"Everything broke at once: check for a stale assembly first"

During a burst of edits (especially parallel agents):

• Audio dead, features missing, old bugs back: everything looks broken at once.
• Console may show Compile of … Failed / Broken Reference.
• Or worse: compiler wedged (success=False, 0 errors / 0 warnings, needsBuild=False). Editor keeps the stale assembly forever with nothing to "fix."

When the package compile fails (mid-edit, broken reference, internal compiler crash), the s&box editor silently keeps running the last good hotloaded assembly. Playtests then exhibit "regressions" from code that predates hours of committed work.

A related wedge: internal NullReferenceException / "One or more errors occurred" leaves compile status failed with no diagnostics and needsBuild=False: it thinks nothing needs rebuilding.

Also: Steam can update the engine under a running editor (mixed DLLs, stripped components on deserialize; do not save the scene in that state). First check sbox/.version mtime vs session start / appmanifest_590830.acf StateFlags.

Before debugging multi-symptom chaos

1. Grep the session log for Compile of / Failed / Broken Reference.
2. If present → finish or revert the broken edit, get a clean compile, restart Play. Do not chase the symptoms.
3. Wedge signature (success=False + 0 diagnostics + needsBuild=False): bump any watched .cs mtime to dirty the compile:

(Get-Item Code\SomeFile.cs).LastWriteTime = Get-Date

Then rebuild / alt-tab hotload; confirm clean.

Normal hotload expectations

• C# edits apply in ~ms on alt-tab.
• Network sessions reset on hotload.
• Scene-file changes need a Play restart.
• New assets sometimes need an editor kick.

After engine update underfoot

Relaunch editor, discard scene changes if components were stripped, verify dotnet build --no-incremental against the new assemblies before trusting anything.

Hotload prefers "keep playing" over "hard fail closed." That masks compile failure as gameplay regression. Checking compile health first collapses a dozen fake bugs into one real fix: restore a current, successful assembly.