diff --git a/scripts/generate-schemas.ts b/scripts/generate-schemas.ts
index 109f352..85225f5 100644
--- a/scripts/generate-schemas.ts
+++ b/scripts/generate-schemas.ts
@@ -12,7 +12,7 @@
  *
  * ts-to-zod generates `import { z } from "zod"`. We rewrite this to
  * `import { z } from "zod/v4"` because the generated schemas compose with
- * schemas imported from `@modelcontextprotocol/sdk/types.js`, which the SDK
+ * schemas imported from `@modelcontextprotocol/core`, which the SDK
  * constructs via `zod/v4`. Mixing schemas from the v3 and v4 APIs at runtime
  * fails with errors like `keyValidator._parse is not a function` (v3 internals
  * calling into v4 objects, or vice versa). The `zod/v4` subpath is exported by
@@ -22,7 +22,7 @@
  *
  * **Problem**: ts-to-zod cannot resolve types imported from external packages.
  * When it encounters types like `ContentBlock`, `CallToolResult`, `Implementation`,
- * `RequestId`, and `Tool` from `@modelcontextprotocol/sdk`, it generates `z.any()`
+ * `RequestId`, and `Tool` from `@modelcontextprotocol/core`, it generates `z.any()`
  * as a placeholder.
  *
  * **Solution**: Import the schemas from MCP SDK and remove the z.any() placeholders.
@@ -193,7 +193,7 @@ function postProcess(content: string): string {
     `import { z } from "zod/v4";
 import {
   ${mcpImports},
-} from "@modelcontextprotocol/sdk/types.js";`,
+} from "@modelcontextprotocol/core";`,
   );
 
   // 2. Remove z.any() placeholders for external types (now imported from MCP SDK)
diff --git a/src/generated/schema.json b/src/generated/schema.json
index 80b4ac6..5f2124a 100644
--- a/src/generated/schema.json
+++ b/src/generated/schema.json
@@ -596,7 +596,9 @@
                           "propertyNames": {
                             "type": "string"
                           },
-                          "additionalProperties": {}
+                          "additionalProperties": {
+                            "$ref": "#/$defs/__schema0"
+                          }
                         },
                         "required": {
                           "type": "array",
@@ -611,25 +613,10 @@
                     "outputSchema": {
                       "type": "object",
                       "properties": {
-                        "type": {
-                          "type": "string",
-                          "const": "object"
-                        },
-                        "properties": {
-                          "type": "object",
-                          "propertyNames": {
-                            "type": "string"
-                          },
-                          "additionalProperties": {}
-                        },
-                        "required": {
-                          "type": "array",
-                          "items": {
-                            "type": "string"
-                          }
+                        "$schema": {
+                          "type": "string"
                         }
                       },
-                      "required": ["type"],
                       "additionalProperties": {}
                     },
                     "annotations": {
@@ -1286,7 +1273,40 @@
         }
       },
       "required": ["method", "params"],
-      "additionalProperties": false
+      "additionalProperties": false,
+      "$defs": {
+        "__schema0": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "number"
+            },
+            {
+              "type": "boolean"
+            },
+            {
+              "type": "null"
+            },
+            {
+              "type": "object",
+              "propertyNames": {
+                "type": "string"
+              },
+              "additionalProperties": {
+                "$ref": "#/$defs/__schema0"
+              }
+            },
+            {
+              "type": "array",
+              "items": {
+                "$ref": "#/$defs/__schema0"
+              }
+            }
+          ]
+        }
+      }
     },
     "McpUiHostContext": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
@@ -1359,7 +1379,9 @@
                       "propertyNames": {
                         "type": "string"
                       },
-                      "additionalProperties": {}
+                      "additionalProperties": {
+                        "$ref": "#/$defs/__schema0"
+                      }
                     },
                     "required": {
                       "type": "array",
@@ -1374,25 +1396,10 @@
                 "outputSchema": {
                   "type": "object",
                   "properties": {
-                    "type": {
-                      "type": "string",
-                      "const": "object"
-                    },
-                    "properties": {
-                      "type": "object",
