Symbolized (HOIST_KEEP_NAMES=1): the trap is on the asyncify REWIND re-entering
the fiber — stack-local COROUTINE+body were destroyed when Call() returned
early on a park, so the rewind called through freed objects (latent UB in the
ORIGINAL fire-and-forget runOnFiber too). Heap-pinned FiberSlot + explicit
done flag + fiber-tail re-drain. Layer 2 (rewind interplay) still open —
fuzz stays fixme'd; pageerror stacks now captured in fuzz artifacts.
Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01G5cAM9M6q34n5X4dbrfVvi
22cd32b7b2