Debugging SSA Fuzzer Failures

This skill provides the complete workflow for debugging SSA optimization bugs discovered by CI fuzzers. It combines two sub-skills:

1. extract-fuzzer-repro — Extract a Noir project from CI failure logs
2. bisect-ssa-pass — Bisect SSA passes to find the one that breaks semantics

When to Use This Skill

Use this when:

• A pass_vs_prev fuzzer test fails in CI
• You have a GitHub Actions URL showing a fuzzer failure
• You need to go from "CI is red" to "I know which SSA pass has the bug"

Note: This workflow is tailored for pass_vs_prev failures, which detect SSA passes that break semantic preservation. Other fuzzers exist that test different properties and may require different debugging approaches. Identify the fuzzer type from the failing test name in the GitHub logs — it follows the format targets::<fuzzer_type>::tests::fuzz_with_arbtest. If the failure comes from a fuzzer other than pass_vs_prev, ask the developer for guidance on how to proceed.

Workflow Overview