const EXPECTED_CUSTOMFEATUREFLAGS_CONTENT: &str = r#"
     package com.android.aconfig.test;
+
     // TODO(b/303773055): Remove the annotation after access issue is resolved.
     import android.compat.annotation.UnsupportedAppUsage;
     import java.util.Arrays;
-    import java.util.HashMap;
     import java.util.HashSet;
-    import java.util.Map;
+    import java.util.List;
     import java.util.Set;
+    import java.util.function.BiPredicate;
+    import java.util.function.Predicate;
+
     /** @hide */
-    public class FakeFeatureFlagsImpl implements FeatureFlags {
-        public FakeFeatureFlagsImpl() {
-            resetAll();
+    public class CustomFeatureFlags implements FeatureFlags {
+
+        private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+        public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+            mGetValueImpl = getValueImpl;
         }
+
         @Override
         @UnsupportedAppUsage
         public boolean disabledRo() {
-            return getValue(Flags.FLAG_DISABLED_RO);
+            return getValue(Flags.FLAG_DISABLED_RO,
+                    FeatureFlags::disabledRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRw() {
-            return getValue(Flags.FLAG_DISABLED_RW);
+            return getValue(Flags.FLAG_DISABLED_RW,
+                FeatureFlags::disabledRw);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRwExported() {
-            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
+            return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
+                FeatureFlags::disabledRwExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean disabledRwInOtherNamespace() {
-            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
+            return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                FeatureFlags::disabledRwInOtherNamespace);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledFixedRo() {
-            return getValue(Flags.FLAG_ENABLED_FIXED_RO);
+            return getValue(Flags.FLAG_ENABLED_FIXED_RO,
+                FeatureFlags::enabledFixedRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledFixedRoExported() {
-            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
+            return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                FeatureFlags::enabledFixedRoExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRo() {
-            return getValue(Flags.FLAG_ENABLED_RO);
+            return getValue(Flags.FLAG_ENABLED_RO,
+                FeatureFlags::enabledRo);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRoExported() {
-            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
+            return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
+                FeatureFlags::enabledRoExported);
         }
         @Override
         @UnsupportedAppUsage
         public boolean enabledRw() {
-            return getValue(Flags.FLAG_ENABLED_RW);
+            return getValue(Flags.FLAG_ENABLED_RW,
+                FeatureFlags::enabledRw);
         }
-        public void setFlag(String flagName, boolean value) {
-            if (!this.mFlagMap.containsKey(flagName)) {
-                throw new IllegalArgumentException("no such flag " + flagName);
-            }
-            this.mFlagMap.put(flagName, value);
-        }
-        public void resetAll() {
-            for (Map.Entry entry : mFlagMap.entrySet()) {
-                entry.setValue(null);
-            }
-        }
+
         public boolean isFlagReadOnlyOptimized(String flagName) {
             if (mReadOnlyFlagsSet.contains(flagName) &&
                 isOptimizationEnabled()) {
@@ -369,30 +382,30 @@
             }
             return false;
         }
+
         @com.android.aconfig.annotations.AssumeTrueForR8
         private boolean isOptimizationEnabled() {
             return false;
         }
-        private boolean getValue(String flagName) {
-            Boolean value = this.mFlagMap.get(flagName);
-            if (value == null) {
-                throw new IllegalArgumentException(flagName + " is not set");
-            }
-            return value;
+
+        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+            return mGetValueImpl.test(flagName, getter);
         }
-        private Map<String, Boolean> mFlagMap = new HashMap<>(
-            Map.ofEntries(
-                Map.entry(Flags.FLAG_DISABLED_RO, false),
-                Map.entry(Flags.FLAG_DISABLED_RW, false),
-                Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
-                Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
-                Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
-                Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
-                Map.entry(Flags.FLAG_ENABLED_RO, false),
-                Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false),
-                Map.entry(Flags.FLAG_ENABLED_RW, false)
-            )
-        );
+
+        public List<String> getFlagNames() {
+            return Arrays.asList(
+                Flags.FLAG_DISABLED_RO,
+                Flags.FLAG_DISABLED_RW,
+                Flags.FLAG_DISABLED_RW_EXPORTED,
+                Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                Flags.FLAG_ENABLED_FIXED_RO,
+                Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                Flags.FLAG_ENABLED_RO,
+                Flags.FLAG_ENABLED_RO_EXPORTED,
+                Flags.FLAG_ENABLED_RW
+            );
+        }
+
         private Set<String> mReadOnlyFlagsSet = new HashSet<>(
             Arrays.asList(
                 Flags.FLAG_DISABLED_RO,
@@ -406,6 +419,58 @@
     }
     "#;
 
+    const EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT: &str = r#"
+    package com.android.aconfig.test;
+
+    import java.util.HashMap;
+    import java.util.Map;
+    import java.util.function.Predicate;
+
+    /** @hide */
+    public class FakeFeatureFlagsImpl extends CustomFeatureFlags {
+        private final Map<String, Boolean> mFlagMap = new HashMap<>();
+        private final FeatureFlags mDefaults;
+
+        public FakeFeatureFlagsImpl() {
+            this(null);
+        }
+
+        public FakeFeatureFlagsImpl(FeatureFlags defaults) {
