Sourceful: Riverflow V2.5 Fast (free)

Riverflow V2.5 Fast is the speed-optimized variant of Sourceful's Riverflow 2.5 lineup, best for production deployments and latency-critical workflows.

The Riverflow 2.5 series is a unified text-to-image and image-to-image family that treats generation as a production workflow, using an integrated reasoning model to plan multi-step edits and judge candidates before accepting a result. Reasoning effort is controllable via the reasoning parameter (low/medium/high) - higher levels do more editing passes and apply a stricter internal judge, while lower levels return faster for early exploration. It generates at 1K and 2K resolution (no 4K) and accepts up to 4 input images for editing.

Pricing is dynamic: cost is finalized per job at completion based on billable processing, so it scales with reasoning effort, resolution, and editing complexity rather than a fixed per-image rate.

Additional features (via image_config):

• Custom font rendering via font_inputs (max 2) to match brand lettering, spacing, and weight
• Custom scoring via scoring_prompt and scoring_rubric, so the reasoning model evaluates and steers each candidate against the criteria you care about
• Background control via background_mode (original, transparent, solid) and background_hex_color

See the image generation docs for details: https://openrouter.ai/docs/features/multimodal/image-generation(opens in new tab)

Note: Sourceful imposes a 4.5MB request size limit, therefore it is highly recommended to pass image URLs instead of Base64 data.