Merge pull request #2310 from tgstation/Omega [TGSDeploy]

v6.18.0: Merging way too many things at once
2026-08-24 05:27:30 +01:00 · 2025-07-27 13:30:05 -04:00
parent e40dbdfb0e 0d4d68d736
commit 6f5a2f6f6b
76 changed files with 1019 additions and 462 deletions
@@ -50,6 +50,9 @@ You must also have the following environment variables set. To run them more acc
 - `TGS_TEST_DATABASE_TYPE`: `MySql`, `MariaDB`, `PostgresSql`, or `SqlServer`.
 - `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.
@@ -42,6 +42,9 @@ 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
+  DMAPI_BYOND_BUILD_MIRROR_DOWNLOAD_TEMPLATE: https://mocha.affectedarc07.co.uk/tgs_byond_mirrors/${FULL_VERSION}_byond_linux.zip # Available vars are $BYOND_MAJOR (i.e. 516) and $FULL_VERSION (i.e. 516.1666)

 concurrency:
  group: "ci-${{ (github.event_name != 'push' && github.event_name != 'schedule' && github.event.inputs.pull_request_number) || github.run_id }}-${{ github.event_name }}"
@@ -90,6 +93,56 @@ jobs:
          name: release_notes_bins
          path: ./release_notes_bins/

+  validate-nix-flake:
+    name: Validate Nix Flake
+    needs: start-gate
+    runs-on: ubuntu-latest
+    env:
+      TEST_TGS_VERSION: "6.17.0" # Version we use here doesn't matter as it won't be executed. Just used to download a zip and calc hash
+    steps:
+      - name: Install Native Packages # Name checked in rerunFlakyTests.js
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y xmlstarlet
+
+      - name: Setup Nix
+        uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=channel:nixos-unstable
+
+      - name: Checkout (Branch)
+        uses: actions/checkout@v4
+        if: github.event_name == 'push' || github.event_name == 'schedule'
+
+      - name: Checkout (PR Merge)
+        uses: actions/checkout@v4
+        if: github.event_name != 'push' && github.event_name != 'schedule'
+        with:
+          ref: "refs/pull/${{ inputs.pull_request_number }}/merge"
+
+      - name: Replace current TGS version with test version
+        run: |
+          CURRENT_TGS_VERSION="$(xmlstarlet sel -N X="http://schemas.microsoft.com/developer/msbuild/2003" --template --value-of /X:Project/X:PropertyGroup/X:TgsCoreVersion build/Version.props)"
+          sed -i -e "s/<TgsCoreVersion>${CURRENT_TGS_VERSION}/<TgsCoreVersion>${{ env.TEST_TGS_VERSION }}/g" build/Version.props
+
+      - name: Retrieve ServerConsole.zip Artifact
+        run: |
+          mkdir release
+          curl -L https://github.com/tgstation/tgstation-server/releases/download/tgstation-server-v${{ env.TEST_TGS_VERSION }}/ServerConsole.zip -f -o release/ServerConsole.zip
+
+      - name: Regenerate Nix Hash
+        run: |
+          nix hash path ./release > build/package/nix/ServerConsole.sha256
+          cat build/package/nix/ServerConsole.sha256
+
+      - name: Cleanup Download
+        run: rm -rf ./release
+
+      - name: Check Flake
+        run: |
+          cd build/package/nix
+          nix flake check
+
  code-scanning:
    name: Run CodeQL
    needs: start-gate
@@ -164,21 +217,14 @@ jobs:
        run: |
          sudo dpkg --add-architecture i386
          sudo apt-get update
-          sudo apt-get install -y -o APT::Immediate-Configure=0 libc6-i386 libstdc++6:i386 libgcc-s1:i386
+          sudo apt-get install -y -o APT::Immediate-Configure=0 libc6-i386 libstdc++6:i386 libgcc-s1:i386 libcurl4:i386

-      - name: Cache BYOND .zips
-        uses: actions/cache@v4
-        id: cache-byond
-        with:
-          path: ~/byond-zips-cache
-          key: byond-zips
-
-      - name: Setup BYOND Cache if Necessary and Install
+      - name: Evaluate BYOND version
+        id: version_evaluation
        run: |
-          echo "Setting up BYOND."
          FULL_VERSION=${{ matrix.byond }}
          if [[ "$FULL_VERSION" = "EDGE" ]] ; then
-              VERSIONS=$(curl https://www.byond.com/download/version.txt)
+              VERSIONS=$(curl https://spacestation13.github.io/byond-builds/version.txt)
              FULL_VERSION=$(echo "$VERSIONS" | tail -n1)
              echo "EDGE version evaluated to $FULL_VERSION"

@@ -190,14 +236,31 @@ jobs:
                  FULL_VERSION=${bad_linux_releases[$FULL_VERSION]}
              fi
          fi
-          if [[ ! -f $HOME/byond-zips-cache/linux/$FULL_VERSION.zip ]] ; then
+          echo "EVALUATED_VERSION=$FULL_VERSION" >> $GITHUB_OUTPUT
+
+      - name: Cache BYOND .zips
+        uses: actions/cache@v4
+        id: cache-byond
+        with:
+          path: ~/byond-zips-cache/linux/${{ steps.version_evaluation.outputs.EVALUATED_VERSION }}
+          key: byond-zips-linux-${{ steps.version_evaluation.outputs.EVALUATED_VERSION }}
+
+      - name: Setup BYOND Cache if Necessary and Install
+        run: |
+          echo "Setting up BYOND."
+          FULL_VERSION=${{ steps.version_evaluation.outputs.EVALUATED_VERSION }}
+          if [[ ! -f $HOME/byond-zips-cache/linux/$FULL_VERSION/$FULL_VERSION.zip ]] ; then
              BYOND_MAJOR=${FULL_VERSION%.*}
-              mkdir -p $HOME/byond-zips-cache/linux
-              curl "https://www.byond.com/download/build/$BYOND_MAJOR/${FULL_VERSION}_byond_linux.zip" -o $HOME/byond-zips-cache/linux/$FULL_VERSION.zip
+              mkdir -p $HOME/byond-zips-cache/linux/$FULL_VERSION
+              DOWNLOAD_URL="${{ env.DMAPI_BYOND_BUILD_MIRROR_DOWNLOAD_TEMPLATE }}"
+              if [[ "${{ matrix.byond }}" = "EDGE" ]] ; then
+                DOWNLOAD_URL="https://spacestation13.github.io/byond-builds/$BYOND_MAJOR/${FULL_VERSION}_byond_linux.zip"
+              fi
+              curl "$DOWNLOAD_URL" -o $HOME/byond-zips-cache/linux/$FULL_VERSION/$FULL_VERSION.zip
          fi
          mkdir -p "$HOME/BYOND"
          cd "$HOME/BYOND"
-          cp $HOME/byond-zips-cache/linux/$FULL_VERSION.zip byond.zip
+          cp $HOME/byond-zips-cache/linux/$FULL_VERSION/$FULL_VERSION.zip byond.zip
          unzip byond.zip
          cd byond
          make here
@@ -509,13 +572,6 @@ jobs:
        if: always()
        run: rm -f ${{ env.TGS_TELEMETRY_KEY_FILE }}

-      - name: Cache BYOND .zips
-        uses: actions/cache@v4
-        id: cache-byond
-        with:
-          path: ~/byond-zips-cache
-          key: byond-zips
-
      - name: Run Unit Tests
        run: sudo dotnet test --no-build --logger "GitHubActions;summary.includePassedTests=true;summary.includeSkippedTests=true" --filter TestCategory!=RequiresDatabase -c ${{ matrix.configuration }}NoWindows --collect:"XPlat Code Coverage" --settings build/ci.runsettings --results-directory ./TestResults tgstation-server.sln
        env:
@@ -578,13 +634,6 @@ jobs:
        if: always()
        run: rm -f ${{ env.TGS_TELEMETRY_KEY_FILE }}

-      - name: Cache BYOND .zips
-        uses: actions/cache@v4
-        id: cache-byond
-        with:
-          path: ~/byond-zips-cache
-          key: byond-zips
-
      - name: Run Unit Tests
        run: dotnet test --no-build --logger "GitHubActions;summary.includePassedTests=true;summary.includeSkippedTests=true" --filter TestCategory!=RequiresDatabase -c ${{ matrix.configuration }}NoWix --collect:"XPlat Code Coverage" --settings build/ci.runsettings --results-directory ./TestResults tgstation-server.sln
        env:
@@ -598,9 +647,50 @@ jobs:
          name: windows-unit-test-coverage-${{ matrix.configuration }}
          path: ./TestResults/

+  prep-edge-versions:
+    name: Prepare Live Tests Cache of EDGE Versions
+    needs: start-gate
+    runs-on: ubuntu-latest
+    steps:
+      - name: Cache BYOND .zips (Linux)
+        uses: actions/cache@v4
+        with:
+          path: ~/byond-zips-cache/live/linux
+          key: byond-zips-linux-live
+
+      - name: Cache BYOND .zips (Windows)
+        uses: actions/cache@v4
+        with:
+          path: ~/byond-zips-cache/live/windows
+          key: byond-zips-windows-live
+
+      - name: Evaluate BYOND version
+        id: version_evaluation
+        run: |
+          VERSIONS=$(curl https://spacestation13.github.io/byond-builds/version.txt)
+          FULL_VERSION=$(echo "$VERSIONS" | tail -n1)
+          echo "EDGE version evaluated to $FULL_VERSION"
+          echo "EVALUATED_VERSION=$FULL_VERSION" >> $GITHUB_OUTPUT
+
+      - name: Setup BYOND Cache if Necessary and Install
+        run: |
+          echo "Downloading BYOND."
+          FULL_VERSION=${{ steps.version_evaluation.outputs.EVALUATED_VERSION }}
+          BYOND_MAJOR=${FULL_VERSION%.*}
+          if [[ ! -f $HOME/byond-zips-cache/live/linux/$FULL_VERSION/$FULL_VERSION.zip ]] ; then
+              mkdir -p $HOME/byond-zips-cache/live/linux/$FULL_VERSION
+              DOWNLOAD_URL="https://spacestation13.github.io/byond-builds/$BYOND_MAJOR/${FULL_VERSION}_byond_linux.zip"
+              curl "$DOWNLOAD_URL" -o $HOME/byond-zips-cache/live/linux/$FULL_VERSION/$FULL_VERSION.zip
+          fi
+          if [[ ! -f $HOME/byond-zips-cache/live/windows/$FULL_VERSION/$FULL_VERSION.zip ]] ; then
+              mkdir -p $HOME/byond-zips-cache/live/windows/$FULL_VERSION
+              DOWNLOAD_URL="https://spacestation13.github.io/byond-builds/$BYOND_MAJOR/${FULL_VERSION}_byond.zip"
+              curl "$DOWNLOAD_URL" -o $HOME/byond-zips-cache/live/windows/$FULL_VERSION/$FULL_VERSION.zip
+          fi
+
  windows-integration-tests:
    name: Windows Live Tests
-    needs: [dmapi-build, opendream-build]
+    needs: [dmapi-build, opendream-build, prep-edge-versions]
    strategy:
      fail-fast: false
      matrix:
@@ -633,6 +723,12 @@ jobs:
        with:
          node-version: ${{ env.TGS_NODE_VERSION }}

+      - name: Cache BYOND .zips
+        uses: actions/cache@v4
+        with:
+          path: ~/byond-zips-cache/live/windows
+          key: byond-zips-windows-live
+
      - name: Set TGS_TEST_DUMP_API_SPEC
        if: ${{ matrix.configuration == 'Release' && matrix.watchdog-type == 'Advanced' && matrix.database-type == 'SqlServer' }}
        run: echo "TGS_TEST_DUMP_API_SPEC=yes" >> $Env:GITHUB_ENV
@@ -717,13 +813,6 @@ jobs:
        if: always()
        run: rm -f ${{ env.TGS_TELEMETRY_KEY_FILE }}

-      - name: Cache BYOND .zips
-        uses: actions/cache@v4
-        id: cache-byond
-        with:
-          path: ~/byond-zips-cache
-          key: byond-zips
-
      - name: Run Live Tests # Logging here is weird because printing massive amounts of text on Windows runners is SLOW AS SHIT!!!
        id: live-tests
        shell: bash
@@ -816,7 +905,7 @@ jobs:

  linux-integration-tests:
    name: Linux Live Tests
-    needs: [dmapi-build, opendream-build]
+    needs: [dmapi-build, opendream-build, prep-edge-versions]
    services: # We start all dbs here so we can just code the stuff once
      mssql:
        image: ${{ (matrix.database-type == 'SqlServer') && 'mcr.microsoft.com/mssql/server:2019-latest' || '' }}
@@ -884,13 +973,19 @@ jobs:
        run: |
          sudo dpkg --add-architecture i386
          sudo apt-get update
-          sudo apt-get install -y -o APT::Immediate-Configure=0 libc6-i386 libstdc++6:i386 gdb libgcc-s1:i386 libgdiplus
+          sudo apt-get install -y -o APT::Immediate-Configure=0 libc6-i386 libstdc++6:i386 gdb libgcc-s1:i386 libgdiplus libcurl4:i386

      - name: Setup Node.JS
        uses: actions/setup-node@v4
        with:
          node-version: ${{ env.TGS_NODE_VERSION }}

+      - name: Cache BYOND .zips
+        uses: actions/cache@v4
+        with:
+          path: ~/byond-zips-cache/live/linux
+          key: byond-zips-linux-live
+
      - name: Set Sqlite Connection Info
        if: ${{ matrix.database-type == 'Sqlite' }}
        run: |
@@ -945,13 +1040,6 @@ jobs:
        if: always()
        run: rm -f ${{ env.TGS_TELEMETRY_KEY_FILE }}

-      - name: Cache BYOND .zips
-        uses: actions/cache@v4
-        id: cache-byond
-        with:
-          path: ~/byond-zips-cache
-          key: byond-zips
-
      - name: Run Live Tests
        run: |
          cd tests/Tgstation.Server.Tests
@@ -1657,6 +1745,7 @@ jobs:
        check-winget-pr-template,
        efcore-version-match,
        code-scanning,
+        validate-nix-flake,
      ]
    runs-on: ubuntu-latest
    steps:
@@ -15,7 +15,7 @@ jobs:
          sudo apt-get install -y xmlstarlet

      - name: Setup Nix
-        uses: cachix/install-nix-action@v30
+        uses: cachix/install-nix-action@v31
        with:
          nix_path: nixpkgs=channel:nixos-unstable

@@ -59,11 +59,13 @@ RUN export TGS_TELEMETRY_KEY_FILE="../../${TGS_TELEMETRY_KEY_FILE}" \
 FROM mcr.microsoft.com/dotnet/aspnet:8.0-bookworm-slim

 #needed for byond, curl for healthchecks
-RUN apt-get update \
+RUN dpkg --add-architecture i386 \
+	&& apt-get update \
 	&& apt-get install -y \
 		gcc-multilib \
 		gdb \
 		curl \
+		libcurl4:i386 \
 	&& rm -rf /var/lib/apt/lists/*

 EXPOSE 5000
@@ -13,14 +13,14 @@
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <!-- Usage: Hard to say what exactly this is for, but not including it removes the test icon and breaks vstest.console.exe for some reason -->
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" Condition="'$(TgsTestNoSdk)' != 'true'" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.14.1" Condition="'$(TgsTestNoSdk)' != 'true'" />
    <!-- Usage: Dependency mocking for tests -->
    <!-- Pinned: Be VERY careful about updating https://github.com/moq/moq/issues/1372 -->
    <PackageReference Include="Moq" Version="4.20.72" />
    <!-- Usage: MSTest execution -->
-    <PackageReference Include="MSTest.TestAdapter" Version="3.8.3" />
+    <PackageReference Include="MSTest.TestAdapter" Version="3.9.3" />
    <!-- Usage: MSTest asserts etc... -->
-    <PackageReference Include="MSTest.TestFramework" Version="3.8.3" />
+    <PackageReference Include="MSTest.TestFramework" Version="3.9.3" />
  </ItemGroup>

 </Project>
@@ -3,8 +3,8 @@
  <!-- Integration tests will ensure they match across the board -->
  <Import Project="WebpanelVersion.props" />
  <PropertyGroup>
-    <TgsCoreVersion>6.17.0</TgsCoreVersion>
-    <TgsConfigVersion>5.7.0</TgsConfigVersion>
+    <TgsCoreVersion>6.18.0</TgsCoreVersion>
+    <TgsConfigVersion>5.8.0</TgsConfigVersion>
    <TgsRestVersion>10.13.0</TgsRestVersion>
    <TgsGraphQLVersion>0.6.0</TgsGraphQLVersion>
    <TgsCommonLibraryVersion>7.0.0</TgsCommonLibraryVersion>
@@ -22,11 +22,6 @@ apt-get install -y \
    xmlstarlet \
    libgdiplus

-declare repo_version=$(if command -v lsb_release &> /dev/null; then lsb_release -r -s; else grep -oP '(?<=^VERSION_ID=).+' /etc/os-release | tr -d '"'; fi)
-curl -L https://packages.microsoft.com/config/ubuntu/$repo_version/packages-microsoft-prod.deb -o packages-microsoft-prod.deb
-dpkg -i ./packages-microsoft-prod.deb
-rm packages-microsoft-prod.deb
-
 # https://github.com/nodesource/distributions
 mkdir -p /etc/apt/keyrings
 curl -fsSL https://deb.nodesource.com/gpgkey/nodesource-repo.gpg.key | gpg --dearmor -o /etc/apt/keyrings/nodesource.gpg
@@ -21,6 +21,7 @@ Depends:
 libstdc++6:i386 [amd64],
 libstdc++6 [i386],
 gcc-multilib [amd64],
+ libcurl4 [i386],
 Recommends:
 libsystemd0,
 gdb,
@@ -3,11 +3,12 @@

    inputs = {};

-    outputs = { ... }: {
+    outputs = { nixpkgs, ... }: {
        nixosModules = {
            default = { ... }: {
                imports = [ ./tgstation-server.nix ];
            };
        };
+        checks.x86_64-linux.package-build = nixpkgs.legacyPackages.x86_64-linux.callPackage ./package.nix { };
    };
 }
@@ -86,6 +86,7 @@ stdenv.mkDerivation {
    gcc_multi
    glibc
    bash
+    curl
  ];
  nativeBuildInputs = with pkgs; [
    makeWrapper
@@ -28,7 +28,7 @@
    <!-- Usage: HTTP constants reference -->
    <PackageReference Include="Microsoft.AspNetCore.Http.Extensions" Version="2.3.0" />
    <!-- Usage: Decoding the 'nbf' property of JWTs -->
-    <PackageReference Include="Microsoft.IdentityModel.JsonWebTokens" Version="8.8.0" />
+    <PackageReference Include="Microsoft.IdentityModel.JsonWebTokens" Version="8.13.0" />
    <!-- Usage: Data model annotating -->
    <PackageReference Include="System.ComponentModel.Annotations" Version="5.0.0" />
  </ItemGroup>
@@ -9,8 +9,7 @@