-                      "propertyNames": {
-                        "type": "string"
-                      },
-                      "additionalProperties": {}
-                    },
-                    "required": {
-                      "type": "array",
-                      "items": {
-                        "type": "string"
-                      }
+                    "$schema": {
+                      "type": "string"
                     }
                   },
-                  "required": ["type"],
                   "additionalProperties": {}
                 },
                 "annotations": {
@@ -2044,7 +2051,40 @@
           "additionalProperties": false
         }
       },
-      "additionalProperties": {}
+      "additionalProperties": {},
+      "$defs": {
+        "__schema0": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "number"
+            },
+            {
+              "type": "boolean"
+            },
+            {
+              "type": "null"
+            },
+            {
+              "type": "object",
+              "propertyNames": {
+                "type": "string"
+              },
+              "additionalProperties": {
+                "$ref": "#/$defs/__schema0"
+              }
+            },
+            {
+              "type": "array",
+              "items": {
+                "$ref": "#/$defs/__schema0"
+              }
+            }
+          ]
+        }
+      }
     },
     "McpUiHostCss": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
@@ -2942,7 +2982,9 @@
                           "propertyNames": {
                             "type": "string"
                           },
-                          "additionalProperties": {}
+                          "additionalProperties": {
+                            "$ref": "#/$defs/__schema0"
+                          }
                         },
                         "required": {
                           "type": "array",
@@ -2957,25 +2999,10 @@
                     "outputSchema": {
                       "type": "object",
                       "properties": {
-                        "type": {
-                          "type": "string",
-                          "const": "object"
-                        },
-                        "properties": {
-                          "type": "object",
-                          "propertyNames": {
-                            "type": "string"
-                          },
-                          "additionalProperties": {}
-                        },
-                        "required": {
-                          "type": "array",
-                          "items": {
-                            "type": "string"
-                          }
+                        "$schema": {
+                          "type": "string"
                         }
                       },
-                      "required": ["type"],
                       "additionalProperties": {}
                     },
                     "annotations": {
@@ -3637,7 +3664,40 @@
         "hostCapabilities",
         "hostContext"
       ],
-      "additionalProperties": {}
+      "additionalProperties": {},
+      "$defs": {
+        "__schema0": {
+          "anyOf": [
+            {
+              "type": "string"
+            },
+            {
+              "type": "number"
+            },
+            {
+              "type": "boolean"
+            },
+            {
+              "type": "null"
+            },
+            {
+              "type": "object",
+              "propertyNames": {
+                "type": "string"
+              },
+              "additionalProperties": {
+                "$ref": "#/$defs/__schema0"
+              }
+            },
+            {
+              "type": "array",
+              "items": {
+                "$ref": "#/$defs/__schema0"
+              }
+            }
+          ]
+        }
+      }
     },
     "McpUiInitializedNotification": {
       "$schema": "https://json-schema.org/draft/2020-12/schema",
@@ -5669,13 +5729,7 @@
                 ]
               }
             },
-            "structuredContent": {
-              "type": "object",
-              "propertyNames": {
-                "type": "string"
-              },
-              "additionalProperties": {}
-            },
+            "structuredContent": {},
             "isError": {
               "type": "boolean"
             }
diff --git a/src/generated/schema.ts b/src/generated/schema.ts
index 4368737..341c7b4 100644
--- a/src/generated/schema.ts
+++ b/src/generated/schema.ts
@@ -10,7 +10,7 @@ import {
   RequestIdSchema,
   ResourceLinkSchema,
   ToolSchema,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/core";
 
 /**
  * @description Color theme preference for the host environment.
