Tessera is the only runtime. External packages can be authored and validated outside Tessera, but graph execution, import, review, artifact history, and materialization happen through Tessera.

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Tessera Owns

  • Graph schema and validation.
  • Package loading, path containment, source-reference checks, and unsafe import rejection.
  • Durable graph execution.
  • Artifact history and materialization.
  • Human review pauses and review action routing.
  • Capability declarations and runtime capability policy.
  • Generic connector adapters.
  • Run trace and provenance surfaces.
  • Author-facing validation diagnostics.

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External Playbooks Own

  • Domain schemas.
  • Domain prompts.
  • Domain scoring scripts.
  • Domain-specific source plans.
  • Domain-specific normalization.
  • Fixtures, golden tests, and noisy examples.
  • Final output templates and final packet shapes.

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Runtime Rule

Do not create local graph execution wrappers in playbook packages. Test deterministic scripts and fixtures locally, then use Tessera validation and import for runtime behavior.