[BUG] CLI v2.1.55 fails to connect to VS Code extension WebSocket server (regression from v2.1.53)

Summary

After upgrading CLI from v2.1.53 to v2.1.55 in a VS Code Remote SSH environment, IDE integration completely stops working. Downgrading back to v2.1.53 immediately restores functionality, confirming this is a regression introduced in v2.1.55.

Environment

| Item | Details |
|------|---------|
| OS | Linux Ubuntu (x86_64) |
| VS Code | 1.109.5 (Remote SSH / vscode-server) |
| Claude Code CLI | v2.1.55 (broken) / v2.1.53 (working) |
| VS Code Extension | anthropic.claude-code v2.1.55 |
| Connection Mode | Remote SSH via vscode-server |

Steps to Reproduce

1. Use VS Code with Remote SSH connected to a Linux machine (vscode-server)
2. Install Claude Code CLI v2.1.55 on the remote machine
3. Install the matching VS Code extension v2.1.55
4. Open an integrated terminal in VS Code and launch claude
5. IDE integration does not work

Diagnostic Findings

Detailed investigation was performed. Key findings are as follows:

Environment variables at runtime (CLI v2.1.55)

VSCODE_IPC_HOOK=              ← empty (expected behavior in Remote SSH)
VSCODE_IPC_HOOK_CLI=/run/user/1000/vscode-ipc-xxxx.sock  ← present
CLAUDE_CODE_SSE_PORT=39280
TERM_PROGRAM=vscode
CLAUDECODE=1

VS Code extension side — healthy

• WebSocket server running and listening on 127.0.0.1:39280 (confirmed via ss -tlnp)
• Lock file ~/.claude/ide/39280.lock exists with valid content:

``json
{
"pid": 139046,
"workspaceFolders": ["/path/to/workspace"],
"ideName": "Visual Studio Code",
"transport": "ws",
"runningInWindows": false,
"authToken": "..."
}
``

• TCP connectivity test: Python socket.connect(('127.0.0.1', 39280)) succeeded

CLI v2.1.55 side — broken

• Inspected all network connections of the Claude Code process via ss -tnp | grep <claude_pid>
• The CLI process has zero outbound connections — it never attempts to connect to the VS Code extension's WebSocket server

The extension side is fully functional. The CLI simply does not connect.

Workaround

Downgrade CLI to v2.1.53:

# If you used the native installer, versions are stored locally
ln -sf ~/.local/share/claude/versions/2.1.53 ~/.local/bin/claude

# Verify
claude --version  # should show 2.1.53

After reopening a terminal and launching claude, IDE integration is restored immediately.

Verification

After downgrading to v2.1.53, ss -tnp confirms the Claude Code process establishes a WebSocket connection to port 39280, and all IDE integration features work correctly.