+            super(null);
+            mDefaults = defaults;
+            // Initialize the map with null values
+            for (String flagName : getFlagNames()) {
+                mFlagMap.put(flagName, null);
+            }
+        }
+
+        @Override
+        protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+            Boolean value = this.mFlagMap.get(flagName);
+            if (value != null) {
+                return value;
+            }
+            if (mDefaults != null) {
+                return getter.test(mDefaults);
+            }
+            throw new IllegalArgumentException(flagName + " is not set");
+        }
+
+        public void setFlag(String flagName, boolean value) {
+            if (!this.mFlagMap.containsKey(flagName)) {
+                throw new IllegalArgumentException("no such flag " + flagName);
+            }
+            this.mFlagMap.put(flagName, value);
+        }
+
+        public void resetAll() {
+            for (Map.Entry entry : mFlagMap.entrySet()) {
+                entry.setValue(null);
+            }
+        }
+    }
+    "#;
+
     #[test]
     fn test_generate_java_code_production() {
         let parsed_flags = crate::test::parse_test_flags();
@@ -549,6 +614,10 @@
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             ("com/android/aconfig/test/FeatureFlags.java", EXPECTED_FEATUREFLAGS_COMMON_CONTENT),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
                 EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
@@ -671,55 +740,53 @@
             }
         }"#;
 
-        let expect_fake_feature_flags_impl_content = r#"
+        let expect_custom_feature_flags_content = r#"
         package com.android.aconfig.test;
+
         import java.util.Arrays;
-        import java.util.HashMap;
         import java.util.HashSet;
-        import java.util.Map;
+        import java.util.List;
         import java.util.Set;
+        import java.util.function.BiPredicate;
+        import java.util.function.Predicate;
+
         /** @hide */
-        public class FakeFeatureFlagsImpl implements FeatureFlags {
-            public FakeFeatureFlagsImpl() {
-                resetAll();
+        public class CustomFeatureFlags implements FeatureFlags {
+
+            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+                mGetValueImpl = getValueImpl;
             }
+
             @Override
             public boolean disabledRwExported() {
-                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED);
+                return getValue(Flags.FLAG_DISABLED_RW_EXPORTED,
+                    FeatureFlags::disabledRwExported);
             }
             @Override
             public boolean enabledFixedRoExported() {
-                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED);
+                return getValue(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                    FeatureFlags::enabledFixedRoExported);
             }
             @Override
             public boolean enabledRoExported() {
-                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED);
+                return getValue(Flags.FLAG_ENABLED_RO_EXPORTED,
+                    FeatureFlags::enabledRoExported);
             }
-            public void setFlag(String flagName, boolean value) {
-                if (!this.mFlagMap.containsKey(flagName)) {
-                    throw new IllegalArgumentException("no such flag " + flagName);
-                }
-                this.mFlagMap.put(flagName, value);
+
+            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+                return mGetValueImpl.test(flagName, getter);
             }
-            public void resetAll() {
-                for (Map.Entry entry : mFlagMap.entrySet()) {
-                    entry.setValue(null);
-                }
+
+            public List<String> getFlagNames() {
+                return Arrays.asList(
+                    Flags.FLAG_DISABLED_RW_EXPORTED,
+                    Flags.FLAG_ENABLED_FIXED_RO_EXPORTED,
+                    Flags.FLAG_ENABLED_RO_EXPORTED
+                );
             }
-            private boolean getValue(String flagName) {
-                Boolean value = this.mFlagMap.get(flagName);
-                if (value == null) {
-                    throw new IllegalArgumentException(flagName + " is not set");
-                }
-                return value;
-            }
-            private Map<String, Boolean> mFlagMap = new HashMap<>(
-                Map.ofEntries(
-                    Map.entry(Flags.FLAG_DISABLED_RW_EXPORTED, false),
-                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO_EXPORTED, false),
-                    Map.entry(Flags.FLAG_ENABLED_RO_EXPORTED, false)
-                )
-            );
+
             private Set<String> mReadOnlyFlagsSet = new HashSet<>(
                 Arrays.asList(
                     ""
@@ -733,8 +800,12 @@
             ("com/android/aconfig/test/FeatureFlags.java", expect_feature_flags_content),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_feature_flags_impl_content),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                expect_custom_feature_flags_content,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
-                expect_fake_feature_flags_impl_content,
+                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
         ]);
 
@@ -854,6 +925,10 @@
             ("com/android/aconfig/test/FeatureFlags.java", EXPECTED_FEATUREFLAGS_COMMON_CONTENT),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             (
+                "com/android/aconfig/test/CustomFeatureFlags.java",
+                EXPECTED_CUSTOMFEATUREFLAGS_CONTENT,
+            ),
+            (
                 "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
                 EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
             ),
@@ -1020,61 +1095,64 @@
             private static FeatureFlags FEATURE_FLAGS = new FeatureFlagsImpl();
         }"#;
 
-        let expect_fakefeatureflags_content = r#"
+        let expect_customfeatureflags_content = r#"
         package com.android.aconfig.test;
+
         // TODO(b/303773055): Remove the annotation after access issue is resolved.
