[Models] Step-3.5-Flash (#33523)

Signed-off-by: Jee Jee Li <pandaleefree@gmail.com>
Co-authored-by: i-zhangmingming <i-zhangmingming@stepfun.com>
Co-authored-by: xiewuxun <xiewuxun@stepfun.com>
Co-authored-by: zetaohong <i-hongzetao@stepfun.com>
Co-authored-by: Jee Jee Li <pandaleefree@gmail.com>
(cherry picked from commit c3b40dc3e7)

tests/models/registry.py

@@ -480,6 +480,9 @@ _TEXT_GENERATION_EXAMPLE_MODELS = {
     "Step1ForCausalLM": _HfExamplesInfo(
         "stepfun-ai/Step-Audio-EditX", trust_remote_code=True
     ),
+    "Step3p5ForCausalLM": _HfExamplesInfo(
+        "stepfun-ai/step-3.5-flash", is_available_online=False
+    ),
     "SmolLM3ForCausalLM": _HfExamplesInfo("HuggingFaceTB/SmolLM3-3B"),
     "StableLMEpochForCausalLM": _HfExamplesInfo("stabilityai/stablelm-zephyr-3b"),
     "StableLmForCausalLM": _HfExamplesInfo("stabilityai/stablelm-3b-4e1t"),
@@ -1081,6 +1084,12 @@ _SPECULATIVE_DECODING_EXAMPLE_MODELS = {
     "Qwen3NextMTP": _HfExamplesInfo(
         "Qwen/Qwen3-Next-80B-A3B-Instruct", min_transformers_version="4.56.3"
     ),
+    "Step3p5MTP": _HfExamplesInfo(
+        "stepfun-ai/Step-3.5-Flash",
+        trust_remote_code=True,
+        speculative_model="stepfun-ai/Step-3.5-Flash",
+        is_available_online=False,
+    ),
 }
 
 _TRANSFORMERS_BACKEND_MODELS = {