diff --git a/.github/CONTRIBUTING.md b/.github/CONTRIBUTING.md
index c2912e0af5..54178ff953 100644
--- a/.github/CONTRIBUTING.md
+++ b/.github/CONTRIBUTING.md
@@ -51,6 +51,8 @@ You must also have the following environment variables set. To run them more acc
 - `TGS_TEST_CONNECTION_STRING`: To a valid database connection string. You can use the setup wizard to create one.
 - (Optional) `TGS_TEST_GITHUB_TOKEN`: A GitHub personal access token with no scopes used to bypass rate limits.
 - (Optional) `TGS_TEST_BYOND_ZIP_DOWNLOAD_TEMPLATE`: Template URL for downloading BYOND zip files from a non-official mirror.
+- (Optional) `TGS_TEST_BYOND_MIRROR_VERSION_TXT`: version.txt for a BYOND zip mirror. Requires `TGS_TEST_BYOND_ZIP_DOWNLOAD_TEMPLATE`.
+- (Optional) `TGS_TEST_BYOND_ZIPS_BASE_PATH`: Directory on disk to cache BYOND zip files.
 - (Optional) The following variables are all interdependent, so if one is set they all must be.
   - `TGS_TEST_DISCORD_TOKEN`: To a valid discord bot token.
   - `TGS_TEST_DISCORD_CHANNEL`: To a valid discord channel ID that the above bot can access.
diff --git a/.github/workflows/ci-pipeline.yml b/.github/workflows/ci-pipeline.yml
index 9f9c9a5010..0e098dc503 100644
--- a/.github/workflows/ci-pipeline.yml
+++ b/.github/workflows/ci-pipeline.yml
@@ -42,6 +42,8 @@ env:
   TGS_NODE_VERSION: 20.x
   TGS_TEST_GITHUB_TOKEN: ${{ secrets.LIVE_TESTS_TOKEN }}
   PACKAGING_PRIVATE_KEY_PASSPHRASE: ${{ secrets.PACKAGING_PRIVATE_KEY_PASSPHRASE }}
+  TGS_TEST_BYOND_ZIP_DOWNLOAD_TEMPLATE: https://mocha.affectedarc07.co.uk/tgs_byond_mirrors/${Major}.${Minor}_byond${Linux:_linux}.zip
+  TGS_TEST_BYOND_MIRROR_VERSION_TXT: https://mocha.affectedarc07.co.uk/tgs_byond_mirrors/version.txt
 
 concurrency:
   group: "ci-${{ (github.event_name != 'push' && github.event_name != 'schedule' && github.event.inputs.pull_request_number) || github.run_id }}-${{ github.event_name }}"
diff --git a/tests/Tgstation.Server.Tests/CachingFileDownloader.cs b/tests/Tgstation.Server.Tests/CachingFileDownloader.cs
index 8fccd1234c..f2897cf808 100644
--- a/tests/Tgstation.Server.Tests/CachingFileDownloader.cs
+++ b/tests/Tgstation.Server.Tests/CachingFileDownloader.cs
@@ -92,15 +92,21 @@ namespace Tgstation.Server.Tests
 
 			var url = ByondInstallerBase.GetDownloadZipUrl(byondVersion, urlTemplate, new PlatformIdentifier().IsWindows ? "Windows" : "Linux");
 			string path = null;
-			if (TestingUtils.RunningInGitHubActions)
+			string basePath = Environment.GetEnvironmentVariable("TGS_TEST_BYOND_ZIPS_BASE_PATH");
+			if (basePath == null && TestingUtils.RunningInGitHubActions)
 			{
-				// actions is supposed to cache BYOND for us
-
-				var dir = Path.Combine(
+				// actions is supposed to cache BYOND for us here
+				basePath = Path.Combine(
 					Environment.GetFolderPath(
 						Environment.SpecialFolder.UserProfile,
 						Environment.SpecialFolderOption.DoNotVerify),
-					"byond-zips-cache",
+					"byond-zips-cache");
+			}
+
+			if (basePath != null)
+			{
+				var dir = Path.Combine(
+					basePath,
 					"live",
 					windows ? "windows" : "linux");
 				path = Path.Combine(
@@ -109,15 +115,23 @@ namespace Tgstation.Server.Tests
 					$"{version.Version.Major}.{version.Version.Minor}.zip");
 			}
 
