gpt-image-2.6-sunburst / gpt-image-2.6-flare: background: "transparent" with output_format: "jpeg" is the only combination that returns 400. png / webp give full alpha, gif on 2.6 gives 1-bit transparency, and svg only writes a full-canvas white background with opaque. The page includes the measured 5 × 3 matrix.
Another easy mistake is auto: it is not fixed to opaque and follows the prompt; pass transparent or opaque explicitly for deterministic output.
📖 Read the output format and background FAQ
← Back to live updates · 📚 Monthly archive