Updating an ATS Mod After an American Truck Simulator Game Update

Do not mark an ATS mod compatible because the main menu opens. A game update can change definitions, models, materials, sounds, UI, economy data, or tooling while leaving the first screen apparently healthy. Treat compatibility as a test result tied to an exact package and game version.

1. Preserve the last known-good state

Archive the released package, source revision, export tools, screenshots, listing copy, and the ATS version on which it passed. Create the update from a version-control branch or duplicated working directory so an emergency fix cannot destroy the previous release.

2. Read the update information before changing files

Review official game announcements and relevant changes in the SCS Modding Wiki documentation. If you publish through Workshop, use the uploader version that matches the game branch; SCS documents current, public-beta, historical, and legacy-compatible uploader builds in its official uploader changelog.

3. Reproduce with the smallest test setup

1. Copy the previous public archive into a clean ATS mod directory.
2. Use a dedicated test profile with only the mod and its required dependencies enabled.
3. Clear or rename the old game.log.txt, launch the updated game, and exercise every feature your mod changes.
4. Save the new log and note visible failures, warnings, reproduction steps, and affected configurations.
5. Repeat once without the mod to distinguish base-game behavior from your regression.

4. Triage evidence, not guesses

Sort issues into missing or renamed data, invalid definitions, changed model or material pipelines, altered sound or UI behavior, dependency changes, and harmless legacy warnings. Fix the first root error before chasing secondary messages; one missing definition can produce a long chain of misleading symptoms.

Original triage example: After an update, a configurable accessory disappears and the log reports a missing parent unit followed by six invalid accessory references. Verify and repair the parent unit first. Re-test before editing all six accessories; they may recover automatically once the shared dependency resolves.

5. Make the smallest complete compatibility change

Update affected definitions or re-export changed assets with the matching tools. Avoid unrelated feature work in the compatibility patch. A narrow change is easier to test, explain, and roll back while players are waiting.

6. Run a regression matrix

Test the configurations that cover meaningful variation rather than every cosmetic combination.

• New profile or clean configuration.
• Existing save already using the mod.
• Each supported truck, chassis, cabin, or trailer family.
• Required DLC present; optional DLC absent where applicable.
• Known dependencies in the documented load order.
• Purchase/configuration flow, normal driving, reload, and removal where safe.

Record the exact ATS build, test package checksum or file name, result, and log status. That small test ledger turns “seems fine” into repeatable release evidence.

7. Update compatibility metadata carefully

For standalone packages, review manifest.sii. SCS notes that restrictive compatible_versions entries can unnecessarily block a working mod after minor patches; use them when version coupling is real. Workshop packages can map different content packages to game versions through versions.sii, as explained in the official Workshop mod structure guide.

8. Package and retest the distributable

Increment the mod version, build a clean archive, install that archive instead of your source directory, and rerun the critical path. Check that the package name, manifest version, listing compatibility, and release notes all agree. Use the publishing checklist as the final gate.

9. Communicate what you know

Compatibility update example
Version 2.4.1, tested on ATS 1.x
Fixed accessory definitions affected by the game update.
Re-exported cabin materials with the matching tools.
Tested: all supported chassis, existing saves, clean profile, night lighting.
Known issue: third-party sound packs have not been validated.
Upgrade: replace version 2.4.0; no load-order change.

If testing is incomplete, say “testing in progress” and keep the old compatibility statement. A fast, uncertain green badge creates more support work than a short, precise delay.