         import android.compat.annotation.UnsupportedAppUsage;
         import java.util.Arrays;
-        import java.util.HashMap;
         import java.util.HashSet;
-        import java.util.Map;
+        import java.util.List;
         import java.util.Set;
+        import java.util.function.BiPredicate;
+        import java.util.function.Predicate;
+
         /** @hide */
-        public class FakeFeatureFlagsImpl implements FeatureFlags {
-            public FakeFeatureFlagsImpl() {
-                resetAll();
+        public class CustomFeatureFlags implements FeatureFlags {
+
+            private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+            public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) {
+                mGetValueImpl = getValueImpl;
             }
+
             @Override
             @UnsupportedAppUsage
             public boolean disabledRo() {
-                return getValue(Flags.FLAG_DISABLED_RO);
+                return getValue(Flags.FLAG_DISABLED_RO,
+                        FeatureFlags::disabledRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean disabledRw() {
-                return getValue(Flags.FLAG_DISABLED_RW);
+                return getValue(Flags.FLAG_DISABLED_RW,
+                    FeatureFlags::disabledRw);
             }
             @Override
             @UnsupportedAppUsage
             public boolean disabledRwInOtherNamespace() {
-                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE);
+                return getValue(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                    FeatureFlags::disabledRwInOtherNamespace);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledFixedRo() {
-                return getValue(Flags.FLAG_ENABLED_FIXED_RO);
+                return getValue(Flags.FLAG_ENABLED_FIXED_RO,
+                    FeatureFlags::enabledFixedRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledRo() {
-                return getValue(Flags.FLAG_ENABLED_RO);
+                return getValue(Flags.FLAG_ENABLED_RO,
+                    FeatureFlags::enabledRo);
             }
             @Override
             @UnsupportedAppUsage
             public boolean enabledRw() {
-                return getValue(Flags.FLAG_ENABLED_RW);
+                return getValue(Flags.FLAG_ENABLED_RW,
+                    FeatureFlags::enabledRw);
             }
-            public void setFlag(String flagName, boolean value) {
-                if (!this.mFlagMap.containsKey(flagName)) {
-                    throw new IllegalArgumentException("no such flag " + flagName);
-                }
-                this.mFlagMap.put(flagName, value);
-            }
-            public void resetAll() {
-                for (Map.Entry entry : mFlagMap.entrySet()) {
-                    entry.setValue(null);
-                }
-            }
+
             public boolean isFlagReadOnlyOptimized(String flagName) {
                 if (mReadOnlyFlagsSet.contains(flagName) &&
                     isOptimizationEnabled()) {
@@ -1082,27 +1160,27 @@
                 }
                 return false;
             }
+
             @com.android.aconfig.annotations.AssumeTrueForR8
             private boolean isOptimizationEnabled() {
                 return false;
             }
-            private boolean getValue(String flagName) {
-                Boolean value = this.mFlagMap.get(flagName);
-                if (value == null) {
-                    throw new IllegalArgumentException(flagName + " is not set");
-                }
-                return value;
+
+            protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) {
+                return mGetValueImpl.test(flagName, getter);
             }
-            private Map<String, Boolean> mFlagMap = new HashMap<>(
-                Map.ofEntries(
-                    Map.entry(Flags.FLAG_DISABLED_RO, false),
-                    Map.entry(Flags.FLAG_DISABLED_RW, false),
-                    Map.entry(Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE, false),
-                    Map.entry(Flags.FLAG_ENABLED_FIXED_RO, false),
-                    Map.entry(Flags.FLAG_ENABLED_RO, false),
-                    Map.entry(Flags.FLAG_ENABLED_RW, false)
-                )
-            );
+
+            public List<String> getFlagNames() {
+                return Arrays.asList(
+                    Flags.FLAG_DISABLED_RO,
+                    Flags.FLAG_DISABLED_RW,
+                    Flags.FLAG_DISABLED_RW_IN_OTHER_NAMESPACE,
+                    Flags.FLAG_ENABLED_FIXED_RO,
+                    Flags.FLAG_ENABLED_RO,
+                    Flags.FLAG_ENABLED_RW
+                );
+            }
+
             private Set<String> mReadOnlyFlagsSet = new HashSet<>(
                 Arrays.asList(
                     Flags.FLAG_DISABLED_RO,
@@ -1116,11 +1194,16 @@
             );
         }
         "#;
+
         let mut file_set = HashMap::from([
             ("com/android/aconfig/test/Flags.java", expect_flags_content),
             ("com/android/aconfig/test/FeatureFlagsImpl.java", expect_featureflagsimpl_content),
             ("com/android/aconfig/test/FeatureFlags.java", expect_featureflags_content),
-            ("com/android/aconfig/test/FakeFeatureFlagsImpl.java", expect_fakefeatureflags_content),
+            ("com/android/aconfig/test/CustomFeatureFlags.java", expect_customfeatureflags_content),
+            (
+                "com/android/aconfig/test/FakeFeatureFlagsImpl.java",
+                EXPECTED_FAKEFEATUREFLAGSIMPL_CONTENT,
+            ),
         ]);
 
         for file in generated_files {
diff --git a/tools/aconfig/aconfig/src/commands.rs b/tools/aconfig/aconfig/src/commands.rs
index ad96bb8..90b3951 100644
--- a/tools/aconfig/aconfig/src/commands.rs
+++ b/tools/aconfig/aconfig/src/commands.rs
@@ -214,8 +214,8 @@
         bail!("no parsed flags, or the parsed flags use different packages");
     };
     let package = package.to_string();
-    let _flag_ids = assign_flag_ids(&package, modified_parsed_flags.iter())?;
-    generate_cpp_code(&package, modified_parsed_flags.into_iter(), codegen_mode)
+    let flag_ids = assign_flag_ids(&package, modified_parsed_flags.iter())?;
+    generate_cpp_code(&package, modified_parsed_flags.into_iter(), codegen_mode, flag_ids, false)
 }
 
 pub fn create_rust_lib(mut input: Input, codegen_mode: CodegenMode) -> Result<OutputFile> {
diff --git a/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template b/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template
new file mode 100644
index 0000000..b82b9cb
--- /dev/null
+++ b/tools/aconfig/aconfig/templates/CustomFeatureFlags.java.template
@@ -0,0 +1,70 @@
+package {package_name};
+
+{{ if not library_exported- }}
+// TODO(b/303773055): Remove the annotation after access issue is resolved.
