CodeInstances Forks a Run at Any Step

CodeInstances 0.6 adds fork. codeinstances fork -at 9 run.instance answers a kept run’s first eight calls from the recording and then lets the program carry on live from call nine, so an agent or job that went wrong late doesn’t have to spend the time and the calls to get back there. With -answer and -offline, call nine gets an answer you write instead, a 503 say, and nothing goes out: a what-if on a real run rather than a mock. The release post has the details, and binaries are out for Linux, macOS and Windows.

A fork is an instance like any other. It names its parent and step, every call says whether its answer came from the parent, was given or was sent, and the program gets the parent’s clock and random values back, so diff against the parent shows what the step changed. Running a different command after -- forks a new build against the old run.

An independent review before release found that a kept setting such as NO_PROXY could let an offline fork reach the network, and that a shrunk fork kept a parent it no longer matched. Both are fixed and tested. 100 Go tests pass with a clean race detector run, and the recorded what-if fork in the demo took 25 ms. Signed, tamper-evident instances are next on the plan.