  <ItemGroup>
    <!-- GraphQL connector and code generator -->
-    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.4" />
-    <PackageReference Include="StrawberryShake.Server" Version="15.1.3" />
+    <PackageReference Include="StrawberryShake.Server" Version="15.1.8" />
  </ItemGroup>

  <ItemGroup>
@@ -11,9 +11,9 @@

  <ItemGroup>
    <!-- Usage: Connecting to SignalR hubs in API -->
-    <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="9.0.4" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Client" Version="9.0.7" />
    <!-- Usage: Using target JSON serializer for API -->
-    <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.4" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.7" />
  </ItemGroup>

  <ItemGroup>
@@ -13,9 +13,9 @@

  <ItemGroup>
    <!-- Usage: Identifying if we're running under SystemD -->
-    <PackageReference Include="Microsoft.Extensions.Hosting.Systemd" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.Systemd" Version="9.0.7" />
    <!-- Usage: Console logging plugin -->
-    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.7" />
  </ItemGroup>

  <ItemGroup>
@@ -21,21 +21,21 @@
    <!-- Usage: Command line argument support -->
    <PackageReference Include="McMaster.Extensions.CommandLineUtils" Version="4.1.1" />
    <!-- Usage: Identifies when we are running in the context of the Windows SCM -->
-    <PackageReference Include="Microsoft.Extensions.Hosting.WindowsServices" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Hosting.WindowsServices" Version="9.0.7" />
    <!-- Usage: Windows event log logging plugin -->
-    <PackageReference Include="Microsoft.Extensions.Logging.EventLog" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Logging.EventLog" Version="9.0.7" />
    <!-- Usage: Console logging plugin -->
-    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Logging.Console" Version="9.0.7" />
    <!-- Usage: Updated transitive dependency of Core.System.ServiceProcess -->
    <PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
    <!-- Usage: Updated transitive dependency of Core.System.ServiceProcess -->
-    <PackageReference Include="System.Drawing.Common" Version="9.0.4" />
+    <PackageReference Include="System.Drawing.Common" Version="9.0.7" />
    <!-- Usage: Updated transitive dependency, unable to tell what of -->
    <PackageReference Include="System.Private.Uri" Version="4.3.2" />
    <!-- Usage: OS identification -->
    <PackageReference Include="System.Runtime.InteropServices" Version="4.3.0" />
    <!-- Usage: Windows Service Manager intergration -->
-    <PackageReference Include="System.ServiceProcess.ServiceController" Version="9.0.4" />
+    <PackageReference Include="System.ServiceProcess.ServiceController" Version="9.0.7" />
  </ItemGroup>

  <ItemGroup>
@@ -38,7 +38,8 @@
  </Target>

  <ItemGroup>
-    <PackageReference Include="StrawberryShake.Server" Version="15.1.3" />
+    <!-- GraphQL code generator -->
+    <PackageReference Include="StrawberryShake.Server" Version="15.1.8" />
  </ItemGroup>

  <ItemGroup>
@@ -1855,14 +1855,15 @@ __metadata:
  linkType: hard

 "form-data@npm:^4.0.0":
-  version: 4.0.2
-  resolution: "form-data@npm:4.0.2"
+  version: 4.0.4
+  resolution: "form-data@npm:4.0.4"
  dependencies:
    asynckit: "npm:^0.4.0"
    combined-stream: "npm:^1.0.8"
    es-set-tostringtag: "npm:^2.1.0"
+    hasown: "npm:^2.0.2"
    mime-types: "npm:^2.1.12"
-  checksum: 10/82c65b426af4a40090e517a1bc9057f76970b4c6043e37aa49859c447d88553e77d4cc5626395079a53d2b0889ba5f2a49f3900db3ad3f3f1bf76613532572fb
+  checksum: 10/a4b62e21932f48702bc468cc26fb276d186e6b07b557e3dd7cc455872bdbb82db7db066844a64ad3cf40eaf3a753c830538183570462d3649fdfd705601cbcfb
  languageName: node
  linkType: hard

@@ -10,7 +10,7 @@

  <ItemGroup>
    <!-- Usage: Logging abstractions -->
-    <PackageReference Include="Microsoft.Extensions.Logging" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Extensions.Logging" Version="9.0.7" />
    <!-- Usage: POSIX support for signals -->
    <PackageReference Include="Mono.Posix.NETStandard" Version="1.0.0" />
  </ItemGroup>
@@ -3,7 +3,7 @@
  "isRoot": true,
  "tools": {
    "dotnet-ef": {
-      "version": "9.0.4",
+      "version": "9.0.7",
      "commands": [
        "dotnet-ef"
      ]
@@ -351,28 +351,11 @@ namespace Tgstation.Server.Host.Components.Chat

 		/// <inheritdoc />
 		public void QueueWatchdogMessage(string message)
-		{
-			ArgumentNullException.ThrowIfNull(message);
+			=> QueueMessageGeneric(mapping => mapping.IsWatchdogChannel, message, "WD");

-			message = String.Format(CultureInfo.InvariantCulture, "WD: {0}", message);
-
-			if (!initialProviderConnectionsTask!.IsCompleted)
-				logger.LogTrace("Waiting for initial provider connections before sending watchdog message...");
-
-			// Reimplementing QueueMessage
-			QueueMessageInternal(
-				new MessageContent
-				{
-					Text = message,
-				},
-				() =>
-				{
-					// so it doesn't change while we're using it
-					lock (mappedChannels)
-						return mappedChannels.Where(x => x.Value.IsWatchdogChannel).Select(x => x.Key).ToList();
-				},
-				true);
-		}
+		/// <inheritdoc />
+		public void QueueRawDeploymentMessage(string message)
+			=> QueueMessageGeneric(mapping => mapping.IsUpdatesChannel, message, null);

 		/// <inheritdoc />
 		public Func<string?, string, Action<bool>> QueueDeploymentMessage(
@@ -1111,5 +1094,38 @@ namespace Tgstation.Server.Host.Components.Chat

 			AddMessageTask(SendMessageTask());
 		}
+
+		/// <summary>
+		/// Queues a message to a selected set of <see cref="ChannelMapping"/>s.
+		/// </summary>
+		/// <param name="channelSelector">A <see cref="Predicate{T}"/> for selecting the <see cref="ChannelMapping"/>s to send to.</param>
+		/// <param name="message">The message to send.</param>
+		/// <param name="prefix">The optional prefix to the message to be sent.</param>
+		void QueueMessageGeneric(Predicate<ChannelMapping> channelSelector, string message, string? prefix)
+		{
+			ArgumentNullException.ThrowIfNull(message);
+
+			if (prefix != null)
+			{
+				message = $"{prefix}: {message}";
+			}
+
+			if (!initialProviderConnectionsTask!.IsCompleted)
+				logger.LogTrace("Waiting for initial provider connections before sending chat message...");
+
+			// Reimplementing QueueMessage
+			QueueMessageInternal(
+				new MessageContent
+				{
+					Text = message,
+				},
+				() =>
+				{
+					// so it doesn't change while we're using it
+					lock (mappedChannels)
+						return mappedChannels.Where(x => channelSelector(x.Value)).Select(x => x.Key).ToList();
+				},
+				true);
+		}
 	}
 }
@@ -57,6 +57,12 @@ namespace Tgstation.Server.Host.Components.Chat
 		/// <param name="message">The message being sent.</param>
 		void QueueWatchdogMessage(string message);

+		/// <summary>
+		/// Queue a chat <paramref name="message"/> to configured deployment channels.
+		/// </summary>
+		/// <param name="message">The message being sent.</param>
+		void QueueRawDeploymentMessage(string message);
+
 		/// <summary>
 		/// Send the message for a deployment to configured deployment channels.
 		/// </summary>
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
-using System.IO;
 using System.Linq;
 using System.Runtime.CompilerServices;
 using System.Text;
@@ -431,7 +430,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 					// Don't dispose it
 					logger.LogDebug("Creating legacy two folder .dmb provider targeting {aDirName} directory...", LegacyADirectoryName);
 #pragma warning disable CA2000 // Dispose objects before losing scope (false positive)
-					newProvider = new DmbProvider(compileJob, engineVersion, ioManager, new DisposeInvoker(CleanupAction), Path.DirectorySeparatorChar + LegacyADirectoryName);
+					newProvider = new DmbProvider(compileJob, engineVersion, ioManager, new DisposeInvoker(CleanupAction), LegacyADirectoryName);
 #pragma warning restore CA2000 // Dispose objects before losing scope
 				}

@@ -12,7 +12,18 @@ namespace Tgstation.Server.Host.Components.Deployment
 	sealed class DmbProvider : DmbProviderBase, IDmbProvider
 	{
 		/// <inheritdoc />
-		public override string Directory => ioManager.ResolvePath(CompileJob.DirectoryName!.Value.ToString() + directoryAppend);
+		public override string Directory
+		{
+			get
+			{
+				var stringifiedCompileJobDirectory = CompileJob.DirectoryName!.Value.ToString();
+
+				if (directoryAppend != null)
+					stringifiedCompileJobDirectory = ioManager.ConcatPath(stringifiedCompileJobDirectory, directoryAppend);
+
+				return ioManager.ResolvePath(stringifiedCompileJobDirectory);
+			}
+		}

 		/// <inheritdoc />
 		public override Models.CompileJob CompileJob { get; }
@@ -28,7 +39,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 		/// <summary>
 		/// Extra path to add to the end of <see cref="CompileJob.DirectoryName"/>.
 		/// </summary>
-		readonly string directoryAppend;
+		readonly string? directoryAppend;

 		/// <summary>
 		/// The <see cref="Action"/> to run when <see cref="DisposeAsync"/> is called.
@@ -49,7 +60,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 			EngineVersion = engineVersion ?? throw new ArgumentNullException(nameof(engineVersion));
 			this.ioManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
 			this.onDispose = onDispose ?? throw new ArgumentNullException(nameof(onDispose));
-			this.directoryAppend = directoryAppend ?? String.Empty;
+			this.directoryAppend = directoryAppend;
 		}

 		/// <inheritdoc />
@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Diagnostics;
 using System.Globalization;
 using System.IO;
+using System.IO.Abstractions;
 using System.Runtime.Versioning;
 using System.Threading;
 using System.Threading.Tasks;
@@ -187,8 +188,10 @@ namespace Tgstation.Server.Host.Components.Deployment
 				dest = IOManager.ResolvePath(mirrorGuid.ToString());

 				using var semaphore = taskThrottle.HasValue ? new SemaphoreSlim(taskThrottle.Value) : null;
+
+				var dir = await IOManager.DirectoryInfo(src, cancellationToken);
 				await Task.WhenAll(MirrorDirectoryImpl(
-					src,
+					dir,
 					dest,
 					semaphore,
 					securityLevel,
@@ -230,21 +233,20 @@ namespace Tgstation.Server.Host.Components.Deployment
 		/// <summary>
 		/// Recursively create tasks to create a hard link directory mirror of <paramref name="src"/> to <paramref name="dest"/>.
 		/// </summary>
-		/// <param name="src">The source directory path.</param>
+		/// <param name="src">The source <see cref="IDirectoryInfo"/>.</param>
 		/// <param name="dest">The destination directory path.</param>
 		/// <param name="semaphore">Optional <see cref="SemaphoreSlim"/> used to limit degree of parallelism.</param>
 		/// <param name="securityLevel">The launch <see cref="DreamDaemonSecurity"/> level.</param>
 		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
-		/// <returns>A <see cref="IEnumerable{T}"/> of <see cref="Task"/>s representing the running operations. The first <see cref="Task"/> returned is always the necessary call to <see cref="IIOManager.CreateDirectory(string, CancellationToken)"/>.</returns>
+		/// <returns>An <see cref="IEnumerable{T}"/> of <see cref="Task"/>s representing the running operations. The first <see cref="Task"/> returned is always the necessary call to <see cref="IIOManager.CreateDirectory(string, CancellationToken)"/>.</returns>
 		/// <remarks>I genuinely don't know how this will work with symlinked files. Waiting for the issue report I guess.</remarks>
-		IEnumerable<Task> MirrorDirectoryImpl(string src, string dest, SemaphoreSlim? semaphore, DreamDaemonSecurity securityLevel, CancellationToken cancellationToken)
+		IEnumerable<Task> MirrorDirectoryImpl(IDirectoryInfo src, string dest, SemaphoreSlim? semaphore, DreamDaemonSecurity securityLevel, CancellationToken cancellationToken)
 		{
-			var dir = new DirectoryInfo(src);
 			Task? subdirCreationTask = null;
 			var dreamDaemonWillAcceptOutOfDirectorySymlinks = securityLevel == DreamDaemonSecurity.Trusted;
-			foreach (var subDirectory in dir.EnumerateDirectories())
+			foreach (var subDirectory in src.EnumerateDirectories())
 			{
-				var mirroredName = Path.Combine(dest, subDirectory.Name);
+				var mirroredName = IOManager.ConcatPath(dest, subDirectory.Name);

 				// check if we are a symbolic link
 				if (subDirectory.Attributes.HasFlag(FileAttributes.ReparsePoint))
@@ -275,7 +277,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 						logger.LogDebug("Recreating symlinked directory {name} as hard links...", subDirectory.Name);

 				var checkingSubdirCreationTask = true;
-				foreach (var copyTask in MirrorDirectoryImpl(subDirectory.FullName, mirroredName, semaphore, securityLevel, cancellationToken))
+				foreach (var copyTask in MirrorDirectoryImpl(subDirectory, mirroredName, semaphore, securityLevel, cancellationToken))
 				{
 					if (subdirCreationTask == null)
 					{
@@ -289,7 +291,7 @@ namespace Tgstation.Server.Host.Components.Deployment
 				}
 			}

-			foreach (var fileInfo in dir.EnumerateFiles())
+			foreach (var fileInfo in src.EnumerateFiles())
 			{
 				if (subdirCreationTask == null)
 				{
@@ -6,8 +6,10 @@ using System.Threading;
 using System.Threading.Tasks;

 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;

 using Tgstation.Server.Api.Models;
+using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Jobs;

@@ -41,6 +43,11 @@ namespace Tgstation.Server.Host.Components.Engine
 		/// <inheritdoc />
 		protected override EngineType TargetEngineType => EngineType.Byond;

+		/// <summary>
+		/// The <see cref="GeneralConfiguration"/> <see cref="IOptionsMonitor{TOptions}"/> for the <see cref="ByondInstallerBase"/>.
+		/// </summary>
+		protected IOptionsMonitor<GeneralConfiguration> GeneralConfigurationOptions { get; }
+
 		/// <summary>
 		/// Path to the system user's local BYOND folder.
 		/// </summary>
@@ -52,25 +59,85 @@ namespace Tgstation.Server.Host.Components.Engine
 		protected abstract string DreamMakerName { get; }

 		/// <summary>
-		/// Gets the URL formatter string for downloading a byond version of {0:Major} {1:Minor}.
+		/// Template to do ${Marker:xxx} replacements in <see cref="GeneralConfiguration.ByondZipDownloadTemplate"/>.
 		/// </summary>
-		protected abstract string ByondRevisionsUrlTemplate { get; }
+		protected abstract string OSMarkerTemplate { get; }

 		/// <summary>
 		/// The <see cref="IFileDownloader"/> for the <see cref="ByondInstallerBase"/>.
 		/// </summary>
 		readonly IFileDownloader fileDownloader;

+		/// <summary>
+		/// Format a given <paramref name="byondZipDownloadTemplate"/>.
+		/// </summary>
+		/// <param name="semver">The BYOND version to download.</param>
+		/// <param name="byondZipDownloadTemplate">The template.</param>
+		/// <param name="osMarkerTemplate">The <see cref="OSMarkerTemplate"/>.</param>
+		/// <returns>The formatted byond download <see cref="Uri"/>.</returns>
+		/// <remarks>Exposed only for testability.</remarks>
+		internal static Uri GetDownloadZipUrl(Version semver, string byondZipDownloadTemplate, string osMarkerTemplate)
+		{
+			// god forbid
+			var guardGuid = Guid.NewGuid();
+
+			var url = byondZipDownloadTemplate
+				.Replace("$$", guardGuid.ToString(), StringComparison.Ordinal)
+				.Replace("${Major}", semver.Major.ToString(CultureInfo.InvariantCulture), StringComparison.Ordinal)
+				.Replace("${Minor}", semver.Minor.ToString(CultureInfo.InvariantCulture), StringComparison.Ordinal);
+
+			var osMarkerPrefix = $"${{{osMarkerTemplate}:";
+			var osMarkerIndex = url.IndexOf(osMarkerPrefix);
+			while (osMarkerIndex != -1)
+			{
+				var start = osMarkerIndex + osMarkerPrefix.Length;
+				var end = url.IndexOf('}', start);
+				if (end == -1)
+					break;
+
+				var substitution = url.Substring(start, end - start);
+				url = url.Replace($"{osMarkerPrefix}{substitution}}}", substitution, StringComparison.Ordinal);
+
+				osMarkerIndex = url.IndexOf(osMarkerPrefix);
+			}
+
+			// at this point, any other substitution attempts should be removed
+			var otherMarkerPrefix = "${";
+			var otherMarkerIndex = url.IndexOf(otherMarkerPrefix);
+			while (otherMarkerIndex != -1)
+			{
+				var start = otherMarkerIndex + otherMarkerPrefix.Length;
+				var end = url.IndexOf('}', start);
+				if (end == -1)
+					break;
+
+				var substitution = url.Substring(start, end - start);
+				url = url.Replace($"{otherMarkerPrefix}{substitution}}}", String.Empty, StringComparison.Ordinal);
+
+				otherMarkerIndex = url.IndexOf(otherMarkerPrefix);
+			}
+
+			url = url.Replace(guardGuid.ToString(), "$", StringComparison.Ordinal);
+
+			return new Uri(url);
+		}
+
 		/// <summary>
 		/// Initializes a new instance of the <see cref="ByondInstallerBase"/> class.
 		/// </summary>
 		/// <param name="ioManager">The <see cref="IIOManager"/> for the <see cref="EngineInstallerBase"/>.</param>
 		/// <param name="logger">The <see cref="ILogger"/> for the <see cref="EngineInstallerBase"/>.</param>
 		/// <param name="fileDownloader">The value of <see cref="fileDownloader"/>.</param>
-		protected ByondInstallerBase(IIOManager ioManager, ILogger<ByondInstallerBase> logger, IFileDownloader fileDownloader)
+		/// <param name="generalConfigurationOptions">The value of <see cref="GeneralConfigurationOptions"/>.</param>
+		protected ByondInstallerBase(
+			IIOManager ioManager,
+			ILogger<ByondInstallerBase> logger,
+			IFileDownloader fileDownloader,
+			IOptionsMonitor<GeneralConfiguration> generalConfigurationOptions)
 			: base(ioManager, logger)
 		{
 			this.fileDownloader = fileDownloader ?? throw new ArgumentNullException(nameof(fileDownloader));
+			GeneralConfigurationOptions = generalConfigurationOptions ?? throw new ArgumentNullException(nameof(generalConfigurationOptions));
 		}

 		/// <inheritdoc />
@@ -78,7 +145,7 @@ namespace Tgstation.Server.Host.Components.Engine
 		{
 			CheckVersionValidity(version);

