NanoBanana / Firefly cannot generate images in 21:9 ultrawide format — is this a bug or a limitation

Hello!
I’ve been testing NanoBanana / Adobe Firefly for cinematic image generation, and I noticed an issue related to aspect ratios.

Whenever I request an ultrawide 21:9 (2.39:1) format, Firefly always outputs the image in 16:9, even if I explicitly specify the exact aspect ratio or provide a 21:9 storyboard as a reference.

I have tried:

• “strict 21:9” prompts

• specifying exact pixel resolutions (e.g., 2560×1100, 3440×1440)

• uploading a 21:9 storyboard and asking Firefly to preserve the frame

• canvas expansion prompts

• “do not crop / do not convert to 16:9” instructions

In every case, the model still generates an image in 16:9.

My question is:
Is Firefly currently unable to render true 21:9 ultrawide images due to model constraints, or is this behavior a bug?
If it’s a limitation, is native 21:9 support planned for future updates?

Ultrawide formats are essential for cinematic workflows, so any clarification would be greatly appreciated.
Thank you!