LSP tool hangs when calling typescript-language-server despite successful initialization

Description

The LSP tool hangs indefinitely when invoked against .tsx/.ts files, even though the typescript-language-server initializes correctly and responds with full capabilities.

Environment

• Claude Code version: latest (as of 2026-04-01)
• OS: macOS (Darwin 25.3.0)
• Node: v22.16.0
• typescript-language-server: 5.1.3
• TypeScript (workspace): 5.9.3

Configuration

Plugin

Using typescript-lsp@claude-plugins-official (enabled via /plugin, reloaded via /reload-plugins).

Reload output confirms LSP is registered:

Reloaded: 5 plugins · 1 skill · 6 agents · 0 hooks · 0 plugin MCP servers · 2 plugin LSP servers

Also tried .lsp.json (same result)

Placed at both ~/.claude/.lsp.json and <project>/.claude/.lsp.json:

{
  "typescript": {
    "command": "typescript-language-server",
    "args": ["--stdio"],
    "extensionToLanguage": {
      ".ts": "typescript",
      ".tsx": "typescriptreact",
      ".js": "javascript",
      ".jsx": "javascriptreact"
    },
    "workspaceFolder": "/path/to/project/frontend"
  }
}

Note: Before the plugin was enabled, .lsp.json in both locations returned No LSP server available for file type: .tsx rather than hanging, suggesting the .lsp.json discovery mechanism may also be broken (separate issue).

Steps to Reproduce

1. Install typescript-language-server globally (npm install -g typescript-language-server)
2. Enable typescript-lsp@claude-plugins-official via /plugin
3. Run /reload-plugins (confirms 2 plugin LSP servers)
4. Use the LSP tool on any .tsx file:

``
LSP operation=documentSymbol filePath=frontend/src/app/page.tsx line=1 character=1
``

1. Tool hangs indefinitely, returns [Tool result missing due to internal error]

Evidence: Server Works Correctly

Tested the same server manually via Python, sending an LSP initialize request:

proc = subprocess.Popen(
    ['typescript-language-server', '--stdio'],
    stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE,
    cwd='/path/to/project/frontend'
)

msg = json.dumps({
    'jsonrpc': '2.0', 'id': 1, 'method': 'initialize',
    'params': {'processId': None, 'rootUri': 'file:///path/to/project/frontend', 'capabilities': {}}
})
content = f'Content-Length: {len(msg)}\r\n\r\n{msg}'
proc.stdin.write(content.encode())
proc.stdin.flush()

Result: Server responds immediately with full capabilities (documentSymbol, hover, references, etc.). No hang, no errors.

Expected Behavior

LSP tool should return document symbols (or other requested data) from the running typescript-language-server.

Actual Behavior

LSP tool hangs until timeout, then returns [Tool result missing due to internal error].

Additional Notes

• The .lsp.json file placed in the project root (<project>/.lsp.json) was not discovered at all (returned "No LSP server available"). Only the plugin registration was detected, but it still hangs.
• .lsp.json placed at ~/.claude/.lsp.json and <project>/.claude/.lsp.json also returned "No LSP server available", suggesting .lsp.json file discovery only works via plugins.