diff --git a/.github/workflows/weekly-randomized-model.yml b/.github/workflows/weekly-randomized-model.yml
index 0f123ae..fff4588 100644
--- a/.github/workflows/weekly-randomized-model.yml
+++ b/.github/workflows/weekly-randomized-model.yml
@@ -503,13 +503,14 @@ jobs:
   qemu-chaos-matrix:
     name: QEMU chaos (${{ matrix.suite }}, ${{ matrix.arch }})
     needs: qemu-image-build
-    runs-on: ubuntu-24.04
+    runs-on: ${{ matrix.runner }}
     timeout-minutes: ${{ matrix.job_timeout }}
     strategy:
       fail-fast: false
       matrix:
         include:
           - arch: x86_64
+            runner: ubuntu-24.04
             suite: rootfs-stress
             script: scripts/qemu/rootfs_stress.sh
             qemu_timeout: "4800"
@@ -518,6 +519,7 @@ jobs:
             chaos_workers: ""
             job_timeout: 95
           - arch: arm64
+            runner: ubuntu-24.04-arm
             suite: rootfs-stress
             script: scripts/qemu/rootfs_stress.sh
             qemu_timeout: "5400"
@@ -526,6 +528,7 @@ jobs:
             chaos_workers: ""
             job_timeout: 110
           - arch: x86_64
+            runner: ubuntu-24.04
             suite: block-lifecycle-stress
             script: scripts/qemu/block_lifecycle_stress.sh
             qemu_timeout: "2400"
@@ -534,6 +537,7 @@ jobs:
             chaos_workers: ""
             job_timeout: 55
           - arch: arm64
+            runner: ubuntu-24.04-arm
             suite: block-lifecycle-stress
             script: scripts/qemu/block_lifecycle_stress.sh
             qemu_timeout: "3000"
@@ -542,6 +546,7 @@ jobs:
             chaos_workers: ""
             job_timeout: 65
           - arch: x86_64
+            runner: ubuntu-24.04
             suite: crash-recovery
             script: scripts/qemu/crash_recovery.sh
             qemu_timeout: "2400"
@@ -550,6 +555,7 @@ jobs:
             chaos_workers: ""
             job_timeout: 60
           - arch: arm64
+            runner: ubuntu-24.04-arm
             suite: crash-recovery
             script: scripts/qemu/crash_recovery.sh
             qemu_timeout: "3000"
@@ -557,22 +563,26 @@ jobs:
             chaos_files: ""
             chaos_workers: ""
             job_timeout: 75
+          # mixed_chaos.sh runs two sequential QEMU phases. The job timeout must
+          # cover both per-phase timeouts plus runner setup and artifact upload.
           - arch: x86_64
+            runner: ubuntu-24.04
             suite: mixed-chaos
             script: scripts/qemu/mixed_chaos.sh
             qemu_timeout: "4800"
             stress_workers: ""
             chaos_files: "320"
             chaos_workers: "10"
-            job_timeout: 100
+            job_timeout: 180
           - arch: arm64
+            runner: ubuntu-24.04-arm
             suite: mixed-chaos
             script: scripts/qemu/mixed_chaos.sh
             qemu_timeout: "5400"
             stress_workers: ""
             chaos_files: "280"
             chaos_workers: "8"
-            job_timeout: 115
+            job_timeout: 210
     steps:
       - name: Checkout ArgosFS
         uses: actions/checkout@v7