codex-thread-store is the storage boundary for Codex threads. It defines the ThreadStore trait plus local and in-memory implementations. Other storage implementations may live outside this repository.

Responsibilities

LiveThread is the preferred API for active session persistence. It owns a ThreadStore, serializes live operations, and sends canonical rollout items and explicit metadata updates in order.
ThreadMetadataHandler is private to this crate and owned by LiveThread. It synthesizes initial SessionMeta, filters and sanitizes rollout items, observes implicit metadata changes, and prepares ThreadMetadataUpdate values for LiveThread to send through ThreadStore::apply_thread_metadata.
ThreadStore::append_items is the raw canonical history append API. It does not infer metadata from item contents. Callers that need metadata correctness should use LiveThread.
ThreadStore::apply_thread_metadata is the explicit metadata API. Local storage writes these facts to SQLite; other stores can route them to a metadata endpoint independent of rollout item contents.
LocalThreadStore persists history through codex-rollout JSONL files and persists queryable metadata through the SQLite state database.
RolloutRecorder is the local JSONL writer. It writes already-canonical items and does not decide which rollout events should be persisted.
core/session creates or resumes LiveThread handles and should not need to know whether persistence is backed by local files or a remote store.
App-server code should use LiveThread for loaded threads.

Direction

New metadata semantics should live above ThreadStore. The store is allowed to persist explicit metadata fields, but it should not derive metadata by inspecting rollout item payloads.