Synergy

Synergy Team

Released: Oct 3, 2008
Platforms: WindowsLinux
Last updated: 09 Sep 2026, 00:55 GMT

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20 posts

08 Nov 2025Developer post
Rebel Rush 2025
Join us for Synergy's annual Rebel Rush event where we play through the entire Half-Life 2 campaign and its episodes with a significantly increased player limit. The Half-Life Discord will once again be hosting this event. Many performance optimizations have been applied to Syner
Join us for Synergy's annual Rebel Rush event where we play through the entire Half-Life 2 campaign and its episodes with a significantly increased player limit.
The Half-Life Discord will once again be hosting this event. Many performance optimizations have been applied to Synergy since last year's event so we'll be doubling the player limit from 127 to 255!
Synergy's one elusive achievement will be granted after a few minutes of play after the first chapter.
How to participate
First, RSVP if you have Discord so we know how many rebels to expect!
Discord RSVP
On the day of the event, switch to Synergy's rebelrush Steam branch to participate. It will be made publicly available shortly before the event starts.
Right click Synergy in Steam -> Properties -> Betas and switch to the 'rebelrush' branch
After launching the rebelrush version of Synergy, click the Join Rebel Rush 2025 Server button on the main menu.
Since we're pushing the Source Engine to its limits, do expect a few moments of lag and perhaps a crash or two! We've done our best to minimize these inconveniences but there's always more work to do. We'll be hosting the server on a 9950x3D to give it every performance advantage possible.
The event typically lasts about 10 hours.
The server will likely fill up fast but there will be many opportunities to catch a spot throughout the day.
Although the player limit will be set to 255 (including reserved slots), we may artificially lower it in certain sections if performance limitations demand it. We will gradually increase it when we have headroom.
You can switch to a free-cam spectator mode via jointeam 1 in the console (space bar toggles modes).
Keep an eye on the Half-Life Discord Server Announcements page for any moment-to-moment updates during the event.
If you have any questions, feel free to drop by the Half-Life Discord Chat or Synergy Discord Chat. Big thanks to IntriguingTiles and BobWombat for helping make this event possible!
This is a BYOC event (bring your own crowbar). We hope to see you there!
Original post
24 Mar 2025Developer post
Synergy 25.03
d2_coast_08 : Fixed return level change not working. ep2_outland_03 : Fixed vortigaunt not getting on the elevator near the end of the level. ep1_citadel_01 : Fixed missing vortex particle effect on bridge puzzle. Increased voice chat quality by switching to the Steam Voice codec
d2_coast_08: Fixed return level change not working.
ep2_outland_03: Fixed vortigaunt not getting on the elevator near the end of the level.
ep1_citadel_01: Fixed missing vortex particle effect on bridge puzzle.
Increased voice chat quality by switching to the Steam Voice codec by default.
Changed sv_voicecodec default from vaudio_celt to steam and increased buffer sizes.
Fixed annoying combine turret alarm sound getting stuck on in a loop sometimes.
Fixed .lmp files not applying to maps for patched entity data. Mainly applies to ep1 and ep2.
Fixed net_graph sometimes not rendering large packets.
Fixed prop_combine_ball consuming a lot of network bandwidth on citadel maps.
Fixed Strider and Antlion Worker gibs in ep2 not simulating correctly.
Other players now will fade when too close the camera. cl_player_fadedist_*
Issue Tracker
Discord
Original post
01 Jan 2025Developer post
24.12.2 Update
General Updates Fixed player ragdolls not rendering. Fixed vote menu map list being empty (backported to 24.12.1) Fixed crash on player spawn on Linux servers (backported to 24.12.1) Fixed "Failed to prepare map" error dialog on custom maps downloaded from server. showtriggers_to
General Updates

