GitHub - Neelagiri65/equiv: Deterministic checker for behaviour-preserving code changes. Signed, re-runnable receipts; PR gate; single static binary. · GitHub
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Neelagiri65
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equiv
An LLM should not be the only thing reviewing LLM-written code.
equiv runs a changed function against its previous version on the same<br>deterministically generated inputs and reports whether the behaviour changed. If<br>it did, you get the exact input where they differ. Either way you get a<br>reproducible, signed receipt: re-run the check on any machine and you get the same<br>answer, byte for byte, without trusting any model's opinion.
Most code is now written by AI and reviewed by AI. A model saying "this looks<br>fine" is not verification. A deterministic check you can re-run yourself is.
Quickstart: the PR gate
List the functions whose behaviour must be preserved across a PR in a manifest<br>at the repository root. The format of each line is<br>: : , where arg types are int, str, or<br>list[int], comma separated:
src/math.py : total : int
Add the workflow at .github/workflows/equiv-review.yml:
on: pull_request<br>permissions: { contents: read, pull-requests: write, id-token: write }<br>jobs:<br>review:<br>runs-on: ubuntu-latest<br>steps:<br>- uses: actions/checkout@v4<br>with: { fetch-depth: 0 }<br>- uses: Neelagiri65/equiv@v0.1.0<br>with: { keyless: "true" }
Pin to a released tag (@v0.1.0) rather than @main so runs are reproducible<br>and do not change under you.
Each PR receives a comment. Every changed function is tested against its version<br>on the base branch. A change that preserves behaviour passes. A change that does<br>not is reported with the input that distinguishes the two versions. That<br>fails the check. Receipts are signed with Sigstore keyless signing, which stores<br>no key. They can be verified with cosign.
CLI
curl --proto '=https' --tlsv1.2 -LsSf \<br>https://github.com/Neelagiri65/equiv/releases/latest/download/equiv-cli-installer.sh | sh
equiv verify-receipt ">equiv review candidate.py reference.py<br>equiv verify-receipt
Exit codes: 0 equivalent, 1 diverges with a printed counterexample, 2<br>could not check.
Scope
equiv checks behavioural equivalence of a function against a reference, on<br>deterministically generated inputs. This is bounded random testing, not<br>exhaustive verification: a pass means no divergence was found on the generated<br>inputs. It can still miss an edge case that only shows up for an input that<br>was not generated. It does not check intent, architecture, security. It<br>cannot judge new functionality that has no reference to compare against. A<br>passing result means behaviour was preserved on the tested inputs. It does not<br>mean the change is correct. Supported input types in this version are int,<br>str and list[int].
How it works
Input generation and the verdict are computed in Rust from a fixed seed. The<br>language runtime is used only as an evaluator and never decides anything that<br>reaches the receipt. Receipts are identical across hosts. Receipts can be<br>signed with a local ed25519 key or with keyless Sigstore (OIDC). The keyless<br>path binds the signature to a verifiable CI identity rather than a stored<br>secret. The tool is a single static binary with no runtime dependencies,<br>prebuilt for macOS, Linux and Windows.
Documentation
docs/signing-model.md: receipt signing with ed25519...