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

ThreadStore::append_items is the raw canonical history append API. It does not infer metadata from item contents.
ThreadStore::update_thread_metadata is the only thread metadata write API. It accepts a single literal metadata patch shape, regardless of whether the caller is applying a user/API mutation or facts derived above the store from appended history.
LiveThread is the preferred API for active session persistence. It owns a per-thread metadata sync helper, applies the rollout persistence policy, appends canonical history, and then sends metadata patches through ThreadStore::update_thread_metadata.
ThreadManager routes metadata mutations for loaded and cold threads through one entrypoint. Loaded threads use their LiveThread; cold threads go directly to the store.
LocalThreadStore persists history through codex-rollout JSONL files and persists queryable metadata through the SQLite state database when available. Local explicit metadata mutations also maintain JSONL/name-index compatibility so reading old or SQLite-less local storage keeps working.
RolloutRecorder is the local JSONL writer. It writes already-canonical items for ThreadStore::append_items; it no longer decides metadata updates for live thread-store appends.
core/session creates or resumes LiveThread handles and does not need to know whether persistence is backed by local files or another store.

Direction

New metadata observation semantics should live above ThreadStore. Stores persist explicit metadata fields, but raw history appends remain history-only.