How to Deduplicate Flaky Test Failures in AI Prompt Suites by Root Cause

When a shared dependency like an HTTP client or model provider fails during testing, it can trigger dozens of simultaneous test failures that appear unrelated in standard reports. This misrepresentation inflates flake counts, clutters triage backlogs, and can bury genuine individual regressions in noise. A practical solution involves computing a short 'signature' string from each failure using fields like HTTP status, provider error code, exception class, and assertion site — while deliberately excluding test names, full messages, and timestamps. Error messages must be normalised before hashing to strip out variable data such as UUIDs, timestamps, and inline content, ensuring that failures sharing the same root cause produce identical signatures. The goal is for each signature group to represent a single fixable incident, making large test runs legible at a glance.