# Proof Grammar Empty Assignment

> A proof grammar fixture in which an ordinary block-local variable is deliberately emptied before an allowlisted command. The empty binding must replay. Never distributed. Trigger phrases - "empty proof assignment", "empty local replay test".

- Skill: `island-dev-crew/proof-grammar-empty-assignment` (Agent Skill)
- Install (CLI): `npx skillmds@latest add island-dev-crew/proof-grammar-empty-assignment`
- Raw SKILL.md: https://api.skillmd.com/api/skills/island-dev-crew/proof-grammar-empty-assignment/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- 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-empty-assignment

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# Empty ordinary assignment

The first assignment makes a stale value observable. The second must clear it; silently dropping
`D=` leaves `poison` in place and makes the documented proof fail.

- `enforced`: verify-proofs.py replays both assignments and the proof exits 0.
- `advisory`: nothing else here is real.

```bash
D=poison
D=
python3 -c "import sys; sys.exit(0 if sys.argv[1] == '' else 1)" "$D"   # exit 0
```