diff --git a/common/config/rush/pnpm-lock.yaml b/common/config/rush/pnpm-lock.yaml
index 77c0608095..c5c8718b49 100644
--- a/common/config/rush/pnpm-lock.yaml
+++ b/common/config/rush/pnpm-lock.yaml
@@ -23,7 +23,7 @@ importers:
       '@azure/core-paging': ^1.5.0
       '@azure/core-rest-pipeline': ^1.12.0
       '@azure/core-tracing': ^1.0.0
-      '@azure/core-util': ^1.0.0-beta.1
+      '@azure/core-util': ^1.4.0
       '@azure/core-xml': ^1.0.0-beta.1
       '@azure/logger': ^1.0.0
       '@microsoft.azure/autorest.testserver': ^3.3.34
@@ -110,7 +110,7 @@ importers:
       '@types/fs-extra': 9.0.13
       '@types/js-yaml': 3.12.1
       '@types/mocha': 5.2.7
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       '@types/prettier': 1.19.1
       '@types/sinon': 10.0.16
       '@types/xmlbuilder': 0.0.34
@@ -167,12 +167,12 @@ importers:
     devDependencies:
       '@types/fs-extra': 8.1.2
       '@types/lodash': 4.14.196
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       eslint: 8.46.0
       fs-extra: 10.1.0
       prettier: 2.7.1
       rimraf: 3.0.2
-      ts-node: 10.9.1_wi7sq6ly3n6iu4nn6oglpcixxq
+      ts-node: 10.9.1_nxr4dymg3vz2ku26eufzpgsdza
       typescript: 5.0.4
 
   ../../packages/typespec-test:
@@ -208,7 +208,7 @@ importers:
       prettier: 2.7.1
     devDependencies:
       '@types/mocha': 5.2.7
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       ts-node: 8.10.2_typescript@5.0.4
       typescript: 5.0.4
 
@@ -225,6 +225,7 @@ importers:
       '@azure/core-lro': ^2.5.4
       '@azure/core-paging': ^1.5.0
       '@azure/core-rest-pipeline': ^1.12.0
+      '@azure/core-util': ^1.4.0
       '@azure/logger': ^1.0.4
       '@types/chai': ^4.3.1
       '@types/fs-extra': ^9.0.13
@@ -271,11 +272,12 @@ importers:
       '@azure/core-lro': 2.5.4
       '@azure/core-paging': 1.5.0
       '@azure/core-rest-pipeline': 1.12.0
+      '@azure/core-util': 1.4.0
       '@azure/logger': 1.0.4
       '@types/chai': 4.3.5
       '@types/fs-extra': 9.0.13
       '@types/mocha': 9.1.1
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       '@types/prettier': 2.7.3
       '@typescript-eslint/eslint-plugin': 5.62.0_btmaeoyl2rpnnxkii57gvvnqrq
       '@typescript-eslint/parser': 5.62.0_qjkw45b3tljvcusgfgkwdbduhu
@@ -286,7 +288,7 @@ importers:
       mkdirp: 2.1.6
       mocha: 9.2.2
       rimraf: 3.0.2
-      ts-node: 10.9.1_wi7sq6ly3n6iu4nn6oglpcixxq
+      ts-node: 10.9.1_nxr4dymg3vz2ku26eufzpgsdza
       typescript: 5.0.4
 
 packages:
@@ -361,7 +363,7 @@ packages:
     dependencies:
       '@azure/identity': 3.2.4
       '@azure/storage-blob': 12.15.0
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     transitivePeerDependencies:
       - encoding
       - supports-color
@@ -686,9 +688,9 @@ packages:
       '@azure/core-tracing': 1.0.1
       '@azure/core-util': 1.4.0
       '@azure/logger': 1.0.4
-      '@azure/msal-browser': 2.38.0
-      '@azure/msal-common': 13.2.0
-      '@azure/msal-node': 1.18.0
+      '@azure/msal-browser': 2.38.1
+      '@azure/msal-common': 13.2.1
+      '@azure/msal-node': 1.18.1
       events: 3.3.0
       jws: 4.0.0
       open: 8.4.2
@@ -705,23 +707,23 @@ packages:
     dependencies:
       tslib: 2.6.1
 
-  /@azure/msal-browser/2.38.0:
-    resolution: {integrity: sha512-gxBh83IumHgEP9uMCm9pJLKLRwICMQTxG9TX3AytdNt3oLUI3tytm/szYD5u5zKJgSkhHvwFSM+NPnM04hYw3w==}
+  /@azure/msal-browser/2.38.1:
+    resolution: {integrity: sha512-NROo7mLpw7aWtj8tWy9ZPz3WWiudwVAOIDZ1K3PPrjDAA4kFYayWlbZiJl1T1sD5Oqwa6FOtwzFSvuUj1CWp6Q==}
     engines: {node: '>=0.8.0'}
     dependencies:
-      '@azure/msal-common': 13.2.0
+      '@azure/msal-common': 13.2.1
     dev: true
 
-  /@azure/msal-common/13.2.0:
-    resolution: {integrity: sha512-rnstQ7Zgn3fSTKNQO+/YNV34/QXJs0vni7IA0/3QB1EEyrJg14xyRmTqlw9ta+pdSuT5OJwUP8kI3D/rBwUIBw==}
+  /@azure/msal-common/13.2.1:
+    resolution: {integrity: sha512-9CtyVdDtAOw+raemKg8gdBuE7gleObgSb7p4bzMIlUt8eM69/Gaow7uqr1gK3jLYINSrss32OZW8mBbdgVLiHg==}
     engines: {node: '>=0.8.0'}
     dev: true
 
-  /@azure/msal-node/1.18.0:
-    resolution: {integrity: sha512-N6GX1Twxw524e7gaJvj7hKtrPRmZl9qGY7U4pmUdx4XzoWYRFfYk4H1ZjVhQ7pwb5Ks88NNhbXVCagsuYPTEFg==}
+  /@azure/msal-node/1.18.1:
+    resolution: {integrity: sha512-B4kUOWJoN4vD8b3pGJ9Q9mIZhaDb8EnQM1aN0x1otlQgTfzDvEk6rWc6fy8uGdtXqcNddBtiXdc4oRiItroVkA==}
     engines: {node: 10 || 12 || 14 || 16 || 18}
     dependencies:
-      '@azure/msal-common': 13.2.0
+      '@azure/msal-common': 13.2.1
       jsonwebtoken: 9.0.1
       uuid: 8.3.2
     dev: true
@@ -742,18 +744,19 @@ packages:
       - encoding
     dev: true
 