-			var installationIOManager = new ResolvingIOManager(IOManager, path);
+			var installationIOManager = IOManager.CreateResolverForSubdirectory(path);
 			var supportsMapThreads = version.Version >= MapThreadsVersion;

 			return ValueTask.FromResult<IEngineInstallation>(
@@ -195,8 +262,12 @@ namespace Tgstation.Server.Host.Components.Engine
 		Uri GetDownloadZipUrl(EngineVersion version)
 		{
 			CheckVersionValidity(version);
-			var url = String.Format(CultureInfo.InvariantCulture, ByondRevisionsUrlTemplate, version.Version!.Major, version.Version.Minor);
-			return new Uri(url);
+
+			var guardGuid = Guid.NewGuid();
+
+			var semver = version.Version!;
+			var template = GeneralConfigurationOptions.CurrentValue.ByondZipDownloadTemplate;
+			return GetDownloadZipUrl(semver, template, OSMarkerTemplate);
 		}
 	}
 }
@@ -126,7 +126,7 @@ namespace Tgstation.Server.Host.Components.Engine
 			var dotnetPath = (await DotnetHelper.GetDotnetPath(platformIdentifier, IOManager, cancellationToken))
 				?? throw new JobException("Failed to find dotnet path!");
 			return new OpenDreamInstallation(
-				new ResolvingIOManager(IOManager, path),
+				IOManager.CreateResolverForSubdirectory(path),
 				asyncDelayer,
 				httpClientFactory,
 				dotnetPath,
@@ -5,9 +5,11 @@ using System.Threading;
 using System.Threading.Tasks;

 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;

 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Common.Extensions;
+using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.IO;

 namespace Tgstation.Server.Host.Components.Engine
@@ -39,7 +41,7 @@ namespace Tgstation.Server.Host.Components.Engine
 		protected override string DreamMakerName => DreamMakerExecutableName + ShellScriptExtension;

 		/// <inheritdoc />
-		protected override string ByondRevisionsUrlTemplate => "https://www.byond.com/download/build/{0}/{0}.{1}_byond_linux.zip";
+		protected override string OSMarkerTemplate => "Linux";

 		/// <summary>
 		/// The <see cref="IPostWriteHandler"/> for the <see cref="PosixByondInstaller"/>.
@@ -52,13 +54,15 @@ namespace Tgstation.Server.Host.Components.Engine
 		/// <param name="postWriteHandler">The value of <see cref="postWriteHandler"/>.</param>
 		/// <param name="ioManager">The <see cref="IIOManager"/> for the <see cref="ByondInstallerBase"/>.</param>
 		/// <param name="fileDownloader">The <see cref="IFileDownloader"/> for the <see cref="ByondInstallerBase"/>.</param>
+		/// <param name="generalConfigurationOptions">The <see cref="GeneralConfiguration"/> <see cref="IOptionsMonitor{TOptions}"/>.</param>
 		/// <param name="logger">The <see cref="ILogger"/> for the <see cref="ByondInstallerBase"/>.</param>
 		public PosixByondInstaller(
 			IPostWriteHandler postWriteHandler,
 			IIOManager ioManager,
 			IFileDownloader fileDownloader,
+			IOptionsMonitor<GeneralConfiguration> generalConfigurationOptions,
 			ILogger<PosixByondInstaller> logger)
-			: base(ioManager, logger, fileDownloader)
+			: base(ioManager, logger, fileDownloader, generalConfigurationOptions)
 		{
 			this.postWriteHandler = postWriteHandler ?? throw new ArgumentNullException(nameof(postWriteHandler));

@@ -69,18 +69,13 @@ namespace Tgstation.Server.Host.Components.Engine
 		protected override string PathToUserFolder { get; }

 		/// <inheritdoc />
-		protected override string ByondRevisionsUrlTemplate => "https://www.byond.com/download/build/{0}/{0}.{1}_byond.zip";
+		protected override string OSMarkerTemplate => "Windows";

 		/// <summary>
 		/// The <see cref="IProcessExecutor"/> for the <see cref="WindowsByondInstaller"/>.
 		/// </summary>
 		readonly IProcessExecutor processExecutor;

-		/// <summary>
-		/// The <see cref="GeneralConfiguration"/> for the <see cref="WindowsByondInstaller"/>.
-		/// </summary>
-		readonly GeneralConfiguration generalConfiguration;
-
 		/// <summary>
 		/// The <see cref="SessionConfiguration"/> for the <see cref="WindowsByondInstaller"/>.
 		/// </summary>
@@ -100,7 +95,7 @@ namespace Tgstation.Server.Host.Components.Engine
 		/// Initializes a new instance of the <see cref="WindowsByondInstaller"/> class.
 		/// </summary>
 		/// <param name="processExecutor">The value of <see cref="processExecutor"/>.</param>
-		/// <param name="generalConfigurationOptions">The <see cref="IOptions{TOptions}"/> containing the value of <see cref="generalConfiguration"/>.</param>
+		/// <param name="generalConfigurationOptions">The <see cref="IOptionsMonitor{TOptions}"/> containing the <see cref="GeneralConfiguration"/>.</param>
 		/// <param name="sessionConfigurationOptions">The <see cref="IOptions{TOptions}"/> containing the value of <see cref="sessionConfiguration"/>.</param>
 		/// <param name="ioManager">The <see cref="IIOManager"/> for the <see cref="ByondInstallerBase"/>.</param>
 		/// <param name="fileDownloader">The <see cref="IFileDownloader"/> for the <see cref="ByondInstallerBase"/>.</param>
@@ -109,13 +104,12 @@ namespace Tgstation.Server.Host.Components.Engine
 			IProcessExecutor processExecutor,
 			IIOManager ioManager,
 			IFileDownloader fileDownloader,
-			IOptions<GeneralConfiguration> generalConfigurationOptions,
+			IOptionsMonitor<GeneralConfiguration> generalConfigurationOptions,
 			IOptions<SessionConfiguration> sessionConfigurationOptions,
 			ILogger<WindowsByondInstaller> logger)
-			: base(ioManager, logger, fileDownloader)
+			: base(ioManager, logger, fileDownloader, generalConfigurationOptions)
 		{
 			this.processExecutor = processExecutor ?? throw new ArgumentNullException(nameof(processExecutor));
-			generalConfiguration = generalConfigurationOptions?.Value ?? throw new ArgumentNullException(nameof(generalConfigurationOptions));
 			sessionConfiguration = sessionConfigurationOptions?.Value ?? throw new ArgumentNullException(nameof(sessionConfigurationOptions));

 			var useServiceSpecialTactics = Environment.Is64BitProcess && Environment.UserName == $"{Environment.MachineName}$";
@@ -150,7 +144,7 @@ namespace Tgstation.Server.Host.Components.Engine
 				installDirectXTask,
 			};

-			if (!generalConfiguration.SkipAddingByondFirewallException)
+			if (!GeneralConfigurationOptions.CurrentValue.SkipAddingByondFirewallException)
 			{
 				var firewallTask = AddDreamDaemonToFirewall(version, path, deploymentPipelineProcesses, cancellationToken);
 				tasks.Add(firewallTask);
@@ -165,7 +159,7 @@ namespace Tgstation.Server.Host.Components.Engine
 			CheckVersionValidity(version);
 			ArgumentNullException.ThrowIfNull(path);

-			if (generalConfiguration.SkipAddingByondFirewallException)
+			if (GeneralConfigurationOptions.CurrentValue.SkipAddingByondFirewallException)
 				return;

 			if (version.Version < DDExeVersion)
@@ -18,7 +18,7 @@ namespace Tgstation.Server.Host.Components.Engine
 		readonly IIOManager ioManager;

 		/// <summary>
-		/// The <see cref="MemoryStream"/> containing the zip data of the engine.
+		/// The <see cref="Stream"/> containing the zip data of the engine.
 		/// </summary>
 		readonly Stream zipStream;

@@ -531,7 +531,10 @@ namespace Tgstation.Server.Host.Components
 						}
 					}
 					else if (preserveTestMerges)
+					{
+						Chat.QueueRawDeploymentMessage("Automatic update has failed due to a conflicting testmerge!");
 						throw new JobException(Api.Models.ErrorCode.InstanceUpdateTestMergeConflict);
+					}

 					if (!preserveTestMerges)
 					{
@@ -164,7 +164,7 @@ namespace Tgstation.Server.Host.Components
 		/// </summary>
 		/// <param name="instanceIOManager">The instance's <see cref="IIOManager"/>.</param>
 		/// <returns>The <see cref="IIOManager"/> for the instance's "Game" directory.</returns>
-		static ResolvingIOManager CreateGameIOManager(IIOManager instanceIOManager) => new(instanceIOManager, "Game");
+		static IIOManager CreateGameIOManager(IIOManager instanceIOManager) => instanceIOManager.CreateResolverForSubdirectory("Game");

 #pragma warning disable CA1502 // TODO: Decomplexify
 		/// <summary>
@@ -270,11 +270,11 @@ namespace Tgstation.Server.Host.Components
 			var instanceIoManager = CreateInstanceIOManager(metadata);

 			// various other ioManagers
-			var repoIoManager = new ResolvingIOManager(instanceIoManager, "Repository");
-			var byondIOManager = new ResolvingIOManager(instanceIoManager, "Byond");
+			var repoIoManager = instanceIoManager.CreateResolverForSubdirectory("Repository");
+			var byondIOManager = instanceIoManager.CreateResolverForSubdirectory("Byond");
 			var gameIoManager = CreateGameIOManager(instanceIoManager);
-			var diagnosticsIOManager = new ResolvingIOManager(instanceIoManager, "Diagnostics");
-			var configurationIoManager = new ResolvingIOManager(instanceIoManager, "Configuration");
+			var diagnosticsIOManager = instanceIoManager.CreateResolverForSubdirectory("Diagnostics");
+			var configurationIoManager = instanceIoManager.CreateResolverForSubdirectory("Configuration");

 			var metricFactory = this.metricFactory.WithLabels(
 				new Dictionary<string, string>
@@ -441,6 +441,6 @@ namespace Tgstation.Server.Host.Components
 		/// </summary>
 		/// <param name="metadata">The <see cref="Models.Instance"/>.</param>
 		/// <returns>The <see cref="IIOManager"/> for the <paramref name="metadata"/>.</returns>
-		ResolvingIOManager CreateInstanceIOManager(Models.Instance metadata) => new(ioManager, metadata.Path!);
+		IIOManager CreateInstanceIOManager(Models.Instance metadata) => ioManager.CreateResolverForSubdirectory(metadata.Path!);
 	}
 }
@@ -702,7 +702,7 @@ namespace Tgstation.Server.Host.Components
 		{
 			logger.LogDebug("Running as user: {username}", Environment.UserName);

-			generalConfiguration.CheckCompatibility(logger);
+			generalConfiguration.CheckCompatibility(logger, ioManager);

 			using (var systemIdentity = systemIdentityFactory.GetCurrent())
 			{
@@ -1,7 +1,6 @@
 using System;
 using System.Collections.Generic;
 using System.Globalization;
-using System.IO;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -1099,8 +1098,8 @@ namespace Tgstation.Server.Host.Components.Repository
 			=> ioManager.GetDirectoryName(libGitRepo
 				.Info
 				.Path
-				.TrimEnd(Path.DirectorySeparatorChar)
-				.TrimEnd(Path.AltDirectorySeparatorChar));
+				.TrimEnd(ioManager.DirectorySeparatorChar)
+				.TrimEnd(ioManager.AltDirectorySeparatorChar));

 		/// <summary>
 		/// Recusively update all <see cref="Submodule"/>s in the <see cref="libGitRepo"/>.
@@ -333,10 +333,10 @@ namespace Tgstation.Server.Host.Components.StaticFiles
 							},
 							async cancellationToken =>
 							{
-								FileStream? result = null;
+								Stream? result = null;
 								void GetFileStream()
 								{
-									result = ioManager.GetFileStream(path, false);
+									result = synchronousIOManager.GetFileStream(path);
 								}

 								if (systemIdentity == null)
@@ -771,7 +771,7 @@ namespace Tgstation.Server.Host.Components.StaticFiles
 			var nullOrEmptyCheck = String.IsNullOrEmpty(configurationRelativePath);
 			if (nullOrEmptyCheck)
 				configurationRelativePath = DefaultIOManager.CurrentDirectory;
-			if (configurationRelativePath![0] == Path.DirectorySeparatorChar || configurationRelativePath[0] == Path.AltDirectorySeparatorChar)
+			if (configurationRelativePath![0] == ioManager.DirectorySeparatorChar || configurationRelativePath[0] == ioManager.AltDirectorySeparatorChar)
 				configurationRelativePath = DefaultIOManager.CurrentDirectory + configurationRelativePath;
 			var resolved = ioManager.ResolvePath(configurationRelativePath);
 			var local = !nullOrEmptyCheck ? ioManager.ResolvePath() : null;
@@ -1,6 +1,5 @@
 using System;
 using System.Collections.Generic;
-using System.IO;
 using System.Linq;

 using Microsoft.Extensions.Logging;
@@ -9,6 +8,7 @@ using Newtonsoft.Json.Converters;

 using Tgstation.Server.Api.Models.Internal;
 using Tgstation.Server.Host.Extensions;
+using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.Properties;
 using Tgstation.Server.Host.Setup;

@@ -31,6 +31,11 @@ namespace Tgstation.Server.Host.Configuration
 		/// </summary>
 		public const ushort DefaultApiPort = 5000;

+		/// <summary>
+		/// Default vale for <see cref="ByondZipDownloadTemplate"/>.
+		/// </summary>
+		public const string DefaultByondZipDownloadTemplate = "https://www.byond.com/download/build/${Major}/${Major}.${Minor}_byond${Linux:_linux}.zip";
+
 		/// <summary>
 		/// The default value for <see cref="ServerInformationBase.MinimumPasswordLength"/>.
 		/// </summary>
@@ -148,6 +153,17 @@ namespace Tgstation.Server.Host.Configuration
 		[YamlMember(SerializeAs = typeof(string))]
 		public Uri OpenDreamGitUrl { get; set; } = new Uri(DefaultOpenDreamGitUrl);

+		/// <summary>
+		/// The formatter used to download official byond zip files for a given version
+		/// - ${Major} is substituted with the major version number
+		/// - ${Minor} is substituted with the minor version number
+		/// - ${Linux:xxx}, where xxx is any string, will be substituted with xxx if running under Linux.
+		/// - ${Windows:xxx}, where xxx is any string, will be substituted with xxx if running under Windows.
+		/// - $$ will evaluate to a literal $ and not be used for substitutions.
+		/// - Any inapplicable ${xxx} string will be removed.
+		/// </summary>
+		public string ByondZipDownloadTemplate { get; set; } = DefaultByondZipDownloadTemplate;
+
 		/// <summary>
 		/// The prefix to the OpenDream semver as tags appear in the git repository.
 		/// </summary>
@@ -178,7 +194,8 @@ namespace Tgstation.Server.Host.Configuration
 		/// Validates the current <see cref="ConfigVersion"/>'s compatibility and provides migration instructions.
 		/// </summary>
 		/// <param name="logger">The <see cref="ILogger"/> to use.</param>
-		public void CheckCompatibility(ILogger logger)
+		/// <param name="ioManager">The <see cref="IIOManager"/> to use.</param>
+		public void CheckCompatibility(ILogger logger, IIOManager ioManager)
 		{
 			ArgumentNullException.ThrowIfNull(logger);

@@ -204,7 +221,7 @@ namespace Tgstation.Server.Host.Configuration
 			if (ByondTopicTimeout <= 1000)
 				logger.LogWarning("The timeout for sending BYOND topics is very low ({ms}ms). Topic calls may fail to complete at all!", ByondTopicTimeout);

-			if (AdditionalEventScriptsDirectories?.Any(path => !Path.IsPathRooted(path)) == true)
+			if (AdditionalEventScriptsDirectories?.Any(path => !ioManager.IsPathRooted(path)) == true)
 				logger.LogWarning($"Config option \"{nameof(AdditionalEventScriptsDirectories)}\" contains non-rooted paths. These will be evaluated relative to each instances \"Configuration\" directory!");
 		}
 	}
@@ -2,6 +2,7 @@
 using System.Collections.Frozen;
 using System.Collections.Generic;
 using System.Globalization;
+using System.IO.Abstractions;
 using System.Threading.Tasks;
 using System.Web;

@@ -105,10 +106,12 @@ namespace Tgstation.Server.Host.Core
 		public static IServerFactory CreateDefaultServerFactory()
 		{
 			var assemblyInformationProvider = new AssemblyInformationProvider();
-			var ioManager = new DefaultIOManager();
+			var fileSystem = new FileSystem();
+			var ioManager = new DefaultIOManager(fileSystem);
 			return new ServerFactory(
 				assemblyInformationProvider,
-				ioManager);
+				ioManager,
+				fileSystem);
 		}

 		/// <summary>
@@ -154,11 +157,13 @@ namespace Tgstation.Server.Host.Core
 		/// <param name="assemblyInformationProvider">The <see cref="IAssemblyInformationProvider"/> needed for configuration.</param>
 		/// <param name="ioManager">The <see cref="IIOManager"/> needed for configuration.</param>
 		/// <param name="postSetupServices">The <see cref="IPostSetupServices"/> needed for configuration.</param>
+		/// <param name="fileSystem">The <see cref="IFileSystem"/> needed for configuration.</param>
 		public void ConfigureServices(
 			IServiceCollection services,
 			IAssemblyInformationProvider assemblyInformationProvider,
 			IIOManager ioManager,
-			IPostSetupServices postSetupServices)
+			IPostSetupServices postSetupServices,
+			IFileSystem fileSystem)
 		{
 			ConfigureServices(services, assemblyInformationProvider, ioManager);

@@ -485,8 +490,7 @@ namespace Tgstation.Server.Host.Core
 				services => services
 					.GetRequiredService<IRepositoryManagerFactory>()
 					.CreateRepositoryManager(
-						new ResolvingIOManager(
-							services.GetRequiredService<IIOManager>(),
+						services.GetRequiredService<IIOManager>().CreateResolverForSubdirectory(
 							openDreamRepositoryDirectory),
 						new NoopEventConsumer()));

@@ -542,6 +546,7 @@ namespace Tgstation.Server.Host.Core
 			services.AddSingleton<ISynchronousIOManager, SynchronousIOManager>();
 			services.AddSingleton<IServerPortProvider, ServerPortProivder>();
 			services.AddSingleton<ITopicClientFactory, TopicClientFactory>();
+			services.AddSingleton(fileSystem);
 			services.AddHostedService<CommandPipeManager>();
 			services.AddHostedService<VersionReportingService>();

@@ -940,10 +945,7 @@ namespace Tgstation.Server.Host.Core
 							options.Scope.Add(OpenIdConnectScope.OpenId);
 							options.Scope.Add(OpenIdConnectScope.OfflineAccess);

