SDXL image generation

SDXL is Stable Diffusion XL — the higher-resolution successor to SD1. Native resolution 1024×1024, massive community catalog, prompt style sits between SD1's Booru tags and Flux's natural language (tags still help; full sentences work too). Two invocation paths on the orchestrator:

`engine`	Best for	Notes
`sdcpp` (ecosystem `sdxl`)	Default — Stable Diffusion C++ on Civitai workers	`sampleMethod` + `schedule` sdcpp enums, textual-inversion embeddings, `uCache` mode.
`comfy` (ecosystem `sdxl`)	When you specifically need ComfyUI sampler/scheduler enums or a Comfy-only feature	`sampler` + `scheduler` Comfy enums, `denoiseStrength` (vs sdcpp's `strength`) on variants.

Default choice for new integrations: engine: "sdcpp", ecosystem: "sdxl". Reach for comfy only when you specifically need a ComfyUI-exclusive sampler (dpmpp_2m, dpmpp_sde, etc.) or scheduler (karras).

Both engines support createImage and createVariant (img2img). Neither supports editImage — use Flux 1 Kontext or Flux 2 Klein if you need prompt-driven editing.

Prerequisites

A Civitai orchestration token (Quick start → Prerequisites)
An SDXL checkpoint AIR URN — browse the Civitai SDXL catalog
For createVariant: a source image URL

sdcpp (default path)

Text-to-image

http

POST https://orchestration.civitai.com/v2/consumer/workflows?wait=60
Authorization: Bearer <your-token>
Content-Type: application/json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "sdcpp",
      "ecosystem": "sdxl",
      "operation": "createImage",
      "model": "urn:air:sdxl:checkpoint:civitai:101055@128078",
      "prompt": "masterpiece, best quality, 1girl, solo, landscape, sunset, cinematic lighting, highly detailed",
      "negativePrompt": "worst quality, low quality, blurry",
      "width": 1024,
      "height": 1024,
      "cfgScale": 7,
      "steps": 25
    }
  }]
}

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

Valid JSON

Common sdcpp-sdxl parameters:

Field	Default	Range	Notes
`model`	— ✅	AIR URN	SDXL checkpoint. See the catalog.
`prompt`	— ✅	≤ 10 000 chars	Tag-style or natural language. Quality tags (`masterpiece, best quality, …`) still help.
`negativePrompt`	(none)	≤ 10 000 chars	Recommended. `worst quality, low quality, blurry` is a solid starting point.
`width` / `height`	`1024`	`64`–`2048`, divisible by 16	SDXL's native resolution is 1024×1024. Well-behaved aspect ratios: 1024×1024, 1152×896, 896×1152, 1216×832, 832×1216, 1344×768, 768×1344, 1536×640, 640×1536.
`cfgScale`	`7`	`0`–`30`	`6`–`8` works for most SDXL checkpoints; LCM/Turbo variants want `1`–`2`.
`steps`	`20`	`1`–`150`	`20`–`30` typical. LCM/Turbo checkpoints need fewer (`4`–`8`).
`sampleMethod`	`euler`	enum	`SdCppSampleMethod`.
`schedule`	`discrete`	enum	`SdCppSchedule`.
`vaeModel`	(checkpoint VAE)	AIR URN	Override baked-in VAE. Rarely needed.
`loras`	`{}`	`{ airUrn: strength }`	Stack multiple; `0.6`–`1.0` strengths typical.
`embeddings`	`[]`	array of AIR URNs	Textual inversions. Reference them in the prompt / negative prompt by their embedding name.
`quantity`	`1`	`1`–`12`	Number of images per call.
`seed`	random	int64	Pin for reproducibility.
`uCache`	(default)	enum	`SdCppUCacheMode`. Caching strategy; leave default unless you know you want otherwise.

No clipSkip on SDXL

Unlike SD1, SDXL doesn't expose a clipSkip parameter — the model's dual text encoders make the SD1 clip-skip convention meaningless here. Sending clipSkip on an SDXL request will 400.