+import android.compat.annotation.UnsupportedAppUsage;
+{{ -endif }}
+import java.util.Arrays;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Set;
+import java.util.function.BiPredicate;
+import java.util.function.Predicate;
+
+/** @hide */
+public class CustomFeatureFlags implements FeatureFlags \{
+
+    private BiPredicate<String, Predicate<FeatureFlags>> mGetValueImpl;
+
+    public CustomFeatureFlags(BiPredicate<String, Predicate<FeatureFlags>> getValueImpl) \{
+        mGetValueImpl = getValueImpl;
+    }
+
+{{ -for item in flag_elements}}
+    @Override
+{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
+    public boolean {item.method_name}() \{
+        return getValue(Flags.FLAG_{item.flag_name_constant_suffix},
+            FeatureFlags::{item.method_name});
+    }
+{{ endfor }}
+
+{{ -if not library_exported }}
+    public boolean isFlagReadOnlyOptimized(String flagName) \{
+        if (mReadOnlyFlagsSet.contains(flagName) &&
+            isOptimizationEnabled()) \{
+                return true;
+        }
+        return false;
+    }
+
+    @com.android.aconfig.annotations.AssumeTrueForR8
+    private boolean isOptimizationEnabled() \{
+        return false;
+    }
+{{ -endif }}
+
+    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
+        return mGetValueImpl.test(flagName, getter);
+    }
+
+    public List<String> getFlagNames() \{
+        return Arrays.asList(
+            {{ -for item in flag_elements }}
+            Flags.FLAG_{item.flag_name_constant_suffix}
+            {{ -if not @last }},{{ endif }}
+            {{ -endfor }}
+        );
+    }
+
+    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
+        Arrays.asList(
+            {{ -for item in flag_elements }}
+            {{ -if not item.is_read_write }}
+            Flags.FLAG_{item.flag_name_constant_suffix},
+            {{ -endif }}
+            {{ -endfor }}
+            ""{# The empty string here is to resolve the ending comma #}
+        )
+    );
+}
diff --git a/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template b/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
index 177e711..290d2c4 100644
--- a/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
+++ b/tools/aconfig/aconfig/templates/FakeFeatureFlagsImpl.java.template
@@ -1,27 +1,39 @@
 package {package_name};
-{{ if not library_exported- }}
-// TODO(b/303773055): Remove the annotation after access issue is resolved.
-import android.compat.annotation.UnsupportedAppUsage;
-{{ -endif }}
-import java.util.Arrays;
+
 import java.util.HashMap;
-import java.util.HashSet;
 import java.util.Map;
-import java.util.Set;
+import java.util.function.Predicate;
 
 /** @hide */
-public class FakeFeatureFlagsImpl implements FeatureFlags \{
+public class FakeFeatureFlagsImpl extends CustomFeatureFlags \{
+    private final Map<String, Boolean> mFlagMap = new HashMap<>();
+    private final FeatureFlags mDefaults;
+
     public FakeFeatureFlagsImpl() \{
-        resetAll();
+        this(null);
     }
 
-{{ for item in flag_elements}}
-    @Override
-{{ if not library_exported }}    @UnsupportedAppUsage{{ -endif }}
-    public boolean {item.method_name}() \{
-        return getValue(Flags.FLAG_{item.flag_name_constant_suffix});
+    public FakeFeatureFlagsImpl(FeatureFlags defaults) \{
+        super(null);
+        mDefaults = defaults;
+        // Initialize the map with null values
+        for (String flagName : getFlagNames()) \{
+            mFlagMap.put(flagName, null);
+        }
     }
-{{ endfor}}
+
+    @Override
+    protected boolean getValue(String flagName, Predicate<FeatureFlags> getter) \{
+        Boolean value = this.mFlagMap.get(flagName);
+        if (value != null) \{
+            return value;
+        }
+        if (mDefaults != null) \{
+            return getter.test(mDefaults);
+        }
+        throw new IllegalArgumentException(flagName + " is not set");
+    }
+
     public void setFlag(String flagName, boolean value) \{
         if (!this.mFlagMap.containsKey(flagName)) \{
             throw new IllegalArgumentException("no such flag " + flagName);
@@ -34,46 +46,4 @@
             entry.setValue(null);
         }
     }
-{{ if not library_exported }}
-    public boolean isFlagReadOnlyOptimized(String flagName) \{
-        if (mReadOnlyFlagsSet.contains(flagName) &&
-            isOptimizationEnabled()) \{
-                return true;
-        }
-        return false;
-    }
-
-    @com.android.aconfig.annotations.AssumeTrueForR8
-    private boolean isOptimizationEnabled() \{
-        return false;
-    }
-{{ -endif }}
-    private boolean getValue(String flagName) \{
-        Boolean value = this.mFlagMap.get(flagName);
-        if (value == null) \{
-            throw new IllegalArgumentException(flagName + " is not set");
-        }
-        return value;
