Background:
Optional capabilities of java.lang.instrument (JLI) agents are specified as attributes in the JAR manifest. They cannot (currently) be set dynamically by agent code. The current implementation of JLI always uses a single implementation of "Instrumentation" which holds the capabilities.

The bug:
As a result, if multiple JLI agents are loaded (either at the command line or via attach) the first loaded agent creates the "Instrumentation" instance and sets its capabilities. A subsequent agent, with possibly greater capabilities specified in its attributes then has these capabilities ignored. So the bug is first one wins.