[BUG] CLAUDE_ENV_FILE variables not available in Bash on resumed sessions (--continue/--resume)

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?

Environment variables written to CLAUDE_ENV_FILE during a SessionStart hook are available in Bash tool calls on fresh sessions, but not on resumed sessions (--continue, --resume, /resume).

The hook executes successfully in both cases — the env file is written with correct content — but the file is not re-sourced into the Bash environment on resume.

This was previously reported in #12418, which was auto-closed as a duplicate of #11649. However, #11649 is a different bug (plugins not receiving CLAUDE_ENV_FILE at all). The resume-session issue is a separate root cause and was not addressed by the fix for #11649.

What Should Happen?

Variables written to CLAUDE_ENV_FILE during SessionStart hooks should be available in all subsequent Bash tool calls, regardless of whether the session is fresh or resumed.

Error Messages/Logs

Fresh session:

$ echo $HOOK_TEST
hello_from_hook     ← ✓ works

Resumed session:

$ echo $HOOK_TEST
                    ← ✗ empty

The env file exists and has the correct content in both cases:

$ cat /Users/.../.claude/session-env/<session-id>/sessionstart-hook-0.sh
export HOOK_TEST=hello_from_hook

Steps to Reproduce

1. Add a SessionStart hook to .claude/settings.local.json:

``json
{
"hooks": {
"SessionStart": [
{
"matcher": "",
"hooks": [
{
"type": "command",
"command": "echo 'export HOOK_TEST=hello_from_hook' >> \"$CLAUDE_ENV_FILE\""
}
]
}
]
}
}
``

1. Start a fresh session: claude
2. Run echo $HOOK_TEST → outputs hello_from_hook ✓
3. Exit and resume: claude --continue
4. Run echo $HOOK_TEST → outputs empty string ✗

Claude Model

Opus

Is this a regression?

I don't know

Claude Code Version

2.1.119 (Claude Code)

Platform

AWS Bedrock

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

• The SessionStart hook runs on resume (confirmed by writing a debug log to /tmp).
• CLAUDE_PROJECT_DIR and CLAUDE_ENV_FILE are both available inside the hook during resume.
• The env file is written correctly — the issue is that it's not sourced into the Bash tool environment after resume.
• #12418 was auto-closed as duplicate of #11649, but they are different bugs: #11649 was about CLAUDE_ENV_FILE not being set for plugin-installed hooks; this is about the env file not being sourced on resumed sessions regardless of hook source.