JEV OAS Sentinel – catch breaking API changes hidden in OpenAPI prose

The independent community project JEV OAS Sentinel released a public alpha tool that compares two OpenAPI documents in two layers: deterministic structural checks plus TypeSafe Jev semantic evaluation of changed descriptions, examples, defaults, retry behavior, ordering, pagination, authorization, and error semantics. The tool returns typed decisions and probabilities rather than writing reviews or changing specifications, with deterministic Python code deciding whether to pass, request review, or block; advisory mode is the default. The project states it is not affiliated with, maintained by, or endorsed by TypeSafe AI, and its benchmarks suite exercises ten semantic-only contract changes.

JEV OAS Sentinel Actions Tags 2 Catch behavioral breaking changes hidden in OpenAPI prose—changes that structural schema diff tools cannot see. jev-oas-sentinel compares two OpenAPI documents in two layers: 1. deterministic checks find definite structural compatibility problems; 2. TypeSafe Jev evaluates bounded semantic questions about changed descriptions, examples, defaults, retry behavior, ordering, pagination, authorization, and error semantics. JEV never writes a review or changes a specification. It returns typed decisions and probabilities; deterministic Python code decides whether to pass, request review, or block. Note JEV OAS Sentinel is an independent community project. It is not affiliated with, maintained by, or endorsed by TypeSafe AI. No API key or network call to JEV is needed for this preview: git clone https://github.com/ShuhanSun/jev-oas-sentinel.git cd jev-oas-sentinel uvx jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --dry-run \ --format markdown The example changes an operation's consumer-facing prose. The structural schema remains compatible, but Sentinel identifies the operation that needs semantic review: | Block | Review | Notice | |---:|---:|---:| |0|1|0| | Severity | Operation | Rule | Finding | |---|---|---|---| | review | GET /orders | semantic-evaluation-planned | Contract prose changed and would be sent to JEV | The reproducible benchmarks/ https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/benchmarks suite exercises ten semantic-only contract changes covering pagination, ordering, retries, authorization, timestamps, error meaning, and other consumer-visible promises. The independent jev-oas-sentinel-demo https://github.com/ShuhanSun/jev-oas-sentinel-demo repository verifies the public @v0 Action and SARIF upload from a real consumer workflow. The current public alpha supports OpenAPI JSON and standards-compliant safe YAML, including anchors and merge keys. Internal and multi-file local $ref targets are resolved with cycle protection. Remote $ref targets are rejected rather than fetched implicitly. Advisory mode is the default. Local references are restricted to the specification's directory tree by default. For repositories that keep shared schemas in a parent directory, set an explicit trusted root: jev-oas-sentinel compare \ --base api/base/openapi.yaml \ --head api/head/openapi.yaml \ --ref-root . \ --no-jev - uv https://docs.astral.sh/uv/ for the recommended installation and development workflow - Python 3.9+ when running without uv - A TypeSafe API key for live semantic evaluation Runtime dependencies are PyYAML for standards-compliant OpenAPI parsing and, on Python 3.10+, truststore for the operating system's native certificate store. Tool installers keep the CLI isolated from system and project Python environments. Python 3.9 uses its configured OpenSSL CA bundle and can be given a private bundle explicitly. Run the published CLI once without installing it: uvx jev-oas-sentinel --version Or install it as an isolated command: uv tool install jev-oas-sentinel or pipx install jev-oas-sentinel To work on the current checkout, install it in editable mode: uv tool install --editable . jev-oas-sentinel --version On a Mac or corporate network that relies on certificates from the operating-system trust store, add --system-certs to the uv install command. Managed installs can be upgraded or removed cleanly with uv tool upgrade jev-oas-sentinel and uv tool uninstall jev-oas-sentinel . ./jev-oas-sentinel remains available as a no-install fallback when working directly in a source checkout. Run deterministic checks only: jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --no-jev \ --format markdown Run a live Jev evaluation: export TYPESAFE API KEY="..." jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --format markdown Preview which operations would require JEV without an API key or network call: jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --dry-run \ --format json Bound API usage and transport behavior explicitly in CI: --max-jev-calls 20 --timeout 30 --max-retries 3 Put shared policy in .jev-sentinel.yaml at the directory where the command runs. The format is versioned, CLI options override file settings, and --config PATH selects another file. Use --no-config for a fully explicit run. version: 1 mode: advisory fail on review: false model: jev-1.13.0 review threshold: 0.65 block threshold: 0.90 max jev calls: 20 timeout: 30 max retries: 3 suppressions: - operation: GET /legacy/ rule: semantic-contract-review expires: 2099-12-31 owner: api-platform reason: Migration is tracked in API-123 Suppressions require an owner, reason, and expiration date. A matching block or review becomes a notice but remains in JSON, Markdown, and SARIF with its original severity and suppression metadata. An expired suppression fails the run so exceptions cannot silently become