-    }
-
-
-    private Map<String, Boolean> mFlagMap = new HashMap<>(
-        Map.ofEntries(
-            {{ -for item in flag_elements }}
-            Map.entry(Flags.FLAG_{item.flag_name_constant_suffix}, false)
-            {{ -if not @last }},{{ endif }}
-            {{ -endfor }}
-        )
-    );
-
-    private Set<String> mReadOnlyFlagsSet = new HashSet<>(
-        Arrays.asList(
-            {{ -for item in flag_elements }}
-            {{ -if not item.is_read_write }}
-            Flags.FLAG_{item.flag_name_constant_suffix},
-            {{ -endif }}
-            {{ -endfor }}
-            ""{# The empty string here is to resolve the ending comma #}
-        )
-    );
 }
diff --git a/tools/aconfig/aconfig/templates/cpp_source_file.template b/tools/aconfig/aconfig/templates/cpp_source_file.template
index 4bcd1b7..7646015 100644
--- a/tools/aconfig/aconfig/templates/cpp_source_file.template
+++ b/tools/aconfig/aconfig/templates/cpp_source_file.template
@@ -1,5 +1,16 @@
 #include "{header}.h"
 
+{{ if allow_instrumentation }}
+#include <sys/stat.h>
+#include "aconfig_storage/aconfig_storage_read_api.hpp"
+#include <protos/aconfig_storage_metadata.pb.h>
+#include <android/log.h>
+
+#define ALOGI(msg, ...)                                                        \
+  __android_log_print(ANDROID_LOG_INFO, "AconfigTestMission1", (msg), __VA_ARGS__)
+
+{{ endif }}
+
 {{ if readwrite- }}
 #include <server_configurable_flags/get_flags.h>
 {{ endif }}
@@ -97,6 +108,58 @@
     {{ -if item.readwrite }}
     return {cpp_namespace}::{item.flag_name}();
     {{ -else }}
+    {{ if allow_instrumentation }}
+    auto result =
+        {{ if item.is_fixed_read_only }}
+	    {package_macro}_{item.flag_macro}
+	{{ else }}
+	    {item.default_value}
+	{{ endif }};
+
+    struct stat buffer;
+    if (stat("/metadata/aconfig_test_missions/mission_1", &buffer) != 0) \{
+        return result;
+    }
+
+    auto package_map_file = aconfig_storage::get_mapped_file(
+        "{item.container}",
+        aconfig_storage::StorageFileType::package_map);
+    if (!package_map_file.ok()) \{
+        ALOGI("error: failed to get package map file: %s", package_map_file.error().message().c_str());
+        return result;
+    }
+
+    auto package_read_context = aconfig_storage::get_package_read_context(
+        *package_map_file, "{package}");
+    if (!package_read_context.ok()) \{
+        ALOGI("error: failed to get package read context: %s", package_map_file.error().message().c_str());
+        return result;
+    }
+
+    auto flag_val_map = aconfig_storage::get_mapped_file(
+        "{item.container}",
+        aconfig_storage::StorageFileType::flag_val);
+    if (!flag_val_map.ok()) \{
+        ALOGI("error: failed to get flag val map: %s", package_map_file.error().message().c_str());
+        return result;
+    }
+
+    auto value = aconfig_storage::get_boolean_flag_value(
+        *flag_val_map,
+        package_read_context->package_id + {item.flag_offset});
+    if (!value.ok()) \{
+        ALOGI("error: failed to get flag val: %s", package_map_file.error().message().c_str());
+        return result;
+    }
+
+    if (*value != result) \{
+        ALOGI("error: new storage value '%d' does not match current value '%d'", *value, result);
+    } else \{
+        ALOGI("success: new storage value was '%d, legacy storage was '%d'", *value, result);
+    }
+
+    return result;
+    {{ else }}
     {{ -if item.is_fixed_read_only }}
     return {package_macro}_{item.flag_macro};
     {{ -else }}
@@ -104,6 +167,7 @@
     {{ -endif }}
     {{ -endif }}
     {{ -endif }}
+    {{ -endif }}
 }
 
 {{ -if is_test_mode }}
@@ -119,3 +183,4 @@
 }
 {{ -endif }}
 
+
diff --git a/tools/aconfig/aconfig_storage_read_api/Android.bp b/tools/aconfig/aconfig_storage_read_api/Android.bp
index 946c00b..c89107f 100644
--- a/tools/aconfig/aconfig_storage_read_api/Android.bp
+++ b/tools/aconfig/aconfig_storage_read_api/Android.bp
@@ -102,8 +102,10 @@
         "//apex_available:anyapex",
     ],
     min_sdk_version: "29",
+    target: {
+        linux: {
+            version_script: "libaconfig_storage_read_api_cc.map",
+        },
+    },
     double_loadable: true,
-    cflags: [
-        "-fvisibility=hidden",
-    ],
 }
diff --git a/tools/aconfig/aconfig_storage_read_api/libaconfig_storage_read_api_cc.map b/tools/aconfig/aconfig_storage_read_api/libaconfig_storage_read_api_cc.map
new file mode 100644
index 0000000..7d47e0b
--- /dev/null
+++ b/tools/aconfig/aconfig_storage_read_api/libaconfig_storage_read_api_cc.map
@@ -0,0 +1,11 @@
+LIBACONFIG_STORAGE_READ_API_CC {
+  # Export everything in the aconfig_storage namespace. This includes both the
+  # public API and library internals.
+  global:
+    extern "C++" {
+        aconfig_storage::*;
+    };
+  # Hide everything else.