diff --git a/src/message-transport.ts b/src/message-transport.ts
index 9d19543..9483540 100644
--- a/src/message-transport.ts
+++ b/src/message-transport.ts
@@ -1,12 +1,10 @@
-import {
+import { JSONRPCMessageSchema } from "@modelcontextprotocol/core";
+import type {
   JSONRPCMessage,
-  JSONRPCMessageSchema,
   MessageExtraInfo,
-} from "@modelcontextprotocol/sdk/types.js";
-import {
   Transport,
   TransportSendOptions,
-} from "@modelcontextprotocol/sdk/shared/transport.js";
+} from "@modelcontextprotocol/client";
 import { TOOL_INPUT_PARTIAL_METHOD } from "./spec.types";
 
 /**
diff --git a/src/react/useApp.tsx b/src/react/useApp.tsx
index 6189246..0e64a74 100644
--- a/src/react/useApp.tsx
+++ b/src/react/useApp.tsx
@@ -1,6 +1,5 @@
 import { useEffect, useState } from "react";
-import { Implementation } from "@modelcontextprotocol/sdk/types.js";
-import { Client } from "@modelcontextprotocol/sdk/client";
+import type { Implementation } from "@modelcontextprotocol/client";
 import {
   App,
   AppOptions,
diff --git a/src/server/index.ts b/src/server/index.ts
index c90514a..b8b3ad0 100644
--- a/src/server/index.ts
+++ b/src/server/index.ts
@@ -40,24 +40,17 @@ import {
   McpUiClientCapabilities,
 } from "../app.js";
 import type {
-  BaseToolCallback,
+  ClientCapabilities,
   McpServer,
+  ReadResourceResult,
   RegisteredTool,
   ResourceMetadata,
+  StandardSchemaWithJSON,
+  ToolAnnotations,
   ToolCallback,
   ReadResourceCallback as _ReadResourceCallback,
   RegisteredResource,
-} from "@modelcontextprotocol/sdk/server/mcp.js";
-import type {
-  AnySchema,
-  ZodRawShapeCompat,
-} from "@modelcontextprotocol/sdk/server/zod-compat.js";
-import type { StandardSchemaWithJSON } from "../standard-schema";
-import type {
-  ClientCapabilities,
-  ReadResourceResult,
-  ToolAnnotations,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/server";
 
 // Re-exports for convenience
 export { RESOURCE_URI_META_KEY, RESOURCE_MIME_TYPE };
@@ -70,8 +63,8 @@ export type { ResourceMetadata, ToolCallback };
 export interface ToolConfig {
   title?: string;
   description?: string;
-  inputSchema?: ZodRawShapeCompat | StandardSchemaWithJSON;
-  outputSchema?: ZodRawShapeCompat | StandardSchemaWithJSON;
+  inputSchema?: StandardSchemaWithJSON;
+  outputSchema?: StandardSchemaWithJSON;
   annotations?: ToolAnnotations;
   _meta?: Record<string, unknown>;
 }
@@ -215,9 +208,8 @@ export interface McpUiAppResourceConfig extends ResourceMetadata {
  * @see {@link registerAppResource `registerAppResource`} to register the HTML resource referenced by the tool
  */
 export function registerAppTool<
-  OutputArgs extends ZodRawShapeCompat | StandardSchemaWithJSON,
-  InputArgs extends undefined | ZodRawShapeCompat | StandardSchemaWithJSON =
-    undefined,
+  OutputArgs extends StandardSchemaWithJSON,
+  InputArgs extends StandardSchemaWithJSON | undefined = undefined,
 >(
   server: Pick<McpServer, "registerTool">,
   name: string,
@@ -225,15 +217,7 @@ export function registerAppTool<
     inputSchema?: InputArgs;
     outputSchema?: OutputArgs;
   },
-  // The widened constraint signals the v2 API shape, but NOTE: McpServer in
-  // sdk@1.x still calls zod internals at runtime, so non-zod schemas will fail
-  // here until we depend on sdk v2. Zod (which all current callers use) is
-  // unaffected. The cast below bridges the 1.x type signature.
-  cb: ToolCallback<
-    InputArgs extends undefined | ZodRawShapeCompat | AnySchema
-      ? InputArgs
-      : AnySchema
-  >,
+  cb: ToolCallback<InputArgs>,
 ): RegisteredTool {
   // Normalize metadata for backward compatibility:
   // - If _meta.ui.resourceUri is set, also set the legacy flat key
@@ -251,14 +235,7 @@ export function registerAppTool<
     normalizedMeta = { ...meta, ui: { ...uiMeta, resourceUri: legacyUri } };
   }
 
-  // Cast bridges the widened StandardSchemaWithJSON constraint to the
-  // sdk@1.x zod-typed signature. Drops once we depend on sdk v2.
-  // eslint-disable-next-line @typescript-eslint/no-explicit-any
-  return server.registerTool(
-    name,
-    { ...config, _meta: normalizedMeta } as any,
-    cb as any,
-  );
+  return server.registerTool(name, { ...config, _meta: normalizedMeta }, cb);
 }
 
 export type McpUiReadResourceResult = ReadResourceResult & {
@@ -418,10 +395,6 @@ export const EXTENSION_ID = "io.modelcontextprotocol/ui";
  * This helper retrieves the capability object from the `extensions` field
  * where MCP Apps advertises its support.
