| `brush-core/src/expansion.rs` | corpus divergence D1: added `ExpansionPiece::LiteralText` — literal unquoted text is never field-split (bash splits only expansion results) but keeps glob characters active. Parameter-expansion substitutions (`${v:-word}` etc.) convert back to splittable at the expansion boundary; `ExpanderOptions.field_split_literal_text` lets data-string callers opt in. Upstream candidate. |
| `brush-core/src/completion.rs` | `compgen -W` word list opts into `field_split_literal_text` (the -W string is data) |
| `brush-shell/tests/cases/compat/ifs.yaml` | removed `known_failure` from 3 IFS tests the D1 fix repairs |
| `brush-core/src/gate.rs` (new) + `lib.rs` | the `Gate` trait (docs/NASH.md §4.2): process-global, verdict-shaped hook; allow-all default so an unconfigured shell behaves exactly like upstream |
| `brush-core/src/commands.rs` | `SimpleCommand::execute` split into gate wrapper + `execute_inner`: `on_exec` before dispatch (Deny short-circuits), completion correlated through all three spawn-result variants |
| `brush-core/src/processes.rs` | `ChildProcess.gate_token` + `on_exit` reporting from `wait()`/`poll()` (128+signal for signal deaths) |
| `brush-shell/src/entry.rs` | `set_exit_hook` seam so nash can flush its event buffer before `process::exit` |
| `brush-core/src/interp.rs` | `spawn_pipeline_processes` interposes a tee on each `a \| b` link when observation is active (`nash_spawn_pipe_tee`): a copier thread mirrors a bounded prefix, preserving backpressure and SIGPIPE, reports before closing the write end. No tee on the unobserved fast path. |