permanent. Operation and rule values support shell-style , ? , and character-set patterns. For security, repository configuration cannot set the JEV endpoint, API-key file, CA bundle, local-reference root, report path, or trace path. Those remain explicit CLI options. See examples/jev-sentinel.yaml https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/examples/jev-sentinel.yaml for a complete example. The client also accepts --api-key-file PATH . Never commit that file. To inspect the exact JEV input and output, opt in to a sanitized trace: Show the trace on stderr while keeping the report on stdout. jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --show-jev-io \ --format markdown Or write the trace as JSON. jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --jev-io-output reports/jev-io.json \ --format markdown The versioned trace omits request headers and recursively redacts the configured API key plus common credential fields from captured data. Trace files are created with owner-only permissions on POSIX systems. They do include the contract fragments sent to JEV, so treat them as potentially sensitive and do not publish them unintentionally. On Python 3.10 and newer, HTTPS verification uses the operating system's native certificate store, including enterprise CAs installed in macOS Keychain or the Windows certificate store. For Python 3.9 or a private CA bundle, use --ca-bundle PATH , JEV CA BUNDLE , or the standard SSL CERT FILE environment variable. TLS verification is never disabled. jev-oas-sentinel compare \ --base examples/base-openapi.yaml \ --head examples/head-openapi.yaml \ --ca-bundle /path/to/company-ca.pem \ --format markdown Write SARIF for GitHub code scanning: jev-oas-sentinel compare \ --base openapi-base.yaml \ --head src/main/resources/openapi.yaml \ --format sarif \ --output reports/jev-oas-sentinel.sarif The repository includes a composite action. A complete pull-request example is available at examples/github-workflow.yaml https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/examples/github-workflow.yaml . - uses: ShuhanSun/jev-oas-sentinel@v0 with: base: /tmp/openapi-base.yaml head: src/main/resources/openapi.yaml api-key: ${{ secrets.TYPESAFE API KEY }} format: sarif output: reports/jev-oas-sentinel.sarif - --mode advisory default : definite structural breaks block; semantic risks request review. - --mode enforce : a semantic break blocks only when both the breaking probability and promise-violation probability cross conservative thresholds. - --fail-on-review : return a non-zero exit code for review findings as well as blocks. Thresholds are configurable: --review-threshold 0.65 --block-threshold 0.90 Do not enable enforcement until the questions and thresholds have been evaluated on representative changes from your own APIs. - removed operations; - removed parameters; - new required parameters; - optional parameters becoming required; - required request bodies being introduced; - removed response status codes; - removed request or response media types; - removed request or response properties; - request properties becoming required; - response properties no longer being guaranteed; - request enum narrowing and response enum expansion; - incompatible schema type or nullability changes; - security requirement changes; - other non-documentation structural changes, conservatively routed to review. Each changed operation receives one request containing four independent questions: - change kind: documentation-only, additive, behavioral, breaking, or unclear; - affected dimension: defaults, response meaning, ordering/pagination, retry/idempotency, authorization, deprecation, error semantics, or another dimension; - whether every old consumer-visible promise remains preserved; - ordered migration burden. The report retains the selected values, full probability distributions, confidence values, resolved model, token usage, and deterministic source location. - 0 : no blocking finding and no review finding when --fail-on-review is used ; - 1 : policy blocked the change; - 2 : invalid input or execution failure. - API keys are read from TYPESAFE API KEY or an explicit key file and are never included in reports. - Only changed operation fragments are sent to Jev. - Structural compatibility rules remain deterministic. - API errors fail closed in enforcement mode and request review in advisory mode. - OpenAPI descriptions are untrusted input. The tool does not execute examples, extensions, URLs, or code found in a specification. See docs/architecture.md https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/docs/architecture.md for design boundaries and extension points. uv sync --locked uv run python -m unittest discover -s tests -v uv run jev-oas-sentinel --version uv build --no-sources CI runs the tests on Python 3.9, 3.11, and 3.13 and validates both distribution artifacts. See docs/releasing.md https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/docs/releasing.md for the trusted-publishing release process. - Read CONTRIBUTING.md https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/CONTRIBUTING.md before opening a pull request. - See the directional ROADMAP.md https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/ROADMAP.md . - Use the issue forms for reproducible bugs and concrete compatibility proposals. - Use docs/launch.md https://github.com/ShuhanSun/jev-oas-sentinel/blob/main/docs/launch.md when sharing the project without overstating benchmark or model claims. JEV OAS Sentinel is not certified by GitHub. It is provided by a third-party and is governed by separate terms of service, privacy policy, and support documentation.