{
  "date": "2026-10-01",
  "method": "Each model received the same start image and the same eight edit prompts in order, each edit applied to that model's previous output. One run per chain, first result at every step, no retouching. Identical = share of all pixels whose colour moved less than CIE76 dE 2 versus the previous step. Control = SSIM and mean dE of regions no edit touches, start versus after edit 8. Outputs at a different size were resized to the start image (a resize round trip alone keeps 97-99% identical). Two scenes; not a statistical benchmark.",
  "settings": {
    "ideogram-4.5": {
      "endpoint": "ideogram/v4.5/edit",
      "edit_precision": "high",
      "quality": "medium"
    },
    "gpt-image-2.5-sunburst": {
      "endpoint": "openai/gpt-image-2.5/sunburst/edit",
      "quality": "medium"
    },
    "nano-banana-pro": {
      "endpoint": "fal-ai/nano-banana-pro/edit",
      "resolution": "1K"
    },
    "seedream-5-pro": {
      "endpoint": "bytedance/seedream/v5/pro/edit",
      "image_size": "default (auto_2K)"
    }
  },
  "drift_scenes": [
    {
      "id": "cafe",
      "start_model": "fal-ai/gpt-image-2",
      "start_settings": {
        "image_size": "square_hd",
        "quality": "high"
      },
      "start_prompt": "Natural editorial photograph of a fictional Scandinavian woman in her late twenties with a short blonde bob and light freckles, wearing a mustard yellow cable-knit sweater, sitting at a light oak table by a large window in a bright Stockholm café, looking slightly off camera with a calm smile. On the table: a plain white ceramic mug and a small potted green plant. Behind her on the white wall hangs a framed abstract print with blue and terracotta shapes. Soft overcast daylight, 50mm lens, eye level, realistic skin texture, no text anywhere in the image.",
      "edits": [
        "Add round tortoiseshell glasses to her face. Change nothing else.",
        "Change her sweater color from mustard yellow to forest green. Keep the knit pattern. Change nothing else.",
        "Put a croissant on a small white plate on the table next to the mug. Change nothing else.",
        "Replace the potted plant with a small glass vase of yellow tulips. Change nothing else.",
        "Print the word HEJ in black capital letters on the front of the mug. Change nothing else.",
        "Add a small grey cat sitting on the empty chair beside her. Change nothing else.",
        "Add a thin silver watch on her left wrist. Change nothing else.",
        "Change her hair color to auburn. Keep the same haircut. Change nothing else."
      ],
      "results": {
        "ideogram-4.5": {
          "identical_pct_per_step": [
            98.1,
            77.0,
            96.0,
            92.8,
            99.2,
            96.6,
            99.4,
            94.4
          ],
          "median_identical_pct": 96.3,
          "control_ssim_after_chain": 1.0,
          "control_delta_e_after_chain": 0.02
        },
        "gpt-image-2.5-sunburst": {
          "identical_pct_per_step": [
            49.8,
            58.2,
            72.7,
            70.3,
            78.1,
            78.1,
            81.9,
            77.1
          ],
          "median_identical_pct": 74.9,
          "control_ssim_after_chain": 0.827,
          "control_delta_e_after_chain": 5.65
        },
        "nano-banana-pro": {
          "identical_pct_per_step": [
            45.8,
            54.7,
            63.5,
            62.8,
            66.5,
            65.7,
            49.8,
            54.3
          ],
          "median_identical_pct": 58.75,
          "control_ssim_after_chain": 0.839,
          "control_delta_e_after_chain": 7.92
        },
        "seedream-5-pro": {
          "identical_pct_per_step": [
            33.2,
            29.8,
            48.7,
            39.1,
            47.0,
            19.1,
            38.7,
            23.3
          ],
          "median_identical_pct": 35.95,
          "control_ssim_after_chain": 0.654,
          "control_delta_e_after_chain": 18.36
        }
      }
    },
    {
      "id": "poster",
      "start_model": "fal-ai/gpt-image-2",
      "start_settings": {
        "image_size": "portrait_4_3",
        "quality": "high"
      },
      "start_prompt": "Clean minimal print advertisement poster for a fictional coffee roaster. Off-white background. At the top, a large bold black sans-serif headline reading \"MORNING RITUAL\". Below it, a smaller line reading \"Single-origin, roasted in Göteborg\". In the center, a kraft paper coffee bag standing upright, photographed with soft studio light and a gentle shadow, with a small label on the bag reading \"FJÄLLBACKA ROASTERS\". At the lower right, a round black price badge reading \"129 kr\". At the bottom center, small footer text reading \"fjallbacka-roasters.se\". Generous margins, Scandinavian graphic design, sharp text.",
      "edits": [
        "Change the headline text to \"EVENING RITUAL\". Keep the same font, size and position. Change nothing else.",
        "Change the price in the badge to \"99 kr\". Change nothing else.",
        "Change the coffee bag color from kraft brown to matte black. Keep the label and its text. Change nothing else.",
        "Add a small white espresso cup on a saucer to the left of the bag. Change nothing else.",
        "Change the smaller line under the headline to \"Från en gård, rostat i Göteborg\". Keep the same font and size. Change nothing else.",
        "Add a small red circular sticker reading \"NYHET\" in the top right corner. Change nothing else.",
        "Change the footer text to \"fjallbacka.se\". Change nothing else.",
        "Add three roasted coffee beans on the surface in front of the bag. Change nothing else."
