Catches the mistakes coding agents repeat before they merge: a pull-request gate with no model call and no API key.
Short answer: Concurrent mutations use compare-and-swap or row locks. Two writers that read, change and write lose one of the changes.
Group: State and concurrency. Status: stable. Generated from the rule definitions; do not edit by hand.
Playground: https://brevio.pro/tools/agent-guard-playground?rule=R11.1
Atomic read-modify-write: concurrent mutations use compare-and-swap or row locks.
Two writers that read, change and write lose one of the changes.
const n = await get(); await set(n + 1);
await db.update({ where: { id, version }, data: { n: n + 1, version: version + 1 } });
A person can silence one finding with brevio-core: ignore R11.1 -- reason on the line or the line above. Without the reason it does not count. An agent cannot silence it: the agent hook and the MCP tools never honour the comment, and a pull request that adds one is reported until a reviewer allows it. Fixing the code is still the better answer.
To change what the rule flags, edit its definition in dev_rules.py or code_rules/__init__.py. That is a code change and is reviewed like one.