A production brain's first process boot after a live authority flip looked
hung and was restarted three times mid-recovery — three defects with one
scene. (1) THE FOLD MATERIALIZED THE LOG: peekFactsAbove(0) decoded every
fact into one array (GBs of after-images on a ~7k-fact log, a GC storm, a
starved write lane). The fold now STREAMS one segment-batch at a time —
memory is one segment at any log size — with structural ordering asserted
loudly. (2) THE FOLD WAS SILENT UNTIL DONE: minutes of boot work with zero
narration is what invited the restarts. It now announces itself BEFORE the
work ('do not restart, the fold is finite') and prints progress every
thousand facts. (3) THE CHAIN COULD ONLY ARM AT A CRASH: a live mid-session
flip left the fold checkpoint unfounded, so the brain's first unclean boot
paid a whole-log fold. Adoption now founds the checkpoint AT THE FLIP — one
paged full canonical barrier (bounded memory), then the stamp — so bounded
recovery holds from minute zero for every store that flips, at any size.
Pinned: a non-fresh flip stamps immediately; the first post-flip unclean
boot folds bounded (an unflushed at-ack fact above the checkpoint is
restored; a barrier-covered row below it is outside the fold). Kill matrix
and both adoption suites green alongside.
Two defects with one root, found by the fold-checkpoint work's first
integration gate. (1) THE RACE: restore() never quiesced the generation
store, so a background flush could write into _system/ while the swap was
removing it — observed as ENOTEMPTY mid-swap when a checkpoint stamp landed
between readdir and rmdir. The swap now runs inside the store's exclusive
section (runStateReplacement): flush timer disarmed, pending tier and
checkpoint accumulator discarded BEFORE any directory moves. (2) THE
INHERITED ASSERTION: a snapshot carries its source brain's clean-shutdown
marker and fold checkpoint, but the restored files were bulk-copied without
per-file fsync — the inherited stamps would suppress exactly the recovery
fold that cures a post-restore power cut. reopenAfterRestore now deletes
both stamps before reopening: the open treats the store as uncleanly shut,
folds the restored log into canonical, barrier-syncs what it re-applied,
and stamps fresh — the restored state is durably founded at restore time
instead of borrowing assertions about bytes this disk never synced.
Pinned: restore under in-flight traffic completes; the pre-restore stamp
does not survive; the post-restore stamp is the reopen fold's own, at the
restored watermark.
The fold checkpoint (_system/fold-checkpoint.json) is stamped strictly after
a canonical-sync barrier over every live entity touched since the last stamp
(syncEntityCanonical: ids → canonical paths → fsync; an absent file fsyncs
its parent directory so deletes are as durable as writes). An unclean open
under log authority now folds only (checkpoint, head]; the chain bootstraps
at an empty brain's adoption (three-phase hooks around adoptLogAuthority) or
at a brain's first whole-log fold — existing brains converge at their first
crash with zero regression. Rollback restores sync immediately; abort paths
feed the barrier; a failed barrier retains the old bound (bigger fold later,
never a lost write). Five structural pins including boundedness itself.
Also: the production-shaped write-flow gate leg (mixed traffic racing
flushes, crash mid-traffic, every ack survives — from a consumer-reported
gate miss), and two release-ceremony cures (tag-first push so the publish
never queues behind the release commit's CI run; raw-curl npmjs shasum
probe with propagation grace instead of a one-shot false divergence).
