# Changelog
All notable changes to this project will be documented in this file.
The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/),
and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
## [Unreleased]
## [0.22.4] — 2026-03-22
### Added
- `AuditChain::append_with_agent()` — append an entry with agent ID in one call (previously required manual entry construction and `pub(crate)` access)
## [0.22.3] — 2026-03-22
### Added
- `FileStore` — append-only JSON Lines file backend (`file_store` module)
- `SqliteStore` — queryable SQLite backend with indexed columns, behind `sqlite` feature flag
- Chain rotation: `AuditChain::rotate()` returns `ChainArchive`, new entries link to previous head
- `AuditChain::from_entries()` to restore a chain from archived entries
- `SqliteStore::query_by_source()`, `query_by_severity()`, `query_by_agent()` for indexed queries
- `query` module with `QueryFilter` — composable multi-field filtering (source, severity, agent, action, time range)
- `AuditChain::by_agent()` and `AuditChain::query()` methods
- `SqliteStore::query()` — translates `QueryFilter` to indexed SQL WHERE clauses
- `FileStore::query()` — load + filter in memory
- `export` module: `to_jsonl()` and `to_csv()` writing to any `io::Write` target
- `retention` module: `RetentionPolicy` enum (KeepCount, KeepDuration, KeepAfter)
- `AuditChain::apply_retention()` — archive entries outside the retention window
- `EventSeverity::as_str()` — stable string representation for hashing and storage
- `AuditEntry` accessor methods: `id()`, `timestamp()`, `severity()`, `source()`, `action()`, `details()`, `agent_id()`, `prev_hash()`, `hash()`
- Advisory file locking (`flock`) on `FileStore` append and load for concurrent-process safety
- `fs2` dependency for cross-platform file locking
- `review` module: `ChainReview` with integrity status, time range, source/severity/agent distributions
- `AuditChain::review()` — produce a structured chain summary with `Display` for human-readable output
- `Display` impl for `AuditEntry` and `EventSeverity`
- `tracing` instrumentation: append, verify, rotate, retention, store open, parse errors
- `merkle` module: `MerkleTree` with `build()`, `root()`, `proof()`, and `verify_proof()` for O(log N) inclusion proofs
- `signing` module (feature: `signing`): Ed25519 per-entry signatures with `SigningKey`, `VerifyingKey`, `EntrySignature`
- `EventSeverity` now implements `Ord`/`PartialOrd`/`Hash` — variants ordered Debug < Info < Warning < Error < Critical < Security
- `EventSeverity::at_or_above()` — returns all severity levels at or above a given level
- `QueryFilter::min_severity()` — filter to entries with severity >= a given level (SQL `IN(...)` for SqliteStore)
- `AuditChain::append_batch()` — append multiple entries in one call
- `AuditChain::page(offset, limit)` — paginated access to chain entries
- `AuditStore::load_page(offset, limit)` — paginated loading with SQL LIMIT/OFFSET override for SqliteStore
- `AuditStore::load_and_verify()` — convenience that loads and verifies in one call
- `AuditStore::query()` — trait-level query with default load+filter impl; `SqliteStore` overrides with SQL WHERE
- `streaming` module (feature: `streaming`): `AuditStream` for real-time pub/sub via majra with MQTT-style topic wildcards
- 84 tests, 94% line coverage
### Changed
- **Breaking:** `compute_hash` now length-prefixes each variable-length field (little-endian u64) to prevent second-preimage collisions via field boundary shifting. Hashes from previous versions are incompatible.
- **Breaking:** `AuditEntry` fields are now private — use accessor methods instead. Construction still via `AuditEntry::new()` and `.with_agent()`. This prevents accidental mutation that bypasses hash integrity.
- **Breaking:** `compute_hash` now uses `EventSeverity::as_str()` (stable) instead of `Debug` format, and canonical sorted-key JSON for details. Hashes from previous versions are incompatible.