-  /@babel/code-frame/7.22.5:
-    resolution: {integrity: sha512-Xmwn266vad+6DAqEB2A6V/CcZVp62BbwVmcOJc2RPuwih1kw02TjQvWVWlcKGbBPd+8/0V5DEkOcizRGYsspYQ==}
+  /@babel/code-frame/7.22.10:
+    resolution: {integrity: sha512-/KKIMG4UEL35WmI9OlvMhurwtytjvXoFcGNrOvyG9zIzA8YmPjVtIZUf7b05+TPO7G7/GEmLHDaoCgACHl9hhA==}
     engines: {node: '>=6.9.0'}
     dependencies:
-      '@babel/highlight': 7.22.5
+      '@babel/highlight': 7.22.10
+      chalk: 2.4.2
 
   /@babel/helper-validator-identifier/7.22.5:
     resolution: {integrity: sha512-aJXu+6lErq8ltp+JhkJUfk1MTGyuA4v7f3pA+BJ5HLfNC6nAQ0Cpi9uOquUj8Hehg0aUiHzWQbOVJGao6ztBAQ==}
     engines: {node: '>=6.9.0'}
 
-  /@babel/highlight/7.22.5:
-    resolution: {integrity: sha512-BSKlD1hgnedS5XRnGOljZawtag7H1yPfQp0tdNJCHoH6AZ+Pcm9VvkrK59/Yy593Ypg0zMxH2BxD1VPYUQ7UIw==}
+  /@babel/highlight/7.22.10:
+    resolution: {integrity: sha512-78aUtVcT7MUscr0K5mIEnkwxPE0MaxkR5RxRwuHaQ+JuU5AmTPhY+do2mdzVTnIJJpyBglql2pehuBIWHug+WQ==}
     engines: {node: '>=6.9.0'}
     dependencies:
       '@babel/helper-validator-identifier': 7.22.5
@@ -848,12 +851,7 @@ packages:
     dependencies:
       '@jridgewell/set-array': 1.1.2
       '@jridgewell/sourcemap-codec': 1.4.15
-      '@jridgewell/trace-mapping': 0.3.18
-    dev: true
-
-  /@jridgewell/resolve-uri/3.1.0:
-    resolution: {integrity: sha512-F2msla3tad+Mfht5cJq7LSXcdudKTWCVYUgw6pLFOOHSTtZlj6SWNYAp+AhuqLmWdBO2X5hPrLcu8cVP8fy28w==}
-    engines: {node: '>=6.0.0'}
+      '@jridgewell/trace-mapping': 0.3.19
     dev: true
 
   /@jridgewell/resolve-uri/3.1.1:
@@ -870,22 +868,18 @@ packages:
     resolution: {integrity: sha512-UTYAUj/wviwdsMfzoSJspJxbkH5o1snzwX0//0ENX1u/55kkZZkcTZP6u9bwKGkv+dkk9at4m1Cpt0uY80kcpQ==}
     dependencies:
       '@jridgewell/gen-mapping': 0.3.3
-      '@jridgewell/trace-mapping': 0.3.18
-    dev: true
-
-  /@jridgewell/sourcemap-codec/1.4.14:
-    resolution: {integrity: sha512-XPSJHWmi394fuUuzDnGz1wiKqWfo1yXecHQMRf2l6hztTO+nPru658AyDngaBe7isIxEkRsPR3FZh+s7iVa4Uw==}
+      '@jridgewell/trace-mapping': 0.3.19
     dev: true
 
   /@jridgewell/sourcemap-codec/1.4.15:
     resolution: {integrity: sha512-eF2rxCRulEKXHTRiDrDy6erMYWqNw4LPdQ8UQA4huuxaQsVeRPFl2oM8oDGxMFhJUWZf9McpLtJasDDZb/Bpeg==}
     dev: true
 
-  /@jridgewell/trace-mapping/0.3.18:
-    resolution: {integrity: sha512-w+niJYzMHdd7USdiH2U6869nqhD2nbfZXND5Yp93qIbEmnDNk7PD48o+YchRVpzMU7M6jVCbenTR7PA1FLQ9pA==}
+  /@jridgewell/trace-mapping/0.3.19:
+    resolution: {integrity: sha512-kf37QtfW+Hwx/buWGMPcR60iF9ziHa6r/CZJIHbmcm4+0qrXiVdxegAH0F6yddEVQ7zdkjcGCgCzUu+BcbhQxw==}
     dependencies:
-      '@jridgewell/resolve-uri': 3.1.0
-      '@jridgewell/sourcemap-codec': 1.4.14
+      '@jridgewell/resolve-uri': 3.1.1
+      '@jridgewell/sourcemap-codec': 1.4.15
     dev: true
 
   /@jridgewell/trace-mapping/0.3.9:
@@ -1057,18 +1051,18 @@ packages:
   /@types/cors/2.8.13:
     resolution: {integrity: sha512-RG8AStHlUiV5ysZQKq97copd2UmVYw3/pRMLefISZ3S1hK104Cwm7iLQ3fTKx+lsUH2CE8FlLaYeEA2LSeqYUA==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: true
 
   /@types/eslint-scope/3.7.4:
     resolution: {integrity: sha512-9K4zoImiZc3HlIp6AVUDE4CWYx22a+lhSZMYNpbjW04+YF0KWj4pJXnEMjdnFTiQibFFmElcsasJXDbdI/EPhA==}
     dependencies:
-      '@types/eslint': 8.44.1
+      '@types/eslint': 8.44.2
       '@types/estree': 1.0.1
     dev: true
 
-  /@types/eslint/8.44.1:
-    resolution: {integrity: sha512-XpNDc4Z5Tb4x+SW1MriMVeIsMoONHCkWFMkR/aPJbzEsxqHy+4Glu/BqTdPrApfDeMaXbtNh6bseNgl5KaWrSg==}
+  /@types/eslint/8.44.2:
+    resolution: {integrity: sha512-sdPRb9K6iL5XZOmBubg8yiFp5yS/JdUDQsq5e6h95km91MCYMuvp7mh1fjPEYUhvHepKpZOjnEaMBR4PxjWDzg==}
     dependencies:
       '@types/estree': 1.0.1
       '@types/json-schema': 7.0.12
@@ -1081,13 +1075,13 @@ packages:
   /@types/fs-extra/8.1.2:
     resolution: {integrity: sha512-SvSrYXfWSc7R4eqnOzbQF4TZmfpNSM9FrSWLU3EUnWBuyZqNBOrv1B1JA3byUDPUl9z4Ab3jeZG2eDdySlgNMg==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: true
 
   /@types/fs-extra/9.0.13:
     resolution: {integrity: sha512-nEnwB++1u5lVDM2UI4c1+5R+FYaKfaAzS4OococimjVm3nQw3TuzH5UNsocrcTBbhnerblyHj4A49qXbIiZdpA==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: true
 
