Fix: Server Broken After the CS 25th Anniversary Update

In November 2023 Valve shipped the 25th Anniversary update to Counter-Strike, and it rippled into CS 1.6: clients updated, some servers stopped accepting them, non-Steam auth broke, and a wave of "my server worked for ten years and died overnight" reports followed. Nothing was corrupted on your box — the client and platform moved, and an old server stack did not. The fix is to bring the stack up to builds that were patched for the change, and, where you cannot, to point clients at the legacy branch.

1. Understand what actually changed for you

The two symptoms that matter to an admin: modern (updated) clients get rejected or crash on connect, and non-Steam authentication stops working. Both come from the same root — the server-side components predate the update and no longer speak to current clients correctly. The maintained projects (the rehlds organisation and the ReGameDLL/Reunion authors) released updated builds for exactly this. Your job is to install them.

Here is the short version of what to touch, in order:

2. Update the engine and game logic

Update in the same order you would install the stack, current release for each:

1. ReHLDS — the engine. Older builds are the most common cause of post-update connection failures.
2. ReGameDLL_CS — keep it paired with ReHLDS from the same era; a mismatched pair crashes on its own.

After each, verify the component actually loaded — rehlds_version and regamedll_version in the console — before moving on, so you know which layer a remaining problem is in.

3. Update Metamod-r, AMXX, and — critically — Reunion

The plugin layer needs to match too:

1. Metamod-r and AMX Mod X — update both; very old AMXX can misbehave against updated clients.
2. Reunion — the biggest single fix for non-Steam breakage. Old Reunion builds do not authenticate updated non-Steam clients. Install a current build per the Reunion guide and keep your existing SteamIdHashSalt (16+ chars) so player ids and bans survive the upgrade. See non-Steam players can't join if they still cannot.

4. The client-side escape hatch: steam_legacy

Some setups — and some players' machines — need the pre-anniversary build. Valve kept it available as the steam_legacy beta branch. A player rolls back by right-clicking Counter-Strike in Steam, Properties → Betas, and selecting steam_legacy from the beta dropdown (no access code required). This is the standard advice for players who cannot connect after updating, and for admins running an old stack they are not ready to migrate immediately.

Understand what it buys you, though: it is a stopgap, not a strategy. Telling every player to switch to steam_legacy shrinks your reachable audience to people willing to pin an old branch, and it does nothing for the non-Steam half of the population. The maintained path — an updated server stack that accepts current clients — is the one that keeps your server open to everyone without asking each visitor to reconfigure Steam. Use the legacy branch to keep the lights on while you do the updates, not as the destination.

Common errors

• Updated ReHLDS but left old ReGameDLL — mismatched pair, crash on round or map change. Update both together; see the incompatibility fix.
• Non-Steam still broken after updating everything else — you did not update Reunion, or its salt is under 16 characters so it did not load.
• Server invisible in the browser after the update — old engines can lose the master too; that is covered in server not in the master list, and updating ReHLDS usually resolves it.
• AMXX plugins throwing errors post-update — recompile against a current AMXX; a handful of old plugins relied on behaviour that shifted.

Verification

Once the stack is updated, test with a current Steam client (not a legacy one) and a current non-Steam client. Both must connect and spawn. In the console confirm the versions:

rehlds_version
regamedll_version
meta list

All three should report current builds with every Metamod plugin at RUN. Watch a full map for connect-time crashes. When a fresh, updated client connects cleanly and non-Steam auth issues distinct ids, you are back on a stack that lives with the anniversary update rather than fighting it.