12. Application Data

Everything the application persists lives under the per-user AppData folder:

%LocalAppData%\CHDStudio\
├── logs\                          # Serilog rolling log files
│   └── CHDStudio-YYYYMMDD.log   (daily roll, 10 MB size roll, 7 files retained)
└── screenshots\                   # F8 captures
    └── screenshot_yyyy-MM-dd_HH-mm-ss-fff.png

%LocalAppData% resolves to C:\Users\<user>\AppData\Local on a standard install. F8 screenshots are saved into the screenshots folder beside logs; a screenshots folder next to the executable is used only when AppData cannot be written.

12.1 Logs

Configured in App.axaml.cs ConfigureSerilog.
File sink: %LocalAppData%\CHDStudio\logs\CHDStudio-.log, daily rolling (RollingInterval.Day) with a 10 MB size roll (rollOnFileSizeLimit), 7 files retained, minimum level Debug, invariant-culture timestamps {Timestamp:yyyy-MM-dd HH:mm:ss.fff} [{Level:u3}] {Message:lj}{NewLine}{Exception}.
Debug sink (visible in the Visual Studio debugger output) and the BugReportApiSink (warning+, see Bug Reporting System).
The in-app LogViewer shows the same messages. Lines are queued (oldest dropped past 2,000) and flushed in batches of at most 200 lines every 100 ms, a single line is capped at 2,000 characters, and the text is capped at 50,000 characters (MaxLogLength), so a large log cannot freeze the window; the AppData title-bar button opens %LocalAppData%\CHDStudio in Explorer.

12.2 Screenshots

While the application window is focused, F8 captures that window with Avalonia’s RenderTargetBitmap and saves it as screenshot_yyyy-MM-dd_HH-mm-ss-fff.png in %LocalAppData%\CHDStudio\screenshots (folder created on demand).
When that folder cannot be written, the capture falls back to a screenshots folder next to the executable.
The saved path is logged in the app (“Screenshot saved: …”).

12.3 Temporary Directories

Temp directories use the system temp folder by default; a folder at a drive root is only created when the system temp path is unsafe to hand to chdman (non-ASCII or near MAX_PATH) or its volume cannot hold the operation:

Pattern: CHDStudio_Temp_<guid> under the system temp folder, or {drive}\CHDStudio_Temp\ as the fallback (PathUtils.GetBestTempDirectory, see Utilities Reference).
Raw CD images that need a generated cue are staged in {drive}\CHDStudio_Temp\ on the image’s own volume, because chdman resolves a cue’s FILE entry relative to the cue’s directory.
Used for: archive extraction, CSO decompression, PBP/CCD cue generation, retry-via-temp-copy fallback, and cue work directories.
Cleanup: temp dirs are deleted after each file is processed; an emptied CHDStudio_Temp folder is removed with them, and at startup leftover CHDStudio_Temp_* folders (plus stale Explorer extractions older than a day) are removed (CleanupLeftoverTempDirectories, MainWindow.axaml.cs).

12.4 What Lives Next to the Executable

Item	Purpose
`CHDStudio.exe`	The application
`chdman.exe` / `chdman_arm64.exe`	MAME CHD tool (Windows; must stay next to the exe)
`7za.exe` / `7za_arm64.exe`	7-Zip fallback extractor (Windows)
`7zz` + `7-Zip-License.txt`	Official 7-Zip 26.03 console build (Linux/macOS)
`CHDSharp.dll`, `Avalonia` assemblies, etc.	Managed dependencies (copy-local); CHDSharp powers the built-in in-process encoder
`CCDSharp.dll`, `CSOSharp.dll`, `PBPSharp.dll`, `MDSSharp.dll`, `ISZSharp.dll`	In-house libraries

Legacy leftovers (logs and Resources folders; maxcso.exe, psxpackager.exe) are deleted automatically at startup by LegacyCleanupService (see Services Reference). A Screenshot folder next to the executable is left alone because it is the fallback location for F8 captures.

12.5 Network Endpoints

Endpoint	Purpose
`https://www.purelogiccode.com/bugreport/api/send-bug-report`	Bug reports (POST, `X-API-KEY` header)
`https://www.purelogiccode.com/ApplicationStats/stats`	Anonymous usage stats (POST, Bearer token)
`https://api.github.com/repos/purelogiccode/CHDStudio/releases/latest`	Update checks (GET, User-Agent)

All HTTP traffic goes through the shared AppHttpClient singleton (TLS 1.2/1.3, see Services Reference).