-#if DEBUG
 							options.RequireHttpsMetadata = false;
-#endif
-
 							options.SaveTokens = true;
 							options.ResponseType = OpenIdConnectResponseType.Code;
 							options.MapInboundClaims = false;
@@ -1,4 +1,5 @@
 using System;
+using System.IO.Abstractions;

 using Microsoft.AspNetCore.Builder;
 using Microsoft.AspNetCore.Hosting;
@@ -26,24 +27,27 @@ namespace Tgstation.Server.Host.Extensions
 		/// <param name="builder">The <see cref="IWebHostBuilder"/> to configure.</param>
 		/// <param name="assemblyInformationProvider">The <see cref="IAssemblyInformationProvider"/> to use.</param>
 		/// <param name="ioManager">The <see cref="IIOManager"/> to use.</param>
-		/// <returns>The configured <paramref name="builder"/>.</returns>
 		/// <param name="postSetupServices">The <see cref="IPostSetupServices"/> to use.</param>
+		/// <param name="fileSystem">The <see cref="IFileSystem"/> to use.</param>
+		/// <returns>The configured <paramref name="builder"/>.</returns>
 		public static IWebHostBuilder UseApplication(
 			this IWebHostBuilder builder,
 			IAssemblyInformationProvider assemblyInformationProvider,
 			IIOManager ioManager,
-			IPostSetupServices postSetupServices)
+			IPostSetupServices postSetupServices,
+			IFileSystem fileSystem)
 		{
 			ArgumentNullException.ThrowIfNull(builder);
 			ArgumentNullException.ThrowIfNull(assemblyInformationProvider);
 			ArgumentNullException.ThrowIfNull(ioManager);
 			ArgumentNullException.ThrowIfNull(postSetupServices);
+			ArgumentNullException.ThrowIfNull(fileSystem);

 			return builder.ConfigureServices(
 				(context, services) =>
 				{
 					var application = new Application(context.Configuration, context.HostingEnvironment);
-					application.ConfigureServices(services, assemblyInformationProvider, ioManager, postSetupServices);
+					application.ConfigureServices(services, assemblyInformationProvider, ioManager, postSetupServices, fileSystem);
 					services.AddSingleton(application);
 				})
 				.Configure(ConfigureApplication);
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Abstractions;
 using System.IO.Compression;
 using System.Linq;
 using System.Threading;
@@ -30,12 +31,32 @@ namespace Tgstation.Server.Host.IO
 		/// </summary>
 		public const TaskCreationOptions BlockingTaskCreationOptions = TaskCreationOptions.None;

+		/// <inheritdoc />
+		public char DirectorySeparatorChar => fileSystem.Path.DirectorySeparatorChar;
+
+		/// <inheritdoc />
+		public char AltDirectorySeparatorChar => fileSystem.Path.AltDirectorySeparatorChar;
+
+		/// <summary>
+		/// The backing <see cref="IFileSystem"/>.
+		/// </summary>
+		readonly IFileSystem fileSystem;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="DefaultIOManager"/> class.
+		/// </summary>
+		/// <param name="fileSystem">The value of <see cref="fileSystem"/>.</param>
+		public DefaultIOManager(IFileSystem fileSystem)
+		{
+			this.fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
+		}
+
 		/// <summary>
 		/// Recursively empty a directory.
 		/// </summary>
 		/// <param name="dir"><see cref="DirectoryInfo"/> of the directory to empty.</param>
 		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
-		static void NormalizeAndDelete(DirectoryInfo dir, CancellationToken cancellationToken)
+		static void NormalizeAndDelete(IDirectoryInfo dir, CancellationToken cancellationToken)
 		{
 			cancellationToken.ThrowIfCancellationRequested();

@@ -111,7 +132,7 @@ namespace Tgstation.Server.Host.IO
 		}

 		/// <inheritdoc />
-		public string ConcatPath(params string[] paths) => Path.Combine(paths);
+		public string ConcatPath(params string[] paths) => fileSystem.Path.Combine(paths);

 		/// <inheritdoc />
 		public async ValueTask CopyFile(string src, string dest, CancellationToken cancellationToken)
@@ -120,7 +141,7 @@ namespace Tgstation.Server.Host.IO
 			ArgumentNullException.ThrowIfNull(dest);

 			// tested to hell and back, these are the optimal buffer sizes
-			await using var srcStream = new FileStream(
+			await using var srcStream = fileSystem.FileStream.New(
 				ResolvePath(src),
 				FileMode.Open,
 				FileAccess.Read,
@@ -134,41 +155,40 @@ namespace Tgstation.Server.Host.IO
 		}

 		/// <inheritdoc />
-		public Task CreateDirectory(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => Directory.CreateDirectory(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);
+		public Task CreateDirectory(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => fileSystem.Directory.CreateDirectory(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);

 		/// <inheritdoc />
 		public Task DeleteDirectory(string path, CancellationToken cancellationToken)
-		{
-			path = ResolvePath(path);
-			var di = new DirectoryInfo(path);
-			if (!di.Exists)
-				return Task.CompletedTask;
-
-			return Task.Factory.StartNew(
-				() => NormalizeAndDelete(di, cancellationToken),
+			=> Task.Factory.StartNew(
+				() =>
+				{
+					var di = fileSystem.DirectoryInfo.New(
+						ResolvePath(path));
+					if (di.Exists)
+						NormalizeAndDelete(di, cancellationToken);
+				},
 				cancellationToken,
 				BlockingTaskCreationOptions,
 				TaskScheduler.Current);
-		}

 		/// <inheritdoc />
-		public Task DeleteFile(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => File.Delete(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);
+		public Task DeleteFile(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => fileSystem.File.Delete(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);

 		/// <inheritdoc />
-		public Task<bool> FileExists(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => File.Exists(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);
+		public Task<bool> FileExists(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => fileSystem.File.Exists(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);

 		/// <inheritdoc />
-		public Task<bool> DirectoryExists(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => Directory.Exists(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);
+		public Task<bool> DirectoryExists(string path, CancellationToken cancellationToken) => Task.Factory.StartNew(() => fileSystem.Directory.Exists(ResolvePath(path)), cancellationToken, BlockingTaskCreationOptions, TaskScheduler.Current);

 		/// <inheritdoc />
-		public string GetDirectoryName(string path) => Path.GetDirectoryName(path ?? throw new ArgumentNullException(nameof(path)))
+		public string GetDirectoryName(string path) => fileSystem.Path.GetDirectoryName(path ?? throw new ArgumentNullException(nameof(path)))
 			?? throw new InvalidOperationException($"Null was returned. Path ({path}) must be rooted. This is not supported!");

 		/// <inheritdoc />
-		public string GetFileName(string path) => Path.GetFileName(path ?? throw new ArgumentNullException(nameof(path)));
+		public string GetFileName(string path) => fileSystem.Path.GetFileName(path ?? throw new ArgumentNullException(nameof(path)));

 		/// <inheritdoc />
-		public string GetFileNameWithoutExtension(string path) => Path.GetFileNameWithoutExtension(path ?? throw new ArgumentNullException(nameof(path)));
+		public string GetFileNameWithoutExtension(string path) => fileSystem.Path.GetFileNameWithoutExtension(path ?? throw new ArgumentNullException(nameof(path)));

 		/// <inheritdoc />
 		public Task<List<string>> GetFilesWithExtension(string path, string extension, bool recursive, CancellationToken cancellationToken) => Task.Factory.StartNew(
@@ -177,7 +197,7 @@ namespace Tgstation.Server.Host.IO
 				path = ResolvePath(path);
 				ArgumentNullException.ThrowIfNull(extension);
 				var results = new List<string>();
-				foreach (var fileName in Directory.EnumerateFiles(
+				foreach (var fileName in fileSystem.Directory.EnumerateFiles(
 					path,
 					$"*.{extension}",
 					recursive ? SearchOption.AllDirectories : SearchOption.TopDirectoryOnly))
@@ -199,7 +219,7 @@ namespace Tgstation.Server.Host.IO
 				ArgumentNullException.ThrowIfNull(destination);
 				source = ResolvePath(source ?? throw new ArgumentNullException(nameof(source)));
 				destination = ResolvePath(destination);
-				File.Move(source, destination);
+				fileSystem.File.Move(source, destination);
 			},
 			cancellationToken,
 			BlockingTaskCreationOptions,
@@ -212,7 +232,7 @@ namespace Tgstation.Server.Host.IO
 				ArgumentNullException.ThrowIfNull(destination);
 				source = ResolvePath(source ?? throw new ArgumentNullException(nameof(source)));
 				destination = ResolvePath(destination);
-				Directory.Move(source, destination);
+				fileSystem.Directory.Move(source, destination);
 			},
 			cancellationToken,
 			BlockingTaskCreationOptions,
@@ -221,7 +241,7 @@ namespace Tgstation.Server.Host.IO
 		/// <inheritdoc />
 		public async ValueTask<byte[]> ReadAllBytes(string path, CancellationToken cancellationToken)
 		{
-			await using var file = CreateAsyncSequentialReadStream(path);
+			await using var file = CreateAsyncReadStream(path, true, true);
 			byte[] buf;
 			buf = new byte[file.Length];
 			await file.ReadAsync(buf, cancellationToken);
@@ -229,10 +249,12 @@ namespace Tgstation.Server.Host.IO
 		}

 		/// <inheritdoc />
-		public string ResolvePath() => ResolvePath(CurrentDirectory);
+		public string ResolvePath()
+			=> ResolvePath(CurrentDirectory);

 		/// <inheritdoc />
-		public virtual string ResolvePath(string path) => Path.GetFullPath(path ?? throw new ArgumentNullException(nameof(path)));
+		public virtual string ResolvePath(string path)
+			=> fileSystem.Path.GetFullPath(path ?? throw new ArgumentNullException(nameof(path)));

 		/// <inheritdoc />
 		public async ValueTask WriteAllBytes(string path, byte[] contents, CancellationToken cancellationToken)
@@ -242,10 +264,10 @@ namespace Tgstation.Server.Host.IO
 		}

 		/// <inheritdoc />
-		public FileStream CreateAsyncSequentialWriteStream(string path)
+		public Stream CreateAsyncSequentialWriteStream(string path)
 		{
 			path = ResolvePath(path);
-			return new FileStream(
+			return fileSystem.FileStream.New(
 				path,
 				FileMode.Create,
 				FileAccess.Write,
@@ -255,16 +277,18 @@ namespace Tgstation.Server.Host.IO
 		}

 		/// <inheritdoc />
-		public FileStream CreateAsyncSequentialReadStream(string path)
+		public Stream CreateAsyncReadStream(string path, bool sequental, bool shareWrite)
 		{
 			path = ResolvePath(path);
-			return new FileStream(
+			return fileSystem.FileStream.New(
 				path,
 				FileMode.Open,
 				FileAccess.Read,
-				FileShare.ReadWrite | FileShare.Delete,
+				FileShare.ReadWrite | FileShare.Delete | (shareWrite ? FileShare.Write : FileShare.None),
 				DefaultBufferSize,
-				FileOptions.Asynchronous | FileOptions.SequentialScan);
+				sequental
+					? FileOptions.Asynchronous | FileOptions.SequentialScan
+					: FileOptions.Asynchronous);
 		}

 		/// <inheritdoc />
@@ -274,7 +298,7 @@ namespace Tgstation.Server.Host.IO
 				path = ResolvePath(path);
 				var results = new List<string>();
 				cancellationToken.ThrowIfCancellationRequested();
-				foreach (var directoryName in Directory.EnumerateDirectories(path))
+				foreach (var directoryName in fileSystem.Directory.EnumerateDirectories(path))
 				{
 					results.Add(directoryName);
 					cancellationToken.ThrowIfCancellationRequested();
@@ -293,7 +317,7 @@ namespace Tgstation.Server.Host.IO
 				path = ResolvePath(path);
 				var results = new List<string>();
 				cancellationToken.ThrowIfCancellationRequested();
-				foreach (var fileName in Directory.EnumerateFiles(path))
+				foreach (var fileName in fileSystem.Directory.EnumerateFiles(path))
 				{
 					results.Add(fileName);
 					cancellationToken.ThrowIfCancellationRequested();
@@ -331,8 +355,8 @@ namespace Tgstation.Server.Host.IO
 		public bool PathContainsParentAccess(string path) => path
 			?.Split(
 				[
-					Path.DirectorySeparatorChar,
-					Path.AltDirectorySeparatorChar,
+					fileSystem.Path.DirectorySeparatorChar,
+					fileSystem.Path.AltDirectorySeparatorChar,
 				])
 			.Any(x => x == "..")
 			?? throw new ArgumentNullException(nameof(path));
@@ -342,22 +366,13 @@ namespace Tgstation.Server.Host.IO
 			() =>
 			{
 				path = ResolvePath(path ?? throw new ArgumentNullException(nameof(path)));
-				var fileInfo = new FileInfo(path);
+				var fileInfo = fileSystem.FileInfo.New(path);
 				return new DateTimeOffset(fileInfo.LastWriteTimeUtc);
 			},
 			cancellationToken,
 			BlockingTaskCreationOptions,
 			TaskScheduler.Current);

-		/// <inheritdoc />
-		public FileStream GetFileStream(string path, bool shareWrite) => new(
-			ResolvePath(path),
-			FileMode.Open,
-			FileAccess.Read,
-			FileShare.Read | FileShare.Delete | (shareWrite ? FileShare.Write : FileShare.None),
-			DefaultBufferSize,
-			true);
-
 		/// <inheritdoc />
 		public Task<bool> PathIsChildOf(string parentPath, string childPath, CancellationToken cancellationToken) => Task.Factory.StartNew(
 			() =>
@@ -369,8 +384,8 @@ namespace Tgstation.Server.Host.IO
 					return true;

 				// https://stackoverflow.com/questions/5617320/given-full-path-check-if-path-is-subdirectory-of-some-other-path-or-otherwise?lq=1
-				var di1 = new DirectoryInfo(parentPath);
-				var di2 = new DirectoryInfo(childPath);
+				var di1 = fileSystem.DirectoryInfo.New(parentPath);
+				var di2 = fileSystem.DirectoryInfo.New(childPath);
 				while (di2.Parent != null)
 				{
 					if (di2.Parent.FullName == di1.FullName)
@@ -385,6 +400,33 @@ namespace Tgstation.Server.Host.IO
 			BlockingTaskCreationOptions,
 			TaskScheduler.Current);

+		/// <inheritdoc />
+		public Task<IDirectoryInfo> DirectoryInfo(string path, CancellationToken cancellationToken)
+			=> Task.Factory.StartNew(
+				() => fileSystem.DirectoryInfo.New(ResolvePath(path)),
+				cancellationToken,
+				BlockingTaskCreationOptions,
+				TaskScheduler.Current);
+
+		/// <inheritdoc />
+		public bool IsPathRooted(string path)
+			=> fileSystem.Path.IsPathRooted(path);
+
+		/// <inheritdoc />
+		public IIOManager CreateResolverForSubdirectory(string subdirectoryPath)
+		{
+			ArgumentNullException.ThrowIfNull(subdirectoryPath);
+
+			if (!Path.IsPathRooted(subdirectoryPath))
+				subdirectoryPath = ConcatPath(
+					ResolvePath(),
+					subdirectoryPath);
+
+			return new ResolvingIOManager(
+				fileSystem,
+				subdirectoryPath);
+		}
+
 		/// <summary>
 		/// Copies a directory from <paramref name="src"/> to <paramref name="dest"/>.
 		/// </summary>
@@ -403,7 +445,7 @@ namespace Tgstation.Server.Host.IO
 			SemaphoreSlim? semaphore,
 			CancellationToken cancellationToken)
 		{
-			var dir = new DirectoryInfo(src);
+			var dir = fileSystem.DirectoryInfo.New(src);
 			Task? subdirCreationTask = null;
 			foreach (var subDirectory in dir.EnumerateDirectories())
 			{
@@ -411,7 +453,7 @@ namespace Tgstation.Server.Host.IO
 					continue;

 				var checkingSubdirCreationTask = true;
-				foreach (var copyTask in CopyDirectoryImpl(subDirectory.FullName, Path.Combine(dest, subDirectory.Name), null, postCopyCallback, semaphore, cancellationToken))
+				foreach (var copyTask in CopyDirectoryImpl(subDirectory.FullName, fileSystem.Path.Combine(dest, subDirectory.Name), null, postCopyCallback, semaphore, cancellationToken))
 				{
 					if (subdirCreationTask == null)
 					{
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -11,6 +12,23 @@ namespace Tgstation.Server.Host.IO
 	/// </summary>
 	public interface IIOManager
 	{
+		/// <summary>
+		/// Gets the primary directory separator character.
+		/// </summary>
+		char DirectorySeparatorChar { get; }
+
+		/// <summary>
+		/// Gets the alternative directory separator character.
+		/// </summary>
+		char AltDirectorySeparatorChar { get; }
+
+		/// <summary>
+		/// Create a new <see cref="IIOManager"/> that resolves paths to the specified <paramref name="subdirectoryPath"/>.
+		/// </summary>
+		/// <param name="subdirectoryPath">A relative or absolute path that the new <see cref="IIOManager"/> will resolve as its current directory.</param>
+		/// <returns>A new <see cref="IIOManager"/>.</returns>
+		IIOManager CreateResolverForSubdirectory(string subdirectoryPath);
+
 		/// <summary>
 		/// Retrieve the full path of the current working directory.
 		/// </summary>
@@ -117,15 +135,17 @@ namespace Tgstation.Server.Host.IO
 		/// Creates an asynchronous <see cref="FileStream"/> for sequential writing.
 		/// </summary>
 		/// <param name="path">The path of the file to write, will be truncated.</param>
-		/// <returns>The open <see cref="FileStream"/>.</returns>
-		FileStream CreateAsyncSequentialWriteStream(string path);
+		/// <returns>The open <see cref="Stream"/>.</returns>
+		Stream CreateAsyncSequentialWriteStream(string path);

 		/// <summary>
 		/// Creates an asynchronous <see cref="FileStream"/> for sequential reading.
 		/// </summary>
 		/// <param name="path">The path of the file to write, will be truncated.</param>
-		/// <returns>The open <see cref="FileStream"/>.</returns>
-		FileStream CreateAsyncSequentialReadStream(string path);
+		/// <param name="sequential">If the sequential read flag should be added.</param>
+		/// <param name="shareWrite">If <see cref="FileShare.Write"/> should be used.</param>
+		/// <returns>The open <see cref="Stream"/>.</returns>
+		Stream CreateAsyncReadStream(string path, bool sequential, bool shareWrite);

 		/// <summary>
 		/// Writes some <paramref name="contents"/> to a file at <paramref name="path"/> overwriting previous content.
@@ -230,12 +250,18 @@ namespace Tgstation.Server.Host.IO
 		Task<DateTimeOffset> GetLastModified(string path, CancellationToken cancellationToken);

