[BUG] Claude Code hangs indefinitely on SSE stream with multiple simultaneous sessions

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude Code frequently freezes and stops responding when running two simultaneous sessions. Token count stops incrementing and the session just sits stuck on "thinking" for 5+ minutes with no progress.

What Should Happen?

Environment

Platform: macOS
Terminal: Alacritty + tmux
Claude Code version: [run claude --version and fill in]

Setup

Session 1: Active coding session in a git worktree branch
Session 2: Planning session using Superpowers

Error Messages/Logs

Steps to Reproduce

Start a Claude Code session in a git worktree branch
Start a second Claude Code session for planning
Submit prompts to both sessions
One or both sessions hang — spinner keeps running but token count freezes and no progress is made

Expected behavior
Both sessions respond independently and consistently.
Actual Behavior
Sessions hang indefinitely showing something like:
(5m 9s · ↓ 8.0k tokens · thinking)
Token count stops increasing. No error, no timeout, no recovery.
Workaround
Pressing Enter with an empty prompt in the stuck pane nudges the SSE connection back to life without losing context. Hacky but effective.
Related Issues: #26957

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.50

Claude Code Version

2.1.50

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

(5m 9s · ↓ 8.0k tokens · thinking)

Workaround
Pressing Enter with an empty prompt in the stuck pane nudges the SSE connection back to life without losing context. Hacky but effective.
Related Issues: #26224, #13240, #13224