You generate the perfect edit, but the face came back… adjacent. Not quite her. Multiply by five references and a video, and the whole scene subtly belongs to someone else. This is identity drift, and Sensia is engineered around it.
What we measured
Across every past run with an input image: with references attached, Apex (Seedream 4.5) kept the input's face on roughly half of runs, while Anchor (Qwen Image) held it on about two thirds — and both were perfect with the input alone. The takeaway isn't that one model is strictly better; it's that references are a coin-flip tax on identity, per generation.
- Keep the input image attached even when the prompt already describes everything — it is the identity anchor.
- Prefer Anchor when the face matters more than reference count; prefer Apex when you need 10+ references in one run.
- Regenerate on drift instead of fighting it in the prompt — each run re-rolls the coin.
- For the strongest hold, run Preserve Identity in the optimizer once and compare it against your original prompt.
The one prompt habit
Always put identity in the Preserve field, not the instruction. 'Keep her facial features, skin tone, and proportions exactly' in Preserve tells the model what not to touch; the same phrase in Instruction makes it just another editable adjective.