diff --git a/crates/els/server.rs b/crates/els/server.rs
index b66f8983..9868601c 100644
--- a/crates/els/server.rs
+++ b/crates/els/server.rs
@@ -276,29 +276,30 @@ impl<Checker: BuildRunnable, Parser: Parsable> Server<Checker, Parser> {
             lsp_log!("packages must be an array: {pkgs}");
             return cfg;
         };
+        let mut packages = vec![];
         for rec in arr.iter() {
             let ast::Expr::Record(rec) = rec else {
                 lsp_log!("packages must be records: {rec}");
-                return cfg;
+                break;
             };
             let Some(ast::Expr::Literal(name)) =
                 rec.get("name").and_then(|name| name.body.block.first())
             else {
-                return cfg;
+                break;
             };
             let name = name.token.content.replace('\"', "");
             let Some(ast::Expr::Literal(as_name)) = rec
                 .get("as_name")
                 .and_then(|as_name| as_name.body.block.first())
             else {
-                return cfg;
+                break;
             };
             let as_name = as_name.token.content.replace('\"', "");
             let Some(ast::Expr::Literal(version)) = rec
                 .get("version")
                 .and_then(|version| version.body.block.first())
             else {
-                return cfg;
+                break;
             };
             let version = version.token.content.replace('\"', "");
             let path = rec.get("path").and_then(|path| {
@@ -314,8 +315,9 @@ impl<Checker: BuildRunnable, Parser: Parsable> Server<Checker, Parser> {
                 version.leak(),
                 path.map(|p| &*p.leak()),
             );
-            cfg.packages.push(package);
+            packages.push(package);
         }
+        cfg.packages = Arc::from(packages);
         cfg
     }
 
diff --git a/crates/erg_common/config.rs b/crates/erg_common/config.rs
index 6ad746a8..7307ab78 100644
--- a/crates/erg_common/config.rs
+++ b/crates/erg_common/config.rs
@@ -14,6 +14,7 @@ use crate::levenshtein::get_similar_name;
 use crate::normalize_path;
 use crate::python_util::{detect_magic_number, get_python_version, PythonVersion};
 use crate::serialize::{get_magic_num_from_bytes, get_ver_from_magic_num};
+use crate::ArcArray;
 
 #[cfg(not(feature = "pylib"))]
 use erg_proc_macros::{new, pyclass, pymethods};
@@ -167,8 +168,8 @@ pub struct ErgConfig {
     /// needed for `jupyter-erg`
     pub ps1: &'static str,
     pub ps2: &'static str,
-    pub runtime_args: Vec<&'static str>,
-    pub packages: Vec<Package>,
+    pub runtime_args: ArcArray<&'static str>,
+    pub packages: ArcArray<Package>,
     pub effect_check: bool,
     pub ownership_check: bool,
 }
@@ -194,8 +195,8 @@ impl Default for ErgConfig {
             verbose: 1,
             ps1: ">>> ",
             ps2: "... ",
-            runtime_args: vec![],
-            packages: vec![],
+            runtime_args: ArcArray::from([]),
+            packages: ArcArray::from([]),
             effect_check: true,
             ownership_check: true,
         }
@@ -269,13 +270,15 @@ impl ErgConfig {
         let mut args = env::args();
         args.next(); // "ergc"
         let mut cfg = Self::default();
+        let mut runtime_args: Vec<&'static str> = vec![];
+        let mut packages = vec![];
         // not `for` because we need to consume the next argument
         while let Some(arg) = args.next() {
             match &arg[..] {
                 /* Options */
                 "--" => {
                     for arg in args {
-                        cfg.runtime_args.push(Box::leak(arg.into_boxed_str()));
+                        runtime_args.push(Box::leak(arg.into_boxed_str()));
                     }
                     break;
                 }
@@ -332,7 +335,7 @@ impl ErgConfig {
                         .next()
                         .expect("`version` of `--use-package` is not passed")
                         .into_boxed_str();
-                    cfg.packages.push(Package::new(
+                    packages.push(Package::new(
                         Box::leak(name),
                         Box::leak(as_name),
                         Box::leak(version),
@@ -356,7 +359,7 @@ impl ErgConfig {
                         .next()
                         .expect("`path` of `--use-package` is not passed")
                         .into_boxed_str();
-                    cfg.packages.push(Package::new(
+                    packages.push(Package::new(
                         Box::leak(name),
                         Box::leak(as_name),
                         Box::leak(version),
@@ -505,7 +508,7 @@ USAGE:
                         cfg.mode = mode;
                         if cfg.mode == ErgMode::Pack {
                             for arg in args {
-                                cfg.runtime_args.push(Box::leak(arg.into_boxed_str()));
+                                runtime_args.push(Box::leak(arg.into_boxed_str()));
                             }
                             break;
                         }
@@ -517,7 +520,7 @@ USAGE:
                         match args.next().as_ref().map(|s| &s[..]) {
                             Some("--") => {
                                 for arg in args {
-                                    cfg.runtime_args.push(Box::leak(arg.into_boxed_str()));
+                                    runtime_args.push(Box::leak(arg.into_boxed_str()));
                                 }
                             }
                             Some(some) => {
@@ -543,6 +546,8 @@ USAGE:
             };
             cfg.input = input;
         }
+        cfg.runtime_args = ArcArray::from(runtime_args);
+        cfg.packages = ArcArray::from(packages);
         cfg
     }
 }
diff --git a/crates/erg_compiler/lib.rs b/crates/erg_compiler/lib.rs
index b955a1f5..159179d4 100644
--- a/crates/erg_compiler/lib.rs
+++ b/crates/erg_compiler/lib.rs
@@ -57,7 +57,7 @@ impl _Compiler {
     #[new]
     fn new(deps: Vec<Package>) -> Self {
         let cfg = ErgConfig {
-            packages: deps,
+            packages: erg_common::ArcArray::from(deps),
             ..ErgConfig::default()
         };
         Self {
diff --git a/src/dummy.rs b/src/dummy.rs
index cb65d8e8..1554c9b5 100644
--- a/src/dummy.rs
+++ b/src/dummy.rs
@@ -448,7 +448,7 @@ impl PackageManagerRunner {
             .stdin(Stdio::inherit())
             .stdout(Stdio::inherit())
             .stderr(Stdio::inherit())
-            .args(&cfg.runtime_args)
+            .args(cfg.runtime_args.as_ref())
             .output()
         {
             Ok(out) => ExitStatus::new(out.status.code().unwrap_or(0), 0, 0),