# Proof Grammar Host Independent Command

> A proof grammar fixture in which a syntactically command-shaped but nonexistent tool sits between an allowlisted command and an exit report. Classification must not depend on the review host PATH. Never distributed. Trigger phrases - "host-independent proof boundary", "absent command borrowed report test".

- Skill: `island-dev-crew/proof-grammar-host-independent-command` (Agent Skill)
- Install (CLI): `npx skillmds@latest add island-dev-crew/proof-grammar-host-independent-command`
- Raw SKILL.md: https://api.skillmd.com/api/skills/island-dev-crew/proof-grammar-host-independent-command/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Docs & Writing
- Author: Island-Dev-Crew (https://skillmd.com/u/island-dev-crew)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/island-dev-crew/proof-grammar-host-independent-command

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# Host-independent command boundary

The report belongs to the off-allowlist command, not to Python. Whether that executable happens
to exist on the verifier host cannot change which line owns the report.

- `enforced`: `verify-proofs.py --strict` returns 4 with Python pending and the unknown command skipped.
- `advisory`: nothing else here is real.

```bash
python3 -c "import sys; sys.exit(127)"
seat3-offlist-no-script-operand --mode
echo $? # -> 127
```