SessionStart hook stdout not displayed in terminal (regression from v2.1.15 to v2.1.37)

Bug Description

SessionStart hook output was visible in the user's terminal in v2.1.15 but is no longer displayed in v2.1.37. The hook still executes successfully and its output is injected into Claude's model context (visible as <system-reminder> tags), but the user sees nothing in the terminal.

Environment

• Claude Code version: v2.1.37 (worked in v2.1.15)
• OS: macOS (Darwin 23.1.0)
• Terminal: Ghostty

Hook Configuration

In .claude/settings.local.json:

{
  "hooks": {
    "SessionStart": [
      {
        "hooks": [
          {
            "type": "command",
            "command": "/path/to/my_hook.sh",
            "timeout": 5
          }
        ]
      }
    ]
  }
}

Hook Script (minimal reproduction)

#!/bin/bash
echo "=== Session Info ==="
echo "Database: ✅ Connected"
echo "API: 🔴 Down - CHECK NEEDED"
echo ""
echo "Action: Check API status"

Expected Behavior

The hook output should be displayed in the user's terminal at session start (as it was in v2.1.15).

Actual Behavior

• Terminal shows nothing from the hook
• Hook output IS injected into Claude's model context as SessionStart:... hook success: === Session Info ===...
• Claude can see and act on the hook output, but the user cannot

Steps to Reproduce

1. Configure a SessionStart hook that outputs text to stdout
2. Start a new Claude Code session or run /clear
3. Observe that no hook output is displayed in the terminal
4. Claude's first response will reference the hook output, confirming it executed

Related Issues

• #10373 (SessionStart hooks not working for new conversations)
• #9591 (SessionStart hook context not displayed)
• #12653 (SessionStart hook stderr not displaying)

Additional Context

This is a regression — the exact same hook configuration and script worked correctly in v2.1.15 where the output was visible in the terminal before the input prompt.