 		/// <summary>
-		/// Gets the <see cref="Stream"/> for a given file <paramref name="path"/>.
+		/// Gets a <see cref="IDirectoryInfo"/> for the given <paramref name="path"/>.
 		/// </summary>
-		/// <param name="path">The path of the file.</param>
-		/// <param name="shareWrite">If <see cref="FileShare.Write"/> should be used.</param>
-		/// <returns>The <see cref="FileStream"/> of the file.</returns>
-		/// <remarks>This function is sychronous.</remarks>
-		FileStream GetFileStream(string path, bool shareWrite);
+		/// <param name="path">The path to get <see cref="IDirectoryInfo"/> for.</param>
+		/// <param name="cancellationToken">The <see cref="CancellationToken"/> for the operation.</param>
+		/// <returns>A <see cref="Task{TResult}"/> resulting in the <see cref="IDirectoryInfo"/> of the <paramref name="path"/>.</returns>
+		Task<IDirectoryInfo> DirectoryInfo(string path, CancellationToken cancellationToken);
+
+		/// <summary>
+		/// Check if a given <paramref name="path"/> is at the root level of the filesystem.
+		/// </summary>
+		/// <param name="path">The path to check.</param>
+		/// <returns><see langword="true"/> if the path is rooted, <see langword="false"/> otherwise.</returns>
+		bool IsPathRooted(string path);
 	}
 }
@@ -63,5 +63,12 @@ namespace Tgstation.Server.Host.IO
 		/// <param name="path">The path to check.</param>
 		/// <returns><see langword="true"/> if <paramref name="path"/> is a directory, <see langword="false"/> otherwise.</returns>
 		bool IsDirectory(string path);
+
+		/// <summary>
+		/// Gets the <see cref="Stream"/> for a given file <paramref name="path"/> without write share.
+		/// </summary>
+		/// <param name="path">The path of the file.</param>
+		/// <returns>The <see cref="Stream"/> of the file.</returns>
+		Stream GetFileStream(string path);
 	}
 }
@@ -1,5 +1,5 @@
 using System;
-using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -15,6 +15,20 @@ namespace Tgstation.Server.Host.IO
 		/// <inheritdoc />
 		public bool SymlinkedDirectoriesAreDeletedAsFiles => true;

+		/// <summary>
+		/// The <see cref="IFileSystem"/> to use.
+		/// </summary>
+		readonly IFileSystem fileSystem;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="PosixFilesystemLinkFactory"/> class.
+		/// </summary>
+		/// <param name="fileSystem">The value of <see cref="fileSystem"/>.</param>
+		public PosixFilesystemLinkFactory(IFileSystem fileSystem)
+		{
+			this.fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
+		}
+
 		/// <inheritdoc />
 		public Task CreateHardLink(string targetPath, string linkPath, CancellationToken cancellationToken) => Task.Factory.StartNew(
 			() =>
@@ -39,7 +53,7 @@ namespace Tgstation.Server.Host.IO
 				ArgumentNullException.ThrowIfNull(linkPath);

 				UnixFileSystemInfo fsInfo;
-				var isFile = File.Exists(targetPath);
+				var isFile = fileSystem.File.Exists(targetPath);
 				cancellationToken.ThrowIfCancellationRequested();
 				if (isFile)
 					fsInfo = new UnixFileInfo(targetPath);
@@ -1,5 +1,5 @@
 using System;
-using System.IO;
+using System.IO.Abstractions;

 namespace Tgstation.Server.Host.IO
 {
@@ -16,20 +16,20 @@ namespace Tgstation.Server.Host.IO
 		/// <summary>
 		/// Initializes a new instance of the <see cref="ResolvingIOManager"/> class.
 		/// </summary>
-		/// <param name="parent">The <see cref="IIOManager"/> that resolves to the directory to work out of.</param>
+		/// <param name="fileSystem">The <see cref="IFileSystem"/> for the <see cref="DefaultIOManager"/>.</param>
 		/// <param name="subdirectory">The value of <see cref="subdirectory"/>.</param>
-		public ResolvingIOManager(IIOManager parent, string subdirectory)
+		public ResolvingIOManager(
+			IFileSystem fileSystem,
+			string subdirectory)
+			: base(fileSystem)
 		{
-			ArgumentNullException.ThrowIfNull(parent);
-			ArgumentNullException.ThrowIfNull(subdirectory);
-
-			this.subdirectory = ConcatPath(parent.ResolvePath(), subdirectory);
+			this.subdirectory = subdirectory ?? throw new ArgumentNullException(nameof(subdirectory));
 		}

 		/// <inheritdoc />
 		public override string ResolvePath(string path)
 		{
-			if (!Path.IsPathRooted(path))
+			if (!IsPathRooted(path))
 				return base.ResolvePath(ConcatPath(subdirectory, path));
 			return path;
 		}
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Security.Cryptography;
 using System.Threading;
@@ -13,6 +14,11 @@ namespace Tgstation.Server.Host.IO
 	/// <inheritdoc />
 	sealed class SynchronousIOManager : ISynchronousIOManager
 	{
+		/// <summary>
+		/// The <see cref="IFileSystem"/> to use.
+		/// </summary>
+		readonly IFileSystem fileSystem;
+
 		/// <summary>
 		/// The <see cref="ILogger"/> for the <see cref="SynchronousIOManager"/>.
 		/// </summary>
@@ -21,9 +27,11 @@ namespace Tgstation.Server.Host.IO
 		/// <summary>
 		/// Initializes a new instance of the <see cref="SynchronousIOManager"/> class.
 		/// </summary>
+		/// <param name="fileSystem">The value of <see cref="fileSystem"/>.</param>
 		/// <param name="logger">The value of <see cref="logger"/>.</param>
-		public SynchronousIOManager(ILogger<SynchronousIOManager> logger)
+		public SynchronousIOManager(IFileSystem fileSystem, ILogger<SynchronousIOManager> logger)
 		{
+			this.fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
 			this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
 		}

@@ -33,32 +41,32 @@ namespace Tgstation.Server.Host.IO
 			if (IsDirectory(path))
 				return true;
 			cancellationToken.ThrowIfCancellationRequested();
-			Directory.CreateDirectory(path);
+			fileSystem.Directory.CreateDirectory(path);
 			return false;
 		}

 		/// <inheritdoc />
 		public bool DeleteDirectory(string path)
 		{
-			if (File.Exists(path))
+			if (fileSystem.File.Exists(path))
 				return false;

-			if (!Directory.Exists(path))
+			if (!fileSystem.Directory.Exists(path))
 				return true;

-			if (Directory.EnumerateFileSystemEntries(path).Any())
+			if (fileSystem.Directory.EnumerateFileSystemEntries(path).Any())
 				return false;

-			Directory.Delete(path);
+			fileSystem.Directory.Delete(path);
 			return true;
 		}

 		/// <inheritdoc />
 		public IEnumerable<string> GetDirectories(string path, CancellationToken cancellationToken)
 		{
-			foreach (var directoryName in Directory.EnumerateDirectories(path))
+			foreach (var directoryName in fileSystem.Directory.EnumerateDirectories(path))
 			{
-				yield return Path.GetFileName(directoryName);
+				yield return fileSystem.Path.GetFileName(directoryName);
 				cancellationToken.ThrowIfCancellationRequested();
 			}
 		}
@@ -66,9 +74,9 @@ namespace Tgstation.Server.Host.IO
 		/// <inheritdoc />
 		public IEnumerable<string> GetFiles(string path, CancellationToken cancellationToken)
 		{
-			foreach (var fileName in Directory.EnumerateFiles(path))
+			foreach (var fileName in fileSystem.Directory.EnumerateFiles(path))
 			{
-				yield return Path.GetFileName(fileName);
+				yield return fileSystem.Path.GetFileName(fileName);
 				cancellationToken.ThrowIfCancellationRequested();
 			}
 		}
@@ -77,14 +85,14 @@ namespace Tgstation.Server.Host.IO
 		public bool IsDirectory(string path)
 		{
 			ArgumentNullException.ThrowIfNull(path);
-			return Directory.Exists(path);
+			return fileSystem.Directory.Exists(path);
 		}

 		/// <inheritdoc />
 		public byte[] ReadFile(string path)
 		{
 			ArgumentNullException.ThrowIfNull(path);
-			return File.ReadAllBytes(path);
+			return fileSystem.File.ReadAllBytes(path);
 		}

 		/// <inheritdoc />
@@ -94,16 +102,16 @@ namespace Tgstation.Server.Host.IO
 			ArgumentNullException.ThrowIfNull(data);

 			cancellationToken.ThrowIfCancellationRequested();
-			var directory = Path.GetDirectoryName(path) ?? throw new ArgumentException("path cannot be rooted!", nameof(path));
-			Directory.CreateDirectory(directory);
+			var directory = fileSystem.Path.GetDirectoryName(path) ?? throw new ArgumentException("path cannot be rooted!", nameof(path));
+			fileSystem.Directory.CreateDirectory(directory);

-			var newFile = !File.Exists(path);
+			var newFile = !fileSystem.File.Exists(path);

 			cancellationToken.ThrowIfCancellationRequested();

 			logger.LogTrace("Starting checked write to {path} ({fileType} file)", path, newFile ? "New" : "Pre-existing");

-			using (var file = File.Open(path, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
+			using (var file = fileSystem.File.Open(path, FileMode.OpenOrCreate, FileAccess.ReadWrite, FileShare.None))
 			{
 				cancellationToken.ThrowIfCancellationRequested();

@@ -160,10 +168,20 @@ namespace Tgstation.Server.Host.IO
 			if (data.Length == 0)
 			{
 				logger.LogDebug("Stream is empty, deleting file");
-				File.Delete(path);
+				fileSystem.File.Delete(path);
 			}

 			return true;
 		}
+
+		/// <inheritdoc />
+		public Stream GetFileStream(string path)
+			=> fileSystem.FileStream.New(
+				path,
+				FileMode.Open,
+				FileAccess.Read,
+				FileShare.Read | FileShare.Delete,
+				DefaultIOManager.DefaultBufferSize,
+				true);
 	}
 }
@@ -1,6 +1,6 @@
 using System;
 using System.ComponentModel;
-using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -16,6 +16,20 @@ namespace Tgstation.Server.Host.IO
 		/// <inheritdoc />
 		public bool SymlinkedDirectoriesAreDeletedAsFiles => false;

+		/// <summary>
+		/// The <see cref="IFileSystem"/> to use.
+		/// </summary>
+		readonly IFileSystem fileSystem;
+
+		/// <summary>
+		/// Initializes a new instance of the <see cref="WindowsFilesystemLinkFactory"/> class.
+		/// </summary>
+		/// <param name="fileSystem">The value of <see cref="fileSystem"/>.</param>
+		public WindowsFilesystemLinkFactory(IFileSystem fileSystem)
+		{
+			this.fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
+		}
+
 		/// <inheritdoc />
 		public Task CreateHardLink(string targetPath, string linkPath, CancellationToken cancellationToken)
 			=> throw new NotSupportedException();
@@ -28,7 +42,7 @@ namespace Tgstation.Server.Host.IO
 				ArgumentNullException.ThrowIfNull(linkPath);

 				// check if its not a file
-				var flags = File.Exists(targetPath) ? NativeMethods.CreateSymbolicLinkFlags.None : NativeMethods.CreateSymbolicLinkFlags.Directory;
+				var flags = fileSystem.File.Exists(targetPath) ? NativeMethods.CreateSymbolicLinkFlags.None : NativeMethods.CreateSymbolicLinkFlags.Directory;

 				/*
 				 * no don't fucking use this
@@ -1,4 +1,5 @@
 using System;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -29,23 +30,33 @@ namespace Tgstation.Server.Host
 		/// </summary>
 		public const string AppSettings = "appsettings";

+		/// <inheritdoc />
+		public IIOManager IOManager { get; }
+
 		/// <summary>
 		/// The <see cref="IAssemblyInformationProvider"/> for the <see cref="ServerFactory"/>.
 		/// </summary>
 		readonly IAssemblyInformationProvider assemblyInformationProvider;

-		/// <inheritdoc />
-		public IIOManager IOManager { get; }
+		/// <summary>
+		/// The <see cref="IFileSystem"/> for the <see cref="ServerFactory"/>.
+		/// </summary>
+		readonly IFileSystem fileSystem;

 		/// <summary>
 		/// Initializes a new instance of the <see cref="ServerFactory"/> class.
 		/// </summary>
 		/// <param name="assemblyInformationProvider">The value of <see cref="assemblyInformationProvider"/>.</param>
 		/// <param name="ioManager">The value of <see cref="IOManager"/>.</param>
-		internal ServerFactory(IAssemblyInformationProvider assemblyInformationProvider, IIOManager ioManager)
+		/// <param name="fileSystem">The value of <see cref="fileSystem"/>.</param>
+		internal ServerFactory(
+			IAssemblyInformationProvider assemblyInformationProvider,
+			IIOManager ioManager,
+			IFileSystem fileSystem)
 		{
 			this.assemblyInformationProvider = assemblyInformationProvider ?? throw new ArgumentNullException(nameof(assemblyInformationProvider));
 			IOManager = ioManager ?? throw new ArgumentNullException(nameof(ioManager));
+			this.fileSystem = fileSystem ?? throw new ArgumentNullException(nameof(fileSystem));
 		}

 		/// <inheritdoc />
@@ -160,7 +171,7 @@ namespace Tgstation.Server.Host
 						})
 						.UseIIS()
 						.UseIISIntegration()
-						.UseApplication(assemblyInformationProvider, IOManager, postSetupServices)
+						.UseApplication(assemblyInformationProvider, IOManager, postSetupServices, fileSystem)
 						.SuppressStatusMessages(true)
 						.UseShutdownTimeout(
 							TimeSpan.FromMinutes(
@@ -304,7 +304,7 @@ namespace Tgstation.Server.Host.Setup
 		/// <returns>A <see cref="ValueTask{TResult}"/> resulting in the SQLite database path to store in the configuration.</returns>
 		async ValueTask<string?> ValidateNonExistantSqliteDBName(string databaseName, CancellationToken cancellationToken)
 		{
-			var dbPathIsRooted = Path.IsPathRooted(databaseName);
+			var dbPathIsRooted = ioManager.IsPathRooted(databaseName);
 			var resolvedPath = ioManager.ResolvePath(
 				dbPathIsRooted
 					? databaseName
@@ -64,39 +64,6 @@ namespace Tgstation.Server.Host.System
 			this.logger = logger ?? throw new ArgumentNullException(nameof(logger));
 		}

-		/// <summary>
-		/// Gets potential paths to the gcore executable.
-		/// </summary>
-		/// <returns>The potential paths to the gcore executable.</returns>
-		static IEnumerable<string> GetPotentialGCorePaths()
-		{
-			var enviromentPath = Environment.GetEnvironmentVariable("PATH");
-			IEnumerable<string> enumerator;
-			if (enviromentPath == null)
-				enumerator = Enumerable.Empty<string>();
-			else
-			{
-				var paths = enviromentPath.Split(';');
-				enumerator = paths
-					.Select(x => x.Split(':'))
-					.SelectMany(x => x);
-			}
-
-			var exeName = "gcore";
-
-			enumerator = enumerator
-				.Concat(new List<string>(2)
-				{
-					"/usr/bin",
-					"/usr/share/bin",
-					"/bin",
-				});
-
-			enumerator = enumerator.Select(x => Path.Combine(x, exeName));
-
-			return enumerator;
-		}
-
 		/// <inheritdoc />
 		public void ResumeProcess(global::System.Diagnostics.Process process)
 		{
@@ -201,8 +168,8 @@ namespace Tgstation.Server.Host.System
 			{
 				// can't use ReadAllBytes here, /proc files have 0 length so the buffer is initialized to empty
 				// https://stackoverflow.com/questions/12237712/how-can-i-show-the-size-of-files-in-proc-it-should-not-be-size-zero
-				await using var fileStream = ioManager.CreateAsyncSequentialReadStream(
-					"/proc/self/oom_score_adj");
+				await using var fileStream = ioManager.CreateAsyncReadStream(
+					"/proc/self/oom_score_adj", true, true);
 				using var reader = new StreamReader(fileStream, Encoding.UTF8, leaveOpen: true);
 				originalString = await reader.ReadToEndAsync(cancellationToken);
 			}
@@ -255,5 +222,38 @@ namespace Tgstation.Server.Host.System
 				Encoding.UTF8.GetBytes(adjustedValue.ToString(CultureInfo.InvariantCulture)),
 				cancellationToken);
 		}
+
+		/// <summary>
+		/// Gets potential paths to the gcore executable.
+		/// </summary>
+		/// <returns>The potential paths to the gcore executable.</returns>
+		IEnumerable<string> GetPotentialGCorePaths()
+		{
+			var enviromentPath = Environment.GetEnvironmentVariable("PATH");
+			IEnumerable<string> enumerator;
+			if (enviromentPath == null)
+				enumerator = Enumerable.Empty<string>();
+			else
+			{
+				var paths = enviromentPath.Split(';');
+				enumerator = paths
+					.Select(x => x.Split(':'))
+					.SelectMany(x => x);
+			}
+
+			var exeName = "gcore";
+
+			enumerator = enumerator
+				.Concat(new List<string>(2)
+				{
+					"/usr/bin",
+					"/usr/share/bin",
+					"/bin",
+				});
+
+			enumerator = enumerator.Select(x => ioManager.ConcatPath(x, exeName));
+
+			return enumerator;
+		}
 	}
 }
@@ -145,6 +145,7 @@ namespace Tgstation.Server.Host.System
 				throw new JobException(ErrorCode.GameServerOffline, ex);
 			}

