GPT-5.6 Luna Image Output Triggers 500 Error

idoco · reddit · 2026-07-15

While using the computer use capabilities of the GPT-5.6 Luna API, a user encountered random HTTP 500 errors.

The post details a specific reproduction path: when returning inputimage within functioncalloutput, all 6 Luna runs failed. However, switching the model to Terra resulted in an 8/8 success rate for the exact same flow, with 40/40 requests functioning normally. The author further confirmed that removing the "return image" function allowed Luna to work again, making it look like a specific bug related to image-returning function output rather than general API instability.

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