   /@types/js-yaml/3.12.1:
@@ -1116,11 +1110,11 @@ packages:
   /@types/node-fetch/2.6.4:
     resolution: {integrity: sha512-1ZX9fcN4Rvkvgv4E6PAY5WXUFWFcRWxZa3EW83UjycOB9ljJCedb2CupIP4RZMEwF/M3eTcCihbBRgwtGbg5Rg==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       form-data: 3.0.1
 
-  /@types/node/18.17.2:
-    resolution: {integrity: sha512-wBo3KqP/PBqje5TI9UTiuL3yWfP6sdPtjtygSOqcYZWT232dfDeDOnkDps5wqZBP9NgGgYrNejinl0faAuE+HQ==}
+  /@types/node/18.17.3:
+    resolution: {integrity: sha512-2x8HWtFk0S99zqVQABU9wTpr8wPoaDHZUcAkoTKH+nL7kPv3WUI9cRi/Kk5Mz4xdqXSqTkKP7IWNoQQYCnDsTA==}
 
   /@types/prettier/1.19.1:
     resolution: {integrity: sha512-5qOlnZscTn4xxM5MeGXAMOsIOIKIbh9e85zJWfBRVPlRMEVawzoPhINYbRGkBZCI8LxvBe7tJCdWiarA99OZfQ==}
@@ -1151,13 +1145,13 @@ packages:
   /@types/tunnel/0.0.1:
     resolution: {integrity: sha512-AOqu6bQu5MSWwYvehMXLukFHnupHrpZ8nvgae5Ggie9UwzDR1CCwoXgSSWNZJuyOlCdfdsWMA5F2LlmvyoTv8A==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: false
 
   /@types/tunnel/0.0.3:
     resolution: {integrity: sha512-sOUTGn6h1SfQ+gbgqC364jLFBw2lnFqkgF3q0WovEHRLMrVD1sd5aufqi/aJObLekJO+Aq5z646U4Oxy6shXMA==}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: true
 
   /@types/xmlbuilder/0.0.34:
@@ -1178,7 +1172,7 @@ packages:
     resolution: {integrity: sha512-Cn6WYCm0tXv8p6k+A8PvbDG763EDpBoTzHdA+Q/MF6H3sapGjCm9NzoaJncJS9tUKSuCoDs9XHxYYsQDgxR6kw==}
     requiresBuild: true
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
     dev: true
     optional: true
 
@@ -1317,7 +1311,7 @@ packages:
     engines: {node: '>=16.0.0'}
     hasBin: true
     dependencies:
-      '@babel/code-frame': 7.22.5
+      '@babel/code-frame': 7.22.10
       ajv: 8.12.0
       change-case: 4.1.2
       globby: 13.1.4
@@ -1847,7 +1841,7 @@ packages:
     hasBin: true
     dependencies:
       caniuse-lite: 1.0.30001519
-      electron-to-chromium: 1.4.484
+      electron-to-chromium: 1.4.487
       node-releases: 2.0.13
       update-browserslist-db: 1.0.11_browserslist@4.21.10
     dev: true
@@ -2387,8 +2381,8 @@ packages:
     resolution: {integrity: sha512-WMwm9LhRUo+WUaRN+vRuETqG89IgZphVSNkdFgeb6sS/E4OrDIN7t48CAewSHXc6C8lefD8KKfr5vY61brQlow==}
     dev: true
 
-  /electron-to-chromium/1.4.484:
-    resolution: {integrity: sha512-nO3ZEomTK2PO/3TUXgEx0A97xZTpKVf4p427lABHuCpT1IQ2N+njVh29DkQkCk6Q4m2wjU+faK4xAcfFndwjvw==}
+  /electron-to-chromium/1.4.487:
+    resolution: {integrity: sha512-XbCRs/34l31np/p33m+5tdBrdXu9jJkZxSbNxj5I0H1KtV2ZMSB+i/HYqDiRzHaFx2T5EdytjoBRe8QRJE2vQg==}
     dev: true
 
   /emoji-regex/8.0.0:
@@ -2425,7 +2419,7 @@ packages:
     dependencies:
       '@types/cookie': 0.4.1
       '@types/cors': 2.8.13
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       accepts: 1.3.8
       base64id: 2.0.0
       cookie: 0.4.2
@@ -3446,8 +3440,8 @@ packages:
     engines: {node: '>= 0.4'}
     dev: true
 
-  /is-core-module/2.12.1:
-    resolution: {integrity: sha512-Q4ZuBAe2FUsKtyQJoQHlvP8OvBERxO3jEmy1I7hcRXcJBGGHFh/aJBswbXuS9sgrDH2QUO8ilkwNPHvHMd8clg==}
+  /is-core-module/2.13.0:
+    resolution: {integrity: sha512-Z7dk6Qo8pOCp3l4tsX2C5ZVas4V+UxwQodwZhLopL91TX8UyyHEXafPcyoeeWuLrwzHcr3igO78wNLwHJHsMCQ==}
     dependencies:
       has: 1.0.3
     dev: true
@@ -3636,7 +3630,7 @@ packages:
     resolution: {integrity: sha512-7vuh85V5cdDofPyxn58nrPjBktZo0u9x1g8WtjQol+jZDaE+fhN+cIvTj11GndBnMnyfrUOG1sZQxCdjKh+DKg==}
     engines: {node: '>= 10.13.0'}
     dependencies:
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       merge-stream: 2.0.0
       supports-color: 8.1.1
     dev: true
@@ -4208,7 +4202,7 @@ packages:
     resolution: {integrity: sha512-/5CMN3T0R4XTj4DcGaexo+roZSdSFW/0AOOTROrjxzCG1wrWXEsGbRKevjlIL+ZDE4sZlJr5ED4YW0yqmkK+eA==}
     dependencies:
       hosted-git-info: 2.8.9
-      resolve: 1.22.2
+      resolve: 1.22.4
       semver: 5.7.2
       validate-npm-package-license: 3.0.4
     dev: true
@@ -4667,7 +4661,7 @@ packages:
     resolution: {integrity: sha512-/njmZ8s1wVeR6pjTZ+0nCnv8SpZNRMT2D1RLOJQESlYFDBvwpTA4KWJpZ+sBJ4+vhjILRcK7JIFdGCdxEAAitg==}
     engines: {node: '>= 0.10'}
     dependencies:
-      resolve: 1.22.2
+      resolve: 1.22.4
     dev: true
 
   /regexp.prototype.flags/1.5.0:
@@ -4757,11 +4751,11 @@ packages:
     engines: {node: '>=8'}
     dev: true
 