+			// Windows API so has to be a real FS
 			await using var fileStream = new FileStream(outputFile, FileMode.CreateNew);

 			await Task.Factory.StartNew(
@@ -96,41 +96,41 @@
    <!-- Usage: .env file parsing -->
    <PackageReference Include="DotEnv.Core" Version="3.1.0" />
    <!-- Usage: Text formatter for Elasticsearch logging plugin -->
-    <PackageReference Include="Elastic.CommonSchema.Serilog" Version="8.12.3" />
+    <PackageReference Include="Elastic.CommonSchema.Serilog" Version="8.18.2" />
    <!-- Usage: GraphQL API Engine -->
-    <PackageReference Include="HotChocolate.AspNetCore" Version="15.1.3" />
+    <PackageReference Include="HotChocolate.AspNetCore" Version="15.1.8" />
    <!-- Usage: GraphQL Authorization Plugin -->
-    <PackageReference Include="HotChocolate.AspNetCore.Authorization" Version="15.1.3" />
+    <PackageReference Include="HotChocolate.AspNetCore.Authorization" Version="15.1.8" />
    <!-- Usage: GraphQL IDatabaseContext support -->
-    <PackageReference Include="HotChocolate.Data.EntityFramework" Version="15.1.3" />
+    <PackageReference Include="HotChocolate.Data.EntityFramework" Version="15.1.8" />
    <!-- Usage: DataLoader source generation -->
-    <PackageReference Include="HotChocolate.Types.Analyzers" Version="15.1.3" />
+    <PackageReference Include="HotChocolate.Types.Analyzers" Version="15.1.8" />
    <!-- Usage: GraphQL additional scalar type definitions -->
-    <PackageReference Include="HotChocolate.Types.Scalars" Version="15.1.3" />
+    <PackageReference Include="HotChocolate.Types.Scalars" Version="15.1.8" />
    <!-- Usage: git interop -->
    <PackageReference Include="LibGit2Sharp" Version="0.31.0" />
    <!-- Usage: OpenID Connect support -->
-    <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="8.0.15" />
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.OpenIdConnect" Version="8.0.18" />
    <!-- Usage: Support ""legacy"" Newotonsoft.Json in HTTP pipeline. The rest of our codebase uses Newtonsoft. -->
-    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="8.0.15" />
+    <PackageReference Include="Microsoft.AspNetCore.Mvc.NewtonsoftJson" Version="8.0.18" />
    <!-- Usage: Using target JSON serializer for API -->
-    <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.4" />
+    <PackageReference Include="Microsoft.AspNetCore.SignalR.Protocols.NewtonsoftJson" Version="9.0.7" />
    <!-- Usage: Generating dumps of dotnet engine processes -->
    <PackageReference Include="Microsoft.Diagnostics.NETCore.Client" Version="0.2.621003" />
    <!-- Usage: Database ORM -->
-    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore" Version="9.0.7" />
    <!-- Usage: Automatic migration generation using command line -->
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.4">
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Design" Version="9.0.7">
      <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
    </PackageReference>
    <!-- Usage: Sqlite ORM plugin -->
-    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="9.0.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.Sqlite" Version="9.0.7" />
    <!-- Usage: MSSQL ORM plugin -->
-    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="9.0.7" />
    <!-- Usage: Database connectivity health check -->
-    <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" Version="8.0.15" />
+    <PackageReference Include="Microsoft.Extensions.Diagnostics.HealthChecks.EntityFrameworkCore" Version="8.0.18" />
    <!-- Usage: OIDC support prerequisite. See https://stackoverflow.com/a/78650835/3976486 -->
-    <PackageReference Include="Microsoft.IdentityModel.Protocols.OpenIdConnect" Version="8.8.0" />
+    <PackageReference Include="Microsoft.IdentityModel.Protocols.OpenIdConnect" Version="8.13.0" />
    <!-- Usage: POSIX support for syscalls, signals, and symlinks -->
    <PackageReference Include="Mono.Posix.NETStandard" Version="1.0.0" />
    <!-- Usage: Cron string parsing -->
@@ -144,9 +144,9 @@
    <!-- Usage: Publishing Prometheus metrics -->
    <PackageReference Include="prometheus-net.AspNetCore.HealthChecks" Version="8.2.1" />
    <!-- Usage: Discord interop -->
-    <PackageReference Include="Remora.Discord" Version="2025.1.0" />
+    <PackageReference Include="Remora.Discord" Version="2025.2.0" />
    <!-- Usage: Rich logger builder -->
-    <PackageReference Include="Serilog.Extensions.Logging" Version="9.0.1" />
+    <PackageReference Include="Serilog.Extensions.Logging" Version="9.0.2" />
    <!-- Usage: Async logging plugin -->
    <PackageReference Include="Serilog.Sinks.Async" Version="2.1.0" />
    <!-- Usage: Console logging plugin -->
@@ -154,15 +154,17 @@
    <!-- Usage: Elasticsearch logging plugin -->
    <PackageReference Include="Serilog.Sinks.Elasticsearch" Version="10.0.0" />
    <!-- Usage: File logging plugin -->
-    <PackageReference Include="Serilog.Sinks.File" Version="6.0.0" />
+    <PackageReference Include="Serilog.Sinks.File" Version="7.0.0" />
    <!-- Usage: OpenAPI spec generator -->
-    <PackageReference Include="Swashbuckle.AspNetCore" Version="8.1.1" />
+    <PackageReference Include="Swashbuckle.AspNetCore" Version="9.0.3" />
    <!-- Usage: Newtonsoft.Json plugin for OpenAPI spec generator -->
-    <PackageReference Include="Swashbuckle.AspNetCore.Newtonsoft" Version="8.1.1" />
+    <PackageReference Include="Swashbuckle.AspNetCore.Newtonsoft" Version="9.0.3" />
    <!-- Usage: Windows authentication plugin allowing searching for users by name -->
-    <PackageReference Include="System.DirectoryServices.AccountManagement" Version="9.0.4" />
+    <PackageReference Include="System.DirectoryServices.AccountManagement" Version="9.0.7" />
+    <!-- Usage: Filesystem abstraction -->
+    <PackageReference Include="System.IO.Abstractions" Version="22.0.15" />
    <!-- Usage: Identifying owning user of Windows Process objects -->
-    <PackageReference Include="System.Management" Version="9.0.4" />
+    <PackageReference Include="System.Management" Version="9.0.7" />
  </ItemGroup>

  <ItemGroup>
@@ -212,7 +212,7 @@ namespace Tgstation.Server.Host.Transfer
 				if (downloadProvider.StreamProvider != null)
 					stream = await downloadProvider.StreamProvider(cancellationToken);
 				else
-					stream = ioManager.GetFileStream(downloadProvider.FilePath, downloadProvider.ShareWrite);
+					stream = ioManager.CreateAsyncReadStream(downloadProvider.FilePath, false, downloadProvider.ShareWrite);
 			}
 			catch (IOException ex)
 			{
@@ -17,6 +17,7 @@ General:
  HostApiDocumentation: false # Make HTTP API documentation available at /api/doc/tgs_api.json and /api/graphql
  SkipAddingByondFirewallException: false # Windows Only: Prevent running netsh.exe to add a firewall exception for installed engine binaries
  DeploymentDirectoryCopyTasksPerCore: 100 # Maximum number of concurrent file copy operations PER available CPU core
+  ByondZipDownloadTemplate: https://www.byond.com/download/build/${Major}/${Major}.${Minor}_byond${Linux:_linux}.zip # Template for downloading official byond versions
  OpenDreamGitUrl: https://github.com/OpenDreamProject/OpenDream # The repository to retrieve OpenDream from
  OpenDreamGitTagPrefix: v # The prefix to the OpenDream semver as tags appear in the git repository
  OpenDreamSuppressInstallOutput: false # Suppress the dotnet output of creating an OpenDream installation. Known to cause hangs in CI.
@@ -10,7 +10,7 @@

  <ItemGroup>
    <!-- Usage: JWT injection into HTTP pipeline -->
-    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="8.0.15" />
+    <PackageReference Include="Microsoft.AspNetCore.Authentication.JwtBearer" Version="8.0.18" />
    <!-- Usage: GitHub.com interop -->
    <PackageReference Include="Octokit" Version="14.0.0" />
    <!-- Usage: YAML conversion of Version objects -->
@@ -6,7 +6,7 @@
  </PropertyGroup>

  <ItemGroup>
-    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.4" />
+    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.7" />
  </ItemGroup>

  <ItemGroup>
@@ -0,0 +1,23 @@
+using System;
+
+using Microsoft.VisualStudio.TestTools.UnitTesting;
+
+namespace Tgstation.Server.Host.Components.Engine.Tests
+{
+	[TestClass]
+	public sealed class TestByondInstallerBase
+	{
+		[TestMethod]
+		public void TestUrlTemplateFormatting()
+		{
+			const string OSMarker = "TempleOS";
+
+			Assert.AreEqual(
+				new Uri("https://example.com/$515.1111_Hello Worl$d.zip"),
+				ByondInstallerBase.GetDownloadZipUrl(
+					new Version(515, 1111),
+					"https://example.com/$$${Major}.${Minor}_${TempleOS:Hello Worl$$d}.zip${Linux:Not this}${Or This}",
+					OSMarker));
+		}
+	}
+}
@@ -1,4 +1,5 @@
 using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using System;
@@ -9,6 +10,7 @@ using System.Threading.Tasks;

 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Internal;
+using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.IO;

 namespace Tgstation.Server.Host.Components.Engine.Tests
@@ -19,16 +21,18 @@ namespace Tgstation.Server.Host.Components.Engine.Tests
 		[TestMethod]
 		public void TestConstruction()
 		{
-			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(null, null, null, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(null, null, null, null, null));
 			var mockPostWriteHandler = new Mock<IPostWriteHandler>();
-			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, null, null, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, null, null, null, null));
 			var mockIOManager = new Mock<IIOManager>();
-			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, null, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, null, null, null));
 			var mockFileDownloader = Mock.Of<IFileDownloader>();
-			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, null, null));
+			var mockOptions = Mock.Of<IOptionsMonitor<GeneralConfiguration>>();
+			Assert.ThrowsException<ArgumentNullException>(() => new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockOptions, null));

 			var mockLogger = new Mock<ILogger<PosixByondInstaller>>();
-			_ = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockLogger.Object);
+			_ = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockOptions, mockLogger.Object);
 		}

 		[TestMethod]
@@ -38,7 +42,8 @@ namespace Tgstation.Server.Host.Components.Engine.Tests
 			var mockIOManager = new Mock<IIOManager>();
 			var mockLogger = new Mock<ILogger<PosixByondInstaller>>();
 			var mockFileDownloader = Mock.Of<IFileDownloader>();
-			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockLogger.Object);
+			var mockOptions = Mock.Of<IOptionsMonitor<GeneralConfiguration>>();
+			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockOptions, mockLogger.Object);
 			await installer.CleanCache(default);
 		}

@@ -50,7 +55,14 @@ namespace Tgstation.Server.Host.Components.Engine.Tests
 			var mockPostWriteHandler = new Mock<IPostWriteHandler>();
 			var mockLogger = new Mock<ILogger<PosixByondInstaller>>();
 			var mockFileDownloader = new Mock<IFileDownloader>();
-			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader.Object, mockLogger.Object);
+			var mockOptions = new Mock<IOptionsMonitor<GeneralConfiguration>>();
+			const string TestUrl = "https://chumb.is";
+			mockOptions.SetupGet(x => x.CurrentValue).Returns(new GeneralConfiguration
+			{
+				ByondZipDownloadTemplate = TestUrl,
+			});
+
+			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader.Object, mockOptions.Object, mockLogger.Object);

 			await Assert.ThrowsExceptionAsync<ArgumentNullException>(() => installer.DownloadVersion(null, null, default).AsTask());

@@ -58,7 +70,7 @@ namespace Tgstation.Server.Host.Components.Engine.Tests
 			mockFileDownloader
 				.Setup(
 					x => x.DownloadFile(
-						It.Is<Uri>(uri => uri == new Uri("https://www.byond.com/download/build/511/511.1385_byond_linux.zip")),
+						It.Is<Uri>(uri => uri == new Uri(TestUrl)),
 						null))
 				.Returns(
 					new BufferedFileStreamProvider(
@@ -87,7 +99,8 @@ namespace Tgstation.Server.Host.Components.Engine.Tests
 			var mockPostWriteHandler = new Mock<IPostWriteHandler>();
 			var mockLogger = new Mock<ILogger<PosixByondInstaller>>();
 			var mockFileDownloader = Mock.Of<IFileDownloader>();
-			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockLogger.Object);
+			var mockOptions = Mock.Of<IOptionsMonitor<GeneralConfiguration>>();
+			var installer = new PosixByondInstaller(mockPostWriteHandler.Object, mockIOManager.Object, mockFileDownloader, mockOptions, mockLogger.Object);

 			const string FakePath = "fake";
 			await Assert.ThrowsExceptionAsync<ArgumentNullException>(() => installer.Install(null, null, false, default).AsTask());
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions.TestingHelpers;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -31,9 +32,10 @@ namespace Tgstation.Server.Host.Components.StaticFiles.Tests
 				builder.SetMinimumLevel(LogLevel.Trace);
 			});

+			var mockFs = new MockFileSystem();
 			var tempPath = Path.GetTempFileName();
 			File.Delete(tempPath);
-			var ioManager = new ResolvingIOManager(new DefaultIOManager(), tempPath);
+			var ioManager = new DefaultIOManager(mockFs).CreateResolverForSubdirectory(tempPath);
 			await ioManager.CreateDirectory(".", CancellationToken.None);
 			try
 			{
@@ -46,7 +48,9 @@ namespace Tgstation.Server.Host.Components.StaticFiles.Tests

 				var configuration = new Configuration(
 					ioManager,
-					new SynchronousIOManager(loggerFactory.CreateLogger<SynchronousIOManager>()),
+					new SynchronousIOManager(
+						mockFs,
+						loggerFactory.CreateLogger<SynchronousIOManager>()),
 					Mock.Of<IFilesystemLinkFactory>(),
 					Mock.Of<IProcessExecutor>(),
 					Mock.Of<IPostWriteHandler>(),
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Runtime.InteropServices;
 using System.Security.Principal;
 using System.Threading;
@@ -17,10 +18,11 @@ namespace Tgstation.Server.Host.IO.Tests
 		[ClassInitialize]
 		public static void SelectFactory(TestContext _)
 		{
+			var fileSystem = new FileSystem();
 			if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
-				linkFactory = new WindowsFilesystemLinkFactory();
+				linkFactory = new WindowsFilesystemLinkFactory(fileSystem);
 			else
-				linkFactory = new PosixFilesystemLinkFactory();
+				linkFactory = new PosixFilesystemLinkFactory(fileSystem);
 		}

 		public static bool HasPermissionToMakeSymlinks()
@@ -1,5 +1,7 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
+using System.IO.Abstractions.TestingHelpers;
 using System.Linq;
 using System.Text;
 using System.Threading;
@@ -14,27 +16,34 @@ namespace Tgstation.Server.Host.IO.Tests
 	[TestClass]
 	public sealed class TestIOManager
 	{
-		readonly IIOManager ioManager = new DefaultIOManager();
+		readonly IFileSystem fileSystem;
+		readonly IIOManager ioManager;
+
+		public TestIOManager()
+		{
+			fileSystem = new MockFileSystem();
+			ioManager = new DefaultIOManager(fileSystem);
+		}

 		[TestMethod]
 		public async Task TestDeleteDirectory()
 		{
-			var tempPath = Path.GetTempFileName();
-			File.Delete(tempPath);
-			Directory.CreateDirectory(tempPath);
+			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+			fileSystem.File.Delete(tempPath);
+			fileSystem.Directory.CreateDirectory(tempPath);
 			try
 			{
-				await File.WriteAllTextAsync(Path.Combine(tempPath, "file.txt"), "asdf");
-				var subDir = Path.Combine(tempPath, "subdir");
-				Directory.CreateDirectory(subDir);
-				await File.WriteAllTextAsync(Path.Combine(subDir, "file2.txt"), "fdsa");
+				await fileSystem.File.WriteAllTextAsync(Path.Combine(tempPath, "file.txt"), "asdf");
+				var subDir = fileSystem.Path.Combine(tempPath, "subdir");
+				fileSystem.Directory.CreateDirectory(subDir);
+				await fileSystem.File.WriteAllTextAsync(Path.Combine(subDir, "file2.txt"), "fdsa");
 				await ioManager.DeleteDirectory(tempPath, default);

-				Assert.IsFalse(Directory.Exists(tempPath));
+				Assert.IsFalse(fileSystem.Directory.Exists(tempPath));
 			}
 			catch
 			{
-				Directory.Delete(tempPath, true);
+				fileSystem.Directory.Delete(tempPath, true);
 				throw;
 			}
 		}
@@ -42,13 +51,17 @@ namespace Tgstation.Server.Host.IO.Tests
 		[TestMethod]
 		public async Task TestDeleteDirectoryWithSymlinkInsideDoesntRecurse()
 		{
-			var linkFactory = (IFilesystemLinkFactory)(new PlatformIdentifier().IsWindows
-				? new WindowsFilesystemLinkFactory()
-				: new PosixFilesystemLinkFactory());
+			// need a real FS here
+			var fileSystem = new FileSystem();
+			var ioManager = new DefaultIOManager(fileSystem);

-			var tempPath = Path.GetTempFileName();
-			File.Delete(tempPath);
-			Directory.CreateDirectory(tempPath);
+			var linkFactory = (IFilesystemLinkFactory)(new PlatformIdentifier().IsWindows
+				? new WindowsFilesystemLinkFactory(fileSystem)
+				: new PosixFilesystemLinkFactory(fileSystem));
+
+			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+			fileSystem.File.Delete(tempPath);
+			fileSystem.Directory.CreateDirectory(tempPath);
 			try
 			{
 				var targetDir = ioManager.ConcatPath(tempPath, "targetdir");
@@ -81,7 +94,7 @@ namespace Tgstation.Server.Host.IO.Tests
 			}
 			catch
 			{
-				Directory.Delete(tempPath, true);
+				fileSystem.Directory.Delete(tempPath, true);
 				throw;
 			}
 		}
@@ -89,14 +102,15 @@ namespace Tgstation.Server.Host.IO.Tests
 		[TestMethod]
 		public async Task TestFileExists()
 		{
-			var tempPath = Path.GetTempFileName();
+			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+			await fileSystem.File.WriteAllBytesAsync(tempPath, Array.Empty<byte>());
 			try
 			{
 				Assert.IsTrue(await ioManager.FileExists(tempPath, default));
 			}
 			finally
 			{
-				File.Delete(tempPath);
+				fileSystem.File.Delete(tempPath);
 			}

 			Assert.IsFalse(await ioManager.FileExists(tempPath, default));
@@ -105,12 +119,12 @@ namespace Tgstation.Server.Host.IO.Tests
 		[TestMethod]
 		public async Task TestDirectoryExists()
 		{
-			var tempPath = Path.GetTempFileName();
-			File.Delete(tempPath);
+			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+			fileSystem.File.Delete(tempPath);

 			Assert.IsFalse(await ioManager.DirectoryExists(tempPath, default));

-			Directory.CreateDirectory(tempPath);
+			fileSystem.Directory.CreateDirectory(tempPath);

 			try
 			{
@@ -118,7 +132,7 @@ namespace Tgstation.Server.Host.IO.Tests
 			}
 			catch
 			{
-				Directory.Delete(tempPath);
+				fileSystem.Directory.Delete(tempPath);
 				throw;
 			}
 		}
@@ -180,18 +194,18 @@ namespace Tgstation.Server.Host.IO.Tests

 		async Task TestCopyDirectory(int? throttle)
 		{
-			var tempPath = Path.GetTempFileName();
-			File.Delete(tempPath);
-			Directory.CreateDirectory(tempPath);
+			var tempPath = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+			fileSystem.File.Delete(tempPath);
+			fileSystem.Directory.CreateDirectory(tempPath);
 			try
 			{
-				var tempPath2 = Path.GetTempFileName();
-				File.Delete(tempPath2);
+				var tempPath2 = fileSystem.Path.Combine(fileSystem.Path.GetTempPath(), fileSystem.Path.GetRandomFileName());
+				fileSystem.File.Delete(tempPath2);

-				await File.WriteAllTextAsync(Path.Combine(tempPath, "file.txt"), "asdf");
-				var subDir = Path.Combine(tempPath, "subdir");
-				Directory.CreateDirectory(subDir);
-				await File.WriteAllTextAsync(Path.Combine(subDir, "file2.txt"), "fdsa");
+				await fileSystem.File.WriteAllTextAsync(fileSystem.Path.Combine(tempPath, "file.txt"), "asdf");
+				var subDir = fileSystem.Path.Combine(tempPath, "subdir");
+				fileSystem.Directory.CreateDirectory(subDir);
+				await fileSystem.File.WriteAllTextAsync(fileSystem.Path.Combine(subDir, "file2.txt"), "fdsa");

 				try
 				{
@@ -203,26 +217,26 @@ namespace Tgstation.Server.Host.IO.Tests
 						throttle,
 						default);

