claude --worktree hangs indefinitely on Linux (stuck on API call before init)

Description

claude --worktree hangs indefinitely with a completely blank terminal on Linux. Regular claude in the same directory starts within seconds.

Environment

• Claude Code version: 2.1.71
• OS: Ubuntu Linux (kernel 6.17.0-14-generic)
• Shell: zsh
• Platform: x86_64

Steps to Reproduce

1. cd into any git repository
2. Run claude --worktree
3. Terminal stays completely blank -- no TUI renders, no spinner, no output
4. Process must be killed manually

Regular claude (without --worktree) in the same directory starts fine.

Diagnostic Findings

Process state while hanging

Inspected the hanging process via /proc and ss:

• State: S (sleeping), all threads sleeping
• wchan: ep_poll (blocked in Node.js event loop waiting for I/O)
• No child processes: MCP servers, hooks, worktree session -- none spawned yet. Hang is very early in initialization.
• Only ~17 file descriptors: far fewer than a fully initialized session
• Single network socket: ESTAB 0 0 <local>:46118 <anthropic-api>:443
• TCP connection to api.anthropic.com:443 is ESTABLISHED
• Send queue = 0, receive queue = 0 (no data flowing in either direction)
• Process is waiting for an HTTP response that never arrives

What was ruled out

All local factors were systematically tested and eliminated:

| Hypothesis | Result |
|---|---|
| Git hooks slow | post-checkout hook completes in 0.02s |
| Git worktree creation slow | git worktree add completes in 0.06s |
| MCP stdio servers hanging | Not spawned yet -- hang is before MCP init |
| MCP HTTP servers unreachable | All local MCP servers respond normally |
| SessionStart hooks hanging | All hooks have 5s timeouts, server is running |
| Process stopped by SIGTTOU | Only happens under timeout wrapper; direct run shows S (sleeping) with correct foreground process group (TPGID = PGID) |

strace confirmation

Running under strace -f shows the process:

1. Loads shared libraries (libc, libpthread, etc.)
2. Initializes V8 runtime, creates worker threads (clone3)
3. Opens project directory
4. Stops -- all threads enter futex waits, no further syscalls

No fork/exec/clone for child processes (git, MCP servers, etc.) ever occurs.

Expected Behavior

claude --worktree should create a git worktree and start an interactive session in it, similar to how regular claude starts.

Actual Behavior

Process hangs indefinitely with a blank terminal, stuck waiting for an HTTPS response from api.anthropic.com that never arrives. The hang occurs before any local initialization (worktree creation, MCP servers, hooks, TUI rendering).

Workaround

Manually create the worktree and run claude in it:

git worktree add /tmp/my-feature -b feature/my-work
cd /tmp/my-feature
claude