[kodablah]

Temporal determines a workflow is non-deterministic if upon code replay the high-level commands don't match up with what happened during the original code execution. In this case, technically it's safe to change the code this way because both still result timer commands. But what the timer was first created with on existing runs is what applies (there are reset approaches though as mentioned in other comment). However if, say, you changed the implementation do start a child workflow or activity before the timer, the commands would mismatch and you'd get a non-determinism error upon replay.

There are multiple strategies to update live workflows, see https://community.temporal.io/t/workflow-versioning-strategi.... Most often for small changes, people would use the `Workflow.Patched` API.