Arbitrary instruction execution from context memory. In some embodiments, an integrated circuit includes a processor core; a context management circuit coupled to the processor core; and a debug support circuit coupled to the context management circuit, where: the context management circuit is configured to halt a thread running on the processor core and save a halted thread context for that thread into a context memory distinct from the processor core, where the halted thread context comprises a fetched instruction as the next instruction in the execution pipeline; the debug support circuit is configured instruct the context management circuit to modify the halted thread context in the context memory by replacing the fetched instruction with an arbitrary instruction; and the context management circuit is further configured to cause the thread to resume using the modified thread context to execute the arbitrary instruction.