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majordomo/docs/adr/0016-imagegen-interface.md
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feat(llamaswap): add llama-swap provider + canonical imagegen interface
Add provider/llamaswap, a tailored provider for llama-swap (the model-swapping
proxy over llama.cpp / stable-diffusion.cpp). Its chat path delegates to
provider/openai at {base}/v1 — no duplicated wire client (ADR-0007) — with
legacy max_tokens, a Bearer no-key placeholder for keyless local instances, and
a timeout-free client so cold model swaps rely on context deadlines. The
"tailored" surface is concrete management methods (ListModels / Running /
Unload) that don't belong on the canonical llm.Provider interface. The
llama-swap:// DSN scheme builds an http base URL (local-first); a no-URL
built-in errors clearly on use, mirroring foreman.

Add imagegen, a new canonical text-to-image interface separate from llm
(Request/Result/Model/Provider; Image = llm.ImagePart so generated images feed
straight back into chat). First backend is llama-swap via OpenAI
/v1/images/generations (b64_json, bytes-only). Re-exported from the root. v1 is
txt2img only.

Hermetic httptest coverage for chat delegation, management endpoints, image
decode, and scheme wiring. ADR-0015 + ADR-0016, README support matrix +
image-gen section, CLAUDE.md package map, and progress.md updated in the same
commit.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
2026-06-27 15:01:54 -04:00

2.3 KiB

ADR-0016: imagegen — a canonical text-to-image interface

Status: Accepted — 2026-06-27

Context

mort needs to generate images (via llama-swap's stable-diffusion.cpp backend), and majordomo had no image-generation surface. Image generation does not fit the chat contract: there are no conversation messages, tools, streaming, or failover-chain semantics — forcing it through llm.Request/llm.Response/ llm.Model would overload that contract with mostly-unused fields. The user asked for "a new ai image interface as opposed to llm".

Decision

  • A new canonical leaf package imagegen, parallel to llm, re-exported from the root (ImageModel, ImageProvider, ImageRequest, ImageResult, ImageOption, plus WithImageCount/WithImageSize). Providers import imagegen; mort codes to the interface, not to llama-swap.
  • Minimal v1 surface (text-to-image only):
    • Request{ Prompt string; N int; Size string } — zero values mean provider default (N=0 → backend default count; "" Size → backend default).
    • Result{ Images []Image; Raw any }.
    • Model.Generate(ctx, Request, ...Option) (*Result, error) and Provider.ImageModel(id, ...ModelOption) (Model, error).
    • Functional options + Request.Apply, mirroring llm.
  • type Image = llm.ImagePart (bytes + MIME). Reusing the chat content type means a generated image drops straight back into a chat turn (llm.UserParts(res.Images[0])) with no conversion — the key interop win.
  • Out of scope for v1 (designed-for, deferred): image edits / img2img, the raw A1111 SDAPI, masks/seeds/steps, streaming, and registry-level image-model DSN resolution (construct the provider directly for now).
  • First implementation: provider/llamaswap, targeting OpenAI /v1/images/generations with response_format: "b64_json" (bytes inline; we never fetch remote URLs — mirrors ImagePart's bytes-only contract).

Consequences

  • Image generation is provider-agnostic from day one; a future OpenAI DALL·E or Gemini image backend implements the same interface.
  • The narrow interface keeps the door open for richer requests without breaking callers (additive fields/options).
  • No health/failover for image models yet; if needed it can be added as a separate chain type rather than retrofitting the chat chain.