diff --git a/conf/openai_models.json b/conf/openai_models.json
index 848fb96..2f47aa2 100644
--- a/conf/openai_models.json
+++ b/conf/openai_models.json
@@ -232,6 +232,81 @@
       "supports_temperature": true,
       "max_image_size_mb": 20.0,
       "use_openai_response_api": true
+    },
+    {
+      "model_name": "gpt-5.1",
+      "friendly_name": "OpenAI (GPT-5.1)",
+      "aliases": [
+        "gpt5.1",
+        "gpt-5.1",
+        "5.1"
+      ],
+      "intelligence_score": 18,
+      "description": "GPT-5.1 (400K context, 128K output) - Flagship reasoning model with configurable thinking effort and vision support.",
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_system_prompts": true,
+      "supports_streaming": true,
+      "supports_function_calling": true,
+      "supports_json_mode": true,
+      "supports_images": true,
+      "supports_temperature": true,
+      "max_image_size_mb": 20.0,
+      "default_reasoning_effort": "medium",
+      "allow_code_generation": true,
+      "temperature_constraint": "fixed"
+    },
+    {
+      "model_name": "gpt-5.1-codex",
+      "friendly_name": "OpenAI (GPT-5.1 Codex)",
+      "aliases": [
+        "gpt5.1-codex",
+        "gpt-5.1-codex",
+        "gpt5.1code",
+        "gpt-5.1-code",
+        "codex-5.1"
+      ],
+      "intelligence_score": 19,
+      "description": "GPT-5.1 Codex (400K context, 128K output) - Agentic coding specialization available through the Responses API.",
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_system_prompts": true,
+      "supports_streaming": false,
+      "supports_function_calling": true,
+      "supports_json_mode": true,
+      "supports_images": true,
+      "supports_temperature": true,
+      "max_image_size_mb": 20.0,
+      "use_openai_response_api": true,
+      "default_reasoning_effort": "high",
+      "allow_code_generation": true,
+      "temperature_constraint": "fixed"
+    },
+    {
+      "model_name": "gpt-5.1-codex-mini",
+      "friendly_name": "OpenAI (GPT-5.1 Codex mini)",
+      "aliases": [
+        "gpt5.1-codex-mini",
+        "gpt-5.1-codex-mini",
+        "codex-mini",
+        "5.1-codex-mini"
+      ],
+      "intelligence_score": 16,
+      "description": "GPT-5.1 Codex mini (400K context, 128K output) - Cost-efficient Codex variant with streaming support.",
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_system_prompts": true,
+      "supports_streaming": true,
+      "supports_function_calling": true,
+      "supports_json_mode": true,
+      "supports_images": true,
+      "supports_temperature": true,
+      "max_image_size_mb": 20.0,
+      "allow_code_generation": true,
+      "temperature_constraint": "fixed"
     }
   ]
 }
diff --git a/conf/openrouter_models.json b/conf/openrouter_models.json
index aaa1d66..0d7f33e 100644
--- a/conf/openrouter_models.json
+++ b/conf/openrouter_models.json
@@ -366,6 +366,72 @@
       "description": "GPT-5 nano (400K context, 128K output) - Fastest, cheapest version of GPT-5 for summarization and classification tasks",
       "intelligence_score": 8
     },
+    {
+      "model_name": "openai/gpt-5.1",
+      "aliases": [
+        "gpt5.1",
+        "gpt-5.1",
+        "5.1"
+      ],
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_json_mode": true,
+      "supports_function_calling": true,
+      "supports_images": true,
+      "max_image_size_mb": 20.0,
+      "supports_temperature": true,
+      "temperature_constraint": "fixed",
+      "default_reasoning_effort": "medium",
+      "allow_code_generation": true,
+      "description": "GPT-5.1 (400K context, 128K output) - Flagship reasoning model with configurable thinking effort and vision support",
+      "intelligence_score": 18
+    },
+    {
+      "model_name": "openai/gpt-5.1-codex",
+      "aliases": [
+        "gpt5.1-codex",
+        "gpt-5.1-codex",
+        "gpt5.1code",
+        "gpt-5.1-code",
+        "codex-5.1"
+      ],
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_json_mode": true,
+      "supports_function_calling": true,
+      "supports_images": true,
+      "max_image_size_mb": 20.0,
+      "supports_temperature": true,
+      "temperature_constraint": "fixed",
+      "use_openai_response_api": true,
+      "default_reasoning_effort": "high",
+      "allow_code_generation": true,
+      "description": "GPT-5.1 Codex (400K context, 128K output) - Agentic coding specialization available through the Responses API",
+      "intelligence_score": 19
+    },
+    {
+      "model_name": "openai/gpt-5.1-codex-mini",
+      "aliases": [
+        "gpt5.1-codex-mini",
+        "gpt-5.1-codex-mini",
+        "codex-mini",
+        "5.1-codex-mini"
+      ],
+      "context_window": 400000,
+      "max_output_tokens": 128000,
+      "supports_extended_thinking": true,
+      "supports_json_mode": true,
+      "supports_function_calling": true,
+      "supports_images": true,
+      "max_image_size_mb": 20.0,
+      "supports_temperature": true,
+      "temperature_constraint": "fixed",
+      "allow_code_generation": true,
+      "description": "GPT-5.1 Codex mini (400K context, 128K output) - Cost-efficient Codex variant with streaming support",
+      "intelligence_score": 16
+    },
     {
       "model_name": "x-ai/grok-4",
       "aliases": [
diff --git a/providers/openai.py b/providers/openai.py
index f7e61f4..7acb19c 100644
--- a/providers/openai.py
+++ b/providers/openai.py
@@ -115,20 +115,51 @@ class OpenAIModelProvider(RegistryBackedProviderMixin, OpenAICompatibleProvider)
 
