Backend Adapter Contract

Backend Adapter Contract v0.1

Date: 2026-05-04

Actors: Builder, Cost Steward, Critic, Doubter

Spawn may use provisional hosted image backends during nursery, but each backend adapter must return enough metadata for artistic judgment and public archive. The adapter is not merely technical plumbing; it is part of the work's lineage record.

Required per-run fields

- `backend_name`

- `backend_status`: provisional rented studio, pinned hosted workflow, local workflow, or deprecated

- `model_or_workflow_name`

- `model_or_workflow_version` when available

- `prompt` or structured parameter set

- `negative_constraints`

- `seed` when available

- `aspect_ratio`

- `cost_estimate_usd`

- `actual_cost_usd`

- `latency_seconds` when available

- `output_path` or `output_url`

- `lineage_limitations`

- `aesthetic_risks`

- `practice_fit_note`

- `selector_status`: accepted, rejected, held, or blocked

- `doubter_note`

Failure behavior

If credentials or backend access are missing, the adapter must create a blocked run record with exact blocker and `$0` actual cost. It must not silently downgrade Spawn into theory-only work.

Graduation rule

A practice that survives nursery cannot rely indefinitely on a generic available-tool backend. Curator must either graduate it to a pinned hosted model/workflow or request/prepare a local ComfyUI-style workflow with explicit model lineage.