  *
- * Note: The `clientCapabilities` parameter extends the SDK's `ClientCapabilities`
- * type with an `extensions` field (pending SEP-1724). Once `extensions` is added
- * to the SDK, this can use `ClientCapabilities` directly.
- *
  * @param clientCapabilities - The client capabilities from the initialize response
  * @returns The MCP Apps capability settings, or `undefined` if not supported
  *
@@ -456,10 +429,7 @@ export const EXTENSION_ID = "io.modelcontextprotocol/ui";
  * ```
  */
 export function getUiCapability(
-  clientCapabilities:
-    | (ClientCapabilities & { extensions?: Record<string, unknown> })
-    | null
-    | undefined,
+  clientCapabilities: ClientCapabilities | null | undefined,
 ): McpUiClientCapabilities | undefined {
   if (!clientCapabilities) {
     return undefined;
diff --git a/src/spec.types.ts b/src/spec.types.ts
index 7a8b337..8b03de9 100644
--- a/src/spec.types.ts
+++ b/src/spec.types.ts
@@ -18,7 +18,7 @@ import type {
   RequestId,
   ResourceLink,
   Tool,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/client";
 
 /**
  * Current protocol version supported by this SDK.
@@ -163,8 +163,8 @@ export interface McpUiOpenLinkResult {
   /** @description True if the host failed to open the URL (e.g., due to security policy). */
   isError?: boolean;
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
-   * Note: The generated schema uses passthrough() to allow additional properties.
+   * Additional result properties are preserved for protocol extensibility.
+   * The generated schema uses passthrough() to allow them.
    */
   [key: string]: unknown;
 }
@@ -195,8 +195,8 @@ export interface McpUiDownloadFileResult {
   /** @description True if the download failed (e.g., user cancelled or host denied). */
   isError?: boolean;
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
-   * Note: The generated schema uses passthrough() to allow additional properties.
+   * Additional result properties are preserved for protocol extensibility.
+   * The generated schema uses passthrough() to allow them.
    */
   [key: string]: unknown;
 }
@@ -223,8 +223,8 @@ export interface McpUiMessageResult {
   /** @description True if the host rejected or failed to deliver the message. */
   isError?: boolean;
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
-   * Note: The generated schema uses passthrough() to allow additional properties.
+   * Additional result properties are preserved for protocol extensibility.
+   * The generated schema uses passthrough() to allow them.
    */
   [key: string]: unknown;
 }
@@ -454,7 +454,7 @@ export interface McpUiResourceTeardownRequest {
  */
 export interface McpUiResourceTeardownResult {
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
+   * Additional result properties are preserved for protocol extensibility.
    */
   [key: string]: unknown;
 }
@@ -577,8 +577,8 @@ export interface McpUiInitializeResult {
   /** @description Rich context about the host environment. */
   hostContext: McpUiHostContext;
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
-   * Note: The generated schema uses passthrough() to allow additional properties.
+   * Additional result properties are preserved for protocol extensibility.
+   * The generated schema uses passthrough() to allow them.
    */
   [key: string]: unknown;
 }
@@ -752,7 +752,7 @@ export interface McpUiRequestDisplayModeResult {
   /** @description The display mode that was actually set. May differ from requested if not supported. */
   mode: McpUiDisplayMode;
   /**
-   * Index signature required for MCP SDK `Protocol` class compatibility.
+   * Additional result properties are preserved for protocol extensibility.
    * Note: The generated schema uses passthrough() to allow additional properties.