         if category == ToolModelCategory.EXTENDED_REASONING:
             # Prefer models with extended thinking support
-            # GPT-5-Codex first for coding tasks
-            preferred = find_first(["gpt-5-codex", "gpt-5-pro", "o3", "o3-pro", "gpt-5"])
+            # GPT-5.1 Codex first for coding tasks
+            preferred = find_first(
+                [
+                    "gpt-5.1-codex",
+                    "gpt-5.1",
+                    "gpt-5-codex",
+                    "gpt-5-pro",
+                    "o3-pro",
+                    "gpt-5",
+                    "o3",
+                ]
+            )
             return preferred if preferred else allowed_models[0]
 
         elif category == ToolModelCategory.FAST_RESPONSE:
             # Prefer fast, cost-efficient models
-            # GPT-5 models for speed, GPT-5-Codex after (premium pricing but cached)
-            preferred = find_first(["gpt-5", "gpt-5-mini", "gpt-5-codex", "o4-mini", "o3-mini"])
+            # GPT-5.1 models for speed, GPT-5.1-Codex after (premium pricing but cached)
+            preferred = find_first(
+                [
+                    "gpt-5.1",
+                    "gpt-5.1-codex-mini",
+                    "gpt-5",
+                    "gpt-5-mini",
+                    "gpt-5-codex",
+                    "o4-mini",
+                    "o3-mini",
+                ]
+            )
             return preferred if preferred else allowed_models[0]
 
         else:  # BALANCED or default
             # Prefer balanced performance/cost models
-            # Include GPT-5-Codex for coding workflows
-            preferred = find_first(["gpt-5", "gpt-5-codex", "gpt-5-pro", "gpt-5-mini", "o4-mini", "o3-mini"])
+            # Include GPT-5.1 family for latest capabilities
+            preferred = find_first(
+                [
+                    "gpt-5.1",
+                    "gpt-5.1-codex",
+                    "gpt-5",
+                    "gpt-5-codex",
+                    "gpt-5-pro",
+                    "gpt-5-mini",
+                    "o4-mini",
+                    "o3-mini",
+                ]
+            )
             return preferred if preferred else allowed_models[0]