// End-to-end workflow for debugging SSA fuzzer failures from CI. Extracts a reproduction case from GitHub Actions logs, then bisects SSA passes to identify the bug. Use when a `pass_vs_prev` or similar fuzzer test fails in CI.
| name | debug-fuzzer-failure |
| description | End-to-end workflow for debugging SSA fuzzer failures from CI. Extracts a reproduction case from GitHub Actions logs, then bisects SSA passes to identify the bug. Use when a `pass_vs_prev` or similar fuzzer test fails in CI. |
This skill provides the complete workflow for debugging SSA optimization bugs discovered by CI fuzzers. It combines two sub-skills:
extract-fuzzer-repro — Extract a Noir project from CI failure logsbisect-ssa-pass — Bisect SSA passes to find the one that breaks semanticsUse this when:
pass_vs_prev fuzzer test fails in CINote: 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.
extract-fuzzer-repro)bisect-ssa-pass)Use the extract-fuzzer-repro skill to get a local Noir project from the CI logs.
Input: GitHub Actions job URL (e.g., https://github.com/noir-lang/noir/actions/runs/12345/job/67890)
Output: A Noir project directory with:
src/main.nr — The generated program that triggered the failureProver.toml — Input values that cause the bugQuick reference:
# Download logs from GitHub Actions
gh run view <run-id> --job <job-id> --log > fuzzer_log.txt
# Extract the Noir project (the skill has detailed instructions)
# Look for "Program:" and "Inputs:" sections in the log
Before bisecting, confirm the issue reproduces:
cd <extracted_project>
nargo execute
If using experimental features (like enums/match), add the appropriate flags:
nargo execute -Zenums
Use the bisect-ssa-pass skill to:
pass_vs_prev fuzzer compares interpretation results before and after each pass, so failures indicate semantic preservation bugsextract-fuzzer-repro — Detailed instructions for extracting from CI logsbisect-ssa-pass — Detailed instructions for SSA bisection and regression testsWorkflow for debugging SSA pass semantic preservation using the noir-ssa CLI. Use when a program's behavior changes incorrectly during the SSA pipeline - bisects passes to identify which one breaks semantics. The `pass_vs_prev` fuzzer finds such issues automatically.
Extract a Noir reproduction project from fuzzer failure logs in GitHub Actions. Use when a CI fuzzer test fails and you need to create a local reproduction.
Workflow for measuring and optimizing the ACIR circuit size of a constrained Noir program. Use when asked to optimize a Noir program's gate count or circuit size.
Minimize an SSA file that triggers a bug in the noir-ssa pipeline, producing the smallest possible reproduction case. Use after bisecting to identify which SSA passes cause the issue.
Guide for writing noirc_frontend unit tests. Use when adding, writing, or reviewing frontend tests — regression tests, reproduction tests, error-checking tests, or should_panic tests in the compiler frontend.
Guidelines for writing idiomatic, efficient Noir programs. Use when writing or reviewing Noir code.