usourcecontrol

5.1What Forge is

A standalone app for a build machine, so packaging stops being something a person does.

Section 1 of 4 in this chapter

USourceControl Forge is its own application with its own installer. It turns a machine you own into a build runner: it claims queued work, downloads exactly the committed state the build asked for, runs Unreal's RunUAT BuildCookRun, zips and uploads the artifact, and publishes the release.

It is separate from the desktop app on purpose. A build machine has no reason to run a sync client, and someone using the sync client has no reason to be carrying a build runner around.

   queue                runner (your machine)
     │
     ├─ claim ──────►  materialize commit #24
     │                        │
     │                        ▼
     │                 RunUAT BuildCookRun
     │                        │
     │                        ▼
     │                 validate · tests · smoke
     │                        │
     │                        ▼
     ◄──── publish ───  zip + upload artifact
                              │
                              ▼
                        deploy to Steam (optional)
Figure 5-1. What a runner does between claiming a job and publishing a release.

Why it is on every plan

Forge runs on your hardware with your engine. There is no cloud compute for us to meter, so there is nothing to charge for. It is included everywhere, Free included.

Incremental workspaces

The naive version of a build runner downloads the whole project every time. On a hundred-gigabyte game that is an hour of network before the first line compiles, every single build.

Instead a runner keeps its workspace between builds and records which commit sequence number it materialized. The next build asks the server for the delta since that number, so only files that actually changed are transferred.

The correctness work sits underneath that: a stat pass invalidates a baseline that has drifted on disk, downloads are verified by hash as they stream in, and any mismatch falls back to a full download rather than building something subtly wrong. A fast build that is occasionally wrong is worse than a slow one.

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