R5.1: Deterministic graceful fallbacks

Short answer: Return explicit degraded status, never fabricated metrics. A made-up number looks real on a dashboard and drives wrong decisions.

Group: Reliability and fallbacks. Status: stable. Generated from the rule definitions; do not edit by hand.

Playground: https://brevio.pro/tools/agent-guard-playground?rule=R5.1

What it catches

Deterministic graceful fallbacks: return explicit degraded status, never fabricated metrics.

Why

A made-up number looks real on a dashboard and drives wrong decisions.

A bad example

return { revenue: lastKnown ?? 0 };

A good example

return { status: 'degraded', revenue: null };

How it is checked

A one-line card in the prompt of a slice that touches matching files (dev_rules.slice_micro_rules).

How to silence it

A person can silence one finding with brevio-core: ignore R5.1 -- 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.

R5.2 HTTP empty-body hygiene
R5.3 Bounded retry with jitter
R5.4 No silent exception swallowing
R5.5 Process & lock safety
Every rule