diff --git a/baselines/dom.generated.d.ts b/baselines/dom.generated.d.ts
index 541bfa35b..3ceb40797 100644
--- a/baselines/dom.generated.d.ts
+++ b/baselines/dom.generated.d.ts
@@ -1677,6 +1677,7 @@ interface RequestInit {
     cache?: RequestCache;
     /** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
     credentials?: RequestCredentials;
+    duplex?: RequestDuplex;
     /** A Headers object, an object literal, or an array of two-item arrays to set request's headers. */
     headers?: HeadersInit;
     /** A cryptographic hash of the resource to be fetched by request. Sets request's integrity. */
@@ -28600,6 +28601,7 @@ type RemotePlaybackState = "connected" | "connecting" | "disconnected";
 type RequestCache = "default" | "force-cache" | "no-cache" | "no-store" | "only-if-cached" | "reload";
 type RequestCredentials = "include" | "omit" | "same-origin";
 type RequestDestination = "" | "audio" | "audioworklet" | "document" | "embed" | "font" | "frame" | "iframe" | "image" | "manifest" | "object" | "paintworklet" | "report" | "script" | "sharedworker" | "style" | "track" | "video" | "worker" | "xslt";
+type RequestDuplex = "half";
 type RequestMode = "cors" | "navigate" | "no-cors" | "same-origin";
 type RequestPriority = "auto" | "high" | "low";
 type RequestRedirect = "error" | "follow" | "manual";
diff --git a/baselines/serviceworker.generated.d.ts b/baselines/serviceworker.generated.d.ts
index 93e37afb1..96811a589 100644
--- a/baselines/serviceworker.generated.d.ts
+++ b/baselines/serviceworker.generated.d.ts
@@ -537,6 +537,7 @@ interface RequestInit {
     cache?: RequestCache;
     /** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
     credentials?: RequestCredentials;
+    duplex?: RequestDuplex;
     /** A Headers object, an object literal, or an array of two-item arrays to set request's headers. */
     headers?: HeadersInit;
     /** A cryptographic hash of the resource to be fetched by request. Sets request's integrity. */
@@ -8651,6 +8652,7 @@ type ReferrerPolicy = "" | "no-referrer" | "no-referrer-when-downgrade" | "origi
 type RequestCache = "default" | "force-cache" | "no-cache" | "no-store" | "only-if-cached" | "reload";
 type RequestCredentials = "include" | "omit" | "same-origin";
 type RequestDestination = "" | "audio" | "audioworklet" | "document" | "embed" | "font" | "frame" | "iframe" | "image" | "manifest" | "object" | "paintworklet" | "report" | "script" | "sharedworker" | "style" | "track" | "video" | "worker" | "xslt";
+type RequestDuplex = "half";
 type RequestMode = "cors" | "navigate" | "no-cors" | "same-origin";
 type RequestPriority = "auto" | "high" | "low";
 type RequestRedirect = "error" | "follow" | "manual";
diff --git a/baselines/sharedworker.generated.d.ts b/baselines/sharedworker.generated.d.ts
index b0ac0c20f..b6b362045 100644
--- a/baselines/sharedworker.generated.d.ts
+++ b/baselines/sharedworker.generated.d.ts
@@ -503,6 +503,7 @@ interface RequestInit {
     cache?: RequestCache;
     /** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
     credentials?: RequestCredentials;
+    duplex?: RequestDuplex;
     /** A Headers object, an object literal, or an array of two-item arrays to set request's headers. */
     headers?: HeadersInit;
     /** A cryptographic hash of the resource to be fetched by request. Sets request's integrity. */
@@ -8654,6 +8655,7 @@ type ReferrerPolicy = "" | "no-referrer" | "no-referrer-when-downgrade" | "origi
 type RequestCache = "default" | "force-cache" | "no-cache" | "no-store" | "only-if-cached" | "reload";
 type RequestCredentials = "include" | "omit" | "same-origin";
 type RequestDestination = "" | "audio" | "audioworklet" | "document" | "embed" | "font" | "frame" | "iframe" | "image" | "manifest" | "object" | "paintworklet" | "report" | "script" | "sharedworker" | "style" | "track" | "video" | "worker" | "xslt";
+type RequestDuplex = "half";
 type RequestMode = "cors" | "navigate" | "no-cors" | "same-origin";
 type RequestPriority = "auto" | "high" | "low";
 type RequestRedirect = "error" | "follow" | "manual";
diff --git a/baselines/webworker.generated.d.ts b/baselines/webworker.generated.d.ts
index da563d118..d93e53b57 100644
--- a/baselines/webworker.generated.d.ts
+++ b/baselines/webworker.generated.d.ts
@@ -581,6 +581,7 @@ interface RequestInit {
     cache?: RequestCache;
     /** A string indicating whether credentials will be sent with the request always, never, or only when sent to a same-origin URL. Sets request's credentials. */
     credentials?: RequestCredentials;
+    duplex?: RequestDuplex;
     /** A Headers object, an object literal, or an array of two-item arrays to set request's headers. */
     headers?: HeadersInit;
     /** A cryptographic hash of the resource to be fetched by request. Sets request's integrity. */
@@ -9391,6 +9392,7 @@ type ReferrerPolicy = "" | "no-referrer" | "no-referrer-when-downgrade" | "origi
 type RequestCache = "default" | "force-cache" | "no-cache" | "no-store" | "only-if-cached" | "reload";
 type RequestCredentials = "include" | "omit" | "same-origin";
 type RequestDestination = "" | "audio" | "audioworklet" | "document" | "embed" | "font" | "frame" | "iframe" | "image" | "manifest" | "object" | "paintworklet" | "report" | "script" | "sharedworker" | "style" | "track" | "video" | "worker" | "xslt";
+type RequestDuplex = "half";
 type RequestMode = "cors" | "navigate" | "no-cors" | "same-origin";
 type RequestPriority = "auto" | "high" | "low";
 type RequestRedirect = "error" | "follow" | "manual";
diff --git a/inputfiles/removedTypes.jsonc b/inputfiles/removedTypes.jsonc
index 2e03456ca..6ec5b717c 100644
--- a/inputfiles/removedTypes.jsonc
+++ b/inputfiles/removedTypes.jsonc
@@ -560,7 +560,6 @@
                     "member": {
                         "adAuctionHeaders": null, // Blink only as of 2023-11
                         "attributionReporting": null, // Blink only as of 2023-10
-                        "duplex": null, // Blink only as of 2023-09
                         "privateToken": null, // Blink only as of 2023-09
                         "sharedStorageWritable": null, // Blink only as of 2023-10
                         "targetAddressSpace": null // Blink only as of 2023-09