An adopter's full suite found two v2 write-path defects on fresh brains,
reproduced with stacks; both cured and both pinned with their exact
production shapes:
1. PAD-FRAME CONSTRUCTIBILITY: a single msgpack bin filler steps its
header by one byte at each size class (bin8→bin16→bin32), leaving one
unreachable payload size per boundary — the sealer requested a
291-byte pad, the encoder threw 'not constructible', and sync() died
whole. Construction is now TOTAL: the class-boundary holes bridge with
a trailing fixint beside the bin ({bin(n)} ∪ {bin(n)+fixint} covers
every size ≥ minimum). Pinned exhaustively: every size from the
minimum through a full sector plus boundary spill constructs
byte-exact and decodes as reader-invisible filler.
2. THE NON-MONOTONIC REFUSAL LOOP: the append-failure compensation
rewound the generation counter on ANY throw — including a covering
SYNC failure after a SUCCESSFUL append. The log carried generation N
while the counter re-minted N, and every later append refused
'non-monotonic (N ≤ head N)' — the write path wedged in a refusal
loop through deferred-embed retries and flush backoff. The
compensation now splits by phase: an append failure (log never took
the fact) fully compensates — un-buffer and rewind; a sync failure
after append earns the rewind ONLY if the appended fact is provably
dropped, otherwise the generation stays consumed and buffered — the
counter never re-mints a number the log may carry. Pinned: an
injected one-shot sync failure fails its write loudly and the very
next write mints fresh and succeeds, with the log scanning strictly
ascending end to end.
Also probed against the adopter's carried report: the 9.0 vfs.rename
stale-ghost shape does NOT reproduce on this head (old path cleanly
unresolvable on exists/stat/readdir after rename).
Gates: unit 2067/2067 (160 files) · integration 833 (97 files) ·
conformance 36/36.
One deterministic v2 log (nine facts covering every fold-relevant behavior:
genesis, after-images with minted ints, a deferred embed pending→landed,
a sameAsGeneration vector ref, a verb, a tombstone, and an all-deduped
empty commit) whose ENCODED BYTES and FOLDED STATE are both pinned by
sha256 literals. The fixture (tests/fixtures/golden-log-v2.bin, 4128 B,
byte-verified against the encoder on every run) is the shared artifact a
second reader implementation consumes — it must reproduce the identical
fold digest; the pair is normative on disagreement. The fold law is
stated in prose beside the code: generation-ordered latest-per-id,
tombstone masking, embed.landed vector application, single-hop ref
resolution, key-sorted digest.
Also: decodeGroupV2 discriminated pad filler by RECORD COUNT, silently
swallowing legitimate empty commits (an all-deduped batch at a real
generation). Pads carry generation 0 — which writers can never mint — so
the generation is the honest discriminator; empty commits stay visible.
Pins: 4/4 (encode-exact, fixture-identical, fold-exact, human-readable
spot checks beside the hashes).
The cutover: new tail segments write format v2 (per-record [type, version,
cipherFlag, keyId] envelope; noun/verb after-images carry dense ints
MINTED AT APPEND from the id mapper — a rebuilt mapper reproduces
assignments exactly; log.genesis opens every new log with the id-space
width + a minted brain id; sync() seals to the header-declared sector
boundary with reader-invisible pad frames). Existing v1 segments are
never rewritten — per-segment decoder dispatch reads both formats and v2
facts map to the exact CommitFact shape all consumers already read.
Cutover on a live v1 log: an empty v1 tail re-heads in place; a non-empty
one is sealed by rotation, byte-identical. Records reserve the encryption
fields (cipherFlag 0 / keyId nil are the only legal values; anything else
refuses typed naming the needed newer reader) — crypto-ready with no
future bump on the compat surface. Empty-records facts are legal (an
all-deduped batch is a real generation — v1 semantics preserved; the
refusal there tore a column-store flush mid-commit in the full suite, the
consistency guard caught it loudly, and the root is fixed).
Golden byte vectors pinned for the second (native) reader implementation.
Pins: cutover 5/5 · codec 54 · kill-matrix stays 11/11.
The two-implementation contract surface as one pure module (no I/O):
segment header v2 (formatVersion 2 + sealSize in the reserved bytes),
per-record [type u8, version u8] envelope killing the unknown-kind
misclassification trap, the 12-type registry (after-images with minted
ints, tombstones, batch.meta, embed.pending/landed, blob.manifest,
projection.note, bootstrap.baseline, log.genesis with id-space width and
TYPED width-mismatch refusal), vectorLeg inline|{sameAsGeneration} with
writer-enforced single-hop, sector-sealed groups with pad frames, torn-tail
discipline, and GOLDEN BYTE VECTORS pinned so a second (native) reader
implementation can conform byte-for-byte. 50 format pins + a
fault-injecting storage wrapper (tear/drop-sync/fail-append) with 13
self-tests. v1 segments remain readable; nothing writes v2 yet — the
live-format cutover is its own commit.
