Two good questions.

Concurrent sessions: works today. Every backscroll run (or exec) is its own session — concurrent writers share one SQLite DB (WAL mode), and each row keeps its session id, so streams don't smear together; list/search/pick/export --session <id> isolates one. For a tree of agents the nicer pattern is labeling: launch each agent's shell with BACKSCROLL_HOST=agent-7 backscroll run … — every command gets tagged, --host agent-7 filters any view (CLI, web UI, MCP), and stats --by host gives you a per-agent failure/latency table. That's essentially the setup described in the agents-audit doc.

Env capture: not today — a row is command, output, exit, cwd, duration, host/session, plus an optional note. It's feasible for exec (we spawn the process, so we could record env at launch), and the reason I haven't shipped it is that env is exactly where secrets live — a raw dump is a footgun. If it ships it'd be allowlist-based (exec --env 'PATH,GIT_*' style) with the redaction pass applied on top, never a full dump. Filesystem snapshots I'd keep out of scope (zfs/btrfs/restic territory), but an allowlisted env var is a natural place to carry a snapshot id along with each command (SNAP_ID=… backscroll exec …).

If allowlisted env capture would actually be useful in your orchestration setup, open an issue — the earlier threads here already turned into shipped changes (0600 DB perms, prune --max-size), so that's not a rhetorical invitation.