R11.8: Thread-safe singleton initialization

Short answer: Singletons use atomic locks or double-checked init. Two threads can both create the singleton.

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=R11.8

What it catches

Thread-safe singleton initialization: singletons use atomic locks or double-checked init.

Why

Two threads can both create the singleton.

A bad example

if (!inst) inst = make();

A good example

with lock:
    if inst is None:
        inst = make()

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 R11.8 -- 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.

R11.1 Atomic read-modify-write
R11.2 No dangling unawaited promises
R11.3 Race condition prevention
R11.4 Deterministic reducer purity
Every rule