diff --git a/ci/matrix.yaml b/ci/matrix.yaml
index d9b9ffbadd..e9c8879088 100644
--- a/ci/matrix.yaml
+++ b/ci/matrix.yaml
@@ -28,9 +28,8 @@ llvm14: &llvm14 { name: 'llvm', version: '14', exe: 'clang++' }
 llvm15: &llvm15 { name: 'llvm', version: '15', exe: 'clang++' }
 llvm16: &llvm16 { name: 'llvm', version: '16', exe: 'clang++' }
 llvm17: &llvm17 { name: 'llvm', version: '17', exe: 'clang++' }
-llvm18: &llvm18 { name: 'llvm', version: '18', exe: 'clang++' }
 llvm-oldest: &llvm-oldest { name: 'llvm', version: '9', exe: 'clang++' }
-llvm-newest: &llvm-newest { name: 'llvm', version: '18', exe: 'clang++' }
+llvm-newest: &llvm-newest { name: 'llvm', version: '17', exe: 'clang++' }
 
 # MSVC configs
 msvc2017: &msvc2017 { name: 'cl', version: '14.16', exe: 'cl++' }
@@ -58,7 +57,7 @@ workflows:
     - {jobs: ['build'], std: 'all', ctk: *ctk_11_1, cxx: [*gcc6, *gcc7, *gcc8, *gcc9, *llvm9, *msvc2017]}
     - {jobs: ['build'], std: 'all', ctk: *ctk_11_8, cxx: [*gcc11], sm: '60;70;80;90'}
     - {jobs: ['build'], std: 'all', cxx: [*gcc7, *gcc8, *gcc9, *gcc10, *gcc11, *gcc12]}
-    - {jobs: ['build'], std: 'all', cxx: [*llvm9, *llvm10, *llvm11, *llvm12, *llvm13, *llvm14, *llvm15, *llvm16, *llvm17, *llvm18]}
+    - {jobs: ['build'], std: 'all', cxx: [*llvm9, *llvm10, *llvm11, *llvm12, *llvm13, *llvm14, *llvm15, *llvm16, *llvm17]}
     - {jobs: ['test'],  std: 'all', cxx: [*gcc-newest, *llvm-newest]}
     - {jobs: ['build'], std: 'all', cxx: [*gcc-newest, *llvm-newest], cpu: 'arm64'}
     - {jobs: ['build'], std: 'all', cxx: [*gcc-newest], sm: '90a'}
@@ -215,7 +214,6 @@ default_os_lookup:
   'ctk12.4-llvm15': 'ubuntu22.04'
   'ctk12.4-llvm16': 'ubuntu22.04'
   'ctk12.4-llvm17': 'ubuntu22.04'
-  'ctk12.4-llvm18': 'ubuntu22.04'
   'ctk12.4-cl14.29': 'windows2022'
   'ctk12.4-cl14.36': 'windows2022'
   'ctk12.4-cl14.39': 'windows2022'
@@ -241,7 +239,6 @@ lookup_cxx_supported_stds:
   'llvm15':         [11, 14, 17, 20]
   'llvm16':         [11, 14, 17, 20]
   'llvm17':         [11, 14, 17, 20]
-  'llvm18':         [11, 14, 17, 20]
   'cl14.16':        [    14        ]
   'cl14.29':        [    14, 17    ]
   'cl14.36':        [    14, 17, 20]