diff --git a/packages/contracts/src/model.ts b/packages/contracts/src/model.ts
index ee69b5ad2aa93f45c8105986ba88f1d5e4728e37..31e5f9d633050b71b07ced42590e1d4df5bf3162 100644
--- a/packages/contracts/src/model.ts
+++ b/packages/contracts/src/model.ts
@@ -161,7 +161,7 @@ export const PREFERRED_DEFAULT_CODEX_MODELS: ReadonlyArray<string> = [
   "gpt-5.6-sol",
   "gpt-5.6-terra",
 ];
-export const DEFAULT_TEXT_GENERATION_MODEL = "gpt-5.6-luna";
+export const DEFAULT_TEXT_GENERATION_MODEL = "gpt-6-luna";
 /** Keep the official Antigravity session's current model. Never send this ID to ACP. */
 export const ANTIGRAVITY_DEFAULT_MODEL = "antigravity-default";
 export const DEFAULT_TEXT_GENERATION_REASONING_EFFORT = "low";
diff --git a/packages/contracts/src/settings.test.ts b/packages/contracts/src/settings.test.ts
index 692edfb18a658f80ef5d02e73612ca995d85625d..16b9418ab7ccb22fddf3185057c92420be93610d 100644
--- a/packages/contracts/src/settings.test.ts
+++ b/packages/contracts/src/settings.test.ts
@@ -690,14 +690,6 @@ describe("ClientSettings pull request merge methods", () => {
 });
 
 describe("ServerSettings.providerInstances (slice-2 invariant)", () => {
-  it("defaults text generation to Luna at low reasoning effort", () => {
-    expect(DEFAULT_SERVER_SETTINGS.textGenerationModelSelection).toEqual({
-      instanceId: ProviderInstanceId.make("codex"),
-      model: "gpt-5.6-luna",
-      options: [{ id: "reasoningEffort", value: "low" }],
-    });
-  });
-
   it("defaults to an empty record so legacy configs without the key still decode", () => {
     expect(DEFAULT_SERVER_SETTINGS.providerInstances).toEqual({});
   });