    */
   [key: string]: unknown;
diff --git a/src/types.ts b/src/types.ts
index 7fc6b71..655812b 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -69,33 +69,6 @@ export {
   type McpUiClientCapabilities,
 } from "./spec.types.js";
 
-// Import types needed for protocol type unions (not re-exported, just used internally)
-import type {
-  McpUiInitializeRequest,
-  McpUiOpenLinkRequest,
-  McpUiDownloadFileRequest,
-  McpUiMessageRequest,
-  McpUiUpdateModelContextRequest,
-  McpUiResourceTeardownRequest,
-  McpUiRequestDisplayModeRequest,
-  McpUiHostContextChangedNotification,
-  McpUiToolInputNotification,
-  McpUiToolInputPartialNotification,
-  McpUiToolResultNotification,
-  McpUiToolCancelledNotification,
-  McpUiSandboxResourceReadyNotification,
-  McpUiInitializedNotification,
-  McpUiSizeChangedNotification,
-  McpUiSandboxProxyReadyNotification,
-  McpUiRequestTeardownNotification,
-  McpUiInitializeResult,
-  McpUiOpenLinkResult,
-  McpUiDownloadFileResult,
-  McpUiMessageResult,
-  McpUiResourceTeardownResult,
-  McpUiRequestDisplayModeResult,
-} from "./spec.types.js";
-
 // Re-export all schemas from generated/schema.ts (already PascalCase)
 export {
   McpUiThemeSchema,
@@ -135,106 +108,3 @@ export {
   McpUiToolVisibilitySchema,
   McpUiToolMetaSchema,
 } from "./generated/schema.js";
-
-// Re-export SDK types used in protocol type unions
-import {
-  CallToolRequest,
-  CallToolResult,
-  CreateMessageRequest,
-  CreateMessageResult,
-  CreateMessageResultWithTools,
-  EmptyResult,
-  ListPromptsRequest,
-  ListPromptsResult,
-  ListResourcesRequest,
-  ListResourcesResult,
-  ListResourceTemplatesRequest,
-  ListResourceTemplatesResult,
-  ListToolsRequest,
-  ListToolsResult,
-  LoggingMessageNotification,
-  PingRequest,
-  PromptListChangedNotification,
-  ReadResourceRequest,
-  ReadResourceResult,
-  ResourceListChangedNotification,
-  ToolListChangedNotification,
-} from "@modelcontextprotocol/sdk/types.js";
-
-/**
- * All request types in the MCP Apps protocol.
- *
- * Includes:
- * - MCP UI requests (initialize, open-link, message, resource-teardown, request-display-mode)
- * - MCP server requests forwarded from the app (tools/call, tools/list, resources/list,
- *   resources/templates/list, resources/read, prompts/list)
- * - MCP client requests forwarded to the host (sampling/createMessage)
- * - Protocol requests (ping)
- */
-export type AppRequest =
-  | McpUiInitializeRequest
-  | McpUiOpenLinkRequest
-  | McpUiDownloadFileRequest
-  | McpUiMessageRequest
-  | McpUiUpdateModelContextRequest
-  | McpUiResourceTeardownRequest
-  | McpUiRequestDisplayModeRequest
-  | CallToolRequest
-  | ListToolsRequest
-  | ListResourcesRequest
-  | ListResourceTemplatesRequest
-  | ReadResourceRequest
-  | ListPromptsRequest
-  | CreateMessageRequest
-  | PingRequest;
-
-/**
- * All notification types in the MCP Apps protocol.
- *
- * Host to app:
- * - Tool lifecycle (input, input-partial, result, cancelled)
- * - Host context changes
- * - MCP list changes (tools, resources, prompts)
- * - Sandbox resource ready
- *
- * App to host:
- * - Initialized, size-changed, sandbox-proxy-ready, request-teardown
- * - Logging messages
- */
-export type AppNotification =
-  // Sent to app
-  | McpUiHostContextChangedNotification
-  | McpUiToolInputNotification
-  | McpUiToolInputPartialNotification
-  | McpUiToolResultNotification
-  | McpUiToolCancelledNotification
-  | McpUiSandboxResourceReadyNotification
-  | ToolListChangedNotification
-  | ResourceListChangedNotification
-  | PromptListChangedNotification
-  // Received from app
-  | McpUiInitializedNotification
-  | McpUiSizeChangedNotification
-  | McpUiSandboxProxyReadyNotification
-  | McpUiRequestTeardownNotification
-  | LoggingMessageNotification;
-
-/**
- * All result types in the MCP Apps protocol.
- */
-export type AppResult =
-  | McpUiInitializeResult
-  | McpUiOpenLinkResult
-  | McpUiDownloadFileResult
-  | McpUiMessageResult
-  | McpUiResourceTeardownResult
-  | McpUiRequestDisplayModeResult
-  | CallToolResult
-  | ListToolsResult
-  | ListResourcesResult
-  | ListResourceTemplatesResult
-  | ReadResourceResult
-  | ListPromptsResult
-  | CreateMessageResult
-  | CreateMessageResultWithTools
-  | EmptyResult;