# Invariant Spec: execution_isolation
### Scope
- **Purpose**: Verify that each `program_tools run` invocation uses an isolated workspace with no cross-run contamination.
- **Responsibility**: Sequential runs produce separate workspaces; concurrent runs do not bleed source files.
- **In Scope**: Workspace path uniqueness per invocation; source file isolation between concurrent runs.
- **Out of Scope**: Artifact caching with shared `--target-dir` (→ `param/target_dir.md`); output isolation (→ `invariant/output_determinism.md`).
### IC-1: Sequential runs use separate workspaces
**Given:** Two compilable programs `a.rs` and `b.rs` that print different output
**When:** `program_tools run a.rs` followed by `program_tools run b.rs` (sequential, no `--keep`)
**Then:** Both exit `0`; each run produces only its own output; no source or artifact from the first run appears in the second run's workspace
### IC-2: Concurrent runs do not bleed source files
**Given:** Two compilable programs `a.rs` and `b.rs` launched simultaneously
**When:** Both `program_tools run a.rs` and `program_tools run b.rs` run concurrently
**Then:** Both exit `0`; each run produces only its own correct output; workspace directories are distinct; neither run's sources appear in the other's workspace
**Commands:** run
### Cross-References
| doc | `docs/invariant/002_execution_isolation.md` | Canonical execution isolation contract |
| test | `tests/inc/runner_test.rs` | Integration tests verifying per-run workspace isolation |
| param | `tests/docs/cli/param/target_dir.md` | `--target-dir` flag: shared cache without workspace pollution |