Fixed player ragdolls not rendering.
Fixed vote menu map list being empty (backported to 24.12.1)
Fixed crash on player spawn on Linux servers (backported to 24.12.1)
Fixed "Failed to prepare map" error dialog on custom maps downloaded from server.
showtriggers_toggle can now only be ran from the server.
d2_coast_10: Removed black screen fade when someone falls into the water.
Updated all Half-Life 2 EDT files to be more robust in the face of future Half-Life 2 map updates (Thanks Balim)
Steam Networking: Phase II
Game Client
The Synergy game client will now connect to all internet servers using the Steam Datagram Relay (SDR) by default.
This will:
Keep your IP address hidden from servers you connect to.
Encrypt all server network traffic (incoming and outgoing).
Possibly lower ping times.
Connecting to a server via a LAN IP address will remain unchanged. It will always connect via local IP directly and bypass the SDR as it would otherwise increase ping times by going over the internet instead of staying within the LAN. However, connecting to a server on the LAN via a SteamID (e.g. connect ) will use the SDR.
If you wish to instead connect to servers with your IP address (how it worked before) then disable this ConVar:
cl_sdr_prefer 0cl_sdr_prefer 0 will not work when trying to connect to a Dedicated Server using an anonymized IP address (see below) or when connecting via a SteamID; the SDR will still be used in those cases.
Dedicated Servers
Synergy Dedicated Servers will now use anonymized IP addresses by default.
This will:

Keep the server's public IP address private.
Remove the requirement to port forward the server to display in the Server Browser.
If you prefer to continue displaying your server's real IP address in the server browser then add the following startup option to keep previous behavior:
-nofakeip
Clients will still attempt to connect via the SDR by default even with -nofakeip. If the server has -nofakeip and the client has cl_sdr_prefer disabled, the connection will not use the SDR - as it worked by default before this update.
Due to a possible Steam bug, servers using an anonymized IP address will not show up in the Steam Client's Server Browser, but it will show up in Synergy's in-game server browser. -nofakeip can be used to workaround this.
Listen Servers
Listen servers are unchanged and will work as they did in the previous update (i.e. connect ). UI updates are still in progress to make playing with Steam friends easier.
Happy New Years!
Issue Tracker
Discord
Original post
17 Dec 2024Developer post
24.12.1 Patch
Added backend support for Steam Networking . Frontend TBD. Fixed additional instances of Anti-virus false positives with synergy.exe and srcds.exe Updated executable icons on Windows. Linux DS: Fixed NPC sounds not playing. Steam Networking (beta) This update includes backend net
Added backend support for Steam Networking. Frontend TBD.
Fixed additional instances of Anti-virus false positives with synergy.exe and srcds.exe
Updated executable icons on Windows.
Linux DS: Fixed NPC sounds not playing.
Steam Networking (beta)
This update includes backend netcode support for Steam Networking. This means you can play Synergy with your friends without the hoster needing to port forward their listen client or dedicated server. UI changes to help facilitate this are currently in progress.
How can I use it now?
Whoever will be hosting the server simply needs to load into a map and provide their SteamID64 to their friends. Type status in the console while loaded into a map to get your SteamID64.
This will be one of the lines printed:
steamid : [A;1;123456789:03210] (01234567890123456)This is your SteamID. The SteamID64 is the one in parentheses: (01234567890123456). Send this to friends who would be connecting to your server.
To connect to a friend's server, type the following into the console given your friend's SteamID64:
connect 01234567890123456This works with dedicated servers as well. When a dedicated server loads a map, it will also provide a game server SteamID64 via the status command. However the game client's Server Browser does not support listing servers via SteamID yet.

Issue Tracker
Discord
Original post
08 Dec 2024Developer post
24.12.0 Patch
Fixed Linux client not launching on some popular distros. Fixed infinite connect loop when connecting to 56.16 servers. Fixed a McAfee AV false positive for synergy.exe and srcds.exe. Fixed MetaMod/SourceMod not working with Synergy on Linux. SM Pull Request (Thanks Balim) Fixed
Fixed Linux client not launching on some popular distros.
Fixed infinite connect loop when connecting to 56.16 servers.
Fixed a McAfee AV false positive for synergy.exe and srcds.exe.
Fixed MetaMod/SourceMod not working with Synergy on Linux.
SM Pull Request (Thanks Balim)
Fixed newer versions of MM/SM not working.
Fixed some additional cases where Synergy would fail to start if you have Source Filmmaker installed.
Fixed workshop items sometimes not mounting on dedicated servers.
d1_canals_03 & d2_coast_01: Fixed progression block at end of level if antirush is enabled.
d3_c17_02: Fixed dog being a bad boy sometimes by closing the gate early.
d2_coast_03: Fixed some visible triggers.