+			Uri overrideUrl = null;
+			if (urlCacheOverrideTemplate != null)
+			{
+				overrideUrl = url;
+				url = ByondInstallerBase.GetDownloadZipUrl(byondVersion, urlCacheOverrideTemplate, new PlatformIdentifier().IsWindows ? "Windows" : "Linux");
+			}
+
 			await (await CacheFile(
 				logger,
-				urlCacheOverrideTemplate != null
-					? ByondInstallerBase.GetDownloadZipUrl(byondVersion, urlCacheOverrideTemplate, new PlatformIdentifier().IsWindows ? "Windows" : "Linux")
-					: url,
+				url,
 				null,
 				path,
 				cancellationToken))
 				.DisposeAsync();
+
+			if (overrideUrl != null)
+				cachedPaths[overrideUrl.ToString()] = cachedPaths[url.ToString()];
 		}
 
 		public static void Cleanup()
diff --git a/tests/Tgstation.Server.Tests/Live/TestLiveServer.cs b/tests/Tgstation.Server.Tests/Live/TestLiveServer.cs
index 7eeec04af3..61013ea17e 100644
--- a/tests/Tgstation.Server.Tests/Live/TestLiveServer.cs
+++ b/tests/Tgstation.Server.Tests/Live/TestLiveServer.cs
@@ -1626,6 +1626,16 @@ namespace Tgstation.Server.Tests.Live
 						if (openDreamOnly)
 							return;
 
+						var windowsMinCompat = new Version(510, 1346);
+						var linuxMinCompat = new Version(512, 1451); // http://www.byond.com/forum/?forum=5&command=search&scope=local&text=resolved%3a512.1451
+						await CachingFileDownloader.InitializeByondVersion(
+							GetLogger(),
+							new PlatformIdentifier().IsWindows
+								? windowsMinCompat
+								: linuxMinCompat,
+							new PlatformIdentifier().IsWindows,
+							cancellationToken);
+
 						var compatTests = FailFast(
 							instanceTest
 								.RunCompatTests(
@@ -1633,8 +1643,8 @@ namespace Tgstation.Server.Tests.Live
 									{
 										Engine = EngineType.Byond,
 										Version = new PlatformIdentifier().IsWindows
-											? new Version(510, 1346)
-											: new Version(512, 1451) // http://www.byond.com/forum/?forum=5&command=search&scope=local&text=resolved%3a512.1451
+											? windowsMinCompat
+											: linuxMinCompat,
 									},
 									server.OpenDreamUrl,
 									firstAdminRestClient.Instances.CreateClient(compatInstance),
diff --git a/tests/Tgstation.Server.Tests/TestingUtils.cs b/tests/Tgstation.Server.Tests/TestingUtils.cs
index 9cc11f7966..40925352dd 100644
--- a/tests/Tgstation.Server.Tests/TestingUtils.cs
+++ b/tests/Tgstation.Server.Tests/TestingUtils.cs
@@ -136,7 +136,7 @@ namespace Tgstation.Server.Tests
 				const string DefaultMirror = "https://www.byond.com/download/version.txt";
 				edgeVersion = await GetVersionFromResponse(DefaultMirror);
 
-				logger.LogInformation("Downloading edge version from BYOND.com");
+				logger.LogInformation("Downloading edge version from BYOND.com {edge}", edgeVersion);
 
 				// if we got the result from byond.com, make sure the cache grabs the zip from there as well
 				await CachingFileDownloader.InitializeByondVersion(logger, Version.Parse(edgeVersion), new PlatformIdentifier().IsWindows, cancellationToken, GeneralConfiguration.DefaultByondZipDownloadTemplate);