### Preflight Checklist - [x] I have searched [existing issues](https://github.com/anthropics/claude-code/issues?q=is%3Aissue%20state%3Aopen%20label%3Abug) and this hasn't been reported yet - [x] This is a single bug report (please file separate reports for different bugs) - [x] I am using the latest version of Claude Code ### What's Wrong? Claude Code `1.0.120` release breaks the MCP server. ```json { "mcpServers": { "claude": { "command": "claude", "args": [ "mcp"

[BUG] MCP server broken on 1.0.120 release

Status Fixed / completed

Maintainer reply None cached

Activity 12 comments · opened Sep 22, 2025 · closed Nov 10, 2025

Preflight Checklist

[x] I have searched existing issues and this hasn't been reported yet
[x] This is a single bug report (please file separate reports for different bugs)
[x] I am using the latest version of Claude Code

What's Wrong?

Claude Code 1.0.120 release breaks the MCP server.

{
  "mcpServers": {
    "claude": {
      "command": "claude",
      "args": [
        "mcp",
        "serve"
      ]
    },
...

What Should Happen?

MCP server should provide the tools, as per documentation.

Error Messages/Logs

Steps to Reproduce

Install the latest binary:

$ npm -g install @anthropic-ai/claude-code
$ claude --version
1.0.120 (Claude Code)

Claude MCP Server
│ Status: ✔ connected
│ Command: claude
│ Args: mcp serve
│ Config location: /Users/username/github/claude/.mcp.json
│ Capabilities: none

$ npm -g uninstall @anthropic-ai/claude-code
$ npm -g install @anthropic-ai/claude-code@1.0.119

Claude MCP Server
│ Status: ✔ connected
│ Command: claude
│ Args: mcp serve
│ Config location: /Users/username/github/claude/.mcp.json
│ Capabilities: tools
│ Tools: 15 tools
│
│ ❯ 1. View tools
│   2. Reconnect

Claude Model

Sonnet (default)

Is this a regression?

Yes, this worked in a previous version

Last Working Version

1.0.119

Claude Code Version

1.0.120 (Claude Code)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_

View original on GitHub ↗

12 Comments

ChanceHu · 11 months ago

Same here.

Claude Code MCP Tool's "outputSchema" contains an "anyOf"

When using other tools：

{
"code": "invalid_literal",
"expected": "object",
"path": [
"tools",
5,
"outputSchema",
"type"
],
"message": "Invalid literal value, expected \"object\""
}

fmunteanu · 11 months ago

@bcherny this is still broken in new 2.0.0 release.

fmunteanu · 10 months ago

Edit: This was fixed on latest Claude Desktop, great job.

@jeremy-green @bcherny using Sonnet 4.5 in Claude Desktop with 1.0.119 release MCP server breaks Claude Desktop, I get a window error. Everything works fine with Sonnet 4.

Sonnet 4.5 result on session start with 1.0.119 release MCP server:

    "claude": {
      "command": "claude",
      "args": [
        "mcp",
        "serve"
      ]
    }

window.log:

2025-10-07 00:39:22 [warn] Error with Permissions-Policy header: Unrecognized feature: 'web-share'.
2025-10-07 00:39:23 [warn]   WARN  [Statsig] useFeatureGate hook failed to find a valid StatsigClient for gate 'requires_explicit_consent'.
2025-10-07 00:39:23 [warn]   WARN  [Statsig] useFeatureGate hook failed to find a valid StatsigClient for gate 'log_segment_events'.
2025-10-07 00:39:23 [warn]   WARN  [Statsig] useFeatureGate hook failed to find a valid StatsigClient for gate 'claude_ai_segment_enabled'.
2025-10-07 00:39:41 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:39:44 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:16 [error] Uncaught (in promise) Error: incomplete_stream
2025-10-07 00:40:49 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:40:52 [error] ResizeObserver loop completed with undelivered notifications.
2025-10-07 00:41:24 [error] Uncaught (in promise) Error: incomplete_stream

This is related to Project Instructions readout.

giannisanni · 10 months ago

still broken

jeremy-green · 10 months ago

When running the inspector: npx @modelcontextprotocol/inspector claude mcp serve, I receive the following error in the UI:

[
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": [
      "tools",
      0,
      "outputSchema",
      "type"
    ],
    "message": "Invalid literal value, expected \"object\""
  },
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": [
      "tools",
      5,
      "outputSchema",
      "type"
    ],
    "message": "Invalid literal value, expected \"object\""
  }
]

longfin · 10 months ago

it's still occurred in 2.0.24.

