diff --git a/internal/registry/model_definitions.go b/internal/registry/model_definitions.go
index 8bab7710..898af75d 100644
--- a/internal/registry/model_definitions.go
+++ b/internal/registry/model_definitions.go
@@ -593,8 +593,9 @@ func GetGitHubCopilotModels() []*ModelInfo {
 			Type:                "github-copilot",
 			DisplayName:         "Gemini 3.1 Pro (Preview)",
 			Description:         "Google Gemini 3.1 Pro Preview via GitHub Copilot",
-			ContextLength:       1048576,
+			ContextLength:       173000,
 			MaxCompletionTokens: 65536,
+			SupportedEndpoints:  []string{"/chat/completions"},
 		},
 		{
 			ID:                  "gemini-3-flash-preview",
@@ -604,7 +605,7 @@ func GetGitHubCopilotModels() []*ModelInfo {
 			Type:                "github-copilot",
 			DisplayName:         "Gemini 3 Flash (Preview)",
 			Description:         "Google Gemini 3 Flash Preview via GitHub Copilot",
-			ContextLength:       1048576,
+			ContextLength:       173000,
 			MaxCompletionTokens: 65536,
 			SupportedEndpoints:  []string{"/chat/completions"},
 		},
diff --git a/internal/registry/model_definitions_test.go b/internal/registry/model_definitions_test.go
index f38b9ce4..9bf6d416 100644
--- a/internal/registry/model_definitions_test.go
+++ b/internal/registry/model_definitions_test.go
@@ -7,6 +7,7 @@ func TestGitHubCopilotGeminiModelsAreChatOnly(t *testing.T) {
 	required := map[string]bool{
 		"gemini-2.5-pro":         false,
 		"gemini-3-pro-preview":   false,
+		"gemini-3.1-pro-preview": false,
 		"gemini-3-flash-preview": false,
 	}