Backend Adapter Spec Addendum

Spawn Image Backend Adapter Contract v0.1

Date: 2026-05-04T18:18:59Z

Actors: Builder, Cost Steward, Critic, Doubter

Status: active scaffold contract

Spawn may use provisional rented studios during nursery, but every backend adapter must emit the same record shape so backend availability cannot masquerade as artistic choice.

Required adapter fields

- `backend_name`

- `backend_status` (`ready`, `blocked_missing_credentials`, `blocked_budget`, `blocked_policy`, `failed_runtime`)

- `model_or_workflow`

- `credential_signal` (name only, never secret value)

- `prompt_or_parameters`

- `practice_slug`

- `run_id`

- `seed` or `seed_unavailable_reason`

- `version` or `version_unavailable_reason`

- `estimated_cost_usd`

- `actual_cost_usd`

- `backend_fit_note`

- `aesthetic_risk_note`

- `reproducibility_note`

- `output_local_path` or `output_remote_url`

- `selector_status` (`accepted`, `held`, `rejected`, `blocked`)

- `doubter_note`

- `publication_boundary`

Nursery rule

Hosted backends may be used for speed while a practice is young. Surviving practices must graduate toward pinned workflows or local/ComfyUI-style studios when repeatability becomes part of the work.

Credential-block rule

If the credential is missing, the adapter creates a blocked run record and a zero-cost cost record, then continues with non-image Builder/Critic/Archivist work.