# algocline-engine::execution
`algocline-engine::execution` — v2 execution module.
Provides the engine-level session lifecycle machinery:
- [`SessionRecord`] — per-session ownership bundle (state, broadcast tx,
cancellation token, join handle, response senders).
- [`SessionRegistryV2`] — registry that spawns, tracks, and controls v2
sessions (coexists with the legacy `SessionRegistry` in `session.rs`).
- [`driver_loop`] — background async fn that drives a session to completion,
embedding the four cooperative cancellation checkpoints (Crux R2).
- [`BroadcastObserverHandle`] — concrete [`algocline_core::execution::ObserverHandle`]
implementation backed by a `broadcast::Receiver<ProgressEvent>` (Crux R3).
# Design invariants
- **Crux R1**: No `rmcp::*`, `progressToken`, `_meta`, `notifications/*`, or
`mcp_`-prefixed identifiers in this module tree.
- **Crux R2**: Cancellation uses `CancellationToken::cancel()` only;
`JoinHandle::abort()` and process-kill paths are absent.
- **Crux R3**: `observe()` is sync and returns a valid handle even with zero
pre-registered observers (sink-free fan-out).