An Android launcher and on-device porting toolkit for Hollow Knight: Silksong, with Steam sign-in, game downloads, Cloud saves, achievement synchronization, and single-screen or dual-screen play. The launcher prepares a native ARM64 Unity player from your own Linux game files; it is not game streaming and does not require the desktop Steam client to run on Android.
This is a community project based on jakobkhansen's SilksongAndroid, with additional SteamSync and achievement features. It is not an official Team Cherry or Valve release.
- On-device porting: select an existing Linux depot or download it through Steam. The launcher fetches the required Unity and Android-hosted tools, compiles the patches and game assemblies through IL2CPP/C++, and assembles the native ARM64 player on the device.
- Reusable build data: downloaded tools and conversion/build outputs are cached. Source or app changes can require another conversion; cached inputs reduce repeated work. The original game folder remains necessary for play.
- Launch preparation: checks the installed content, prepares local saves, exports game settings, optionally downloads Cloud saves, and waits for the signed-in achievement bridge before starting the game. Failures appear in a preparation screen instead of silently launching an unready session.
- Dashboard: game artwork, Play, Steam account access, Cloud saves, achievement preview, settings, About, and safe exit.
- Diagnostics: launcher and Steam bridge logs, diagnostic viewing/sharing, and an advanced build-reset action for troubleshooting.
- Safe exit: requests a pending-achievement flush and clears Steam playing status before disconnecting. A network failure can still prevent submission.
- Steam sign-in: QR approval through the Steam mobile app, or account name and password with Steam Guard confirmation when required.
- Game download: uses the signed-in account's access to Silksong's Linux depot. Supplying compatible game files manually is also supported.
- Steam Cloud: manual download/upload, optional automatic download before play and upload on return to the launcher, and conflict choices when the destination has newer data. Both automatic options default to off.
- Save history: browses the backup/version files Steam currently exposes, restores a selected slot, pairs historical shared achievement state where available, and backs up the current local save set before restoring.
- Real Steam achievement updates: forwards achievements earned in the game to the signed-in Steam account and checks Steam's response before treating a new upload as confirmed.
- Achievement reconciliation: checks achievement flags already recorded by the game to recover eligible unlocks missed by older builds or failed writes.
- Achievement viewer: names, descriptions, locked/unlocked state, unlock dates where supplied, completion count/percentage, and numerical progress where Steam supplies it. Tap an achievement for details.
- Spoiler control: locked secret achievements are concealed until explicitly revealed for the current viewer session; the dashboard masks their artwork.
- Preview card: up to five icon tiles, a remaining-count overlay, and overall completion progress; tapping opens the full list.
- Image cache: achievement icons are reused from memory and disk, with placeholders when unavailable, rounded corners, and separated list rows.
- Playing status and notifications: announces Silksong to Steam while the game is active, respects another client's playing-session block, and shows an in-game toast after a confirmed new unlock.
- Single-screen play and optional dual-screen support on compatible hardware. The secondary screen provides touch-driven map, inventory/loadout, crests, tasks, and journal views using the game's data.
- Controller/game input support through the port's Android player and Input System integration, plus touch interaction with inventory and secondary views. This does not imply a complete on-screen touch gamepad.
- Settings: automatic Cloud download/upload, skip startup logos/intro, performance overlay, and enable/disable the secondary screen.
- Port compatibility patches: render-resolution configuration, shader warmup, animator fixes, and save-file replacement compatibility. These are internal port features, not all separate launcher settings.
PR #3 adds the following launcher improvements:
- Compact dashboard cards and a two-column layout on sufficiently wide screens.
- Cloud status showing the last completed sync, current activity, and failure/ retry guidance; clearer download/upload confirmations.
- Achievement search, All/Unlocked/Locked filters, Latest/Name/Closest-progress sorting, and an expanded detail dialog with a larger icon and progress.
- Account-scoped achievement display snapshots for faster reopening, with saved/live data and freshness labels. This is a display cache, not an offline upload queue.
- Grouped settings with collapsible advanced options and improved text wrapping.
- An offline Credits & licenses screen containing this repository's
CREDITS.md,NOTICE.md, andLICENSE. - Manual-only APK build triggering. No compilation is needed to edit this README.
