A fork subagent's transcript opens with a copy of the parent turn that spawned it, its own Agent call included; folding that call re-entered the same fork until RecursionError, failing every daily sync since 2026-09-24. Skip a spawn call while its own subagent is being expanded, and strip the <fork-boilerplate> preamble. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01LbnmGHnFqDjyhPcCg1SEfF