SimContract: A Validation-Aware and Simulator-Authoritative Framework for Reproducible, Model-Replaceable Multi-Stakeholder Simulation with Governed AI Participation

SimContract is a contract-governed, validation-aware research framework for simulation-based decision experiments: heterogeneous simulation domains run behind one adapter contract; human, rule-based, ranked, and LLM-assisted controllers pass through the same two-tier validation path; every run produces a hashed, replayable evidence bundle. v0.3.1 is a backward-compatible remediation release. It fixes a cross-platform evidence-serialization defect: evidence writers now emit canonical UTF-8 bytes and hash exactly the bytes written, so per-file verification (files_ok) holds on platforms that rewrite newlines. Behaviour is unchanged on POSIX and the frozen benchmark reproduces content hash dd73a350… unchanged. Verified by a clean installed-wheel run on Linux/WSL2 and byte-level regression tests. Also adds reuse documentation, a bundle-only analyzer example, and a CI workflow config (not yet exercised on hosted runners). Independent native-Windows remediation was pending at release. The immutable software artifact evaluated for Paper 1 is SimContract v0.3.1. Updated reproduction instructions and reporting templates are maintained in the repository after the release tag. The archived source, wheel, verification script, and checksums remain unchanged.