diff --git a/changelog.d/features/11685-antigravity-auto-sync-default.md b/changelog.d/features/11685-antigravity-auto-sync-default.md
new file mode 100644
index 0000000000..63368cc15a
--- /dev/null
+++ b/changelog.d/features/11685-antigravity-auto-sync-default.md
@@ -0,0 +1 @@
+- Default new Antigravity-family connections (agy CLI imports and Antigravity OAuth connects) to model auto-sync, so live model discovery lands in the synced catalog and `/v1/models` picks up freshly released upstream models (e.g. Gemini 3.7 Flash tiers) without code changes. Existing connections keep their current setting; the per-connection dashboard toggle remains the opt-out. (#11685 — thanks @MumuTW)
diff --git a/src/lib/oauth/providers/antigravity.ts b/src/lib/oauth/providers/antigravity.ts
index 636bfc3a88..5cab4d6f93 100644
--- a/src/lib/oauth/providers/antigravity.ts
+++ b/src/lib/oauth/providers/antigravity.ts
@@ -247,6 +247,12 @@ function mapAntigravityTokens(
       clientProfile,
       projectId: extra?.projectId,
       tier: extra?.tierId,
+      // The Antigravity backend ships new models frequently (e.g. Gemini 3.7
+      // Flash tiers appeared upstream weeks before the pinned catalog knew
+      // them). Default new connections into the 24h model auto-sync (#488) so
+      // live discovery lands in the synced catalog and /v1/models stays
+      // current without code changes. Operator-controlled per connection.
+      autoSync: true,
     },
   };
 }
diff --git a/src/lib/oauth/utils/agyAuthImport.ts b/src/lib/oauth/utils/agyAuthImport.ts
index 86edf19d78..d0a526eb23 100644
--- a/src/lib/oauth/utils/agyAuthImport.ts
+++ b/src/lib/oauth/utils/agyAuthImport.ts
@@ -216,6 +216,10 @@ export async function createConnectionFromAgyToken(
         testStatus: "active",
         isActive: true,
         providerSpecificData: {
+          // Auto-sync default for newly discovered backends — see
+          // mapAntigravityTokens. Placed BEFORE the existing-data spread so a
+          // previously persisted operator choice (true or false) wins.
+          autoSync: true,
           ...toRecord(existing.providerSpecificData),
           clientProfile: "cli",
           tokenType: enriched.tokenType,
@@ -249,6 +253,8 @@ export async function createConnectionFromAgyToken(
     isActive: true,
     testStatus: "active",
     providerSpecificData: {
+      // Default new imports into model auto-sync — see mapAntigravityTokens.
+      autoSync: true,
       clientProfile: "cli",
       tokenType: enriched.tokenType,
       authMethod: enriched.authMethod,
diff --git a/tests/unit/antigravity-family-auto-sync-default.test.ts b/tests/unit/antigravity-family-auto-sync-default.test.ts
new file mode 100644
index 0000000000..5422dc1606
--- /dev/null
+++ b/tests/unit/antigravity-family-auto-sync-default.test.ts
@@ -0,0 +1,132 @@
+/**
+ * Antigravity-family connections default to model auto-sync on (#488).
+ *
+ * The Antigravity backend ships new models faster than the pinned catalog can
+ * be re-frozen by hand (Gemini 3.7 Flash tiers existed upstream while the
+ * catalog still stopped at 3.6, leaving /v1/models blind to them). Discovery
+ * and the 24h model-sync scheduler already exist — the missing piece was the
+ * opt-in trigger. New agy/antigravity connections now ship with
+ * providerSpecificData.autoSync = true so live discovery lands in the synced
+ * catalog automatically; an explicit operator choice must survive re-import.
