How Do I Access Seedream 4.0 / 4.5 via API?

Overview

Access Seedream v4 or v4.5 through WaveSpeedAI, not through a version-agnostic endpoint. Create a WaveSpeedAI key, then POST prompt-based JSON to /api/v3/bytedance/seedream-v4 or /api/v3/bytedance/seedream-v4.5 with the bearer key. Save the returned prediction ID and fetch the result. These are separate route paths, so choose the version before building the request.

For a first call, keep the key server-side, supply a prompt and a supported size according to the selected route’s schema, then inspect the returned output and task status. Both current pages show this basic text-to-image request shape; an editing flow or image reference needs its own documented route and upload permission check. Keep the prediction ID in your application job record. Do not copy optional fields from one version into the other without checking its live schema.

Test the two versions on the same approved brief only when they accept comparable inputs. Evaluate typography, subject preservation, composition and the number of attempts before approval. Record the exact route ID and current price quote in your deployment notes; access and charges can change independently of this conceptual workflow.

For a first build, implement one version end to end. Add the other only if it solves a measured quality or workflow need, not because its version number is newer.

Keep separate request fixtures for v4 and v4.5 even when their first examples look alike. Validate each fixture against its own live page and record a sample response, making version-specific schema differences easier to catch before production traffic depends on them.

Source: WaveSpeedAI Seedream v4 route; WaveSpeedAI Seedream v4.5 route; WaveSpeedAI API quickstart. Source check: 2026-09-29.