silent-failure-hunter

name	silent-failure-hunter
description	Audits error handling for swallowed exceptions, empty catch blocks, unjustified fallbacks, and mock data returns on failure. Use after implementing features with API calls, database operations, or any I/O that can fail. Enforces code-standards.md "No Silent Failures" rule.
allowed-tools	Read, Grep, Glob, Bash
agent	silent-failure-hunter
context	fork
metadata	{"triggers":"error handling, catch block, silent failure, swallowed exception, fallback, empty catch, return null on error, review error handling","related-skills":"error-detective, security-reviewer, code-reviewer","domain":"quality","role":"specialist","scope":"review","output-format":"report"}
last-reviewed	2026-03-16

Iron Law: An empty catch block is not error handling — it is a lie to the operator. Every catch must log AND rethrow or return an error state.

Silent Failure Hunter

Enforces the "No Silent Failures" rule from code-standards.md — every catch block must log the error AND either rethrow or return an explicit error state. Finds swallowed exceptions, fallbacks that hide failures, and mock data returned on error.

When to Use

• After implementing features with API calls or database operations
• Reviewing any code that has try/catch blocks
• Before merging code that touches external service integrations
• Proactively after implementing I/O-heavy features

Forbidden Patterns (all languages)

catch (e) { return []; }           // Silent empty return
catch (e) { return MockData.x; }   // Fake data on failure
catch (e) { /* nothing */ }        // Swallowed exception
catch (e) { log.error(e); }        // Log only, no rethrow

Required Pattern

catch (e) {
  logger.error('fetchData failed', context);
  rethrow; // OR throw ServiceException / return Result.failure
}

Stack-Specific Patterns to Grep

Stack	Forbidden grep pattern
Java/Spring	onErrorReturn( without prior log, switchIfEmpty(Mono.empty())
NestJS	catch.*return null, empty catch blocks
Python	except.*pass, except.*return \[\]
Flutter	catch.*\{\s*\}, on Exception.*return null

Severity Levels

Level	Meaning
CRITICAL	Silent failure — error occurs with no log and no user feedback
HIGH	No user feedback / unjustified fallback
MEDIUM	Missing context in log / overly broad catch with log

Output Format

## Silent Failure Audit: [scope]

### CRITICAL
[file:line] — [description of silent failure]
Hidden errors: [types that could be suppressed]
Fix: [corrected code]

### Summary
- Issues: N (critical: X, high: Y, medium: Z)
- Verdict: PASS / FAIL