+  local:
+    *;
+};
diff --git a/tools/tool_event_logger/Android.bp b/tools/tool_event_logger/Android.bp
new file mode 100644
index 0000000..7a1d2aa
--- /dev/null
+++ b/tools/tool_event_logger/Android.bp
@@ -0,0 +1,67 @@
+// Copyright 2024 The Android Open Source Project
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Set of error prone rules to ensure code quality
+// PackageLocation check requires the androidCompatible=false otherwise it does not do anything.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+    default_team: "trendy_team_adte",
+}
+
+python_library_host {
+    name: "tool_event_proto",
+    srcs: [
+        "proto/tool_event.proto",
+    ],
+    proto: {
+        canonical_path_from_root: false,
+    },
+}
+
+python_binary_host {
+    name: "tool_event_logger",
+    pkg_path: "tool_event_logger",
+    srcs: [
+        "tool_event_logger.py",
+    ],
+    libs: [
+        "asuite_cc_client",
+        "tool_event_proto",
+    ],
+    main: "tool_event_logger.py",
+}
+
+python_test_host {
+    name: "tool_event_logger_test",
+    main: "tool_event_logger_test.py",
+    pkg_path: "tool_event_logger",
+    srcs: [
+        "tool_event_logger.py",
+        "tool_event_logger_test.py",
+    ],
+    test_options: {
+        unit_test: true,
+    },
+    libs: [
+        "asuite_cc_client",
+        "tool_event_proto",
+    ],
+    version: {
+        py3: {
+            embedded_launcher: true,
+            enabled: true,
+        },
+    },
+}
diff --git a/tools/tool_event_logger/OWNERS b/tools/tool_event_logger/OWNERS
new file mode 100644
index 0000000..b692c9e
--- /dev/null
+++ b/tools/tool_event_logger/OWNERS
@@ -0,0 +1,4 @@
+include platform/tools/asuite:/OWNERS
+
+zhuoyao@google.com
+hzalek@google.com
\ No newline at end of file
diff --git a/tools/tool_event_logger/proto/tool_event.proto b/tools/tool_event_logger/proto/tool_event.proto
new file mode 100644
index 0000000..61e28a2
--- /dev/null
+++ b/tools/tool_event_logger/proto/tool_event.proto
@@ -0,0 +1,35 @@
+syntax = "proto3";
+
+package tools.asuite.tool_event_logger;
+
+message ToolEvent {
+  // Occurs immediately upon execution of the tool.
+  message InvocationStarted {
+    string command_args = 1;
+    string cwd = 2;
+    string os = 3;
+  }
+
+  // Occurs when tool exits for any reason.
+  message InvocationStopped {
+    int32 exit_code = 2;
+    string exit_log = 3;
+  }
+
+  // ------------------------
+  // FIELDS FOR ToolEvent
+  // ------------------------
+  // Random string generated to identify the invocation.
+  string invocation_id = 1;
+  // Internal user name.
+  string user_name = 2;
+  // The root of Android source.
+  string source_root = 3;
+  // Name of the tool used.
+  string tool_tag = 6;
+
+  oneof event {
+    InvocationStarted invocation_started = 4;
+    InvocationStopped invocation_stopped = 5;
+  }
+}
diff --git a/tools/tool_event_logger/tool_event_logger.py b/tools/tool_event_logger/tool_event_logger.py
new file mode 100644
index 0000000..65a9696
--- /dev/null
+++ b/tools/tool_event_logger/tool_event_logger.py
@@ -0,0 +1,229 @@
+# Copyright 2024, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+
+import argparse
+import datetime
+import getpass
+import logging
+import os
+import platform
+import sys
+import tempfile
+import uuid
+
+from atest.metrics import clearcut_client
+from atest.proto import clientanalytics_pb2
+from proto import tool_event_pb2
+
+LOG_SOURCE = 2395
+
+
+class ToolEventLogger:
+  """Logs tool events to Sawmill through Clearcut."""
+
+  def __init__(
+      self,
+      tool_tag: str,
+      invocation_id: str,
+      user_name: str,
+      source_root: str,
+      platform_version: str,
+      python_version: str,
+      client: clearcut_client.Clearcut,
+  ):
+    self.tool_tag = tool_tag
+    self.invocation_id = invocation_id
+    self.user_name = user_name
+    self.source_root = source_root
+    self.platform_version = platform_version
+    self.python_version = python_version
+    self._clearcut_client = client
+
+  @classmethod
+  def create(cls, tool_tag: str):
+    return ToolEventLogger(
+        tool_tag=tool_tag,
+        invocation_id=str(uuid.uuid4()),
+        user_name=getpass.getuser(),
+        source_root=os.environ.get('ANDROID_BUILD_TOP', ''),
+        platform_version=platform.platform(),
+        python_version=platform.python_version(),
+        client=clearcut_client.Clearcut(LOG_SOURCE),
+    )
+
+  def __enter__(self):
+    return self
+
+  def __exit__(self, exc_type, exc_val, exc_tb):
+    self.flush()
+
+  def log_invocation_started(self, event_time: datetime, command_args: str):
+    """Creates an event log with invocation started info."""
+    event = self._create_tool_event()
+    event.invocation_started.CopyFrom(
+        tool_event_pb2.ToolEvent.InvocationStarted(
+            command_args=command_args,
+            os=f'{self.platform_version}:{self.python_version}',
+        )
+    )
+
+    logging.debug('Log invocation_started: %s', event)
+    self._log_clearcut_event(event, event_time)
+
+  def log_invocation_stopped(
+      self,
+      event_time: datetime,
+      exit_code: int,
+      exit_log: str,
+  ):
+    """Creates an event log with invocation stopped info."""
+    event = self._create_tool_event()
+    event.invocation_stopped.CopyFrom(
+        tool_event_pb2.ToolEvent.InvocationStopped(
+            exit_code=exit_code,
+            exit_log=exit_log,
+        )
+    )
+
+    logging.debug('Log invocation_stopped: %s', event)
+    self._log_clearcut_event(event, event_time)
+
+  def flush(self):
+    """Sends all batched events to Clearcut."""
+    logging.debug('Sending events to Clearcut.')
