fuzz-nightly.yml

name: Fuzz (nightly)

# PLAN.md Phase 1 bullet 1: differential fuzzing at 10^6 iterations/day in
# CI nightly. A single sequential run of that scale doesn't fit a normal
# job comfortably, so this shards across a matrix: 10 shards x 100,000
# iterations = 1,000,000 total, each shard seeded distinctly (see
# NULANG_FUZZ_SHARD_ID handling in src/fuzz.rs::fuzz_differential_extended)
# so they cover different mutant sequences rather than duplicating work.
#
# Kill criteria (PLAN.md Phase 1): any divergence found here is a Sev-1 if
# it touches Frozen-tier surface (bytecode/value-layout/wire-format
# semantics) -- this job fails loudly (test panic -> non-zero exit) rather
# than silently logging, precisely so that can't be missed.

on:
  schedule:
    # 03:00 UTC daily -- off-peak, doesn't compete with interactive CI runs.
    - cron: "0 3 * * *"
  workflow_dispatch: {} # allow manual runs for investigation

env:
  CARGO_TERM_COLOR: always

jobs:
  fuzz-shard:
    name: Differential fuzz shard ${{ matrix.shard }}
    runs-on: ubuntu-latest
    strategy:
      fail-fast: false # one shard's divergence shouldn't hide another's
      matrix:
        shard: [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
    steps:
      - uses: actions/checkout@v7

      - name: Install system dependencies
        run: sudo apt-get update && sudo apt-get install -y python3-dev

      - name: Install Rust
        uses: dtolnay/rust-toolchain@stable

      - name: Cache cargo
        uses: Swatinem/rust-cache@v2
        with:
          key: fuzz-shard-${{ matrix.shard }}

      - name: Run differential fuzz shard
        env:
          NULANG_FUZZ_ITERATIONS: "100000"
          NULANG_FUZZ_SHARD_ID: ${{ matrix.shard }}
        run: cargo test --lib --features wasm-backend fuzz_differential_extended -- --ignored --nocapture

      - name: Upload divergence log on failure
        if: failure()
        uses: actions/upload-artifact@v4
        with:
          name: fuzz-divergence-shard-${{ matrix.shard }}
          path: |
            /tmp/*.log
          if-no-files-found: ignore
          retention-days: 30