check-jsonschema --builtin-schema: Vendored Schemas

check-jsonschema --builtin-schema vendor.github-workflows validates workflow files against a bundled schema with no network access.

Vendored (built-in) schemas let check-jsonschema validate common CI config files offline, which is exactly what you want on a locked-down runner.

What it does

The --builtin-schema flag selects a schema bundled with check-jsonschema instead of a file or URL. vendor.* schemas are copies of SchemaStore schemas (github-workflows, github-actions, gitlab-ci, renovate, dependabot, azure-pipelines, and more) so validation works without downloading anything.

Common usage

# list every bundled schema name
check-jsonschema --builtin-schema list

# GitHub Actions workflow files
check-jsonschema --builtin-schema vendor.github-workflows \
  .github/workflows/*.yml

# a reusable/composite action definition
check-jsonschema --builtin-schema vendor.github-actions action.yml

# GitLab CI
check-jsonschema --builtin-schema vendor.gitlab-ci .gitlab-ci.yml

Options

In CI

Prefer a vendor.* built-in over a remote --schemafile URL on CI: it avoids a network call, so an offline or proxied runner still validates and the job cannot flake on a SchemaStore outage. Run --builtin-schema list once to confirm the exact name in your installed version.

Common errors in CI

--builtin-schema: invalid choice: 'github-workflow' means a wrong or renamed name (note the plural github-workflows); run --builtin-schema list. Validating an Azure pipeline without --data-transform azure-pipelines yields spurious is not valid under any of the given schemas errors because the template syntax is not decoded. A vendor.* name missing from your version means the package is too old; upgrade with pipx.

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