Settings → Display offers Keep game setting, Native, 540p, 720p, 900p, 1080p, and 1440p. Presets use landscape render height, preserve the panel aspect ratio, and are capped at native resolution. Keep game setting preserves the saved choice, including the existing one-time 720p default. A chooser appears before launch; disable Ask before each launch to reuse the saved selection. Cancel aborts launch without saving the chooser changes. The in-game resolution menu remains usable.
Settings → Steam achievements → Show advanced achievement controls offers these switches, applied on the next launch:
| Control | Effect when disabled |
|---|---|
| Missing-achievement repair helpers | Does not create the repair component; normal game-to-Steam unlock delivery remains active. |
| Startup check | Skips the startup repair scan. |
| Scene/save/resume checks | Skips scans triggered by those lifecycle events. |
| Periodic check | Does not start the periodic repair coroutine, including the default 120-second scan. |
| Extra award-event listener | Disables the repair helper's supplementary listener; the primary online-subsystem path remains active. |
| Confirmed popups | Hides the port's achievement toasts without suppressing submissions. |
Periodic intervals: 60, 120 (default), 300, or 600 seconds. Repair helpers and popups default to enabled. Subordinate repair controls are disabled in the UI when the repair master switch is off, retaining their choices. The extra award-event helper can still schedule confirmation checks, and pending write retries remain active independently of periodic scans. To disable all optional repair scans, turn off the repair master control. Fewer checks may delay recovery of missed achievements. Steam authentication, schema validation, the native bridge, and confirmed-write handling remain enabled; existing Steam unlocks are never undone by these switches.
- Pre-launch FPS: Keep game setting, 30, 60, 90, or 120 FPS in the display chooser and Settings. An explicit selection is held for that game session and capped at the available display refresh rate; actual performance may be lower. Select Keep game setting to use the in-game frame-rate control again.
- Check for missed achievements now: The Steam achievements card explains the action before starting the game. It checks recorded local achievement flags and submits eligible missing unlocks to Steam. Load the desired save. This enables startup and scene-load repair checks for that session even when repair is disabled, without changing stored repair switches. It cannot award achievements that have no qualifying local record, and Steam must accept each submission.
- Automatic local backups: before a non-empty Cloud download writes any save,
the launcher creates and verifies a ZIP of existing local save files. A failed
backup aborts the download. The five newest completed snapshots are retained
under the app's external-files
cloud-download-backupsdirectory. Cloud saves & backups can export the latest backup through Android's document picker. These local backups are separate from Steam Save History and are removed if app data is cleared or the app is uninstalled; export a copy first. There is no automatic rollback or in-app local-ZIP restore in this update.
- Download the latest APK from this repository’s Releases and install it.
- Supply your own game files. Either copy them across from your PC yourself, or let the app fetch them for you by signing in to Steam.
- Press the button. The app fetches everything it needs and builds the game. The build takes 20–30 minutes on a Snapdragon 8 Gen 2, most of it the download and the compile.
- Play. Later launches reuse the prepared player, with content, save, and Steam readiness checks as applicable.
The upstream project reports testing on the AYN Thor and Retroid Pocket Flip 2. Compatibility depends on Android version, ARM64 tooling execution, graphics drivers, and device resources; support for every Android device is not guaranteed. Report your device and Android version when opening an issue.
If you'd rather not sign in, download the game's Linux depot on a PC with DepotDownloader. The Linux files are the ones the port is built from; the Windows (1030301) and macOS (1030302) depots will not do, and the app rejects them:
DepotDownloader -app 1030300 -depot 1030303 -username <your account> -password <your password> -dir silksongCopy the whole silksong folder onto the device, as long as it is on
the device's own storage. Then press Choose folder in the app and pick it.
silksong/ <-- pick THIS one
├── Hollow Knight Silksong.x86_64
├── UnityPlayer.so
└── Hollow Knight Silksong_Data/
├── Managed/
├── MonoBleedingEdge/
├── Plugins/
├── Resources/
├── StreamingAssets/
├── globalgamemanagers
├── resources.assets
└── ...
Wherever you put them, leave them there. The game is several gigabytes of content that
is never copied into the app: it is read from that folder every time you play, and every
app update that rebuilds the game reads it too. Deleting or moving the folder stops the
game from starting. The app leaves a SILKSONG-DO-NOT-DELETE.txt in there saying so.
