diff --git a/specification/draft/apps.mdx b/specification/draft/apps.mdx
index e5ff305..f4aa9d5 100644
--- a/specification/draft/apps.mdx
+++ b/specification/draft/apps.mdx
@@ -461,18 +461,17 @@ interface HostContext {
   displayMode?: "inline" | "fullscreen" | "pip";
   /** Display modes the host supports */
   availableDisplayModes?: string[];
-  /**
-   * Viewport dimensions available to the UI.
-   *
-   * The viewport has two independent dimension pairs:
-   * - Height: Either `height` (fixed) or `maxHeight` (flexible), never both
-   * - Width: Either `width` (fixed) or `maxWidth` (flexible), never both
-   *
-   * Fixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.
-   * Flexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified.
-   */
-  viewport?: ({ height: number } | { maxHeight?: number }) &
-    ({ width: number } | { maxWidth?: number });
+  /** Current and maximum dimensions available to the UI. */
+  viewport?: {
+    /** Current viewport width in pixels. */
+    width: number;
+    /** Current viewport height in pixels. */
+    height: number;
+    /** Maximum available height in pixels (if constrained). */
+    maxHeight?: number;
+    /** Maximum available width in pixels (if constrained). */
+    maxWidth?: number;
+  };
   /** User's language/region preference (BCP 47, e.g., "en-US") */
   locale?: string;
   /** User's timezone (IANA, e.g., "America/New_York") */
diff --git a/src/app-bridge.test.ts b/src/app-bridge.test.ts
index 3424d69..5a36b47 100644
--- a/src/app-bridge.test.ts
+++ b/src/app-bridge.test.ts
@@ -113,7 +113,7 @@ describe("App <-> AppBridge integration", () => {
       const testHostContext = {
         theme: "dark" as const,
         locale: "en-US",
-        viewport: { width: 800, maxHeight: 600 },
+        viewport: { width: 800, height: 600, maxHeight: 600 },
       };
       const newBridge = new AppBridge(
         createMockClient() as Client,
@@ -337,7 +337,7 @@ describe("App <-> AppBridge integration", () => {
       const initialContext = {
         theme: "light" as const,
         locale: "en-US",
-        viewport: { width: 800, maxHeight: 600 },
+        viewport: { width: 800, height: 600, maxHeight: 600 },
       };
       const newBridge = new AppBridge(
         createMockClient() as Client,
@@ -356,7 +356,7 @@ describe("App <-> AppBridge integration", () => {
 
       // Send another partial update: only viewport changes
       newBridge.sendHostContextChange({
-        viewport: { width: 1024, maxHeight: 768 },
+        viewport: { width: 1024, height: 768, maxHeight: 768 },
       });
       await flush();
 
@@ -367,7 +367,11 @@ describe("App <-> AppBridge integration", () => {
       const context = newApp.getHostContext();
       expect(context?.theme).toBe("dark");
       expect(context?.locale).toBe("en-US");
-      expect(context?.viewport).toEqual({ width: 1024, maxHeight: 768 });
+      expect(context?.viewport).toEqual({
+        width: 1024,
+        height: 768,
+        maxHeight: 768,
+      });
 
       await newAppTransport.close();
       await newBridgeTransport.close();
diff --git a/src/generated/schema.json b/src/generated/schema.json
index f1a458c..e835986 100644
--- a/src/generated/schema.json
+++ b/src/generated/schema.json
@@ -629,55 +629,28 @@
               }
             },
             "viewport": {
-              "description": "Viewport dimensions available to the UI.\n\nThe viewport has two independent dimension pairs:\n- Height: Either `height` (fixed) or `maxHeight` (flexible), never both\n- Width: Either `width` (fixed) or `maxWidth` (flexible), never both\n\nFixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.\nFlexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.",
-              "allOf": [
-                {
-                  "anyOf": [
-                    {
-                      "type": "object",
-                      "properties": {
-                        "height": {
-                          "type": "number"
-                        }
-                      },
-                      "required": ["height"],
-                      "additionalProperties": false
-                    },
-                    {
-                      "type": "object",
-                      "properties": {
-                        "maxHeight": {
-                          "type": "number"
-                        }
-                      },
-                      "additionalProperties": false
-                    }
-                  ]
+              "description": "Current and maximum dimensions available to the UI.",
+              "type": "object",
+              "properties": {
+                "width": {
+                  "description": "Current viewport width in pixels.",
+                  "type": "number"
                 },
-                {
-                  "anyOf": [
-                    {
-                      "type": "object",
-                      "properties": {
-                        "width": {
-                          "type": "number"
-                        }
-                      },
-                      "required": ["width"],
-                      "additionalProperties": false
-                    },
-                    {
-                      "type": "object",
-                      "properties": {
-                        "maxWidth": {
-                          "type": "number"
-                        }
-                      },
-                      "additionalProperties": false
-                    }
-                  ]
+                "height": {
+                  "description": "Current viewport height in pixels.",
+                  "type": "number"
+                },
+                "maxHeight": {
+                  "description": "Maximum available height in pixels (if constrained).",
+                  "type": "number"
+                },
+                "maxWidth": {
+                  "description": "Maximum available width in pixels (if constrained).",
+                  "type": "number"
                 }
-              ]
+              },
+              "required": ["width", "height"],
+              "additionalProperties": false
             },
             "locale": {
