Crate harn_session_store 

Durable Harn session-store primitive.

One source of truth for persisted agent/session events (Message, ToolCall, ToolResult, Plan, Compaction, SystemReminder, Hypothesis, Receipt, Reminder, PermissionDecision, plus arbitrary Custom shapes), snapshots, replay, fork/truncate, signed receipts (Ed25519 over canonical JSON), and retention. Server and host adapters can layer transport, auth, and product policy on top without reimplementing transcript storage semantics.

Layout

• event - event taxonomy and canonical JSON encoder
• signing - Ed25519 chain hashes and receipt signatures
• store - public SessionStore trait and shared types
• memory - in-memory backend for tests and headless dev
• sqlite - persistent SQLite backend for local/self-hosted use
• retention - declarative per-tenant retention policy

Re-exports

pub use event::canonical_event_bytes;

pub use event::canonical_json_bytes;

pub use event::AppendEvent;

pub use event::EventId;

pub use event::EventSignature;

pub use event::SessionEventKind;

pub use event::StoredEvent;

pub use memory::MemorySessionStore;

pub use retention::ArchiveSink;

pub use retention::RetentionPolicy;

pub use retention::SharedArchiveSink;

pub use retention::Tombstone;

pub use signing::chain_root_fold;

pub use signing::chain_root_hash;

pub use signing::chain_root_init;

pub use signing::compute_record_hash;

pub use signing::re_anchor_events;

pub use signing::verify_event;

pub use signing::verify_event_chain;

pub use signing::verify_receipt_root;

pub use signing::SessionSigner;

pub use signing::VerifyError;

pub use signing::ALGORITHM as SIGNATURE_ALGORITHM;

pub use sqlite::SqliteSessionStore;

pub use store::CreateSession;

pub use store::EventPage;

pub use store::ForkResult;

pub use store::ListFilter;

pub use store::ReadRange;

pub use store::SessionId;

pub use store::SessionMeta;

pub use store::SessionStatus;

pub use store::SessionStore;

pub use store::SharedSessionStore;

pub use store::Snapshot;

pub use store::SnapshotId;

pub use store::StoreError;

pub use store::StoreHooks;

pub use store::StoreResult;

pub use store::SweepReport;

pub use store::TruncateResult;

pub use store::VerifyFailure;

pub use store::VerifyReport;

pub use store::MAX_READ_BATCH;

Modules

event

Session event taxonomy and canonical serialization.

memory

In-memory backend. Single-process, no persistence — but matches the public SessionStore contract exactly so the rest of the primitive can be exercised end-to-end in tests without touching disk.

retention

Per-tenant retention policy: lifecycle windows + archive sink hooks.

signing

Ed25519 signing for session event chains.

sqlite

SQLite-backed SessionStore.

store

SessionStore trait + the shared types every backend speaks.