diff --git a/CHANGELOG.md b/CHANGELOG.md
index af2dece18..340c08908 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -67,6 +67,13 @@ Anthropic's OpenAI-compatible endpoint, which may ignore the request for bare JS
 reply containing multiple objects fell back to offering every tool; replies with no valid `skills`
 list still do.
 
+### The AG2 Bot answers on a plain OpenAI key
+
+Picked with an OpenAI key, the AG2 Bot failed every run. Compose writes `OPENAI_BASE_URL` empty when
+the choice is a plain OpenAI key, and the OpenAI SDK only defaults an absent URL, so it was given ""
+as the address. The Bot now falls back to `https://api.openai.com/v1` for an empty value, as its
+Anthropic branch already did for `ANTHROPIC_BASE_URL`. An OpenAI-compatible endpoint is unchanged.
+
 ### Dictate messages and talk to a coworker in a live voice call
 
 Deployments can configure transcription separately from their Bots' models, with a waveform composer
diff --git a/agent-ag2/src/main.py b/agent-ag2/src/main.py
index 5828e4ab9..796bc31bb 100644
--- a/agent-ag2/src/main.py
+++ b/agent-ag2/src/main.py
@@ -23,7 +23,10 @@ def _config() -> AnthropicConfig | OpenAIConfig:
         # Compose exports missing overrides as ""; the SDK only defaults an absent URL.
         base_url = (os.environ.get("ANTHROPIC_BASE_URL") or "").strip() or "https://api.anthropic.com"
         return AnthropicConfig(model=model, base_url=base_url)
-    return OpenAIConfig(model=model)
+    # The same "" for OPENAI_BASE_URL, which Compose writes whenever the model screen chose a plain
+    # OpenAI key. The SDK only defaults an absent URL; given "", every request fails to connect.
+    base_url = (os.environ.get("OPENAI_BASE_URL") or "").strip() or "https://api.openai.com/v1"
+    return OpenAIConfig(model=model, base_url=base_url)
 
 
 agent = Agent(
diff --git a/agent-ag2/tests/test_main.py b/agent-ag2/tests/test_main.py
index 7f7341d3c..93cf26a8c 100644
--- a/agent-ag2/tests/test_main.py
+++ b/agent-ag2/tests/test_main.py
@@ -229,3 +229,40 @@ async def respond(transport, request):
     assert '"RUN_FINISHED"' in response.text
     assert '"RUN_ERROR"' not in response.text
     assert "hello" in response.text
+
+
+def test_an_openai_key_uses_the_official_endpoint_when_compose_sets_a_blank_url(monkeypatch):
+    # The same "" Compose writes for ANTHROPIC_BASE_URL above, on the other provider: the model screen
+    # sets only the key for a plain OpenAI key, and the SDK treats "" as an address, not as absent.
+    seen = []
+    provider_seen = []
+    provider_app = _provider_app(provider_seen)
+
+    async def respond(transport, request):
+        seen.append((str(request.url), request.headers.get("authorization")))
+        async with httpx2.ASGITransport(app=provider_app) as local_provider:
+            return await local_provider.handle_async_request(request)
+
+    # Keep the real AG2 and OpenAI clients; replace only the network transport.
+    monkeypatch.setattr(httpx2.AsyncHTTPTransport, "handle_async_request", respond)
+    monkeypatch.setenv("MANAGED_AGENT_TOKEN", TOKEN)
+    monkeypatch.setenv("BOT_PROVIDER", "openai")
+    monkeypatch.setenv("BOT_MODEL", "gpt-5.5")
+    monkeypatch.setenv("OPENAI_API_KEY", "test-key")
+    monkeypatch.setenv("OPENAI_BASE_URL", "")
+    monkeypatch.setenv("ANTHROPIC_API_KEY", "")
+    monkeypatch.setenv("ANTHROPIC_BASE_URL", "")
+
+    from src import main
+
+    main = importlib.reload(main)
+    response = TestClient(main.app).post(
+        "/", json=RUN, headers={"x-openbot-agent-token": TOKEN}
+    )
+
+    assert seen == [("https://api.openai.com/v1/chat/completions", "Bearer test-key")]
+    assert provider_seen == [("openai", "gpt-5.5")]
+    assert response.status_code == 200
+    assert '"RUN_FINISHED"' in response.text
+    assert '"RUN_ERROR"' not in response.text
+    assert "hello" in response.text