Nightly 2.0.26 (70e9d639b)

What's Changed

• fix(ci): publish Linux release as .zip instead of .tar.gz in #114
• macOS build and CI in #117
• fix(ci): bundle MSVC x64 CRT so nightly runs without VC++ Redistributable in #118
• fix(coop): allow personnel hire when SHARED base stores full in #119
• fix(coop): serve the client on a mid-battle campaign resume in #120
• fix(coop): host re-validate craft capacity in SHARED (#121) in #123
• fix(coop): stop SHARED in-battle soldier gift from duplicating roster (#126) in #128
• fix(coop): BasescapeState double-free crash after mission (#124) in #130
• fix(coop-test): stop test_ufo_notice gating on best-effort UFO detection propagation (#129) in #135
• fix(ci): consolidate install + data-copy instructions into HOW_TO_RUN.txt on all platforms (#137) in #138
• fix(coop): make hotseat startable from New Battle; retire dead menu flows (#136) in #139
• fix(coop): sync door-open actions from BA_NONE turn packets in #145
• fix(ci): add package-tree assertions to all four platform builds in #146
• feat: list missing mods in ConfirmLoadState dialog in #148
• feat(coop): PvP campaign and skirmish mode (win/lose, role-aware sim, stub blob, honest tests) in #151
• fix(coop): SHARED auto-end crash-site finishBattle stack underflow in #154
• Added password label to PasswordCheckMenu in #153
• feat(coop): teal-split exe icon for coop mod in #156
• Fix separate campaign maintenance costs in #158
• fix(coop-test): de-flake test_pvp_campaign_ufo_spawn (accumulate UFO sightings) in #160

Full Changelog: v2.0.6...nightly

v2.0.6

A maintenance release on top of 2.0.0: the Linux download is a self-contained
AppImage again, plus two co-op crash fixes and clearer soldier-arrival alerts.

Fixed

• The Linux download is a self-contained AppImage again (as in v1.8.4) instead
  of a bare dynamically-linked binary, so it no longer needs matching system
  SDL libraries or a new-enough glibc to start. Built on an older base (glibc
  2.31) for broad distro support. Run OpenXcoop-x86_64.AppImage from the
  extracted folder, next to the data folders (see the bundled HOW_TO_RUN.txt).
• Fixed a crash at the end of the month when one of your bases came under
  attack in a co-op game.
• Fixed a crash for the second player when ordered soldiers arrived at a base
  in SHARED mode. Soldier-arrival alerts now list every incoming soldier for
  both players and label each with its owner's name.

v2.0.0

A brand-new SHARED campaign mode, host-authoritative saving, an automatic
save upgrader, in-game voting, and a long list of desync, crash and item-loss
fixes. Windows x64, Windows XP (32-bit) and Linux packages now ship together
with every release.

Added

• SHARED co-op campaign: a second co-op mode where both players run one
  world together: shared bases, funds, research, manufacturing and craft.
  Either player can command any craft, fly interceptions and dogfights, and a
  battle can mix soldiers from both players in a single squad. The campaign
  type is chosen at NEW GAME (Solo / Co-op (Separate) / Co-op (Shared)).
• Save upgrader: saves from older versions (including legacy v1.8.4 co-op
  saves) are detected on load and upgraded in-game, step by step, to the
  current format.
• Host-authoritative saving: the host's save now embeds the client's
  world, making it the single authority for both players' campaigns; clients
  resume straight from the host's copy.
• Multiplayer voting — in-game vote dialogs (for example, voting to abort
  a battle), with matching lobby improvements.
• Clipboard paste — text fields accept paste (Ctrl+V) on Windows and Linux.
• Skirmish co-op lobby — NEW BATTLE co-op is redesigned around a
  host-driven lobby with a BATTLE SETTINGS screen and a join popup shown over
  the lobby; battles in progress can be rejoined.
• Soldier gifting and transfers — gift soldiers to the other player
  (optionally with their gear), including a reworked in-battle gifting flow.
• Server browser — the server list can aggregate multiple rendezvous
  servers.
• Geoscape ally indicator — your partner's activities and time-step are
  shown in the geoscape so it's easier to coordinate fast-forwarding.
• Off-turn scanner and soldier-direction indicators in battle while it is not
  your turn.
• Crash reporting — crash logs are actionable and minidumps are written
  next to them.
• Text labels in the Add Server menu and a Hotseat tooltip in the Host menu.

Changed

• The neutral side in battle is reported as "Outsiders Activity" instead of
  "Alien Activity".
• The main menu shows a readable version block (coop version plus the OXCE
  engine version), and official releases drop the channel suffix.
• Automatic "nightly" builds with every git commit, making bugfix iteration
  easier.
• Due to the new host-authoritative save architecture, all players are required
  in-game for a game to be able to progress, and players cannot join a
  campaign late. The player set is determined at campaign start, and cannot
  be modified.
• Games are paused while any client is disconnected to prevent desync.

