Canary

The canary fuzzer is a minimal test that validates the fuzzing infrastructure itself. It always exits with a non-zero status, confirming that CFO correctly detects, records, and reports failures.

Running

./zig/zig build fuzz -- canary

What It Does

The canary runs a trivial Python script that prints to stderr and calls sys.exit(1). There is no logic — it fails unconditionally.

CFO treats this exit code as a fuzzer failure. It creates a SeedRecord with ok=false and includes it in the GCS upload alongside real fuzzer results. If the canary ever passes, or fails to appear in the results at all, the fuzzing infrastructure itself is broken — not any specific piece of infrastructure.

The canary is the “does CFO even work?” check.

Source

src/fuzz_tests/canary.py