SDK v2 migration (behavior-neutral, versionNegotiation: 'legacy') (#1624)

Migrate all three clients + core + test-servers from
@modelcontextprotocol/sdk@1.29 to SDK v2 (2.0.0-beta.4), keeping behavior
identical against legacy (2025-11-25) servers. Foundation for the SDK V2 +
New Spec stack.

Packages
- Split @modelcontextprotocol/sdk -> @modelcontextprotocol/client (Client,
  transports, OAuth, error taxonomy, protocol types) + core (Zod schemas);
  stdio -> client/stdio, Ajv -> client/validators/ajv. Test-servers ->
  @modelcontextprotocol/server (+ server-legacy/sse). Deterministic import
  rewrite (schemas -> core, everything else -> client); the codemod misroutes
  client code to /server so it was not used for path routing.
- new Client(..., { versionNegotiation: { mode: 'legacy' } }) — nothing
  2026-era goes on the wire.

Runtime (core/mcp/inspectorClient.ts)
- Error taxonomy: McpError -> ProtocolError, ErrorCode -> ProtocolErrorCode;
  RequestTimeout -> SdkError/SdkErrorCode.
- Handlers take method strings; task methods (tasks/*, notifications/tasks/*)
  use the 3-arg custom form (excluded from v2's spec-method set).
- Legacy tasks kept working (per project requirement): requestor tasks re-
  implemented over raw client.request + explicit deprecated schemas;
  experimental.tasks.callToolStream replaced by a local pollTaskToolCall
  async generator (with _progressHandlers revival so task-execution progress
  still reaches the caller). Receiver (server-initiated) tasks: the v2 Client
  validates a sampling/elicit handler result and rejects the legacy { task }
  response with -32602 — installReceiverTaskResponseBypass swaps the wrapped
  entry in the private _requestHandlers map for the task-augmented branch so
  { task } reaches the wire (fixes server-initiated sampling-via-task).
- Pagination: list verbs use raw client.request({method}, List*ResultSchema)
  for single-page behavior (v2's client.listX() auto-aggregate all pages).

Web / auth / apps
- Rename local JsonSchemaType -> InspectorFormSchema + add toFormSchema()
  structural narrowing at the SDK-schema -> form boundary.
- ext-apps still peers on SDK v1: one compat boundary with documented casts
  (remove when ext-apps#702 lands a v2 peer).
- OAuth provider saveClientInformation reconciled with v2's
  OAuthClientInformationContext; InvalidClientMetadataError re-homed as a
  local class (server-legacy/auth is not browser-safe).
- vitest.shared.mts dedupes @modelcontextprotocol/client+core to one copy so
  vi.mock intercepts the SUT's import.

Accepted v2 behavior changes (per #1624 / spec §9.2): unknown-tool call
rejects with -32602; cancellation is stream-abort (no guaranteed
notifications/cancelled frame); output-schema strictness restored via the
Inspector's own Ajv check on the default path.

npm run ci green: validate (web 3087 / cli 212 / tui 274 / launcher 5),
coverage (>=90 per-file, all clients), smoke (launcher/cli/web), storybook
(410).

Closes #1624

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

clients/tui/src/App.tsx

@@ -18,7 +18,7 @@ import type {
   Prompt,
   PromptArgument,
   GetPromptResult,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/client";
 import { InspectorClient } from "@inspector/core/mcp/index.js";
 import {
   ManagedToolsState,
@@ -923,7 +923,7 @@ function App({
     resource:
       | Resource
       | {
-          content: import("@modelcontextprotocol/sdk/types.js").ReadResourceResult;
+          content: import("@modelcontextprotocol/client").ReadResourceResult;
         },
   ) => (
     <>

