nautechsystems/nautilus_trader · error

Actor for {id} not found

Error message

Actor for {id} not found

What it means

This panic comes from ActorRegistry::get_actor_unchecked, a lookup that assumes an actor with the given Ustr id exists. When the registry contains no entry for the id, the function panics with 'Actor for {id} not found'. It is the caller's responsibility to ensure the actor was registered before calling this unchecked accessor.

Source

Thrown at crates/common/src/actor/registry.rs:209

/// Only the exact ID is removed, so unrelated actors sharing the thread-local registry are
/// untouched.
pub fn deregister_actor(id: &Ustr) {
    with_actor_registry(|registry| registry.remove(id));
}

/// Returns a guard providing mutable access to the registered actor of type `T`.
///
/// The returned [`ActorRef`] holds an `Rc` to keep the actor alive, preventing
/// use-after-free if the actor is removed from the registry.
///
/// # Panics
///
/// - Panics if no actor with the specified `id` is found in the registry.
/// - Panics if the stored actor is not of type `T`.
#[must_use]
pub fn get_actor_unchecked<T: Actor>(id: &Ustr) -> ActorRef<T> {
    let actor_rc = with_actor_registry(|registry| registry.get(id))
        .unwrap_or_else(|| panic!("Actor for {id} not found"));

    match actor_ref_from_rc(actor_rc) {
        Ok(actor_ref) => actor_ref,
        Err(ActorRefError {
            expected_type,
            actual_type,
        }) => {
            panic!(
                "Actor type mismatch for '{id}': expected {expected_type:?}, found {actual_type:?}"
            )
        }
    }
}

/// Attempts to get a guard providing mutable access to the registered actor.
///
/// Returns `None` if the actor is not found or the type doesn't match.
#[must_use]

View on GitHub (pinned to 18893faf8b)

Solutions

1. Verify the actor was registered with the exact same Ustr id (Ustr is case-sensitive) before calling get_actor_unchecked
2. Ensure the actor's registration/spawn completes before the lookup (ordering of startup code)
3. Print or log the registry contents to compare against the id being requested
4. Use a checked lookup (registry.get(id)) returning an Option instead of the unchecked panic path

Example fix

// before
let orders = get_actor_unchecked::<MockActor>(&ustr("OrderManger"));
// after
let id = ustr("OrderManager"); // fix id spelling
let orders = get_actor_unchecked::<MockActor>(&id);

if registry.get(&id).is_some() {
    let actor = get_actor_unchecked::<T>(&id);
} else {
    eprintln!("actor {id} not registered");
}

fn actor_registered(registry: &ActorRegistry, id: &Ustr) -> bool {
    registry.get(id).is_some()
}

When it happens

Trigger: Calling ActorRegistry::get_actor_unchecked::<T>(id) (via with_actor_registry) with an id that was never registered, or after the actor was registered under a different id, or after the registry was reset/cleared.

Common situations: Typos or case mismatches in actor names; looking up an actor before the system has finished spawning/registering it; actors registered in a different registry instance than the one queried; tests that forget to register the actor under test.

Understand the failure class

Background: "Not found" and "does not exist" errors: why "Task not found", "No such folder", and "Can't find" fire when a lookup comes back empty — this error's family across 14 libraries.

Related errors

• Actor type mismatch for '{id}': expected {expected_type:?},
• in-flight mutex poisoned
• wallet balance mutex poisoned
• instrument update lock poisoned
• rate limiter decision lock poisoned

AI-assisted analysis of nautechsystems/nautilus_trader@18893faf8b (2026-09-08). Data as JSON: /api/errors/4f286d03d9d31df4. Report an issue: GitHub.