Phase-3-light. #3790 (@ai-ag2026): expand cold-load transcript window to ~msg_limit renderable rows so tool-heavy sessions don't open showing 1-2 messages. Codex CORE fix: explicit expand_renderable flag (cold-load only; Load-earlier keeps raw cap). Also fixed a recurring CI timing flake (git-parallel test → deterministic Barrier). Full suite 8228, Codex SAFE, Opus SHIP, CI 11/11. Co-authored-by: ai-ag2026 <ai-ag2026@users.noreply.github.com>