diff --git a/internal/misc/antigravity_version.go b/internal/misc/antigravity_version.go
index 93b54d0b5..679b815ac 100644
--- a/internal/misc/antigravity_version.go
+++ b/internal/misc/antigravity_version.go
@@ -16,7 +16,11 @@ import (
 )
 
 const (
-	antigravityFallbackVersion = "2.2.1"
+	// antigravityFallbackVersion is the client version reported when the hub
+	// manifest has not been fetched yet or cannot be reached. Cloud Code rejects
+	// newer models for clients below 2.9.0, so this floor must stay at or above
+	// that version.
+	antigravityFallbackVersion = "2.9.1"
 	antigravityHubPlatform     = "darwin/arm64"
 	antigravityVersionCacheTTL = 6 * time.Hour
 	antigravityFetchTimeout    = 10 * time.Second
diff --git a/internal/misc/antigravity_version_test.go b/internal/misc/antigravity_version_test.go
index 645f2f7a1..eb36b5d78 100644
--- a/internal/misc/antigravity_version_test.go
+++ b/internal/misc/antigravity_version_test.go
@@ -2,6 +2,7 @@ package misc
 
 import (
 	"context"
+	"fmt"
 	"net/http"
 	"net/http/httptest"
 	"testing"
@@ -42,8 +43,22 @@ func TestAntigravityLatestVersionUsesCurrentHubFallback(t *testing.T) {
 	defer restore()
 
 	version := AntigravityLatestVersion()
-	if version != "2.2.1" {
-		t.Fatalf("AntigravityLatestVersion() = %q, want %q", version, "2.2.1")
+	if version != antigravityFallbackVersion {
+		t.Fatalf("AntigravityLatestVersion() = %q, want %q", version, antigravityFallbackVersion)
+	}
+}
+
+// Cloud Code resolves newer models only for clients reporting at least 2.9.0;
+// older versions get 404 Requested entity was not found.
+func TestAntigravityFallbackVersionMeetsBackendFloor(t *testing.T) {
+	const floorMajor, floorMinor = 2, 9
+
+	var major, minor, patch int
+	if _, err := fmt.Sscanf(antigravityFallbackVersion, "%d.%d.%d", &major, &minor, &patch); err != nil {
+		t.Fatalf("antigravityFallbackVersion = %q is not a dotted version: %v", antigravityFallbackVersion, err)
+	}
+	if major < floorMajor || (major == floorMajor && minor < floorMinor) {
+		t.Fatalf("antigravityFallbackVersion = %q, want at least %d.%d.0", antigravityFallbackVersion, floorMajor, floorMinor)
 	}
 }