-  /resolve/1.22.2:
-    resolution: {integrity: sha512-Sb+mjNHOULsBv818T40qSPeRiuWLyaGMa5ewydRLFimneixmVy2zdivRl+AF6jaYPC8ERxGDmFSiqui6SfPd+g==}
+  /resolve/1.22.4:
+    resolution: {integrity: sha512-PXNdCiPqDqeUou+w1C2eTQbNfxKSuMxqTCuvlmmMsk1NWHL5fRrhY6Pl0qEYYc6+QqGClco1Qj8XnjPego4wfg==}
     hasBin: true
     dependencies:
-      is-core-module: 2.12.1
+      is-core-module: 2.13.0
       path-parse: 1.0.7
       supports-preserve-symlinks-flag: 1.0.0
     dev: true
@@ -5269,7 +5263,7 @@ packages:
       uglify-js:
         optional: true
     dependencies:
-      '@jridgewell/trace-mapping': 0.3.18
+      '@jridgewell/trace-mapping': 0.3.19
       jest-worker: 27.5.1
       schema-utils: 3.3.0
       serialize-javascript: 6.0.1
@@ -5351,7 +5345,7 @@ packages:
       code-block-writer: 11.0.3
     dev: false
 
-  /ts-node/10.9.1_wi7sq6ly3n6iu4nn6oglpcixxq:
+  /ts-node/10.9.1_nxr4dymg3vz2ku26eufzpgsdza:
     resolution: {integrity: sha512-NtVysVPkxxrwFGUUxGYhfux8k78pQB3JqYBXlLRZgdGUqTO5wU/UyHop5p70iEbGhB7q5KmiZiU0Y3KlJrScEw==}
     hasBin: true
     peerDependencies:
@@ -5370,7 +5364,7 @@ packages:
       '@tsconfig/node12': 1.0.11
       '@tsconfig/node14': 1.0.3
       '@tsconfig/node16': 1.0.4
-      '@types/node': 18.17.2
+      '@types/node': 18.17.3
       acorn: 8.10.0
       acorn-walk: 8.2.0
       arg: 4.1.3
diff --git a/packages/autorest.typescript/package.json b/packages/autorest.typescript/package.json
index 1577957aa0..9252e0f757 100644
--- a/packages/autorest.typescript/package.json
+++ b/packages/autorest.typescript/package.json
@@ -79,7 +79,7 @@
   "devDependencies": {
     "@azure-tools/test-recorder": "^3.0.0",
     "@azure/abort-controller": "^1.0.1",
-    "@azure/core-util": "^1.0.0-beta.1",
+    "@azure/core-util": "^1.4.0",
     "@azure/core-xml": "^1.0.0-beta.1",
     "@microsoft.azure/autorest.testserver": "^3.3.34",
     "@types/chai": "^4.2.8",
diff --git a/packages/rlc-common/src/metadata/buildPackageFile.ts b/packages/rlc-common/src/metadata/buildPackageFile.ts
index 9919fbd84d..d35fc02308 100644
--- a/packages/rlc-common/src/metadata/buildPackageFile.ts
+++ b/packages/rlc-common/src/metadata/buildPackageFile.ts
@@ -164,6 +164,9 @@ function restLevelPackage(model: RLCModel, hasSamplesGenerated: boolean) {
       ...(hasLRO && {
         "@azure/core-lro": "^2.5.4",
         "@azure/abort-controller": "^1.0.0"
+      }),
+      ...(model.options.isModularLibrary && {
+        "@azure/core-util": "^1.4.0"
       })
     },
     devDependencies: {
diff --git a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package-files/package.json b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package-files/package.json
index 6948c195da..9ea8d0e70e 100644
--- a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package-files/package.json
+++ b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package-files/package.json
@@ -126,7 +126,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package.json b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package.json
index cd50faae68..7961474f22 100644
--- a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package.json
+++ b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/src/api/operations.ts b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/src/api/operations.ts
index a893700226..4cbeee4732 100644
--- a/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/src/api/operations.ts
+++ b/packages/typespec-test/test/eventgrid_modular/generated/typespec-ts/src/api/operations.ts
@@ -28,6 +28,7 @@ import {
   StreamableMethod,
   operationOptionsToRequestParameters,
 } from "@azure-rest/core-client";
+import { uint8ArrayToString, stringToUint8Array } from "@azure/core-util";
 import {
   PublishCloudEventOptions,
   PublishCloudEventsOptions,
@@ -52,7 +53,24 @@ export function _publishCloudEventSend(
       contentType:
         (options.contentType as any) ??
         "application/cloudevents+json; charset=utf-8",
-      body: { event: event },
+      body: {
+        event: {
+          id: event["id"],
+          source: event["source"],
+          data: event["data"],
+          data_base64:
+            event["dataBase64"] !== undefined
+              ? uint8ArrayToString(event["dataBase64"], "base64")
+              : undefined,
+          type: event["type"],
+          time:
+            event["time"] !== undefined ? new Date(event["time"]) : undefined,
+          specversion: event["specversion"],
+          dataschema: event["dataschema"],
+          datacontenttype: event["datacontenttype"],
+          subject: event["subject"],
+        },
+      },
     });
 }
 
@@ -90,15 +108,29 @@ export function _publishCloudEventsSend(
 ): StreamableMethod<
   PublishCloudEvents200Response | PublishCloudEventsDefaultResponse
 > {
-  return context
-    .path("/topics/{topicName}:publish", topicName)
-    .post({
-      ...operationOptionsToRequestParameters(options),
-      contentType:
-        (options.contentType as any) ??
-        "application/cloudevents-batch+json; charset=utf-8",
-      body: events,
-    });
+  return context.path("/topics/{topicName}:publish", topicName).post({
+    ...operationOptionsToRequestParameters(options),
+    contentType:
+      (options.contentType as any) ??
+      "application/cloudevents-batch+json; charset=utf-8",
+    body: (events ?? []).map((p) => {
+      return {
+        id: p["id"],
+        source: p["source"],
+        data: p["data"],
+        data_base64:
+          p["dataBase64"] !== undefined
+            ? uint8ArrayToString(p["dataBase64"], "base64")
+            : undefined,
+        type: p["type"],
+        time: p["time"] !== undefined ? new Date(p["time"]) : undefined,
+        specversion: p["specversion"],
+        dataschema: p["dataschema"],
+        datacontenttype: p["datacontenttype"],
+        subject: p["subject"],
+      };
+    }),
+  });
 }
 
