diff --git a/agent/utils/auth.py b/agent/utils/auth.py
index a8a0dfb1..53ea6c1e 100644
--- a/agent/utils/auth.py
+++ b/agent/utils/auth.py
@@ -192,7 +192,12 @@ async def get_github_token_for_user(ls_user_id: str, tenant_id: str) -> dict[str
                 return result
             if auth_url:
                 return {"auth_url": auth_url}
-            return {"error": f"Unexpected auth result: {response_data}"}
+            # Log the full upstream body server-side only; the returned error becomes a
+            # user-facing Slack/Linear comment, so never echo the raw response body.
+            logger.error(
+                "GitHub auth returned an unexpected result (no token/url): %s", response_data
+            )
+            return {"error": "GitHub auth returned an unexpected result"}
 
     except httpx.HTTPStatusError as e:
         # Log the full upstream body server-side only; the returned error becomes a
diff --git a/tests/test_auth_error_leak.py b/tests/test_auth_error_leak.py
index 02907887..33cb1cbc 100644
--- a/tests/test_auth_error_leak.py
+++ b/tests/test_auth_error_leak.py
@@ -43,6 +43,19 @@ class _Client:
         return self._resp
 
 
+class _OkResp:
+    """A 2xx response whose JSON body lacks both a token and an auth url."""
+
+    def __init__(self, payload: Any) -> None:
+        self._payload = payload
+
+    def raise_for_status(self) -> None:
+        return None
+
+    def json(self) -> Any:
+        return self._payload
+
+
 def test_http_error_returns_generic_message(monkeypatch: pytest.MonkeyPatch) -> None:
     monkeypatch.setattr(auth, "GITHUB_OAUTH_PROVIDER_ID", "provider-id")
     monkeypatch.setattr(auth, "X_SERVICE_AUTH_JWT_SECRET", "jwt-secret")
@@ -53,3 +66,16 @@ def test_http_error_returns_generic_message(monkeypatch: pytest.MonkeyPatch) ->
     assert "error" in result
     assert _SECRET_BODY not in result["error"]
     assert "500" in result["error"]
+
+
+def test_unexpected_result_returns_generic_message(monkeypatch: pytest.MonkeyPatch) -> None:
+    """The 2xx-but-missing-token/url branch must not echo the upstream body."""
+    monkeypatch.setattr(auth, "GITHUB_OAUTH_PROVIDER_ID", "provider-id")
+    monkeypatch.setattr(auth, "X_SERVICE_AUTH_JWT_SECRET", "jwt-secret")
+    body = {"unexpected_field": _SECRET_BODY}
+    monkeypatch.setattr(httpx, "AsyncClient", lambda *a, **k: _Client(_OkResp(body)))
+
+    result = asyncio.run(auth.get_github_token_for_user("ls-user", "tenant"))
+
+    assert result == {"error": "GitHub auth returned an unexpected result"}
+    assert _SECRET_BODY not in result["error"]