From 22c0d07fac1ee242f9507f5b1f3417caa1c5a042 Mon Sep 17 00:00:00 2001
From: mindful-time <mindful.time@outlook.com>
Date: Fri, 7 Nov 2025 16:44:21 +0100
Subject: [PATCH] fix(dspy): exclude gpt-5-chat from reasoning model
 classification

The regex pattern for identifying reasoning models was incorrectly
matching gpt-5-chat, causing it to be subject to reasoning model
validation requirements and attempting to pass reasoning parameters
that Azure's API doesn't support for this model.

Updated the regex to use negative lookahead (?!-chat) to exclude
gpt-5-chat while still allowing other gpt-5 variants like gpt-5-mini,
gpt-5-nano, and gpt-5-pro to be recognized as reasoning models.

- Updated regex pattern in dspy/clients/lm.py
- Added test case for gpt-5-chat in test_reasoning_model_token_parameter
- Added dedicated test test_gpt_5_chat_not_reasoning_model

Fixes issue where gpt-5-chat (Azure AI Foundry) was incorrectly
classified as a reasoning model, preventing normal usage with
standard temperature and max_tokens values.
---
 dspy/clients/lm.py       |  8 +++++++-
 tests/clients/test_lm.py | 18 +++++++++++++++++-
 2 files changed, 24 insertions(+), 2 deletions(-)

diff --git a/dspy/clients/lm.py b/dspy/clients/lm.py
index 19085bea81..c165ceca4d 100644
--- a/dspy/clients/lm.py
+++ b/dspy/clients/lm.py
@@ -85,7 +85,13 @@ def __init__(
         model_family = model.split("/")[-1].lower() if "/" in model else model.lower()
 
         # Recognize OpenAI reasoning models (o1, o3, o4, gpt-5 family)
-        model_pattern = re.match(r"^(?:o[1345]|gpt-5)(?:-(?:mini|nano))?", model_family)
+        # Exclude non-reasoning variants like gpt-5-chat this is in azure ai foundry
+        # Allow date suffixes like -2023-01-01 after model name or mini/nano/pro
+        # For gpt-5, use negative lookahead to exclude -chat and allow other suffixes
+        model_pattern = re.match(
+            r"^(?:o[1345](?:-(?:mini|nano|pro))?(?:-\d{4}-\d{2}-\d{2})?|gpt-5(?!-chat)(?:-.*)?)$",
+            model_family,
+        )
 
         if model_pattern:
             if (temperature and temperature != 1.0) or (max_tokens and max_tokens < 16000):
diff --git a/tests/clients/test_lm.py b/tests/clients/test_lm.py
index a24c09a9d4..64e76ecd9c 100644
--- a/tests/clients/test_lm.py
+++ b/tests/clients/test_lm.py
@@ -298,6 +298,7 @@ def test_reasoning_model_token_parameter():
         ("openai/gpt-5", True),
         ("openai/gpt-5-mini", True),
         ("openai/gpt-5-nano", True),
+        ("azure/gpt-5-chat", False),  # gpt-5-chat is NOT a reasoning model
         ("openai/gpt-4", False),
         ("anthropic/claude-2", False),
     ]
@@ -318,7 +319,7 @@ def test_reasoning_model_token_parameter():
             assert lm.kwargs["max_tokens"] == 1000
 
 
-@pytest.mark.parametrize("model_name", ["openai/o1", "openai/gpt-5-nano"])
+@pytest.mark.parametrize("model_name", ["openai/o1", "openai/gpt-5-nano", "openai/gpt-5-mini"])
 def test_reasoning_model_requirements(model_name):
     # Should raise assertion error if temperature or max_tokens requirements not met
     with pytest.raises(
@@ -347,6 +348,21 @@ def test_reasoning_model_requirements(model_name):
     assert lm.kwargs["max_completion_tokens"] is None
 
 
+def test_gpt_5_chat_not_reasoning_model():
+    """Test that gpt-5-chat is NOT treated as a reasoning model."""
+    # Should NOT raise validation error - gpt-5-chat is not a reasoning model
+    lm = dspy.LM(
+        model="openai/gpt-5-chat",
+        temperature=0.7,  # Can be any value
+        max_tokens=1000,  # Can be any value
+    )
+    # Should use max_tokens, not max_completion_tokens
+    assert "max_completion_tokens" not in lm.kwargs
+    assert "max_tokens" in lm.kwargs
+    assert lm.kwargs["max_tokens"] == 1000
+    assert lm.kwargs["temperature"] == 0.7
+
+
 def test_dump_state():
     lm = dspy.LM(
         model="openai/gpt-4o-mini",