The Kotlin launcher uses JavaSteam, an open-source Steam protocol client,
through SteamSession.kt. It maintains a Steam client and callback-processing
thread for each session. QrAuth.kt and CredentialsAuth.kt handle QR/password
login and Steam Guard approval; Steam returns credentials for subsequent login.
No user-supplied Steam Web API key is required by this implementation.
TokenStore.kt stores the account name and refresh token encrypted with
AES-256-GCM using an Android Keystore key. The password is not saved. The refresh
token is sent back to Steam to authenticate later sessions—it would be incorrect
to say that it never leaves the device. Signing out clears the stored credentials
and their encryption key.
The achievement service owns a long-lived authenticated session. Depot downloads, Cloud transfers, and save-history operations use their own session paths; the viewer reads the achievement service's display state instead of opening another Steam login just to draw the page.
Silksong's App ID is 1030300, and the required Linux depot is 1030303.
DepotFetcher.kt uses JavaSteam Depot Downloader and the signed-in account's
Steam access to retrieve the content. The launcher verifies the expected Linux
layout before using it. Windows depot 1030301 and macOS depot 1030302 are not
interchangeable with the Linux files used by this port.
The downloaded game stays on the device. The launcher converts/builds it locally; Steam is providing authenticated content delivery, not remotely running the game.
SteamCloudClient.kt talks to Steam's Cloud unified service to enumerate
files and obtain transfer instructions. File bytes are transferred with OkHttp;
uploads use Steam's begin-upload and commit-upload protocol. Compressed download
payloads are decoded when necessary.
CloudSync.kt maps Steam's remote Silksong path prefix to the Android game's
local save directory. It compares timestamps, skips unchanged entries, and asks
which side to keep when a transfer would replace newer destination data. Ordinary
sync excludes nested desktop restore-point directories; save history handles
historical entries separately. Upload cleanup can also remove eligible rotated
backup files left on Steam after the local game has pruned them.
Automatic download runs during launch preparation. Automatic upload runs when returning from the game to the launcher, so force-stopping the app is not a reliable way to trigger an upload. These are file transfers, not a live merge between two simultaneously running games. Transfer failures can leave some files transferred and others pending; conflict confirmation is not a multi-file transaction guarantee.
SaveHistory.kt can only show versions still available through Steam. It restores
the selected slot and the best available historical shared.dat companion,
with a local pre-restore backup. Restoring old saves does not relock
achievements already accepted by Steam.
The achievement path has three layers:
- Game-side C# patches:
AndroidSteamOnlineSubsystem.csinstalls an Android implementation into Silksong's desktop online-subsystem path. It receives the game's achievement calls.SteamAchievementRepair.csalso listens to game lifecycle/award events and reconciles achievement flags from local game state. - Native compatibility bridge:
steam_api_shim.csupplies the Steamworks.NET native entry points needed by the port and forwards requests over an Android local socket. It is this project's compatibility shim, not a full Android Steam client or a complete implementation of every Steamworks API. - Kotlin foreground service:
AchievementService.ktreceives readiness, get/set-achievement, and store requests and uses JavaSteam'sSteamUserStatshandler to communicate with Steam for App ID1030300.
At initialization, the service fetches the signed-in player's Steam stats and achievement schema, maps achievement API names to their stat blocks/bits, and loads the existing unlock state. It also requires the launcher's validated Steam depot installation path. A signed-in launch waits for this service to become ready; it does not silently continue with broken achievement synchronization.
A new game-earned unlock is queued. Before submitting, the service fetches fresh
Steam state, merges the requested bits with existing unlocks, and submits
storeUserStats with the current stats CRC. It checks the result, stale-state
flag, and validation failures, with bounded retry. Only an accepted response
confirms the write and allows the new-unlock notification. Existing Steam unlocks
are preserved, and names absent from Steam's schema are rejected.
Intermediate gameplay progress is not generally uploaded as arbitrary numeric Steam stats. For a progress-based achievement, reaching the game's declared maximum can trigger the final unlock; partial progress stays local. Viewer progress bars reflect the data Steam actually returns.
Pending writes are held in memory, with game-side retry/reconciliation; there is no durable, guaranteed offline achievement-upload queue. Previously recorded local achievement flags may be reconciled after reconnection, but every unlock still needs Steam acceptance. The launcher does not expose a reset-Steam- achievements or unlock-everything control.
