[BUG] Claude Code Desktop: session closes silently, no response displayed

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?

Messages sent in Claude Code Desktop are received but get no response. The session defocuses within ~1 second after sendMessage. The UI shows the sent message but no reply ever appears.

CLI v2.1.83 and embedded binary 2.1.78 both work perfectly in terminal. claude.ai/code works perfectly in browser. Only the Desktop app fails.

Environment: macOS arm64, Claude Max plan, Claude Desktop freshly reinstalled.

What Should Happen?

Messages sent in Claude Code Desktop should receive a response, same as when using the CLI in terminal or claude.ai/code in browser.

Error Messages/Logs

# Before OAuth fix - Epoch mismatch loop:
[error] [transport:ccr] Epoch mismatch (409), invoking onEpochMismatch handler
[error] Session local_xxx query error: Claude Code process exited with code 1
[message] Unexpected token 'o', "ok\n" is not valid JSON

# After OAuth fix (/login resolved 401) - Silent session close:
17:43:52 [info] LocalSessions.sendMessage: sessionId=local_d5190cca, messageLength=2
17:43:53 [info] [CCD] LocalSessions.setFocusedSession: sessionId=null
17:44:00 [info] [CCD] LocalSessions.replaceEnabledMcpTools: toolCount=14
17:44:00 [info] [CCD] LocalSessions.replaceRemoteMcpServers: serverCount=2
17:44:01 [info] [CCD] LocalSessions.setFocusedSession: sessionId=null

# No error logged, session just silently closes.

Steps to Reproduce

1. Open Claude Desktop app on macOS arm64
2. Open a project folder (git repo)
3. Create a new Code task
4. Send any message (e.g. "hello")
5. Message appears in UI but no response is ever returned
6. Logs show setFocusedSession: null within ~1s of sendMessage

Troubleshooting already done:

• Full uninstall + reinstall of Desktop app
• Deleted ~/Library/Application Support/Claude
• Deleted ~/Library/Caches/com.anthropic.claude
• Deleted saved state and preferences
• Fixed expired OAuth token via /login
• Cleared git worktrees
• Reinstalled Node.js v24.14.1 and Claude Code CLI v2.1.83
• Confirmed CLI and claude.ai/code both work fine

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.83 (CLI) / 2.1.78 (Desktop embedded)

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_