$ claude --version
2.0.24 (Claude Code)

$ npx -y @wong2/mcp-cli claude mcp serve
⠏ Connecting to server...file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/zod/v3/types.js:39
                const error = new ZodError(ctx.common.issues);
                              ^

ZodError: [
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": [
      "tools",
      0,
      "outputSchema",
      "type"
    ],
    "message": "Invalid literal value, expected \"object\""
  },
  {
    "code": "invalid_literal",
    "expected": "object",
    "path": [
      "tools",
      5,
      "outputSchema",
      "type"
    ],
    "message": "Invalid literal value, expected \"object\""
  }
]
    at get error (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/zod/v3/types.js:39:31)
    at ZodObject.parse (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/zod/v3/types.js:114:22)
    at file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:295:49
    at Client._onresponse (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:221:13)
    at _transport.onmessage (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/@modelcontextprotocol/sdk/dist/esm/shared/protocol.js:87:22)
    at StdioClientTransport.processReadBuffer (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/@modelcontextprotocol/sdk/dist/esm/client/stdio.js:145:79)
    at Socket.<anonymous> (file:///Users/seongwonmun/.npm/_npx/234164726e649089/node_modules/@modelcontextprotocol/sdk/dist/esm/client/stdio.js:103:22)
    at Socket.emit (node:events:507:28)
    at addChunk (node:internal/streams/readable:559:12)
    at readableAddChunkPushByteMode (node:internal/streams/readable:510:3) {
  issues: [
    {
      received: undefined,
      code: 'invalid_literal',
      expected: 'object',
      path: [ 'tools', 0, 'outputSchema', 'type' ],
      message: 'Invalid literal value, expected "object"'
    },
    {
      received: undefined,
      code: 'invalid_literal',
      expected: 'object',
      path: [ 'tools', 5, 'outputSchema', 'type' ],
      message: 'Invalid literal value, expected "object"'
    }
  ],
  addIssue: [Function (anonymous)],
  addIssues: [Function (anonymous)],
  errors: [
    {
      received: undefined,
      code: 'invalid_literal',
      expected: 'object',
      path: [ 'tools', 0, 'outputSchema', 'type' ],
      message: 'Invalid literal value, expected "object"'
    },
    {
      received: undefined,
      code: 'invalid_literal',
      expected: 'object',
      path: [ 'tools', 5, 'outputSchema', 'type' ],
      message: 'Invalid literal value, expected "object"'
    }
  ]
}

Node.js v24.4.1

it seems that 1.0.86 is fine.

$ npm install -g @anthropic-ai/claude-code@1.0.86
$ claude --version
1.0.86 (Claude Code)

$ npx -y @wong2/mcp-cli claude mcp serve
✔ Connected, server capabilities: tools
? Pick a primitive ›
❯   tool(Task)
    Launch a new agent to handle complex, multi-step tasks autonomously.

    Available agent types and the tools they have access to:
    - general-purpose: General-purpose agent for researching complex questions, searching for code, and executing multi-step tasks. When you are searching for a keyword or file and are not confident that you will find the right match in the first few tries use this
   agent to perform the search for you. (Tools: *)
    - statusline-setup: Use this agent to configure the user's Claude Code status line setting. (Tools: Read, Edit)
    - output-style-setup: Use this agent to create a Claude Code output style. (Tools: Read, Write, Edit, Glob, LS, Grep)

    When using the Task tool, you must specify a subagent_type parameter to select which agent type to use.

zhangz1w3nCode · 10 months ago

Is bug?

fmunteanu · 10 months ago

it seems that 1.0.86 is fine.

Last working version is 1.0.119, @longfin.

domdomegg · 9 months ago

Sorry for accidentally closing this issue! Linked up to some internal bug tracking by accident. I believe I've identified the root cause and made a fix, which should be available in the next version of Claude Code.

fmunteanu · 9 months ago

Thanks @domdomegg, any chance you can look into this Adam? I’m blocked on Claude Code upgrade because of this, for weeks. Can you ping any developer, this should be a trivial fix.