Aspect-ratio variants

SDXL handles off-square aspect ratios well as long as you stay near ~1 megapixel total area. Go too wide or too tall and composition artifacts (duplicated subjects, "mirrored twin" effects) start to appear.

json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "sdcpp",
      "ecosystem": "sdxl",
      "operation": "createImage",
      "model": "urn:air:sdxl:checkpoint:civitai:101055@128078",
      "prompt": "masterpiece, best quality, wide panoramic view of a futuristic city at dusk",
      "negativePrompt": "worst quality, low quality",
      "width": 1536,
      "height": 640,
      "cfgScale": 7,
      "steps": 25
    }
  }]
}

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

Valid JSON

With LoRAs

json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "sdcpp",
      "ecosystem": "sdxl",
      "operation": "createImage",
      "model": "urn:air:sdxl:checkpoint:civitai:101055@128078",
      "prompt": "masterpiece, best quality, portrait of a warrior in ornate armor",
      "negativePrompt": "worst quality, low quality, blurry",
      "width": 1024,
      "height": 1024,
      "cfgScale": 7,
      "steps": 25,
      "loras": {
        "urn:air:sdxl:lora:civitai:123456@789012": 0.8
      }
    }
  }]
}

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

Valid JSON

Image-to-image (`createVariant`)

json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "sdcpp",
      "ecosystem": "sdxl",
      "operation": "createVariant",
      "model": "urn:air:sdxl:checkpoint:civitai:101055@128078",
      "prompt": "masterpiece, best quality, daytime with clear blue sky",
      "negativePrompt": "worst quality, low quality",
      "width": 1024,
      "height": 1024,
      "cfgScale": 7,
      "steps": 25,
      "image": "https://image.civitai.com/.../source.jpeg",
      "strength": 0.7
    }
  }]
}

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

Valid JSON

strength controls how much of the source to preserve — 0.0 returns the source unchanged, 1.0 discards it entirely. 0.6–0.8 is the sweet spot for "keep composition, change style". Note image is a plain string URL (not a { url: ... } wrapper), and the field is strength (not denoiseStrength like on Comfy).

Comfy (alternative path)

Use engine: "comfy" when you need a ComfyUI-specific sampler — dpmpp_2m paired with the karras scheduler is a popular combo on SDXL for smoother detail:

json

{
  "steps": [{
    "$type": "imageGen",
    "input": {
      "engine": "comfy",
      "ecosystem": "sdxl",
      "operation": "createImage",
      "model": "urn:air:sdxl:checkpoint:civitai:101055@128078",
      "prompt": "masterpiece, best quality, 1girl, solo, landscape, sunset, cinematic lighting",
      "negativePrompt": "worst quality, low quality, blurry",
      "width": 1024,
      "height": 1024,
      "steps": 30,
      "cfgScale": 7,
      "sampler": "dpmpp_2m",
      "scheduler": "karras"
    }
  }]
}

Set your Civitai API token via the Token button in the navbar to enable Try It.

Request body — edit to customize (e.g. swap the image URL or prompt)

Valid JSON

Key differences from sdcpp:

Field	sdcpp	comfy
Sampler	`sampleMethod` (`SdCppSampleMethod`)	`sampler` (`ComfySampler`)
Schedule	`schedule` (`SdCppSchedule`)	`scheduler` (`ComfyScheduler`)
Img2img strength	`strength` (default `0.7`)	`denoiseStrength` (default `0.75`)
Default `steps`	`20`	`30`
`embeddings` array	✅	—
`uCache`	✅	—

Comfy also supports createVariant with image (plain string URL) + denoiseStrength; see the ComfySdxlVariantImageGenInput schema.

Reading the result

Both engines emit the standard imageGen output — an images[] array, one entry per quantity:

json

{
  "status": "succeeded",
  "steps": [{
    "name": "0",
    "$type": "imageGen",
    "status": "succeeded",
    "output": {
      "images": [
        { "id": "blob_...", "url": "https://.../signed.jpeg" }
      ]
    }
  }]
}

Blob URLs are signed and expire — refetch the workflow or call GetBlob for a fresh URL.

Runtime

SDXL at 1024×1024 typically finishes in 10–25 s (sdcpp) or 15–35 s (comfy). wait=60 works comfortably for quantity ≤ 2. LCM/Turbo checkpoints at steps: 4–8 finish in 3–8 s and support higher quantity inside the same window. For larger batches or atypical aspect ratios, submit with wait=0 and poll.

