Artifact validation and fidelity gates

Canonical builds validate every terminal artifact before publication. Validation is part of the execution result: an artifact is valid, valid_with_warnings, invalid, unavailable, or skipped by explicit policy. Intermediate artifacts remain not_requested unless they become selected targets.

The built-in registry provides deterministic structural validators for text, JSON, YAML, markup, delimited text, PDF, PNG, JPEG, ZIP-based packages, and RIFF/WAVE. Each result records the validator ID, implementation version, provider, state, and structured diagnostics in renderflow-run.json.

execution:
  validation:
    required: true
    validators:
      - validator.core.non_empty
      - validator.core.png
    failure_mode: branch_local
    allow_unavailable: false
  reject_loss_classes:
    - lossy
    - unknown

With branch_local, a failed target is withheld while independent valid targets may be published, producing a partial run. With fatal, any blocking validation or fidelity result prevents every target from being published. Setting required: false records terminal validation as skipped; it does not silently claim validity.

An unavailable requested validator blocks publication unless allow_unavailable: true. Warnings remain publishable. reject_loss_classes can reject lossless, partial, lossy, path_dependent, or unknown fidelity declarations independently of the numeric planning-time minimum_fidelity threshold.

Capability conformance matrix

The generated matrix is the source for format support claims:

renderflow capabilities --matrix
renderflow capabilities --matrix --format json
renderflow capabilities --matrix --format yaml

Each row distinguishes implemented, experimental, unavailable, and planned support and names declared capabilities, executors, providers, validators, fixtures, platforms, deterministic validation, and loss profile. Its machine-readable contract is schemas/renderflow-conformance-v1.schema.json.