SessionHeader, SessionMessageEntry, NewSessionOptions), transcript recording, branch summaries, compaction entries. Key constants: SESSION_STREAMING_LOAD_THRESHOLD_BYTES (128 MB), SESSION_ASYNC_PARSE_YIELD_BYTES (4 MB). Session version CURRENT_SESSION_VERSION = 3. Reads/session search uses SESSION_LIST_SEARCH_TEXT_MAX_CHARS (64 KB) and SESSION_LIST_PARSE_MAX_LINE_CHARS (1 MB).
Related: Coding agent index, Compaction