Function parse_cursor_jsonl

src/sessions/cursor.rs:285–373

Parse the newly-appended portion of one Cursor transcript file into a provider-neutral [`ParsedTranscript`]. Shared by the hook path ([`CursorEventSource`]) and the startup catch-up sweep ([`CursorSweepSource`]); both derive identical session/message ids for the same file (the hook event's `session_id` always equals the transcript file stem), so whichever runs second is an idempotent no-op.

(
    event: &Value,
    parent_session_id: &str,
    path: &Path,
    prev: StoredCursor,
    max_new_bytes: Option<u64>,
)

/// same file (the hook event's `session_id` always equals the transcript file
/// stem), so whichever runs second is an idempotent no-op.
fn parse_cursor_jsonl(
    event: &Value,
    parent_session_id: &str,
    path: &Path,
    prev: StoredCursor,
    max_new_bytes: Option<u64>,
) -> Option<ParsedTranscript> {
    let new = stream_new_jsonl(path, prev, max_new_bytes)?;
    let subagent = cursor_subagent_identity(path, parent_session_id);
    let session_id = subagent.as_ref().map_or_else(
        || parent_session_id.to_string(),
        |(session_id, _agent_id)| session_id.clone(),
    );
    let subagent_model = subagent.as_ref().and_then(|(_, agent_id)| {
        parent_dispatch_model_for_subagent(path, parent_session_id, agent_id)
    });
    let event_cwd = event_cwd(event);
    let event_location_provenance = event_location_provenance(event);
    let mut carry = TimestampCarry::new(i64::try_from(new.new_cursor.mtime).ok());
    let mut messages = Vec::new();
    for line in &new.lines {
        let derived_timestamp = carry.observe(&line.value);
        let context = CursorMessageContext {
            transcript_path: path,
            source_offset: line.offset,
            derived_timestamp,
            model_fallback: subagent_model.as_deref(),
            event_cwd: event_cwd.as_deref(),
            event_location_provenance,
        };
        // The byte offset doubles as the message ordinal and source_offset,
        // matching the original Cursor ingestion.
        if let Some(message) = event_message(&line.value, event, &session_id, line.offset, context)
        {
            messages.push(message);
        }
        messages.extend(event_dispatch_messages(
            &line.value,
            event,
            &session_id,
            context,
        ));
    }

    // Defer the (filesystem-walking) project/title/metadata derivation until
    // we actually have new messages; the driver ignores the draft otherwise.
    let draft = if messages.is_empty() {
        SessionDraft {
            session_id,
            project_key: String::new(),
            project_path: String::new(),
            title: None,
            metadata_json: None,
            parent_session_id: None,
            is_subagent: false,
            agent_id: None,
            parent_tool_use_id: None,
        }