The runner builds nothing, so serialising it only added its wait to the critical path; the worktree-isolated fallback is what must follow the lenses, and the harness case now records lens count at the FALLBACK's start alone. setTimeout in the harness is globalThis.setTimeout (the .mjs lint config has ES builtins only). head_sha carries the same description in both scripts and every fixer/implementer prompt asks for the worktree HEAD, not a PR head. The mechanics page says why the cap stays at one after the serialisation and restores the 20%/10% RAM thresholds by key; the record says "several", not "three". Decisions-Edit: yes Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_015QqCpYFsKgnAnx6jVwrKiV