Catches the mistakes coding agents repeat before they merge: a pull-request gate with no model call and no API key.
Short answer: State reducers remain pure functions without side effects. A reducer with side effects gives a different state each time it is replayed.
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=R11.4
Deterministic reducer purity: state reducers remain pure functions without side effects.
A reducer with side effects gives a different state each time it is replayed.
case 'add': log(action); state.n++; return state;
case 'add': return { ...state, n: state.n + 1 };
A person can silence one finding with brevio-core: ignore R11.4 -- 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.