Released May 15, 2020
Early Access $15.99 · −20% Mostly Positive
Cepheus Protocol
By Halcyon Winds
Followers
—
Reviews
3,002
Mostly Positive
Players yesterday
20
at the busiest moment
Owners
200K–500K
estimated
Steam data
Everything Steam lists for Cepheus Protocol · record updated 1 day ago
Overview
App ID979640
Release dateMay 15, 2020
Last change number40106532
Last record update1 day ago
App info
- App type
- Game
- Developer
- Halcyon Winds
- Publisher
- Halcyon Winds
- Steam profile
- Counts toward game count and achievement totals · checked Nov 1, 2025
- Franchise
- Cepheus Protocol
- Website
- cepheusprotocol.com
Platforms
Windows
64-bit
- Steam Deck
- Playable
- Controller
- Partial support
Features
12
Single-playerSteam CloudSteam AchievementsRemote Play TogetherSteam WorkshopSteam Trading CardsPartial controller supportMulti-playerCo-opOnline co-opMMOFamily Sharing
Related apps
Patches
Builds
4| Build | Branch | Updated |
|---|---|---|
| 26101149 | experimental | Oct 21, 2026 |
| 24829887 | public | Aug 20, 2026 |
| 20415865 | legacy | Jan 7, 2026 |
| 15464740 | legacy-premerge | Aug 31, 2025 |
Packages & DLC
DLCs
7Depots
Depots
10| ID | Name | Systems | Size | Download | Manifest |
|---|---|---|---|---|---|
| 228989 | — shared from 228980 | Windows | — | — | — |
| 228990 | — shared from 228980 | Windows | — | — | — |
| 979641 | — | Windows | 11.22 GB | 10.32 GB | 8190979047784837192 |
| 1387390 | — DLC 1387390 | All | 1.0 MB | 891.4 KB | 1286529532299846223 |
| 1997150 | — DLC 1997150 | All | 11.3 MB | 10.6 MB | 2646314920170677226 |
| 2496500 | — DLC 2496500 | Windows | 1.1 MB | 1.1 MB | 7113364543456853873 |
| 2496510 | — DLC 2496510 | Windows | 756.4 KB | 752.2 KB | 8725575257045246761 |
| 2496520 | — DLC 2496520 | All | 123.7 KB | 105.0 KB | 3007699981174887082 |
| 2514440 | — DLC 2514440 | Windows | 10.6 KB | 3.2 KB | 5343426092076636058 |
| 2540710 | — DLC 2540710 | All | 489.2 KB | 427.8 KB | 7374174257502697085 |
Branches
4| Branch | Build | Updated | Access |
|---|---|---|---|
| public | 24829887 | Aug 20, 2026 | Open |
| experimental Preview build with new features. Unstable, frequent updates, saves may break. | 26101149 | Oct 21, 2026 | Open |
| legacy The branch before we merged the rebuilt game as default on 1.6.25 | 20415865 | Jan 7, 2026 | Open |
| legacy-premerge Build from before experimental was merged into the live branch. | 15464740 | Aug 31, 2025 | Open |
Configuration
Install foldersteamapps/common/Cepheus Protocol
Launch options
4| Executable | Arguments | Systems | Description |
|---|---|---|---|
| CepheusProtocol.exe | Windows · 64-bit | Default | |
| CepheusLauncher.App.exe | Windows · 64-bit | Launcher | |
| CepheusProtocol.exe | Windows · 64-bit | Without Launcher | |
| CepheusProtocol\Mods\ModUploader.exe | Windows · 64-bit | Upload Workshop Mod |
Cloud saves
Space per player7.45 GB
Filesup to 5,000
Save locations2
| Root | Path | Pattern | Systems |
|---|---|---|---|
| WinAppDataLocal | CepheusProtocol/Saved/SaveGames | *.sav | All |
| gameinstall | CepheusProtocol/Saved/SaveGames | *.sav | All |
Data from public Steam pages, updated daily; 1 day of history. Owner counts are estimates. LaunchRivals is not affiliated with Valve or Steam.