 export async function _publishCloudEventsDeserialize(
@@ -167,9 +199,13 @@ export async function _receiveCloudEventsDeserialize(
         id: p.event["id"],
         source: p.event["source"],
         data: p.event["data"],
-        dataBase64: Buffer.from(p.event["data_base64"] ?? ""),
+        dataBase64:
+          typeof p.event["data_base64"] === "string"
+            ? stringToUint8Array(p.event["data_base64"], "base64")
+            : p.event["data_base64"],
         type: p.event["type"],
-        time: new Date(p.event["time"] ?? ""),
+        time:
+          p.event["time"] !== undefined ? new Date(p.event["time"]) : undefined,
         specversion: p.event["specversion"],
         dataschema: p.event["dataschema"],
         datacontenttype: p.event["datacontenttype"],
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package-files/package.json b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package-files/package.json
index f91aa9ac82..b0f01b31ea 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package-files/package.json
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package-files/package.json
@@ -142,7 +142,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package.json b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package.json
index 96758f13bd..28c4226c04 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package.json
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/package.json
@@ -58,7 +58,8 @@
     "tslib": "^2.2.0",
     "@azure/core-paging": "^1.5.0",
     "@azure/core-lro": "^2.5.4",
-    "@azure/abort-controller": "^1.0.0"
+    "@azure/abort-controller": "^1.0.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestAdministration/api/operations.ts b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestAdministration/api/operations.ts
index 291c32e69f..521b928756 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestAdministration/api/operations.ts
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestAdministration/api/operations.ts
@@ -76,11 +76,42 @@ export function _createOrUpdateTestSend(
       contentType:
         (options.contentType as any) ?? "application/merge-patch+json",
       body: {
-        passFailCriteria: options?.passFailCriteria,
+        passFailCriteria: {
+          passFailMetrics: options?.passFailCriteria?.["passFailMetrics"],
+        },
         secrets: options?.secrets,
-        certificate: options?.certificate,
+        certificate: {
+          value: options?.certificate?.["value"],
+          type: options?.certificate?.["type"],
+          name: options?.certificate?.["name"],
+        },
         environmentVariables: options?.environmentVariables,
-        loadTestConfiguration: options?.loadTestConfiguration,
+        loadTestConfiguration: {
+          engineInstances: options?.loadTestConfiguration?.["engineInstances"],
+          splitAllCSVs: options?.loadTestConfiguration?.["splitAllCSVs"],
+          quickStartTest: options?.loadTestConfiguration?.["quickStartTest"],
+          optionalLoadTestConfig: !options?.loadTestConfiguration
+            ?.optionalLoadTestConfig
+            ? undefined
+            : {
+                endpointUrl:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "endpointUrl"
+                  ],
+                virtualUsers:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "virtualUsers"
+                  ],
+                rampUpTime:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "rampUpTime"
+                  ],
+                duration:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "duration"
+                  ],
+              },
+        },
         description: options?.description,
         displayName: options?.displayName,
         subnetId: options?.subnetId,
diff --git a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestRun/api/operations.ts b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestRun/api/operations.ts
index 610e744233..ca9151a566 100644
--- a/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestRun/api/operations.ts
+++ b/packages/typespec-test/test/loadtesting_modular/generated/typespec-ts/src/loadTestRun/api/operations.ts
@@ -88,11 +88,42 @@ export function _testRunSend(
         (options.contentType as any) ?? "application/merge-patch+json",
       queryParameters: { oldTestRunId: options?.oldTestRunId },
       body: {
-        passFailCriteria: options?.passFailCriteria,
+        passFailCriteria: {
+          passFailMetrics: options?.passFailCriteria?.["passFailMetrics"],
+        },
         secrets: options?.secrets,
-        certificate: options?.certificate,
+        certificate: {
+          value: options?.certificate?.["value"],
+          type: options?.certificate?.["type"],
+          name: options?.certificate?.["name"],
+        },
         environmentVariables: options?.environmentVariables,
-        loadTestConfiguration: options?.loadTestConfiguration,
+        loadTestConfiguration: {
+          engineInstances: options?.loadTestConfiguration?.["engineInstances"],
+          splitAllCSVs: options?.loadTestConfiguration?.["splitAllCSVs"],
+          quickStartTest: options?.loadTestConfiguration?.["quickStartTest"],
+          optionalLoadTestConfig: !options?.loadTestConfiguration
+            ?.optionalLoadTestConfig
+            ? undefined
+            : {
+                endpointUrl:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "endpointUrl"
+                  ],
+                virtualUsers:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "virtualUsers"
+                  ],
+                rampUpTime:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "rampUpTime"
+                  ],
+                duration:
+                  options?.loadTestConfiguration?.optionalLoadTestConfig?.[
+                    "duration"
+                  ],
+              },
+        },
         displayName: options?.displayName,
         testId: options?.testId,
         description: options?.description,
diff --git a/packages/typespec-test/test/openai_modular/generated/typespec-ts/package-files/package.json b/packages/typespec-test/test/openai_modular/generated/typespec-ts/package-files/package.json
index bb71052ada..d20d7f79da 100644
--- a/packages/typespec-test/test/openai_modular/generated/typespec-ts/package-files/package.json
+++ b/packages/typespec-test/test/openai_modular/generated/typespec-ts/package-files/package.json
@@ -126,7 +126,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-test/test/openai_modular/generated/typespec-ts/package.json b/packages/typespec-test/test/openai_modular/generated/typespec-ts/package.json
index f698700689..5c034694d2 100644
--- a/packages/typespec-test/test/openai_modular/generated/typespec-ts/package.json
+++ b/packages/typespec-test/test/openai_modular/generated/typespec-ts/package.json
@@ -57,7 +57,8 @@
     "@azure/logger": "^1.0.0",
     "tslib": "^2.2.0",
     "@azure/core-lro": "^2.5.4",
-    "@azure/abort-controller": "^1.0.0"
+    "@azure/abort-controller": "^1.0.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package-files/package.json b/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package-files/package.json
index 05f9946086..546a74ac38 100644
--- a/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package-files/package.json
+++ b/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package-files/package.json
@@ -126,7 +126,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package.json b/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package.json
index 8f05bcbab1..95d447453f 100644
--- a/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package.json
+++ b/packages/typespec-test/test/widget_dpg/generated/typespec-ts/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-ts/package.json b/packages/typespec-ts/package.json
index fb5720e360..9c2bca16d2 100644
--- a/packages/typespec-ts/package.json
+++ b/packages/typespec-ts/package.json
@@ -60,7 +60,8 @@
     "@azure/core-paging": "^1.5.0",
     "@azure/core-lro": "^2.5.4",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/logger": "^1.0.4"
+    "@azure/logger": "^1.0.4",
+    "@azure/core-util": "^1.4.0"
   },
   "peerDependencies": {
     "@azure-tools/typespec-azure-core": ">=0.32.0 <1.0.0",
diff --git a/packages/typespec-ts/src/modular/buildCodeModel.ts b/packages/typespec-ts/src/modular/buildCodeModel.ts
index d51673f9c1..c9e7ace45e 100644
--- a/packages/typespec-ts/src/modular/buildCodeModel.ts
+++ b/packages/typespec-ts/src/modular/buildCodeModel.ts
@@ -37,6 +37,7 @@ import {
   IntrinsicType,
   getProjectedName,
   isNullType,
+  getEncode,
   isTemplateDeclarationOrInstance
 } from "@typespec/compiler";
 import {
@@ -996,11 +997,12 @@ function emitCredentialUnion(cred_types: CredentialTypeUnion) {
 }
 
