diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 39b7cef..a453f37 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -12,19 +12,19 @@ permissions:
 
 jobs:
   install:
-    name: Rust ${{matrix.rust}} on ${{matrix.os == 'ubuntu' && 'Linux' || matrix.os == 'macos' && 'macOS' || matrix.os == 'windows' && 'Windows' || '???'}}
-    runs-on: ${{matrix.os}}-latest
+    name: Rust ${{matrix.rust}} on ${{matrix.os}}
+    runs-on: ${{matrix.os}}
     strategy:
       fail-fast: false
       matrix:
-        os: [ubuntu, macos, windows]
+        os: [ubuntu-latest, macos-latest, windows-latest, windows-11-arm, ubuntu-22.04-arm]
         rust: [nightly, beta, stable, 1.62.0, stable 18 months ago, stable minus 8 releases]
         include:
-          - os: ubuntu
+          - os: ubuntu-latest
             rust: 1.0.0
     timeout-minutes: 45
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: ./
         name: Run dtolnay/rust-toolchain${{contains(matrix.rust, ' ') && ' for ' || '@'}}${{matrix.rust}}
         id: toolchain
diff --git a/README.md b/README.md
index 2ea5437..fc44f15 100644
--- a/README.md
+++ b/README.md
@@ -16,15 +16,15 @@ jobs:
     name: cargo test
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
       - uses: dtolnay/rust-toolchain@stable
       - run: cargo test --all-features
 ```
 
 The selection of Rust toolchain is made based on the particular @rev of this
 Action being requested. For example "dtolnay/rust-toolchain@nightly" pulls in
-the nightly Rust toolchain, while "dtolnay/rust-toolchain@1.42.0" pulls in
-1.42.0.
+the nightly Rust toolchain, while "dtolnay/rust-toolchain@1.89.0" pulls in
+1.89.0.
 
 <br>
 
@@ -40,7 +40,7 @@ All inputs are optional.
 <tr>
   <td><code>toolchain</code></td>
   <td>
-    Rustup toolchain specifier e.g. <code>stable</code>, <code>nightly</code>, <code>1.42.0</code>, <code>nightly-2022-01-01</code>.
+    Rustup toolchain specifier e.g. <code>stable</code>, <code>nightly</code>, <code>1.89.0</code>, <code>nightly-2025-01-01</code>.
     <b>Important: the default is to match the @rev as described above.</b>
     When passing an explicit <code>toolchain</code> as an input instead of @rev, you'll want to use "dtolnay/rust-toolchain@master" as the revision of the action.
   </td>
@@ -66,7 +66,7 @@ All inputs are optional.
 </tr>
 <tr>
   <td><code>cachekey</code></td>
-  <td>A short hash of the installed rustc version, appropriate for use as a cache key. <code>"20220627a831"</code></td>
+  <td>A short hash of the installed rustc version, appropriate for use as a cache key. <code>"20250627a831"</code></td>
 </tr>
 <tr>
   <td><code>name</code></td>
@@ -99,6 +99,18 @@ compiler support.
 
 <br>
 
+## Choice of full-length commit SHA
+
+In a workflow that [pins the action][pin] using a full-length commit SHA (as
+opposed to something like @nightly or @1.89.0) it is required that you pick a
+SHA that is within the history of the master branch. Any commit that is not
+within the history of master will eventually get garbage-collected and your
+workflows will fail.
