diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index ad67596360..580a76f598 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -4,6 +4,7 @@ on:
   push:
     branches:
       - master
+      - llvm18
 concurrency:
   # Cancels pending runs when a PR gets updated.
   group: ${{ github.head_ref || github.run_id }}-${{ github.actor }}
diff --git a/ci/aarch64-linux-debug.sh b/ci/aarch64-linux-debug.sh
index b75911fa56..ef653bd40c 100644
--- a/ci/aarch64-linux-debug.sh
+++ b/ci/aarch64-linux-debug.sh
@@ -8,7 +8,7 @@ set -e
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.203+d3bc1cfc4"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/aarch64-linux-release.sh b/ci/aarch64-linux-release.sh
index a43f162eb5..194081d476 100644
--- a/ci/aarch64-linux-release.sh
+++ b/ci/aarch64-linux-release.sh
@@ -8,7 +8,7 @@ set -e
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.203+d3bc1cfc4"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/aarch64-macos-debug.sh b/ci/aarch64-macos-debug.sh
index fb85914c49..3a8c1938d3 100755
--- a/ci/aarch64-macos-debug.sh
+++ b/ci/aarch64-macos-debug.sh
@@ -9,7 +9,7 @@ set -e
 ZIGDIR="$PWD"
 TARGET="$ARCH-macos-none"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.467+0345d7866"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/aarch64-macos-release.sh b/ci/aarch64-macos-release.sh
index e34c3e31da..3d35b49bd7 100755
--- a/ci/aarch64-macos-release.sh
+++ b/ci/aarch64-macos-release.sh
@@ -9,7 +9,7 @@ set -e
 ZIGDIR="$PWD"
 TARGET="$ARCH-macos-none"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.467+0345d7866"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/aarch64-windows.ps1 b/ci/aarch64-windows.ps1
index 72da7c3a89..67d3d176c9 100644
--- a/ci/aarch64-windows.ps1
+++ b/ci/aarch64-windows.ps1
@@ -1,5 +1,5 @@
 $TARGET = "$($Env:ARCH)-windows-gnu"
-$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.12.0-dev.2087+e9a18010b"
+$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 $MCPU = "baseline"
 $ZIG_LLVM_CLANG_LLD_URL = "https://ziglang.org/deps/$ZIG_LLVM_CLANG_LLD_NAME.zip"
 $PREFIX_PATH = "$(Get-Location)\..\$ZIG_LLVM_CLANG_LLD_NAME"
diff --git a/ci/x86_64-linux-debug.sh b/ci/x86_64-linux-debug.sh
index 38b98cc4a9..45b81f753f 100755
--- a/ci/x86_64-linux-debug.sh
+++ b/ci/x86_64-linux-debug.sh
@@ -8,7 +8,7 @@ set -e
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.203+d3bc1cfc4"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/x86_64-linux-release.sh b/ci/x86_64-linux-release.sh
index 3860cd734f..1909fd049b 100755
--- a/ci/x86_64-linux-release.sh
+++ b/ci/x86_64-linux-release.sh
@@ -8,7 +8,7 @@ set -e
 ARCH="$(uname -m)"
 TARGET="$ARCH-linux-musl"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.203+d3bc1cfc4"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/deps/$CACHE_BASENAME"
 ZIG="$PREFIX/bin/zig"
 
diff --git a/ci/x86_64-macos-release.sh b/ci/x86_64-macos-release.sh
index c67613d3fc..3dfbfd3cc0 100755
--- a/ci/x86_64-macos-release.sh
+++ b/ci/x86_64-macos-release.sh
@@ -6,7 +6,7 @@ set -e
 ZIGDIR="$PWD"
 TARGET="$ARCH-macos-none"
 MCPU="baseline"
-CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.12.0-dev.467+0345d7866"
+CACHE_BASENAME="zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 PREFIX="$HOME/$CACHE_BASENAME"
 JOBS="-j3"
 
diff --git a/ci/x86_64-windows-debug.ps1 b/ci/x86_64-windows-debug.ps1
index 6f8039883d..717bdb1b36 100644
--- a/ci/x86_64-windows-debug.ps1
+++ b/ci/x86_64-windows-debug.ps1
@@ -1,10 +1,20 @@
 $TARGET = "$($Env:ARCH)-windows-gnu"
-$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.12.0-dev.2073+402fe565a"
+$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 $MCPU = "baseline"
-$PREFIX_PATH = "$($Env:USERPROFILE)\$ZIG_LLVM_CLANG_LLD_NAME"
+$ZIG_LLVM_CLANG_LLD_URL = "https://ziglang.org/deps/$ZIG_LLVM_CLANG_LLD_NAME.zip"
+$PREFIX_PATH = "$(Get-Location)\..\$ZIG_LLVM_CLANG_LLD_NAME"
 $ZIG = "$PREFIX_PATH\bin\zig.exe"
 $ZIG_LIB_DIR = "$(Get-Location)\lib"
 
