Add support for new GPT-5 model variants

- Renamed existing GPT-5 variants for consistency (`nano` → `minimal`, `mini` → `low`, etc.).
- Added metadata definitions for new variants: `gpt-5-minimal`, `gpt-5-low`, `gpt-5-medium`, and updated logic to reflect variant-specific reasoning efforts.

internal/client/codex_client.go

@@ -93,8 +93,9 @@ func (c *CodexClient) Provider() string {
 func (c *CodexClient) CanProvideModel(modelName string) bool {
 	models := []string{
 		"gpt-5",
-		"gpt-5-mini",
+		"gpt-5-minimal",
-		"gpt-5-nano",
+		"gpt-5-low",
+		"gpt-5-medium",
 		"gpt-5-high",
 		"codex-mini-latest",
 	}
@@ -344,14 +345,14 @@ func (c *CodexClient) APIRequest(ctx context.Context, modelName, endpoint string
 	// Stream must be set to true
 	jsonBody, _ = sjson.SetBytes(jsonBody, "stream", true)
 
-	if util.InArray([]string{"gpt-5-nano", "gpt-5-mini", "gpt-5", "gpt-5-high"}, modelName) {
+	if util.InArray([]string{"gpt-5-minimal", "gpt-5-low", "gpt-5-medium", "gpt-5-high"}, modelName) {
 		jsonBody, _ = sjson.SetBytes(jsonBody, "model", "gpt-5")
 		switch modelName {
-		case "gpt-5-nano":
+		case "gpt-5-minimal":
 			jsonBody, _ = sjson.SetBytes(jsonBody, "reasoning.effort", "minimal")
-		case "gpt-5-mini":
+		case "gpt-5-low":
 			jsonBody, _ = sjson.SetBytes(jsonBody, "reasoning.effort", "low")
-		case "gpt-5":
+		case "gpt-5-medium":
 			jsonBody, _ = sjson.SetBytes(jsonBody, "reasoning.effort", "medium")
 		case "gpt-5-high":
 			jsonBody, _ = sjson.SetBytes(jsonBody, "reasoning.effort", "high")

internal/registry/model_definitions.go

@@ -149,6 +149,58 @@ func GetOpenAIModels() []*ModelInfo {
 			MaxCompletionTokens: 128000,
 			SupportedParameters: []string{"tools"},
 		},
+		{
+			ID:                  "gpt-5-minimal",
+			Object:              "model",
+			Created:             time.Now().Unix(),
+			OwnedBy:             "openai",
+			Type:                "openai",
+			Version:             "gpt-5-2025-08-07",
+			DisplayName:         "GPT 5 Minimal",
+			Description:         "Stable version of GPT 5, The best model for coding and agentic tasks across domains.",
+			ContextLength:       400000,
+			MaxCompletionTokens: 128000,
+			SupportedParameters: []string{"tools"},
+		},
+		{
+			ID:                  "gpt-5-low",
+			Object:              "model",
+			Created:             time.Now().Unix(),
+			OwnedBy:             "openai",
+			Type:                "openai",
+			Version:             "gpt-5-2025-08-07",
+			DisplayName:         "GPT 5 Low",
+			Description:         "Stable version of GPT 5, The best model for coding and agentic tasks across domains.",
+			ContextLength:       400000,
+			MaxCompletionTokens: 128000,
+			SupportedParameters: []string{"tools"},
+		},
+		{
+			ID:                  "gpt-5-medium",
+			Object:              "model",
+			Created:             time.Now().Unix(),
+			OwnedBy:             "openai",
+			Type:                "openai",
+			Version:             "gpt-5-2025-08-07",
+			DisplayName:         "GPT 5 Medium",
+			Description:         "Stable version of GPT 5, The best model for coding and agentic tasks across domains.",
+			ContextLength:       400000,
+			MaxCompletionTokens: 128000,
+			SupportedParameters: []string{"tools"},
+		},
+		{
+			ID:                  "gpt-5-high",
+			Object:              "model",
+			Created:             time.Now().Unix(),
+			OwnedBy:             "openai",
+			Type:                "openai",
+			Version:             "gpt-5-2025-08-07",
+			DisplayName:         "GPT 5 High",
+			Description:         "Stable version of GPT 5, The best model for coding and agentic tasks across domains.",
+			ContextLength:       400000,
+			MaxCompletionTokens: 128000,
+			SupportedParameters: []string{"tools"},
+		},
 		{
 			ID:                  "codex-mini-latest",
 			Object:              "model",