 function emitStdScalar(
+  program: Program,
   scalar: Scalar & { name: IntrinsicScalarName }
 ): Record<string, any> {
   switch (scalar.name) {
     case "bytes":
-      return { type: "byte-array", format: "byte" };
+      return { type: "byte-array", format: getEncode(program, scalar) };
     case "int8":
     case "int16":
     case "int32":
@@ -1095,7 +1097,7 @@ function applyIntrinsicDecorators(
 function emitScalar(program: Program, scalar: Scalar): Record<string, any> {
   let result: Record<string, any> = {};
   if (program.checker.isStdType(scalar)) {
-    result = emitStdScalar(scalar);
+    result = emitStdScalar(program, scalar);
   } else if (scalar.baseScalar) {
     result = emitScalar(program, scalar.baseScalar);
   }
diff --git a/packages/typespec-ts/src/modular/buildOperations.ts b/packages/typespec-ts/src/modular/buildOperations.ts
index 3e58c5ea48..e3628b360e 100644
--- a/packages/typespec-ts/src/modular/buildOperations.ts
+++ b/packages/typespec-ts/src/modular/buildOperations.ts
@@ -26,6 +26,7 @@ export function buildOperationFiles(
   needUnexpectedHelper: boolean = true
 ) {
   for (const operationGroup of client.operationGroups) {
+    const importSet: Map<string, Set<string>> = new Map<string, Set<string>>();
     const fileName = operationGroup.className
       ? `${normalizeName(operationGroup.className, NameType.File)}`
       : // When the program has no operation groups defined all operations are put
@@ -73,11 +74,16 @@ export function buildOperationFiles(
     }
     operationGroup.operations.forEach((o) => {
       const operationDeclaration = getOperationFunction(o, clientType);
-      const sendOperationDeclaration = getSendPrivateFunction(o, clientType);
+      const sendOperationDeclaration = getSendPrivateFunction(
+        o,
+        clientType,
+        importSet
+      );
       const deserializeOperationDeclaration = getDeserializePrivateFunction(
         o,
         isRLCMultiEndpoint(dpgContext),
-        needUnexpectedHelper
+        needUnexpectedHelper,
+        importSet
       );
       operationGroupFile.addFunctions([
         sendOperationDeclaration,
@@ -95,7 +101,16 @@ export function buildOperationFiles(
         ]
       }
     ]);
-
+    if (importSet.size > 0) {
+      for (const [moduleName, imports] of importSet.entries()) {
+        operationGroupFile.addImportDeclarations([
+          {
+            moduleSpecifier: moduleName,
+            namedImports: [...imports.values()]
+          }
+        ]);
+      }
+    }
     operationGroupFile.fixMissingImports();
     // have to fixUnusedIdentifiers after everything get generated.
     operationGroupFile.fixUnusedIdentifiers();
diff --git a/packages/typespec-ts/src/modular/buildProjectFiles.ts b/packages/typespec-ts/src/modular/buildProjectFiles.ts
index ebaab04197..43c863fa60 100644
--- a/packages/typespec-ts/src/modular/buildProjectFiles.ts
+++ b/packages/typespec-ts/src/modular/buildProjectFiles.ts
@@ -172,7 +172,7 @@ export function emitPackage(
       "@azure-rest/core-client": "^1.1.2",
       "@azure/core-auth": "^1.4.1",
       "@azure/core-rest-pipeline": "^1.12.0",
-      "@azure/core-util": "^1.1.0",
+      "@azure/core-util": "^1.4.0",
       "@azure/logger": "^1.0.3",
       tslib: "^2.4.0"
     }
diff --git a/packages/typespec-ts/src/modular/helpers/operationHelpers.ts b/packages/typespec-ts/src/modular/helpers/operationHelpers.ts
index 254d025c4a..321e7200d5 100644
--- a/packages/typespec-ts/src/modular/helpers/operationHelpers.ts
+++ b/packages/typespec-ts/src/modular/helpers/operationHelpers.ts
@@ -44,7 +44,8 @@ function getRLCResponseType(rlcResponse?: OperationResponse) {
 
 export function getSendPrivateFunction(
   operation: Operation,
-  clientType: string
+  clientType: string,
+  importSet: Map<string, Set<string>>
 ): OptionalKind<FunctionDeclarationStructure> {
   const parameters = getOperationSignatureParameters(operation, clientType);
   const { name } = getOperationName(operation);
@@ -65,7 +66,8 @@ export function getSendPrivateFunction(
     `return context.path("${operationPath}", ${getPathParameters(
       operation
     )}).${operationMethod}({...operationOptionsToRequestParameters(options), ${getRequestParameters(
-      operation
+      operation,
+      importSet
     )}});`
   );
 
@@ -78,7 +80,8 @@ export function getSendPrivateFunction(
 export function getDeserializePrivateFunction(
   operation: Operation,
   needSubClient: boolean,
-  needUnexpectedHelper: boolean
+  needUnexpectedHelper: boolean,
+  importSet: Map<string, Set<string>>
 ): OptionalKind<FunctionDeclarationStructure> {
   const { name } = getOperationName(operation);
 
@@ -126,12 +129,20 @@ export function getDeserializePrivateFunction(
     statements.push(`return result.body`);
   } else if (response?.type?.elementType) {
     statements.push(
-      `return ${deserializeResponseValue(response.type, "result.body")}`
+      `return ${deserializeResponseValue(
+        response.type,
+        "result.body",
+        importSet
+      )}`
     );
   } else if (response?.type?.properties) {
     statements.push(
       `return {`,
-      getResponseMapping(response.type.properties ?? []).join(","),
+      getResponseMapping(
+        response.type.properties ?? [],
+        "result.body",
+        importSet
+      ).join(","),
       `}`
     );
   } else if (returnType.type === "void") {
@@ -258,7 +269,10 @@ export function getOperationOptionsName(operation: Operation) {
  * RLC internally. This will translate High Level parameters into the RLC ones.
  * Figuring out what goes in headers, body, path and qsp.
  */
-function getRequestParameters(operation: Operation): string {
+function getRequestParameters(
+  operation: Operation,
+  importSet: Map<string, Set<string>>
+): string {
   if (!operation.parameters) {
     return "";
   }
@@ -280,7 +294,9 @@ function getRequestParameters(operation: Operation): string {
 
   for (const param of operationParameters) {
     if (param.location === "header" || param.location === "query") {
-      parametersImplementation[param.location].push(getParameterMap(param));
+      parametersImplementation[param.location].push(
+        getParameterMap(param, importSet)
+      );
     }
   }
 