+    self._clearcut_client.flush_events()
+
+  def _create_tool_event(self):
+    return tool_event_pb2.ToolEvent(
+        tool_tag=self.tool_tag,
+        invocation_id=self.invocation_id,
+        user_name=self.user_name,
+        source_root=self.source_root,
+    )
+
+  def _log_clearcut_event(
+      self, tool_event: tool_event_pb2.ToolEvent, event_time: datetime
+  ):
+    log_event = clientanalytics_pb2.LogEvent(
+        event_time_ms=int(event_time.timestamp() * 1000),
+        source_extension=tool_event.SerializeToString(),
+    )
+    self._clearcut_client.log(log_event)
+
+
+class ArgumentParserWithLogging(argparse.ArgumentParser):
+
+  def error(self, message):
+    logging.error('Failed to parse args with error: %s', message)
+    super().error(message)
+
+
+def create_arg_parser():
+  """Creates an instance of the default ToolEventLogger arg parser."""
+
+  parser = ArgumentParserWithLogging(
+      description='Build and upload logs for Android dev tools',
+      add_help=True,
+      formatter_class=argparse.RawDescriptionHelpFormatter,
+  )
+
+  parser.add_argument(
+      '--tool_tag',
+      type=str,
+      required=True,
+      help='Name of the tool.',
+  )
+
+  parser.add_argument(
+      '--start_timestamp',
+      type=lambda ts: datetime.datetime.fromtimestamp(float(ts)),
+      required=True,
+      help=(
+          'Timestamp when the tool starts. The timestamp should have the format'
+          '%s.%N which represents the seconds elapses since epoch.'
+      ),
+  )
+
+  parser.add_argument(
+      '--end_timestamp',
+      type=lambda ts: datetime.datetime.fromtimestamp(float(ts)),
+      required=True,
+      help=(
+          'Timestamp when the tool exits. The timestamp should have the format'
+          '%s.%N which represents the seconds elapses since epoch.'
+      ),
+  )
+
+  parser.add_argument(
+      '--tool_args',
+      type=str,
+      help='Parameters that are passed to the tool.',
+  )
+
+  parser.add_argument(
+      '--exit_code',
+      type=int,
+      required=True,
+      help='Tool exit code.',
+  )
+
+  parser.add_argument(
+      '--exit_log',
+      type=str,
+      help='Logs when tool exits.',
+  )
+
+  parser.add_argument(
+      '--dry_run',
+      action='store_true',
+      help='Dry run the tool event logger if set.',
+  )
+
+  return parser
+
+
+def configure_logging():
+  root_logging_dir = tempfile.mkdtemp(prefix='tool_event_logger_')
+
+  log_fmt = '%(asctime)s %(filename)s:%(lineno)s:%(levelname)s: %(message)s'
+  date_fmt = '%Y-%m-%d %H:%M:%S'
+  _, log_path = tempfile.mkstemp(dir=root_logging_dir, suffix='.log')
+
+  logging.basicConfig(
+      filename=log_path, level=logging.DEBUG, format=log_fmt, datefmt=date_fmt
+  )
+
+
+def main(argv: list[str]):
+  args = create_arg_parser().parse_args(argv[1:])
+
+  if args.dry_run:
+    logging.debug('This is a dry run.')
+    return
+
+  try:
+    with ToolEventLogger.create(args.tool_tag) as logger:
+      logger.log_invocation_started(args.start_timestamp, args.tool_args)
+      logger.log_invocation_stopped(
+          args.end_timestamp, args.exit_code, args.exit_log
+      )
+  except Exception as e:
+    logging.error('Log failed with unexpected error: %s', e)
+    raise
+
+
+if __name__ == '__main__':
+  configure_logging()
+  main(sys.argv)
diff --git a/tools/tool_event_logger/tool_event_logger_test.py b/tools/tool_event_logger/tool_event_logger_test.py
new file mode 100644
index 0000000..34b6c35
--- /dev/null
+++ b/tools/tool_event_logger/tool_event_logger_test.py
@@ -0,0 +1,209 @@
+# Copyright 2024, The Android Open Source Project
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unittests for ToolEventLogger."""
