diff --git a/java/src/main/java/com/github/copilot/rpc/PermissionRequest.java b/java/src/main/java/com/github/copilot/rpc/PermissionRequest.java
index a3297bfb2..fc49332b8 100644
--- a/java/src/main/java/com/github/copilot/rpc/PermissionRequest.java
+++ b/java/src/main/java/com/github/copilot/rpc/PermissionRequest.java
@@ -5,8 +5,10 @@
 package com.github.copilot.rpc;
 
 import java.io.IOException;
+import java.util.LinkedHashMap;
 import java.util.Map;
 
+import com.fasterxml.jackson.annotation.JsonAnySetter;
 import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
 import com.fasterxml.jackson.annotation.JsonInclude;
 import com.fasterxml.jackson.annotation.JsonProperty;
@@ -45,6 +47,14 @@ public class PermissionRequest {
 
     private Map<String, Object> extensionData;
 
+    @JsonAnySetter
+    private void setExtensionDataEntry(String key, Object value) {
+        if (extensionData == null) {
+            extensionData = new LinkedHashMap<>();
+        }
+        extensionData.put(key, value);
+    }
+
     private static final class ManagedApprovalRequiredDeserializer extends JsonDeserializer<Boolean> {
 
         @Override
diff --git a/java/src/test/java/com/github/copilot/DataObjectCoverageTest.java b/java/src/test/java/com/github/copilot/DataObjectCoverageTest.java
index f38a03836..f95c5bcc5 100644
--- a/java/src/test/java/com/github/copilot/DataObjectCoverageTest.java
+++ b/java/src/test/java/com/github/copilot/DataObjectCoverageTest.java
@@ -139,6 +139,27 @@ void permissionRequestSetExtensionData() {
         assertEquals("value", req.getExtensionData().get("key"));
     }
 
+    @Test
+    void permissionRequestPreservesMcpExtensionData() {
+        var request = PermissionRequest.fromJsonValue(
+                java.util.Map.of("kind", "mcp", "serverName", "playwright", "toolName", "playwright-browser_navigate",
+                        "args", java.util.Map.of("url", "http://127.0.0.1:8106/docs/target-app/")));
+
+        assertEquals("mcp", request.getKind());
+        assertEquals("playwright", request.getExtensionData().get("serverName"));
+        assertEquals("playwright-browser_navigate", request.getExtensionData().get("toolName"));
+        @SuppressWarnings("unchecked")
+        var args = (java.util.Map<String, Object>) request.getExtensionData().get("args");
+        assertEquals("http://127.0.0.1:8106/docs/target-app/", args.get("url"));
+    }
+
+    @Test
+    void permissionRequestWithoutExtensionDataPreservesNull() {
+        var request = PermissionRequest.fromJsonValue(java.util.Map.of("kind", "read", "toolCallId", "tool-123"));
+
+        assertNull(request.getExtensionData());
+    }
+
     // ===== SectionOverride setContent =====
 
     @Test