Parallel sessions crash simultaneously on Windows (native install)

Found 3 possible duplicate issues:

1. https://github.com/anthropics/claude-code/issues/3117
2. https://github.com/anthropics/claude-code/issues/13287
3. https://github.com/anthropics/claude-code/issues/15079

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Update: Workaround Found

After further investigation of the cli.js source (v2.1.50), we identified that the root cause is not the ~/.claude.json race condition, but rather the auto-migrate-to-native mechanism (qL1() function in cli.js).

What happens

Every time Claude Code starts, it checks whether it should migrate to the native Windows installation. When multiple sessions are running, this migration process kills and restarts the process — taking down all parallel sessions simultaneously.

The fix

Set the environment variable DISABLE_AUTO_MIGRATE_TO_NATIVE=1 to prevent the auto-migration check.

We added it to ~/.claude/settings.json:

{
  "env": {
    "DISABLE_AUTO_MIGRATE_TO_NATIVE": "1"
  }
}

Other findings

• autoUpdatesChannel in settings only accepts "latest" or "stable" — setting it to "disabled" causes a validation error (silent, but may contribute to instability)
• The native migration is a separate mechanism from auto-updates, controlled exclusively by the env var above

Result

After applying this fix, we've been running parallel sessions (multiple terminals, worktrees, subagents) without any crash. The sessions remain stable and independent as expected.

Confirmed Fix — Stable after 24h+

The workaround described in my previous comment has been confirmed working after multiple sessions over 24+ hours. Two environment variables provide full protection:

1. DISABLE_AUTO_MIGRATE_TO_NATIVE=1 — prevents the auto-migration check (qL1()) that was killing all parallel sessions
2. DISABLE_INSTALLATION_CHECKS=1 — suppresses the yellow "switched from npm to native" warning message (controlled by a separate mechanism, key npm-deprecation-warning in cli.js)

Both are set as permanent Windows user-scope environment variables (via [Environment]::SetEnvironmentVariable(..., 'User')) and as backup in ~/.claude/settings.json env section.

Summary

• Root cause: qL1() auto-migrate function runs at startup, reads process.env of the main process before settings.json env is applied (which only affects subprocesses via q16()). This race condition caused the migration process to kill all running sessions.
• Solution: Setting the env var at OS level (Windows registry, User scope) ensures it's available to any process from startup.
• Result: Parallel sessions (multiple terminals, worktrees, subagents) are fully stable.

I'd suggest documenting DISABLE_AUTO_MIGRATE_TO_NATIVE and DISABLE_INSTALLATION_CHECKS as official env vars for users who need to control this behavior, especially on Windows with parallel sessions.

Closing as resolved. Fix confirmed stable after 24h+ of parallel sessions. See last two comments for the full workaround (env vars DISABLE_AUTO_MIGRATE_TO_NATIVE + DISABLE_INSTALLATION_CHECKS at OS level).

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