diff --git a/action.yml b/action.yml
index 7a8c79e..6a6bd9f 100644
--- a/action.yml
+++ b/action.yml
@@ -42,28 +42,15 @@ runs:
       shell: bash
       working-directory: ${{ inputs.rails-root }}
       run: |
-        AUDIT_OUTPUT=$(bin/importmap audit 2>&1 || true)
-        OUTDATED_OUTPUT=$(bin/importmap outdated 2>&1 || true)
-
-        echo "## Importmap Update" >> $GITHUB_STEP_SUMMARY
-        echo "" >> $GITHUB_STEP_SUMMARY
-        echo "### Vulnerabilities" >> $GITHUB_STEP_SUMMARY
-
-        echo "$AUDIT_OUTPUT" >> $GITHUB_STEP_SUMMARY
-
-        echo "" >> $GITHUB_STEP_SUMMARY
-        echo "### Outdated packages" >> $GITHUB_STEP_SUMMARY
-        echo "$OUTDATED_OUTPUT" >> $GITHUB_STEP_SUMMARY
-
         {
           echo 'importmap-audit<<IMPORTMAP_AUDIT_OUTPUT'
-          echo "$AUDIT_OUTPUT"
+          bin/importmap audit 2>&1 || true
           echo 'IMPORTMAP_AUDIT_OUTPUT'
         } >> "$GITHUB_OUTPUT"
 
         {
           echo 'importmap-outdated<<IMPORTMAP_OUTDATED_OUTPUT'
-          echo "$OUTDATED_OUTPUT"
+          bin/importmap outdated 2>&1 || true
           echo 'IMPORTMAP_OUTDATED_OUTPUT'
         } >> "$GITHUB_OUTPUT"
 
diff --git a/exe/importmap-update b/exe/importmap-update
index a94213a..5beadea 100755
--- a/exe/importmap-update
+++ b/exe/importmap-update
@@ -105,6 +105,37 @@ report.outcomes.each do |o|
 end
 report.warnings.each { |w| warn "  ! #{w}" }
 
+if (summary_path = ENV["GITHUB_STEP_SUMMARY"])
+  File.open(summary_path, "a") do |f|
+    f.puts "### Update summary"
+    f.puts "Dry run: #{options[:dry_run]}"
+
+    if plan.warnings.any?
+      f.puts "#### Plan warnings"
+      plan.warnings.each { |w| f.puts "- #{w}" }
+    end
+
+    f.puts ""
+    f.puts "Reconciler ignored #{reconciled.ignored.size} foreign PR(s)."
+    f.puts ""
+
+    if report.outcomes.any?
+      f.puts "#### Outcomes"
+      f.puts "| Branch | PR | Action | Status | Detail |"
+      f.puts "| --- | --- | --- | --- | --- |"
+      report.outcomes.each do |o|
+        f.puts "| #{o.branch || "?"} | #{"##{o.pr_number}" if o.pr_number} | #{o.type} | #{o.status} | #{o.detail} |"
+      end
+    end
+
+    report.warnings.each { |w|
+      f.puts ""
+      f.puts "> [!WARNING]"
+      f.puts "> #{w}"
+    }
+  end
+end
+
 # Exit non-zero only if any non-skipped outcome failed; in dry run all are
 # skipped, which is a successful run.
 exit(report.outcomes.any?(&:failed?) ? 1 : 0)