- `AuditChain::verify()` now delegates to `verify_chain()` after genesis check, eliminating duplicated logic
- `AuditChain::apply_retention()` moved from orphan impl in `retention.rs` to `chain.rs`
- CSV export now escapes `agent_id` field (user-provided, may contain commas)
- `AuditEntry::Display` no longer panics on short/empty hash strings
- `FileStore::open` uses atomic `OpenOptions::create(true)` instead of TOCTOU `exists()`+`create()`
- `verify_chain` computes hash once per entry instead of twice on failure
- `rotate()` on empty chain no longer sets `prev_chain_hash` to `Some("")`
- `query()` moved to `AuditStore` trait (polymorphic access via `dyn AuditStore`)
- `AuditStore::load_all` docs now warn that it does not verify integrity
- `RetentionPolicy::apply_retention` avoids double clone via `Vec::split_off`
- Key types re-exported from crate root: `QueryFilter`, `RetentionPolicy`, `to_jsonl`, `to_csv`
### Removed
- `LibroError::EmptyChain` variant (was dead code, never constructed)
- `SqliteStore::query_by_source`, `query_by_severity`, `query_by_agent` — superseded by `SqliteStore::query(&QueryFilter)`
- `tracing` dependency (was listed but never used)
## [0.21.3] — 2026-03-21
### Fixed
- Corrected `EmptyChain` error variant — previously unreachable, now reserved for store-level semantics
### Changed
- Tightened `thiserror` dependency to major version 2
## [0.21.2] — 2026-03-20
### Added
- Criterion benchmarks for `append` and `verify` operations (`benches/chain.rs`)
### Changed
- Improved CI pipeline: added MSRV check (1.89), `cargo-deny` supply-chain audit, codecov integration
## [0.21.1] — 2026-03-19
### Added
- `verify` module — standalone `verify_chain()` function for external audit tools
- Integration tests for full chain lifecycle, tamper detection, and error display
### Fixed
- Genesis entry validation now checks `prev_hash` is empty
## [0.21.0] — 2026-03-18
### Added
- `AuditStore` trait for pluggable persistence backends
- `MemoryStore` — in-memory backend (for testing and ephemeral use)
- `store` module with unit tests
### Changed
- `LibroError` extended with `Store`, `Io`, and `Json` variants for persistence error handling
## [0.20.0] — 2026-03-17
### Added
- `AuditChain` — append-only chain with hash linking, verification, and query methods
- `by_source()` and `by_severity()` query methods on `AuditChain`
- `head_hash()` to retrieve the chain head
- Chain-level tamper detection tests
## [0.19.0] — 2026-03-16
### Added
- `AuditEntry::with_agent()` builder method for optional agent ID tracking
- Serde `Serialize`/`Deserialize` on `AuditEntry` and `EventSeverity`
- Serde roundtrip test
## [0.18.0] — 2026-03-15
### Added
- `AuditEntry` — core audit entry with UUID, timestamp, severity, source, action, JSON details
- `EventSeverity` enum: Debug, Info, Warning, Error, Critical, Security
- SHA-256 hash computation and self-verification (`compute_hash`, `verify`)
- Hash-linked chaining via `prev_hash` field
- `LibroError` with `IntegrityViolation` variant
- Entry creation, tamper detection, and chaining tests
## [0.1.0] — 2026-03-14
### Added
- Initial project scaffolding extracted from daimon agent-runtime audit module
- Cargo workspace setup (edition 2024, MSRV 1.89, AGPL-3.0)
- CI pipeline (`ci.yml`) with fmt, clippy, test, and audit steps
- Release workflow (`release.yml`) with multi-platform builds and crates.io publish
- `Makefile` with standard development targets
- `VERSION` file and `scripts/version-bump.sh`
- README with architecture overview, roadmap, and reference code pointers
[Unreleased]: https://github.com/MacCracken/libro/compare/v0.22.3...HEAD
[0.22.3]: https://github.com/MacCracken/libro/compare/v0.21.3...v0.22.3
[0.21.3]: https://github.com/MacCracken/libro/compare/v0.21.2...v0.21.3
[0.21.2]: https://github.com/MacCracken/libro/compare/v0.21.1...v0.21.2
[0.21.1]: https://github.com/MacCracken/libro/compare/v0.21.0...v0.21.1
[0.21.0]: https://github.com/MacCracken/libro/compare/v0.20.0...v0.21.0
[0.20.0]: https://github.com/MacCracken/libro/compare/v0.19.0...v0.20.0
[0.19.0]: https://github.com/MacCracken/libro/compare/v0.18.0...v0.19.0
[0.18.0]: https://github.com/MacCracken/libro/compare/v0.1.0...v0.18.0
[0.1.0]: https://github.com/MacCracken/libro/releases/tag/v0.1.0