Issue Tracker
Discord
Original post
03 Dec 2024GamingOnLinux
Half-Life 2 co-op mod Synergy upgraded for the Half-Life 2 20th Anniversary Update
Synergy is a free mod for Half-Life 2 that allows you to play the Half-Life 2 series and many other singleplayer Source Mods cooperatively with friends. It was recently upgraded to support the Half-Life 2 20th Anniversary Update. Read the full article here:
29 Nov 2024Developer post
24.11.1 Hotfix
ep2_outland_09 : Fixed softlock on transition from ep2_outland_08 where two rebel NPCs will spawn and block the doorway, preventing progression. d3_c17_07 : Fixed softlock above turret room. d1_canals_13 : Fixed issue where some helicopter sounds would never play . Added support
28 Nov 2024Developer post
Synergy: Half-Life 2's 20th Anniversary Update
Greetings Rebels! Its been a long time. The last official Synergy update was way back in 2015! Over the years we've been working in the `development` branch, which has had a lot of work done to it. Due to the release of Half-Life 2's 20th Anniversary update, we are prompted to re
Greetings Rebels!
Its been a long time. The last official Synergy update was way back in 2015!
Over the years we've been working in the `development` branch, which has had a lot of work done to it.
Due to the release of Half-Life 2's 20th Anniversary update, we are prompted to release this sooner than we've planned as to resolve numerous breaking changes from Half-Life 2's recent large update.
We're happy to announce that Half-Life 2's 20th Anniversary Update is now supported and we thank you for your patience.
Patch Notes

Support for the Half-Life 2 20th Anniversary Update!
Fixed numerous crashes like the infamous "unconnected" player bug and player models jittering.
Significantly improved overall performance, especially with large player counts.
Rebalanced numerous, rather absurd, map-specific difficulty spikes in the Half-Life 2 campaign.
Fixed SteamVR starting when changing settings.
Initial official native support for Steamdeck (UI still leaves a lot to be desired).
Fixed various HUD issues introduced by Half-Life 2's Steamdeck update.
Official support for Linux Dedicated Servers.

Requires steam client installed (e.g. `sudo apt install steam`).
Added support for saved games.

