diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index f15a9fcd59124..3e45ac01331ac 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -121,12 +121,10 @@ jobs:
         with:
           fetch-depth: 2
 
-      # Free up disk space on Linux by removing preinstalled components that
-      # we do not need. We do this to enable some of the less resource
-      # intensive jobs to run on free runners, which however also have
-      # less disk space.
+      # Free up disk space on Linux or macOS by removing preinstalled components that
+      # we do not need.
       - name: free up disk space
-        run: src/ci/scripts/free-disk-space-linux.sh
+        run: src/ci/scripts/free-disk-space.sh
         if: matrix.free_disk
 
       # If we don't need to free up disk space then just report how much space we have
diff --git a/src/ci/github-actions/jobs.yml b/src/ci/github-actions/jobs.yml
index 8ee042c415322..68298870cf739 100644
--- a/src/ci/github-actions/jobs.yml
+++ b/src/ci/github-actions/jobs.yml
@@ -17,6 +17,12 @@ runners:
 
   - &job-macos-15
     os: macos-15 # macOS 15 Arm64
+    free_disk: true
+    <<: *base-job
+
+  - &job-macos-26
+    os: macos-26 # macOS 26 Arm64
+    free_disk: true # See https://github.com/rust-lang/infra-team/issues/307
     <<: *base-job
 
   - &job-windows
@@ -561,15 +567,41 @@ auto:
       CODEGEN_BACKENDS: llvm,cranelift
     <<: *job-macos-15
 
-#  - name: test-aarch64-apple-1
+  - name: test-aarch64-apple-1
+    env:
+      # NOTE: keep in sync with `src/ci/docker/scripts/stage_2_test_set1.sh`
+      SCRIPT: >-
+        ./x.py --stage 2 test
+        --host=aarch64-apple-darwin
+        --target=aarch64-apple-darwin
+        --skip compiler
+        --skip src
+      RUST_CONFIGURE_ARGS: >-
+        --enable-sanitizers
+        --enable-profiler
+        --set build.allocator=jemalloc
+      DEVELOPER_DIR: /Applications/Xcode_26.2.app/Contents/Developer
+      # Aarch64 tooling only needs to support macOS 11.0 and up as nothing else
+      # supports the hardware, so only need to test it there.
+      MACOSX_DEPLOYMENT_TARGET: 11.0
+      MACOSX_STD_DEPLOYMENT_TARGET: 11.0
+    <<: *job-macos-15
+
+#  - name: test-aarch64-apple-2
 #    env:
-#      # NOTE: keep in sync with `src/ci/docker/scripts/stage_2_test_set1.sh`
+#      # NOTE: keep in sync with `src/ci/docker/scripts/stage_2_test_set2.sh`,
+#      # union `src/tools/cargo` specifically.
 #      SCRIPT: >-
 #        ./x.py --stage 2 test
 #        --host=aarch64-apple-darwin
 #        --target=aarch64-apple-darwin
-#        --skip compiler
-#        --skip src
+#        --skip tests
+#        --skip library
+#        --skip tidyselftest
+#        && ./x.py --stage 2 test
+#        --host=aarch64-apple-darwin
+#        --target=aarch64-apple-darwin
+#        src/tools/cargo
 #      RUST_CONFIGURE_ARGS: >-
 #        --enable-sanitizers
 #        --enable-profiler
@@ -580,8 +612,36 @@ auto:
 #      MACOSX_DEPLOYMENT_TARGET: 11.0
 #      MACOSX_STD_DEPLOYMENT_TARGET: 11.0
 #    <<: *job-macos-15
-#
-#  - name: test-aarch64-apple-2
+
+  # EXPERIMENT(#157687): we will try to run `aarch64-apple`-equivalent workload
+  # on `macos-26` runner images in parallel to evaluate the running times, since
+  # previous attempts have timed out multiple times. Remove/revert this job if
+  # this hangs or times out, or if it becomes the slowest Merge CI job, and let
+  # T-infra know.
+  # See also #165148
+  - name: test-aarch64-apple-macos-26-1
+    doc_url: https://github.com/rust-lang/rust/issues/157687
+    env:
+      # NOTE: keep in sync with `src/ci/docker/scripts/stage_2_test_set1.sh`
+      SCRIPT: >-
+        ./x.py --stage 2 test
+        --host=aarch64-apple-darwin
+        --target=aarch64-apple-darwin
+        --skip compiler
+        --skip src
+      RUST_CONFIGURE_ARGS: >-
+        --enable-sanitizers
+        --enable-profiler
+        --set build.allocator=jemalloc
+      DEVELOPER_DIR: /Applications/Xcode_26.2.app/Contents/Developer
+      # Aarch64 tooling only needs to support macOS 11.0 and up as nothing else
+      # supports the hardware, so only need to test it there.
+      MACOSX_DEPLOYMENT_TARGET: 11.0
+      MACOSX_STD_DEPLOYMENT_TARGET: 11.0
+    <<: *job-macos-26
+
+#  - name: test-aarch64-apple-macos-26-2
+#    doc_url: https://github.com/rust-lang/rust/issues/157687
 #    env:
 #      # NOTE: keep in sync with `src/ci/docker/scripts/stage_2_test_set2.sh`,
 #      # union `src/tools/cargo` specifically.
@@ -605,7 +665,7 @@ auto:
 #      # supports the hardware, so only need to test it there.
 #      MACOSX_DEPLOYMENT_TARGET: 11.0
 #      MACOSX_STD_DEPLOYMENT_TARGET: 11.0
-#    <<: *job-macos-15
+#    <<: *job-macos-26
 
