# Runtime Core Errors

Please see below a reference to each [@aurelia/runtime](https://github.com/aurelia/aurelia/tree/master/packages/runtime) package related error with explanations and resources for debugging and solving.

## Runtime Core Errors (0199-0228)

These errors occur in the core runtime functionality including scoping, observation, dirty checking, and computed properties.

* [AUR0199](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0199) - Observing null/undefined
* [AUR0203](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0203) - Null scope
* [AUR0204](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0204) - Create scope with null context
* [AUR0206](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0206) - Switch on null connectable
* [AUR0207](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0207) - Switch active connectable
* [AUR0208](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0208) - Switch off null connectable
* [AUR0209](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0209) - Switch off inactive connectable
* [AUR0210](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0210) - Non-recognizable collection type
* [AUR0217](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0217) - Dirty check no handler
* [AUR0218](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0218) - Dirty check not allowed
* [AUR0219](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0219) - Dirty check setter not allowed
* [AUR0220](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0220) - Assign readonly size
* [AUR0221](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0221) - Assign readonly property from computed
* [AUR0224](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0224) - Invalid observable decorator usage
* [AUR0225](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0225) - Stopping a stopped effect
* [AUR0226](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0226) - Effect maximum recursion reached
* [AUR0227](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0227) - Computed mutating
* [AUR0228](https://docs.aurelia.io/developer-guides/error-messages/0203-to-0227/aur0228) - Computed not getter