Module store 

Session persistence layer

Provides pluggable session storage via the SessionStore trait.

Default Implementation

FileSessionStore stores each session as a JSON file:

• Session metadata (id, name, timestamps)
• Configuration (system prompt, policies)
• Conversation history (messages)
• Context usage statistics

Custom Backends

Implement SessionStore trait for custom backends (Redis, PostgreSQL, etc.):

use a3s_code::store::{
    SessionData, SessionSnapshotV1, SessionStore, SessionStoreCapabilities,
};

struct RedisStore { /* ... */ }

#[async_trait::async_trait]
impl SessionStore for RedisStore {
    // Required by AgentSession::save: commit the entire value in one
    // backend transaction / atomic replacement.
    async fn save_snapshot(&self, snapshot: &SessionSnapshotV1) -> Result<()> { /* ... */ }
    async fn load_snapshot(&self, id: &str) -> Result<Option<SessionSnapshotV1>> { /* ... */ }
    fn capabilities(&self) -> SessionStoreCapabilities {
        SessionStoreCapabilities { atomic_session_snapshots: true }
    }

    // Legacy fragment APIs remain available for migration compatibility.
    async fn save(&self, session: &SessionData) -> Result<()> { /* ... */ }
    async fn load(&self, id: &str) -> Result<Option<SessionData>> { /* ... */ }
    async fn delete(&self, id: &str) -> Result<()> { /* ... */ }
    async fn list(&self) -> Result<Vec<String>> { /* ... */ }
    async fn exists(&self, id: &str) -> Result<bool> { /* ... */ }
}

Structs

ContextUsage

Context usage statistics persisted with saved sessions.

FileSessionStore

File-based session store.

FileSessionStoreWal

Durable append-only JSONL WAL under a FileSessionStore root.

LlmConfigData

Serializable LLM configuration

MemorySessionStore

In-memory session store for testing

SessionConfig

Serializable session configuration.

SessionData

Serializable session data for persistence

SessionSnapshotV1

A complete, versioned persistence generation for one session.

SessionStoreAtRestCipher

AES-256-GCM cipher used by super::FileSessionStore when constructed with an encryption key.

SessionStoreCapabilities

Persistence guarantees advertised by a session store implementation.

SessionStoreCommitEventV1

Notification that one complete session generation was committed.

SessionStoreCommitWatch

Subscription to durable snapshot commit notifications.

SessionStoreWalEntryV1

One append-only WAL record for a FileSessionStore snapshot commit.

SessionStoreWriterLeaseV1

Durable writer lease published by a session store that advertises super::SessionStoreCapabilities::lease_fencing.

Enums

SessionState

Session state persisted with saved sessions.

SessionStoreWalPhaseV1

Lifecycle phase of one WAL record for a session snapshot commit.

Constants

DEFAULT_AUTO_COMPACT_THRESHOLD

Default auto-compact threshold (80% of context window).

SESSION_SNAPSHOT_SCHEMA_VERSION

Schema version written by SessionSnapshotV1.

SESSION_STORE_COMMIT_EVENT_SCHEMA_V1

SESSION_STORE_WAL_ENTRY_SCHEMA_V1

SESSION_STORE_WRITER_LEASE_SCHEMA_V1

Traits

SessionStore

Session storage trait

Functions

snapshot_content_digest

Digest a complete session snapshot for WAL identity fencing.