-					Assert.IsTrue(Directory.Exists(tempPath2));
-					var newFilePath = Path.Combine(tempPath2, "file.txt");
-					Assert.IsTrue(File.Exists(newFilePath));
-					var newFileText = await File.ReadAllTextAsync(newFilePath);
+					Assert.IsTrue(fileSystem.Directory.Exists(tempPath2));
+					var newFilePath = fileSystem.Path.Combine(tempPath2, "file.txt");
+					Assert.IsTrue(fileSystem.File.Exists(newFilePath));
+					var newFileText = await fileSystem.File.ReadAllTextAsync(newFilePath);
 					Assert.AreEqual("asdf", newFileText);
-					var newDirPath = Path.Combine(tempPath2, "subdir");
-					Assert.IsTrue(Directory.Exists(newDirPath));
-					var newFile2Path = Path.Combine(newDirPath, "file2.txt");
-					Assert.IsTrue(File.Exists(newFile2Path));
-					var newFile2Text = await File.ReadAllTextAsync(newFile2Path);
+					var newDirPath = fileSystem.Path.Combine(tempPath2, "subdir");
+					Assert.IsTrue(fileSystem.Directory.Exists(newDirPath));
+					var newFile2Path = fileSystem.Path.Combine(newDirPath, "file2.txt");
+					Assert.IsTrue(fileSystem.File.Exists(newFile2Path));
+					var newFile2Text = await fileSystem.File.ReadAllTextAsync(newFile2Path);
 					Assert.AreEqual("fdsa", newFile2Text);
 				}
 				finally
 				{
-					Directory.Delete(tempPath2, true);
+					fileSystem.Directory.Delete(tempPath2, true);
 				}
 			}
 			finally
 			{
-				Directory.Delete(tempPath, true);
+				fileSystem.Directory.Delete(tempPath, true);
 			}
 		}
 	}
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Reflection;
 using System.Threading;
 using System.Threading.Tasks;
@@ -58,7 +59,8 @@ namespace Tgstation.Server.Host.System.Tests
 			processExecutor = new ProcessExecutor(
 				new PosixProcessFeatures(
 					new Lazy<IProcessExecutor>(() => processExecutor),
-					new DefaultIOManager(),
+					new DefaultIOManager(
+						new FileSystem()),
 					loggerFactory.CreateLogger<PosixProcessFeatures>()),
 				Mock.Of<IIOManager>(),
 				loggerFactory.CreateLogger<ProcessExecutor>(),
@@ -2,6 +2,7 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using System;
+using System.IO.Abstractions.TestingHelpers;
 using System.Runtime.InteropServices;

 using Tgstation.Server.Host.IO;
@@ -21,7 +22,7 @@ namespace Tgstation.Server.Host.System.Tests
 		{
 			features = RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
 				? (IProcessFeatures)new WindowsProcessFeatures(Mock.Of<ILogger<WindowsProcessFeatures>>())
-				: new PosixProcessFeatures(new Lazy<IProcessExecutor>(() => null), new DefaultIOManager(), Mock.Of<ILogger<PosixProcessFeatures>>());
+				: new PosixProcessFeatures(new Lazy<IProcessExecutor>(() => null), new DefaultIOManager(new MockFileSystem()), Mock.Of<ILogger<PosixProcessFeatures>>());
 		}

 		[TestMethod]
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -13,8 +14,10 @@ namespace Tgstation.Server.Host.System.Tests
 	public sealed class TestSymlinkFactory
 	{
 		readonly IFilesystemLinkFactory factory = new PlatformIdentifier().IsWindows
-			? new WindowsFilesystemLinkFactory()
-			: new PosixFilesystemLinkFactory();
+			? new WindowsFilesystemLinkFactory(
+				new FileSystem())
+			: new PosixFilesystemLinkFactory(
+				new FileSystem());

 		[TestMethod]
 		public async Task TestSymlinks()
@@ -2,6 +2,7 @@
 using Moq;
 using System;
 using System.IO;
+using System.IO.Abstractions.TestingHelpers;
 using System.Threading;
 using System.Threading.Tasks;

@@ -80,28 +81,29 @@ namespace Tgstation.Server.Host.Tests
 		public async Task TestStandardRunWithExceptionAndWatchdog()
 		{
 			var mockServer = new Mock<IServer>();
+			var mockFs = new MockFileSystem();
 			var exception = new DivideByZeroException();
 			mockServer.Setup(x => x.Run(It.IsAny<CancellationToken>())).Throws(exception);
 			mockServer.SetupGet(x => x.RestartRequested).Returns(true);
 			var mockServerFactory = new Mock<IServerFactory>();
-			mockServerFactory.SetupGet(x => x.IOManager).Returns(new DefaultIOManager());
+			mockServerFactory.SetupGet(x => x.IOManager).Returns(new DefaultIOManager(mockFs));
 			mockServerFactory.Setup(x => x.CreateServer(It.IsNotNull<string[]>(), It.IsAny<string>(), It.IsAny<CancellationToken>())).ReturnsAsync(mockServer.Object);
 			var program = new Program
 			{
 				ServerFactory = mockServerFactory.Object
 			};

-			var tempFileName = Path.GetTempFileName();
-			File.Delete(tempFileName);
+			var tempFileName = mockFs.Path.Combine(mockFs.Path.GetTempPath(), mockFs.Path.GetRandomFileName());
+			mockFs.File.Delete(tempFileName);
 			try
 			{
 				var result = await program.Main(Array.Empty<string>(), tempFileName);
 				Assert.AreEqual(HostExitCode.Error, result);
-				Assert.AreEqual(exception.ToString(), File.ReadAllText(tempFileName));
+				Assert.AreEqual(exception.ToString(), mockFs.File.ReadAllText(tempFileName));
 			}
 			finally
 			{
-				File.Delete(tempFileName);
+				mockFs.File.Delete(tempFileName);
 			}
 		}
 	}
@@ -1,6 +1,7 @@
 using Microsoft.VisualStudio.TestTools.UnitTesting;
 using Moq;
 using System;
+using System.IO.Abstractions.TestingHelpers;
 using System.Threading.Tasks;

 using Tgstation.Server.Host.Core;
@@ -20,11 +21,13 @@ namespace Tgstation.Server.Host.Tests
 		[TestMethod]
 		public void TestConstructor()
 		{
-			Assert.ThrowsException<ArgumentNullException>(() => new ServerFactory(null, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new ServerFactory(null, null, null));
 			IAssemblyInformationProvider assemblyInformationProvider = Mock.Of<IAssemblyInformationProvider>();
-			Assert.ThrowsException<ArgumentNullException>(() => new ServerFactory(assemblyInformationProvider, null));
+			Assert.ThrowsException<ArgumentNullException>(() => new ServerFactory(assemblyInformationProvider, null, null));
 			IIOManager ioManager = Mock.Of<IIOManager>();
-			_ = new ServerFactory(assemblyInformationProvider, ioManager);
+			Assert.ThrowsException<ArgumentNullException>(() => new ServerFactory(assemblyInformationProvider, ioManager, null));
+			var mockFileSystem = new MockFileSystem();
+			_ = new ServerFactory(assemblyInformationProvider, ioManager, mockFileSystem);
 		}

 		[TestMethod]
@@ -7,7 +7,9 @@

  <ItemGroup>
    <!-- Usage: Creating mock database implementations -->
-    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="9.0.4" />
+    <PackageReference Include="Microsoft.EntityFrameworkCore.InMemory" Version="9.0.7" />
+    <!-- Usage: Creating mock filesystem implementations -->
+    <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="22.0.15" />
  </ItemGroup>

  <ItemGroup>
@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -12,6 +13,8 @@ using Moq;
 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Api.Models.Internal;
 using Tgstation.Server.Common.Http;
+using Tgstation.Server.Host.Components.Engine;
+using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.Extensions;
 using Tgstation.Server.Host.IO;
 using Tgstation.Server.Host.System;
@@ -44,9 +47,9 @@ namespace Tgstation.Server.Tests
 			var logger = loggerFactory.CreateLogger("CachingFileDownloader");

 			var cfd = new CachingFileDownloader(loggerFactory.CreateLogger<CachingFileDownloader>());
-			var edgeVersion = await EngineTest.GetEdgeVersion(Api.Models.EngineType.Byond, cfd, cancellationToken);

-			await InitializeByondVersion(logger, edgeVersion.Version, new PlatformIdentifier().IsWindows, cancellationToken);
+			// this also will inject the edge version
+			var edgeVersion = await EngineTest.GetEdgeVersion(Api.Models.EngineType.Byond, logger, cfd, cancellationToken);

 			// predownload the target github release update asset
 			var gitHubToken = Environment.GetEnvironmentVariable("TGS_TEST_GITHUB_TOKEN");
@@ -78,7 +81,7 @@ namespace Tgstation.Server.Tests
 			ServiceCollectionExtensions.UseFileDownloader<CachingFileDownloader>();
 		}

-		public static async ValueTask InitializeByondVersion(ILogger logger, Version byondVersion, bool windows, CancellationToken cancellationToken)
+		public static async ValueTask InitializeByondVersion(ILogger logger, Version byondVersion, bool windows, CancellationToken cancellationToken, string urlCacheOverrideTemplate = null)
 		{
 			var version = new EngineVersion
 			{
@@ -86,25 +89,50 @@ namespace Tgstation.Server.Tests
 				Version = byondVersion,
 			};

-			var url = new Uri(
-				$"https://www.byond.com/download/build/{version.Version.Major}/{version.Version.Major}.{version.Version.Minor}_byond{(!windows ? "_linux" : string.Empty)}.zip");
-			string path = null;
-			if (TestingUtils.RunningInGitHubActions)
-			{
-				// actions is supposed to cache BYOND for us
+			var urlTemplate = TestingUtils.ByondZipDownloadTemplate;

-				var dir = Path.Combine(
+			var url = ByondInstallerBase.GetDownloadZipUrl(byondVersion, urlTemplate, new PlatformIdentifier().IsWindows ? "Windows" : "Linux");
+			string path = null;
+			string basePath = Environment.GetEnvironmentVariable("TGS_TEST_BYOND_ZIPS_BASE_PATH");
+			if (basePath == null && TestingUtils.RunningInGitHubActions)
+			{
+				// 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(
 					dir,
+					$"{version.Version.Major}.{version.Version.Minor}",
 					$"{version.Version.Major}.{version.Version.Minor}.zip");
 			}

-			await (await CacheFile(logger, url, null, path, cancellationToken)).DisposeAsync();
+			Uri overrideUrl = null;
+			if (urlCacheOverrideTemplate != null)
+			{
+				overrideUrl = url;
+				url = ByondInstallerBase.GetDownloadZipUrl(byondVersion, urlCacheOverrideTemplate, new PlatformIdentifier().IsWindows ? "Windows" : "Linux");
+			}
+
+			await (await CacheFile(
+				logger,
+				url,
+				null,
+				path,
+				cancellationToken))
+				.DisposeAsync();
+
+			if (overrideUrl != null)
+				cachedPaths[overrideUrl.ToString()] = cachedPaths[url.ToString()];
 		}

 		public static void Cleanup()
@@ -195,7 +223,7 @@ namespace Tgstation.Server.Tests
 						try
 						{
 							Directory.CreateDirectory(Path.GetDirectoryName(path));
-							await using var fs = new DefaultIOManager().CreateAsyncSequentialWriteStream(path);
+							await using var fs = new DefaultIOManager(new FileSystem()).CreateAsyncSequentialWriteStream(path);
 							await ms.CopyToAsync(fs, cancellationToken);

 							cachedPaths.Add(url.ToString(), Tuple.Create(path, temporal));
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Text;
 using System.Threading;
@@ -90,7 +91,8 @@ namespace Tgstation.Server.Tests.Live.Instance
 		public ValueTask SetupDMApiTests(bool includingRoot, CancellationToken cancellationToken)
 		{
 			// just use an I/O manager here
-			var ioManager = new DefaultIOManager();
+			var ioManager = new DefaultIOManager(
+				new FileSystem());

 			async ValueTask TestStaticFileAndDir()
 			{
@@ -127,7 +129,7 @@ namespace Tgstation.Server.Tests.Live.Instance
 						Path = $"/EventScripts/{scriptName}"
 					};

-					await using var readStream = ioManager.GetFileStream($"../../../../DMAPI/{(basic ? "BasicOperation" : "LongRunning")}/{scriptName}", false);
+					await using var readStream = ioManager.CreateAsyncReadStream($"../../../../DMAPI/{(basic ? "BasicOperation" : "LongRunning")}/{scriptName}", true, false);
 					await configurationClient.Write(
 						resourcingScript,
 						readStream,
@@ -41,13 +41,13 @@ namespace Tgstation.Server.Tests.Live.Instance
 		EngineVersion testVersion;
 		readonly EngineType testEngine = engineType;

-		public Task Run(CancellationToken cancellationToken, out Task firstInstall)
+		public Task Run(ILogger logger, CancellationToken cancellationToken, out Task firstInstall)
 		{
-			firstInstall = RunPartOne(cancellationToken);
+			firstInstall = RunPartOne(logger, cancellationToken);
 			return RunContinued(firstInstall, cancellationToken);
 		}

-		public static async ValueTask<EngineVersion> GetEdgeVersion(EngineType engineType, IFileDownloader fileDownloader, CancellationToken cancellationToken)
+		public static async ValueTask<EngineVersion> GetEdgeVersion(EngineType engineType, ILogger logger, IFileDownloader fileDownloader, CancellationToken cancellationToken)
 		{
 			var edgeVersion = edgeVersions[engineType];

@@ -57,26 +57,7 @@ namespace Tgstation.Server.Tests.Live.Instance
 			EngineVersion engineVersion;
 			if (engineType == EngineType.Byond)
 			{
-				await using var provider = fileDownloader.DownloadFile(new Uri("https://www.byond.com/download/version.txt"), null);
-				var stream = await provider.GetResult(cancellationToken);
-				using var reader = new StreamReader(stream, Encoding.UTF8, false, -1, true);
-				var text = await reader.ReadToEndAsync(cancellationToken);
-				var splits = text.Split('\n', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
-
-				var targetVersion = splits.Last();
-
-				var badVersionMap = new PlatformIdentifier().IsWindows
-					? []
-					// linux map also needs updating in CI
-					: new Dictionary<string, string>()
-					{
-						{ "515.1612", "515.1611" }
-					};
-
-				badVersionMap.Add("515.1617", "515.1616");
-
-				if (badVersionMap.TryGetValue(targetVersion, out var remappedVersion))
-					targetVersion = remappedVersion;
+				var targetVersion = await TestingUtils.GetByondEdgeVersion(logger, fileDownloader, cancellationToken);

 				Assert.IsTrue(EngineVersion.TryParse(targetVersion, out engineVersion), $"Bad version: {targetVersion}");
 			}
@@ -112,9 +93,9 @@ namespace Tgstation.Server.Tests.Live.Instance
 			return edgeVersions[engineType] = engineVersion;
 		}

-		async Task RunPartOne(CancellationToken cancellationToken)
+		async Task RunPartOne(ILogger logger, CancellationToken cancellationToken)
 		{
-			testVersion = await GetEdgeVersion(testEngine, fileDownloader, cancellationToken);
+			testVersion = await GetEdgeVersion(testEngine, logger, fileDownloader, cancellationToken);
 			await TestNoVersion(cancellationToken);
 			await TestInstallNullVersion(cancellationToken);
 			await TestInstallStable(cancellationToken);
@@ -284,8 +265,11 @@ namespace Tgstation.Server.Tests.Live.Instance

 		async Task TestCustomInstalls(CancellationToken cancellationToken)
 		{
-			var generalConfigOptionsMock = new Mock<IOptions<GeneralConfiguration>>();
-			generalConfigOptionsMock.SetupGet(x => x.Value).Returns(new GeneralConfiguration());
+			var generalConfigOptionsMock = new Mock<IOptionsMonitor<GeneralConfiguration>>();
+			generalConfigOptionsMock.SetupGet(x => x.CurrentValue).Returns(new GeneralConfiguration
+			{
+				ByondZipDownloadTemplate = TestingUtils.ByondZipDownloadTemplate,
+			});
 			var sessionConfigOptionsMock = new Mock<IOptions<SessionConfiguration>>();
 			sessionConfigOptionsMock.SetupGet(x => x.Value).Returns(new SessionConfiguration());

@@ -303,6 +287,7 @@ namespace Tgstation.Server.Tests.Live.Instance
 					Mock.Of<IPostWriteHandler>(),
 					Mock.Of<IIOManager>(),
 					fileDownloader,
+					generalConfigOptionsMock.Object,
 					Mock.Of<ILogger<PosixByondInstaller>>());

 			using var windowsByondInstaller = byondInstaller as WindowsByondInstaller;
@@ -1,5 +1,6 @@
 using System;
 using System.Collections.Generic;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -36,6 +37,7 @@ namespace Tgstation.Server.Tests.Live.Instance
 		readonly ushort serverPort = serverPort;

 		public async Task RunTests(
+			ILogger logger,
 			IInstanceClient instanceClient,
 			ushort dmPort,
 			ushort ddPort,
@@ -44,14 +46,14 @@ namespace Tgstation.Server.Tests.Live.Instance
 			bool usingBasicWatchdog,
 			CancellationToken cancellationToken)
 		{
-			var testVersion = await EngineTest.GetEdgeVersion(EngineType.Byond, fileDownloader, cancellationToken);
+			var testVersion = await EngineTest.GetEdgeVersion(EngineType.Byond, logger, fileDownloader, cancellationToken);
 			await using var engineTest = new EngineTest(instanceClient.Engine, instanceClient.Jobs, fileDownloader, instanceClient.Metadata, testVersion.Engine.Value);
 			await using var chatTest = new ChatTest(instanceClient.ChatBots, instanceManagerClient, instanceClient.Jobs, instanceClient.Metadata);
 			var configTest = new ConfigurationTest(instanceClient.Configuration, instanceClient.Metadata);
 			await using var repoTest = new RepositoryTest(instanceClient, instanceClient.Repository, instanceClient.Jobs);
 			await using var dmTest = new DeploymentTest(instanceClient, instanceClient.Jobs, dmPort, ddPort, lowPrioDeployment, testVersion);

-			var byondTask = engineTest.Run(cancellationToken, out var firstInstall);
+			var byondTask = engineTest.Run(logger, cancellationToken, out var firstInstall);
 			var chatTask = chatTest.RunPreWatchdog(cancellationToken);

 			var repoLongJob = await repoTest.RunLongClone(cancellationToken);
@@ -89,25 +91,26 @@ namespace Tgstation.Server.Tests.Live.Instance
 			Uri openDreamUrl,
 			CancellationToken cancellationToken)
 		{
-			var ioManager = new DefaultIOManager();
+			var ioManager = new DefaultIOManager(new FileSystem());
 			var odRepoDir = ioManager.ConcatPath(
 				Environment.GetFolderPath(
 					Environment.SpecialFolder.LocalApplicationData,
 					Environment.SpecialFolderOption.DoNotVerify),
 				new AssemblyInformationProvider().VersionPrefix,
 				"OpenDreamRepository");
-			var odRepoIoManager = new ResolvingIOManager(ioManager, odRepoDir);
+			var odRepoIoManager = ioManager.CreateResolverForSubdirectory(odRepoDir);

