diff --git a/.github/workflows/integration.yml b/.github/workflows/integration.yml
index b409c9b..946d0d3 100644
--- a/.github/workflows/integration.yml
+++ b/.github/workflows/integration.yml
@@ -20,7 +20,7 @@ jobs:
       - name: Create test Rails app
         run: |
           gem install rails --no-document
-          rails new /tmp/test-app \
+          rails new $RUNNER_TEMP/test-app \
             --skip-git \
             --skip-action-mailer \
             --skip-action-mailbox \
@@ -31,7 +31,7 @@ jobs:
             --skip-bootsnap \
             --skip-test \
             --quiet
-          cd /tmp/test-app
+          cd $RUNNER_TEMP/test-app
           git init
           git add .
           git config user.email "test@example.com"
@@ -40,7 +40,7 @@ jobs:
 
       - name: Pin outdated packages
         run: |
-          cd /tmp/test-app
+          cd $RUNNER_TEMP/test-app
 
           cat >> config/importmap.rb << 'EOF'
 
@@ -58,17 +58,17 @@ jobs:
       - name: Run in dry-run mode
         uses: ./
         env:
-          IMPORTMAP_RUN_LOG: /tmp/dry-run-output.txt
+          IMPORTMAP_RUN_LOG: ${{ runner.temp }}/dry-run-output.txt
         with:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           dry-run: "true"
-          rails-root: /tmp/test-app
+          rails-root: ${{ runner.temp }}/test-app
 
       - name: Assert all outdated packages appear in dry-run output
         run: |
           failed=0
           for pkg in hotkeys-js is-svg just-extend local-time md5 tom-select; do
-            if grep -q "$pkg" /tmp/dry-run-output.txt; then
+            if grep -q "$pkg" $RUNNER_TEMP/dry-run-output.txt; then
               echo "✓ $pkg"
             else
               echo "✗ $pkg not found in output"
diff --git a/action.yml b/action.yml
index 833a65a..8546301 100644
--- a/action.yml
+++ b/action.yml
@@ -21,9 +21,6 @@ inputs:
     description: "When 'true', run end-to-end but skip all side effects (no commits, pushes, or PR operations)."
     required: false
     default: "false"
-  ruby-version:
-    description: "Ruby version to set up. Defaults to the consuming repo's .ruby-version."
-    required: false
   author-name:
     description: "Git author name for commits."
     required: false
@@ -44,8 +41,8 @@ runs:
       shell: bash
       working-directory: ${{ inputs.rails-root }}
       run: |
-        bin/importmap audit 2>&1 | tee /tmp/importmap-audit.txt || true
-        bin/importmap outdated 2>&1 | tee /tmp/importmap-outdated.txt || true
+        bin/importmap audit 2>&1 | tee "${{ runner.temp }}/importmap-audit.txt" || true
+        bin/importmap outdated 2>&1 | tee "${{ runner.temp }}/importmap-outdated.txt" || true
 
     - name: Run importmap-update
       shell: bash
@@ -60,9 +57,8 @@ runs:
         IMPORTMAP_DRY_RUN:        ${{ inputs.dry-run }}
         IMPORTMAP_AUTHOR_NAME:    ${{ inputs.author-name }}
         IMPORTMAP_AUTHOR_EMAIL:   ${{ inputs.author-email }}
+        IMPORTMAP_OUTDATED_FILE:  ${{ runner.temp }}/importmap-outdated.txt
+        IMPORTMAP_AUDIT_FILE:     ${{ runner.temp }}/importmap-audit.txt
       run: |
         bundle install
-        bundle exec exe/importmap-update \
-          --outdated-file /tmp/importmap-outdated.txt \
-          --audit-file /tmp/importmap-audit.txt \
-          2>&1 | tee "${IMPORTMAP_RUN_LOG:-/dev/null}"
+        bundle exec exe/importmap-update 2>&1 | tee "${IMPORTMAP_RUN_LOG:-/dev/null}"
diff --git a/exe/importmap-update b/exe/importmap-update
index 3ee7d97..650bdae 100755
--- a/exe/importmap-update
+++ b/exe/importmap-update
@@ -31,16 +31,12 @@ require "parsers/audit_parser"
 
 options = {
   config_path: ENV.fetch("INPUT_CONFIG_FILE", ".github/importmap-updates.yml"),
-  outdated_file: nil,
-  audit_file: nil,
   dry_run: %w[true 1 yes].include?(ENV["IMPORTMAP_DRY_RUN"].to_s.downcase)
 }
 
 OptionParser.new do |opts|
   opts.banner = "Usage: importmap-update [options]"
   opts.on("-c", "--config PATH", "Path to config YAML") { |p| options[:config_path] = p }
-  opts.on("--outdated-file PATH", "Captured `bin/importmap outdated` output") { |p| options[:outdated_file] = p }
-  opts.on("--audit-file PATH", "Captured `bin/importmap audit` output") { |p| options[:audit_file] = p }
   opts.on("--dry-run", "Do not perform side effects; log what would happen") { options[:dry_run] = true }
   opts.on("-h", "--help") {
     puts opts
@@ -55,11 +51,8 @@ rescue Importmap::Update::Config::ConfigError => e
   exit 2
 end
 
-missing = [:outdated_file, :audit_file].select { |k| options[k].nil? }
-unless missing.empty?
-  warn "Missing required option(s): #{missing.map { |k| "--#{k.to_s.tr("_", "-")}" }.join(", ")}"
-  exit 2
-end
+outdated_file = ENV.fetch("IMPORTMAP_OUTDATED_FILE")
+audit_file = ENV.fetch("IMPORTMAP_AUDIT_FILE")
 
 repo = ENV["GITHUB_REPOSITORY"]
 if repo.nil? || repo.empty?
@@ -82,8 +75,8 @@ git = Importmap::Update::GitClient.new(
   author_email: ENV.fetch("IMPORTMAP_AUTHOR_EMAIL", "github-actions[bot]@users.noreply.github.com")
 )
 
-outdated_output = File.read(options[:outdated_file])
-audit_output = File.read(options[:audit_file])
+outdated_output = File.read(outdated_file)
+audit_output = File.read(audit_file)
 outdated = Importmap::Update::Parsers::OutdatedParser.parse(outdated_output)
 vulnerabilities = Importmap::Update::Parsers::AuditParser.parse(audit_output)
 plan = Importmap::Update::Planner.new(