Screeps Error Codes and Return Values

Constant	Value	Practical meaning
`OK`	`0`	The command was accepted. The visible result may still appear on a later tick.
`ERR_NOT_OWNER`	`-1`	The object is not controlled by you, or the method requires ownership.
`ERR_NO_PATH`	`-2`	No route or path could be found under the current movement options.
`ERR_NAME_EXISTS`	`-3`	A requested name is already in use, commonly when spawning a Creep.
`ERR_BUSY`	`-4`	The object is already performing an incompatible action, such as a busy Spawn.
`ERR_NOT_FOUND`	`-5`	The requested object, resource, reaction, or state was not found.
`ERR_NOT_ENOUGH_ENERGY`	`-6`	The action lacks Energy or another required resource.
`ERR_INVALID_TARGET`	`-7`	The target exists but cannot be used by this method.
`ERR_FULL`	`-8`	The target store, structure, or capacity is already full.
`ERR_NOT_IN_RANGE`	`-9`	The acting object is too far from the target. Move closer and retry on a later tick.
`ERR_INVALID_ARGS`	`-10`	One or more arguments do not match the method contract.
`ERR_TIRED`	`-11`	The object is on cooldown or a Creep has fatigue.
`ERR_NO_BODYPART`	`-12`	The Creep lacks an active body part required for the action.
`ERR_RCL_NOT_ENOUGH`	`-14`	The room Controller level does not permit the requested structure or action.
`ERR_GCL_NOT_ENOUGH`	`-15`	The account does not have enough control level for the requested claim or expansion.

DEBUGGING PATTERN

Store the result once

Call the action once, save its result, log the result with context, and branch from that value. Avoid calling the same state-changing method repeatedly inside one expression.

NEXT STEP

Check the full room state

When several systems fail together, use a room snapshot to inspect workforce, Energy, Controller pressure, construction, and CPU.

Open room diagnostics →