Cost

Billed in Buzz on the workflow's transactions. Use whatif=true for an exact preview; see Payments (Buzz) for currency selection.

Both engines use the same per-pixel / per-step shape — different reference values:

total = base × (width × height / referencePixels) × (steps / referenceSteps) × quantity

Path	`base`	`referencePixels`	`referenceSteps`	Defaults → Buzz
`sdcpp + sdxl`	`8`	1024²	`20`	1024²/`steps: 20`/`q: 1` → ~8 Buzz
`comfy + sdxl`	`8`	1024²	`30`	1024²/`steps: 30`/`q: 1` → ~8 Buzz

Examples:

1024² at quantity: 4 → ~32 Buzz
1344×768 at steps: 25 → ~8 × 0.98 × 1.25 ≈ ~10 Buzz (sdcpp)
1024² at steps: 35 → ~14 Buzz (sdcpp)
1536×640 at steps: 25 → ~8 × 0.94 × 1.25 ≈ ~9 Buzz (sdcpp)

Atypical aspect ratios still bill by total pixel area, so a 2:1 panorama at the same megapixel count costs the same as a 1:1 image at 1024².

Troubleshooting

Symptom	Likely cause	Fix
`400` with "model must match AIR pattern"	Passed a bare model ID or version slug	Use a full AIR URN: `urn:air:sdxl:checkpoint:civitai:<modelId>@<versionId>`.
`400` with "clipSkip is not a valid property" on SDXL	`clipSkip` doesn't exist on SDXL (it's an SD1 knob)	Remove the field. SDXL uses dual text encoders; there's nothing to skip.
`400` with unknown property	Field not valid for this engine (e.g. `sampler` on sdcpp, `sampleMethod` on comfy, `denoiseStrength` on sdcpp)	Match the schema for your chosen engine — see the difference table above.
Output has duplicated subjects / mirrored-twin composition	Aspect ratio too far from 1:1 at fixed megapixel count	Stick to well-behaved SDXL ratios: 1024², 1152×896, 1344×768, 1536×640, and mirrors thereof.
Turbo/LCM checkpoint produces mush	`cfgScale` / `steps` tuned for base SDXL	Turbo/LCM want `cfgScale: 1`–`2` and `steps: 4`–`8`.
LoRA has no visible effect	Wrong AIR URN, model private / not published, or ecosystem mismatch	Verify the URN on the LoRA's Civitai page; only SDXL-tagged LoRAs work on the `sdxl` ecosystem.
Request timed out (`wait` expired)	Large `quantity`, atypical dimensions, busy worker	Resubmit with `wait=0` and poll.
Step `failed`, `reason = "blocked"`	Prompt hit content moderation	Don't retry the same input — see Errors & retries → Step-level failures.

SubmitWorkflow — operation used by every example here
GetWorkflow — for polling
SD1 image generation — the 512×512 predecessor with the same two-engine pattern
Flux 2 / Flux 1 image generation — newer families with stronger prompt adherence
Image upscaling — chain after imageGen for higher-res output
Prompt enhancement — LLM-rewrite a prompt before feeding it in via $ref (use ecosystem: "sdxl" on the enhancer)
Full parameter catalog: the SdxlCreateImageGenInput / SdxlVariantImageGenInput / ComfySdxlCreateImageGenInput / ComfySdxlVariantImageGenInput schemas in the API reference
imageGen endpoint OpenAPI spec — standalone OpenAPI 3.1 YAML covering the full imageGen surface; import into Postman / OpenAPI Generator

SDXL image generation ​

Prerequisites ​

sdcpp (default path) ​

Text-to-image ​

Aspect-ratio variants ​

With LoRAs ​

Image-to-image (createVariant) ​

Comfy (alternative path) ​

Reading the result ​

Runtime ​

Cost ​

Troubleshooting ​

Related ​

SDXL image generation

Prerequisites

sdcpp (default path)

Text-to-image

Aspect-ratio variants

With LoRAs

Image-to-image (`createVariant`)

Comfy (alternative path)

Reading the result

Runtime

Cost

Troubleshooting

Related