Why I build orchestration systems locally first

The first thing MOS does is run locally. That choice landed with the November 2025 build, after the July 2025 orchestration notes made reproducibility the gate before scale. Not as a limitation: as the point. An agent loop that only exists in a shared environment is one you can’t fully inspect, and one you can’t rerun to see whether a change actually helped.

Running locally first makes every step reproducible. The intermediate state is a file on disk I can open, diff, and replay. When something goes wrong I can see exactly which phase produced the bad output, instead of re-prompting and hoping. Only once the loop is boring and predictable does it earn the right to touch anything shared.

Most of the reliability I care about comes from that one decision. Impressive-but-opaque loses to reproducible-but-plain every time I’ve had to actually maintain the thing.