HF RL Explorer

Feature: Add GPT‑5.5 as a premium gated model

Feature: Add GPT‑5.5 as a premium gated model: a task in LegoFlow-SWE (Harbor dataset). Issue 192 asks us to add the model openai/gpt-5.5 to the available model list and apply the same premium gating that Bedrock Claude already has.

The task

Issue #192 asks us to add the model `openai/gpt-5.5` to the available model list and apply the **same** premium gating that Bedrock Claude already has.

Part of Lego-X/LegoFlow-SWE.