SessionEnd hooks don't fire on API 500 errors

Problem

SessionEnd hooks configured in .claude/settings.json do not fire when a session terminates due to API 500 errors.

Expected behavior

SessionEnd hooks should fire on any session termination, including crashes, so users can implement auto-save/recovery mechanisms.

Actual behavior

When API Error 500 kills a session, the process terminates without triggering SessionEnd hooks. This defeats the purpose of having session-end automation for crash recovery.

Reproduction

1. Configure a SessionEnd hook in .claude/settings.json:

{
  "hooks": {
    "SessionEnd": [
      {
        "hooks": [
          {
            "type": "command",
            "command": ".claude/hooks/save-session.sh",
            "timeout": 15
          }
        ]
      }
    ]
  }
}

1. Trigger an API 500 error (e.g., by having PDFs in the project directory per #20018)

1. Observe that the hook script is never executed

Environment

• Claude Code v2.1.17
• macOS (Apple Silicon)
• Opus 4.5

Additional context

This may also be a configuration format issue—the nested hooks arrays might be incorrect. Documentation on the exact schema for .claude/settings.json hooks would help.

Related: #20018 (PDF reading causes API 500)