R11.6: Optimistic UI rollback

Short answer: Optimistic state updates retain rollback snapshot on failure. An optimistic update with no snapshot cannot be undone when the server says no.

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=R11.6

What it catches

Optimistic UI rollback: optimistic state updates retain rollback snapshot on failure.

Why

An optimistic update with no snapshot cannot be undone when the server says no.

A bad example

setItems([...items, item]); await save(item);

A good example

const snap = items; setItems([...items, item]);
try { await save(item); } catch { setItems(snap); }

How it is checked

Nothing yet. No scanner and no slice card checks it: it is a standing rule for authors and reviewers.

How to silence it

A person can silence one finding with brevio-core: ignore R11.6 -- 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.

R11.7 Bounded in-memory queues
R11.8 Thread-safe singleton initialization
R11.1 Atomic read-modify-write
R11.2 No dangling unawaited promises
Every rule