+
+import datetime
+import logging
+import unittest
+from unittest import mock
+
+from atest.metrics import clearcut_client
+from proto import tool_event_pb2
+from tool_event_logger import tool_event_logger
+
+TEST_INVOCATION_ID = 'test_invocation_id'
+TEST_USER_NAME = 'test_user'
+TEST_TOOL_TAG = 'test_tool'
+TEST_SOURCE_ROOT = 'test_source_root'
+TEST_PLATFORM_VERSION = 'test_platform_version'
+TEST_PYTHON_VERSION = 'test_python_version'
+TEST_EVENT_TIMESTAMP = datetime.datetime.now()
+
+
+class ToolEventLoggerTest(unittest.TestCase):
+
+  def setUp(self):
+    super().setUp()
+    self.clearcut_client = FakeClearcutClient()
+    self.logger = tool_event_logger.ToolEventLogger(
+        TEST_TOOL_TAG,
+        TEST_INVOCATION_ID,
+        TEST_USER_NAME,
+        TEST_SOURCE_ROOT,
+        TEST_PLATFORM_VERSION,
+        TEST_PYTHON_VERSION,
+        client=self.clearcut_client,
+    )
+
+  def test_log_event_timestamp(self):
+    with self.logger:
+      self.logger.log_invocation_started(
+          datetime.datetime.fromtimestamp(100.101), 'test_command'
+      )
+
+    self.assertEqual(
+        self.clearcut_client.get_last_sent_event().event_time_ms, 100101
+    )
+
+  def test_log_event_basic_information(self):
+    with self.logger:
+      self.logger.log_invocation_started(TEST_EVENT_TIMESTAMP, 'test_command')
+
+    sent_event = self.clearcut_client.get_last_sent_event()
+    log_event = tool_event_pb2.ToolEvent.FromString(sent_event.source_extension)
+    self.assertEqual(log_event.invocation_id, TEST_INVOCATION_ID)
+    self.assertEqual(log_event.user_name, TEST_USER_NAME)
+    self.assertEqual(log_event.tool_tag, TEST_TOOL_TAG)
+    self.assertEqual(log_event.source_root, TEST_SOURCE_ROOT)
+
+  def test_log_invocation_started(self):
+    expected_invocation_started = tool_event_pb2.ToolEvent.InvocationStarted(
+        command_args='test_command',
+        os=TEST_PLATFORM_VERSION + ':' + TEST_PYTHON_VERSION,
+    )
+
+    with self.logger:
+      self.logger.log_invocation_started(TEST_EVENT_TIMESTAMP, 'test_command')
+
+    self.assertEqual(self.clearcut_client.get_number_of_sent_events(), 1)
+    sent_event = self.clearcut_client.get_last_sent_event()
+    self.assertEqual(
+        expected_invocation_started,
+        tool_event_pb2.ToolEvent.FromString(
+            sent_event.source_extension
+        ).invocation_started,
+    )
+
+  def test_log_invocation_stopped(self):
+    expected_invocation_stopped = tool_event_pb2.ToolEvent.InvocationStopped(
+        exit_code=0,
+        exit_log='exit_log',
+    )
+
+    with self.logger:
+      self.logger.log_invocation_stopped(TEST_EVENT_TIMESTAMP, 0, 'exit_log')
+
+    self.assertEqual(self.clearcut_client.get_number_of_sent_events(), 1)
+    sent_event = self.clearcut_client.get_last_sent_event()
+    self.assertEqual(
+        expected_invocation_stopped,
+        tool_event_pb2.ToolEvent.FromString(
+            sent_event.source_extension
+        ).invocation_stopped,
+    )
+
+  def test_log_multiple_events(self):
+    with self.logger:
+      self.logger.log_invocation_started(TEST_EVENT_TIMESTAMP, 'test_command')
+      self.logger.log_invocation_stopped(TEST_EVENT_TIMESTAMP, 0, 'exit_log')
+
+    self.assertEqual(self.clearcut_client.get_number_of_sent_events(), 2)
+
+
+class MainTest(unittest.TestCase):
+
+  REQUIRED_ARGS = [
+      '',
+      '--tool_tag',
+      'test_tool',
+      '--start_timestamp',
+      '1',
+      '--end_timestamp',
+      '2',
+      '--exit_code',
+      '0',
+  ]
+
+  def test_log_and_exit_with_missing_required_args(self):
+    with self.assertLogs() as logs:
+      with self.assertRaises(SystemExit) as ex:
+        tool_event_logger.main(['', '--tool_tag', 'test_tool'])
+
+    with self.subTest('Verify exception code'):
+      self.assertEqual(ex.exception.code, 2)
+
+    with self.subTest('Verify log messages'):
+      self.assertIn(
+          'the following arguments are required',
+          '\n'.join(logs.output),
+      )
+
+  def test_log_and_exit_with_invalid_args(self):
+    with self.assertLogs() as logs:
+      with self.assertRaises(SystemExit) as ex:
+        tool_event_logger.main(['', '--start_timestamp', 'test'])
+
+    with self.subTest('Verify exception code'):
+      self.assertEqual(ex.exception.code, 2)
+
+    with self.subTest('Verify log messages'):
+      self.assertIn(
+          '--start_timestamp: invalid',
+          '\n'.join(logs.output),
+      )
+
+  def test_log_and_exit_with_dry_run(self):
+    with self.assertLogs(level=logging.DEBUG) as logs:
+      tool_event_logger.main(self.REQUIRED_ARGS + ['--dry_run'])
+
+    with self.subTest('Verify log messages'):
+      self.assertIn('dry run', '\n'.join(logs.output))
+
+  @mock.patch.object(clearcut_client, 'Clearcut')
+  def test_log_and_exit_with_unexpected_exception(self, mock_cc):
+    mock_cc.return_value = FakeClearcutClient(raise_log_exception=True)
+
+    with self.assertLogs() as logs:
+      with self.assertRaises(Exception) as ex:
+        tool_event_logger.main(self.REQUIRED_ARGS)
+
+    with self.subTest('Verify log messages'):
+      self.assertIn('unexpected error', '\n'.join(logs.output))
+
+  @mock.patch.object(clearcut_client, 'Clearcut')
+  def test_success(self, mock_cc):
+    mock_clear_cut_client = FakeClearcutClient()
+    mock_cc.return_value = mock_clear_cut_client
+
+    tool_event_logger.main(self.REQUIRED_ARGS)
+
+    self.assertEqual(mock_clear_cut_client.get_number_of_sent_events(), 2)
+
+
+class FakeClearcutClient:
+
+  def __init__(self, raise_log_exception=False):
+    self.pending_log_events = []
+    self.sent_log_events = []
+    self.raise_log_exception = raise_log_exception
+
+  def log(self, log_event):
+    if self.raise_log_exception:
+      raise Exception('unknown exception')
+    self.pending_log_events.append(log_event)
+
+  def flush_events(self):
+    self.sent_log_events.extend(self.pending_log_events)
+    self.pending_log_events.clear()
+
+  def get_number_of_sent_events(self):
+    return len(self.sent_log_events)
+
+  def get_last_sent_event(self):
+    return self.sent_log_events[-1]
+
+
+if __name__ == '__main__':
+  unittest.main()