DeckyCache

Check compatibility before installing

Requirement	Current bundle
Supported SteamOS channel	Stable only. Beta, Preview and Main are not supported.
Tested SteamOS	3.8.28, build 20260922.1, on an NVIDIA x86-64 PC
Required kernel	6.18.50-valve2-1-neptune-618-gc7289a96b14d
Library drives	Separate ext4 data partitions
Tested Decky Loader	3.2.10

Check uname -r in Desktop Mode before installing. The kernel must match exactly. The SteamOS version alone is not enough: an update may change the kernel. This plugin does not rebuild or replace it; another kernel needs a matching module bundle.

Full compatibility and update information

Keep your games on the HDD. Cache the data you use on an SSD or NVMe.

DeckyCache is a Decky Loader plugin for SteamOS PC. Choose a dedicated cache drive, switch on the library drives you want to cache, and play. Open CAS stores accessed blocks on the faster drive while the original games and Steam updates stay on the HDD.

Install · First setup · User guide · Compatibility

What you get

• Choose an SSD or NVMe: format a dedicated drive or reuse one prepared by DeckyCache.
• Choose library drives: enable one or several supported game-drive partitions.
• Choose cache scope: cache reads across those drives or restrict new cached data to selected Steam, DRM-free or ROM folders.
• Master switch: temporarily bypass cache while keeping your drive selections and valid cached blocks.
• Compatible updates: check GitHub for a release matching the running kernel, then install through Decky with an automatic plugin reload. The built-in updater keeps compatible cache and library mounts connected.
• Persistent cache: cached blocks survive a clean shutdown and restart.
• Original games stay on the HDD: writes, including game updates, go to the original drive. New cache blocks come from reads within the selected drives or folders; writes do not allocate new cache blocks.
• Cached games: Steam games and direct non-Steam shortcuts, with existing Steam artwork and attributed cache sizes. Tiny entries appear under Small fragments.
• Other cached data: the final tile accounts for occupied cache outside the displayed game entries.
• Clear cache: remove cached copies without formatting the NVMe or deleting games.
• A compact controller-friendly panel: short labels, section dividers and details behind information buttons.

Download and install

Download the DeckyCache plugin ZIP from this repository's Releases. Choose the attached plugin ZIP, not the automatically generated source-code archive.

1. Open Decky Loader settings → General and enable Developer mode.
2. Open Developer → Install Plugin from ZIP File → Browse and choose the downloaded ZIP.
3. Alternatively, copy the plugin ZIP's direct download link from the release and paste it into Install Plugin from URL, then select Install.
4. Open DeckyCache from the Decky menu.

See the illustrated installation guide for screenshots. A download that requires signing in should be installed from the local ZIP.

For later updates, use Check for updates in DeckyCache, select the offered version and confirm Decky's installer. The plugin reloads automatically. See Updating the plugin.

First setup

1. Close games and let Steam downloads or updates finish.
2. In Cache drive, select your dedicated SSD/NVMe.
3. Choose Format and use for a new cache drive, or Reuse existing cache for a drive already prepared by DeckyCache.
4. Enable the desired partitions under Library drives.
5. Under Cache scope, keep Entire selected drives or choose Selected folders and add the folders you want.
6. Start a game. Eligible reads fill cache; installation and update writes do not allocate new cache blocks.

Format and use erases the entire selected cache drive. Check its model, size and serial number before confirming. The library HDD is not formatted or moved. See First setup.

What gets cached

Choose Entire selected drives for all eligible reads on the enabled partitions, or Selected folders for specific libraries. Add several folders across enabled drives as needed. Writes from copying, installation and Steam updates go to the HDD without allocating new cache blocks. Reads for copying, unpacking or verification can still fill cache within the selected scope. This is a folder filter, not a detector of whether a game is running.

Changing scope keeps existing cached data. Other cached data accounts for cached blocks outside the current game list, including data retained from earlier versions. Use Clear cache if you want to discard those copies; games on the HDD stay intact.

There is no pinning, full-game preloading or per-game eviction. Game sizes are partial attribution, not proof that every byte of a game is cached. Directory rules cannot identify every direct or asynchronous read; unidentified reads bypass cache in folder mode.

Compatibility and updates · How it works · Troubleshooting

Build from source

cd plugin
npm ci
npm run typecheck
npm run build
cd ..
python3 scripts/package.py

Before packaging, prepare the matching Open CAS binaries as described in the bundle build guide. Packaging produces build/DeckyCache-<version>.zip with the runtime, required licenses and offline user guide.

License

The plugin uses the BSD 3-Clause license. The release includes Open CAS, OCF and safeclib license notices and an upstream source reference in bin/opencas.