Official Status: September 6 Fix Released
A September 6 official fix addressed KOTAMON crash and infinite loading cases. Most launch issues should be fixed on the latest build, but conflicting apps may remain and some players may still need save, config, overlay or file-integrity triage. Treat the checks below as safe follow-up steps, not guaranteed developer-confirmed cures.
Quick Diagnosis
First update KOTAMON and restart Steam. If Steam Play still instantly closes while the game exe can launch manually, check path length first, then test -dx11. First launch fails before a real save exists: remove overlays, verify files and update graphics drivers. Loading never finishes after the September 6 official fix: suspect config, Steam Cloud or save state. Existing save fails but a fresh game works: back up the save and isolate that slot. Nothing works: collect evidence and report it instead of deleting data blindly.
KOTAMON Instant Crash on Launch - Windows 260 Path Limit Fix
A current Steam guide surfaces a Windows path-length crash pattern for KOTAMON: Steam Play closes instantly, but manually launching the executable may still work. Microsoft documents the classic Windows MAX_PATH limit as 260 characters and notes that long-path behavior depends on both system settings and application support. The low-risk player test is to move the Steam library or game install into a shorter folder path, then retry from Steam.
DX11 Branch
If the crash is instant or happens before normal menu input, open Steam Library, right-click KOTAMON, open Properties, add -dx11 under Launch Options, then start the game once. Remove the option if it does not help so later tests are clean. This is a community workaround, not a developer-confirmed cure.
Steam Cloud, Save and Config Branch
If the game reaches loading but never finishes, or if one save fails while a new game works, back up the save folder before changing anything. Then test Steam Cloud sync state, config files and one save slot at a time. Rename one suspect file, launch once, and restore it if behavior does not change.
First-Launch Failure Branch
If KOTAMON has never opened successfully on this PC, prioritize non-save causes first: verify files, remove launch options except a single -dx11 test, close overlays, update GPU drivers and shorten the install path. Save deletion is unlikely to help when no useful save has been created yet.
Existing-Save Failure Branch
If the game starts with a new profile but fails with an older save, do not overwrite the old save. Record the slot, patch date, last in-game action, Steam Cloud state and whether the failure began after a crash, pile generation, store visit or collectible pickup.
KOTAMON Stuck Loading Forever
The September 6 official fix specifically addressed infinite loading, so first confirm the game is fully updated. If loading still never finishes after verifying files, restarting Steam and trying only one clean launch-option test, treat it as different from an instant crash. Before deleting anything, back up the save folder, then test by renaming one suspect config or save file at a time and restoring it if behavior does not change.
Save Slot and Config Isolation
If a fresh save loads but an old slot does not, record which slot fails. Community troubleshooting has mentioned settings and global save files as possible suspects, but different players may have different broken files. The safe pattern is backup, rename one file, test, restore if ineffective, then move to the next suspect.
Reported DX11 Symptom
A Steam Community crash thread for KOTAMON includes instant-crash reports. One community reply suggests trying -dx11 in Steam Launch Options. Treat this as a community workaround, not an official fix.
Overlay Conflict Check
Before reinstalling, close one overlay layer at a time: Steam overlay, Discord overlay, recording overlays, GPU monitoring panels and RTSS/MSI Afterburner style hooks. Record which one changed the crash behavior.
Official Steam Fallback
Use Steam Verify integrity of game files before reinstalling. Steam Support documents this flow under Installed Files, and it is lower risk than deleting local data.
Evidence to Capture
Record whether the crash happens before the Unity window, during loading, or after menu input. Also note GPU, driver version, launch options, overlay apps and whether Steam file verification found changes.
If None of This Works
Stop changing files and write a compact bug report: exact failure point, Windows version, GPU, driver version, install path length, launch options tested, Steam Cloud state, whether a fresh save works and whether Steam file verification found changes. Unresolved startup failures after the September 6 official fix should still be treated as report-worthy edge cases.
When to Stop
Do not wipe saves unless you have backed them up and confirmed the issue is not only a launch option, overlay, driver or file-integrity failure. Workarounds can fail; that does not mean your save is safe to delete.