Atomic engram_save + anti-clobber floor (validated, darwin build recipe) #57

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tim.lingo wants to merge 1 commits from fix/engram-save-atomic-darwin into chore/live-darwin-runtime

Author	SHA1	Message	Date
Tim Lingo	89e45ed689	fix(engram): atomic engram_save (tmp+fsync+rename) + sparse-write anti-clobber floor Kills the engram-clobber loop at its source. engram_save did a bare fopen("wb") that truncates snapshot.json to 0 bytes before the 47MB write — a booting soul's engram_load could read that empty window -> genesis -> nodes=1 -> a 63-node save overwrote the populated file. Two guards: 1. Atomic write: serialize to <path>.tmp, fflush+fsync, rename() over target (atomic on POSIX) — no reader ever sees a truncated/0-byte snapshot. 2. Sparse-write floor: refuse to overwrite a >200KB snapshot with one < 1/16 its size — a partial load can never clobber a healthy graph, whatever the cause. Validated in isolation: standalone clang harness 11/11; rebuilt the darwin soul (scripts/build-soul-darwin.sh) and booted it on an isolated port against a golden copy — loaded 5113 nodes and round-tripped the full 47MB snapshot, no .tmp leftover, live ~/.neuron untouched. Adds scripts/build-soul-darwin.sh (local elb replacement). Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>	2026-06-16 18:23:08 -05:00

Author

SHA1

Message

Date

Tim Lingo

89e45ed689

fix(engram): atomic engram_save (tmp+fsync+rename) + sparse-write anti-clobber floor

Kills the engram-clobber loop at its source. engram_save did a bare fopen("wb")
that truncates snapshot.json to 0 bytes before the 47MB write — a booting soul's
engram_load could read that empty window -> genesis -> nodes=1 -> a 63-node save
overwrote the populated file. Two guards:
 1. Atomic write: serialize to <path>.tmp, fflush+fsync, rename() over target
    (atomic on POSIX) — no reader ever sees a truncated/0-byte snapshot.
 2. Sparse-write floor: refuse to overwrite a >200KB snapshot with one < 1/16 its
    size — a partial load can never clobber a healthy graph, whatever the cause.

Validated in isolation: standalone clang harness 11/11; rebuilt the darwin soul
(scripts/build-soul-darwin.sh) and booted it on an isolated port against a golden
copy — loaded 5113 nodes and round-tripped the full 47MB snapshot, no .tmp leftover,
live ~/.neuron untouched. Adds scripts/build-soul-darwin.sh (local elb replacement).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

2026-06-16 18:23:08 -05:00

Atomic engram_save + anti-clobber floor (validated, darwin build recipe) #57

1 Commits