FLX-2101: the bundle's inputDigest has moved since the plan was recorded
Family: plan/replay binding (the 2000 band)
KERNEL-SPEC section 11: apply/run refuse to proceed once a document the plan covered has changed on disk, an in-bundle FLUID contract has changed, or a document was added or removed. Re-run fluxsim plan against the bundle as it stands now, review the new plan, then apply it -- an apply is a decision about the bundle the plan describes, not about whatever the bundle happens to be by the time apply runs.
Look it up offline
$ fluxsim explain FLX-2101
Every code is listed in the error index.