diff --git a/src/youtube_extension/services/agents/antigravity_backend.py b/src/youtube_extension/services/agents/antigravity_backend.py
index 19ed10508..95c6d48e6 100644
--- a/src/youtube_extension/services/agents/antigravity_backend.py
+++ b/src/youtube_extension/services/agents/antigravity_backend.py
@@ -20,7 +20,7 @@
 from typing import Any, Protocol
 from urllib.parse import urlparse
 
-ANTIGRAVITY_AGENT = "antigravity-preview-05-2026"
+ANTIGRAVITY_AGENT = "antigravity-preview-09-2026"
 _MCP_NAME = re.compile(r"^[a-z0-9_-]+$")
 
 
diff --git a/tests/unit/test_antigravity_backend.py b/tests/unit/test_antigravity_backend.py
index f12e1e6ab..ea9ebc998 100644
--- a/tests/unit/test_antigravity_backend.py
+++ b/tests/unit/test_antigravity_backend.py
@@ -85,7 +85,8 @@ async def test_execute_builds_bounded_request_and_receipt() -> None:
     assert len(receipt.request_sha256) == 64
 
     payload = transport.payloads[0]
-    assert payload["agent"] == "antigravity-preview-05-2026"
+    assert payload["agent"] == "antigravity-preview-09-2026"
+    assert payload["environment"] == "remote"
     assert payload["agent_config"]["max_total_tokens"] == 1_000
     assert payload["tools"] == [
         {