   ######################
   #  Windows Builders  #
diff --git a/src/ci/scripts/free-disk-space-mac.sh b/src/ci/scripts/free-disk-space-mac.sh
new file mode 100755
index 0000000000000..b67222ef9210c
--- /dev/null
+++ b/src/ci/scripts/free-disk-space-mac.sh
@@ -0,0 +1,43 @@
+#!/bin/bash
+set -euo pipefail
+# ignore-tidy-file-linelength
+
+# Free disk space on macOS GitHub action runners
+# Achieved by removing all iOS simulator instance files and runtime images
+# See https://developer.apple.com/documentation/xcode/xcode-command-line-tool-reference#Manage-the-Simulator
+
+echo "Before clean-up:"
+df -h
+
+echo "deleting iOS simulator instance files and runtime images"
+
+space_before=$(df -k "$GITHUB_WORKSPACE" | awk 'NR == 2 {print $4}')
+
+xcrun simctl shutdown all
+xcrun simctl delete all
+
+# This subcommand runs asynchronously
+xcrun simctl runtime delete all
+
+# Wait a max of 60 seconds to ensure the clean-up is done before any subsequential build steps
+for ((attempt = 0; attempt < 30; attempt++)); do
+    remaining=$(xcrun simctl runtime list -j | jq -e 'length')
+    echo "Remaining simulator runtime images: $remaining"
+
+    if [[ "$remaining" == 0 ]]; then
+        break
+    fi
+    sleep 2
+done
+
+if [[ "$remaining" != 0 ]]; then
+    echo "::warning::Simulator runtime deletion did not finish within the polling period."
+fi
+
+# Report net increase in available disk space
+space_after=$(df -k "$GITHUB_WORKSPACE" | awk 'NR == 2 {print $4}')
+extra_space=$(awk -v b="$space_before" -v a="$space_after" 'BEGIN { printf "%.2f", (a - b) / 1048576 }')
+echo "Increase in available disk space: $extra_space GiB"
+
+echo "After clean-up:"
+df -h
diff --git a/src/ci/scripts/free-disk-space.sh b/src/ci/scripts/free-disk-space.sh
new file mode 100755
index 0000000000000..76e0140806e93
--- /dev/null
+++ b/src/ci/scripts/free-disk-space.sh
@@ -0,0 +1,18 @@
+#!/bin/bash
+set -euo pipefail
+
+script_dir=$(cd -- "$(dirname -- "$0")" && pwd)
+
+# dispatch according to the Github Runner
+case "${RUNNER_OS:-}" in
+    Linux)
+        exec "${script_dir}/free-disk-space-linux.sh"
+        ;;
+    macOS)
+        exec "${script_dir}/free-disk-space-mac.sh"
+        ;;
+    *)
+        echo "::error:: freeing disk space not supported for: '${RUNNER_OS:-unset}'"
+        exit 1
+        ;;
+esac