FLUX.1 Kontext and Qwen-Image-Edit are a different kind of edit from img2img
and reach sd-server by a different path, and nothing in imagegen could
express it: EditRequest only had Init, which is noised and denoised back
under the prompt.

Measured against FLUX.1-Kontext on the netherstorm host 2026-07-30, on a
synthetic scene with a red rectangle, a blue rectangle and a flat background,
prompted "change the blue rectangle on the right to bright green, keep
everything else exactly the same":

  via init_images (the only path that existed)
      right rect (60,60,200) -> (47,82,228)   still blue, instruction ignored
      left rect  (200,60,60) -> (229,43,50)   drifted
      background (150,200,240) -> (154,211,229) drifted

  via extra_images (this change)
      right rect (60,60,200) -> (70,254,4)    green, as asked
      left rect  (200,60,60) -> (204,57,57)   intact
      background (150,200,240) -> (151,202,247) intact

No mask, no strength, no compositing — the model is handed the picture as
conditioning and the prompt as an instruction about it.

EditRequest.RefImages selects the path; when set, Init/Mask/Strength are
ignored rather than rejected, so a caller handing the same request to
whichever model is configured gets the better result on a Kontext-class model
instead of an error. The provider posts /sdapi/v1/txt2img with extra_images
(sd-server reads that field on both routes into gen_params.ref_images, where
the CLI's -r/--ref-image also lands); there is no init latent to denoise, so
sending one would only add noise to a pipeline that does not want any.

An all-empty reference set is refused: it would otherwise degrade into a
plain txt2img and render the prompt from scratch, which is not the request.

@@ -13,2 +13,4 @@
+	// RefImages is set — see there.
 	Init Image
 
+	// RefImages carries reference images for INSTRUCTION-EDIT models

@@ -167,0 +196,4 @@
+		return nil, err
+	}
+	wire := refEditRequest{txt2imgRequest: base}
+	for _, ref := range req.RefImages {