TUI Error when pressing Enter to call a tool

[collimarco]

Which version line?

v2 — current (@modelcontextprotocol/inspector@latest)

Which client?

TUI

Inspector version

2.1.0

Node version

v24.16.0

Operating system (and browser, for the web client)

macOS 15.7 / dev container (trixie) in VS Code

Transport

stdio

MCP server under inspection

import { createOpenAPIServer } from '@prefecthq/fastmcp-ts/server';
const spec = await fetch('https://pushpad.xyz/openapi.yaml').then((r) => r.text());
const server = createOpenAPIServer({
    spec,
    name: 'Pushpad',
    client: { headers: { authorization: `Bearer ${process.env.PUSHPAD_TOKEN}` } },
});
await server.run();

Steps to reproduce

1. Start the TUI: mcp-inspector --tui -- node --env-file-if-exists=.env .
2. Connect to MCP... tools are displayed correctly
3. Select a tool, like notifications_list
4. Press Enter to Test
5. Inspector TUI crashes with the following error

TUI Error: TypeError: Cannot read properties of null (reading 'useState')
    at useState (/workspaces/pushpad-mcp/node_modules/react/cjs/react.development.js:1622:21)
    at Form (file:///workspaces/pushpad-mcp/node_modules/ink-form/lib/Form.js:11:41)
    at Object.react_stack_bottom_frame (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:17596:20)
    at renderWithHooks (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:5335:22)
    at updateFunctionComponent (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:7720:19)
    at beginWork (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:9277:18)
    at runWithFiberInDEV (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:2505:30)
    at performUnitOfWork (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:15273:22)
    at workLoopSync (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:15099:41)
    at renderRootSync (/workspaces/pushpad-mcp/node_modules/@modelcontextprotocol/inspector/node_modules/react-reconciler/cjs/react-reconciler.development.js:15080:11)

Expected behavior

Inspector TUI should not crash

Actual behavior

Inspector TUI completely crashes with an error

Logs, errors, or screenshots

No response

Already prototyped a fix?

No response

Before you submit

• I searched existing issues and this is not a duplicate.
• This is not a security vulnerability report (those go through the private advisory process).

[fciaccia]

+1 , I can reproduce with any mcp server, even server-everything.