diff --git a/src/Playground.res b/src/Playground.res
index 24b582cfd..4ae260543 100644
--- a/src/Playground.res
+++ b/src/Playground.res
@@ -902,9 +902,19 @@ module Settings = {
 
     let onResetClick = evt => {
       ReactEvent.Mouse.preventDefault(evt)
+
+      let open_modules = switch readyState.selected.apiVersion {
+      | V1 | V2 | V3 | UnknownVersion(_) => None
+      | V4 =>
+        readyState.selected.libraries->Belt.Array.some(el => el === "@rescript/core")
+          ? Some(["RescriptCore"])
+          : None
+      }
+
       let defaultConfig = {
         Api.Config.module_system: "nodejs",
         warn_flags: "+a-4-9-20-40-41-42-50-61-102-109",
+        ?open_modules,
       }
       setConfig(defaultConfig)
     }
diff --git a/src/bindings/RescriptCompilerApi.res b/src/bindings/RescriptCompilerApi.res
index faf569599..eef8c3550 100644
--- a/src/bindings/RescriptCompilerApi.res
+++ b/src/bindings/RescriptCompilerApi.res
@@ -36,6 +36,7 @@ module Version = {
     | V1
     | V2
     | V3
+    | V4
     | UnknownVersion(string)
 
   // Helps finding the right API version
@@ -57,6 +58,7 @@ module Version = {
       }
     | list{"2"} => V2
     | list{"3"} => V3
+    | list{"4"} => V4
     | _ => UnknownVersion(apiVersion)
     }
 
@@ -65,6 +67,7 @@ module Version = {
     | V1 => "1.0"
     | V2 => "2.0"
     | V3 => "3.0"
+    | V4 => "4.0"
     | UnknownVersion(version) => version
     }
 
@@ -73,7 +76,7 @@ module Version = {
   let availableLanguages = t =>
     switch t {
     | V1 => [Lang.Reason, Res]
-    | V2 | V3 => [Lang.Res]
+    | V2 | V3 | V4 => [Lang.Res]
     | UnknownVersion(_) => [Res]
     }
 }
@@ -348,6 +351,7 @@ module Config = {
     module_system: string,
     warn_flags: string,
     uncurried?: bool,
+    open_modules?: array<string>,
   }
 }
 
@@ -423,6 +427,8 @@ module Compiler = {
 
   @send external setWarnFlags: (t, string) => bool = "setWarnFlags"
 
+  @send external setOpenModules: (t, array<string>) => bool = "setOpenModules"
+
   let setConfig = (t: t, config: Config.t): unit => {
     let moduleSystem = switch config.module_system {
     | "nodejs" => #nodejs->Some
@@ -431,6 +437,7 @@ module Compiler = {
     }
 
     Belt.Option.forEach(moduleSystem, moduleSystem => t->setModuleSystem(moduleSystem)->ignore)
+    Belt.Option.forEach(config.open_modules, modules => t->setOpenModules(modules)->ignore)
 
     t->setWarnFlags(config.warn_flags)->ignore
   }
diff --git a/src/bindings/RescriptCompilerApi.resi b/src/bindings/RescriptCompilerApi.resi
index f6742488c..cfb3065aa 100644
--- a/src/bindings/RescriptCompilerApi.resi
+++ b/src/bindings/RescriptCompilerApi.resi
@@ -24,6 +24,7 @@ module Version: {
     | V1
     | V2
     | V3
+    | V4
     | UnknownVersion(string)
 
   // Helps finding the right API version
@@ -159,6 +160,7 @@ module Config: {
     warn_flags: string,
     /** Only available in apiVersion > 3 (= ReScript 11+) */
     uncurried?: bool,
+    open_modules?: array<string>,
   }
 }
 
@@ -197,6 +199,7 @@ module Compiler: {
   let setModuleSystem: (t, [#es6 | #nodejs]) => bool
 
   let setWarnFlags: (t, string) => bool
+  let setOpenModules: (t, array<string>) => bool
   let setConfig: (t, Config.t) => unit
 
   // General format function
diff --git a/src/common/CompilerManagerHook.res b/src/common/CompilerManagerHook.res
index 65e745f06..fb50d3cbd 100644
--- a/src/common/CompilerManagerHook.res
+++ b/src/common/CompilerManagerHook.res
@@ -145,6 +145,12 @@ let getLibrariesForVersion = (~version: Semver.t): array<string> => {
   libraries
 }
 
+let getOpenModules = (~apiVersion: Version.t, ~libraries: array<string>): option<array<string>> =>
+  switch apiVersion {
+  | V1 | V2 | V3 | UnknownVersion(_) => None
+  | V4 => libraries->Belt.Array.some(el => el === "@rescript/core") ? Some(["RescriptCore"]) : None
+  }
+
 /*
     This function loads the compiler, plus a defined set of libraries that are available
     on our bs-platform-js-releases channel.
@@ -396,6 +402,7 @@ let useCompilerManager = (
             | Ok() =>
               let instance = Compiler.make()
               let apiVersion = apiVersion->Version.fromString
+              let open_modules = getOpenModules(~apiVersion, ~libraries)
 
               // Note: The compiler bundle currently defaults to
               // commonjs when initiating the compiler, but our playground
@@ -405,6 +412,7 @@ let useCompilerManager = (
               let config = {
                 ...instance->Compiler.getConfig,
                 module_system: "es6",
+                ?open_modules,
               }
               instance->Compiler.setConfig(config)
 
@@ -453,7 +461,10 @@ let useCompilerManager = (
 
           let instance = Compiler.make()
           let apiVersion = apiVersion->Version.fromString
-          let config = instance->Compiler.getConfig
+          let open_modules = getOpenModules(~apiVersion, ~libraries)
+
+          let config = {...instance->Compiler.getConfig, ?open_modules}
+          instance->Compiler.setConfig(config)
 
           let selected = {
             id: version,
@@ -488,7 +499,7 @@ let useCompilerManager = (
           | Lang.Reason => instance->Compiler.reasonCompile(code)
           | Lang.Res => instance->Compiler.resCompile(code)
           }
-        | V2 | V3 =>
+        | V2 | V3 | V4 =>
           switch lang {
           | Lang.OCaml => instance->Compiler.ocamlCompile(code)
           | Lang.Reason =>