The native Android achievement screens use the same service data: schema names, descriptions, icon references, secret flags, timestamps, and supported progress. Public achievement artwork is fetched from Steam's image CDN and cached locally. The account-scoped display cache is read-only presentation data; it is never used as authoritative input for writing achievements to Steam.
The service also publishes an Online persona and sends Steam's games-played message when the game is active, then clears playing status on inactivity or shutdown. It respects a playing-session block from another client. This supports Steam playing presence; it is not a promise of exact playtime accounting or a Steam overlay inside the Android game.
Steam sign-in and ownership verification are required before play, including when the game files were supplied manually. Downloads, Cloud operations, live achievement retrieval/submission, and Steam presence require network access and a valid account session. With saved credentials present, the current launch gate requires a ready Steam achievement service; it does not provide an automatic offline fallback. Cached icons or display snapshots do not make those network features work offline.
Implementation sources: launcher Kotlin code, native Steam shim, and game patches.
☕ The developer wanted to give you a good time, and in return you can offer them a coffee in https://ko-fi.com/lukevalen/donate 🫐
This project builds on jakobkhansen and the SilksongAndroid contributors. The achievement viewer adapts features from phobos665's original GameNative viewer and VinceBT's refinements in GameNative PR #1695.
See CREDITS.md for the specific features adapted, source links, library contributions, and artwork credits. Third-party license notices are in NOTICE.md.
Parts of this project were developed with AI assistance. Source review, successful compilation, and device testing are separate checks; unmerged or unbuilt changes should not be assumed to have passed all three.
Silksong is © Team Cherry. The launcher does not bundle the playable game depot; you supply your own game files. Game and Steam artwork shown in the launcher remains the property of its respective owners. The APK is a build system: it downloads Unity's toolchain, takes your game files (supplied by hand, or fetched with your own Steam account), and compiles a playable build on your own device.
The tooling is MIT-licensed; see LICENSE. Third-party open-source components shipped in the APK are listed in NOTICE.md, which also records what the APK deliberately does not contain.
You don't need Unity or any game files to build the APK:
make player # once: fetch Unity's Android player module (~642 MB)
make surgery # once: build bundle-surgery
make dev # rebuild, repackage, installRequires an Android SDK, JDK 17+ and the .NET 8 SDK; on Windows use Git Bash.
make docker-apk does the same in a container. See COPILOT.md
for the full development loop.
Settings use separate cards for Display & performance, Cloud saves & backups, Gameplay, and Steam achievements. A live summary shows the selected resolution and FPS. Save directions are explained as Steam → device and device → Steam. Backup export and manual achievement recovery are directly accessible; detailed repair switches and troubleshooting tools expand separately. Switches include short explanations and explicit On/Off labels. Back sits at the top of the scrolling content, without a fixed toolbar strip.
The dashboard Steam button opens an account page. The dashboard and account page show the public Steam persona name, cached per account and refreshed from Steam; the private sign-in identifier is never used as a display-name fallback. Select Disconnected (appear offline), Invisible, or Online. These are persona visibility states, not network switches: saved sign-in, Cloud saves, and achievement synchronization remain available. Offline/Invisible suppress this launcher's games-played announcement. Choices are saved per account and reapplied when its achievement session connects; another Steam client may affect the account's visible state. This is not a privacy control for every type of Steam activity. Sign out at the bottom removes saved credentials and stops the app's achievement session after confirmation, preserving local game files and saves.
QR and password sign-in now request a Steam app ownership ticket for Silksong (App ID 1030300) before accepting the login. The authenticated achievement service also verifies the license before becoming ready for launch, covering saved logins. Manual file selection does not bypass the launch requirement: Play prompts for Steam sign-in if needed. A successful ticket response for the correct App ID with non-empty ticket data is required; local files or a public Steam profile are not used as proof. This verifies Steam-authorized license access, not purchase receipts.
When Steam denies the ownership-ticket request with AccessDenied, the app explains that a valid Steam copy is required and offers the official Silksong Steam store page. This denial alone does not prove that the account never purchased the game. Connection errors, timeouts, and other unconfirmed responses block verification with a retry message instead of claiming the account does not own the game. After buying the game, sign in again. Ticket contents are not stored or logged. Offline launch without verification is no longer supported by this flow.