:sig
String session_start(String session_name = "uce-session")

:params
session_name : optional name of the session cookie, defaults to "uce-session"
return value : the current session ID

:see
>session

:content
Starts a session or reconnects to an existing one.

If the cookie named by `session_name` does not exist, UCE creates it and fills it with a new unique session ID. The function then loads the session data for that ID. Session cookies are emitted with `Path=/`, `HttpOnly`, `SameSite=Lax`, and `Secure` when `SESSION_COOKIE_SECURE=1` is set in the runtime config.

After `session_start()` completes, the following `context` fields are populated:

- `context.session_id` contains the current session ID.
- `context.session_name` contains the current session cookie name.
- `context.session` contains the current session data. The session data is automatically saved after the request completes.


:example
String id = session_start("uce-doc-example");
print(id != "" ? "started\n" : "empty\n");