Fixed

• Geoscape sync no longer floods the connection: position updates ride a
  conflation slot, packet queues are thread-safe, and the "TX queue
  full" / multi-second-ping stalls are gone.
• Purchases and transfers between players: fixed a use-after-free when
  transferring a craft with crew; the receiver validates the target base
  before acknowledging, so goods are no longer silently lost; restored the
  dropped transfer notification; a transfer can no longer be applied twice;
  and a client's out-craft keeps its co-op destination across a host save.
• Battlescape item sync: battles no longer lose or duplicate items across
  machines, and a proximity-grenade blast no longer sweeps every loose item
  off the other player's floor.
• Returning to the main menu tears the co-op session down cleanly, fixing
  crashes and palette corruption after leaving a battle.
• SHARED mode: mission sites and waypoints keep a consistent lifecycle on
  both machines, and UFO/mission detection stays in parity.
• SEPARATE mode: duplicate mission ids are de-duplicated at the snapshot
  sender.
• Chryssalid zombies no longer double-spawn in co-op battles.
• The cursor no longer misbehaves/gets stuck in "aim mode" during the
  other player's turn.
• Craft status stays in sync between players.
• Password-protected lobbies can be joined — and left — cleanly.
• Co-op menu entry points no longer crash when no save is active.
• Fixed a crash when unloading a weapon at a base.

OpenXcom Co-op Mod v1.5.0 – Windows XP SP3 32-bit build

Windows XP SP3 (32-bit) build. This version has not been tested and may not work or launch. Please report any issues you encounter.

OpenXcom Co-op Mod v1.0.0 – Full Release (Windows)

Changelog 2025/12/30

1. Improved research sync, the other player now gets the same research popup, and research projects update instantly without needing to reload a save.
2. Added base facility sync, when one player builds or removes a facility, the change updates instantly for the other player when viewing that base. No need to go to the Geoscape and back to see the changes.
3. Alien base markers are now synced on the Geoscape.
4. Fixed mission sites, so they should no longer disappear for the other player (syncs when both players are in Geoscape).
5. If a player shoots down a UFO over water, it is now destroyed on impact and will not crash and create a mission.
6. Fixed a Battlescape sync issue where throwing an item could sometimes end up on the wrong tile.
7. Improved tile damage sync so tiles like walls and doors now get destroyed in exactly the same way on both players. Before, if you fired a rocket and it hit a wall, the damage could be different for the other player, would not sync, and could break pathfinding.
8. Fixed an issue where a soldier sometimes would not shoot while berserk.
9. Fixed soldiers disappearing in the new battle menu after ending a mission.
10. If you lose a base defense mission, it no longer counts the other player’s base, so the game will not continue if you lose your last base.
11. Units that are on fire should now sync in Battlescape, tested with The X-Com Files.
12. Fixed Battlescape sync issues when a unit was turning or opening a door.
13. Added multiplayer option "Enable XCOM Equipment for Aliens in PvP".
14. Other small fixes and improvements.

OpenXcom Co-op Mod v1.0.0 – Full Release (Linux)

Changelog 2025/12/30

1. Improved research sync, the other player now gets the same research popup, and research projects update instantly without needing to reload a save.
2. Added base facility sync, when one player builds or removes a facility, the change updates instantly for the other player when viewing that base. No need to go to the Geoscape and back to see the changes.
3. Alien base markers are now synced on the Geoscape.
4. Fixed mission sites, so they should no longer disappear for the other player (syncs when both players are in Geoscape).
5. If a player shoots down a UFO over water, it is now destroyed on impact and will not crash and create a mission.
6. Fixed a Battlescape sync issue where throwing an item could sometimes end up on the wrong tile.
7. Improved tile damage sync so tiles like walls and doors now get destroyed in exactly the same way on both players. Before, if you fired a rocket and it hit a wall, the damage could be different for the other player, would not sync, and could break pathfinding.
8. Fixed an issue where a soldier sometimes would not shoot while berserk.
9. Fixed soldiers disappearing in the new battle menu after ending a mission.
10. If you lose a base defense mission, it no longer counts the other player’s base, so the game will not continue if you lose your last base.
11. Units that are on fire should now sync in Battlescape, tested with The X-Com Files.
12. Fixed Battlescape sync issues when a unit was turning or opening a door.
13. Added multiplayer option "Enable XCOM Equipment for Aliens in PvP".
14. Other small fixes and improvements.

