[Bug] MCP mode exits immediately on Windows (Cursor shows Connection closed -32000)

[RIchardRodo]

Summary

bb-browser CLI works in PowerShell for site commands, but MCP mode exits immediately, causing Cursor MCP to fail with Connection closed (-32000).

Environment

• OS: Windows 11 (10.0.26200)
• Node: tested with Node 24 and Node 20
• npm: 11.11.0
• bb-browser: 0.11.3 (also tested latest via npx)
• Client: Cursor (MCP v2)

What works

• bb-browser site update works
• bb-browser site list works
• bb-browser site google/search "AI agent" --json works (except expected site-level errors like 429/503)

What fails

MCP startup always closes immediately:

• Cursor status: Connection failed: MCP error -32000: Connection closed
• Cursor logs:
  • connection:connect_start -> connecting
  • Connection failed: MCP error -32000: Connection closed
  • CreateClient completed, connected: false

Reproduction

1. Configure Cursor MCP server for bb-browser.
2. Enable server in Cursor.
3. Observe immediate Connection closed.

Also reproduced in terminal:

bb-browser --mcp
# returns immediately to prompt (no persistent process)

[RIchardRodo]

Not available in LM studio
2026-04-28 14:05:19 [ERROR]
[Plugin(mcp/bb-browser)] stderr: _0x65c064 [McpError]: MCP error -32000: Connection closed
at _0x1b5ad6._onclose (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:254925)
at . [as onclose] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:253644)
at ChildProcess. (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:29:228490)
at ChildProcess.emit (node:events:508:20)
at _0xb15b01. [as emit] (C:\Program Files\LM Studio\resources\app.webpack\lib\mcpbridgeworker.js:1:295070)
at maybeClose (node:internal/child_process:1084:16)
at ChildProcess._handle.onexit (node:internal/child_process:304:5) {
code: -32000,
data: undefined
}