-			var mockOptions = new Mock<IOptions<GeneralConfiguration>>();
+			var mockOptionsMonitor = new Mock<IOptionsMonitor<GeneralConfiguration>>();
 			var genConfig = new GeneralConfiguration
 			{
 				OpenDreamGitUrl = openDreamUrl,
+				ByondZipDownloadTemplate = TestingUtils.ByondZipDownloadTemplate,
 			};
-			mockOptions.SetupGet(x => x.Value).Returns(genConfig);
+			mockOptionsMonitor.SetupGet(x => x.CurrentValue).Returns(genConfig);
 			IEngineInstaller byondInstaller =
 				compatVersion.Engine == EngineType.OpenDream
 				? new OpenDreamInstaller(
-					new DefaultIOManager(),
+					ioManager,
 					Mock.Of<ILogger<OpenDreamInstaller>>(),
 					new PlatformIdentifier(),
 					Mock.Of<IProcessExecutor>(),
@@ -124,20 +127,21 @@ namespace Tgstation.Server.Tests.Live.Instance
 						genConfig),
 					Mock.Of<IAsyncDelayer>(),
 					Mock.Of<IAbstractHttpClientFactory>(),
-					mockOptions.Object,
+					Options.Create(genConfig),
 					Options.Create(new SessionConfiguration()))
 				: new PlatformIdentifier().IsWindows
 					? new WindowsByondInstaller(
 						Mock.Of<IProcessExecutor>(),
 						Mock.Of<IIOManager>(),
 						fileDownloader,
-						Options.Create(genConfig),
+						mockOptionsMonitor.Object,
 						Options.Create(new SessionConfiguration()),
 						Mock.Of<ILogger<WindowsByondInstaller>>())
 					: new PosixByondInstaller(
 						Mock.Of<IPostWriteHandler>(),
 						Mock.Of<IIOManager>(),
 						fileDownloader,
+						mockOptionsMonitor.Object,
 						Mock.Of<ILogger<PosixByondInstaller>>());

 			using var windowsByondInstaller = byondInstaller as WindowsByondInstaller;
@@ -14,6 +14,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Net;
 using System.Net.Sockets;
@@ -809,7 +810,7 @@ namespace Tgstation.Server.Tests.Live.Instance

 			var features = new PosixProcessFeatures(
 				new Lazy<IProcessExecutor>(Mock.Of<IProcessExecutor>()),
-				new DefaultIOManager(),
+				new DefaultIOManager(new FileSystem()),
 				Mock.Of<ILogger<PosixProcessFeatures>>());

 			features.SuspendProcess(proc);
@@ -876,7 +877,7 @@ namespace Tgstation.Server.Tests.Live.Instance
 			executor = new ProcessExecutor(
 				RuntimeInformation.IsOSPlatform(OSPlatform.Windows)
 					? new WindowsProcessFeatures(Mock.Of<ILogger<WindowsProcessFeatures>>())
-					: new PosixProcessFeatures(new Lazy<IProcessExecutor>(() => executor), new DefaultIOManager(), Mock.Of<ILogger<PosixProcessFeatures>>()),
+					: new PosixProcessFeatures(new Lazy<IProcessExecutor>(() => executor), new DefaultIOManager(new FileSystem()), Mock.Of<ILogger<PosixProcessFeatures>>()),
 				Mock.Of<IIOManager>(),
 				Mock.Of<ILogger<ProcessExecutor>>(),
 				LoggerFactory.Create(x => { }));
@@ -6,6 +6,7 @@ using System;
 using System.Collections.Generic;
 using System.Globalization;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -43,7 +44,7 @@ namespace Tgstation.Server.Tests.Live
 			for (int i = 0; i < 5; ++i)
 				try
 				{
-					new DefaultIOManager().DeleteDirectory(directory, default).GetAwaiter().GetResult();
+					new DefaultIOManager(new FileSystem()).DeleteDirectory(directory, default).GetAwaiter().GetResult();
 				}
 				catch
 				{
@@ -156,7 +157,8 @@ namespace Tgstation.Server.Tests.Live
 				$"Security:TokenExpiryMinutes=120", // timeouts are useless for us
 				$"General:OpenDreamSuppressInstallOutput={TestingUtils.RunningInGitHubActions}",
 				"Telemetry:DisableVersionReporting=true",
-				$"General:PrometheusPort={port}"
+				$"General:PrometheusPort={port}",
+				$"General:ByondZipDownloadTemplate={TestingUtils.ByondZipDownloadTemplate}"
 			};

 			if (MultiServerClient.UseGraphQL)
@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.Diagnostics;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Management;
 using System.Net;
@@ -415,7 +416,7 @@ namespace Tgstation.Server.Tests.Live
 				var gitHubToken = Environment.GetEnvironmentVariable("TGS_TEST_GITHUB_TOKEN");
 				if (String.IsNullOrWhiteSpace(gitHubToken))
 					gitHubToken = null;
-				await new Host.IO.DefaultIOManager().DeleteDirectory(server.UpdatePath, cancellationToken);
+				await new Host.IO.DefaultIOManager(new FileSystem()).DeleteDirectory(server.UpdatePath, cancellationToken);
 				serverTask = server.Run(cancellationToken).AsTask();

 				await using (var adminClient = await CreateAdminClient(server.ApiUrl, cancellationToken))
@@ -1135,7 +1136,7 @@ namespace Tgstation.Server.Tests.Live
 					ApiValidationSecurityLevel = DreamDaemonSecurity.Trusted,
 				}, cancellationToken);

-				var ioManager = new Host.IO.DefaultIOManager();
+				var ioManager = new Host.IO.DefaultIOManager(new FileSystem());
 				var repoPath = ioManager.ConcatPath(instance.Path, "Repository");
 				await using var jobsTest = new JobsRequiredTest(instanceClient.Jobs);
 				var postWriteHandler = (Host.IO.IPostWriteHandler)(new PlatformIdentifier().IsWindows
@@ -1421,6 +1422,7 @@ namespace Tgstation.Server.Tests.Live
 				await Task.Yield();

 			InstanceManager GetInstanceManager() => ((Host.Server)server.RealServer).Host.Services.GetRequiredService<InstanceManager>();
+			ILogger GetLogger() => ((Host.Server)server.RealServer).Host.Services.GetRequiredService<ILogger<TestLiveServer>>();

 			// main run
 			var serverTask = server.Run(cancellationToken).AsTask();
@@ -1590,7 +1592,7 @@ namespace Tgstation.Server.Tests.Live
 						var testSerialized = TestingUtils.RunningInGitHubActions; // they only have 2 cores, can't handle intense parallelization
 						async Task ODCompatTests()
 						{
-							var edgeODVersionTask = EngineTest.GetEdgeVersion(EngineType.OpenDream, fileDownloader, cancellationToken);
+							var edgeODVersionTask = EngineTest.GetEdgeVersion(EngineType.OpenDream, GetLogger(), fileDownloader, cancellationToken);

 							var ex = await Assert.ThrowsExceptionAsync<JobException>(
 								() => InstanceTest.DownloadEngineVersion(
@@ -1625,6 +1627,16 @@ 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(
@@ -1632,8 +1644,8 @@ 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),
@@ -1649,6 +1661,7 @@ namespace Tgstation.Server.Tests.Live
 						await FailFast(
 							instanceTest
 								.RunTests(
+									GetLogger(),
 									instanceClient,
 									mainDMPort.Value,
 									mainDDPort.Value,
@@ -1881,7 +1894,7 @@ namespace Tgstation.Server.Tests.Live
 				preStartupTime = DateTimeOffset.UtcNow;
 				serverTask = server.Run(cancellationToken).AsTask();
 				long expectedCompileJobId, expectedStaged;
-				var edgeVersion = await EngineTest.GetEdgeVersion(EngineType.Byond, fileDownloader, cancellationToken);
+				var edgeVersion = await EngineTest.GetEdgeVersion(EngineType.Byond, GetLogger(), fileDownloader, cancellationToken);
 				await using (var adminClient = await CreateAdminClient(server.ApiUrl, cancellationToken))
 				{
 					var restAdminClient = adminClient.RestClient;
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Linq;
 using System.Threading;
 using System.Threading.Tasks;
@@ -58,7 +59,7 @@ namespace Tgstation.Server.Tests
 			}
 			finally
 			{
-				await new DefaultIOManager().DeleteDirectory(
+				await new DefaultIOManager(new FileSystem()).DeleteDirectory(
 					Path.GetDirectoryName(tempPath),
 					CancellationToken.None);
 			}
@@ -75,8 +76,7 @@ namespace Tgstation.Server.Tests
 			using var manager = new RepositoryManager(
 				repoFac,
 				commands,
-				new ResolvingIOManager(
-					new DefaultIOManager(),
+				new DefaultIOManager(new FileSystem()).CreateResolverForSubdirectory(
 					tempPath),
 				Mock.Of<IEventConsumer>(),
 				new WindowsPostWriteHandler(),
@@ -131,7 +131,7 @@ namespace Tgstation.Server.Tests
 			}
 			finally
 			{
-				await new DefaultIOManager().DeleteDirectory(
+				await new DefaultIOManager(new FileSystem()).DeleteDirectory(
 					Path.GetDirectoryName(tempPath),
 					CancellationToken.None);
 			}
@@ -1,5 +1,6 @@
 using System;
 using System.IO;
+using System.IO.Abstractions;
 using System.Threading;
 using System.Threading.Tasks;

@@ -24,7 +25,7 @@ namespace Tgstation.Server.Tests
 			var platformIdentifier = new PlatformIdentifier();
 			var processExecutor = new ProcessExecutor(
 				Mock.Of<IProcessFeatures>(),
-				new DefaultIOManager(),
+				new DefaultIOManager(new FileSystem()),
 				Mock.Of<ILogger<ProcessExecutor>>(),
 				loggerFactory);

@@ -52,7 +53,7 @@ namespace Tgstation.Server.Tests
 			var platformIdentifier = new PlatformIdentifier();
 			var processExecutor = new ProcessExecutor(
 				Mock.Of<IProcessFeatures>(),
-				new DefaultIOManager(),
+				new DefaultIOManager(new FileSystem()),
 				loggerFactory.CreateLogger<ProcessExecutor>(),
 				loggerFactory);

@@ -33,6 +33,7 @@ using Tgstation.Server.Host.System;
 using Tgstation.Server.Api.Models;
 using Tgstation.Server.Tests.Live;
 using Tgstation.Server.Host.Properties;
+using System.IO.Abstractions;

 namespace Tgstation.Server.Tests
 {
@@ -103,10 +104,14 @@ namespace Tgstation.Server.Tests
 		}

 		[TestMethod]
+		[TestCategory("RequiresDatabase")]
 		public async Task TestDDExeByondVersion()
 		{
-			var mockGeneralConfigurationOptions = new Mock<IOptions<GeneralConfiguration>>();
-			mockGeneralConfigurationOptions.SetupGet(x => x.Value).Returns(new GeneralConfiguration());
+			var mockGeneralConfigurationOptions = new Mock<IOptionsMonitor<GeneralConfiguration>>();
+			mockGeneralConfigurationOptions.SetupGet(x => x.CurrentValue).Returns(new GeneralConfiguration
+			{
+				ByondZipDownloadTemplate = TestingUtils.ByondZipDownloadTemplate,
+			});
 			var mockSessionConfigurationOptions = new Mock<IOptions<SessionConfiguration>>();
 			mockSessionConfigurationOptions.SetupGet(x => x.Value).Returns(new SessionConfiguration());

@@ -165,12 +170,14 @@ namespace Tgstation.Server.Tests
 		static Version MapThreadsVersion() => (Version)typeof(ByondInstallerBase).GetField("MapThreadsVersion", BindingFlags.Static | BindingFlags.NonPublic).GetValue(null) ?? throw new InvalidOperationException("Couldn't find MapThreadsVersion");

 		[TestMethod]
+		[TestCategory("RequiresDatabase")]
 		public async Task TestMapThreadsByondVersion()
 		{
-			var mockGeneralConfigurationOptions = new Mock<IOptions<GeneralConfiguration>>();
-			mockGeneralConfigurationOptions.SetupGet(x => x.Value).Returns(new GeneralConfiguration
+			var mockGeneralConfigurationOptions = new Mock<IOptionsMonitor<GeneralConfiguration>>();
+			mockGeneralConfigurationOptions.SetupGet(x => x.CurrentValue).Returns(new GeneralConfiguration
 			{
 				SkipAddingByondFirewallException = true,
+				ByondZipDownloadTemplate = TestingUtils.ByondZipDownloadTemplate,
 			});
 			var mockSessionConfigurationOptions = new Mock<IOptions<SessionConfiguration>>();
 			mockSessionConfigurationOptions.SetupGet(x => x.Value).Returns(new SessionConfiguration());
@@ -207,8 +214,9 @@ namespace Tgstation.Server.Tests
 					loggerFactory.CreateLogger<WindowsByondInstaller>())
 				: new PosixByondInstaller(
 					new PosixPostWriteHandler(loggerFactory.CreateLogger<PosixPostWriteHandler>()),
-					new DefaultIOManager(),
+					new DefaultIOManager(new FileSystem()),
 					fileDownloader,
+					mockGeneralConfigurationOptions.Object,
 					loggerFactory.CreateLogger<PosixByondInstaller>());
 			using var disposable = byondInstaller as IDisposable;

@@ -217,13 +225,13 @@ namespace Tgstation.Server.Tests
 					? new WindowsProcessFeatures(Mock.Of<ILogger<WindowsProcessFeatures>>())
 					: new PosixProcessFeatures(
 						new Lazy<IProcessExecutor>(() => null),
-						new DefaultIOManager(),
+						new DefaultIOManager(new FileSystem()),
 						loggerFactory.CreateLogger<PosixProcessFeatures>()),
 					Mock.Of<IIOManager>(),
 					loggerFactory.CreateLogger<ProcessExecutor>(),
 					loggerFactory);

-			var ioManager = new DefaultIOManager();
+			var ioManager = new DefaultIOManager(new FileSystem());
 			var tempPath = ioManager.ConcatPath(LiveTestingServer.BaseDirectory, "mapthreads");
 			await ioManager.CreateDirectory(tempPath, default);
 			try
@@ -1,16 +1,24 @@
 using System;
+using System.Collections.Generic;
 using System.IO;
+using System.IO.Abstractions;
 using System.IO.Compression;
+using System.Linq;
+using System.Net.Http;
 using System.Reflection;
+using System.Text;
 using System.Threading;
 using System.Threading.Tasks;

 using Microsoft.Extensions.Logging;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+
 using Moq;

 using Tgstation.Server.Host.Components.Engine;
+using Tgstation.Server.Host.Configuration;
 using Tgstation.Server.Host.IO;
+using Tgstation.Server.Host.System;

 namespace Tgstation.Server.Tests
 {
@@ -67,8 +75,91 @@ namespace Tgstation.Server.Tests
 			}
 			finally
 			{
-				await new DefaultIOManager().DeleteDirectory(tempFolder, cancellationToken);
+				await new DefaultIOManager(new FileSystem()).DeleteDirectory(tempFolder, cancellationToken);
 			}
 		}
+
+		static string byondZipDownloadTemplate;
+
+		public static string ByondZipDownloadTemplate
+		{
+			get
+			{
+				if (byondZipDownloadTemplate == null)
+				{
+					var envvar = Environment.GetEnvironmentVariable("TGS_TEST_BYOND_ZIP_DOWNLOAD_TEMPLATE");
+					if (envvar != null)
+						byondZipDownloadTemplate = envvar;
+					else
+						byondZipDownloadTemplate = GeneralConfiguration.DefaultByondZipDownloadTemplate;
+				}
+
+				return byondZipDownloadTemplate;
+			}
+		}
+
+		static string edgeVersion = null;
+		public static async ValueTask<string> GetByondEdgeVersion(ILogger logger, IFileDownloader fileDownloader, CancellationToken cancellationToken)
+		{
+			if (edgeVersion != null)
+				return edgeVersion;
+
+			async ValueTask<string> GetVersionFromResponse(string versionTxt)
+			{
+				await using var provider = fileDownloader.DownloadFile(new Uri(versionTxt), null);
+				var stream = await provider.GetResult(cancellationToken);
+				using var reader = new StreamReader(stream, Encoding.UTF8, false, -1, true);
+				var text = await reader.ReadToEndAsync(cancellationToken);
+				var splits = text.Split('\n', StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries);
+
+				var targetVersion = splits.Last();
+
+				var badVersionMap = new PlatformIdentifier().IsWindows
+					? []
+					// linux map also needs updating in CI
+					: new Dictionary<string, string>()
+					{
+						{ "515.1612", "515.1611" }
+					};
+
+				badVersionMap.Add("515.1617", "515.1616");
+
+				if (badVersionMap.TryGetValue(targetVersion, out var remappedVersion))
+					targetVersion = remappedVersion;
+
+				return targetVersion;
+			}
+
+			var mirroredVersionTxt = Environment.GetEnvironmentVariable("TGS_TEST_BYOND_MIRROR_VERSION_TXT");
+			try
+			{
+				// always check byond.com first for latest up-to-date, mirror should ALWAYS have stable versions
+				// except byond hates all CI runners now
+				const string DefaultMirror = "https://spacestation13.github.io/byond-builds/version.txt";
+				edgeVersion = await GetVersionFromResponse(DefaultMirror);
+
+				logger.LogInformation("Downloading edge version from SS13 mirror {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,
+					"https://spacestation13.github.io/byond-builds/${Major}/${Major}.${Minor}_byond${Linux:_linux}.zip");
+			}
+			catch (Exception ex)
+			{
+				logger.LogWarning(ex, "Cannot download zip from byond.com!");
+				if (ByondZipDownloadTemplate == GeneralConfiguration.DefaultByondZipDownloadTemplate || mirroredVersionTxt == null)
+					throw;
+
+				// fall back to the mirrored version.txt
+				await using var provider = fileDownloader.DownloadFile(new Uri(mirroredVersionTxt), null);
+				edgeVersion = await GetVersionFromResponse(mirroredVersionTxt);
+			}
+
+			return edgeVersion;
+		}
 	}
 }
@@ -5,10 +5,6 @@
    <TargetFramework>$(TgsFrameworkVersion)</TargetFramework>
  </PropertyGroup>

-  <ItemGroup>
-    <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.4" />
-  </ItemGroup>
-
  <ItemGroup>
    <ProjectReference Include="..\..\src\Tgstation.Server.Client.GraphQL\Tgstation.Server.Client.GraphQL.csproj" />
    <ProjectReference Include="..\..\src\Tgstation.Server.Host.Watchdog\Tgstation.Server.Host.Watchdog.csproj" />