clients/tui/src/components/PromptTestModal.tsx

@@ -3,10 +3,7 @@ import { Box, Text, useInput, type Key } from "ink";
 import { Form } from "ink-form";
 import { InspectorClient } from "@inspector/core/mcp/index.js";
 import { AuthRecoveryRequiredError } from "@inspector/core/auth/challenge.js";
-import type {
-  Prompt,
-  GetPromptResult,
-} from "@modelcontextprotocol/sdk/types.js";
+import type { Prompt, GetPromptResult } from "@modelcontextprotocol/client";
 import { promptArgsToForm } from "../utils/promptArgsToForm.js";
 import { ScrollView, type ScrollViewRef } from "ink-scroll-view";
 

clients/tui/src/components/PromptsTab.tsx

@@ -7,7 +7,7 @@ import type {
   Prompt,
   PromptArgument,
   GetPromptResult,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/client";
 import { useSelectableList } from "../hooks/useSelectableList.js";
 
 interface PromptsTabProps {

clients/tui/src/components/ResourceTestModal.tsx

@@ -3,7 +3,7 @@ import { Box, Text, useInput, type Key } from "ink";
 import { Form } from "ink-form";
 import { InspectorClient } from "@inspector/core/mcp/index.js";
 import { AuthRecoveryRequiredError } from "@inspector/core/auth/challenge.js";
-import type { ReadResourceResult } from "@modelcontextprotocol/sdk/types.js";
+import type { ReadResourceResult } from "@modelcontextprotocol/client";
 import { uriTemplateToForm } from "../utils/uriTemplateToForm.js";
 import { ScrollView, type ScrollViewRef } from "ink-scroll-view";
 

clients/tui/src/components/ResourcesTab.tsx

@@ -6,7 +6,7 @@ import { AuthRecoveryRequiredError } from "@inspector/core/auth/challenge.js";
 import type {
   Resource,
   ReadResourceResult,
-} from "@modelcontextprotocol/sdk/types.js";
+} from "@modelcontextprotocol/client";
 import { useSelectableList } from "../hooks/useSelectableList.js";
 
 interface ResourceTemplate {

clients/tui/src/components/ToolTestModal.tsx

@@ -3,7 +3,7 @@ import { Box, Text, useInput, type Key } from "ink";
 import { Form } from "ink-form";
 import { InspectorClient } from "@inspector/core/mcp/index.js";
 import { AuthRecoveryRequiredError } from "@inspector/core/auth/challenge.js";
-import type { Tool, CallToolResult } from "@modelcontextprotocol/sdk/types.js";
+import type { Tool, CallToolResult } from "@modelcontextprotocol/client";
 import type { JsonValue } from "@inspector/core/mcp/index.js";
 import { schemaToForm } from "../utils/schemaToForm.js";
 import { ScrollView, type ScrollViewRef } from "ink-scroll-view";

clients/tui/src/components/ToolsTab.tsx

@@ -1,7 +1,7 @@
 import React, { useState, useEffect, useRef } from "react";
 import { Box, Text, useInput, type Key } from "ink";
 import { ScrollView, type ScrollViewRef } from "ink-scroll-view";
-import type { Tool } from "@modelcontextprotocol/sdk/types.js";
+import type { Tool } from "@modelcontextprotocol/client";
 import { useSelectableList } from "../hooks/useSelectableList.js";
 
 interface ToolsTabProps {

clients/tui/src/utils/promptArgsToForm.ts

@@ -3,7 +3,7 @@
  */
 
 import type { FormStructure, FormSection, FormField } from "ink-form";
-import type { PromptArgument } from "@modelcontextprotocol/sdk/types.js";
+import type { PromptArgument } from "@modelcontextprotocol/client";
 
 /**
  * Converts prompt arguments array to ink-form structure

clients/tui/src/utils/uriTemplateToForm.ts

@@ -3,7 +3,7 @@
  */
 
 import type { FormStructure, FormSection, FormField } from "ink-form";
-import { UriTemplate } from "@modelcontextprotocol/sdk/shared/uriTemplate.js";
+import { UriTemplate } from "@modelcontextprotocol/client";
 
 /**
  * Converts a URI Template to ink-form structure