diff --git a/.gitignore b/.gitignore
index f785edf..f3c38b8 100644
--- a/.gitignore
+++ b/.gitignore
@@ -133,3 +133,6 @@ dist/
 
 # Temp files
 tmp/
+
+# Run on change hash cache
+.runOnChanged.hashes.json
diff --git a/packages/engine-chronocat-api/package.json b/packages/engine-chronocat-api/package.json
index b2ea601..e9507a4 100644
--- a/packages/engine-chronocat-api/package.json
+++ b/packages/engine-chronocat-api/package.json
@@ -14,7 +14,7 @@
     "lib"
   ],
   "scripts": {
-    "build": "concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
+    "build": "node -r esbuild-register ../../scripts/runOnChanged.cts ./src concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
     "build:cjs": "node -r esbuild-register ../../scripts/build.cts",
     "build:dts": "tsc -p tsconfig.json"
   },
diff --git a/packages/engine-chronocat-event/package.json b/packages/engine-chronocat-event/package.json
index 7362136..22d7a10 100644
--- a/packages/engine-chronocat-event/package.json
+++ b/packages/engine-chronocat-event/package.json
@@ -14,7 +14,7 @@
     "lib"
   ],
   "scripts": {
-    "build": "concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
+    "build": "node -r esbuild-register ../../scripts/runOnChanged.cts ./src concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
     "build:cjs": "node -r esbuild-register ../../scripts/build.cts",
     "build:dts": "tsc -p tsconfig.json"
   },
diff --git a/packages/red/package.json b/packages/red/package.json
index 7da1c07..79b8569 100644
--- a/packages/red/package.json
+++ b/packages/red/package.json
@@ -23,7 +23,7 @@
     "lib"
   ],
   "scripts": {
-    "build": "tsc -p tsconfig.json"
+    "build": "node -r esbuild-register ../../scripts/runOnChanged.cts ./src tsc -p tsconfig.json"
   },
   "devDependencies": {
     "concurrently": "^8.2.1",
diff --git a/packages/shell/package.json b/packages/shell/package.json
index 2ab25cf..d34fbf8 100644
--- a/packages/shell/package.json
+++ b/packages/shell/package.json
@@ -15,7 +15,7 @@
   ],
   "scripts": {
     "codegen": "node -r esbuild-register scripts/codegen.cts",
-    "build": "concurrently -n codegen yarn:codegen && concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
+    "build": "node -r esbuild-register ../../scripts/runOnChanged.cts ./src concurrently -n codegen yarn:codegen && concurrently -n cjs,dts yarn:build:cjs yarn:build:dts",
     "build:cjs": "node -r esbuild-register ../../scripts/build.cts",
     "build:dts": "tsc -p tsconfig.json"
   },
diff --git a/scripts/runOnChanged.cts b/scripts/runOnChanged.cts
new file mode 100644
index 0000000..ba5e81f
--- /dev/null
+++ b/scripts/runOnChanged.cts
@@ -0,0 +1,58 @@
+import * as fs from 'node:fs'
+import * as crypto from 'node:crypto'
+
+
+const watchFolder = process.argv[2]
+if (!watchFolder) {
+  console.error('Usage: node -r esbuild-register runOnChanged <folder> <command>')
+  process.exit(1)
+}
+const command = process.argv.slice(3).join(' ')
+
+// create or compare hash of files in the folder
+let hasChanged = false
+
+let hashes = new Map()
+
+const sha1 = (data: string) => crypto.createHash('sha1').update(data).digest('hex')
+
+
+const hashFile = (file: string) => {
+  const hash = sha1(fs.readFileSync(file, 'utf8'))
+  if (hashes.get(file) !== hash) {
+    hashes.set(file, hash)
+    hasChanged = true
+  }
+}
+
+const hashFilepath = `${watchFolder}/.runOnChanged.hashes.json`
+const hashFolder = (folder: string) => {
+  const files = fs.readdirSync(folder)
+  files.forEach((file: any) => {
+    const path = `${folder}/${file}`
+
+    if (file.endsWith('.runOnChanged.hashes.json')) return
+
+    if (fs.statSync(path).isDirectory()) {
+      hashFolder(path)
+    } else {
+      hashFile(path)
+    }
+  })
+}
+
+if (fs.existsSync(hashFilepath)) {
+  const oldHashes = JSON.parse(fs.readFileSync(hashFilepath, 'utf8'))
+  hashes = new Map(Object.entries(oldHashes))
+}
+
+hashFolder(watchFolder)
+
+if (hasChanged) {
+  console.log('[+] Files have changed, rebuilding...')
+  fs.writeFileSync(hashFilepath, JSON.stringify(Object.fromEntries(hashes)))
+  require('child_process').execSync(command, { stdio: 'inherit' })
+} else {
+  console.log('[-] Files not changed :)')
+}
+