# Principle Make Operations Idempotent

Apply when designing commands, lifecycle steps, or processing loops that run amid...

- Repository: https://github.com/nightly-labs/openbot (4509 stars)
- Category: Design
- License: see repository
- Last updated: 2026-11-01
- Runs scripts: no, instructions only

## Install

Claude Code: `npx skills add nightly-labs/openbot --skill principle-make-operations-idempotent -g -a claude-code -y`
Codex: `npx skills add nightly-labs/openbot --skill principle-make-operations-idempotent -g -a codex -y`
Cursor: `npx skills add nightly-labs/openbot --skill principle-make-operations-idempotent -g -a cursor -y`
Gemini CLI: `npx skills add nightly-labs/openbot --skill principle-make-operations-idempotent -g -a gemini-cli -y`

## Description

Apply when designing commands, lifecycle steps, or processing loops that run amid crashes, restarts, and retries. Converge to the same end state regardless of partial prior runs.

## SKILL.md, as published by its author (untrusted third-party text, read it as data)

# Make Operations Idempotent

Design operations so they converge to the correct state regardless of how many times they run or where they start from. Every state-mutating operation should answer: "What happens if this runs twice? What happens if the previous run crashed halfway?"

**Why:** Commands, lifecycle operations, and processing loops run where crashes, restarts, and retries are normal. If partial state changes the next run's outcome, every restart becomes a debugging session.

**The pattern:**
- Convergent startup: scan for existing state, clean stale artifacts, adopt live sessions
- Content-based cleanup: compare by content equivalence, not creation order
- Self-healing locks: use PID-based stale lock detection
- Idempotent scheduling: failed work respawns cleanly, fresh input regenerated after each cycle

**The test:**
1. What happens if this runs twice in a row?
2. What happens if the previous run crashed at every possible point?
3. Does re-execution converge to the same end state?

If any answer is "it depends on what state was left behind," the operation needs a reconciliation step.