@@ -302,30 +318,60 @@ function getRequestParameters(operation: Operation): string {
     )}},`;
   }
 
-  paramStr = `${paramStr}${buildBodyParameter(operation.bodyParameter)}`;
+  paramStr = `${paramStr}${buildBodyParameter(
+    operation.bodyParameter,
+    importSet
+  )}`;
 
   return paramStr;
 }
 
-function buildBodyParameter(bodyParameter: BodyParameter | undefined) {
+function buildBodyParameter(
+  bodyParameter: BodyParameter | undefined,
+  importSet: Map<string, Set<string>>
+) {
   if (!bodyParameter) {
     return "";
   }
 
   if (bodyParameter.type.type === "model") {
     const bodyParts: string[] = [];
+    let hasSerializeBody = false;
     for (const param of bodyParameter?.type.properties?.filter(
       (p) => !p.readonly
     ) ?? []) {
-      bodyParts.push(getParameterMap(param));
+      if (param.type.type === "model" && isRequired(param)) {
+        hasSerializeBody = true;
+        bodyParts.push(
+          ...getRequestModelMapping(param.type, param.clientName, importSet)
+        );
+      } else {
+        bodyParts.push(getParameterMap(param, importSet));
+      }
     }
 
     if (bodyParameter && bodyParameter.type.properties) {
-      return `\nbody: {${bodyParts.join(",\n")}},`;
+      if (hasSerializeBody) {
+        return `\nbody: {"${bodyParameter.restApiName}": {${bodyParts.join(
+          ",\n"
+        )}}},`;
+      } else {
+        return `\nbody: {${bodyParts.join(",\n")}},`;
+      }
     }
   }
 
   if (bodyParameter.type.type === "list") {
+    if (bodyParameter.type.elementType?.type === "model") {
+      const bodyParts = getRequestModelMapping(
+        bodyParameter.type.elementType,
+        "p",
+        importSet
+      );
+      return `\nbody: (${bodyParameter.clientName} ?? []).map((p) => { return {
+        ${bodyParts.join(", ")}
+      };}),`;
+    }
     return `\nbody: ${bodyParameter.clientName},`;
   }
 
@@ -339,21 +385,24 @@ function buildBodyParameter(bodyParameter: BodyParameter | undefined) {
 /**
  * This function helps with renames, translating client names to rest api names
  */
-function getParameterMap(param: Parameter | Property) {
+function getParameterMap(
+  param: Parameter | Property,
+  importSet: Map<string, Set<string>>
+): string {
   if (isConstant(param)) {
     return getConstantValue(param);
   }
 
   if (isOptionalWithouDefault(param)) {
-    return getOptionalWithoutDefault(param);
+    return getOptionalWithoutDefault(param, importSet);
   }
 
   if (isOptionalWithDefault(param)) {
-    return getOptionalWithDefault(param);
+    return getOptionalWithDefault(param, importSet);
   }
 
   if (isRequired(param)) {
-    return getRequired(param);
+    return getRequired(param, importSet);
   }
 
   throw new Error(`Parameter ${param.clientName} is not supported`);
@@ -391,7 +440,14 @@ function isRequired(param: Parameter | Property): param is RequiredType {
   return !param.optional;
 }
 
-function getRequired(param: RequiredType) {
+function getRequired(param: RequiredType, importSet: Map<string, Set<string>>) {
+  if (param.type.type === "model") {
+    return `"${param.restApiName}": ${getRequestModelMapping(
+      param.type,
+      param.clientName,
+      importSet
+    ).join(",")}`;
+  }
   return `"${param.restApiName}": ${param.clientName}`;
 }
 
@@ -426,7 +482,17 @@ function isOptionalWithouDefault(
 ): param is OptionalWithoutDefaultType {
   return Boolean(param.optional && !param.clientDefaultValue);
 }
-function getOptionalWithoutDefault(param: OptionalWithoutDefaultType) {
+function getOptionalWithoutDefault(
+  param: OptionalWithoutDefaultType,
+  importSet: Map<string, Set<string>>
+) {
+  if (param.type.type === "model") {
+    return `"${param.restApiName}": {${getRequestModelMapping(
+      param.type,
+      "options?." + param.clientName + "?",
+      importSet
+    ).join(", ")}}`;
+  }
   return `"${param.restApiName}": options?.${param.clientName}`;
 }
 
@@ -439,7 +505,17 @@ function isOptionalWithDefault(
   return Boolean(param.clientDefaultValue);
 }
 
-function getOptionalWithDefault(param: OptionalWithDefaultType) {
+function getOptionalWithDefault(
+  param: OptionalWithDefaultType,
+  importSet: Map<string, Set<string>>
+) {
+  if (param.type.type === "model") {
+    return `"${param.restApiName}": {${getRequestModelMapping(
+      param.type,
+      "options?." + param.clientName,
+      importSet
+    ).join(", ")}} ?? ${getQuotedValue(param)}`;
+  }
   return `"${param.restApiName}": options.${
     param.clientName
   } ?? ${getQuotedValue(param)}`;
@@ -503,13 +579,78 @@ function getNullableCheck(name: string, type: Type) {
 
   return `${name} === null ? null :`;
 }
+
+/**
+ *
+ * This function helps translating an HLC request to RLC request,
+ * extracting properties from body and headers and building the RLC response object
+ */
+function getRequestModelMapping(
+  modelPropertyType: Type,
+  propertyPath: string = "body",
+  importSet: Map<string, Set<string>>
+) {
+  if (!modelPropertyType.properties || !modelPropertyType.properties) {
+    return [];
+  }
+  const props: string[] = [];
+  const properties: Property[] = modelPropertyType.properties;
+  for (const property of properties) {
+    if (property.readonly) {
+      continue;
+    }
+    const propertyFullName = `${propertyPath}.${property.restApiName}`;
+    if (property.type.type === "model") {
+      let definition;
+      if (property.type.isCoreErrorType) {
+        definition = `"${property.restApiName}": ${getNullableCheck(
+          propertyFullName,
+          property.type
+        )} ${
+          !property.optional ? "" : `!${propertyFullName} ? undefined :`
+        } ${propertyFullName}`;
+      } else {
+        definition = `"${property.restApiName}": ${getNullableCheck(
+          propertyFullName,
+          property.type
+        )} ${
+          !property.optional ? "" : `!${propertyFullName} ? undefined :`
+        } {${getRequestModelMapping(
+          property.type,
+          `${propertyPath}.${property.restApiName}${
+            property.optional ? "?" : ""
+          }`,
+          importSet
+        )}}`;
+      }
+
+      props.push(definition);
+    } else {
+      const dot = propertyPath.endsWith("?") ? "." : "";
+      const restValue = `${
+        propertyPath ? `${propertyPath}${dot}` : `${dot}`
+      }["${property.clientName}"]`;
+      props.push(
+        `"${property.restApiName}": ${serializeRequestValue(
+          property.type,
+          restValue,
+          importSet
+        )}`
+      );
+    }
+  }
+
+  return props;
+}
+
 /**
  * This function helps translating an RLC response to an HLC response,
  * extracting properties from body and headers and building the HLC response object
  */
 function getResponseMapping(
   properties: Property[],
-  propertyPath: string = "result.body"
+  propertyPath: string = "result.body",
+  importSet: Map<string, Set<string>>
 ) {
   const props: string[] = [];
   for (const property of properties) {
@@ -534,7 +675,8 @@ function getResponseMapping(
           property.type.properties ?? [],
           `${propertyPath}.${property.restApiName}${
             property.optional ? "?" : ""
-          }`
+          }`,
+          importSet
         )}}`;
       }
 