+ */
+
+import test from "node:test";
+import assert from "node:assert/strict";
+import fs from "node:fs";
+import os from "node:os";
+import path from "node:path";
+
+type Row = Record<string, unknown>;
+
+const TEST_DATA_DIR = fs.mkdtempSync(path.join(os.tmpdir(), "omniroute-agy-autosync-"));
+process.env.DATA_DIR = TEST_DATA_DIR;
+
+const { agy } = await import("../../src/lib/oauth/providers/agy.ts");
+const { antigravity } = await import("../../src/lib/oauth/providers/antigravity.ts");
+const providers = { agy, antigravity };
+const { createConnectionFromAgyToken } = await import("../../src/lib/oauth/utils/agyAuthImport.ts");
+const providersDb = await import("../../src/lib/db/providers.ts");
+const core = await import("../../src/lib/db/core.ts");
+
+const TOKENS = {
+  access_token: "agy-access-token-fixture",
+  refresh_token: "agy-refresh-token-fixture",
+  expires_in: 3600,
+  scope: "https://www.googleapis.com/auth/cloud-platform",
+};
+const POST_EXCHANGE = {
+  projectId: "fixture-project",
+  tierId: "free_tier",
+  userInfo: { email: "fixture@example.com" },
+};
+
+function asRecord(value: unknown): Row {
+  return value && typeof value === "object" ? (value as Row) : {};
+}
+
+function enrichedAuth(overrides: Partial<Row> = {}): Row {
+  return {
+    accessToken: TOKENS.access_token,
+    refreshToken: TOKENS.refresh_token,
+    expiresAt: null,
+    projectId: null,
+    tier: null,
+    tokenType: "Bearer",
+    authMethod: "consumer",
+    ...overrides,
+  };
+}
+
+async function findRowByEmail(email: string): Promise<Row | undefined> {
+  const rows = (await providersDb.getProviderConnections({ provider: "agy" })) as Row[];
+  return rows.find((row) => row.email === email);
+}
+
+test("agy OAuth mapTokens defaults providerSpecificData.autoSync to true", () => {
+  const mapped = providers.agy.mapTokens(TOKENS, POST_EXCHANGE) as Row;
+  assert.equal(asRecord(mapped.providerSpecificData).autoSync, true);
+  assert.equal(asRecord(mapped.providerSpecificData).clientProfile, "cli");
+});
+
+test("antigravity OAuth mapTokens defaults providerSpecificData.autoSync to true", () => {
+  const mapped = providers.antigravity.mapTokens(TOKENS, POST_EXCHANGE) as Row;
+  assert.equal(asRecord(mapped.providerSpecificData).autoSync, true);
+  assert.equal(asRecord(mapped.providerSpecificData).clientProfile, "ide");
+});
+
+test("new agy CLI token import persists autoSync: true", async () => {
+  core.resetDbInstance();
+  const email = "import-autosync@example.com";
+  const { connection, created } = await createConnectionFromAgyToken(
+    enrichedAuth({ email }) as never,
+    {}
+  );
+  assert.equal(created, true);
+  const row = (await providersDb.getProviderConnections({ provider: "agy" })) as Row[];
+  const match = row.find((candidate) => candidate.id === (connection as Row).id);
+  assert.equal(asRecord(match?.providerSpecificData).autoSync, true);
+});
+
+test("re-import keeps an explicit autoSync: false choice", async () => {
+  core.resetDbInstance();
+  const email = "import-optout@example.com";
+  const { connection } = await createConnectionFromAgyToken(enrichedAuth({ email }) as never, {});
+  await providersDb.updateProviderConnection(String((connection as Row).id), {
+    providerSpecificData: {
+      ...asRecord((connection as Row).providerSpecificData),
+      autoSync: false,
+    },
+  });
+
+  const { created } = await createConnectionFromAgyToken(
+    enrichedAuth({
+      email,
+      accessToken: "refreshed-access-token-fixture",
+      refreshToken: "refreshed-refresh-token-fixture",
+    }) as never,
+    { overwriteExisting: true }
+  );
+  assert.equal(created, false);
+  assert.equal(asRecord((await findRowByEmail(email))?.providerSpecificData).autoSync, false);
+});
+
+test("re-import enables autoSync when the existing row never had it", async () => {
+  core.resetDbInstance();
+  const email = "import-legacy@example.com";
+  const { connection } = await createConnectionFromAgyToken(enrichedAuth({ email }) as never, {});
+  // Simulate a pre-default row: strip autoSync entirely.
+  await providersDb.updateProviderConnection(String((connection as Row).id), {
+    providerSpecificData: { clientProfile: "cli" },
+  });
+
+  await createConnectionFromAgyToken(
+    enrichedAuth({
+      email,
+      accessToken: "refreshed-access-token-fixture",
+      refreshToken: "refreshed-refresh-token-fixture",
+    }) as never,
+    { overwriteExisting: true }
+  );
+
+  assert.equal(asRecord((await findRowByEmail(email))?.providerSpecificData).autoSync, true);
+});