+
+[pin]: https://docs.github.com/en/actions/reference/security/secure-use#using-third-party-actions
+
+<br>
+
 ## License
 
 The scripts and documentation in this project are released under the [MIT
diff --git a/action.yml b/action.yml
index 3e127bb..bea2792 100644
--- a/action.yml
+++ b/action.yml
@@ -30,7 +30,11 @@ runs:
     - id: parse
       run: |
         : parse toolchain version
-        if [[ $toolchain =~ ^stable' '[0-9]+' '(year|month|week|day)s?' 'ago$ ]]; then
+        if [[ -z $toolchain ]]; then
+          # GitHub does not enforce `required: true` inputs itself. https://github.com/actions/runner/issues/1070
+          echo "'toolchain' is a required input" >&2
+          exit 1
+        elif [[ $toolchain =~ ^stable' '[0-9]+' '(year|month|week|day)s?' 'ago$ ]]; then
           if [[ ${{runner.os}} == macOS ]]; then
             echo "toolchain=1.$((($(date -v-$(sed 's/stable \([0-9]*\) \(.\).*/\1\2/' <<< $toolchain) +%s)/60/60/24-16569)/7/6))" >> $GITHUB_OUTPUT
           else
@@ -38,11 +42,13 @@ runs:
           fi
         elif [[ $toolchain =~ ^stable' 'minus' '[0-9]+' 'releases?$ ]]; then
           echo "toolchain=1.$((($(date +%s)/60/60/24-16569)/7/6-${toolchain//[^0-9]/}))" >> $GITHUB_OUTPUT
+        elif [[ $toolchain =~ ^1\.[0-9]+$ ]]; then
+          echo "toolchain=1.$((i=${toolchain#1.}, c=($(date +%s)/60/60/24-16569)/7/6, i+9*i*(10*i<=c)+90*i*(100*i<=c)))" >> $GITHUB_OUTPUT
         else
           echo "toolchain=$toolchain" >> $GITHUB_OUTPUT
         fi
       env:
-        toolchain: 1.90.0
+        toolchain: 1.91.0
       shell: bash
 
     - id: flags
@@ -58,24 +64,35 @@ runs:
 
     - run: |
         : set $CARGO_HOME
-        echo CARGO_HOME=${CARGO_HOME:-${{runner.os == 'Windows' && '$USERPROFILE' || '$HOME'}}/.cargo} >> $GITHUB_ENV
+        echo CARGO_HOME=${CARGO_HOME:-"${{runner.os == 'Windows' && '$USERPROFILE\.cargo' || '$HOME/.cargo'}}"} >> $GITHUB_ENV
       shell: bash
 
     - run: |
         : install rustup if needed
         if ! command -v rustup &>/dev/null; then
-          curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail "https://sh.rustup.rs" | sh -s -- --default-toolchain none -y
+          curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail https://sh.rustup.rs | sh -s -- --default-toolchain none -y
           echo "$CARGO_HOME/bin" >> $GITHUB_PATH
         fi
       if: runner.os != 'Windows'
       shell: bash
 
+    - run: |
+        : install rustup if needed on windows
+        if ! command -v rustup &>/dev/null; then
+          curl --proto '=https' --tlsv1.2 --retry 10 --retry-connrefused --location --silent --show-error --fail https://win.rustup.rs/${{runner.arch == 'ARM64' && 'aarch64' || 'x86_64'}} --output '${{runner.temp}}\rustup-init.exe'
+          '${{runner.temp}}\rustup-init.exe' --default-toolchain none --no-modify-path -y
+          echo "$CARGO_HOME\bin" >> $GITHUB_PATH
+        fi
+      if: runner.os == 'Windows'
+      shell: bash
+
     - name: rustup toolchain install ${{steps.parse.outputs.toolchain}}
       run: rustup toolchain install ${{steps.parse.outputs.toolchain}}${{steps.flags.outputs.targets}}${{steps.flags.outputs.components}} --profile minimal${{steps.flags.outputs.downgrade}} --no-self-update
       shell: bash
 
     - run: rustup default ${{steps.parse.outputs.toolchain}}
       shell: bash
+      continue-on-error: true  # https://github.com/dtolnay/rust-toolchain/issues/127
 
     - id: rustc-version
       run: |
diff --git a/scripts/update-revs.sh b/scripts/update-revs.sh
index c5c7841..1d5006e 100755
--- a/scripts/update-revs.sh
+++ b/scripts/update-revs.sh
@@ -10,11 +10,12 @@ fi
 patch_releases=(
     1.12.1 1.15.1 1.22.1 1.24.1 1.26.1 1.26.2 1.27.1 1.27.2 1.29.1 1.29.2 1.30.1
     1.31.1 1.34.1 1.34.2 1.41.1 1.43.1 1.44.1 1.45.1 1.45.2 1.52.1 1.56.1 1.58.1
-    1.62.1 1.66.1 1.67.1 1.68.1 1.68.2 1.71.1 1.72.1 1.74.1 1.77.1 1.77.2
+    1.62.1 1.66.1 1.67.1 1.68.1 1.68.2 1.71.1 1.72.1 1.74.1 1.77.1 1.77.2 1.80.1
+    1.84.1 1.85.1
 )
 
 releases() {
-    printf "%s\n" 1.{0..90}.0 ${patch_releases[@]} | sort -V
+    printf "%s\n" 1.{0..100}.0 ${patch_releases[@]} | sort -V
 }
 
 base=$(git rev-parse HEAD)
@@ -32,7 +33,7 @@ for rev in `releases` stable beta nightly; do
     if [[ $rev == 1* ]]; then
         sed -i "/^  toolchain:/,+2d; s/\${{inputs\.toolchain}}/$rev/" action.yml
     else
-        sed -i "s/required: true/required: false\n    default: $rev/" action.yml
+        sed -i "s/^    required: true$/    required: false\n    default: $rev/" action.yml
     fi
     git add action.yml
     git commit --quiet --message "toolchain: $rev"