feat: gpt-5-chat support (#20774)

* added gpt-5-chat support

* uv lock

* updated

* updated tests

* updatec context window

Author: jasiecky

llama-index-integrations/llms/llama-index-llms-openai/llama_index/llms/openai/utils.py

@@ -59,6 +59,7 @@
     # gpt-5 is a reasoning model, putting it in the o models list
     "gpt-5": 400000,
     "gpt-5-2025-08-07": 400000,
+    "gpt-5-chat": 128000,
     "gpt-5-mini": 400000,
     "gpt-5-mini-2025-08-07": 400000,
     "gpt-5-nano": 400000,

llama-index-integrations/llms/llama-index-llms-openai/pyproject.toml

@@ -27,7 +27,7 @@ dev = [
 
 [project]
 name = "llama-index-llms-openai"
-version = "0.6.19"
+version = "0.6.20"
 description = "llama-index llms openai integration"
 authors = [{name = "llama-index"}]
 requires-python = ">=3.9,<4.0"

llama-index-integrations/llms/llama-index-llms-openai/tests/test_openai_utils.py

@@ -477,3 +477,27 @@ def test_gpt_5_chat_latest_model_support() -> None:
 def test_is_chatcomp_api_supported() -> None:
     assert is_chatcomp_api_supported("gpt-5.2")
     assert not is_chatcomp_api_supported("gpt-5.2-pro")
+
+
+def test_gpt_5_chat_model_support() -> None:
+    """Test that gpt-5-chat is properly supported."""
+    model_name = "gpt-5-chat"
+
+    assert model_name in ALL_AVAILABLE_MODELS, (
+        f"{model_name} should be in ALL_AVAILABLE_MODELS"
+    )
+
+    assert is_chat_model(model_name) is True, (
+        f"{model_name} should be recognized as a chat model"
+    )
+
+    assert is_function_calling_model(model_name) is True, (
+        f"{model_name} should support function calling"
+    )
+
+    context_size = openai_modelname_to_contextsize(model_name)
+    assert context_size == 128000, (
+        f"{model_name} should have 128000 tokens context, got {context_size}"
+    )
+
+    assert model_name in CHAT_MODELS, f"{model_name} should be in CHAT_MODELS"