diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0ed6172..de5277f 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -119,7 +119,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        model: [gpt-5-minimal, gpt-4.1, default, gemini-pro, glm-4.6, haiku]
+        model: [gpt-5-minimal, gpt-4.1, sonnet-4.5, gemini-pro, glm-4.6, haiku]
     steps:
       - name: Checkout
         uses: actions/checkout@v4
diff --git a/src/constants.ts b/src/constants.ts
new file mode 100644
index 0000000..3d73772
--- /dev/null
+++ b/src/constants.ts
@@ -0,0 +1,8 @@
+/**
+ * Application-wide constants
+ */
+
+/**
+ * Default model ID to use when no model is specified
+ */
+export const DEFAULT_MODEL_ID = "sonnet-4.5";
diff --git a/src/models.json b/src/models.json
index a67cef2..fe1e461 100644
--- a/src/models.json
+++ b/src/models.json
@@ -1,6 +1,6 @@
 [
   {
-    "id": "default",
+    "id": "sonnet-4.5",
     "handle": "anthropic/claude-sonnet-4-5-20250929",
     "label": "Claude Sonnet 4.5 (default)",
     "description": "The recommended default model (currently Sonnet 4.5)",