Levi Neuwirth
1a7df12b0c
The corpus fixture stamped the manifest at {0,10} because SetTuningContext
needs an operation block at {3,10}. Those are separate domains: the document
line carries the manifest's aggregate SchemaVersion and projection discards the
block's schema by design. With no edit barriers the manifest stays baseline V0,
so the fixture was locking an over-stamped manifest into the corpus while
appearing to prove the operation epoch - the exact inference text_projection.tex
tells readers not to make. The block's stamp is proven where it lives, by the
staged-and-reopened roundtrip test.
t10 still read only bundle.rs. Correcting ids.rs and adding a prose
cross-reference did not make the pair travel together; sharing one guard does.
It now iterates both sources. Two incidental discoveries while extending it:
include_str! pulls in the test's own text, so both the needle and the assertion
message must avoid the phrase they search for - which is why the original split
its needles with concat().
Four stale comments: manifest.rs's barrier-tag range 24-33, payload.rs's "ten
events"/"thirty-four payloads", and the 30..=33 ranges in generators.rs and
layout_stub.rs.
Mutation sweep, each run and observed:
- t1 kind space 34->35, and tag space 34->35, separately. Both kill t1.
- t2/t3 schema_major 3->0: kills t3 and the staged/reopened test ({0,10} vs
{3,10}).
- t6 predecessor restore dropped: kills t6 (442 vs 441).
- t8 kind epoch 10->9 and tag epoch 10->9, separately. Both kill t8; the tag
mutation additionally kills s1's tag table, the kind mutation does not,
which is why both tables needed the entry.
- t10 stale claim reinjected into bundle.rs and into ids.rs, separately. Each
kills the guard, naming the offending file.
t5 and t7 were signed earlier; t4 by the cap-to-2 run.
Gate: 1410 tests, clippy 0, fmt clean, git diff --check clean, 14 textproj
vectors, 105 decode vectors.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QjsEnYhm1gPpf6ii2iFxFV
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| .. | ||
| examples | ||
| src | ||
| tests | ||
| Cargo.toml | ||
| DECISIONS.md | ||
| README.md | ||
README.md
epiphany-bundle
The Epiphany .musc file format, implementing the normative requirements of
Chapter 8 (File Format) of the core specification (spec/core_spec.pdf).
This is Agent D's crate per spec/QUICKSTART.md. It depends on
epiphany-determinism (Agent A) and on nothing else — not on epiphany-core
(Agent B) or epiphany-ops (Agent C):
bundles handle bytes, ops handles semantics. A canonical-base snapshot from the bundle's perspective is opaque bytes plus a frontier DVV; only
epiphany-opsinterprets it. — QUICKSTART
A bundle is a single file: a fixed 64-byte header at offset 0, two 256-byte superblock slots, then a body of immutable, content-addressed chunks. The superblocks are the only mutable on-disk objects. A commit appends new chunks, writes a new manifest chunk, then flips the active superblock by writing the inactive slot and durably flushing it — that flush is the commit point. Because commits only ever append and touch the inactive slot, a crash can never corrupt the active state.
What's here
| Area | Items | Spec |
|---|---|---|
| Prelude | FixedHeader (64 B, CRC-32C), Superblock/CommitState (256 B, CRC-32C), select_active |
Ch. 8 §"The Bundle Layout", §"Superblock Selection" |
| Atomic commit | Bundle::create/open/commit, the 7-step protocol, cold-open path |
Ch. 8 §"The Atomic Write Protocol", §"Streaming Reads" |
| Content addressing | chunk_content_hash/chunk_id, ChunkRef, ChunkKind, CompressionAlgorithm, domain separation |
Ch. 8 §"Content Hashing", §"Chunks" |
| Manifest | Manifest (canonical_base ≠ acceleration_snapshots), SnapshotRef, BlobRef, ProfileDeclaration, ExtensionDeclaration |
Ch. 8 §"The Manifest" |
| Retention | RetentionPolicy (first-class), ProfileConstraints |
Ch. 8 §"Garbage Collection and Retention" |
| Op blocks | pack_operation_blocks (1 MiB soft target), encode_block/decode_block |
Ch. 8 §"Operation Envelope Blocks" |
| Storage | BlockStore, MemStore, FileStore (real fsync), FaultStore (crash sim) |
Ch. 8 §"Durable Writes" |
| Gates | fuzz::run_crash_recovery_fuzz, fuzz::exhaustive_crash_check, fuzz::run_manifest_selection_harness |
QUICKSTART acceptance |
The crash-recovery contract (the acceptance gate)
Kill the process between any two syscalls in the commit protocol; reopen; the bundle must be valid in 100% of runs, and must recover to the previous generation when the crash precedes the durable flush. This is the most important single test in the entire prototype. — QUICKSTART, Agent D
Killing a real process between syscalls cannot be made deterministic, so the
fuzzer drives the commit against a FaultStore that distinguishes live
(page-cache) bytes from durable (survives-a-crash) bytes and can crash after
any chosen syscall — optionally tearing the in-flight superblock write, the
case the slot CRC must catch. After every simulated crash the bundle is reopened
from the durable image and must:
- open successfully (never corrupt);
- be at the previous generation or the new one, never anything else;
- if the commit returned
Ok, be at the new generation; and if the crash was clean (the in-flight flush persisted nothing) and the commit did not complete, be at the previous generation — the exact "recover to the previous generation when the crash precedes the durable flush" property. (A torn final flush may at a full prefix legitimately persist the whole superblock — the genuine post-commit case — so the torn branch admits either generation.) - report no integrity anomaly;
- have every canonical chunk present and hash-intact.
Two drivers exercise this: a randomized 10,000-iteration sweep, and an exhaustive per-commit sweep that tests every syscall boundary crossed with every tear point (clean, and torn at prefixes around the 252-byte CRC offset and the 256-byte slot size). The second leaves no step of the protocol untested.
The companion manifest_selection gate asserts the Chapter 8 superblock-
selection rule across every corruption scenario the QUICKSTART enumerates: slot A
corrupt + B valid (and vice versa), both valid at generation+1, both valid at the
same generation (equivalent, and divergent), a generation gap > 1, a
non-committed slot, a manifest-hash mismatch, and neither valid.
Building and testing
cargo test -p epiphany-bundle # unit + the two gates
cargo clippy -p epiphany-bundle --all-targets -- -D warnings
cargo run --release --example fuzz_crash -- 1000000 # extended crash soak
Hand-off criteria (QUICKSTART, Agent D)
cargo testclean.- Crash-recovery fuzzer passes 10,000 iterations
(
crash_recovery_fuzz_ten_thousand_iterations, two seeds; extended soak via the example binary; exhaustive per-syscall sweep inexhaustive_sweep_across_base_states_and_commit_shapes). - Manifest-selection harness handles every corruption scenario
(
every_selection_scenario_holds). - Real-filesystem
fsyncround-trip (file_store_real_fsync_round_trip).
Scope boundaries (per QUICKSTART "Don't do these")
v0 writes only uncompressed chunks (compression on the write path is deferred),
but reading zstd-compressed chunks and blobs is supported, per the spec's
§Compression MUST (the manifest is mandatory-uncompressed regardless, and a
compressed manifest is rejected). It carries the text-projection root but does
not implement the s-expression projection content, and it preserves extension
declarations and chunks but does not evaluate edit barriers — barrier operands
(OperationKindTag, ObjectKind, EditBarrier) are owned by Agents C and E.
Operation envelopes, snapshots, and causal frontiers are opaque bytes here.
See DECISIONS.md for the prototype byte-layout choices that anticipate the
deferred Binary Format companion, and the batched Pass 11 candidates.