Polychro¶
Polychro is the open source AI linter for spec-driven development. It lets your coding agent lint as you build, not hand it off to the one gating your CI pipeline — in-process, multi-format, and agent-native, rebuilt for the flood of AI-generated specs that legacy OpenAPI-in-CI linters were never built to see. It shifts linting all the way left — out of the CI gate and into the coding agent's inner loop, catching a bad spec at agent speed, before it ever reaches a pull request.
Polychro reads a specification — YAML, JSON, XML, Markdown, or HTML — and tells you what's wrong with it in a single, fast pass: structural mistakes, schema violations, broken conventions, and security anti-patterns. One binary, one config, one diagnostic format — fast enough to sit inside an AI agent's generate-validate-retry loop.
What that means for you¶
You're building AI agents or tools — give the agent a deterministic guardrail that lints its own output in the same turn, sub-second and in-process, or over MCP. → MCP Server guide
You run CI or a platform — gate any spec on every PR with structured SARIF, and collapse a pile of linters into one binary, one config. → GitHub Action guide
You author specs or rules — reuse your Spectral rules, lint more than OpenAPI, and write custom rule functions in JavaScript, Python, Groovy, or Java. → Rulesets guide
See Getting Started for the fastest path to your first lint.
Key features at a glance¶
| Feature | Description |
|---|---|
| Polyglot Validation | Lint YAML, JSON, XML, Markdown, and HTML specs through one pipeline |
| Composable Pipeline | Layered well-formedness → schema-model → ruleset → format-aware validation |
| Native Executable | Standalone binaries for Linux, macOS, and Windows — no JVM required |
| MCP Server Mode | Expose linting as MCP tools for AI agent consumption out of the box |
| GitHub Action | Lint specs in CI with structured SARIF output |
| Spectral-Format Rulesets | Execute governance rulesets with given/then semantics |
| Polyglot Custom Functions | Sandboxed JavaScript, Python, or Groovy rule functions via GraalVM |
| Java Custom Functions | Native RuleFunction SPI — fastest path, no GraalVM required |
| Schema-Model Validation | Formal document models including JSON Schema Draft 2020-12 and JSON Structure |
| Unified Diagnostics | All validators produce the same Diagnostic format — one pipeline, one output |
| Embeddable Java API | In-process linting for JVM applications — no subprocess, no Node.js |
For the full feature list see Features.
What it is not¶
- Not a meta-linter. Super-Linter and MegaLinter bundle dozens of third-party tools in a large Docker image. Polychro is a single engine that owns the spec-validation slice end to end — no Docker dependency, no per-tool config to stitch together.
- Not OpenAPI-only. Polychro speaks the Spectral ruleset format, but treats arbitrary YAML, JSON, XML, Markdown, and HTML as first-class specs — capabilities, MCP manifests, CRDs, instruction files, not just OpenAPI.
- Not a Node.js tool. Polychro runs as a GraalVM-native binary with sub-second cold start, or in-process inside any JVM — no Node.js runtime, no 2–5 s subprocess startup.
Continue reading¶
- Getting Started — install Polychro and run your first lint
- Features — the full capability list
- Architecture — how the validators compose into one pipeline
- Tutorial — an end-to-end linting workflow
- Comparison — how Polychro compares to meta-linters and Spectral
- Roadmap — what's coming in upcoming alphas