      ],
      "results": {
        "ideogram-4.5": {
          "identical_pct_per_step": [
            91.8,
            99.4,
            75.7,
            97.7,
            98.9,
            98.9,
            99.7,
            98.8
          ],
          "median_identical_pct": 98.85,
          "control_ssim_after_chain": 1.0,
          "control_delta_e_after_chain": 0.02
        },
        "gpt-image-2.5-sunburst": {
          "identical_pct_per_step": [
            82.0,
            93.4,
            72.1,
            80.1,
            95.0,
            94.0,
            93.8,
            94.9
          ],
          "median_identical_pct": 93.6,
          "control_ssim_after_chain": 0.988,
          "control_delta_e_after_chain": 1.95
        },
        "nano-banana-pro": {
          "identical_pct_per_step": [
            77.6,
            86.9,
            70.8,
            83.3,
            89.1,
            89.8,
            90.8,
            90.5
          ],
          "median_identical_pct": 88.0,
          "control_ssim_after_chain": 0.957,
          "control_delta_e_after_chain": 2.49
        },
        "seedream-5-pro": {
          "identical_pct_per_step": [
            69.4,
            78.3,
            69.0,
            83.0,
            74.0,
            90.2,
            88.5,
            91.7
          ],
          "median_identical_pct": 80.65,
          "control_ssim_after_chain": 0.953,
          "control_delta_e_after_chain": 4.52
        }
      }
    }
  ],
  "text_round": {
    "settings": {
      "ideogram-4.5": "ideogram/v4.5, medium, square_hd",
      "gpt-image-2.5-sunburst": "openai/gpt-image-2.5/sunburst/text-to-image, medium, square_hd",
      "nano-banana-pro": "fal-ai/nano-banana-pro, 1K, 1:1",
      "seedream-5-pro": "bytedance/seedream/v5/pro/text-to-image, square_hd"
    },
    "prompts": [
      {
        "id": "gig-poster",
        "prompt": "Swiss-style gig poster. Off-white paper. One large orange circle. Heavy black grotesk type reading \"NIGHT SHIFT\" across the top, and below it in smaller type \"14.11 — KULTURHUSET — 20:00\". Bottom line in small caps: \"Tickets 240 kr at the door\". Flat print design, sharp edges."
      },
      {
        "id": "menu-board",
        "prompt": "Photograph of a bistro chalkboard menu on a brick wall. Hand-lettered chalk text, exactly these lines: \"DAGENS LUNCH\", \"Köttbullar med potatismos — 135 kr\", \"Laxsoppa med dill — 125 kr\", \"Vegetarisk lasagne — 119 kr\", \"Kaffe & kanelbulle — 45 kr\". Warm window light."
      },
      {
        "id": "bilingual-label",
        "prompt": "Product photo of a glass jar of honey with a cream paper label. The label reads \"HONUNG / HONEY\" in a serif font, then \"Raw wildflower — Gotland\" and \"Net wt. 350 g\". Below that in Japanese: \"はちみつ\". Soft studio light on a linen surface."
      },
      {
        "id": "app-banner",
        "prompt": "Wide web banner graphic for a fictional fitness app. Dark navy background, a bold white headline \"Run your first 5K in 8 weeks\", a smaller line \"Free plan · No ads · Works offline\", and a rounded lime-green button reading \"Start today\". Clean modern UI typography, flat vector design."
      }
    ]
  }
}