OpenXcom Co-op Mod v1.35.0b – Beta Release (Windows)

1. Geoscape now syncs from host to the client for funding countries, UFO activity, and XCOM activity. The Graphs menu and Funding menu should now look almost the same for both players.
2. Monthly Report is now synced from host to the client, including income, monthly score, happy list, sad list, and more. Monthly score now matches singleplayer with less negative scoring. Maintenance and balance belong to each player, so they are not synced.
3. Improved other player craft syncing, including shield, craft name, vehicle count, soldier count, and more.
4. Reworked time sync. To speed up time, both players must be in Geoscape and select the same time speed button. Game progression should now work correctly on the client.
5. If either player selects a different time speed in Geoscape, both players are forced to 5 seconds time speed. The multiplayer option host-only time speed control still requires both players to be in Geoscape.
6. Fixed an issue where a network loss after ending a mission could leave old soldiers in the host save and break later Battlescape missions. When both players are connected again, the game now automatically repairs the save for both players.
7. Battlescape PvP Mind Control issues should now be fixed, including crashes and unit selection problems.
8. Battlescape PvP footstep sound issues should now be fixed.
9. Added a multiplayer setting to disable other player footstep sounds.
10. Added a multiplayer setting to disable reaction fire in PvP.
11. Battlescape PvP added FACTION_NEUTRAL unit AI logic. FACTION_HOSTILE units can reaction fire at moving FACTION_NEUTRAL units unless reaction fire is disabled in multiplayer settings.
12. Battlescape melee attack sync issues with Chryssalid conversions should now be fixed. Zombies and the later Chryssalid transformation should now sync correctly.

OpenXcom Co-op Mod v1.35.0b – Beta Release (Linux)

1. Geoscape now syncs from host to the client for funding countries, UFO activity, and XCOM activity. The Graphs menu and Funding menu should now look almost the same for both players.
2. Monthly Report is now synced from host to the client, including income, monthly score, happy list, sad list, and more. Monthly score now matches singleplayer with less negative scoring. Maintenance and balance belong to each player, so they are not synced.
3. Improved other player craft syncing, including shield, craft name, vehicle count, soldier count, and more.
4. Reworked time sync. To speed up time, both players must be in Geoscape and select the same time speed button. Game progression should now work correctly on the client.
5. If either player selects a different time speed in Geoscape, both players are forced to 5 seconds time speed. The multiplayer option host-only time speed control still requires both players to be in Geoscape.
6. Fixed an issue where a network loss after ending a mission could leave old soldiers in the host save and break later Battlescape missions. When both players are connected again, the game now automatically repairs the save for both players.
7. Battlescape PvP Mind Control issues should now be fixed, including crashes and unit selection problems.
8. Battlescape PvP footstep sound issues should now be fixed.
9. Added a multiplayer setting to disable other player footstep sounds.
10. Added a multiplayer setting to disable reaction fire in PvP.
11. Battlescape PvP added FACTION_NEUTRAL unit AI logic. FACTION_HOSTILE units can reaction fire at moving FACTION_NEUTRAL units unless reaction fire is disabled in multiplayer settings.
12. Battlescape melee attack sync issues with Chryssalid conversions should now be fixed. Zombies and the later Chryssalid transformation should now sync correctly.

OpenXcom Co-op Mod v1.31.0 – Beta Release

Changelog 2025/11/01

During the past month, synchronization across the Battlescape has been reworked almost completely. AI synchronization is still in progress, so a few issues may remain and will be fixed later.

Shooting, movement, and death now synchronize much more reliably between players. Previously a shot could hit the UFO for one player but miss for the other, or an XCOM soldier could appear alive for one player but dead for the other. This “ghost soldier” problem has been fixed.

Projectile coordinates now synchronize to ensure that hits register the same way for everyone. Tile damage is synchronized as well. Panic and berserk states are synchronized so units walk to the correct tile and can drop their weapon correctly.

The issue where units did not move anywhere when path preview was enabled has been fixed.

The host now fully controls the client during AI turns, and the client no longer runs its own logic. This eliminates cases where units teleported or moved incorrectly.

In PvP the opponent no longer hears footsteps when a player is sneaking. The end-of-battle screen has been corrected. If the UFO side wins it shows Craft Lost, and if XCOM wins it shows UFO is recovered.

The settings menu now includes a Multiplayer options section. You can set a key to open chat and allow research synchronization in campaign mode. Many players have felt research synchronization is too strong, so it is now a setting. More options may be added later.

Some players experienced melee attacks and shots always missing. This was caused by random generator synchronization happening at the wrong time. That synchronization has been removed, and the random generator now behaves the same way as in the original X-COM.

Next we will continue improving AI synchronization and show the end turn screen on the client. Our goal is to keep multiplayer changes as close as possible to the original X-COM behavior.

OpenXcom Co-op Mod v1.30.0 – Beta Release

Changelog 2025/10/11

1. Fixed an issue where duplicate unit IDs could assign positions and items to the wrong unit, causing sync errors. You need to abort the mission and start a new one for the fix to take effect. You do not need to start a new campaign.

2. Fixed MonthlyReport not appearing for the second player

3. Fixed UFOs sometimes not appearing and crashing the game

4. PVP campaign removed message STR_UNABLE_TO_USE_ALIEN_ARTIFACT_UNTIL_RESEARCHED and UFOs can now fire weapons

5. Settings General added Toggle Chat option with a configurable hotkey

6. PVP Battlescape fixed issue where the other player could see unit arrows when holding Alt

7. Minor fixes and polish