               "description": "User's language and region preference in BCP 47 format.",
@@ -1282,55 +1255,28 @@
           }
         },
         "viewport": {
-          "description": "Viewport dimensions available to the UI.\n\nThe viewport has two independent dimension pairs:\n- Height: Either `height` (fixed) or `maxHeight` (flexible), never both\n- Width: Either `width` (fixed) or `maxWidth` (flexible), never both\n\nFixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.\nFlexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.",
-          "allOf": [
-            {
-              "anyOf": [
-                {
-                  "type": "object",
-                  "properties": {
-                    "height": {
-                      "type": "number"
-                    }
-                  },
-                  "required": ["height"],
-                  "additionalProperties": false
-                },
-                {
-                  "type": "object",
-                  "properties": {
-                    "maxHeight": {
-                      "type": "number"
-                    }
-                  },
-                  "additionalProperties": false
-                }
-              ]
+          "description": "Current and maximum dimensions available to the UI.",
+          "type": "object",
+          "properties": {
+            "width": {
+              "description": "Current viewport width in pixels.",
+              "type": "number"
             },
-            {
-              "anyOf": [
-                {
-                  "type": "object",
-                  "properties": {
-                    "width": {
-                      "type": "number"
-                    }
-                  },
-                  "required": ["width"],
-                  "additionalProperties": false
-                },
-                {
-                  "type": "object",
-                  "properties": {
-                    "maxWidth": {
-                      "type": "number"
-                    }
-                  },
-                  "additionalProperties": false
-                }
-              ]
+            "height": {
+              "description": "Current viewport height in pixels.",
+              "type": "number"
+            },
+            "maxHeight": {
+              "description": "Maximum available height in pixels (if constrained).",
+              "type": "number"
+            },
+            "maxWidth": {
+              "description": "Maximum available width in pixels (if constrained).",
+              "type": "number"
             }
-          ]
+          },
+          "required": ["width", "height"],
+          "additionalProperties": false
         },
         "locale": {
           "description": "User's language and region preference in BCP 47 format.",
@@ -2468,55 +2414,28 @@
               }
             },
             "viewport": {
-              "description": "Viewport dimensions available to the UI.\n\nThe viewport has two independent dimension pairs:\n- Height: Either `height` (fixed) or `maxHeight` (flexible), never both\n- Width: Either `width` (fixed) or `maxWidth` (flexible), never both\n\nFixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.\nFlexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.",
-              "allOf": [
-                {
-                  "anyOf": [
-                    {
-                      "type": "object",
-                      "properties": {
-                        "height": {
-                          "type": "number"
-                        }
-                      },
-                      "required": ["height"],
-                      "additionalProperties": false
-                    },
-                    {
-                      "type": "object",
-                      "properties": {
-                        "maxHeight": {
-                          "type": "number"
-                        }
-                      },
-                      "additionalProperties": false
-                    }
-                  ]
+              "description": "Current and maximum dimensions available to the UI.",
+              "type": "object",
+              "properties": {
+                "width": {
+                  "description": "Current viewport width in pixels.",
+                  "type": "number"
                 },
-                {
-                  "anyOf": [
-                    {
-                      "type": "object",
-                      "properties": {
-                        "width": {
-                          "type": "number"
-                        }
-                      },
-                      "required": ["width"],
-                      "additionalProperties": false
-                    },
-                    {
-                      "type": "object",
-                      "properties": {
-                        "maxWidth": {
-                          "type": "number"
-                        }
-                      },
-                      "additionalProperties": false
-                    }
-                  ]
+                "height": {
+                  "description": "Current viewport height in pixels.",
+                  "type": "number"
+                },
+                "maxHeight": {
+                  "description": "Maximum available height in pixels (if constrained).",
+                  "type": "number"
+                },
+                "maxWidth": {
+                  "description": "Maximum available width in pixels (if constrained).",
+                  "type": "number"
                 }
-              ]
+              },
+              "required": ["width", "height"],
+              "additionalProperties": false
             },
             "locale": {
               "description": "User's language and region preference in BCP 47 format.",
diff --git a/src/generated/schema.ts b/src/generated/schema.ts
index 5558961..5e59edc 100644
--- a/src/generated/schema.ts
+++ b/src/generated/schema.ts
@@ -562,39 +562,26 @@ export const McpUiHostContextSchema = z.looseObject({
     .array(z.string())
     .optional()
     .describe("Display modes the host supports."),
-  /**
-   * @description Viewport dimensions available to the UI.
