Fragile native compilation of virtual machine code is described, in which a native code optimizer inspects external code entities such as Java base classes and emits target code based on an inter-procedural analysis of the code and data structure invariants and other properties of the external code entity. The fragile compiler also records which properties of the external code entities were used to produce the optimized code in a "fragile set", so that the virtual machine at which the compiled code is deployed and executed can detect if the recorded properties of the external code entities are compatible with the properties of the corresponding entities on the deployment virtual machine. If the code entities are incompatible, the compiled native code is rejected and the virtual machine reverts to interpreting the virtual machine code.