+if (!(Test-Path "..\$ZIG_LLVM_CLANG_LLD_NAME.zip")) {
+    Write-Output "Downloading $ZIG_LLVM_CLANG_LLD_URL"
+    Invoke-WebRequest -Uri "$ZIG_LLVM_CLANG_LLD_URL" -OutFile "..\$ZIG_LLVM_CLANG_LLD_NAME.zip"
+
+    Write-Output "Extracting..."
+    Add-Type -AssemblyName System.IO.Compression.FileSystem ;
+    [System.IO.Compression.ZipFile]::ExtractToDirectory("$PWD\..\$ZIG_LLVM_CLANG_LLD_NAME.zip", "$PWD\..")
+}
+
 function CheckLastExitCode {
     if (!$?) {
         exit 1
@@ -25,6 +35,12 @@ Remove-Item -Path 'build-debug' -Recurse -Force -ErrorAction Ignore
 New-Item -Path 'build-debug' -ItemType Directory
 Set-Location -Path 'build-debug'
 
+# Override the cache directories because they won't actually help other CI runs
+# which will be testing alternate versions of zig, and ultimately would just
+# fill up space on the hard drive for no reason.
+$Env:ZIG_GLOBAL_CACHE_DIR="$(Get-Location)\zig-global-cache"
+$Env:ZIG_LOCAL_CACHE_DIR="$(Get-Location)\zig-local-cache"
+
 # CMake gives a syntax error when file paths with backward slashes are used.
 # Here, we use forward slashes only to work around this.
 & cmake .. `
diff --git a/ci/x86_64-windows-release.ps1 b/ci/x86_64-windows-release.ps1
index 68d22c9eab..80628a6c3d 100644
--- a/ci/x86_64-windows-release.ps1
+++ b/ci/x86_64-windows-release.ps1
@@ -1,10 +1,20 @@
 $TARGET = "$($Env:ARCH)-windows-gnu"
-$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.12.0-dev.2073+402fe565a"
+$ZIG_LLVM_CLANG_LLD_NAME = "zig+llvm+lld+clang-$TARGET-0.13.0-dev.69+c8b808826"
 $MCPU = "baseline"
-$PREFIX_PATH = "$($Env:USERPROFILE)\$ZIG_LLVM_CLANG_LLD_NAME"
+$ZIG_LLVM_CLANG_LLD_URL = "https://ziglang.org/deps/$ZIG_LLVM_CLANG_LLD_NAME.zip"
+$PREFIX_PATH = "$(Get-Location)\..\$ZIG_LLVM_CLANG_LLD_NAME"
 $ZIG = "$PREFIX_PATH\bin\zig.exe"
 $ZIG_LIB_DIR = "$(Get-Location)\lib"
 
+if (!(Test-Path "..\$ZIG_LLVM_CLANG_LLD_NAME.zip")) {
+    Write-Output "Downloading $ZIG_LLVM_CLANG_LLD_URL"
+    Invoke-WebRequest -Uri "$ZIG_LLVM_CLANG_LLD_URL" -OutFile "..\$ZIG_LLVM_CLANG_LLD_NAME.zip"
+
+    Write-Output "Extracting..."
+    Add-Type -AssemblyName System.IO.Compression.FileSystem ;
+    [System.IO.Compression.ZipFile]::ExtractToDirectory("$PWD\..\$ZIG_LLVM_CLANG_LLD_NAME.zip", "$PWD\..")
+}
+
 function CheckLastExitCode {
     if (!$?) {
         exit 1
@@ -25,6 +35,12 @@ Remove-Item -Path 'build-release' -Recurse -Force -ErrorAction Ignore
 New-Item -Path 'build-release' -ItemType Directory
 Set-Location -Path 'build-release'
 
+# Override the cache directories because they won't actually help other CI runs
+# which will be testing alternate versions of zig, and ultimately would just
+# fill up space on the hard drive for no reason.
+$Env:ZIG_GLOBAL_CACHE_DIR="$(Get-Location)\zig-global-cache"
+$Env:ZIG_LOCAL_CACHE_DIR="$(Get-Location)\zig-local-cache"
+
 # CMake gives a syntax error when file paths with backward slashes are used.
 # Here, we use forward slashes only to work around this.
 & cmake .. `