-   *
-   * The viewport has two independent dimension pairs:
-   * - Height: Either `height` (fixed) or `maxHeight` (flexible), never both
-   * - Width: Either `width` (fixed) or `maxWidth` (flexible), never both
-   *
-   * Fixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.
-   * Flexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.
-   */
+  /** @description Current and maximum dimensions available to the UI. */
   viewport: z
-    .union([
-      z.object({
-        height: z.number(),
-      }),
-      z.object({
-        maxHeight: z.number().optional(),
-      }),
-    ])
-    .and(
-      z.union([
-        z.object({
-          width: z.number(),
-        }),
-        z.object({
-          maxWidth: z.number().optional(),
-        }),
-      ]),
-    )
+    .object({
+      /** @description Current viewport width in pixels. */
+      width: z.number().describe("Current viewport width in pixels."),
+      /** @description Current viewport height in pixels. */
+      height: z.number().describe("Current viewport height in pixels."),
+      /** @description Maximum available height in pixels (if constrained). */
+      maxHeight: z
+        .number()
+        .optional()
+        .describe("Maximum available height in pixels (if constrained)."),
+      /** @description Maximum available width in pixels (if constrained). */
+      maxWidth: z
+        .number()
+        .optional()
+        .describe("Maximum available width in pixels (if constrained)."),
+    })
     .optional()
-    .describe(
-      "Viewport dimensions available to the UI.\n\nThe viewport has two independent dimension pairs:\n- Height: Either `height` (fixed) or `maxHeight` (flexible), never both\n- Width: Either `width` (fixed) or `maxWidth` (flexible), never both\n\nFixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.\nFlexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.",
-    ),
+    .describe("Current and maximum dimensions available to the UI."),
   /** @description User's language and region preference in BCP 47 format. */
   locale: z
     .string()
diff --git a/src/spec.types.ts b/src/spec.types.ts
index 1a0c8c2..f97a0a6 100644
--- a/src/spec.types.ts
+++ b/src/spec.types.ts
@@ -324,18 +324,17 @@ export interface McpUiHostContext {
   displayMode?: McpUiDisplayMode;
   /** @description Display modes the host supports. */
   availableDisplayModes?: string[];
-  /**
-   * @description Viewport dimensions available to the UI.
-   *
-   * The viewport has two independent dimension pairs:
-   * - Height: Either `height` (fixed) or `maxHeight` (flexible), never both
-   * - Width: Either `width` (fixed) or `maxWidth` (flexible), never both
-   *
-   * Fixed dimensions (height/width): The host controls the size. Set height: 100% (recommended) or use the pixel value directly.
-   * Flexible dimensions (maxHeight/maxWidth or undefined): The app controls the size, up to the max if specified. If undefined, there is no limit.
-   */
-  viewport?: ({ height: number } | { maxHeight?: number }) &
-    ({ width: number } | { maxWidth?: number });
+  /** @description Current and maximum dimensions available to the UI. */
+  viewport?: {
+    /** @description Current viewport width in pixels. */
+    width: number;
+    /** @description Current viewport height in pixels. */
+    height: number;
+    /** @description Maximum available height in pixels (if constrained). */
+    maxHeight?: number;
+    /** @description Maximum available width in pixels (if constrained). */
+    maxWidth?: number;
+  };
   /** @description User's language and region preference in BCP 47 format. */
   locale?: string;
   /** @description User's timezone in IANA format. */