Host can load a saved game and friends who join will be restored if they were connected at the time of the save.
Works on dedicated servers.
Various map-specific (EDT) improvements throughout the Half-Life 2 campaigns.
Fixed many level transition issues, particularly on backtracking maps.
Steam Cloud support for settings and saved games.
Steam Workshop support for dedicated servers.
Steam Rich Presence support.
Enabled spectator mode via console (jointeam 1)
Players will spawn in a vehicle on airboat levels (coast levels TBD).
Vehicles will no longer stop when the game autosaves.
Added more player voice command lines from ep1.
Fixed player viewmodels being invisible under some circumstances.
Optimized networking for some entities like the Airboat.
'Use' key will now go through players to avoid blocking anything.
Removed cheat flag from some useful commands/cvars.
Added game content rating to unblock Synergy in Germany.
Increased maximum player support from 10 to 32.
Other changes lost in time.
Previous Version
If you run into any regressions from the previous version (56.16) or bugs in general, please report them to our public issue tracker. Also feel free to make some noise on our Discord.
The previous version of Synergy is still available on its own Steam beta branch: `56.16`. Please report a bug if you feel the need to rollback. If you do rollback, also set Half-Life 2's beta to `steam_legacy` to make everything work as it did before Half-Life 2's 20th Anniversary update.
Our Next Steps
One feature we were planning to have complete before releasing this update was automatic networking and Steam friend lobbies. This feature would remove the requirement of the host needing to port forward their local (or dedicated) server so their friends can join. This has been a large hindrance for those who simply want to play Half-Life 2 with friends out of the box and not deal with troubleshooting networks. Such a feature is a very high priority to us and we hope to have it ready in the near future.
There are likely other issues introduced in the Half-Life 2 20th Anniversary Update so we're keeping an eye on those as well.
Special thanks to IntriguingTiles, Balim and modi for helping with testing, reporting and fixing various issues over the last several months.
There is still much work to do but thanks for raising your crowbars with us over the years and we hope to see you again in City 17!
Original post
16 Nov 2024Developer post
Rebel Rush Event
Half Life Discord and Synergy Discord are running a Rebel Rush Event Today, Take a look at your server list and filter by most players to easily find the "Rebel Rush" Labeled Servers The Servers also do include the Synergy Rebel Rush Achievement. For more information join the Syn
22 Mar 2020Developer post
Rebel Rush: HL Discord
The HL Discord peeps are hosting a Synergy server in celebration before Half-Life: Alyx's release. Switch to the "twitch" beta branch to join! Steam->Synergy->Properties->Betas Tab-> twitch Prepare for #BugFest2020 #Lagfest2020 Play through Half-Life 2/Lost coast/Ep1/
25 Feb 2018Developer post
Synergy stuff/info & Discord
Hey for keeping in touch, Discord link below. Going to annoy our current programmer who is hard at work @ his fancy job now this week hopefully to get Rebel Rush going soon or an alternative way of doing so. I know the "cheevo" hunters out there want this badly but haven't had th
25 Feb 2018Developer post
Synergy stuff/info & Discord
Hey for keeping in touch, Discord link below. Going to annoy our current programmer who is hard at work @ his fancy job now this week hopefully to get Rebel Rush going soon or an alternative way of doing so. I know the "cheevo" hunters out there want this badly but haven't had th
21 Aug 2017Developer post
Community Play, 64 MaxPlayers - Testing for rebelrush
This may be a very bumpy ride to test out the development branch of synergy We are currently having some rebel rush tests going on right now. i'd like to try some beta-tests with no achievements that way the day the "Rebel Rush" event does happen we can all play as smoothly as po
21 Aug 2017Developer post
Community Play, 64 MaxPlayers - Testing for rebelrush
This may be a very bumpy ride to test out the development branch of synergy We are currently having some rebel rush tests going on right now. i'd like to try some beta-tests with no achievements that way the day the "Rebel Rush" event does happen we can all play as smoothly as po
17 Aug 2017Developer post
UPDATE - Secret Development Build / Twitch
Try the development beta! First off thank you for checking this out. Once again sorry for interrupting with a mini window on your side there. The latest development of synergy is included in a secret build that you'll have to do an OPT-IN through the Synergy properties. Instructi
17 Aug 2017Developer post
UPDATE - Secret Development Build / Twitch
Try the development beta! First off thank you for checking this out. Once again sorry for interrupting with a mini window on your side there. The latest development of synergy is included in a secret build that you'll have to do an OPT-IN through the Synergy properties. Instructi
15 Aug 2017Developer post
Community Play - Synergy
2 Synergy Developers Play Synergy HL2 all the way through. Come join us on twitch or in-game Waiting on answers from other Devs for the Rebel Rush Schedule. Incase you wanted to know about that instead. So unfortunately I don't have an answer yet.
15 Aug 2017Developer post
Community Play - Synergy
2 Synergy Developers Play Synergy HL2 all the way through. Come join us on twitch or in-game Waiting on answers from other Devs for the Rebel Rush Schedule. Incase you wanted to know about that instead. So unfortunately I don't have an answer yet.
09 Aug 2017Developer post
Synergy Stream : JonnyQuattro plays with community
In efforts to publicize Hard-Life and Synergy at the same time. I'll be hosting on twitch right now. I am not a good streamer but I will try answering questions as well as playing on the official synergy servers. Join if you'd like (Maybe in hopes of scheduling the next Rebel Rus
09 Aug 2017Developer post
Synergy Stream : JonnyQuattro plays with community
In efforts to publicize Hard-Life and Synergy at the same time. I'll be hosting on twitch right now. I am not a good streamer but I will try answering questions as well as playing on the official synergy servers. Join if you'd like (Maybe in hopes of scheduling the next Rebel Rus