@@ -547,7 +689,8 @@ function getResponseMapping(
       props.push(
         `"${property.clientName}": ${deserializeResponseValue(
           property.type,
-          restValue
+          restValue,
+          importSet
         )}`
       );
     }
@@ -561,29 +704,94 @@ function getResponseMapping(
  * We need to drill down into Array elements to make sure that the element type is
  * deserialized correctly
  */
-function deserializeResponseValue(type: Type, restValue: string): string {
+function deserializeResponseValue(
+  type: Type,
+  restValue: string,
+  importSet: Map<string, Set<string>>
+): string {
+  const coreUtilSet = importSet.get("@azure/core-util");
   switch (type.type) {
     case "datetime":
-      return `new Date(${restValue} ?? "")`;
-    case "byte-array":
-      return `Buffer.from(${restValue} ?? "")`;
+      return `${restValue} !== undefined? new Date(${restValue}): undefined`;
     case "list":
       if (type.elementType?.type === "model") {
         return `(${restValue} ?? []).map(p => ({${getResponseMapping(
           type.elementType?.properties ?? [],
-          "p"
+          "p",
+          importSet
         )}}))`;
       } else if (
         type.elementType?.properties?.some((p) => needsDeserialize(p.type))
       ) {
         return `(${restValue} ?? []).map(p => ${deserializeResponseValue(
           type.elementType!,
-          "p"
+          "p",
+          importSet
         )})`;
       } else {
         return restValue;
       }
+    case "byte-array":
+      if (!coreUtilSet) {
+        importSet.set(
+          "@azure/core-util",
+          new Set<string>().add("stringToUint8Array")
+        );
+      } else {
+        coreUtilSet.add("stringToUint8Array");
+      }
+      return `typeof ${restValue} === 'string'
+      ? stringToUint8Array(${restValue}, "${type.format ?? "base64"}")
+      : ${restValue}`;
+    default:
+      return restValue;
+  }
+}
 
+/**
+ * This function helps converting strings into JS complex types recursively.
+ * We need to drill down into Array elements to make sure that the element type is
+ * deserialized correctly
+ */
+function serializeRequestValue(
+  type: Type,
+  restValue: string,
+  importSet: Map<string, Set<string>> = new Map<string, Set<string>>()
+): string {
+  const coreUtilSet = importSet.get("@azure/core-util");
+  switch (type.type) {
+    case "datetime":
+      return `${restValue} !== undefined ? new Date(${restValue}): undefined`;
+    case "list":
+      if (type.elementType?.type === "model") {
+        return `(${restValue} ?? []).map(p => ({${getResponseMapping(
+          type.elementType?.properties ?? [],
+          "p",
+          importSet
+        )}}))`;
+      } else if (
+        type.elementType?.properties?.some((p) => needsDeserialize(p.type))
+      ) {
+        return `(${restValue} ?? []).map(p => ${deserializeResponseValue(
+          type.elementType!,
+          "p",
+          importSet
+        )})`;
+      } else {
+        return restValue;
+      }
+    case "byte-array":
+      if (!coreUtilSet) {
+        importSet.set(
+          "@azure/core-util",
+          new Set<string>().add("uint8ArrayToString")
+        );
+      } else {
+        coreUtilSet.add("uint8ArrayToString");
+      }
+      return `${restValue} !== undefined ? uint8ArrayToString(${restValue}, "${
+        type.format ?? "base64"
+      }"): undefined`;
     default:
       return restValue;
   }
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package-files/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package-files/package.json
index 16a9812258..ae8a4071dc 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package-files/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package-files/package.json
@@ -128,7 +128,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package.json
index 6ce299940c..95704ea4e9 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/default/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package-files/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package-files/package.json
index c3c21c4ac9..7718fc3c47 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package-files/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package-files/package.json
@@ -144,7 +144,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package.json
index 07374517c8..986779e349 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/multi-client/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package-files/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package-files/package.json
index 5bb07132d8..60df4f97b0 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package-files/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package-files/package.json
@@ -128,7 +128,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package.json
index b90e106d11..4501cda901 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/renamed-operation/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package-files/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package-files/package.json
index c254f2f4fd..0bd758d1c2 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package-files/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package-files/package.json
@@ -128,7 +128,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }
diff --git a/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package.json b/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package.json
index 8e75e10f77..af243afbff 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/client/structure/two-operation-group/package.json
@@ -55,7 +55,8 @@
     "@azure-rest/core-client": "^1.1.4",
     "@azure/core-rest-pipeline": "^1.12.0",
     "@azure/logger": "^1.0.0",
-    "tslib": "^2.2.0"
+    "tslib": "^2.2.0",
+    "@azure/core-util": "^1.4.0"
   },
   "devDependencies": {
     "@microsoft/api-extractor": "^7.31.1",
diff --git a/packages/typespec-ts/test/modularIntegration/generated/models/usage/generated/package-files/package.json b/packages/typespec-ts/test/modularIntegration/generated/models/usage/generated/package-files/package.json
index ef7f36b41e..06d40054b9 100644
--- a/packages/typespec-ts/test/modularIntegration/generated/models/usage/generated/package-files/package.json
+++ b/packages/typespec-ts/test/modularIntegration/generated/models/usage/generated/package-files/package.json
@@ -126,7 +126,7 @@
     "@azure-rest/core-client": "^1.1.2",
     "@azure/core-auth": "^1.4.1",
     "@azure/core-rest-pipeline": "^1.12.0",
-    "@azure/core-util": "^1.1.0",
+    "@azure/core-util": "^1.4.0",
     "@azure/logger": "^1.0.3",
     "tslib": "^2.4.0"
   }